阅读说明：本技术 一种两路输出反激式开关电路 (Two-way output flyback switching circuit ) 是由 张艺蒙 刘源 张玉明 孙乐嘉 宋庆文 汤晓燕 于 2021-07-09 设计创作，主要内容包括：本发明公开了一种两路输出反激式开关电路,包括：直流变压模块,用于在第一开关信号的控制下,通过多绕组变压器将输入电压转换为主路输出电压和辅路中间电压；还用于在第二开关信号和第三开关信号的控制下,通过buck电路将辅路中间电压转换为辅路输出电压；主路反馈与控制模块,用于对主路输出电压进行采样,得到第一采样信号；还用于基于第一采样信号,通过自身包含的第一驱动电路输出第一开关信号；辅路反馈与控制模块,用于对辅路输出电压进行采样,得到第二采样信号；还用于基于第二采样信号,通过自身包含的第二驱动电路输出第二开关信号和第三开关信号。本发明可减轻多输出隔离式变换器的交叉调整率的问题。(The invention discloses a flyback switching circuit with two paths of outputs, which comprises: the direct current transformation module is used for converting an input voltage into a main circuit output voltage and an auxiliary circuit intermediate voltage through the multi-winding transformer under the control of the first switching signal; the buck circuit is used for converting the auxiliary circuit intermediate voltage into an auxiliary circuit output voltage under the control of the second switching signal and the third switching signal; the main circuit feedback and control module is used for sampling the output voltage of the main circuit to obtain a first sampling signal; the first sampling circuit is used for outputting a first sampling signal according to a first sampling signal; the auxiliary circuit feedback and control module is used for sampling the output voltage of the auxiliary circuit to obtain a second sampling signal; and the second circuit is also used for outputting a second switching signal and a third switching signal through a second driving circuit contained in the second circuit based on the second sampling signal. The invention can reduce the problem of the cross regulation rate of the multi-output isolated converter.)

1. A two-way output flyback switch circuit is characterized by comprising:

the direct current transformation module is used for converting an input voltage into a main circuit output voltage and an auxiliary circuit intermediate voltage through a multi-winding transformer contained in the direct current transformation module under the control of a first switching signal; the auxiliary circuit is also used for converting the auxiliary circuit intermediate voltage into an auxiliary circuit output voltage through a buck circuit contained in the auxiliary circuit under the control of a second switching signal and a third switching signal; wherein the second switching signal and the third switching signal are a pair of inverted switching signals having a dead time;

the main circuit feedback and control module is used for sampling the output voltage of the main circuit to obtain a first sampling signal; the first sampling circuit is also used for generating a first switching signal through a first driving circuit contained in the first sampling circuit based on the first sampling signal;

the auxiliary circuit feedback and control module is used for sampling the auxiliary circuit output voltage to obtain a second sampling signal; and the second and third switching signals are generated by a second driving circuit contained in the second sampling circuit based on the second sampling signal.

2. The two-way output flyback switch circuit of claim 1, wherein the dc transformer module comprises: the multi-winding transformer, a first switching tube (M1), a main diode (D1), a secondary diode (D2), the buck circuit and a main filter capacitor (C1); wherein the content of the first and second substances,

the multi-winding transformer comprises a primary coil, a first secondary coil and a second secondary coil;

one end of the primary coil is connected with the input voltage, and the other end of the primary coil is connected with the drain electrode of the first switching tube (M1); the grid electrode of the first switch tube (M1) is connected with the first switch signal, and the source electrode is grounded;

the first secondary coil, one end connects the positive pole of the diode of the said main circuit (D1), another end is grounded; the cathode of the main circuit diode (D1) outputting the main circuit output voltage;

one end of the second secondary coil is connected with the anode of the auxiliary diode (D2), and the other end of the second secondary coil is grounded; the cathode of the auxiliary diode (D2) outputs the auxiliary intermediate voltage;

the input end of the buck circuit is connected with the auxiliary circuit intermediate voltage, and the output end of the buck circuit outputs the auxiliary circuit output voltage; the grid electrodes of two switching tubes in the buck circuit are respectively connected with the second switching signal and the third switching signal;

and one end of the main circuit filter capacitor (C1) is connected with the cathode of the main circuit diode (D1), and the other end of the main circuit filter capacitor is grounded.

3. The two-way output flyback switch circuit of claim 2, wherein the buck circuit comprises: the circuit comprises a second switching tube (M2), a third switching tube (M3), an inductor (L1) and an auxiliary circuit filter capacitor (C2); wherein the content of the first and second substances,

the grid electrode of the second switching tube (M2) is connected with the second switching signal, and the drain electrode of the second switching tube is connected with the auxiliary circuit intermediate voltage;

the grid electrode of the third switching tube (M3) is connected with the third switching signal, and the source electrode of the third switching tube is grounded;

the source electrode of the second switching tube (M2), the drain electrode of the third switching tube (M3) and one end of the inductor (L1) are connected together; the other end of the inductor (L1) is connected with one end of the auxiliary circuit filter capacitor (C2) and is used for outputting the auxiliary circuit output voltage; the other end of the auxiliary filter capacitor (C2) is grounded.

4. The two-way output flyback switching circuit of claim 1, wherein the main circuit feedback and control module comprises: the first sampling circuit, the optical coupler and the first driving circuit; wherein the content of the first and second substances,

the first sampling circuit is used for sampling the main circuit output voltage to obtain the first sampling signal;

the optical coupler is used for comparing the first sampling signal with the reference voltage of the optical coupler to generate a control signal;

the first driving circuit is configured to generate the first switching signal under the control of the control signal.

5. The two-way output flyback switch circuit of claim 1, wherein the auxiliary feedback and control module comprises: the second sampling circuit, the frequency compensation circuit, the PWM generator and the second driving circuit; wherein the content of the first and second substances,

the second sampling circuit is used for sampling the auxiliary circuit output voltage to obtain a second sampling signal;

the frequency compensation circuit is used for carrying out frequency compensation on the second sampling signal to obtain a second sampling signal with stable frequency response;

the PWM generator is used for comparing a triangular wave generated in the PWM generator with the second sampling signal with stable frequency response to generate a PWM square wave;

the second driving circuit is configured to generate the second switching signal and the third switching signal under the control of the PWM square wave.

6. The two-way output flyback switch circuit of claim 1, wherein the first driver circuit comprises: and the peak circuit mode is adopted.

7. The two-way output flyback switch circuit of claim 1, wherein the second driver circuit comprises: a dual output high side gate driver or a high and low side gate driver.

8. The two-way output flyback switching circuit of claim 5, wherein the frequency compensation circuit comprises: a type III compensation circuit.

Technical Field

The invention belongs to the technical field of switch circuits, and particularly relates to a flyback switch circuit with two output paths.

Background

In the fields of industrial control, consumer, medical electronics, mobile communication, etc., switching power supplies are widely used due to their high efficiency, small size, and low cost. With the development of the internet of things, the electronic equipment becomes more and more informationized, intelligent and complicated. This means that our power supply is more and more complicated, and because different systems and modules need power supplies of different levels, multiple power supplies are needed to supply power to the systems in one internet of things device. The traditional power supply solution is that an independent switch power supply is designed for supplying power to form a multi-output power supply system. Although such a power supply has the advantages of high reliability and high power supply accuracy, the disadvantages of high cost, large volume and heavy weight are also obvious. Meanwhile, the development period is long, and the product is not suitable for being quickly listed. Today, the market demand for power supplies is increasingly moving towards miniaturization, lightness, high efficiency and low cost.

For a multi-output power system, an isolated switching power supply is often used. The multi-output isolated switch power supply only needs to add one high-frequency transformer winding, a rear-stage rectifier diode and an LC filter circuit when one output is added, so that the cost of the multi-output power supply system is rapidly reduced, and the volume is greatly reduced.

However, there are many problems with the multi-output power supply system designed based on the addition of windings, and the most important problem is the cross regulation. Specifically, since the isolated multi-output power supply usually performs closed-loop feedback control only on the main output loop, when the load changes, the auxiliary output loop can only perform voltage stabilization control through the turn ratio of the transformer, and cannot perform accurate feedback control, so that the voltage of the auxiliary output loop changes greatly.

Disclosure of Invention

In order to solve the problem of cross regulation rate of a multi-output isolation type converter, the invention provides a two-path output flyback switching circuit.

The technical problem to be solved by the invention is realized by the following technical scheme:

a two-way output flyback switching circuit, comprising:

the direct current transformation module is used for converting an input voltage into a main circuit output voltage and an auxiliary circuit intermediate voltage through a multi-winding transformer contained in the direct current transformation module under the control of a first switching signal; the auxiliary circuit is also used for converting the auxiliary circuit intermediate voltage into an auxiliary circuit output voltage through a buck circuit contained in the auxiliary circuit under the control of a second switching signal and a third switching signal; wherein the second switching signal and the third switching signal are a pair of inverted switching signals having a dead time;

the main circuit feedback and control module is used for sampling the output voltage of the main circuit to obtain a first sampling signal; the first sampling circuit is also used for generating a first switching signal through a first driving circuit contained in the first sampling circuit based on the first sampling signal;

the auxiliary circuit feedback and control module is used for sampling the auxiliary circuit output voltage to obtain a second sampling signal; and the second and third switching signals are generated by a second driving circuit contained in the second sampling circuit based on the second sampling signal.

Optionally, the dc transformer module includes: the multi-winding transformer, the first switching tube M1, the main diode D1, the auxiliary diode D2, the buck circuit and the main filter capacitor C1; wherein the content of the first and second substances,

the multi-winding transformer comprises a primary coil, a first secondary coil and a second secondary coil;

one end of the primary coil is connected with the input voltage, and the other end of the primary coil is connected with the drain electrode of the first switching tube M1; the grid electrode of the first switching tube M1 is connected with the first switching signal, and the source electrode is grounded;

the first secondary coil has one end connected to the anode of the main diode D1 and the other end grounded; the cathode of the main circuit diode D1 outputs the main circuit output voltage;

one end of the second secondary coil is connected with the anode of the auxiliary diode D2, and the other end of the second secondary coil is grounded; the cathode of the auxiliary diode D2 outputs the auxiliary intermediate voltage;

the input end of the buck circuit is connected with the auxiliary circuit intermediate voltage, and the output end of the buck circuit outputs the auxiliary circuit output voltage; the grid electrodes of two switching tubes in the buck circuit are respectively connected with the second switching signal and the third switching signal;

one end of the main circuit filter capacitor C1 is connected to the cathode of the main circuit diode D1, and the other end is grounded.

Optionally, the buck circuit includes: the second switching tube M2, the third switching tube M3, the inductor L1 and the auxiliary filter capacitor C2; wherein the content of the first and second substances,

the grid electrode of the second switching tube M2 is connected with the second switching signal, and the drain electrode of the second switching tube M2 is connected with the auxiliary circuit intermediate voltage;

the grid electrode of the third switching tube M3 is connected with the third switching signal, and the source electrode is grounded;

the source electrode of the second switching tube M2, the drain electrode of the third switching tube M3 and one end of the inductor L1 are connected together; the other end of the inductor L1 is connected with one end of the auxiliary circuit filter capacitor C2 and used for outputting the auxiliary circuit output voltage; the other end of the auxiliary filter capacitor C2 is grounded.

Optionally, the master feedback and control module includes: the first sampling circuit, the optical coupler and the first driving circuit; wherein the content of the first and second substances,

the first sampling circuit is used for sampling the main circuit output voltage to obtain the first sampling signal;

the optical coupler is used for comparing the first sampling signal with the reference voltage of the optical coupler to generate a control signal;

the first driving circuit is configured to generate the first switching signal under the control of the control signal.

Optionally, the auxiliary feedback and control module includes: the second sampling circuit, the frequency compensation circuit, the PWM generator and the second driving circuit; wherein the content of the first and second substances,

the second sampling circuit is used for sampling the auxiliary circuit output voltage to obtain a second sampling signal;

the frequency compensation circuit is used for carrying out frequency compensation on the second sampling signal to obtain a second sampling signal with stable frequency response;

the PWM generator is used for comparing a triangular wave generated in the PWM generator with the second sampling signal with stable frequency response to generate a PWM square wave;

the second driving circuit is configured to generate the second switching signal and the third switching signal under the control of the PWM square wave.

Optionally, the first driving circuit includes: and the peak circuit mode is adopted.

Optionally, the second driving circuit includes: a dual output high side gate driver or a high and low side gate driver.

Optionally, the frequency compensation circuit includes: a type III compensation circuit.

In the two-path output flyback switching circuit provided by the invention, the main circuit feedback and control module samples the main circuit output voltage to generate a first switching signal to control the size of the main circuit output voltage; the auxiliary circuit feedback and control module samples the auxiliary circuit output voltage to generate a pair of opposite-phase switching signals to control the size of the auxiliary circuit output voltage output by the buck circuit; therefore, two paths of output of the switch circuit are independently sampled and fed back, the output voltage of the auxiliary circuit can be accurately fed back and controlled, and the problem of cross regulation rate is effectively solved. The input of the buck circuit is from the auxiliary circuit intermediate voltage controlled by the first switching signal, and the first switching signal is generated by the main circuit feedback and control module, so that the output voltage of the auxiliary circuit does not exceed the output voltage of the main circuit even if fluctuating.

In addition, compared with the method of setting a weighted feedback circuit or a voltage stabilizing circuit for multipath output to solve the problem of cross regulation rate in the prior art, the method does not need to set the weighted feedback circuit or the voltage stabilizing circuit, and can reduce the power consumption of the switch circuit.

The present invention will be described in further detail with reference to the accompanying drawings.

Drawings

Fig. 1 is a block diagram of a two-way output flyback switch circuit according to an embodiment of the present invention;

fig. 2 is a schematic circuit diagram of a dc voltage reduction module in the two-way output flyback switch circuit shown in fig. 1;

fig. 3 is a schematic circuit structure diagram of a two-way output flyback switch circuit according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.

In order to solve the problem of cross regulation rate of a multi-output isolated converter, the embodiment of the invention provides a flyback switching circuit with two output paths; referring to fig. 1, the two-way output flyback switching circuit includes: the device comprises a direct current transformation module, a main circuit feedback and control module and an auxiliary circuit feedback and control module.

The direct current transformation module is used for converting an input voltage VIN into a main circuit output voltage VOUT1 and an auxiliary circuit intermediate voltage through a multi-winding transformer contained in the direct current transformation module under the control of a first switching signal S1; the auxiliary circuit is also used for converting the auxiliary circuit intermediate voltage into an auxiliary circuit output voltage VOUT2 through a buck circuit contained in the auxiliary circuit under the control of the second switching signal S2 and the third switching signal S3; the second switching signal S2 and the third switching signal S3 are a pair of inverted switching signals having dead time.

It can be understood that the dc voltage transformation module includes three switching tubes; one switching tube is controlled by a first switching signal to be opened and closed and is recorded as a first switching tube M1, one switching tube is controlled by a second switching signal to be opened and closed and is recorded as a second switching tube M2, and the other switching tube is controlled by a third switching signal to be opened and closed and is recorded as a third switching tube M3.

The buck circuit is a voltage reduction circuit, and includes a pair of switching tubes, the gates of the two switching tubes are respectively connected to a pair of switching signals with dead time and opposite phases, and the two switching tubes are respectively a second switching tube M2 and a third switching tube M3.

The multi-winding transformer comprises a primary coil, a first secondary coil and a second secondary coil; the primary coil and the first secondary coil implement the conversion of the input voltage VIN to the main output voltage VOUT1, and the primary coil and the second secondary coil implement the conversion of the input voltage to the auxiliary intermediate voltage.

The main circuit feedback and control module is used for sampling a main circuit output voltage VOUT1 to obtain a first sampling signal; and is further configured to generate a first switching signal S1 through the self-contained first driving circuit based on the first sampling signal.

The auxiliary circuit feedback and control module is used for sampling an auxiliary circuit output voltage VOUT2 to obtain a second sampling signal; and is also used for outputting a second switching signal S2 and a third switching signal S3 through a second driving circuit included in itself based on the second sampling signal.

It can be understood that the main circuit feedback and control module and the auxiliary circuit feedback and control module both comprise sampling circuits, and the sampling circuits can be built by adopting resistance voltage division.

In addition, the first driving circuit and the second driving circuit can be built by adopting a driving chip and a peripheral circuit thereof.

In the flyback switching circuit with two output paths provided by the embodiment of the invention, the main circuit feedback and control module samples the output voltage of the main circuit to generate a first switching signal to control the output voltage of the main circuit; the auxiliary circuit feedback and control module samples the auxiliary circuit output voltage to generate a pair of opposite-phase switching signals to control the size of the auxiliary circuit output voltage output by the buck circuit; therefore, two paths of output of the switch circuit are independently sampled and fed back, the output voltage of the auxiliary circuit can be accurately fed back and controlled, and the problem of cross regulation rate is effectively solved. The input of the buck circuit is from the auxiliary circuit intermediate voltage controlled by the first switching signal, and the first switching signal is generated by the main circuit feedback and control module, so that the output voltage of the auxiliary circuit does not exceed the output voltage of the main circuit even if fluctuating.

In addition, compared with the method of setting a weighted feedback circuit or a voltage stabilizing circuit for each output of a multi-output switch circuit in the prior art to solve the problem of cross regulation rate, the embodiment of the invention does not need to set the weighted feedback circuit or the voltage stabilizing circuit, and can reduce the power consumption of the switch circuit.

In one embodiment, referring to fig. 2, the dc transformer module includes: the multi-winding transformer, the first switching tube M1, the main diode D1, the auxiliary diode D2 and the buck circuit.

One end A of the primary coil is connected with an input voltage VIN, and the other end B of the primary coil is connected with the drain electrode of the first switching tube M1; the gate of the first switch transistor M1 is connected to the first switching signal S1, and the source is grounded;

a first secondary coil, one end C of which is connected to the anode of the main diode D1, and the other end D of which is grounded; the cathode of main diode D1 outputs a main output voltage VOUT 1;

one end E of the second secondary coil is connected with the anode of the auxiliary diode D2, and the other end F of the second secondary coil is grounded; the cathode of the auxiliary diode D2 outputs an auxiliary intermediate voltage VMID;

the input end of the buck circuit is connected with the auxiliary circuit intermediate voltage VMID, and the output end of the buck circuit outputs an auxiliary circuit output voltage VOUT 2; the gates of the two switching tubes in the buck circuit are respectively connected with the second switching signal S2 and the third switching signal S3.

As shown in fig. 2, the buck circuit includes: a second switch tube M2, a third switch tube M3, an inductor L1 and an auxiliary filter capacitor C2. The grid of the second switch tube M2 is connected with a second switch signal S2, and the drain is connected with the auxiliary circuit intermediate voltage VMID; the grid of the third switching tube M3 is connected with a third switching signal S3, and the source is grounded; the source of the second switching tube M2, the drain of the third switching tube M3 and one end G of the inductor L1 are connected together; the other end H of the inductor L1 is connected with one end of the auxiliary circuit filter capacitor C2 and used for outputting an auxiliary circuit output voltage; the other end of the auxiliary filter capacitor C2 is grounded.

The multi-winding transformer, the main diode D1 and the auxiliary diode D2 form a flyback topology, and the buck circuit is cascaded after the flyback topology as a buck topology, so that the output of the buck topology can be changed in a range smaller than the output voltage of the main circuit.

When the gate input of the first switching tube M1 is high, the first switching tube M1 is turned on, the input voltage VIN transfers energy to the exciting inductance of the primary coil, and the main diode D1 and the auxiliary diode D2 are turned off in reverse.

When the gate input of the first switching tube M1 is low, the first switching tube M1 is turned off, and at this time, the main diode D1 and the auxiliary diode D2 are turned on, and the excitation inductance of the primary coil transfers energy to the excitation inductances of the first secondary coil and the second secondary coil.

When the main diode D1 is turned on, the exciting inductor of the first secondary winding transfers energy backward, and a main output voltage VOUT1 is generated. When the auxiliary diode D2 is turned on, the exciting inductance of the second secondary coil transfers energy backward, generating an auxiliary intermediate voltage. The auxiliary circuit intermediate voltage is continuously transmitted to the buck circuit, and since the gate voltages of the second switching tube M2 and the third switching tube M3 in the buck circuit are in opposite phases, the third switching tube M3 is turned off when the second switching tube M2 is turned on, and the inductor L1 stores energy; on the contrary, when the second switching tube M2 is turned off, the third switching tube M3 is turned on, and the energy stored in the inductor L1 is transferred backward to generate the auxiliary circuit output voltage VOUT 2.

In another embodiment, to obtain a more stable main output voltage VOUT1, the dc transformer module may further include: main circuit filter capacitance C1; one end of the main circuit filter capacitor C1 is connected to the cathode of the main circuit diode D1, and the other end is grounded.

In fig. 2, resistor R1 represents a load externally connected to main output voltage VOU 1. The resistor R2 represents a load externally connected to the auxiliary output voltage VOUT 2.

In one embodiment, referring to fig. 3, the main path feedback and control module may include: the circuit comprises a first sampling circuit, an optical coupler and a first driving circuit.

The first sampling circuit is used for sampling the output voltage of the main circuit to obtain a first sampling signal;

the optical coupler is used for comparing the first sampling signal with the reference voltage of the optical coupler to generate a control signal; it will be appreciated that the optocoupler functions as: as a reference voltage to be compared with the first sampling signal.

The first driving circuit is used for generating a first switching signal under the control of the control signal.

Optionally, the first driving circuit includes: and the peak circuit mode is adopted. Illustratively, the driver chip may be a driver chip of a type equivalent to UCC28C42, UCC28C40 or UCC38C 42. It will be appreciated that in an actual circuit, the first driver circuit also includes peripheral circuits of the driver chip.

In one embodiment, with continued reference to fig. 3, the secondary feedback and control module may include: the second sampling circuit, the frequency compensation circuit, the PWM generator and the second driving circuit; wherein the content of the first and second substances,

the second sampling circuit is used for sampling the output voltage of the auxiliary circuit to obtain a second sampling signal;

and the frequency compensation circuit is used for carrying out frequency compensation on the second sampling signal to obtain a second sampling signal with stable frequency response. Alternatively, the frequency compensation circuit may be a type III compensation circuit, but is not limited thereto, and any circuit capable of realizing frequency compensation is suitable for use in the embodiment of the present invention.

A PWM (pulse width modulation) generator for comparing a triangular wave generated in the PWM generator with a second sampling signal with stable frequency response to generate a PWM square wave;

and the second driving circuit is used for generating a second switching signal and a third switching signal under the control of the PWM square wave.

Optionally, the second driving circuit comprises: a dual output high side gate driver or a high and low side gate driver. Illustratively, the second driving circuit can be built by a driving chip with the model number of LM5106 and peripheral circuits thereof. The driving chip with the model LM5106 is a high-side gate driver, and can generate two opposite-phase driving signals with dead time.

It should be noted that the specific circuit structures of the main circuit feedback and control module and the auxiliary circuit feedback and control module shown above are only examples, and do not constitute a limitation on the embodiments of the present invention. Any circuit capable of voltage sampling and driving the formation of switching signals for feedback and control based on the sampled voltage is suitable for use in embodiments of the present invention.

It should be noted that the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the description of the specification, reference to the description of the term "one embodiment", "some embodiments", "an example", "a specific example", or "some examples", etc., means that a particular feature or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples described in this specification can be combined and combined by those skilled in the art.

While the invention has been described in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a review of the drawings, the disclosure, and the appended claims.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.