阅读说明：本技术 直流变换器的控制方法及直流变换器 (Control method of direct current converter and direct current converter ) 是由 周翩 刘腾 娄德海 肖宏伟 张怡 于 2020-05-14 设计创作，主要内容包括：本发明实施例提供一种直流变换器的控制方法及直流变换器,所述直流变换器包括开关电路、采样电路以及控制器,所述控制方法包括：根据一输出参考信号和所述输出信号获取Burst周期的占空比；根据所述Burst周期的占空比、第一预设值和所述开关器件的开关周期获取第一开关次数和驱动使能时间；根据所述驱动使能时间和所述Burst周期的占空比获取Burst周期值；根据所述Burst周期值、所述第一开关次数和所述开关周期生成所述驱动信号。本发明的技术方案可以降低直流变换器的输出电压纹波。(The embodiment of the invention provides a control method of a direct current converter and the direct current converter, wherein the direct current converter comprises a switching circuit, a sampling circuit and a controller, and the control method comprises the following steps: acquiring the duty ratio of a Burst period according to an output reference signal and the output signal; acquiring a first switching frequency and a driving enabling time according to the duty ratio of the Burst period, a first preset value and the switching period of the switching device; acquiring a Burst period value according to the driving enabling time and the duty ratio of the Burst period; and generating the driving signal according to the Burst period value, the first switching times and the switching period. The technical scheme of the invention can reduce the output voltage ripple of the DC converter.)

1. A control method of a direct current converter comprises a switching circuit, a sampling circuit and a controller, wherein the sampling circuit is connected with an output end of the direct current converter and the controller and used for collecting an output signal of the output end and sending the output signal to the controller, and the controller is connected with the switching circuit and used for generating a driving signal according to the output signal to drive a switching device in the switching circuit to act, and the control method comprises the following steps:

acquiring the duty ratio of a Burst period according to an output reference signal and the output signal;

acquiring a first switching frequency and a driving enabling time according to the duty ratio of the Burst period, a first preset value and the switching period of the switching device;

acquiring a Burst period value according to the driving enabling time and the duty ratio of the Burst period;

and generating the driving signal according to the Burst period value, the first switching times and the switching period.

2. The control method according to claim 1, wherein the step of obtaining the driving enable time according to the duty ratio of the Burst period, the first preset value, and the switching period further comprises:

acquiring first time according to the duty ratio of the Burst period and the first preset value;

acquiring a first switching frequency contained in the first time according to the first time and the switching period;

and acquiring the driving enabling time according to the first switching times and the switching period.

3. The control method according to claim 2, wherein the step of obtaining the first switching times based on the first time and the switching period further comprises:

acquiring a second switching frequency corresponding to the switching period contained in the first time according to the first time and the switching period;

and rounding the second switching frequency to obtain the first switching frequency.

4. The control method according to claim 1, wherein the step of obtaining the driving signal according to the Burst period value, the first switching times and the switching period further comprises:

acquiring driving enabling time and driving forbidding time according to the Burst period value, the first switching times and the switching period;

generating the driving signal according to the driving enable time and the driving disable time.

5. The control method according to claim 1, wherein the first preset value is set according to one or more parameters of a ripple factor, an output current of the dc converter, an output voltage of the dc converter, an output power of the dc converter, a duty ratio of a load, and a duty ratio of the Burst period.

6. The control method according to claim 1, wherein the dc converter is a full bridge LLC resonant converter or a half bridge LLC resonant converter.

7. The control method according to claim 1, characterized by further comprising:

and adjusting the conducting time of the switching device corresponding to the positive interval and the negative interval of the first switching period in the drive enabling time period.

8. The control method of claim 1, wherein the output signal is an output voltage signal, an output current signal, or an output power signal.

9. A dc converter comprising a switching circuit, a sampling circuit, and a controller, wherein:

the sampling circuit is connected with the output end of the direct current converter and the controller and used for collecting an output signal of the output end and sending the output signal to the controller;

the controller is connected with the switch circuit and used for generating and sending a driving signal to drive a switch device in the switch circuit to act, wherein the controller is used for generating the driving signal according to the output signal, a first preset value and the switching period of the switch device.

10. The dc converter according to claim 9, wherein the dc converter is a full bridge LLC resonant converter or a half bridge LLC resonant converter.

11. The dc converter of claim 9, wherein the controller comprises:

the duty ratio acquisition unit is used for acquiring the duty ratio of a Burst period according to an output reference signal and the output signal;

the switching frequency and enabling time obtaining unit is used for obtaining a first switching frequency and driving enabling time according to the duty ratio of the Burst period, the first preset value and the switching period of the switching device;

the Burst period acquisition unit is used for acquiring a Burst period value according to the driving enabling time and the duty ratio of the Burst period;

and the driving signal generating unit is used for generating the driving signal according to the Burst period value, the first switching times and the switching period.

12. The dc converter according to claim 9, wherein the controller further comprises a driving signal adjusting unit, and the driving signal adjusting unit is configured to adjust the conduction time of the corresponding switching device in each of the positive interval and the negative interval of the first switching cycle in the driving enable time.

Technical Field

The invention relates to the technical field of power electronics, in particular to a control method of a direct current converter and the direct current converter.

Background

In the application fields of electric vehicle charging and the like, high requirements are placed on output voltage ripples. According to the requirements of the technical conditions of the non-vehicle-mounted conductive charger for the electric vehicle (NB/T33001-2018) in the energy industry standard of China, when the output current of the charger changes within the range of the maximum output current value, the ripple factor of the output voltage is not larger than 1%.

The LLC resonant converter has the advantages of high efficiency, high power density and the like due to the soft switching characteristic, and is widely applied to the field of direct current-direct current conversion.

During no-load or light-load, the LLC generally employs a Burst mode (Burst) control method. Burst control alternately enables pulses and disables pulses, so that the power supply intermittently supplies power to the load, thereby reducing output power and meeting the load requirement of no load or light load. The main factors affecting the ripple of the output voltage and the output current are the drive enable time, the drive disable time, the Burst period, the output capacitance value, and the load. Under the same circuit parameters and load conditions, the output ripple is mainly affected by the Burst period.

The digital control system is used for realizing Burst control, the Burst period is influenced by a control period, the digital controller judges whether to enable or disable the pulse in each control period, the time for sending and closing the pulse is integral multiple of the control period, and the Burst period is also integral multiple of the control period. When the control period is longer, the Burst period is also longer, and the output ripple is larger. The control period of the digital control chip is influenced by chip resources and the like, the digital control chip cannot be unlimitedly shortened to achieve the effect of analog control, and when the control frequency is limited and the output capacitance is small, the output ripple of the circuit under no-load and extremely light load is large.

Fig. 1 shows a basic form of an LLC resonant converter. Lr is resonance inductance, Cr is resonance capacitance, Lm is transformer excitation inductance, and n is transformer primary-secondary transformation ratio. The switch SW1, the switch SW2, the switch SW3, and the switch SW4 are switching elements. The LLC typically regulates the output by adjusting the switching element drive frequency, the drive signal being shown in fig. 2. S1 is the driving signal of switch SW1 and switch SW4, S2 is the driving signal of switch SW2 and switch SW3, Ts0 is the switching period, switch SW1 and switch SW3 are driven complementarily, switch SW2 and switch SW4 are driven complementarily, and the driving duty ratio of switch SW1, switch SW2, switch SW3 and switch SW4 is 50%. In Burst mode, pulses are alternately enabled and disabled. During the pulse enable period, the switch SW1, the switch SW2, the switch SW3, and the switch SW4 are each turned on and off at a 50% duty cycle. In the pulse inhibition period, the switch SW1, the switch SW2, the switch SW3, and the switch SW4 are all in the off state.

In the related art, one Burst period includes two portions of time, i.e., a drive enable time Ton0 (i.e., the time of an enable pulse) and a drive disable time Toff0 (i.e., the time of an disable pulse), and the drive enable time Ton0 and the drive disable time Toff0 are integer multiples of the control period Tctrl 0. The driving prohibition time Toff0 under heavy load is more than or equal to the control period Tctrl0, and the voltage in the turn-off time is reduced to exceed the lower limit value due to the overlong turn-off time; the drive enable time Ton0 under a light load is equal to or longer than the control period Tctrl0, and the on time is too long so that the voltage in the on time exceeds the upper limit value. If the control period Tctrl0 is longer, the Burst period is longer, which results in a larger output ripple, and the requirement of the load for the output ripple may not be satisfied.

On the other hand, under the same working condition, the smaller the Burst period value is, the smaller the output ripple is, but the larger the switching loss is. This is because the first or first few switches enabled by the Burst period pulse are turned on as non-ZVS (Zero Voltage Switch), the switching element turn-on loss increases. Under the same load condition, the smaller the Burst period value is, the more the non-ZVS switching-on times are, and the larger the switching loss is. Therefore, on the premise of meeting the ripple requirement, the value of the Burst period should be as large as possible so as to reduce the number of non-ZVS switching-on times and reduce the switching loss.

Burst control typically employs a Bang-Bang control algorithm, i.e., by comparing the measured value of the output signal to the magnitude of given upper and lower limits to enable or disable pulses. The output ripple and steady-state accuracy of Bang-Bang control are affected by sampling accuracy, sampling delay, control bandwidth, control delay and the like, and when the output requirement is high and the performance of a sensor or a controller is limited, the output may not meet the requirement.

In summary, how to reduce the output voltage ripple of the dc converter under light load is a technical problem that needs to be solved.

It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.

Disclosure of Invention

The present disclosure provides a method for controlling a dc converter and a dc converter, so as to reduce a voltage ripple of an output voltage of the dc converter at least to a certain extent.

According to a first aspect of the present invention, there is provided a control method for a dc converter, the dc converter includes a switching circuit, a sampling circuit and a controller, the sampling circuit is connected to an output terminal of the dc converter and the controller, and is configured to collect an output signal of the output terminal and send the output signal to the controller, and the controller is connected to the switching circuit, and is configured to generate a driving signal according to the output signal to drive a switching device in the switching circuit to operate, the control method includes: acquiring the duty ratio of a Burst period according to an output reference signal and the output signal; acquiring a first switching frequency and a driving enabling time according to the duty ratio of the Burst period, a first preset value and the switching period of the switching device; acquiring a Burst period value according to the driving enabling time and the duty ratio of the Burst period; and generating the driving signal according to the Burst period value, the first switching times and the switching period.

In some embodiments, the step of obtaining the driving enable time according to the duty ratio of the Burst period, the first preset value and the switching period further includes: acquiring first time according to the duty ratio of the Burst period and the first preset value; acquiring a first switching frequency contained in the first time according to the first time and the switching period; and acquiring the driving enabling time according to the first switching times and the switching period.

In some embodiments, the step of obtaining the first number of switching times according to the first time and the switching period further comprises: acquiring a second switching frequency corresponding to the switching period contained in the first time according to the first time and the switching period; and rounding the second switching frequency to obtain the first switching frequency.

In some embodiments, the step of obtaining the driving signal according to the Burst period value, the first switching times and the switching period further comprises: acquiring driving enabling time and driving forbidding time according to the Burst period value, the first switching times and the switching period; generating the driving signal according to the driving enable time and the driving disable time.

In some embodiments, the first preset value is set according to one or more parameters of a ripple factor, an output current of the dc converter, an output voltage of the dc converter, an output power of the dc converter, a duty cycle of a load, and a duty cycle of the Burst cycle.

In some embodiments, the dc converter is a full bridge LLC resonant converter or a half bridge LLC resonant converter.

In some embodiments, further comprising: and adjusting the conducting time of the switching device corresponding to the positive interval and the negative interval of the first switching period in the drive enabling time period.

In some embodiments, the output signal is an output voltage signal, an output current signal, or an output power signal.

According to a second aspect of the present invention, there is provided a dc converter comprising a switching circuit, a sampling circuit, and a controller, wherein: the sampling circuit is connected with the output end of the direct current converter and the controller and used for collecting an output signal of the output end and sending the output signal to the controller; the controller is connected with the switch circuit and used for generating and sending a driving signal to drive a switch device in the switch circuit to act, wherein the controller is used for generating the driving signal according to the output signal, a first preset value and the switching period of the switch device.

In some embodiments, the dc converter is a full bridge LLC resonant converter or a half bridge LLC resonant converter.

In some embodiments, the controller comprises: the duty ratio acquisition unit is used for acquiring the duty ratio of a Burst period according to an output reference signal and the output signal; the switching frequency and enabling time obtaining unit is used for obtaining a first switching frequency and driving enabling time according to the duty ratio of the Burst period, the first preset value and the switching period of the switching device; the Burst period acquisition unit is used for acquiring a Burst period value according to the driving enabling time and the duty ratio of the Burst period; and the driving signal generating unit is used for generating the driving signal according to the Burst period value, the first switching times and the switching period.

In some embodiments, the controller further includes a driving signal adjusting unit, and the driving signal adjusting unit is configured to adjust the on-time of the switching device corresponding to each of the positive interval and the negative interval of the first switching period in the driving enable time.

In the control method of the direct current converter and the direct current converter provided by the embodiment of the invention, the first preset value is preset, the output is subjected to closed-loop control, the duty ratio of the driving enabling time in the Burst period is adjusted, and the driving signal of the switching element is generated according to the duty ratio, so that the output voltage ripple can meet the load requirement.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.

Fig. 1 schematically shows a schematic diagram of a dc converter;

FIG. 2 schematically illustrates a timing diagram of driving signals of a switching circuit;

fig. 3 schematically shows a flow chart of a control method of the dc converter of an embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating the timing of the driving signals and the corresponding relationship between the excitation current and the resonant current of the switching circuit according to an embodiment of the present invention;

FIG. 5 is a schematic diagram showing the timing of the driving signals and the corresponding relationship between the excitation current and the resonant current of the switching circuit according to another embodiment of the present invention;

FIG. 6 is a schematic diagram showing the timing of the driving signals and the corresponding relationship between the excitation current and the resonant current of the switching circuit according to still another embodiment of the present invention;

fig. 7 schematically shows a flowchart of a control method of a dc converter according to still another embodiment of the present invention;

FIG. 8 is a diagram schematically illustrating the relationship between the driving signal timing and the output voltage of the switching circuit according to another embodiment of the present invention;

fig. 9 schematically shows a schematic diagram of a dc converter according to an embodiment of the present invention.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, devices, steps, and so forth. In other instances, well-known methods, devices, implementations or operations have not been shown or described in detail to avoid obscuring aspects of the invention.

The block diagrams shown in the figures are functional entities only and do not necessarily correspond to physically separate entities. I.e. these functional entities may be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor means and/or microcontroller means.

The flow charts shown in the drawings are merely illustrative and do not necessarily include all of the contents and operations/steps, nor do they necessarily have to be performed in the order described. For example, some operations/steps may be decomposed, and some operations/steps may be combined or partially combined, so that the actual execution sequence may be changed according to the actual situation.

In the related art, when the load is no-load or light-load, the LLC generally adopts an intermittent mode (Burst) control method to control the power supply to intermittently supply power to the load, and when the control period is longer, the Burst period is correspondingly longer, resulting in a larger output voltage ripple. Therefore, when the control frequency is limited, the output voltage ripple of the dc converter may be large, and may not meet the design requirement.

The embodiment of the invention provides a control method of a direct current converter and the direct current converter, which are used for reducing output voltage ripples of the direct current converter.

The embodiment of the invention provides a control method of a direct current converter, which comprises a switching circuit, a sampling circuit and a controller, wherein the sampling circuit is connected with an output end of the direct current converter and the controller and is used for collecting an output signal of the output end and sending the output signal to the controller, and the controller is connected with the switching circuit and is used for generating a driving signal according to the output signal and further driving a switching device in the switching circuit to act. As shown in fig. 3, the control method of the dc converter includes the steps of:

in step S402, a duty ratio D1 of the Burst period is obtained according to the output reference signal and the output signal.

In step S404, a first switching number Non1 and a driving enable time Ton2 are obtained according to the duty ratio D1 of the Burst period, the first preset value Tset and the switching period Ts of the switching device.

In step S406, a Burst period value Tburst1 is obtained according to the driving enable time Ton2 and the duty ratio D1 of the Burst period.

In step S408, a driving signal is generated according to the Burst period value Tburst1, the first switching number Non1 and the switching period Ts.

The light-load intermittent control method in the embodiment of the invention is suitable for frequency modulation control topology, such as full-bridge LLC or half-bridge LLC, and can reduce output voltage ripple. Specifically, the output is subjected to closed-loop control by presetting a first preset value, and the duty ratio of the driving enabling time in the Burst period is adjusted, so that the Burst period value is obtained, and finally the switching element driving signal is generated. The size of the Burst period value obtained according to the method is not limited by the control period, so that the output voltage ripple can meet the load requirement.

Specifically, when the LLC operates in the Burst mode, in each control period, the digital control system may obtain a Burst period value Tburst1 and a driving enable time Ton2 according to the first preset value Tset, the reference value of the output signal, the measured value of the output signal, and the switching period Ts during the pulse enable period, so as to generate the driving signal of the switching element.

In the embodiment of the invention, the switch circuit comprises a primary circuit, the primary circuit comprises four switch devices SW 1-SW 4 which are connected in parallel after being connected in series two by two, and the drive signals output by the controller are used for controlling the on and off of the four switch devices. The switching device may be an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), a GaN (gallium nitride) or SiC (silicon carbide) power device, but is not limited thereto. During the drive enable period, the switching devices all have an identical switching period Ts.

In the embodiment of the present invention, the output signal may be, but is not limited to, an output voltage signal, an output current signal, or an output power signal.

In this embodiment, the first preset value may be set according to one or more parameters of the ripple factor, the output current of the dc converter, the output voltage of the dc converter, the output power of the dc converter, the duty ratio of the load, and the duty ratio of the Burst period. Specifically, the first preset value Tset may be selected according to, but not limited to, the following method.

In one embodiment, the first preset value Tset may be set to a fixed constant, so as to satisfy the requirement of output ripple under various load conditions.

In another embodiment, the first preset value Tset may be set according to one or more of the current load output power, the output current, or the duty cycle of the load, or the duty cycle of the Burst period, so as to achieve better effects under different loads.

In step S402, a duty ratio D1 of the Burst period is obtained according to the command value (output reference signal) of the output signal and the measured feedback value (output signal) of the output signal, where D1 is a ratio of the drive enable time to the Burst period value in the Burst period. Specifically, the output reference signal and the output signal are subtracted to obtain an output error signal, and the output error signal is transmitted to an output controller, and the output controller outputs a duty ratio D1 of a Burst period.

In step S404, a first time Ton1 is obtained according to the duty ratio D1 of the Burst period and the first preset value Tset.

In one embodiment, the first time Ton1 may be a product of the first preset value Tset and the duty ratio D1 of the Burst period.

Then, the second switching frequency Non2 included in the first time Ton1 is obtained according to the first time Ton1 and the switching period Ts, and the second switching frequency Non2 is further rounded to obtain the first switching frequency Non 1.

Here, the rounding may be rounding up, rounding down, or rounding down.

Thereafter, the drive enable time Ton2 is acquired from the first switching number Non1 and the switching period Ts. Specifically, the drive enable time Ton2 is calculated by multiplying the switching period Ts by the first switching number Non1 in the drive enable period.

In step S406, an actual Burst period value Tburst1 is calculated from the drive enable time Ton2 and the duty ratio D1 of the Burst period.

In step S408, the driving prohibition time Toff1 may be obtained according to the Burst period value Tburst1, the first switching number Non1 and the switching period Ts, or the driving prohibition time Toff1 may be obtained by directly subtracting the Burst period value Tburst1 from the driving enabling time Ton 2; and then generates a driving signal according to the driving enable time Ton2 and the driving disable time Toff 1.

The calculation formula of the drive prohibition time Toff1 is: drive prohibition time Toff 1-Burst period value Tburst 1-first switching number Non 1-switching period Ts.

And updating the Burst period value Tburst1, the drive enabling time Ton2 and the number of switching on times (the first switching time Non1) in the drive enabling period after each Burst period is ended, and generating a drive signal of the switching element in the next Burst period. The number of switch-on times during the drive enable period refers to the number of times the switch SW1 (or the switch SW2, or the switch SW3, or the switch SW4) is turned on as shown in fig. 1. The on times of the switch SW1, the switch SW2, the switch SW3, and the switch SW4 in one switching period are the same.

In the embodiment of the present invention, further, the on-time of the switching device corresponding to each of the positive interval and the negative interval of the first switching cycle in the driving enable period may be adjusted, so as to reduce the switching loss.

During the drive enable period, if the conventional drive mode, i.e. 50% duty ratio of each of the positive and negative half cycles, is used, as shown in fig. 4, during the first several switching cycles in the drive enable period, the positive and negative half cycles of the resonant current ip are asymmetric due to the bias of the exciting current im, so that the positive half cycle or the negative half cycle ZVS of the first several switching cycles is lost, and the switching loss is increased.

The driving mode of the first switching period in the driving enabling period can be optimized, so that the exciting current im can reach positive and negative half-cycle symmetry as soon as possible, ZVS is favorably realized, and the total switching loss is reduced.

In one embodiment, as shown in fig. 5, during the first switching cycle of the drive enable period, the positive half cycle on time is 0.25Ts and the negative half cycle on time is 0.5 Ts. Thus, the on-time of the switches SW1 and SW4 corresponding to the positive interval is 0.25Ts, and the on-time of the switches SW2 and SW3 corresponding to the negative interval is 0.5Ts, so that the excitation current im can approximately reach the positive and negative half cycle balance after the first switching period is finished. The positive and negative half-cycle duty cycles in the remaining switching period are each 50%. Where Ts is the switching period.

In another embodiment, as shown in fig. 6, during the first switching cycle of the drive enable period, the positive half-cycle on-time is 0.33Ts, the negative half-cycle on-time is 0.67Ts, and the positive half-cycle on-time is about half of the negative half-cycle. Thus, the on-time of the switches SW1 and SW4 corresponding to the positive interval is 0.33Ts, and the on-time of the switches SW2 and SW3 corresponding to the negative interval is 0.67Ts, so that the exciting current im is approximately balanced in the positive and negative half cycles after the first switching period is finished. The positive and negative half-cycle duty cycles of the remaining switching cycle are each 50%. Where Ts is the switching period.

As shown in fig. 7, a method for controlling a dc converter according to an embodiment of the present invention includes the following steps:

in step S701, a first preset value is set.

And step S702, carrying out closed-loop control on the output signal to obtain the duty ratio of the Burst period.

And step S703, calculating first time according to the Burst cycle duty ratio and a first preset value.

Step S704, calculating a first switching frequency within the first time according to the first time and the switching period.

Step S705 calculates the drive enable time based on the first switching times and the switching period.

Step S706, calculating a Burst period value according to the driving enabling time and the Burst period duty ratio.

In step S707, a driving signal is generated according to the Burst period value, the first switching times and the switching period.

As shown in fig. 8, in the embodiment of the present invention, in the Burst operation mode, the Burst period value Tburst1 is 0.5Tctrl0, the duty ratio of the Burst period is about 0.5 in the steady state of the closed-loop control, and when the pulse enable time is equal to 0.5Tburst1, the output voltage ripple is about equal to one fourth of the Burst period value 2Tctrl0, which greatly reduces the output voltage ripple.

As shown in fig. 9, an embodiment of the present invention further provides a dc converter, which includes a switching circuit, a sampling circuit 901, and a controller 902, wherein: the sampling circuit 901 is connected with the output end of the dc converter and the controller 902, and is used for collecting the output signal of the output end and sending the output signal to the controller 902; the controller 902 is connected to the switching circuit, and is configured to generate and transmit a driving signal to drive the switching device in the switching circuit to operate. As shown in fig. 9, four switching devices constitute a switching device group 903, and the driving signal drives the switching device group 903 to operate. The controller 902 is configured to generate a driving signal according to the output signal, a first preset value, and a switching period of the switching device.

In the embodiment of the present invention, the dc converter may be a full-bridge LLC resonant converter or a half-bridge LLC resonant converter.

Wherein, the controller may include:

and the duty ratio acquisition unit can be used for acquiring the duty ratio of the Burst period according to the output reference signal and the output signal.

The switching times and enabling time acquiring unit may be configured to acquire the first switching times and the driving enabling time according to a duty ratio of the Burst period, a first preset value, and a switching period of the switching device.

And the Burst period acquisition unit can be used for acquiring a Burst period value according to the driving enabling time and the duty ratio of the Burst period.

And the driving signal generating unit can be used for generating a driving signal according to the Burst period value, the first switching times and the switching period.

Further, the controller may further include a driving signal adjusting unit for adjusting the turn-on time of the switching device corresponding to each of the positive interval and the negative interval of the first switching period within the driving enable time.

As shown in fig. 9, the switching circuit includes a primary circuit, the primary circuit includes four switching devices connected in parallel after being connected in series two by two, and the control signal is used to control the four switching devices to be turned on and off.

In the control method of the direct current converter and the direct current converter provided by the embodiment of the invention, the first preset value is preset, the output is subjected to closed-loop control, the duty ratio of the driving enabling time in the Burst period is adjusted, and the driving signal of the switching element is generated according to the duty ratio, so that the output voltage ripple can meet the load requirement.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.