阅读说明：本技术 交流-直流转换电路 (AC-DC conversion circuit ) 是由 陈威 赵晨 于 2020-12-16 设计创作，主要内容包括：依据本发明的实施例揭露了一种交流-直流转换电路,本发明所述的交流-直流转换电路,利用N个输入端串联的第一类型的功率变换器替换现有技术中采用高耐压功率开关的boost电路以进行功率因数校正,避免在交流-直流转换电路中使用高耐压的功率开关,使得交流-直流转换电路的体积较小,开关损耗更小,能量损耗较少,且散热更好,整个电路的功率密度较大。(According to the ac-dc conversion circuit disclosed by the embodiment of the invention, the boost circuit adopting a high-voltage-withstanding power switch in the prior art is replaced by the first type of power converter with N input ends connected in series to perform power factor correction, so that the use of the high-voltage-withstanding power switch in the ac-dc conversion circuit is avoided, the ac-dc conversion circuit is smaller in size, smaller in switching loss, less in energy loss, better in heat dissipation and higher in power density of the whole circuit.)

1. An ac-dc conversion circuit, comprising:

the rectifying circuit is used for receiving input alternating-current voltage and converting the input alternating-current voltage into input direct-current voltage for output;

the input end of the first DC-DC conversion module is coupled with the output end of the rectifying circuit, the output end of the first DC-DC conversion module is coupled with the input end of the second DC-DC conversion module, and the working state of each power switch in the first DC-DC conversion module is controlled so that the waveform of the input current of the first DC-DC conversion module follows the input direct-current voltage to realize power factor correction; the first DC-DC conversion module is configured as a first type power converter with N input ends connected in series, the input ends of the N first type power converters are sequentially connected in series to receive the input direct-current voltage, so that the voltage borne by each power switch in the first DC-DC conversion circuit is reduced, and N is greater than or equal to 1;

and the input end of the second DC-DC conversion module is coupled to the output end of the first DC-DC conversion module, and the output end of the second DC-DC conversion module is coupled to a load so as to convert the output signal of the first DC-DC conversion module into a first output signal to drive the load.

2. The ac-dc conversion circuit according to claim 1, wherein: the input ends of the N first-type power converters are sequentially connected in series between an input high potential end of a first DC-DC conversion module and a ground potential, and the first DC-DC conversion module is provided with N output ends which are the output ends of the N first-type power converters respectively.

3. The ac-dc conversion circuit according to claim 1, wherein: the first type of power converter is a non-isolated DC-DC converter.

4. The ac-dc conversion circuit according to claim 1, wherein: and controlling at least one power switch in each of the N first type power converters to be conducted so as to reduce the voltage borne by each power switch.

5. The ac-dc conversion circuit according to claim 1, wherein: the alternating current-direct current conversion circuit further comprises N first control circuits, wherein the N first control circuits are used for respectively controlling the N first type power converters, and the first control circuits are configured to select a control mode of constant frequency or variable frequency to control the working state of the corresponding first type power converter under different working modes.

6. The ac-dc conversion circuit according to claim 1, wherein: the alternating current-direct current conversion circuit further comprises N first control circuits, wherein the N first control circuits are used for respectively controlling the N first type power converters, and the first control circuits are used for generating corresponding first duty ratio signals representing required duty ratios according to output voltage sampling signals, input voltage sampling signals and inductive current sampling signals of the corresponding first type power converters, and generating corresponding control signals according to the corresponding first duty ratio signals to control the on and off of each power switch in the corresponding first type power converters.

7. The ac-dc conversion circuit according to claim 6, wherein: the first control circuit includes:

the voltage compensation module receives the output voltage sampling signal and a corresponding voltage reference signal and outputs a voltage compensation signal;

the current reference signal generating module receives the voltage compensation signal and the input voltage sampling signal and generates a current reference signal;

the current compensation module receives the current reference signal and the inductive current sampling signal and outputs a corresponding first duty ratio signal;

wherein the current reference signal is configured to be positively correlated with a product of the voltage compensation signal and the input voltage sampling signal.

8. The ac-dc conversion circuit according to claim 6 or 7, wherein: each of the first type of power converters includes at least one first power switch and at least one second power switch, and in each of the first type of power converters: all the first power switches are switched on and off at the same time, all the second power switches are switched on and off at the same time, and the first power switches and the second power switches are switched on complementarily.

9. The ac-dc conversion circuit of claim 8, wherein: the first control circuit further comprises a PWM generating module for generating a corresponding control signal according to the corresponding first duty ratio signal so as to control the on and off of each power switch in the corresponding first type of power converter; the PWM generation module includes:

the conduction control circuit is used for controlling the conduction time of the first power switch in the corresponding first type of power converter according to the clock signal;

the turn-off control circuit receives a corresponding first duty ratio signal and is used for controlling the turn-off time of the first power switch in the corresponding first type of power converter according to the first duty ratio signal;

wherein the turn-on control circuit and the turn-off control circuit are further configured to control the second power switch in the corresponding first type of power converter to be turned on complementarily with the first power switch.

10. The ac-dc conversion circuit according to claim 1, wherein: the alternating current-direct current conversion circuit further comprises N first control circuits, wherein the N first control circuits are used for respectively controlling the N first type power converters, and the first control circuits are used for controlling the turn-on and turn-off time of each power switch in the corresponding first type power converter according to the output voltage sampling signal and the inductive current of the corresponding first type power converter.

11. The ac-dc conversion circuit of claim 10, wherein: each of the first type of power converters includes at least one first power switch and at least one second power switch, and in each of the first type of power converters: all the first power switches are switched on and off at the same time, all the second power switches are switched on and off at the same time, and the first power switches and the second power switches are switched on complementarily.

12. The ac-dc conversion circuit according to claim 11, wherein: the first control circuit includes:

the conduction control circuit receives the inductive current and generates a corresponding conduction trigger signal when the inductive current crosses zero so as to control the conduction of the first power switch in the corresponding first type of power converter;

the turn-off control circuit receives the output voltage sampling signal and the corresponding first proportional coefficient to generate a corresponding on-time signal, and controls the turn-off time of the first power switch in the corresponding first type of power converter according to the on-time signal;

wherein the turn-on control circuit and the turn-off control circuit are further configured to control the second power switch in the corresponding first type of power converter to be turned on complementarily with the first power switch.

13. The ac-dc conversion circuit of claim 12, wherein: the shutdown control circuit includes:

the voltage compensation circuit receives the output voltage sampling signal and a corresponding voltage reference signal and outputs a voltage compensation signal;

the on-time generating circuit receives the voltage compensation signal and the corresponding first proportional coefficient and outputs a corresponding on-time signal;

the on-time timer starts to time from the on time of the first power switch in the corresponding first type of power converter, and when the on-time signal is reached, the first power switch in the corresponding first type of power converter is turned off;

wherein the corresponding on-time signal is configured to be positively correlated with a product of the voltage compensation signal and the corresponding first scaling factor.

14. The ac-dc conversion circuit according to claim 1, wherein: the second DC-DC conversion module is configured to be N second type power converters, and input ends of the N second type power converters are respectively coupled to output ends of the N first type power converters correspondingly.

15. The ac-dc conversion circuit of claim 14, wherein: the output ends of the N second type power converters are independent or connected in series or in parallel.

16. The ac-dc conversion circuit of claim 14, wherein: the second type of power converter is an isolated DC-DC converter for electrical isolation.

17. The ac-dc conversion circuit of claim 14, wherein: the second type of power converter includes transformers, all of the N second type of power converters being integrated into one single core N-phase integrated transformer.

18. The ac-dc conversion circuit of claim 14, wherein: when the output ends of the N second type power converters are connected in parallel or in series, the working states of two adjacent second type power converters are controlled in a staggered phase mode, so that output ripples are reduced.

19. The ac-dc conversion circuit of claim 14, wherein: the alternating current-direct current conversion circuit further comprises a second control circuit, and the second control circuit is used for controlling the working states of the N second type power converters so as to control the first output signals output by the second DC-DC conversion module.

Technical Field

The invention relates to the field of power electronics, in particular to an alternating current-direct current conversion circuit.

Background

With the development of society, people use various electric appliances to meet personal needs. Some electrical appliances only work under direct current, so an alternating current-direct current conversion device is needed to convert alternating current into direct current suitable for the operation of some electrical appliances so as to drive the electrical appliances. An ac-dc conversion circuit in the prior art includes a rectifying circuit, a boost circuit, and a flyback circuit, where an input end of the rectifying circuit receives an input ac voltage, an output end of the rectifying circuit is coupled to an input end of the boost circuit, an output end of the boost circuit is coupled to an input end of the flyback circuit, and an output end of the flyback circuit is coupled to a load. The rectifying circuit is used for converting alternating current into direct current, the boost circuit is used for realizing a power factor correction function, and the flyback circuit is used for generating direct current suitable for load work so as to drive the load.

In the prior art, a boost circuit is coupled to an output end of a rectifying circuit, so that a power switch of the boost circuit generally adopts a high-voltage device (such as a 600V withstand voltage class) to adapt to a general input alternating voltage range (90-264Vac), and compared with a low-voltage device (such as a 48V withstand voltage class), the high-voltage device has a larger volume, so that the volume of the alternating current-direct current converting circuit is larger, and the power density of the whole circuit is lower; and the switching loss of the high-voltage device is much larger than that of the low-voltage device under the same switching frequency, thereby causing more energy loss.

Disclosure of Invention

In view of the above, the present invention provides an ac-dc conversion circuit to solve the technical problems of low power density and high energy loss of the whole circuit caused by using a high voltage-withstanding power switch in the prior art.

An embodiment of the present invention provides an ac-dc conversion circuit, including: the rectifying circuit is used for receiving input alternating-current voltage and converting the input alternating-current voltage into input direct-current voltage for output; the input end of the first DC-DC conversion module is coupled with the output end of the rectifying circuit, the output end of the first DC-DC conversion module is coupled with the input end of the second DC-DC conversion module, and the working state of each power switch in the first DC-DC conversion module is controlled so that the waveform of the input current of the first DC-DC conversion module follows the input direct-current voltage to realize power factor correction; the first DC-DC conversion module is configured as a first type power converter with N input ends connected in series, the input ends of the N first type power converters are sequentially connected in series to receive the input direct-current voltage, so that the voltage borne by each power switch in the first DC-DC conversion circuit is reduced, and N is greater than or equal to 1; and the input end of the second DC-DC conversion module is coupled to the output end of the first DC-DC conversion module, and the output end of the second DC-DC conversion module is coupled to a load so as to convert the output signal of the first DC-DC conversion module into a first output signal to drive the load.

Preferably, the input terminals of the N first type power converters are sequentially connected in series between the input high potential terminal of the first DC-DC conversion module and the ground potential, and the first DC-DC conversion module has N output terminals, which are the output terminals of the N first type power converters, respectively.

Preferably, the first type of power converter is a non-isolated DC-DC converter.

Preferably, at least one power switch in each of the N first-type power converters is controlled to conduct, so as to reduce the voltage borne by each power switch.

Preferably, the ac-dc conversion circuit further includes N first control circuits, configured to control the N first type power converters respectively, and the first control circuit is configured to select a control manner of fixed frequency or variable frequency to control an operating state of the corresponding first type power converter in different operating modes.

Preferably, the ac-dc conversion circuit further includes N first control circuits, configured to control the N first type power converters respectively, and the first control circuit is configured to generate a corresponding first duty ratio signal representing a required duty ratio according to an output voltage sampling signal, an input voltage sampling signal, and an inductor current sampling signal of the corresponding first type power converter, and generate a corresponding control signal according to the corresponding first duty ratio signal to control on and off of each power switch in the corresponding first type power converter.

Preferably, the first control circuit includes: the voltage compensation module receives the output voltage sampling signal and a corresponding voltage reference signal and outputs a voltage compensation signal; the current reference signal generating module receives the voltage compensation signal and the input voltage sampling signal and generates a current reference signal; the current compensation module receives the current reference signal and the inductive current sampling signal and outputs a corresponding first duty ratio signal; wherein the current reference signal is configured to be positively correlated with a product of the voltage compensation signal and the input voltage sampling signal.

Preferably, each of the first type of power converters comprises at least one first power switch and at least one second power switch, and in each of the first type of power converters: all the first power switches are switched on and off at the same time, all the second power switches are switched on and off at the same time, and the first power switches and the second power switches are switched on complementarily.

Preferably, the first control circuit further comprises a PWM generation module for generating a corresponding control signal according to the corresponding first duty ratio signal to control on and off of each power switch in the corresponding first type of power converter; the PWM generation module includes: the on-control circuit is used for controlling the conducting time of the first power switch in the corresponding first type of power converter according to the clock signal; the turn-off control circuit receives a corresponding first duty ratio signal and is used for controlling the turn-off time of the first power switch in the corresponding first type of power converter according to the first duty ratio signal; wherein the turn-on control circuit and the turn-off control circuit are further configured to control the second power switch in the corresponding first type of power converter to be turned on complementarily with the first power switch.

Preferably, the ac-dc conversion circuit further includes N first control circuits, configured to control the N first type power converters respectively, and the first control circuit is configured to control the turn-on and turn-off time of each power switch in the corresponding first type power converter according to the output voltage sampling signal and the inductor current of the corresponding first type power converter.

Preferably, each of the first type of power converters comprises at least one first power switch and at least one second power switch, and in each of the first type of power converters: all the first power switches are switched on and off at the same time, all the second power switches are switched on and off at the same time, and the first power switches and the second power switches are switched on complementarily.

Preferably, the first control circuit includes: the conduction control circuit receives the inductive current and generates a corresponding conduction trigger signal when the inductive current crosses zero so as to control the conduction of the first power switch in the corresponding first type of power converter; the turn-off control circuit receives the output voltage sampling signal and the corresponding first proportional coefficient to generate a corresponding on-time signal, and controls the turn-off time of the first power switch in the corresponding first type of power converter according to the on-time signal; wherein the turn-on control circuit and the turn-off control circuit are further configured to control the second power switch in the corresponding first type of power converter to be turned on complementarily with the first power switch.

Preferably, the turn-off control circuit includes: the voltage compensation circuit receives the output voltage sampling signal and a corresponding voltage reference signal and outputs a voltage compensation signal; the on-time generating circuit receives the voltage compensation signal and the corresponding first proportional coefficient and outputs a corresponding on-time signal; the on-time timer starts to time from the on time of the first power switch in the corresponding first type of power converter, and when the on-time signal is reached, the first power switch in the corresponding first type of power converter is turned off; wherein the corresponding on-time signal is configured to be positively correlated with a product of the voltage compensation signal and the corresponding first scaling factor.

Preferably, the second DC-DC conversion module is configured as N second type power converters, and the input terminals of the N second type power converters are respectively coupled to the output terminals of the N first type power converters.

Preferably, the output terminals of the N second type power converters are independent or connected in series or in parallel.

Preferably, the second type of power converter is an isolated DC-DC converter for electrical isolation.

Preferably, the second type of power converter comprises transformers, all transformers of the N second type of power converters being integrated into one single core N-phase integrated transformer.

Preferably, when the output ends of the N second type power converters are connected in parallel or in series, the operating states of two adjacent second type power converters are controlled in a staggered phase manner to reduce output ripple.

Preferably, the ac-DC conversion circuit further includes a second control circuit for controlling the operating states of the N second type power converters to control the first output signal output by the second DC-DC conversion module.

Compared with the prior art, the technical scheme of the invention has the following advantages: the alternating current-direct current conversion circuit comprises a rectification circuit, a voltage detection circuit and a voltage control circuit, wherein the rectification circuit is used for receiving an input alternating current voltage and converting the input alternating current voltage into an input direct current voltage for outputting; the input end of the first DC-DC conversion module is coupled with the output end of the rectifying circuit, the output end of the first DC-DC conversion module is coupled with the input end of the second DC-DC conversion module, and power factor correction is carried out by controlling the working state of the first DC-DC conversion module; the output end of the second DC-DC conversion module is coupled with the load so as to drive the load; the first DC-DC conversion module is configured as a first type power converter with N input ends connected in series, and the plurality of power switches in the first DC-DC conversion module are controlled to be conducted at the same time, so that the withstand voltage of each power switch in the first DC-DC conversion module is reduced. According to the alternating current-direct current conversion circuit, a boost circuit adopting a high-voltage-resistance power switch in the prior art is replaced by the first type of power converter with the N input ends connected in series to correct the power factor, so that the high-voltage-resistance power switch is avoided being used in the alternating current-direct current conversion circuit, the alternating current-direct current conversion circuit is smaller in size, smaller in switching loss, less in energy loss, better in heat dissipation and higher in power density of the whole circuit.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of an AC-DC converter circuit according to the present invention;

FIG. 2 is a first block circuit diagram of a first DC-DC conversion module according to the present invention;

FIG. 3 is a circuit diagram of a first DC-DC conversion module according to a first embodiment of the present invention;

FIG. 4 is a waveform diagram illustrating the operation of a first DC-DC conversion module according to a first embodiment of the present invention;

FIG. 5 is a circuit diagram of a first control circuit according to a first embodiment of the present invention;

FIG. 6 is a schematic circuit diagram of a PWM generating module according to an embodiment of the present invention;

FIG. 7 is a circuit diagram of a second control circuit according to a first embodiment of the present invention;

FIG. 8 is a circuit diagram of a second embodiment of a first DC-DC conversion module according to the present invention;

fig. 9 is a circuit diagram of a third embodiment of a first DC-DC conversion module according to the present invention;

fig. 10 is a circuit diagram of a fourth embodiment of a first DC-DC conversion module according to the present invention;

fig. 11 is a waveform diagram illustrating the operation of a fourth embodiment of the first DC-DC conversion module according to the present invention;

fig. 12 is a circuit diagram of a fifth embodiment of a first DC-DC conversion module according to the present invention;

fig. 13 is a circuit diagram of a sixth embodiment of a first DC-DC conversion module according to the present invention;

fig. 14 is a waveform diagram illustrating operation of a sixth embodiment of a first DC-DC conversion module according to the present invention;

fig. 15 is a circuit diagram of a seventh embodiment of a first DC-DC conversion module according to the present invention;

fig. 16 is a circuit diagram of an eighth embodiment of the first DC-DC conversion module according to the present invention;

fig. 17 is a waveform diagram illustrating an operation of an eighth embodiment of the first DC-DC conversion module according to the present invention;

fig. 18 is a circuit diagram of a ninth embodiment of the first DC-DC conversion module according to the present invention;

fig. 19 is a circuit diagram of a tenth embodiment of a first DC-DC conversion module according to the present invention;

fig. 20 is a diagram showing an operation waveform of a first DC-DC conversion module according to a tenth embodiment of the present invention;

fig. 21 is a circuit diagram illustrating an eleventh embodiment of a first DC-DC conversion module according to the present invention;

fig. 22 is a circuit diagram illustrating a twelfth embodiment of a first DC-DC conversion module according to the present invention;

FIG. 23 is a waveform illustrating operation of a twelfth embodiment of a first DC-DC converter module according to the present invention;

fig. 24 is a schematic circuit diagram of a thirteenth embodiment of the first DC-DC conversion module according to the present invention;

FIG. 25 is a circuit diagram of a fourteenth embodiment of a first DC-DC converter module according to the invention;

FIG. 26 is a waveform diagram illustrating operation of a fourteenth DC-DC converter module according to an embodiment of the present invention;

fig. 27 is a circuit schematic diagram of a fifteenth embodiment of a first DC-DC conversion module of the present invention;

fig. 28 is a circuit diagram illustrating a sixteenth embodiment of the first DC-DC conversion module according to the present invention;

fig. 29 is a waveform diagram illustrating operation of a sixteenth embodiment of the first DC-DC conversion module according to the present invention;

FIG. 30 is a circuit schematic diagram of a seventeenth embodiment of a first DC-DC conversion module according to the invention;

fig. 31 is a circuit diagram illustrating an eighteen embodiment of a first DC-DC conversion module according to the present invention;

fig. 32 is a waveform diagram illustrating the operation of an eighteenth embodiment of the first DC-DC conversion module according to the present invention;

fig. 33 is a circuit diagram illustrating a nineteenth embodiment of a first DC-DC conversion module according to the present invention;

FIG. 34 is a second circuit block diagram of the first DC-DC conversion module of the present invention;

fig. 35 is a circuit schematic diagram of a first DC-DC conversion module twenty according to an embodiment of the invention;

fig. 36 is a first circuit block diagram of a second DC-DC conversion module of the present invention;

FIG. 37 is a circuit schematic of a first embodiment of a second DC-DC conversion module of the present invention;

FIG. 38 is a second circuit block diagram of a second DC-DC conversion module of the present invention;

FIG. 39 is a circuit diagram of a second embodiment of a second DC-DC conversion module according to the present invention;

FIG. 40 is a circuit schematic of a third embodiment of a second DC-DC conversion module according to the present invention;

Detailed Description

The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details. Well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.

Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

Meanwhile, it should be understood that, in the following description, a "circuit" refers to a conductive loop constituted by at least one element or sub-circuit through electrical or electromagnetic connection. When an element or circuit is referred to as being "connected to" another element or element/circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that there are no intervening elements present.

Fig. 1 is a circuit block diagram of an ac-dc conversion circuit according to the present invention, the ac-dc conversion circuit including: the rectifier circuit 1 is used for receiving an input alternating current voltage Vin1, converting the input alternating current voltage Vin1 into an input direct current voltage Vin and outputting the input direct current voltage Vin; the input end of the first DC-DC conversion module 2 is coupled with the output end of the rectification circuit 1, the output end of the first DC-DC conversion module is coupled with the input end of the second DC-DC conversion module 3, and power factor correction is carried out by controlling the working state of the first DC-DC conversion module 2; the output end of the second DC-DC conversion module 3 is coupled to a load to generate a first output signal to drive the load; the first DC-DC conversion module 2 includes a multi-level DC-DC converter or a first type power converter with N input terminals connected in series, and controls a plurality of power switches in the first DC-DC conversion module 2 to be turned on simultaneously, so as to reduce the withstand voltage of each power switch in the first DC-DC conversion module 2, where N is greater than 1.

Further, the first DC-DC conversion module 2 is configured as a first type of power converter with N inputs connected in series. Preferably, the first type of power converter is a non-isolated DC-DC converter.

The rectifier circuit 1 converts an input ac voltage Vin1 input by an input source into an input dc voltage Vin, that is, converts ac into dc, and may be implemented by using an existing rectifier circuit, such as a half-bridge rectifier circuit or a full-bridge rectifier circuit. Preferably, the input dc voltage Vin is the absolute value of the input ac voltage Vin 1.

Further, the first DC-DC conversion module 2 is configured as a multi-level DC-DC converter. Preferably, the multi-level DC-DC converter is a non-isolated multi-level DC-DC converter,

further, when the first DC-DC conversion module 2 is configured as a multi-level DC-DC converter, the output voltage of the first DC-DC conversion module 2 is the output voltage of the multi-level DC-DC converter; when the first DC-DC conversion module 2 is configured as N first type power converters, the output voltage of the first DC-DC conversion module 2 is N output voltages of the N first type power converters.

Further, the second DC-DC conversion module 3 includes an isolation type DC-DC converter for electrical isolation, and optionally, the second DC-DC conversion module 3 is configured to implement an output voltage stabilization function or an output constant current function, which is not limited in the present invention.

Preferably, the second DC-DC conversion module 3 comprises N power converters of the second type, said N being greater than 1. Optionally, when the first DC-DC conversion module 2 is configured as a multi-level DC-DC converter, the input terminals of the N second type power converters are connected in parallel to receive the output voltage of the multi-level DC-DC converter, and the output terminals of the N second type power converters are independent or connected in series or in parallel. Optionally, when the first DC-DC conversion module 2 is configured as N first-type power converters, the input terminals of the N second-type power converters are respectively coupled to the output terminals of the N first-type power converters, and the output terminals of the N second-type power converters are independent or connected in series or in parallel.

Further, the coupling manner of the output ends of the N second type power converters depends on the type of the load to be driven, for example, when the ac-dc conversion circuit of the present invention is used to drive a plurality of loads, the output ends of the N second type power converters are independent, and the output ends of the N second type power converters output a driving voltage to drive the N loads respectively; when the driving voltage required by the load is larger, the output ends of the N second type power converters are connected in series to generate larger driving voltage so as to drive the load; when the driving current required by the load is large, the output terminals of the N second type power converters are connected in parallel to generate a large driving current to drive the load, which is not limited by the present invention.

Further, the second type of power converter is an isolated DC-DC converter for electrical isolation.

According to the alternating current-direct current conversion circuit, in the first DC-DC conversion module, a non-isolation type multi-level DC-DC converter or a non-isolation type DC-DC converter with N input ends connected in series is adopted to replace a traditional non-isolation type DC-DC converter in the prior art so as to realize a Power Factor Correction (PFC) function, and a switching device with a low voltage withstanding grade is simply connected in series or is formed into a module and then connected in series to replace a single switching device with a high voltage withstanding grade in the traditional non-isolation type DC-DC converter, so that the same function is equivalently realized, and therefore power switches in the first DC-DC conversion module are all switching devices with a low voltage withstanding grade. Further, the plurality of power switches in the first DC-DC conversion module are controlled to be simultaneously conducted, so that the withstand voltage of each power switch in the first DC-DC conversion module is reduced, and a switching device with a low withstand voltage level can be used in the first DC-DC conversion module. In the invention, the first DC-DC conversion module does not contain switching devices with high voltage-resistant grade any more and is a switching device with low voltage-resistant grade, so that the AC-DC conversion circuit has smaller volume and larger power density of the whole circuit; the switching loss of a switching device with high voltage-withstanding grade under the same switching frequency can be greatly increased, so that the switching loss of the alternating current-direct current conversion circuit is smaller, and the energy loss is less; in the first DC-DC conversion module, a plurality of low voltage-resistant power switches are used for replacing a high voltage-resistant power switch, so that the alternating current-direct current conversion circuit has better heat dissipation; according to the invention, the switching device with low voltage withstanding grade is used in the first DC-DC conversion module, so that the switching frequency can be effectively improved, and the volume of related passive devices (such as inductors, capacitors and the like) is reduced, thereby further improving the power density of the whole circuit. The alternating current-direct current conversion circuit adopts an AC-DC and DC-DC two-stage architecture, wherein the front-stage AC-DC comprises: the non-isolated DC-DC converter with the equivalent switching state is realized by simply connecting switching devices with low voltage-resistant grade in series or forming a mode of cascade after the modules, and has a power factor correction function, namely the input voltage and the envelope curve of the input current of the first DC-DC conversion module are synchronous by controlling the working state of the first DC-DC conversion module; the rear stage DC-DC includes a DC-DC converter having an electrical isolation function to drive a load, and may be implemented using a plurality of DC-DC converters. The alternating current-direct current conversion circuit realizes the high power density of an AC-DC and DC-DC two-stage framework, is applied to the occasions of ultra-thin/ultra-small adapter power supplies, and can also be applied to other occasions with higher requirements on the power density and the switching loss of the circuit, and the invention does not limit the occasions. In addition, the first DC-DC conversion module can work in three working modes of CCM, DCM and BCM. When the first DC-DC conversion module works in a CCM mode, a subsequent first control mode is utilized for controlling, namely the first DC-DC conversion module works in a fixed frequency mode (the working period is controlled to be unchanged, and the conduction time is adjusted); when the first DC-DC conversion module works in a BCM mode, a subsequent second control mode is utilized for controlling, namely, the first DC-DC conversion module works in a frequency conversion mode (the on-time is controlled to be unchanged, the off-time is adjusted, and the working period is further adjusted); since the first DC-DC conversion module operates in DCM in a similar manner as it operates in BCM mode, i.e. operates in frequency conversion mode, the difference between them is only the control manner of the on-time of the power switch, and will not be described in detail later.

FIG. 2 shows a first block circuit diagram of a first DC-DC conversion module according to the present invention; the first DC-DC conversion module 2 comprises a multi-level DC-DC converter, an input terminal of which receives the input DC voltage Vin, and an output voltage Vo of an output terminal of which serves as an output voltage of the first DC-DC conversion module. When the first DC-DC conversion module 2 includes a multi-level DC-DC converter, the second DC-DC conversion module 3 may be an isolated DC-DC converter, or an isolated DC-DC converter with N input terminals connected in parallel.

In the circuit block diagram shown in fig. 2, the ac-dc conversion circuit further includes a first control circuit, and the first control circuit controls the operating state of the multi-level dc-dc converter to perform power factor correction. The first control circuit can control the working state of the multi-level DC-DC converter by adopting two control modes, wherein the two control modes respectively correspond to the two first control circuits.

The first control mode is as follows: and generating a first duty ratio signal representing a required duty ratio according to an output voltage sampling signal, an input voltage sampling signal and an inductive current sampling signal of the multi-level DC-DC converter, and generating a corresponding control signal according to the first duty ratio signal to control the on and off of each power switch in the first DC-DC conversion module. Optionally, the first control mode controls the duty cycle to be fixed, and adjusts the duty cycle (i.e., fixes the frequency) by adjusting the on-time.

Specifically, the first control circuit includes: the voltage compensation module receives an output voltage sampling signal and a voltage reference signal of the multi-level DC-DC converter and outputs a voltage compensation signal; the current reference signal generation module receives a voltage compensation signal and an input voltage sampling signal of the multilevel DC-DC converter and outputs a current reference signal; the current compensation module receives a current reference signal and an inductive current sampling signal of the multilevel DC-DC converter and outputs a first duty ratio signal; and the PWM generating module is used for generating corresponding control signals according to the first duty ratio signal so as to control the switching state of each power switch in the multi-level direct current-direct current converter. When the first control mode is adopted to control the working states of the multilevel DC-DC converters with different structures, the structures of the voltage compensation module, the current reference signal generation module and the current compensation module are the same, and the structures of the corresponding PWM generation modules of the multilevel DC-DC converters with different structures are different.

The second control mode is as follows: and controlling the on and off of each power switch in the multilevel DC-DC converter according to the output voltage sampling signal and the inductive current of the multilevel DC-DC converter. Optionally, the second control mode controls the on-time to be fixed, and adjusts the duty cycle (i.e., frequency conversion) by adjusting the duty cycle (i.e., frequency).

Specifically, the second control circuit includes: the multi-level direct current-direct current converter comprises a turn-off control circuit and a turn-on control circuit, wherein the turn-off control circuit receives an output voltage sampling signal and a first proportional coefficient of the multi-level direct current-direct current converter to generate a turn-on time signal, and controls turn-off time of partial power switches in the multi-level direct current-direct current converter (controls turn-on time of other power switches, and partial power switches and other power switches are in complementary conduction) according to the turn-on time signal; the conduction control circuit receives the inductive current of the multilevel DC-DC converter to control the conduction time of a part of power switches in the multilevel DC-DC converter (to control the turn-off time of other power switches, wherein the part of power switches and other power switches are conducted complementarily). Further, the shutdown control circuit includes: the voltage compensation circuit receives an output voltage sampling signal and a voltage reference signal of the multi-level DC-DC converter and outputs a voltage compensation signal; the on-time generating circuit receives the voltage compensation signal and a first proportional coefficient and outputs an on-time signal; and the on-time timer starts to time from the on-time of a part of power switches, and when the time reaches the on-time signal, the part of power switches are turned off. When the second control mode is adopted to control the working states of the multilevel direct current-direct current converters with different structures, the structures of the turn-off control circuits are the same, and the structures of the corresponding turn-on control circuits of the multilevel direct current-direct current converters with different structures are different. For the second control mode, the effect of applying the second control mode to the multi-level boost dc-dc converter circuit is better, the theoretical value of the corrected power factor can reach 1, and the second control mode can also reach the correction effect when being used in other types of multi-level dc-dc converter circuits, but the theoretical value of the corrected power factor cannot reach 1, and thus the description is given.

It should be noted that, since the multilevel dc-dc converter may be a dc-dc converter of any level, the subsequent multilevel dc-dc converters of different structures are all described in detail by taking a four-level dc-dc converter as an example, and a circuit structure diagram of the N +1 level dc-dc converter is given; in addition, since a plurality of embodiments of the multilevel dc-dc converter with different structures are given in the following of the present invention, for unnecessary details, the following control manner and the first control circuit are described in detail by taking the multilevel buck dc-dc converter as an example, and the control manners of the other types of multilevel dc-dc converters are similar to or the same as the control manner of the multilevel buck dc-dc converter, and reference is made to the similar or the same parts.

FIG. 3 is a circuit diagram of a first embodiment of a first DC-DC converter module according to the present invention; the first DC-DC conversion module comprises a four-level buck DC-DC converter, the four-level buck DC-DC converter comprises a switched capacitor circuit 21 and a first inductor L1, a first terminal of the switched capacitor circuit 21 is an input high potential terminal c of the first DC-DC conversion module for receiving the input DC voltage Vin, a second terminal of the switched capacitor circuit 21 is coupled to one terminal of the first inductor L1, and another terminal of the first inductor L1 is coupled to an output high potential terminal d of the first DC-DC conversion module. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end.

In this embodiment, the switched capacitor circuit 21 includes power switches S1-S6 and flying capacitors C1-C2, the power switches S1-S6 are sequentially connected in series between the input high potential end C of the first DC-DC conversion module and the ground potential to form first intermediate nodes a 1-a 5, the flying capacitor C1 is coupled between first intermediate nodes a1 and a5, the flying capacitor C2 is coupled between first intermediate nodes a2 and a4, and the second end of the switched capacitor circuit 21 is a first intermediate node a3 and is coupled to one end of a first inductor L1. Optionally, the four-level buck DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and the ground potential.

FIG. 4 is a waveform diagram illustrating the operation of a first DC-DC conversion module according to a first embodiment of the present invention; the control signals G1-G6 are respectively used for driving the power switches S1-S6. At t₀-t₁In the interval, G1, G4 and G5 are at high level, the power switches S1, S4 and S5 are turned on, and the inductor current is increased; at t₁-t₂In the interval, G4, G5 and G6 are at high level, the power switches S4, S5 and S6 are turned on, and the inductor current is reduced; at t₂-t₃In the interval, the G2, the G4 and the G6 are in a high level, the power switches S2, S4 and S6 are switched on, and the inductive current is increased; at t₃-t₄In the interval, G4, G5 and G6 are at high level, the power switches S4, S5 and S6 are turned on, and the inductor current is reduced; at t₄-t₅In the interval, the G3, the G5 and the G6 are in a high level, the power switches S3, S5 and S6 are switched on, and the inductive current is increased;at t₅-t₆In the interval, G4, G5 and G6 are high, i.e. power switches S4, S5 and S6 are turned on, the inductor current decreases, t₀-t₆Is one switching cycle.

As can be seen from fig. 4, the power switch S1 and the power switch S6 are complementarily turned on, the power switch S2 and the power switch S5 are complementarily turned on, and the power switch S3 and the power switch S4 are complementarily turned on, in order to prevent the transient short circuit phenomenon caused by the turn-off delay of the power switch, a dead time is inserted between the state switching of the power switch S1 and the power switch S6, or the power switch S2 and the power switch S5, or the power switch S3 and the power switch S4, and the subsequent complementary turning-on includes such a situation, and will not be described again. And it can be seen that 3 power switches are simultaneously turned on at any time when the four-level buck dc-dc converter operates, so that the voltage borne by each power switch is input dc voltage/3, that is, Vin/3, whereas in the conventional buck converter, the voltage borne by each power switch is input dc voltage, that is, Vin, so that the four-level buck dc-dc converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 3 × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The alternating current-direct current conversion circuit further comprises a first control circuit, the first control circuit controls the working state of the multi-level direct current-direct current converter in two control modes to correct the power factor, and the two control modes respectively correspond to the two first control circuits.

FIG. 5 is a circuit diagram of a first control circuit according to a first embodiment of the present invention; the first control circuit is configured to generate a first duty ratio signal D representing a required duty ratio according to an output voltage sampling signal SVout, an input voltage sampling signal SVin, and an inductor current sampling signal SIL of the four-level buck dc-dc converter, and generate a corresponding control signal according to the first duty ratio signal D to control on and off of each power switch in the four-level buck dc-dc converter.

The first control circuit controls the output voltage Vout through a voltage loop, and further controls the inductor current IL through a current loop. Specifically, the first control circuit includes a voltage compensation module 41, a current reference signal generation module 42, a current compensation module 43, and a PWM generation module 44, where the voltage compensation module 41 receives the output voltage sampling signal SVout and the voltage reference signal Vref and outputs a voltage compensation signal Vcmp, and specifically, the voltage compensation module 41 generates the voltage compensation signal Vcmp according to a difference between the output voltage sampling signal SVout and the voltage reference signal Vref; the current reference signal generating module 42 receives the voltage compensation signal Vcmp and the input voltage sampling signal SVin, and outputs a current reference signal Iref, specifically, the reference current signal Iref is positively correlated with a product of the voltage compensation signal Vcmp and the input voltage sampling signal SVin, and preferably, the reference current signal Iref is equal to a product of the voltage compensation signal Vcmp and the input voltage sampling signal SVin, that is, Iref is Vcmp SVin; the current compensation module 43 receives a current reference signal Iref and an inductive current sampling signal SIL, and outputs a first duty cycle signal D, and specifically, the current compensation module 43 generates a first duty cycle signal D representing a required duty cycle according to a difference value between the current reference signal Iref and the inductive current sampling signal SIL; the PWM generation module 44 generates respective control signals G1-G6 to control the turn-on and turn-off of each power switch in the first DC-DC conversion module according to the first duty cycle signal D.

FIG. 6 is a schematic circuit diagram of a PWM generating module according to a first embodiment of the present invention; the PWM generation module 44 includes: the on-state control circuit 441 and the off-state control circuit 442 are used for sequentially turning on the power switches S1-S3, and the difference between the on-state moments of the front power switch and the back power switch in the power switches S1-S3 is 1/3 switching cycles; the turn-off control circuit 442 receives the first duty ratio signal D, and is configured to control a turn-off time of each of the power switches S1 to S3 according to the first duty ratio signal D. The on-control circuit 441 and the off-control circuit 442 are further configured to control the power switches S4-S6 to control the complementary conduction of the power switch S6 and the power switch S1, the complementary conduction of the power switch S5 and the power switch S2, and the complementary conduction of the power switch S4 and the power switch S3.

Specifically, the operation of the PWM generation circuit will be described with reference to fig. 4. First, the conduction control circuit 441 controls the power switch S1 at t₀The time is on, and the turn-off control circuit 442 controls the turn-off time t of the power switch S1 according to the first duty ratio signal D₁Such that (t)₁-t₀)/(t₂-t₀) D, wherein t₂-t₀Equal to 1/3 switching cycles; the conduction control circuit 441 controls the power switch S2 from t₀The start of time is delayed 1/3 after the switching cycle (i.e., t)₂Time) on, the off control circuit 422 controls the off time t of the power switch S2 according to the first duty ratio signal D₃Such that (t)₃-t₂)/(t₄-t₂) D, wherein t₄-t₂Equal to 1/3 switching cycles; the conduction control circuit 441 controls the power switch S3 from t₀After a time start delay 2/3 switching period (i.e., t)₄Time) on, the off control circuit 422 controls the off time t of the power switch S3 according to the first duty ratio signal D₅Such that (t)₅-t₄)/(t₆-t₄) D, wherein t₆-t₄Equal to 1/3 switching cycles. Preferably, the conduction time t of the power switch S1 in each switching period is controlled by a clock signal₀. For the whole period ((t)₁-t₀)+(t₃-t₂)+(t₅-t₄))/(t₆-t₀) Where, t₆-t₀Is one switching cycle.

Optionally, the PWM generating module 44 further includes RS flip-flops 1 to 3, which are respectively used for generating control signals G1 to G3 to control the power switches S1 to S3 to be turned on and off. The conduction control circuit 441 is at t₀Outputs a set signal to the S end of the RS trigger 1 from t₀1/3 switch cycle output setting signal with time delayS terminal of RS flip-flop 2 from t₀The time begins to delay 2/3 the switching period outputs a setting signal to the S end of the RS trigger 3; the turn-off control signal 442 outputs a reset signal to the R terminal of the corresponding RS flip-flop 1-3, so as to determine the turn-off time of the power switches S1-S3 in the corresponding 1/3 switching period according to the first duty ratio signal D, so that the on-time/(1/3 switching period) of each power switch is D, and the output signals of the RS flip-flops 1-3 are the control signals G1-G3, respectively. Because the power switch S6 and the power switch S1 are complementarily turned on, the power switch S5 and the power switch S2 are complementarily turned on, and the power switch S4 and the power switch S3 are complementarily turned on, after the control signals G1 to G3 are inverted, control signals G6, G5 and G4 are respectively obtained to respectively control the on and off of the power switches S6, S5 and S4. Optionally, the conduction control circuit further includes a buffer for storing the first duty ratio signal D.

FIG. 7 is a circuit diagram of a second control circuit according to a first embodiment of the present invention; the second control circuit is used for controlling the turn-on and turn-off time of each power switch in the four-level buck DC-DC converter according to the output voltage sampling signal SVout and the inductive current IL in the four-level buck DC-DC converter.

The second first control circuit comprises an on control circuit 61 and an off control circuit 62, the on control circuit 61 receives the inductive current IL to obtain a second signal V2 representing the number of zero crossings of the inductive current each time, and generates a corresponding on trigger signal according to the second signal V2 when the inductive current passes zero each time to control the corresponding power switch of the power switches S1 to S3 to be turned on; the turn-off control circuit 62 receives the output voltage sampling signal SVout and a first scaling factor K1 to generate an on-time signal Ton, and controls the turn-off time of each of the power switches S1 to S3 according to the on-time signal Ton; the on-control circuit 61 and the off-control circuit 62 are further configured to control the power switches S4-S6, so as to control the power switch S6 and the power switch S1 to be turned on complementarily, the power switch S5 and the power switch S2 to be turned on complementarily, and the power switch S4 and the power switch S3 to be turned on complementarily.

Specifically, the conduction control circuit 61 includes a current zero-crossing detection counting circuit 611 and a conduction trigger signal generating circuit 612, where the current zero-crossing detection counting circuit 611 receives the inductor current IL and outputs a second signal V2 representing the number of zero-crossing times of the inductor current at each time; the on trigger signal generating circuit 612 receives the second signal V2 and generates a corresponding on trigger signal according to the second signal V2; a remainder of the second signal V2 divided by 3 is p, and a turn-on trigger signal corresponding to the p +1 th power switch Sp +1 is generated to correspondingly control the p +1 th power switch Sp +1 to be turned on, where p is equal to 0, 1, and 2.

The turn-off control circuit 62 includes a voltage compensation circuit 621, an on-time generation circuit 622, and an on-time timer 623, where the voltage compensation module 621 receives the output voltage sampling signal SVout and the voltage reference signal Vref and outputs a voltage compensation signal Vcmp, and specifically, the voltage compensation module 621 generates the voltage compensation signal Vcmp according to a difference between the output voltage sampling signal SVout and the voltage reference signal Vref; the on-time generating circuit 622 receives the voltage compensation signal Vcmp and the first scaling factor K1, and outputs an on-time signal Ton, specifically, the on-time signal Ton is positively correlated with a product of the voltage compensation signal Vcmp and the first scaling factor K1, and optionally, the on-time signal Ton is equal to a product of the voltage compensation signal Vcmp and the first scaling factor K1, that is, Ton is equal to Vcmp × K1; the on-time timer 623 starts to count the on-time of each of the power switches S1 to S3, and turns off the corresponding power switch when the counted time reaches the on-time signal Ton.

Optionally, in this embodiment, the first control circuit further includes RS flip-flops 1 to 3, respectively configured to generate control signals G1 to G3 to control the power switches S1 to S3 to turn on and off. The conduction control circuit 61 generates a conduction trigger signal corresponding to the power switch S1 as a corresponding reset signal to be output to the S terminal of the RS flip-flop 1 when the remainder of division by 3 of the second signal V2 is 0, generates a conduction trigger signal corresponding to the power switch S2 as a corresponding reset signal to be output to the S terminal of the RS flip-flop 2 when the remainder of division by 3 of the second signal V2 is 1, and generates a conduction trigger signal corresponding to the power switch S3 as a corresponding reset signal to be output to the S terminal of the RS flip-flop 3 when the remainder of division by 3 of the second signal V2 is 2; the turn-off control circuit 62 starts timing at the turn-on time of each power switch of the power switches S1-S3, and outputs a reset signal to the R end of the corresponding RS flip-flop 1-3 when the timing reaches the turn-on time signal Ton; the output signals of the RS triggers 1-3 are control signals G1-G3 respectively. Because the power switch S6 and the power switch S1 are complementarily turned on, the power switch S5 and the power switch S2 are complementarily turned on, and the power switch S4 and the power switch S3 are complementarily turned on, after the control signals G1 to G3 are inverted, control signals G6, G5 and G4 are respectively obtained to respectively control the on and off of the power switches S6, S5 and S4.

In the first embodiment, the first DC-DC conversion module is a 4-level buck DC-DC converter, and in other embodiments, the first DC-DC conversion module may be a buck DC-DC converter with any level, as shown in fig. 8, which provides a circuit schematic diagram of a second embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC is an N +1 level buck DC-DC converter, and N is larger than 1.

Specifically, the N +1 level buck DC-DC converter includes a switched capacitor circuit 21 and a first inductor L1, a first terminal of the switched capacitor circuit 21 is an input high potential terminal c of the first DC-DC conversion module for receiving the input DC voltage Vin, a second terminal of the switched capacitor circuit 21 is coupled to one terminal of the first inductor L1, and another terminal of the first inductor L1 is coupled to an output high potential terminal d of the first DC-DC conversion module. The switched capacitor circuit 21 in the second embodiment is different from that in the first embodiment, and the rest is the same.

In the present embodiment, the switched capacitor circuit 21 includes 2N power switches S1-S2N and N-1 flying capacitors C1-CN-1, the 2N power switches S1-S2N are sequentially connected in series between the input high potential end C of the first DC-DC conversion module and the ground potential to form 2N-1 first intermediate nodes a 1-a 2N-1, the mth flying capacitor Cm is coupled between the mth first intermediate node am and the 2N-m first intermediate nodes a2N-m, the second end of the switched capacitor circuit is the nth first intermediate node aN and is coupled to one end of the first inductor L, where m is not greater than N-1.

When the N +1 level buck DC-DC converter works, the 2N-N +1 power switch S2N-N +1 and the nth power Sn switch are conducted in a complementary mode, and N is not more than N. At any time when the N +1 level buck dc-dc converter works, N power switches are turned on simultaneously, that is, the voltage borne by each power switch is input dc voltage/N, that is, Vin/N, whereas in a conventional buck converter, the voltage borne by each power switch is input dc voltage, that is, Vin, so that the N +1 level buck dc-dc converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is N × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The alternating current-direct current conversion circuit further comprises a first control circuit, and the first control circuit is used for controlling the working state of the N +1 level buck direct current-direct current converter so as to carry out power factor correction.

The first control circuit of the second embodiment is similar to the first control circuit of the first embodiment, except that: the PWM generating module 44 has a different structure, and is configured to control the switching states of the 2N power switches. In this embodiment, the PWM generating module 44 includes: the on-state control circuit 441 and the off-state control circuit 442 are respectively configured to sequentially turn on the first N power switches S1-SN, where the on-state times of the front and rear power switches in the first N power switches S1-SN are different by 1/N switching period, and preferably, the on-state time of the first power switch S1 in each switching period is controlled by a clock signal; the turn-off control circuit 442 receives the first duty ratio signal D, and is configured to control a turn-off time of each of the first N power switches S1 to SN according to the first duty ratio signal D. The on-control circuit 441 and the off-control circuit 442 are further configured to control the last N power switches SN +1 to S2N, where the 2N-N +1 th power switch S2N-N +1 is complementarily turned on with the nth power switch SN, and N is not greater than N.

The second control circuit of the second embodiment is similar to the first control circuit of the first embodiment, except that: the conduction control circuit 61 has different structures and is configured to control the switching states of the 2N power switches. In this embodiment, the first control circuit includes an on control circuit 61 and an off control circuit 62, where the on control circuit 61 receives the inductor current IL to obtain a second signal V2 representing the number of times of zero crossing of the inductor current each time, and generates a corresponding on trigger signal according to the second signal V2 when the inductor current crosses zero each time, so as to control the corresponding power switch of the first N power switches S1 to SN to be on; the turn-off control circuit 62 receives the voltage sampling signal SVout and the first scaling factor K1 to generate an on-time signal Ton, and controls the turn-off time of each of the first N power switches S1 to SN according to the on-time signal Ton; the on-control circuit 61 and the off-control circuit 62 are further configured to control the last N power switches SN +1 to S2N, where the 2N-N +1 th power switch S2N-N +1 and the nth power switch SN are complementarily turned on, and N is not greater than N. Specifically, the conduction control circuit 61 includes a current zero-crossing detection counting circuit 611 and a conduction trigger signal generating circuit 612, where the current zero-crossing detection counting circuit 611 receives the inductor current IL and outputs a second signal V2 representing the number of zero-crossing times of the inductor current at each time; the on trigger signal generating circuit 612 receives the second signal V2, and generates a corresponding on trigger signal according to the second signal V2; a remainder of the second signal V2 divided by N is p, and a turn-on trigger signal corresponding to the p +1 th power switch Sp +1 is generated to correspondingly control the p +1 th power switch Sp +1 to be turned on, where p is smaller than N.

The switched capacitor circuit 21 in the first and second embodiments may be replaced by any switched capacitor converter, as shown in fig. 9, which shows a circuit schematic diagram of a third embodiment of a first DC-DC conversion module according to the present invention, where the first DC-DC conversion module is a buck DC-DC converter of a switched capacitor converter type, and the difference between the third and first embodiments is that: the switched capacitor circuit 21 has a different structure, and the rest is the same. In this embodiment, the switched capacitor circuit 21 is a switched capacitor converter, the switched capacitor circuit 21 includes power switches S1 to S4, a capacitor C1 and a capacitor C2, the power switches S4 to S1 are sequentially connected in series between an input high potential end C of the first DC-DC conversion module and a ground potential, a first end of the first inductor L1 is coupled to a common end of the power switch S1 and the power switch S2, and a second end of the first inductor L1 is coupled to an output high potential end d of the first DC-DC conversion module. One end of the capacitor C1 is coupled to the common terminal of the power switch S4 and the power switch S3, the other end of the capacitor C1 is coupled to the first end of the first inductor L1, one end of the capacitor C2 is coupled to the common terminal of the power switch S3 and the power switch S2, and the other end of the capacitor C2 is grounded. Wherein the power switch S1 and the power switch S3 are turned on and off simultaneously, the power switch S2 and the power switch S4 are turned on and off simultaneously, and the power switch S1 and the power switch S2 are turned on complementarily.

The ac-dc converter circuit further includes a first control circuit for controlling the operating state of a buck dc-dc converter of the switched capacitor converter type shown in the third embodiment to perform power factor correction.

The first control circuit of the third embodiment is similar to the first control circuit of the first embodiment, except that: the PWM generation module 44 has a different structure for controlling the switching states of the power switches S4-S1. In this embodiment, the PWM generating module 44 includes: a turn-on control circuit 441 and a turn-off control circuit 442, wherein the turn-on control circuit 441 is used for simultaneously turning on the power switches S1 and S3, and the turn-off control circuit 442 is used for receiving the first duty ratio signal D and controlling the turn-off time of the power switches S1 and S3 according to the first duty ratio signal D. The on control circuit 441 and the off control circuit 442 are further configured to control the operating states of the power switches S2 and S4, and the power switches S2 and S4 are complementarily turned on with the power switches S1 and S3. Optionally, the turn-on time of the power switches S1 and S3 is controlled by a clock signal.

The second control circuit in the third embodiment is similar to the second control circuit in the first embodiment, except that: the conduction control circuit 61 has a different structure for controlling the switching states of the power switches S4-S1. In this embodiment, the first control circuit includes an on control circuit 61 and an off control circuit 62, the on control circuit 61 receives the inductor current IL, and generates an on trigger signal to control the power switches S1 and S3 to be turned on when the inductor current crosses zero; the turn-off control circuit 62 receives the voltage sampling signal SVout and the first scaling factor K1 to generate an on-time signal Ton, and controls the turn-off time of the power switches S1 and S3 according to the on-time signal Ton; the on control circuit 61 and the off control circuit 62 are further configured to control the operating states of the power switches S2 and S4, and the power switches S2 and S4 are complementarily turned on with the power switches S1 and S3.

It should be noted that, in the third embodiment, only one structure in which the switched capacitor circuit 21 is a switched capacitor converter is shown, and in other embodiments, the switched capacitor 21 may be any type of switched capacitor converter. The principle of turning on and off the power switch in the buck dc-dc converter of the switched capacitor converter type is the same as that of turning on and off the switched capacitor converter when the switched capacitor converter operates alone (for example, when the switched capacitor converter in the third embodiment operates alone, the power switch S1 and the power switch S3 are turned on and off at the same time, the power switch S2 and the power switch S4 are turned on and off at the same time, and the power switch S1 and the power switch S2 are turned on complementarily), so that the operating state of the buck dc-dc converter of the switched capacitor converter type can be controlled by using two control modes.

Fig. 10 is a circuit diagram of a fourth embodiment of a first DC-DC conversion module according to the present invention; the first DC-DC conversion module includes a four-level boost DC-DC converter, the four-level boost DC-DC converter includes a switched capacitor circuit 21 and a first inductor L1, one end of the first inductor L1 is coupled to the input high potential terminal c of the first DC-DC conversion module for receiving the input DC voltage Vin, the other end of the first inductor L1 is coupled to the first end of the switched capacitor circuit 21, and the second end of the switched capacitor circuit 21 is the output high potential terminal d of the first DC-DC conversion module. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end.

In this embodiment, the switched capacitor circuit 21 includes power switches S1-S6 and flying capacitors C1-C2, the power switches S1-S6 are sequentially connected in series between the output high potential end d of the first DC-DC conversion module and the ground potential to form first intermediate nodes a 1-a 5, the flying capacitor C1 is coupled between first intermediate nodes a1 and a5, the flying capacitor C2 is coupled between first intermediate nodes a2 and a4, and the first end of the switched capacitor circuit 21 is a first intermediate node a3 and is coupled to the other end of the first inductor L1. Optionally, the four-level boost DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and a ground potential.

Fig. 11 is a waveform diagram illustrating operation of a fourth embodiment of the first DC-DC conversion module according to the present invention, wherein the control signals G1-G6 are respectively used for driving the power switches S1-S6. At t₀-t₁In the interval, G1, G4 and G5 are at high level, the power switches S1, S4 and S5 are turned on, and the inductor current is reduced; at t₁-t₂In the interval, G4, G5 and G6 are at high level, the power switches S4, S5 and S6 are turned on, and the inductor current is increased; at t₂-t₃In the interval, the G2, the G4 and the G6 are in a high level, the power switches S2, S4 and S6 are conducted, and the inductive current is reduced; in a section from t3 to t4, G4, G5 and G6 are at high level, power switches S4, S5 and S6 are conducted, and the inductive current is increased; at t₄-t₅In the interval, the G3, the G5 and the G6 are in a high level, the power switches S3, S5 and S6 are conducted, and the inductive current is reduced; at t₅-t₆In the interval, G4, G5 and G6 are high level, the power switches S4, S5 and S6 are conducted, the inductive current is increased, t₀-t₆Is one switching cycle.

As seen in fig. 11, the power switch S1 and the power switch S6 are complementarily conductive, the power switch S2 and the power switch S5 are complementarily conductive, and the power switch S3 and the power switch S4 are complementarily conductive. And it can be seen that at any time when the four-level boost dc-dc converter operates, three power switches are turned on simultaneously, and each power switch bears an output voltage of/3, i.e. Vo/3, whereas in the conventional boost converter, each power switch bears an output voltage, i.e. Vo, so that the four-level boost dc-dc converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 3 × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

In this embodiment, the ac-dc conversion circuit further includes a first control circuit, and the first control circuit controls the operating state of the four-level boost dc-dc converter in two control modes to perform power factor correction. The two kinds of first control circuits in this embodiment are the same as the two kinds of first control circuits in the first embodiment, and are not described herein again.

In a fourth embodiment, the first DC-DC conversion module is a 4-level boost DC-DC converter, and in other embodiments, the first DC-DC conversion module may be a boost DC-DC converter with any level, as shown in fig. 12, which provides a circuit schematic diagram of a fifth embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC conversion module is an N +1 level boost DC-DC converter, and N is larger than 1.

The N +1 level boost DC-DC converter comprises a switched capacitor circuit 21 and a first inductor L1, wherein one end of the first inductor L1 is coupled to the input high potential end c of the first DC-DC conversion module for receiving the input DC voltage Vin, the other end of the first inductor L1 is coupled to the first end of the switched capacitor circuit 21, and the second end of the switched capacitor circuit 21 is the output high potential end d of the first DC-DC conversion module. The switched capacitor circuit 21 in the fifth embodiment is different from that in the fourth embodiment, and the rest is the same.

In this embodiment, the switched capacitor circuit 21 includes 2N power switches S1-S2N and N-1 flying capacitors C1-CN-1, the 2N power switches S1-S2N are sequentially connected in series between the output high potential terminal d of the first DC-DC conversion module and the ground potential to form 2N-1 first intermediate nodes a 1-a 2N-1, the mth flying capacitor Cm is coupled between the mth first intermediate node am and the 2N-m first intermediate nodes a2N-m, the second terminal of the switched capacitor circuit is the nth first intermediate node aN and is coupled to the other terminal of the first inductor L1, where m is not greater than N-1.

When the N +1 level boost direct current-direct current converter works, the 2N-N +1 power switch S2N-N +1 and the nth power Sn switch are conducted in a complementary mode, and N is not larger than N. At any time when the N +1 level boost direct current-direct current converter works, N power switches are simultaneously conducted, that is, the voltage borne by each power switch is output voltage/N, that is, Vo/N, in the conventional boost converter, the voltage borne by each power switch is output voltage, that is, Vo, so that the N +1 level buck direct current-direct current converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is N × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The alternating current-direct current conversion circuit further comprises a first control circuit, and the first control circuit controls the working state of the N +1 level boost direct current-direct current converter in two control modes to correct the power factor. The two kinds of first control circuits in this embodiment are the same as the two kinds of first control circuits in the second embodiment, and are not described herein again.

In addition, the switched capacitor circuit 21 in the fourth embodiment and the switched capacitor circuit in the fifth embodiment may also be replaced by any switched capacitor converter, and the structure and the control method thereof are similar to those in the third embodiment, and are not described herein again.

Fig. 13 is a circuit diagram of a sixth embodiment of a first DC-DC conversion module according to the present invention; the first DC-DC conversion module comprises a four-level buck-boost DC-DC converter, the four-level buck-boost DC-DC converter comprises a switched capacitor circuit 21 and a first inductor L1, a first terminal of the switched capacitor circuit 21 is an input high potential terminal c of the first DC-DC conversion module for receiving the input DC voltage Vin, a second terminal of the switched capacitor circuit 21 is an output high potential terminal d of the first DC-DC conversion module, a third terminal of the switched capacitor circuit 21 is coupled to one terminal of the first inductor L1, and the other terminal of the first inductor is grounded. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end.

In this embodiment, the switched capacitor circuit 21 includes power switches S1-S6 and flying capacitors C1-C2, the power switches S1-S6 are sequentially connected in series between an input high potential terminal C of the first DC-DC conversion module and an output high potential terminal d of the first DC-DC conversion module to form first intermediate nodes a 1-a 5, the flying capacitor C1 is coupled between first intermediate nodes a1 and a5, the flying capacitor C2 is coupled between the first intermediate nodes a2 and a4, and a third terminal of the switched capacitor circuit 21 is a first intermediate node a3 and is coupled to one terminal of a first inductor L1. Optionally, the four-level buck-boost DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and the ground potential.

Fig. 14 is a waveform diagram illustrating operation of a sixth embodiment of the first DC-DC conversion module according to the present invention, wherein the control signals G1-G6 are respectively used for driving the power switches S1-S6. At t₀-t₁In the interval, G1, G4 and G5 are at high level, the power switches S1, S4 and S5 are turned on, and the inductor current is increased; at t₁-t₂In the interval, G4, G5 and G6 are at high level, the power switches S4, S5 and S6 are turned on, and the inductor current is reduced; at t₂-t₃In the interval, the G2, the G4 and the G6 are in a high level, the power switches S2, S4 and S6 are switched on, and the inductive current is increased; at t₃-t₄In the interval, G4, G5 and G6 are high level, power switches S4, S5 and S6 are conducted, and the inductorThe current is reduced; at t₄-t₅In the interval, the G3, the G5 and the G6 are in a high level, the power switches S3, S5 and S6 are switched on, and the inductive current is increased; at t₅-t₆In the interval, G4, G5 and G6 are high level, the power switches S4, S5 and S6 are conducted, the inductive current is reduced, and t₀-t₆Is one switching cycle.

As seen in fig. 14, the power switch S1 and the power switch S6 are complementarily conductive, the power switch S2 and the power switch S5 are complementarily conductive, and the power switch S3 and the power switch S4 are complementarily conductive. And it can be seen that at any time when the four-level buck-boost dc-dc converter operates, three power switches are turned on simultaneously, and the voltage borne by each power switch is 1/3, namely 1/3 (Vo + Vin), of the sum of the output voltage Vo and the input dc voltage Vin, whereas in the conventional buck-boost (inverse voltage) converter, the voltage borne by each power switch is Vo and the sum of the input dc voltage Vin, namely Vo + Vin, so that the four-level buck dc-dc converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 3 × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

In this embodiment, the ac-dc conversion circuit further includes a first control circuit, and the first control circuit controls the operating state of the four-level buck-boost dc-dc converter (reverse voltage) in two control manners to perform power factor correction. The two kinds of first control circuits in this embodiment are the same as the two kinds of first control circuits in the first embodiment, and are not described herein again.

In a sixth embodiment, the first DC-DC conversion module is a 4-level buck-boost DC-DC converter (inverse voltage), and in other embodiments, the first DC-DC conversion module may be a buck-boost DC-DC converter with any level, as shown in fig. 15, which provides a circuit schematic diagram of a seventh embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC conversion module is an N +1 level buck-boost (reverse voltage) DC-DC converter, and N is larger than 1.

The N +1 level buck-boost DC-DC converter comprises a switched capacitor circuit 21 and a first inductor L1, wherein a first terminal of the switched capacitor circuit 21 is an input high potential terminal c of the first DC-DC conversion module for receiving the input DC voltage Vin, a second terminal of the switched capacitor circuit 21 is an output high potential terminal d of the first DC-DC conversion module, a third terminal of the switched capacitor circuit 21 is coupled to one terminal of the first inductor L1, and the other terminal of the first inductor L1 is grounded. The switched capacitor circuit 21 in the seventh embodiment is different from that in the sixth embodiment, and the rest is the same.

In the present embodiment, the switched capacitor circuit 21 includes 2N power switches S1-S2N and N-1 flying capacitors C1-CN-1, the 2N power switches S1-S2N are sequentially connected in series between the input high potential terminal C of the first DC-DC conversion module and the output high potential terminal d of the first DC-DC conversion module to form 2N-1 first intermediate nodes a 1-a 2N-1, the mth flying capacitor Cm is coupled between the mth first intermediate node am and the 2N-m first intermediate nodes a2N-m, the third terminal of the switched capacitor circuit 21 is the nth first intermediate node aN, and is coupled to one terminal of a first inductor L1, where m is not greater than N-1.

When the N +1 level buck-boost direct current-direct current converter (inverse voltage) works, the 2N-N +1 power switch S2N-N +1 and the nth power Sn switch are conducted in a complementary mode, and N is not larger than N. In the conventional buck-boost converter, the voltage borne by each power switch is the sum of the output voltage Vo and the input direct-current voltage Vin, namely Vo + Vin, so that the N +1 level buck-boost direct-current converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is N × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The alternating current-direct current conversion circuit further comprises a first control circuit, and the first control circuit controls the working state of the N +1 level buck-boost direct current-direct current converter in two control modes to correct the power factor. The two kinds of first control circuits in this embodiment are the same as the two kinds of first control circuits in the second embodiment, and are not described herein again.

In addition, the switched capacitor circuit 21 in the sixth and seventh embodiments may also be replaced by any switched capacitor converter, and the structure and the control method thereof are similar to those in the third embodiment, and are not described herein again.

Fig. 16 is a circuit diagram of an eighth embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC conversion module includes a four-level buck-boost (positive voltage) DC-DC converter, the four-level buck-boost DC-DC converter includes a first switched capacitor circuit 211, a second switched capacitor circuit 212 and a first inductor L1, a first terminal of the first switched capacitor circuit 211 is an input high potential terminal c of the first DC-DC conversion module for receiving the input DC voltage Vin, a second terminal of the first switched capacitor circuit 211 is coupled to one terminal of the first inductor L1, another terminal of the first inductor L35 1 is coupled to a first terminal of the second switched capacitor circuit 212, and a second terminal of the second switched capacitor circuit 212 is an output high potential terminal d of the first DC-DC conversion module. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end.

In this embodiment, the first switched capacitor circuit 211 includes first power switches S1-S6 and first flying capacitors C1-C2, the first power switches S1-S6 are sequentially connected in series between the input high potential end C of the first DC-DC conversion module and the ground potential to form first intermediate nodes a 1-a 5, the first flying capacitor C1 is coupled between first intermediate nodes a1 and a5, the first flying capacitor C2 is coupled between first intermediate nodes a2 and a4, and the second end of the first switched capacitor circuit 211 is a first intermediate node a3 and is coupled to one end of a first inductor L1. The second switched capacitor circuit 212 includes second power switches M1-M6 and second flying capacitors c 1-c 2, the second power switches M1-M6 are sequentially connected in series between the output high potential end d of the first DC-DC conversion module and the ground potential to form second intermediate nodes b 1-b 5, the second flying capacitor c1 is coupled between second intermediate nodes b1 and b5, the second flying capacitor c2 is coupled between second intermediate nodes b2 and b4, and the first end of the second switched capacitor circuit 212 is a second intermediate node b3 and is coupled to the other end of the first inductor L1. Optionally, the four-level buck-boost DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and the ground potential.

Fig. 17 is a waveform diagram illustrating an operation of an eighth embodiment of the first DC-DC conversion module according to the present invention, wherein the control signals G1-G6 are respectively used for driving the first power switches S1-S6, and the control signals G1-G6 are respectively used for driving the second power switches M1-M6. At t₀-t₁In the interval, G1, G4, G5, G4, G5 and G6 are at a high level, the first power switches S1, S4 and S5 and the second power switches M4, M5 and M6 are turned on, and the inductor current increases; at t₁-t₂In the interval, G4, G5, G6, G1, G4 and G5 are at a high level, the first power switches S4, S5 and S6 and the second power switches M1, M4 and M5 are turned on, and the inductor current is reduced; at t₂-t₃In the interval, the G2, G4, G6, G4, G5 and G6 are at a high level, the first power switches S2, S4 and S6 are turned on, and the second power switches M4, M5 and M6 are turned on, so that the inductor current is increased; at t₃-t₄In the interval, G4, G5, G6, G2, G4 and G6 are at a high level, the first power switches S4, S5 and S6 and the second power switches M2, M4 and M6 are turned on, and the inductor current is reduced; at t₄-t₅In the interval, the G3, G5, G6, G4, G5 and G6 are at a high level, the first power switches S3, S5 and S6 and the second power switches M4, M5 and M6 are turned on, and the inductor current is increased; at t₅-t₆In the section, G4, G5, G6, G3, G5 and G6 are high, and firstThe power switches S4, S5 and S6 and the second power switches M3, M5 and M6 are turned on, the inductor current decreases, t₀-t₆Is one switching cycle.

As seen in fig. 17, the first power switches S1 and S6 are complementarily conductive, the first power switches S2 and S5 are complementarily conductive, and the first power switches S3 and S4 are complementarily conductive; the second power switches M1 and M6 are complementarily conductive, the second power switches M2 and M5 are complementarily conductive, and the second power switches M3 and M4 are complementarily conductive. The second power switch M1 turns on after the first power switch S1 turns off until the first power switch S2 turns on, the second power switch M2 turns on after the first power switch S2 turns off until the first power switch S3 turns on, and the second power switch M3 turns on after the first power switch S3 turns off until the first power switch S1 turns on for the next switching cycle. And it can be seen that, at any time when the four-level buck-boost dc-dc converter operates, the first switched-capacitor circuit 211 and the second switched-capacitor circuit 212 each have three power switches that are turned on at the same time, each power switch in the first switched-capacitor circuit 211 is exposed to 1/3 times the input dc voltage Vin, 1/3 Vin, each power switch in the second switched capacitor circuit 212 is exposed to a voltage 1/3 of the output voltage Vo, 1/3 Vo, whereas in a conventional buck-boost converter, the power switch is exposed to an output voltage Vo or an input dc voltage Vin, therefore, the four-level buck-boost DC-DC converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 3 × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

In this embodiment, the ac-dc conversion circuit further includes two first control circuits, and the first control circuits control the operating state of the multilevel dc-dc converter in two control manners to perform power factor correction. Specifically, the two first control circuits are respectively used for controlling the switching states of the power switches in the first switched capacitor circuit 211 and the second switched capacitor circuit 212. The two kinds of first control circuits in this embodiment are similar to the two kinds of first control circuits in the first embodiment, and are not described herein again.

In an eighth embodiment, the first DC-DC conversion module is a 4-level buck-boost DC-DC converter (positive voltage), and in other embodiments, the first DC-DC conversion module may be a buck-boost DC-DC converter with any level, as shown in fig. 18, which provides a circuit schematic diagram of a ninth embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC conversion module is an N +1 level buck-boost (positive voltage) DC-DC converter, and N is larger than 1.

The N +1 level buck-boost DC-DC converter comprises a first switched capacitor circuit 211, a second switched capacitor circuit 212 and a first inductor L1, wherein a first terminal of the first switched capacitor circuit 211 is an input high potential terminal c of the first DC-DC conversion module for receiving the input DC voltage Vin, a second terminal of the first switched capacitor circuit 211 is coupled to a terminal of the first inductor L1, another terminal of the first inductor L1 is coupled to a first terminal of the second switched capacitor circuit 212, and a second terminal of the second switched capacitor circuit 212 is an output high potential terminal d of the first DC-DC conversion module. The first switched capacitor circuit 211 and the second switched capacitor circuit 212 in the ninth embodiment are different from those in the eighth embodiment, and the rest parts are the same.

In this embodiment, the first switched capacitor circuit 211 includes 2N first power switches S1-S2N and N-1 first flying capacitors C1-CN-1, the 2N first power switches S1-S2N are sequentially connected in series between the input high potential end C of the first DC-DC conversion module and the ground potential to form 2N-1 first intermediate nodes a 1-a 2N-1, the mth first flying capacitor Cm is coupled between the mth first intermediate node am and the 2N-m first intermediate nodes a2N-m, the second end of the first switched capacitor circuit 211 is the nth first intermediate node aN and is coupled to one end of a first inductor L1; the second switched capacitor circuit 212 comprises 2N first power switches M1-M2N and N-1 second flying capacitors c 1-cN-1, the 2N second power switches M1-M2N are sequentially connected in series between the output high potential end d of the first DC-DC conversion module and the ground potential to form 2N-1 second intermediate nodes b 1-b 2N-1, the mth second flying capacitor cm is coupled between the mth second intermediate node bm and the 2N-M second intermediate nodes b2N-M, the first end of the second switched capacitor circuit 212 is the nth second intermediate node bN and is coupled to the other end of the first inductor L1, wherein M is not more than N-1.

When the N +1 level buck-boost DC-DC converter (positive voltage) works, the 2N-N +1 first power switch S2N-N +1 and the nth first power Sn switch are conducted in a complementary mode, the 2N-N +1 second power switch M2N-N +1 and the nth second power Mn switch are conducted in a complementary mode, and N is not more than N. The e-th second power switch Me is turned on after the e-th first power switch Se is turned off until the e + 1-th first power switch Se +1 is turned on, e is smaller than N, and the N-th second power switch MN is turned on after the N-th first power switch SN is turned off until the first power switch S1 is turned on in the next switching period. At any time when the N +1 level buck-boost dc-dc converter is operating, the first switched-capacitor circuit 211 and the second switched-capacitor circuit 212 each have N power switches that are turned on simultaneously, each power switch in the first switched capacitor circuit 211 is subjected to a voltage 1/N of the input dc voltage Vin, i.e., 1/N Vin, each power switch in the second switched capacitor circuit 212 is exposed to a voltage of 1/N of the output voltage Vo, i.e., 1/N Vo, whereas in a conventional buck-boost converter, the power switch is subjected to an output voltage Vo or an input dc voltage Vin, therefore, the N +1 level buck-boost DC-DC converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is N × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The alternating current-direct current conversion circuit further comprises two first control circuits, and the two first control circuits are used for controlling the working state of the N +1 level buck-boost direct current-direct current converter so as to carry out power factor correction. The first control circuit controls the working state of the multi-level DC-DC converter in two control modes to carry out power factor correction. Specifically, the two first control circuits are respectively used for controlling the switching states of the power switches in the first switched capacitor circuit 211 and the second switched capacitor circuit 212. The two kinds of first control circuits in this embodiment are similar to the two kinds of first control circuits in the second embodiment, and are not described herein again.

In addition, the first switched capacitor circuit 211 and the second switched capacitor circuit 212 in the eighth and ninth embodiments may also be replaced by any switched capacitor converter, and the structure and the control method thereof are similar to those in the third embodiment, and are not described herein again.

Fig. 19 is a circuit diagram of a tenth embodiment of a first DC-DC conversion module according to the present invention; the first DC-DC conversion module comprises a four-level cuk DC-DC converter, the four-level cuk DC-DC converter comprises first power switches S1-S3, second power switches M1-M3, flying capacitors C1-C2, a first inductor L1, a second inductor L2 and a first capacitor C1, one end of the first inductor L1 is coupled to the input high potential end C of the first DC-DC conversion module for receiving the input DC voltage Vin, the other end of the first inductor L1 is coupled to one end of the first capacitor C1, the other end of the first capacitor C1 is coupled to one end of the second inductor L2, the other end of the second inductor L2 is coupled to the output high potential end d of the first DC-DC conversion module, the first power switches S1-S3 are sequentially connected in series between the first inductor L1 and the common end of the first capacitor C1 and the ground potential, to form first intermediate nodes a1 and a2, the second power switches M1-M3 are connected in series between the common terminal of the second inductor L2 and the first capacitor C1 and the ground potential to form second intermediate nodes b1 and b2, the flying capacitor C1 is coupled between the first intermediate node a1 and the second intermediate node b1, the flying capacitor C2 is coupled between the first intermediate node a2 and the second intermediate node b2, the input low potential terminal of the first DC-DC conversion module is the ground potential terminal, and the output low potential terminal of the first DC-DC conversion module is the ground potential terminal. Optionally, the four-level cuk DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and a ground potential.

Fig. 20 is a waveform diagram illustrating the operation of a first embodiment of the DC-DC conversion module of the present invention, where the control signals G1-G3 are respectively used to drive the power switches S1-S3, and the control signals G1-G3 are respectively used to drive the second power switches M1-M3. At t₀-t₁In the interval, G2, G3 and G1 are high, the first power switches S2 and S3 and the second power switch M1 are turned on, and the current in the second inductor L2 is increased; at t₁-t₂In the interval, g1, g2 and g3 are high level, the second power switches M1, M2 and M3 are turned on, and the current on the second inductor L2 is reduced; at t₂-t₃In the interval, G3, G1 and G2 are high, the first power switch S3 and the second power switches M1 and M2 are turned on, and the current on the second inductor L2 is increased; at t₃-t₄In the interval, g1, g2 and g3 are high level, the second power switches M1, M2 and M3 are turned on, and the current on the second inductor L2 is reduced; at t₄-t₅In the interval, the G1, the G2 and the G3 are in a high level, the first power switches S1, S2 and S3 are turned on, and the current on the second inductor L2 is increased; at t₅-t₆In the interval, g1, g2 and g3 are high level, the second power switches M1, M2 and M3 are turned on, the current on the second inductor L2 is reduced, and t is₀-t₆Is one switching cycle. Wherein, the interval t₀-t₁，t₂-t₃And t₄-t₅Equal, interval t₁-t₂，t₃-t₄，t₅-t₆Are equal.

As seen in fig. 20, the first power switch S1 and the second power switch M1 are complementarily conductive, the first power switch S2 and the second power switch M2 are complementarily conductive, and the first power switch S3 and the second power switch M3 are complementarily conductive. The first power switch S1 is turned on once in one switching period, the first power switch S2 is turned on twice in one switching period, the first power switch S3 is turned on three times in one switching period, and the three first power switches S1-S3 are turned on for the same time each time. In one switching cycle, the first power switch S3 is turned off 3 times, and the turn-off time of each time is equal. And it can be seen that at any time when the four-level cuk dc-dc converter operates, three power switches are simultaneously turned on, that is, the voltage borne by each power switch is 1/3, namely 1/3 (Vo + Vin), of the sum of the output voltage Vo and the input dc voltage Vin, whereas in the conventional cuk converter, the voltage borne by each power switch is Vo and the sum of the input dc voltage Vin, namely Vo + Vin, so that the four-level cuk dc-dc converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 3 × fs, so in this embodiment, the second inductor L2 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

In this embodiment, the ac-dc conversion circuit further includes a first control circuit, and the first control circuit controls the operating state of the four-level cuk dc-dc converter in two control modes to perform power factor correction. The first control circuit of the tenth embodiment is similar to the first control circuit of the first embodiment, except that: the PWM generating module 44 has different structures and is configured to control the switching states of the first power switches S1 to S3 and the second power switches M1 to M3. In this embodiment, the PWM generating module 44 receives the first duty ratio signal D, and is configured to turn on the q-th first power switch Sq q times within one switching period, where q is not greater than 3, specifically, turn on the first power switch S1 once, turn on the first power switch S2 twice, turn on the first power switch S3 three times, and turn on the three first power switches S1-S3 for the same turn-on time (i.e., the interval t is t) each time₀-t₁，t₂-t₃And t₄-t₅Equal), controlling the on-time of each first power switch each time according to the first duty ratio signal D; in which the first power switch S3 is turned off 3 times in one switching period, and the turn-off time of each time is equal (i.e. interval)t₁-t₂，t₃-t₄，t₅-t₆Equal) to (t), thereby (t)₁-t₀) Divided by (t)₂-t₀) Is equal to the first duty cycle signal D, t₂-t₀Equal to one third of the switching period, so (t)₁-t₀) The division by one third of the switching period is equal to the first duty cycle signal D, thereby obtaining the turn-off time of each of the first power switches S1-S3. Optionally, the turn-on time of each of the first power switches S1 to S3 is controlled by a clock signal. The PWM generating module 44 is further configured to control the second power switches M1-M3, control the second power switch M1 and the first power switch S1 to be complementarily turned on, control the second power switch M2 and the first power switch S2 to be complementarily turned on, and control the second power switch M3 and the first power switch S3 to be complementarily turned on. The inductor current sampling signal in the first control circuit is a sampling signal of a current flowing through the second inductor L2. The second type of first control circuit in the tenth embodiment is similar to the second type of first control circuit in the first embodiment, and is not repeated here.

In a tenth embodiment, the first DC-DC conversion module is a 4-level cuk DC-DC converter, and in other embodiments, the first DC-DC conversion module may be a cuk DC-DC converter with any level, as shown in fig. 21, a circuit schematic diagram of an eleventh embodiment of the first DC-DC conversion module of the present invention is provided; the first DC-DC conversion module is an N +1 level cuk DC-DC converter, and N is larger than 1.

The N +1 level cuk DC-DC converter comprises N first power switches S1-SN, N second power switches M1-MN, N-1 flying capacitors C1-CN-1, a first inductor L1, a second inductor L2 and a first capacitor C1, wherein one end of the first inductor L1 is coupled to the input high potential end C of the first DC-DC conversion module for receiving the input DC voltage Vin, the other end of the first inductor L1 is coupled to one end of the first capacitor C1, the other end of the first capacitor C1 is coupled to one end of the second inductor L2, the other end of the second inductor L2 is coupled to the output high potential end d of the first DC-DC conversion module, the N first power switches S1-SN are sequentially connected in series between the common end of the first inductor L1 and the first capacitor C1 and the ground potential to form N-1 intermediate nodes a-N-1 a-N-1, the N second power switches M1-MN are sequentially connected in series between the common terminal of the second inductor L2 and the first capacitor c1 and the ground potential to form N-1 second intermediate nodes b 1-bN-1, the mth flying capacitor Cm is coupled between the mth first intermediate node am and the mth second intermediate node bm, and M is not larger than N-1. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end. Optionally, the N +1 level cuk DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and the ground potential.

When the N +1 level cuk direct current-direct current converter works, the nth second power switch Mn and the nth first power switch Sn are conducted in a complementary mode, and N is not larger than N. The nth first power switch Sn is conducted N times in one switching period, and the conducting time of each conduction of the N first power switches S1-SN is the same. In a switching period, the nth first power switch SN is turned off N times, and the turn-off time of each time is equal. In the conventional cuk converter, the voltage borne by each power switch is the sum of the output voltage Vo and the input direct current voltage Vin, namely Vo + Vin, so that the withstand voltage of each power switch can be reduced by the aid of the N +1 level cuk direct current-direct current converter, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is N × fs, so in this embodiment, the second inductor L2 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The alternating current-direct current conversion circuit further comprises a first control circuit, and the first control circuit is used for controlling the working state of the N +1 level cuk direct current-direct current converter so as to carry out power factor correction. The first control circuit of the first kind in the eleventh embodiment is similar to the first control circuit of the tenth embodiment, except that: the PWM generating module 44 has different structures and is configured to control the on/off states of the N first power switches S1 to SN and the N second power switches M1 to MN. In this embodiment, the PWM generating module 44 receives the first duty ratio signal D, and is configured to turn on the q-th first power switch Sq q times in one switching period, q is not greater than N, the turn-on time of each turn-on of the N first power switches S1-SN is the same, and the turn-on time of each turn of each first power switch is controlled according to the first duty ratio signal D; in one switching period, the Nth first power switch SN is turned off for N times, and the turn-off time of each time is equal; optionally, the turn-on time of each of the first power switches S1 to SN is controlled by a clock signal. The PWM generating module 44 is further configured to control the second power switches M1-MN, and control the nth second power switch MN and the nth first power switch Sn to be complementarily turned on, where N is not greater than N. The inductor current sampling signal in the first control circuit is a sampling signal of a current flowing through the second inductor L2. The second type of first control circuit in the eleventh embodiment is similar to the second type of first control circuit in the tenth embodiment, and details are not repeated here.

Fig. 22 is a circuit diagram illustrating a twelfth embodiment of a first DC-DC conversion module according to the present invention; the first DC-DC conversion module comprises a four-level sepic DC-DC converter, the four-level sepic DC-DC converter comprises first power switches S1-S3, second power switches M1-M3, flying capacitors C1-C2, a first inductor L1, a second inductor L2 and a first capacitor C1, one end of the first inductor L1 is coupled to the input high potential end C of the first DC-DC conversion module for receiving the input DC voltage Vin, the other end of the first inductor L1 is coupled to one end of the first capacitor C1, the other end of the first capacitor C1 is coupled to one end of the second inductor L2, the other end of the second inductor L2 is grounded, the first power switches S1-S3 are sequentially connected in series between the common end of the first inductor L1 and the first capacitor C1 and the ground potential to form a first intermediate node 1 and a2 a, the second power switches M1-M3 are sequentially connected in series between a common terminal of the second inductor L2 and the first capacitor C1 and an output high potential terminal d of the first DC-DC conversion module to form second intermediate nodes b1 and b2, the flying capacitor C1 is coupled between a first intermediate node a1 and the second intermediate node b1, the flying capacitor C2 is coupled between the first intermediate node a2 and the second intermediate node b2, an input low potential terminal of the first DC-DC conversion module is a ground potential terminal, and an output low potential terminal of the first DC-DC conversion module is a ground potential terminal. Optionally, the four-level sepic DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and a ground potential.

Fig. 23 is a waveform diagram illustrating operations of a twelfth embodiment of the first DC-DC conversion module of the present invention, where the control signals G1-G3 are respectively used to drive the power switches S1-S3, and the control signals G1-G3 are respectively used to drive the second power switches M1-M3. At t₀-t₁In the interval, G2, G3 and G1 are high, the first power switches S2 and S3 and the second power switch M1 are turned on, and the current in the second inductor L2 is increased; at t₁-t₂In the interval, g1, g2 and g3 are high level, the second power switches M1, M2 and M3 are turned on, and the current on the second inductor L2 is reduced; at t₂-t₃In the interval, G3, G1 and G2 are high, the first power switch S3 and the second power switches M1 and M2 are turned on, and the current on the second inductor L2 is increased; at t₃-t₄In the interval, g1, g2 and g3 are high level, the second power switches M1, M2 and M3 are turned on, and the current on the second inductor L2 is reduced; at t₄-t₅In the interval, the G1, the G2 and the G3 are in a high level, the first power switches S1, S2 and S3 are turned on, and the current on the second inductor L2 is increased; at t₅-t₆In the interval, g1, g2 and g3 are high level, the second power switches M1, M2 and M3 are turned on, the current on the second inductor L2 is reduced, and t is₀-t₆Is one switching cycle. Wherein, the interval t₀-t₁，t₂-t₃And t₄-t₅Equal, interval t₁-t₂，t₃-t₄，t₅-t₆Are equal.

As seen in fig. 23, the first power switch S1 and the second power switch M1 are complementarily conductive, the first power switch S2 and the second power switch M2 are complementarily conductive, and the first power switch S3 and the second power switch M3 are complementarily conductive. The first power switch S1 is turned on once in one switching period, the first power switch S2 is turned on twice in one switching period, the first power switch S3 is turned on three times in one switching period, and the three first power switches S1-S3 are turned on for the same time each time. In one switching cycle, the first power switch S3 is turned off 3 times, and the turn-off time of each time is equal. Moreover, at any time when the four-level sepic dc-dc converter works, three power switches are turned on simultaneously, that is, the voltage borne by each power switch is 1/3 which is the sum of the output voltage Vo and the input dc voltage Vin, that is, 1/3 (Vo + Vin), whereas in the conventional sepic converter, the voltage borne by each power switch is the sum of the output voltage Vo and the input dc voltage Vin, that is, Vo + Vin, so that the four-level sepic dc-dc converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 3 × fs, so in this embodiment, the second inductor L2 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

In this embodiment, the ac-dc conversion circuit further includes a first control circuit, and the first control circuit controls the operating state of the four-level sepic dc-dc converter in two control manners to perform power factor correction. The two kinds of first control circuits in this embodiment are similar to the two kinds of first control circuits in the tenth embodiment, and are not described herein again.

In a twelfth embodiment, the first DC-DC conversion module is a 4-level sepic DC-DC converter, and in other embodiments, the first DC-DC conversion module may be a sepic DC-DC converter with any level, as shown in fig. 24, which provides a schematic circuit diagram of a thirteenth embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC conversion module is an N +1 level sepic DC-DC converter, and N is larger than 1.

The N +1 level sepic DC-DC converter comprises N first power switches S1 to SN, N second power switches M1 to MN, N-1 flying capacitors C1 to CN-1, a first inductor L1, a second inductor L2 and a first capacitor C1, one end of the first inductor L1 is coupled to the input high potential end C of the first DC-DC conversion module for receiving the input DC voltage Vin, the other end of the first inductor L1 is coupled to one end of the first capacitor C1, the other end of the first capacitor C1 is coupled to one end of the second inductor L2, the other end of the second inductor L2 is grounded, the N first power switches S1 to SN are sequentially connected in series between the common end of the first inductor L1 and the first capacitor C1 and the ground potential to form N-1 first intermediate nodes a1 to aN-1, and the N second power switches S1 to MN 2 are sequentially connected in series between the second inductor L1 and the second capacitor L638 in series A common terminal and an output high potential terminal d of the first DC-DC conversion module to form N-1 second intermediate nodes b 1-bN-1, the mth flying capacitor Cm being coupled between the mth first intermediate node am and the mth second intermediate node bm, m being not greater than N-1. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end. Optionally, the N +1 level sepic DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and the ground potential.

When the N +1 level sepic DC-DC converter works, the nth second power switch Mn and the nth first power switch Sn are conducted in a complementary mode, and N is not larger than N. The nth first power switch Sn is conducted N times in one switching period, and the conducting time of each conduction of the N first power switches S1-SN is the same. In a switching period, the nth first power switch SN is turned off N times, and the turn-off time of each time is equal. The N power switches are conducted simultaneously at any time when the N +1 level sepic DC-DC converter works, the voltage borne by each power switch is 1/N (1/N) of the sum of the output voltage Vo and the input DC voltage Vin, namely, 1/N (Vo + Vin), in the traditional sepic converter, the voltage borne by each power switch is the sum of the output voltage Vo and the input DC voltage Vin, namely, Vo + Vin, therefore, the N +1 level sepic DC-DC converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is N × fs, so in this embodiment, the second inductor L2 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The alternating current-direct current conversion circuit further comprises a first control circuit, and the first control circuit is used for controlling the working state of the N +1 level sepic direct current-direct current converter so as to carry out power factor correction. The first control circuit controls the working state of the multi-level DC-DC converter in two control modes to carry out power factor correction. The two kinds of first control circuits in this embodiment are similar to the two kinds of first control circuits in the eleventh embodiment, and are not described herein again.

FIG. 25 is a circuit diagram of a fourteenth embodiment of a first DC-DC converter module according to the invention; the first DC-DC conversion module comprises a four-level zeta DC-DC converter, the four-level zeta DC-DC converter comprises first power switches S1-S3, second power switches M1-M3, flying capacitors C1-C2, a first inductor L1, a second inductor L2, and a first capacitor C1, the first power switches S1-S3 are sequentially connected in series between an input high potential end C of the first DC-DC conversion module and a first node o to form a first intermediate node a1 and a2, one end of the first inductor L1 is coupled to the first node o, the other end of the first inductor L1 is grounded, one end of the first capacitor C1 is coupled to the first node o, the other end of the first capacitor C1 is coupled to a second inductor L2, and the other end of the second inductor L2 is coupled to an output high potential end d of the first DC-DC conversion module, the second power switches M1-M3 are sequentially connected in series between a ground potential and a common terminal of the second inductor L2 and the first capacitor C1 to form second intermediate nodes b1 and b2, the flying capacitor C1 is coupled between a first intermediate node a1 and the second intermediate node b1, and the flying capacitor C2 is coupled between a first intermediate node a2 and a second intermediate node b2, wherein the first node o is the common terminal of the first inductor L1 and the first capacitor C1. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end. Optionally, the four-level zeta DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and a ground potential.

Fig. 26 is a waveform diagram illustrating an operation of a fourteenth embodiment of the first DC-DC conversion module of the present invention, in which control signals G1-G3 are respectively used to drive power switches S1-S3, and control signals G1-G3 are respectively used to drive second power switches M1-M3. At t₀-t₁In the interval, the G1, the G2 and the G3 are in a high level, the first power switches S1, S2 and S3 are turned on, and the current on the second inductor L2 is increased; at t₁-t₂In the interval, g1, g2 and g3 are high level, the second power switches M1, M2 and M3 are turned on, and the current on the second inductor L2 is reduced; at t_2-t₃In the interval, G2, G3 and G1 are high, the first power switches S2 and S3 and the second power switch M1 are turned on, and the current in the second inductor L2 is increased; at t₃-t₄In the interval, g1, g2 and g3 are high level, the second power switches M1, M2 and M3 are turned on, and the current on the second inductor L2 is reduced; at t₄-t₅In the interval, G3, G1 and G2 are high, the first power switch S3 and the second power switches M1 and M2 are turned on, and the current on the second inductor L2 is increased; at t₅-t₆In the interval, g1, g2 and g3 are high level, the second power switches M1, M2 and M3 are turned on, the current on the second inductor L2 is reduced, and t is₀-t₆Is one switching cycle. Wherein, the interval t₀-t₁，t₂-t₃And t₄-t₅Equal, interval t₁-t₂，t₃-t₄，t₅-t₆Are equal.

As seen from fig. 26, the first power switch S1 is turned on once in one switching period, the first power switch S2 is turned on twice in one switching period, the first power switch S3 is turned on three times in one switching period, and the three first power switches S1 to SN are turned on at the same time. In one switching cycle, the first power switch S3 is turned off 3 times, and the turn-off time of each time is equal. The first power switch S1 and the second power switch M1 are complementarily conductive, the first power switch S2 and the second power switch M2 are complementarily conductive, and the first power switch S3 and the second power switch M3 are complementarily conductive. Moreover, at any time when the four-level zeta dc-dc converter operates, three power switches are turned on simultaneously, and the voltage borne by each power switch is 1/3, namely 1/3 (Vo + Vin), of the sum of the output voltage Vo and the input dc voltage Vin, whereas in the conventional zeta converter, the voltage borne by each power switch is Vo and the sum of the input dc voltage Vin, namely Vo + Vin, so that the four-level zeta dc-dc converter can reduce the withstand voltage of each power switch, and each power switch can use a low-withstand-voltage-level switching device. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 3 × fs, so in this embodiment, the second inductor L2 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

In this embodiment, the ac-dc conversion circuit further includes a first control circuit, and the first control circuit controls the operating state of the four-level zeta dc-dc converter in two control modes to perform power factor correction. The two kinds of first control circuits in this embodiment are similar to the two kinds of first control circuits in the tenth embodiment, and are not described herein again.

In a fourteenth embodiment, the first DC-DC conversion module is a 4-level zeta DC-DC converter, and in other embodiments, the first DC-DC conversion module may be a zeta DC-DC converter with any level, as shown in fig. 27, which provides a schematic circuit diagram of a fifteenth embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC conversion module is an N +1 level zeta direct current-direct current converter, and N is larger than 1.

The N +1 level zeta DC-DC converter comprises N first power switches S1-SN, N second power switches M1-MN, N-1 flying capacitors C1-CN-1, a first inductor L1, a second inductor L2 and a first capacitor C1, wherein the N first power switches S1-SN are sequentially connected in series between aN input high potential end C of the first DC-DC conversion module and a first node o to form N-1 first intermediate nodes a 1-aN-1, one end of the first inductor L1 is coupled to the first node o, the other end of the first inductor L1 is grounded, one end of the first capacitor C1 is coupled to the first node o, the other end of the first capacitor C1 is coupled to the second inductor L2, and the other end of the second inductor L2 is coupled to aN output high potential end d of the first DC-DC conversion module, the N second power switches M1-MN are sequentially connected in series between a ground potential and a common terminal of the second inductor L2 and the first capacitor c1 to form N-1 second intermediate nodes b 1-bN-1, the mth flying capacitor Cm is coupled between the mth first intermediate node am and the mth second intermediate node bm, wherein the first node o is a common terminal of the first inductor L1 and the first capacitor c1, and M is not greater than N-1. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end. Optionally, the N +1 level zeta DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and a ground potential.

When the N +1 level zeta direct current-direct current converter works, the nth second power switch Mn and the nth first power switch Sn are conducted in a complementary mode, and N is not larger than N. The nth first power switch Sn is conducted N times in one switching period, and the conducting time of each conduction of the N first power switches S1-SN is the same. In a switching period, the nth first power switch SN is turned off N times, and the turn-off time of each time is equal. In the conventional zeta converter, the voltage borne by each power switch is the sum of the output voltage Vo and the input direct-current voltage Vin, namely Vo + Vin, so that the N +1 level zeta direct-current converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is N × fs, so in this embodiment, the second inductor L2 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The alternating current-direct current conversion circuit further comprises a first control circuit, and the first control circuit is used for controlling the working state of the N +1 level zeta direct current-direct current converter so as to carry out power factor correction. The first control circuit controls the working state of the multi-level DC-DC converter in two control modes to carry out power factor correction. The two kinds of first control circuits in this embodiment are similar to the two kinds of first control circuits in the eleventh embodiment, and are not described herein again.

Fig. 28 is a circuit diagram illustrating a sixteenth embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC conversion module comprises a four-level half-bridge DC-DC converter, the four-level half-bridge DC-DC converter comprises 6 switch capacitor units and a first inductor L1, each switch capacitor unit comprises a first power switch Si, a second power switch Mi and a first capacitor Ci, the first power switch Si and the second power switch Mi are sequentially connected in series and then connected with the first capacitor Ci in parallel, i is 1-6, a first intermediate node a1 is coupled with an input high potential end c of the first DC-DC conversion module and used for connecting with the input DC voltage Vin, a 6 th second intermediate node b6 is grounded, an mth second intermediate node bm is coupled with an m +1 th first intermediate node am +1, one end of the first inductor L1 is coupled with a3 rd second intermediate node b3, and the other end of the first inductor L1 is coupled with an output high potential end d of the first DC-DC conversion module, the first intermediate node ai is a common terminal of the first power switch Si and the second power switch Mi, the second intermediate node bi is a common terminal of the first capacitor Ci and the second power switch Mi, i is 1-6, m is greater than 1 and m is less than 6. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end. Optionally, the four-level half-bridge DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and ground potential.

Fig. 29 is a waveform diagram illustrating sixteen working waveforms of the first DC-DC conversion module according to the embodiment of the present invention, wherein the control signals G1-G6 are respectively used for driving the first power switches S1-S6, and the control signals G1-G6 are respectively used for driving the second power switches M1-M6. At t₀-t₁In the interval, the G1, G2 and G3 are at a high level, the first power switch S1, S2 and the second power switch M3 are turned on, and the inductor current is increased; at t₁-t₂In the interval, g4, g5 and g6 are high level, the second power switches M4, M5 and M6 are turned on, and the inductor current is reduced; at t₂-t₃In the interval, G1, G3 and G2 are at high level, the first power switches S1 and S3 and the second power switch M2 are turned on, and the inductor current increases; at t₃-t₄In the interval, g4, g5 and g6 are high level, the second power switches M4, M5 and M6 are turned on, and the inductor current is reduced; at t₄-t₅In the interval, G2, G3 and G1 are high, the first power switches S2 and S3 and the second power switch M1 are turned on, and the inductor current increases; at t₅-t₆In the interval, g4, g5 and g6 are high level, the second power switches M4, M5 and M6 are turned on, and the inductor current is reduced; at t₆-t₇In the interval, the G4, G5 and G6 are high level, the first power switch S4 and the second power switches M5 and M6 are turned on, and the inductor current is increased; at t₇-t₈In the interval, the g4, g5 and g6 are high level, the second power switches M4, M5 and M6 are conducted, and the inductor current is reduced; at t₈-t₉In the interval, the G5, G4 and G6 are high level, the first power switch S5 and the second power switches M4 and M6 are turned on, and the inductor current is increased; at t₉-t₁₀In the interval, the g4, g5 and g6 are high level, the second power switches M4, M5 and M6 are conducted, and the inductor current is reduced; at t₁₀-t₁₁Intervals, the G6, G4 and G5 being high level, the first powerThe switch S6 and the second power switches M4 and M5 are turned on, and the inductor current increases; at t₁₁-t₁₂In the interval, the g4, g5 and g6 are high level, the second power switches M4, M5 and M6 are conducted, the inductive current is reduced, and t₀-t₁₂Is one switching cycle. Wherein the interval t₀-t₁,t₂-t₃,t₄-t₅,t₆-t₇,t₈-t₉And t₁₀-t₁₁Equal, interval t₁-t₂，t₃-t₄，t₅-t₆，t₇-t₈，t₉-t₁₀And t₁₁-t₁₂Are equal.

As can be seen from fig. 29, at any time when the four-level half-bridge dc-dc converter operates, three switched capacitor units operate, and three power switches are turned on simultaneously, each power switch is subjected to 1/3 of the input dc voltage Vin, that is, 1/3 × Vin, whereas in the conventional half-bridge converter, each power switch is subjected to the input dc voltage Vin, so that the four-level half-bridge dc-dc converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 6 × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

In this embodiment, the ac-dc conversion circuit further includes a first control circuit, and the first control circuit controls the operating state of the four-level half-bridge dc-dc converter in two control modes to perform power factor correction. The first control circuits of the two control modes in this embodiment are similar to the first control circuit in the tenth embodiment, and are not described herein again.

Sixteenth embodiment, the first DC-DC conversion module is a 4-level half-bridge DC-DC converter, in other embodiments, the first DC-DC conversion module may be a half-bridge DC-DC converter with any level, as shown in fig. 30, which shows a schematic circuit diagram of a seventeenth embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC conversion module is an N +1 level half-bridge DC-DC converter, and N is greater than 1.

The N +1 level half-bridge DC-DC converter comprises 2N switched capacitor units and a first inductor L1, each switched capacitor unit comprises a first power switch Si, a second power switch Mi and a first capacitor Ci, the first power switch Si and the second power switch Mi are sequentially connected in series and then connected in parallel with the first capacitor Ci, i is 1-2N, a first intermediate node a1 is coupled to an input high potential end c of the first DC-DC conversion module and is used for receiving the input DC voltage Vin, a second 2N intermediate node b2N is grounded, an mth second intermediate node bm is coupled to an m +1 th first intermediate node am +1, one end of the first inductor L1 is coupled to an nth second intermediate node bN, and the other end of the first inductor L1 is coupled to an output high potential end d of the first DC-DC conversion module, the first intermediate node ai is a common terminal of the first power switch Si and the second power switch Mi, the second intermediate node bi is a common terminal of the first capacitor Ci and the second power switch Mi, i is 1-2N, m is greater than 1 and m is less than 2N. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end. Optionally, the N +1 level half-bridge DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and ground potential.

The N +1 level half-bridge DC-DC converter has the advantages that at any time when the N +1 level half-bridge DC-DC converter works, the N switch capacitor units work, the N power switches are simultaneously conducted, and the voltage borne by each power switch is 1/N of the input DC voltage Vin, namely 1/N Vin. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 2N × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The AC-DC conversion circuit further comprises a first control circuit for controlling the working state of the N +1 level half-bridge DC-DC converter to carry out power factor correction. The first control circuit controls the working state of the multi-level DC-DC converter in two control modes to carry out power factor correction. The two kinds of first control circuits in this embodiment are similar to the two kinds of first control circuits in the eleventh embodiment, and are not described herein again.

Fig. 31 is a circuit diagram illustrating an eighteen embodiment of a first DC-DC conversion module according to the present invention; the first DC-DC conversion module comprises a four-level full-bridge DC-DC converter, the four-level full-bridge DC-DC converter comprises 6 switched capacitor units and a first inductor L1, each switched capacitor unit comprises four power switches and a first capacitor, two power switches S1i and M1i are connected in series to form a first series structure, another two power switches S2i and M2i are connected in series to form a second series structure, the first capacitor C1, the first series structure and the second series structure are connected in parallel in sequence, a first intermediate node a1 is coupled to an input high potential end C of the first DC-DC conversion module for receiving the input DC voltage Vin, a 6 th second intermediate node b6 is grounded, an M th second intermediate node bm is coupled to an M +1 th first intermediate node am +1, one end of the first inductor L1 is coupled to a3 rd second intermediate node b3, the other end of the first inductor L1 is coupled to an output high potential end d of the first DC-DC conversion module, wherein the first intermediate node ai is a common end of two power switches S1i and M1i in the first series structure, and the second intermediate node bi is a common end of two power switches S2i and M2i in the second series structure, where i is 1-6, M is greater than 1 and M is less than 6. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end. Optionally, the four-level full-bridge DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and the ground potential.

Fig. 32 is a waveform diagram illustrating operations of eighteen embodiments of the first DC-DC conversion module of the present invention, wherein the control signals G1-G6 are respectively used for driving the first power switches S1-S6, and the control signals G1-G6 are respectively used for driving the second power switches M1-M6. Wherein t is₀-t₁₂Is one switching period, interval t₀-t₁,t₂-t₃,t₄-t₅,t₆-t₇,t₈-t₉And t₁₀-t₁₁Equal, interval t₁-t₂，t₃-t₄，t₅-t₆，t₇-t₈，t₉-t₁₀And t₁₁-t₁₂Are equal.

As can be seen from fig. 32, at any time when the four-level full-bridge dc-dc converter operates, the power switches in 3 switched capacitor units are turned on, and each switched capacitor unit is turned on in one of the first series connection structure and the second series connection structure, so that the voltage borne by each switched capacitor unit is 1/3 of the input dc voltage Vin, that is, 1/3 × Vin, whereas in the conventional full-bridge converter, the voltage borne by each switched capacitor unit is the input dc voltage Vin, so that the withstand voltage of the power switch in each switched capacitor unit is correspondingly reduced, and thus, the four-level full-bridge dc-dc converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 6 × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

In this embodiment, the ac-dc conversion circuit further includes a first control circuit, and the first control circuit controls the operating state of the four-level full-bridge dc-dc converter in two control modes to perform power factor correction. The two kinds of first control circuits in this embodiment are similar to the two kinds of first control circuits in the tenth embodiment, and are not described herein again.

Eighteen embodiments of the present invention provide that the first DC-DC conversion module is a 4-level full-bridge DC-DC converter, and in other embodiments, the first DC-DC conversion module may be a full-bridge DC-DC converter with any level, as shown in fig. 33, which provides a circuit schematic diagram of nineteenth embodiment of the first DC-DC conversion module according to the present invention; the first DC-DC conversion module is an N +1 level full-bridge DC-DC converter, and N is greater than 1.

The N +1 level full-bridge DC-DC converter comprises 2N switched capacitor units and a first inductor L1, each switched capacitor unit comprises four power switches S1i, M1i, S2i, M2i and a first capacitor Ci, i is 1-2N, two power switches S1i and M1i are connected in series to form a first series structure, the other two power switches S2i and M2i are connected in series to form a second series structure, the first capacitor C1, the first series structure and the second series structure are sequentially connected in parallel, a first intermediate node a1 is coupled to an input high potential end C of the first DC-DC conversion module and used for receiving the input DC voltage Vin, a second intermediate node b2N 2N is grounded, the second intermediate node bm is coupled to a first intermediate node M +1, one end of the first inductor L1 is coupled to a second intermediate node bN +1, the other end of the first inductor L1 is coupled to an output high potential end d of the first DC-DC conversion module, wherein the first intermediate node ai is a common end of two power switches S1i and M1i in the first series structure, and the second intermediate node bi is a common end of two power switches S2i and M2i in the second series structure, where i is 1-2N, M is greater than 1 and M is less than 2N. The input low potential end of the first DC-DC conversion module is a ground potential end, and the output low potential end of the first DC-DC conversion module is a ground potential end. Optionally, the N +1 level full-bridge DC-DC converter further includes an output capacitor Co coupled between the output high potential terminal d of the first DC-DC conversion module and the ground potential.

At any time when the N +1 level full-bridge direct current-direct current converter works, power switches in 3 switch capacitor units are conducted, one power switch is conducted in a first series structure and a second series structure in each switch capacitor unit, the voltage borne by each switch capacitor unit is 1/N (1/N Vin) of the input direct current voltage Vin, and in the traditional full-bridge converter, the voltage borne by each switch capacitor unit is the input direct current voltage Vin, so that the withstand voltage of the power switch in each switch capacitor unit is correspondingly reduced, and therefore the N +1 level full-bridge direct current-direct current converter can reduce the withstand voltage of each power switch, and each power switch can use a switching device with a low withstand voltage level. In addition, under the condition that the operating frequency of each power switch is fs, the equivalent switching frequency on the inductor current is 2N × fs, so in this embodiment, the first inductor L1 may select an inductor with a smaller inductance value, and the ripple of the output capacitor Co is smaller.

The alternating current-direct current conversion circuit further comprises a first control circuit, and the first control circuit is used for controlling the working state of the N +1 level full-bridge direct current-direct current converter so as to carry out power factor correction. The first control circuit controls the working state of the multi-level DC-DC converter in two control modes to carry out power factor correction. The two kinds of first control circuits in this embodiment are similar to the two kinds of first control circuits in the eleventh embodiment, and are not described herein again.

FIG. 34 is a second circuit block diagram of the first DC-DC conversion module of the present invention; the first DC-DC conversion module 2 comprises N first-type power converters 21-2N, input ends of the N first-type power converters 21-2N are connected in series between an input high potential end c of the first DC-DC conversion module and a ground potential, the first DC-DC conversion module is provided with N output ends which are respectively output ends of the N first-type power converters 21-2N, and output voltages Vo 1-VoN of the first DC-DC conversion module are obtained. When the first DC-DC conversion module 2 includes N first-type power converters 21 to 2N, the second DC-DC conversion module 3 is N isolation-type DC-DC converters with independent inputs, and the input ends of the N isolation-type DC-DC converters are respectively coupled to the output ends of the N first-type power converters 21 to 2N.

The first type of power converter is a non-isolated power converter. Optionally, the first type of power converter is one of a buck converter, a boost converter, a buck-boost converter, a cuk converter, a sepic converter, a zeta converter, a half bridge converter and a full bridge converter.

Each of the aforementioned power converters of the first type includes at least one first power switch and at least one second power switch, and in each of the power converters of the first type: all the first power switches are switched on and off at the same time, all the second power switches are switched on and off at the same time, and the first power switches and the second power switches are switched on complementarily. For example, the buck circuit has a first power switch and 1 second power switch, and the first power switch and the second power switch are complementarily conducted.

It should be noted that the N first type power converters may all be the same non-isolated power converter, for example, N buck converters, or may be a mixture of different types of non-isolated power converters, for example, a boost converter, a buck converter, and the like, which is not limited in the present invention.

When the first DC-DC conversion module 2 comprises N first-type power converters 21-2N to work, the withstand voltage born by each power switch is as follows: when the conventional first DC-DC conversion module 2 includes only one power converter of the first type to operate, each power switch is subjected to 1/N of withstand voltage, thereby reducing the withstand voltage of each power switch. At any time when the first DC-DC module 2 operates, at least N power switches are turned on at the same time, that is, at least one power switch in each of the N first-type power converters 21 to 2N is turned on, so that the voltage (withstand voltage) borne by each power switch is reduced.

In a second circuit block diagram, the ac-dc conversion circuit further includes N first control circuits, which are respectively used for controlling N first type power converters 21-2N operating states to perform power factor correction.

Each of the N first control circuits has two modes, the first control circuit is similar to the first control circuit in the first embodiment, the second control circuit is similar to the second control circuit in the first embodiment, and a specific first control circuit will be described with reference to the following twenty embodiments, but the present invention is not limited thereto.

Fig. 35 is a circuit schematic diagram of a first DC-DC conversion module twenty according to an embodiment of the invention; the first DC-DC conversion module comprises 3 buck converters 21-23, input ends of the 3 buck converters 21-23 are connected between an input high potential end c of the first DC-DC conversion module and a ground potential in series, the first DC-DC conversion module is provided with 3 output ends which are output ends of the 3 buck converters 21-23 respectively, and output voltages Vo 1-Vo 3 of the first DC-DC conversion module are obtained.

The first DC-DC conversion module 2 comprises 3 buck converters 21-23, and the withstand voltage born by each power switch during operation is as follows: when the conventional first DC-DC conversion module 2 includes only one buck converter to operate, each power switch is subjected to 1/3 withstanding voltage, thereby reducing the withstanding voltage of each power switch.

The alternating current-direct current conversion circuit further comprises 3 first control circuits which are respectively used for controlling the working states of the 3 buck converters 21-23 to correct the power factor.

In this embodiment, the structure of each of the three first control circuits has two modes, and the first control circuit is similar to the first control circuit in the first embodiment, except that: the PWM generation module 44 has a different structure to control the switching states of the power switches S1 and S2 (or S3 and S4 or S5 and S6). In this embodiment, the PWM generating module 44 includes: an on control circuit 441 and an off control circuit 442, the on control circuit 441 being used to turn on power on S1 (or S3 or S5). Optionally, the on time of the power switch S1 (or S3 or S5) is controlled by a clock signal. The turn-off control circuit 442 receives the first duty cycle signal D, and is configured to control a turn-off time of the power switch S1 (or S3 or S5) according to the first duty cycle signal D. The on-control circuit 441 and the off-control circuit 442 are further configured to control an operating state of the power switch S2 (or S4 or S6), the power switch S2 is complementarily turned on with the power switch S1, the power switch S4 is complementarily turned on with the power switch S3, and the power switch S6 is complementarily turned on with the power switch S5.

The second type of first control circuit is similar to the second type of first control circuit in the first embodiment, except that: the conduction control circuit 61 has a different structure for controlling the switching states of the power switches S1 and S2 (or S3 and S4 or S5 and S6). In the present embodiment, the first control circuit includes an on control circuit 61 and an off control circuit 62, the on control circuit 61 receives the inductor current IL, and generates an on trigger signal to control the power switch S1 (or S3 or S5) to be turned on when the inductor current crosses zero; the turn-off control circuit 62 receives the voltage sampling signal SVout and the first scaling factor K1 to generate an on-time signal Ton, and controls the turn-off time of the power switch S1 (or S3 or S5) according to the on-time signal Ton; the on-control circuit 441 and the off-control circuit 442 are further configured to control an operating state of the power switch S2 (or S4 or S6), the power switch S2 is complementarily turned on with the power switch S1, the power switch S4 is complementarily turned on with the power switch S3, and the power switch S6 is complementarily turned on with the power switch S5.

Further, the second DC-DC conversion module 3 according to the present invention is configured as an isolated DC-DC converter to perform electrical isolation, and optionally, the second DC-DC conversion module 3 is configured to implement an output voltage stabilizing function or an output constant current function, which is not limited in the present invention.

Preferably, the second DC-DC conversion module 3 comprises N power converters of the second type, said N being greater than 1. The second type of power converter is an isolated DC-DC converter for electrical isolation. The second type of power converter is one of a flyback converter, a forward converter, an isolated cuk converter, an isolated sepic converter, an isolated zeta converter, a PWM half-bridge converter, a PWM full-bridge converter, a half-bridge resonant converter and a full-bridge resonant converter.

Fig. 36 shows a first circuit block diagram of a second DC-DC conversion module of the present invention; the second DC-DC conversion module 3 comprises N second-type power converters 31-3N, when the first DC-DC conversion module 2 comprises a multi-level DC-DC converter, the input ends of the N second-type power converters 31-3N are connected in parallel to receive the output voltage Vo of the multi-level DC-DC converter, and the output ends of the N second-type power converters are independent or connected in series or in parallel. When the input ends of the N second-type power converters 31-3N in the first DC-DC conversion module 3 are connected in parallel, the output current of each second-type power converter is small, so that the circuit loss is small, the efficiency is improved, and the output power is enlarged. FIG. 37 is a circuit diagram of a first embodiment of the second DC-DC converter module of the present invention, the second DC-DC converter module 3 includes three half-bridge resonant converters 31-33, the input terminals of the three half-bridge resonant converters 31-33 are connected in parallel to receive the output voltage Vo of the multi-level DC-DC converter, and the output terminals of the three half-bridge resonant converters 31-33 are independent or connected in series or in parallel.

FIG. 38 is a second circuit block diagram of a second DC-DC conversion module of the present invention; the second DC-DC conversion module 3 comprises N second-type power converters 31-3N, when the first DC-DC conversion module 2 comprises N first-type power converters 21-2N, input ends of the N second-type power converters 31-3N are respectively and correspondingly coupled with output ends of the N first-type power converters 21-2N to respectively receive output voltages Vo 1-VoN of each first-type power converter 21-2N, and output ends of the N second-type power converters are independent or connected in series or in parallel. When the input ends of the N second-type power converters 31 to 3N in the first DC-DC conversion module 3 are respectively coupled to the output ends of the N first-type power converters 21 to 2N, the output current of each second-type power converter is small, so that the circuit loss is small, the efficiency is improved, and the output power is enlarged. FIG. 39 is a circuit diagram of a second embodiment of the second DC-DC conversion module according to the present invention, in which the second DC-DC conversion module 3 includes three half-bridge resonant converters 31-33, input terminals of the three half-bridge resonant converters 31-33 are respectively coupled to output terminals of the 3 first-type power converters 21-23 to respectively receive the output voltages Vo 1-Vo 3 of each first-type power converter 21-23, and output terminals of the three half-bridge resonant converters 31-33 are independent or connected in series or in parallel.

Further, the output terminals of the N second type power converters are coupled in a manner that depends on the type of the load to be driven, for example, when the ac-dc conversion circuit of the present invention is used to drive a plurality of loads, the output terminals of the N second type power converters are independent, and the output terminals of the N second type power converters output a driving voltage to drive N loads respectively; when the driving voltage required by the load is larger, the output ends of the N second type power converters are connected in series to generate larger driving voltage to drive the load; when the driving current required by the load is large, the output terminals of the N second type power converters are connected in parallel to generate a large driving current to drive the load, which is not limited by the present invention. Preferably, when the output ends of the N second-type power converters 31 to 3N are connected in series or in parallel, the operating states (i ═ 1 to N-1) of two adjacent second-type power converters 3i and 3i +1 are controlled in a phase-staggered manner, so as to reduce the output ripple.

And integrating N transformers in the N second type power converters into a single-magnetic-core N-phase integrated transformer by a magnetic integration technology so as to further reduce the volume and improve the power density of the circuit. As shown in fig. 40, 3 transformers 1 to 3 of the 3 half-bridge resonant converters 31 to 33 shown in fig. 39 are integrated into a single-core 3-phase integrated transformer by magnetic integration technology.

Further, the ac-DC conversion circuit further includes a second control circuit, configured to control operating states of the N second type power converters to control output signals of the second DC-DC conversion module, where the output signals of the second DC-DC conversion module are configured to be first output signals, and the first output signals may be output voltage signals or output current signals, so as to implement an output voltage stabilizing function or an output constant current function.

Although the embodiments have been described and illustrated separately, it will be apparent to those skilled in the art that some common techniques may be substituted and integrated between the embodiments, and reference may be made to one of the embodiments not explicitly described, or to another embodiment described.

While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.