CN115425850A

CN115425850A - Flyback switching power supply absorption circuit, transformer leakage inductance absorption method and chip

Info

Publication number: CN115425850A
Application number: CN202211238157.9A
Authority: CN
Inventors: 林新春; 张�杰; 郑凌波
Original assignee: Qidong Lishengmei Integrated Circuit Co ltd; Lii Semiconductor Inc
Current assignee: Qidong Lishengmei Integrated Circuit Co ltd; Lii Semiconductor Inc
Priority date: 2022-10-11
Filing date: 2022-10-11
Publication date: 2022-12-02

Abstract

The invention relates to the technical field of electricity, in particular to a flyback switching power supply absorption circuit, a transformer leakage inductance absorption method and a chip, which comprise the following steps: the transformer comprises a primary coil NP and a secondary coil NS; the primary side sub-circuit comprises an energy storage branch connected with a primary side coil NP and an absorption branch connected with the primary side coil NP, when the energy storage branch is conducted, the primary side coil NP stores energy, and when the absorption branch is conducted, the leakage inductance energy of the transformer is absorbed; and the secondary side sub-circuit is connected with the secondary side coil NS, and provides output voltage VOUT for a load connected with the secondary side coil NS when the secondary side coil NS is conducted. The problem of low power conversion efficiency can be solved. Leakage inductance energy is absorbed through the absorption branch circuit so as to be used by a load connected with the secondary side sub-circuit, and the power supply conversion efficiency can be improved.

Description

Flyback switching power supply absorption circuit, transformer leakage inductance absorption method and chip

Technical Field

The invention relates to the technical field of electricity, in particular to an absorption circuit of a flyback switching power supply, a leakage inductance absorption method of a transformer and a chip.

Background

In the flyback switching power supply, due to the existence of leakage inductance of the transformer, the flyback switching power supply generates a large peak voltage at the moment of switching-off of the switching tube, and the peak voltage is coupled to induce the secondary side and is provided for a load, so that the secondary side and the switching tube bear higher voltage stress, the load or the switching tube may be damaged in severe cases, the operation stability and safety of the whole system are affected, and the problem of electromagnetic interference is caused, therefore, the peak voltage needs to be restrained in modes of clamping absorption and the like.

A conventional method for absorbing spike voltage includes: the voltage is clamped by a diode and a capacitor of an RCD (Residual Current Device) absorption circuit, so that the peak voltage is reduced and slowed down, and meanwhile, absorbed energy is discharged by using energy consumption elements (such as resistors).

However, although the conventional RCD absorption circuit can improve the withstand voltage problem and optimize the electromagnetic interference characteristics, the energy absorbed by the capacitor is merely released in the form of heat, and thus the power conversion efficiency is difficult to improve, which causes a problem of low power conversion efficiency.

Disclosure of Invention

The application provides a flyback switching power supply absorption circuit, a transformer leakage inductance absorption method and a chip, and can solve the problem of low power supply conversion efficiency. The application provides the following technical scheme:

in a first aspect, the present application provides an electric flyback switching power supply absorption circuit, including: a transformer, the transformer comprising a primary winding NP and a secondary winding NS;

the primary side sub-circuit comprises an energy storage branch connected with the primary side coil NP and an absorption branch connected with the primary side coil NP, when the energy storage branch is conducted, the primary side coil NP stores energy, and when the absorption branch is conducted, the leakage inductance energy of the transformer is absorbed;

and the secondary side sub-circuit is connected with the secondary side coil NS, and the secondary side coil NS is used for providing output voltage VOUT for a load connected with the secondary side coil NS when being conducted.

Optionally, the energy storage branch comprises a first switching tube Q1, and the first switching tube Q1 is connected in series with the primary winding NP;

the absorption branch comprises a second switch tube Q2, an absorption module, an absorption capacitor C3 and a power supply capacitor C5, wherein the second switch tube Q2 and the absorption capacitor C3 are connected in series and then are connected with a primary coil NP in parallel.

Optionally, the absorption module comprises:

the sampling VS end is connected between the absorption capacitor C3 and the second switching tube Q2;

a control GATE terminal connected to the control terminal of the second switch tube Q2, for controlling the on/off of the second switch tube Q2;

the grounding GND end is connected with the primary coil NP and the first switching tube Q1;

the power supply VDD end is connected with the power supply capacitor C5 and then grounded, and when the energy storage branch is conducted, the power supply VDD voltage for the absorption module to normally work is obtained;

the absorption module is configured to: under the condition that the first switch tube Q1 is disconnected, namely the energy storage branch circuit is disconnected, acquiring a voltage signal VS at the sampling VS end and a GND voltage signal at the grounding GND end; and under the condition that the voltage signal VS is smaller than the preset voltage threshold of the GND voltage signal, controlling the second switch tube Q2 to be switched on, so that the absorption capacitor C3 absorbs leakage inductance energy of the transformer, and after the absorption capacitor C3 finishes absorbing the leakage inductance energy, supplying power to a load connected with the output end of the secondary side sub-circuit.

Optionally, the energy storage branch and the absorption branch do not operate simultaneously.

Optionally, the absorption module includes a power supply submodule, an analog comparator CMP, a delay module TD, an AND gate circuit AND, AND a driving submodule DRV, where the power supply submodule includes a power unit, a single-phase conduction diode D1, AND the power supply capacitor C5;

one end of the power supply sub-module is connected with a sampling VS end of the absorption module to sample a voltage signal VS for the absorption module;

the inverting input end of the analog comparator CMP is connected with the VS end, and the non-inverting input end of the analog comparator CMP is connected with a reference voltage Vref;

the output end of the analog comparator CMP is connected with the first input end of the AND circuit AND;

one end of the delay module TD is connected with the output end of the analog comparator CMP, AND the other end of the delay module TD is connected with the second input end of the AND gate circuit AND;

the output end of the AND gate circuit AND is connected with the driving submodule DRV;

and the output end of the driving sub-module DRV is connected with the control GATE end of the absorption module.

Optionally, in response to the received voltage signal VS, the analog comparator CMP is configured to output a first high level signal to the delay module TD AND the AND circuit AND if the voltage signal VS is smaller than the reference voltage Vref by a preset voltage threshold;

in response to the received first high level signal, the delay module TD is configured to output a second high level signal to the AND circuit AND;

in response to the received first high level signal AND the second high level signal, the AND circuit AND is configured to output a third high level signal to the driving sub-module DRV;

in response to the received third high level signal, the driver sub-module DRV is configured to output a driving signal to a control GATE terminal of the absorption module, so that the second switch tube Q2 connected to the control GATE terminal is turned on after receiving the driving signal that is high level.

Optionally, the delay module TD further includes a timer;

in response to the first high level signal received by the delay module TD, the timer is configured to start countdown based on a preset duration, and output an end signal St when the countdown is finished;

in response to the end signal St, the delay module TD is further configured to output a first low level signal to the AND circuit AND.

Optionally, in response to the received first low-level signal, the AND-gate circuit AND is further configured to output a second low-level signal;

in response to the received second low level signal, the driving sub-module DRV is further configured to output a third low level signal to the control GATE terminal, so that the second switch tube Q2 connected to the control GATE terminal is turned off after receiving the third low level signal.

Optionally, the preset time period is less than a discharge time period of the secondary line NS.

In a second aspect, a transformer leakage inductance absorption method of the absorption circuit of the flyback switching power supply is provided, which includes:

under the condition that the first switching tube Q1 is disconnected, namely the energy storage branch is disconnected, acquiring a voltage signal VS at a sampling VS end of an absorption module in the absorption branch and a GND voltage signal at a grounding GND end of the absorption module;

under the condition that the voltage signal VS is smaller than a preset voltage threshold of the GND voltage signal, controlling a second switch tube Q2 connected with a control GATE end of the absorption module to be conducted through the absorption module;

and under the condition that the second switching tube Q2 is switched on, the leakage inductance energy of the transformer is absorbed by an absorption capacitor C3 in the absorption branch, and after the absorption capacitor C3 finishes absorbing the leakage inductance energy, the power is supplied to a load connected with the output end of the secondary side sub-circuit.

In a third aspect, an absorption chip of a flyback switching power supply is provided, which includes the absorption module of the absorption circuit of the flyback switching power supply.

Optionally, the absorption chip includes a sampling VS terminal, a control GATE terminal, a ground GND terminal, and a power VDD terminal.

Optionally, the absorption chip further includes a second switching tube Q2.

Optionally, the sink chip further includes a sampling VS terminal, a ground GND terminal, and a power VDD terminal.

The beneficial effect of this application lies in: the transformer comprises a primary coil NP and a secondary coil NS; the primary side sub-circuit comprises an energy storage circuit and an absorption circuit, the energy storage branch comprises a first switching tube Q1, and the absorption branch comprises a second switching tube Q2, an absorption chip and an absorption capacitor C3; a secondary side sub-circuit connected to the secondary side coil NS; under the condition that the first switch tube is closed, acquiring a voltage signal VS at the VS end of the absorption chip and a GND voltage at the GND end of the absorption chip; under the condition that the voltage signal VS is smaller than the GND voltage, the second switching tube is controlled to be conducted, so that the leakage inductance current of the transformer is used for charging the absorption capacitor; the absorption capacitor resonates with the parasitic capacitor when the leakage inductance current is 0; during the resonance process, a load connected to the output of the secondary side sub-circuit is supplied. The problem of power conversion efficiency is lower is solved. The leakage inductance energy is absorbed by the absorption chip so as to be used by a load connected with the secondary side sub-circuit, and the power supply conversion efficiency can be improved.

In addition, the absorption chip can effectively solve the problem of peak voltage at the drain end of the first switching tube in the primary side sub-circuit after the first switching tube is closed, so that the impact damage of the peak voltage to devices in the circuit is reduced, on one hand, the safety of the devices in the circuit can be protected, and on the other hand, the switching tube with lower withstand voltage can be used, so that the circuit cost is reduced.

In addition, the leakage inductance current is absorbed through the absorption capacitor, the absorption capacitor resonates with the parasitic capacitor under the condition that the leakage inductance current is 0, and power is supplied to a load connected with the output end of the secondary side sub-circuit in the resonant process, so that energy consumption through a resistor is avoided, and circuit heating can be reduced.

In addition, when the primary coil is conducted, the absorption chip is supplied with power through the input voltage without additional power supply, on one hand, the complexity of the circuit can be reduced, and on the other hand, resources can be saved.

In addition, the second switch tube is used for replacing a diode, so that the conduction voltage drop during energy absorption can be reduced, and the conversion efficiency of the power supply is further improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments or the technical solutions in the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a partial waveform diagram of a flyback switching power supply without a snubber circuit;

FIG. 2 is a system schematic of a typical prior art RCD absorption circuit;

FIG. 3 is a partial voltage waveform diagram of FIG. 2;

fig. 4 is a schematic structural diagram of a snubber circuit of a flyback switching power supply according to an embodiment of the present application;

FIG. 5 is a partial voltage waveform diagram of FIG. 4;

FIG. 6 is a schematic view showing a specific structure of the absorption module of FIG. 4;

FIG. 7 is a schematic diagram of a specific structure of an absorbent chip provided in an embodiment of the present application;

fig. 8 is a flowchart of a transformer leakage inductance absorption method of a flyback switching power supply absorption circuit according to an embodiment of the present application.

Detailed Description

The technical solutions of the present application will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are only some embodiments of the present application, but not all embodiments. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments. It should be noted that, in the present application, the embodiments and features of the embodiments may be combined with each other without conflict.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the accompanying drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

In the application, where the contrary is not intended, directional terms such as "upper, lower, top, bottom" or the like are generally used with respect to the orientation shown in the drawings, or with respect to the component itself in the vertical, or gravitational direction; similarly, "inner and outer" refer to inner and outer relative to the profile of the components themselves for ease of understanding and description, but the above directional terms are not intended to limit the present application.

First, several terms referred to in the present application will be described.

Peak voltage: in the flyback switching power supply, due to the existence of transformer leakage inductance, the flyback switching power supply can generate a large peak voltage at the moment of switching-off of a switching tube, the voltage can be coupled and induced to a secondary side to be provided for a load, so that the secondary side and the switching tube bear higher voltage stress, the load or the switching tube can be damaged when the load or the switching tube is serious, the running stability and safety of the whole system are influenced, the problem of electromagnetic interference is caused, and restraining methods such as clamping absorption and the like must be adopted. The voltage waveform diagram of the drain terminal of the switching tube without the RCD absorption circuit is shown as Vd waveform in fig. 1, wherein Vin waveform is input voltage, vor waveform is reflected voltage of a secondary coil at a primary coil, and Vspike waveform is peak voltage generated by leakage inductance.

A system schematic diagram of an existing typical RCD snubber circuit is shown in fig. 2, a schematic diagram of a waveform of a drain terminal voltage Vd1 of a switching tube Q1 is shown by a solid line Vd1 in fig. 3, a schematic diagram of a waveform of a cathode voltage VA1 of a diode D5 is shown by a dashed line Vd1 in fig. 3, and with reference to fig. 2 and 3, the operating principle is as follows: due to the existence of the leakage inductance Lk of the transformer, the transformer cannot directly transfer energy to the secondary coil at the moment of primary turn-off (corresponding to the time t1 in fig. 3), the current of the primary coil cannot immediately drop to zero, but the parasitic capacitor Cds from the drain of the switching tube Q1 to the ground is continuously charged, the voltage of the drain rapidly rises until the voltage Vd1 of the drain is greater than the sum of the input voltage Vin and the reflected voltage Vor of the secondary output voltage on the primary coil (corresponding to the time t2 in fig. 3), that is, vd1 is greater than Vin + Vor, the secondary coil is turned on, and the energy on the coil is transferred to the secondary coil to supply power to a load; at this time, due to the existence of the leakage inductance of the primary coil, the parasitic capacitor Cds will be continuously charged, the drain voltage Vd1 continues to rise until the drain voltage Vd1 is larger than the cathode voltage VA1 of the absorption circuit by the conduction voltage drop of the diode D5, that is, vd1> VA1+ Vdio, the drain voltage Vd1 is clamped by the absorption circuit, and at the same time, the leakage inductance current starts to charge the capacitor C3 of the absorption circuit, and the voltage VA1 slowly rises until the leakage inductance current decreases to 0 (corresponding to time t3 in fig. 3). After the above process is finished, the energy on the parasitic capacitor Cds continues to participate in resonance until the energy is consumed, and the energy charged to the absorption capacitor C3 by the leakage inductance is consumed by the energy consumption device resistor R in the absorption circuit (corresponding to time t4 in fig. 3).

A power supply submodule: the power supply sub-module is a power supply which can be directly attached to a printed circuit board and is characterized by supplying power to an Application Specific Integrated Circuit (ASIC), a Digital Signal Processor (DSP), a microprocessor, a memory, a Field Programmable Gate Array (FPGA) and other digital or analog loads. Generally, such modules are referred to as load (POL) power supply systems or point-of-use power supply systems (PUPS). Due to the advantages of the modular structure, the modular power supply is widely used in the communication fields of switching equipment, access equipment, mobile communication, microwave communication, optical transmission, routers and the like, and in automotive electronics, aerospace and the like.

A diode: a diode is an electronic device made of semiconductor material (silicon, selenium, germanium, etc.). It has one-way conducting performance, that is, when positive voltage is applied to the anode of the diode, the diode is conducted. When a reverse voltage is applied to the anode and the cathode, the diode is turned off. Therefore, turning on and off the diode corresponds to turning on and off the switch. Diodes are one of the earliest semiconductor devices and are widely used. In particular, in various electronic circuits, diodes and components such as resistors, capacitors and inductors are reasonably connected to form circuits with different functions, so that various functions such as alternating current rectification, modulation signal detection, amplitude limiting and clamping, and power supply voltage stabilization can be realized. The diode traces can be found in common radio circuits, in other household appliances or in industrial control circuits.

Analog Comparator (Comparator, CMP): the analog quantity is compared with a standard value. Above which a high (or low) level is output, and vice versa. For example, a temperature signal is connected to the non-inverting terminal of the operational amplifier, the inverting terminal is connected to a voltage reference (representing a certain temperature), when the temperature is higher than the reference value, the operational amplifier outputs a high level to control the heater to be turned off, and when the temperature signal is lower than the reference value, the operational amplifier outputs a low level to turn on the heater. This op-amp is a simple comparator, since the input and output are in phase, called a non-inverting comparator.

Reflected voltage: the reflected voltage refers to that in the flyback switching power supply, when a switching tube is disconnected, energy stored in a transformer is not absorbed by a secondary side in time, and then the energy returns to a primary side, so that the switching power supply is low in efficiency, and the switching tube is easy to break down.

The flyback switching power supply absorption circuit provided by the present application is described in detail below.

As shown in fig. 4, an embodiment of the present application provides a flyback switching power supply snubber circuit, which at least includes: a transformer 110, a primary side sub-circuit 120, and a secondary side sub-circuit 130. The transformer 110 includes a primary winding NP and a secondary winding NS.

In this embodiment, the primary sub-circuit 120 includes an energy storage branch connected to the primary coil NP and an absorption branch connected to the primary coil NP, and the energy storage branch and the absorption branch do not work at the same time. When the energy storage branch is conducted, the primary coil NP stores energy, and when the absorption branch is conducted, the leakage inductance energy of the transformer is absorbed.

The energy storage branch comprises a first switching tube Q1, and the first switching tube Q1 is connected with a primary coil NP in series; the absorption branch comprises a second switch tube Q2, an absorption module, an absorption capacitor C3 and a power supply capacitor C5, wherein the second switch tube Q2 and the absorption capacitor C3 are connected in series and then are connected with the primary coil NP in parallel.

In actual implementation, the power capacitor C5 may also be disposed inside the absorption module, and the present embodiment does not limit the positional relationship between the power capacitor C5 and the absorption module.

Referring to fig. 4, in the present embodiment, the absorption module includes a sampling VS terminal, a control GATE terminal, a ground GND terminal, and a power VDD terminal.

The sampling VS end is connected between the absorption capacitor C3 and the second switching tube Q2; the control GATE end is connected to the control end of the second switch tube Q2 and is used for controlling the on and off of the second switch tube Q2; the grounding GND end is connected with the primary coil NP and the first switching tube Q1; and the power supply VDD end is grounded after being connected with the power supply capacitor C5, and when the energy storage branch is conducted, the power supply VDD voltage for the absorption module to normally work is obtained.

The absorption capacitor C3 may be a non-polar capacitor, and the second switch Q2 includes a parasitic diode DQ2.

In this embodiment, the absorption module is configured to: under the condition that the first switching tube Q1 is disconnected, namely the energy storage branch circuit is disconnected, acquiring a voltage signal VS at a sampling VS end of the absorption module and a GND voltage signal at a grounding GND end; and under the condition that the voltage signal VS is smaller than the preset voltage threshold of the GND voltage signal, controlling the second switching tube Q2 to be switched on, so that the absorption capacitor C3 absorbs the leakage inductance energy of the transformer, and after the absorption capacitor C3 finishes absorbing the leakage inductance energy, supplying power to a load connected with the output end of the secondary side sub-circuit 130.

The preset voltage threshold is a preset voltage value, which may be 100 microvolts, 150 microvolts, or 200 microvolts, and the implementation manner of the preset voltage threshold is not limited in this embodiment.

In addition, in this embodiment, the parasitic capacitor Cds of the first switching tube Q1 supplies power to the load connected to the output terminal of the secondary side sub-circuit 130 during the resonance process.

The secondary sub-circuit 130 is connected to the secondary winding NS, and supplies an output voltage VOUT to a load connected to the secondary winding NS when the secondary winding NS is turned on.

In addition, in order to ensure that the absorption circuit of the flyback switching power supply can work normally, the absorption circuit of the flyback switching power supply further includes an input voltage sub-circuit 140. The input voltage sub-circuit 140 is connected to the primary sub-circuit 120, and is configured to provide the input voltage Vin to the primary sub-circuit 120.

As shown in fig. 4, optionally, the input voltage sub-circuit 140 is a full-wave bridge rectifier circuit, and specifically includes a diode D1, a diode D2, a diode D3, a diode D4, a capacitor C1, and a capacitor C2. The capacitor C1 may be a non-polar capacitor.

Referring to fig. 5, due to the existence of the leakage inductance of the transformer, energy cannot be directly transferred to the secondary winding NS at the instant when the first switching tube Q1 is turned off (i.e., at time t1 in fig. 5), at this time, the current in the primary winding NP does not immediately drop to zero, but continues to charge the parasitic capacitor Cds from the drain of the first switching tube Q1 to the ground, and the drain voltage Vd2 rapidly rises until the drain voltage Vd2 is greater than the sum of the input voltage Vin and the reflected voltage Vor of the output voltage of the secondary sub-circuit 120 on the primary winding NP (i.e., at time t2 in fig. 5), at this time, the drain voltage Vd2 may be represented by the following formula:

Vd2>Vin+Vor

in the formula, vd2 is the drain voltage of the drain of the first switching tube Q1, vin is the input voltage, and Vor is the reflected voltage of the output voltage of the secondary side sub-circuit 120 on the primary winding NP.

At this time, the secondary winding NS is turned on, and the energy of the primary winding NP is transferred to the secondary winding NS and supplies power to the load connected to the output terminal of the secondary sub-circuit 120.

Meanwhile, due to the existence of the leakage inductance of the transformer, the parasitic capacitance Cds will continue to be charged, so that the drain voltage Vd2 continues to rise until the drain voltage Vd2 is larger than the voltage signal VS of the body diode cathode of the second switching tube Q2 by one body diode conduction voltage drop VQ2 (refer to the waveform of the voltage signal VS in fig. 5), at this time, the drain voltage Vd2 may be represented by the following formula:

Vd2>VS+VQ2

in the formula, vd2 is the drain voltage of the drain of the first switching tube Q1; VS is a voltage signal VS of the cathode of the body diode of the second switching tube Q2, that is, a voltage detected by the sampling VS end of the absorption module; VQ2 is the body diode conduction voltage drop of the second switching tube Q2.

When the absorption module detects that the voltage signal VS is smaller than the GND voltage signal of the ground GND terminal, the absorption module turns on the second switch tube Q2, at this time, the drain voltage Vd2 is almost the same as the voltage signal VS, the leakage current starts to charge the absorption capacitor C3, and the voltage signal VS slowly rises until the leakage current decreases to 0 (i.e., time t3 in fig. 5). Then, the absorption capacitor C3, the parasitic capacitor Cds and the leakage inductance continue to resonate, and the energy collected by the absorption capacitor C3 is transferred to the secondary coil NS and supplies power to the load in the resonant process until the energy is consumed (i.e., time t4 in fig. 5). After the timing of the delay module TD is finished, the second switch Q2 is turned off, the voltage signal VS (i.e. the waveform of the VS signal indicated by the dashed line in fig. 5) is always constant and will not decrease, and the drain voltage Vd2 has a load in the circuit, so the current will decrease, and the drain voltage Vd2 will also slightly decrease.

As shown in fig. 6, the sink module includes a power supply sub-module, an analog comparator CMP, a delay module TD, an AND circuit AND, AND a driving sub-module DRV. The power supply submodule comprises a power unit, a single-phase conducting diode D1 and a power supply capacitor C5.

In this embodiment, one end of the power sub-module is connected to the sampling VS end of the absorption module to sample the voltage signal VS for the absorption module.

The inverting input end of the analog comparator CMP is connected with the VS end, and the non-inverting input end of the analog comparator CMP is connected with the reference voltage Vref; the output terminal of the analog comparator CMP is connected to the first input terminal of the AND circuit AND.

One end of the delay module TD is connected with the output end of the analog comparator CMP, AND the other end of the delay module TD is connected with the second input end of the AND gate circuit AND; meanwhile, the output end of the AND circuit AND is connected with the driving submodule DRV; the output end of the driving sub-module DRV is connected with the control GATE end of the absorption module.

The driving sub-module DRV is connected to the second switching tube Q2 through the control GATE terminal of the absorption module to control the second switching tube Q2 to be turned on or turned off.

In this embodiment, when the primary winding NP is turned on, the voltage signal VS is the sum of the input voltage VIN and the voltage across the absorption capacitor C3.

When the energy storage branch is disconnected, the primary winding NP is turned off, AND in the absorption module, when the analog comparator CMP detects that the voltage signal VS is lower than the reference voltage Vref, the analog comparator CMP outputs a high level to one end of the AND circuit AND the delay module TD.

The voltage value of the reference voltage Vref includes-330 mv, and in practical implementation, the voltage value of the reference voltage Vrfe may be set according to practical situations, and the voltage value of the reference voltage Vref is not limited in this embodiment.

The delay module TD defaults to output a high level signal to the other end of the AND circuit AND after receiving the high level output by the analog comparator CMP. The AND circuit AND outputs a high level to the driving module DRV after receiving the high level signal output by the delay module TD.

After receiving the high level signal output by the delay module TD, the driving module DRV outputs a high level driving signal to the control GATE terminal of the absorption module, so that the second switch Q2 is turned on.

Specifically, under the condition that the primary coil NP is turned off, in response to the received voltage signal VS, the analog comparator CMP is configured to output a first high level signal to the delay module TD AND the AND gate AND circuit when the voltage signal VS is smaller than a preset voltage threshold of the reference voltage Vref; in response to the received first high level signal, the delay module TD is configured to output a second high level signal to the AND circuit AND; the AND gate circuit AND is used for outputting a third high level signal to the driving sub-module DRV in response to the received first high level signal AND the second high level signal; in response to the received third high level signal, the driving sub-module DRV is configured to output a driving signal to the control GATE terminal of the absorption module, so that the second switching tube Q2 connected to the control GATE terminal is turned on after receiving the driving signal with a high level.

In this embodiment, after the delay module TD receives the high level output by the analog comparator CMP, it will output a high level signal to the other end of the AND circuit AND by default, AND at the same time, the delay module TD will start to count down.

When the countdown of the delay module TD is finished, the delay module TD will output a low level signal to the AND circuit AND. The AND circuit AND outputs a low level signal to the driving sub-module DRV when receiving the low level signal sent by the delay module TD. After receiving the low level signal sent by the AND circuit AND, the driving submodule DRV outputs a low level driving signal to the control GATE terminal of the absorption module, so that the second switching tube Q2 is turned off.

Specifically, the delay module TD further comprises a timer; in response to the first high level signal received by the delay module TD, the timer is configured to start countdown based on a preset duration, and output an end signal St when the countdown is finished; the delay block TD is further configured to output a first low level signal to the AND circuit AND in response to the end signal St. In response to the received first low-level signal, the AND gate AND is further configured to output a second low-level signal; in response to the received second low level signal, the driving sub-module DRV is further configured to output a third low level signal to the control GATE terminal, so that the second switching tube Q2 connected to the control GATE terminal is turned off after receiving the third low level signal.

The preset time is less than the discharge time of the secondary winding NS, and specifically, the preset time is less than the minimum value of the discharge time of the secondary winding NS. In this embodiment, the preset duration ranges from 50ns to 2 us. In actual implementation, the preset duration can be set according to actual conditions, and the value range of the preset duration is not limited in this embodiment.

In summary, the flyback switching power supply absorption circuit provided in this embodiment includes a transformer, where the transformer includes a primary winding NP and a secondary winding NS; the primary side sub-circuit comprises an energy storage circuit and an absorption circuit, the energy storage branch comprises a first switching tube Q1, and the absorption branch comprises a second switching tube Q2, an absorption chip and an absorption capacitor C3; a secondary side sub-circuit connected to the secondary side coil NS; under the condition that the first switch tube is closed, acquiring a voltage signal VS at the VS end of the absorption chip and a GND voltage at the GND end of the absorption chip; under the condition that the voltage signal VS is smaller than the GND voltage, the second switching tube is controlled to be conducted, so that the leakage inductance current of the transformer is used for charging the absorption capacitor; the absorption capacitor resonates with the parasitic capacitor when the leakage inductance current is 0; during the resonance process, a load connected to the output of the secondary side sub-circuit is supplied. The problem of low power conversion efficiency is solved. The leakage inductance energy is absorbed by the absorption chip so as to be used by a load connected with the secondary side sub-circuit, and the power supply conversion efficiency can be improved.

In addition, the leakage inductance current is absorbed through the absorption capacitor, the absorption capacitor resonates with the parasitic capacitor under the condition that the leakage inductance current is 0, and in the process of resonating, the absorption capacitor supplies power to a load connected with the output end of the secondary side sub-circuit, so that energy consumption through a resistor is avoided, and circuit heating can be reduced.

In addition, when the primary side coil is conducted, the absorption chip is supplied with power through the input voltage without additional power supply, on one hand, the complexity of the circuit can be reduced, and on the other hand, resources can be saved.

Fig. 7 is a snubber chip of a flyback switching power supply according to an embodiment of the present application, including a snubber module in a snubber circuit of the flyback switching power supply.

Optionally, the sink chip includes a sampling VS terminal, a control GATE terminal, a ground GND terminal, and a power VDD terminal.

Optionally, the sinking chip further includes a second switch Q2, and at this time, the sinking chip further includes a sampling VS terminal, a ground GND terminal, and a power VDD terminal.

In practical implementation, the second switching tube Q2 may also be disposed outside the absorption chip, and the present embodiment does not limit the positional relationship between the second switching tube Q2 and the absorption chip.

For a detailed description of the present embodiment, reference is made to the above embodiment of the absorption circuit of the flyback switching power supply, and the detailed description of the present embodiment is omitted here.

Fig. 8 is a flowchart of a transformer leakage inductance absorption method for a flyback switching power supply absorption circuit according to an embodiment of the present application. The method at least comprises the following steps:

step 801, acquiring a voltage signal VS at a sampling VS end of an absorption chip in the absorption branch and a GND voltage signal at a ground GND end of the absorption chip when the first switching tube Q1 is disconnected, that is, the energy storage branch is disconnected.

And step 802, under the condition that the voltage signal VS is smaller than the preset voltage threshold of the GND voltage signal, controlling the conduction of a second switch tube Q2 connected with a control GATE end of the absorption chip through the absorption chip.

And 803, under the condition that the second switching tube Q2 is turned on, absorbing the leakage inductance energy of the transformer by the absorption capacitor C3 in the absorption branch, and supplying power to a load connected with the output end of the secondary side sub-circuit after the absorption capacitor C3 finishes absorbing the leakage inductance energy.

For details of the related description of the present embodiment, reference is made to the embodiment of the absorption circuit of the flyback switching power supply, and details of the present embodiment are not repeated herein.

In summary, in the transformer leakage inductance absorption method provided in this embodiment, when the energy storage branch is disconnected, the absorption chip controls the second switch tube to be turned on, so that the absorption capacitor absorbs the leakage inductance energy of the transformer, and supplies power to the load connected to the output terminal of the secondary side sub-circuit, thereby improving the power conversion efficiency.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

It is to be understood that the above-described embodiments are only a few, but not all, of the embodiments described herein. Based on the embodiments in the present application, those skilled in the art may make other changes or modifications without creative efforts, and all should fall within the protection scope of the present application.

Claims

1. A flyback switching power supply snubber circuit, wherein the flyback switching power supply snubber circuit includes:

a transformer, the transformer comprising a primary winding NP and a secondary winding NS;

and the secondary side sub-circuit is connected with the secondary side coil NS, and provides output voltage VOUT for a load connected with the secondary side coil NS when the secondary side coil NS is conducted.

2. The flyback switching power supply snubber circuit of claim 1,

the energy storage branch comprises a first switching tube Q1, and the first switching tube Q1 is connected with the primary coil NP in series;

the absorption branch comprises a second switch tube Q2, an absorption module, an absorption capacitor C3 and a power supply capacitor C5, wherein the second switch tube Q2 is connected with the absorption capacitor C3 in series and then is connected with the primary coil NP in parallel.

3. The flyback switching power supply snubber circuit of claim 2, wherein the snubber module comprises:

a control GATE terminal connected to the control terminal of the second switching tube Q2, for controlling the on/off of the second switching tube Q2;

the power supply VDD end is connected with the power supply capacitor C5 and then grounded, and when the energy storage branch circuit is conducted, the power supply VDD voltage for the absorption module to normally work is obtained;

the absorption module is used for: under the condition that the first switching tube Q1 is disconnected, namely the energy storage branch is disconnected, acquiring a voltage signal VS at the sampling VS end and a GND voltage signal at the grounding GND end; and under the condition that the voltage signal VS is smaller than the preset voltage threshold of the GND voltage signal, controlling the second switch tube Q2 to be switched on so that the absorption capacitor C3 absorbs the leakage inductance energy of the transformer and supplies power to a load connected with the output end of the secondary side sub-circuit after the absorption capacitor C3 absorbs the leakage inductance energy.

4. The absorption circuit of claim 1, wherein the energy storage branch and the absorption branch do not operate simultaneously.

5. The flyback switching power supply absorption circuit of claim 3, wherein the absorption module comprises a power supply submodule, an analog comparator CMP, a delay module TD, an AND gate circuit AND, AND a driving submodule DRV, wherein the power supply submodule comprises a power unit, a single-phase conduction diode D1 AND the power supply capacitor C5;

the inverting input end of the analog comparator CMP is connected with the sampling VS end, and the non-inverting input end of the analog comparator CMP is connected with a reference voltage Vref;

6. The flyback switching power supply snubber circuit of claim 5,

in response to the received voltage signal VS, the analog comparator CMP is configured to output a first high level signal to the delay module TD AND the AND-gate AND if the voltage signal VS is smaller than the preset voltage threshold of the reference voltage Vref;

in response to the received first high level signal, the delay module TD is configured to output a second high level signal to the AND gate AND;

in response to the received first high level signal AND the second high level signal, the AND gate AND is used for outputting a third high level signal to the driving sub-module DRV;

in response to the received third high level signal, the driving submodule DRV is configured to output a driving signal to the control GATE terminal of the absorption module, so that the second switching tube Q2 connected to the control GATE terminal is turned on after receiving the driving signal that is high level.

7. The absorption circuit of claim 6, wherein said delay module TD further comprises a timer;

in response to the first high level signal received by the delay module TD, the timer is configured to start countdown based on a preset time length, and output an end signal St when the countdown is finished;

8. The flyback switching power supply snubber circuit of claim 7,

in response to the received first low-level signal, the AND gate AND is further configured to output a second low-level signal;

9. The absorption circuit of claim 7, wherein the predetermined time period is less than a discharge time period of the secondary winding NS.

10. A transformer leakage inductance absorption method based on the absorption circuit of the flyback switching power supply as claimed in any one of claims 1 to 10, the method comprising:

under the condition that the first switch tube Q1 is disconnected, namely the energy storage branch circuit is disconnected, acquiring a voltage signal VS at a sampling VS end of an absorption module in the absorption branch circuit and a GND voltage signal at a grounding GND end of the absorption module;

11. An absorption chip of a flyback switching power supply, characterized by comprising the absorption module of the flyback switching power supply absorption circuit according to any one of claims 1 to 10.

12. The sinking chip of the flyback switching power supply of claim 11, wherein the sinking chip comprises a sampling VS terminal, a control GATE terminal, a ground GND terminal and a power VDD terminal.

13. The snubber chip of the flyback switching power supply of claim 11, further comprising a second switching transistor Q2.

14. The snubber chip of the flyback switching power supply of claim 13, comprising a sampling VS terminal, a ground GND terminal, and a power VDD terminal.