Switching power supply circuit and electronic equipment

Abstract

The invention relates to a switching power supply circuit and electronic equipment. The absorption capacitor in the switching power supply circuit can quickly absorb turn-off voltage energy of the power switch through the direct-connection circuit when the power switch is turned off, and the resistance value of the direct-connection circuit is smaller than that of the current-limiting resistor, so that the charging speed of the absorption capacitor can be improved, and the turn-off efficiency of the power switch is improved; when the power switch is switched on, the absorption capacitor quickly releases stored energy through the switching path, and the resistance value of the switching path is also smaller than that of the current-limiting resistor, so that the discharging speed of the absorption capacitor can be improved, and the switching-on efficiency of the power switch is improved. According to the switching power supply circuit, the switching circuit is switched to different paths when the power switch is in different on-off states, so that the switching efficiency of the power switch is improved, the switching loss is reduced, and the energy conversion efficiency of the switching power supply circuit is improved.

Description

Technical Field

[0001] The present application relates to the technical field of switching power supply circuits, and in particular to a switching power supply circuit and an electronic device. Background Art

[0002] The third-generation wide bandgap power semiconductor materials have the advantages of high thermal conductivity, high breakdown field strength and high saturated electron drift rate. Under the same voltage or current conditions, their on-resistance is only one thousandth of that of silicon devices, which can greatly reduce conduction losses; the switching frequency is more than ten times that of silicon devices, which can reduce the circuit design volume.

[0003] As a third-generation wide-bandgap semiconductor power device, SIC MOS (Silicon Carbide Metal-Oxide-Semiconductor Field-Effect Transistor) is often used as a power switch in switching power supply circuits. SIC MOS is affected by parasitic inductance and capacitance in the switching power supply circuit. A voltage surge is generated at both ends of the SIC MOS when it is turned off. This high-voltage surge increases the voltage stress requirements of the switch tube. To reduce this high-voltage surge, the conventional solution for switching power supply circuits is to use an RCD structure snubber circuit on the primary winding side of the converter. The RCD structure snubber circuit is simple to design, but the current limiting resistor in the RCD structure snubber circuit will cause the absorption capacitor to charge and discharge slowly, which will reduce the energy conversion efficiency of the switching power supply circuit. Summary of the Invention

[0004] The present application provides a switching power supply circuit and an electronic device to solve the problem of low energy conversion efficiency of existing switching power supply circuits.

[0005] In a first aspect, the present application provides a switching power supply circuit, characterized in that the switching power supply circuit includes a power switch, an absorption circuit, a converter, and a secondary rectifier circuit, wherein the source of the power switch is connected to the negative electrode of the power supply, the drain of the power switch is respectively connected to the absorption circuit and the primary side of the converter, the gate of the power switch is connected to the switching power supply chip, the absorption circuit is connected between the positive electrode of the power supply and the primary side of the converter, and the secondary side of the converter is connected to the secondary rectifier circuit;

[0006] The absorption circuit includes an absorption capacitor and a switching circuit, wherein the first end of the absorption capacitor is connected to the positive electrode of the power supply and the first end of the primary side of the converter respectively, the second end of the absorption capacitor is connected between the switching circuit and the second end of the primary side of the converter, and the switching circuit is also connected to the drain of the power switch;

[0007] When the power switch is turned off, the switching circuit switches to a direct-connect path, and the absorption capacitor absorbs the turn-off voltage energy of the power switch through the direct-connect path; when the power switch is turned on, the switching circuit switches to a switch path, and the absorption capacitor releases stored energy through the switch path. The resistance of the direct-connect path and the resistance of the switch path are both less than the resistance of the current limiting resistor.

[0008] Optionally, a first body diode is connected between the source and the drain of the power switch.

[0009] Optionally, a parasitic capacitor is connected between the source and drain of the power switch.

[0010] Optionally, the switching circuit includes a switching switch and an electromagnetic induction device, wherein a first end of the switching switch is connected to the second end of the absorption capacitor, a second end of the switching switch is connected to the first end of the electromagnetic induction device, a third end of the switching switch is respectively connected to the second end of the primary side of the converter, the second end of the electromagnetic induction device, and the drain of the power switch, and a second body diode is connected between the third end of the switching switch and the drain;

[0011] When the power switch is turned on, the electromagnetic induction device is powered on and turns on the switching switch to switch the switching circuit to the switching path; when the power switch is turned off, the electromagnetic induction device is powered off and turns off the switching switch and turns on the second body diode to switch the switching circuit to the direct-connect path.

[0012] Optionally, the electromagnetic induction device includes an auxiliary winding and / or an inductor.

[0013] Optionally, the switch is a field effect transistor.

[0014] Optionally, the secondary rectifier circuit includes a rectifier diode and a rectifier capacitor, the positive electrode of the rectifier diode is connected to the first end of the secondary side of the converter, and the negative electrode of the rectifier diode is connected back to the second end of the secondary side of the converter through the rectifier capacitor.

[0015] Optionally, the converter is a DC to DC transformer.

[0016] Optionally, when the power switch is turned off, the absorption capacitor absorbs the turn-off voltage energy of the power switch and the leakage inductance voltage energy reflected from the secondary side of the DC-DC transformer to the primary side through the direct-connection path.

[0017] In a second aspect, the present application provides an electronic device comprising any of the switching power supply circuits described above.

[0018] In a fourth aspect, the present application further provides a computer storage medium storing computer executable instructions, wherein the computer executable instructions are used to execute the above-mentioned switching power supply circuit.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages over the prior art: the switching power supply circuit provided by the embodiment of the present application includes a power switch, an absorption circuit, a converter and a secondary rectifier circuit, the source of the power switch is connected to the negative pole of the power supply, the drain of the power switch is respectively connected to the absorption circuit and the primary side of the converter, the gate of the power switch is connected to the switching power supply chip, the absorption circuit is connected between the positive pole of the power supply and the primary side of the converter, and the secondary side of the converter is connected to the secondary rectifier circuit; the absorption circuit includes an absorption capacitor and a switching circuit, and the first side of the absorption capacitor is connected to the switching circuit. The ends are respectively connected to the positive electrode of the power supply and the first end of the primary side of the converter, the second end of the absorption capacitor is connected between the switching circuit and the second end of the primary side of the converter, and the switching circuit is also connected to the drain of the power switch; the switching circuit switches to a direct-connection path when the power switch is turned off, and the absorption capacitor absorbs the turn-off voltage energy of the power switch through the direct-connection path; the switching circuit switches to a switching path when the power switch is turned on, and the absorption capacitor releases the stored energy through the switching path, and the resistance of the direct-connection path and the resistance of the switching path are both less than the resistance of the current-limiting resistor.

[0020] When the power switch is turned off, the absorption capacitor in the switching power supply circuit can quickly absorb the turn-off voltage energy of the power switch through a direct-connection path. Because the resistance of the direct-connection path is less than that of the current-limiting resistor, the charging speed of the absorption capacitor can be increased, thereby accelerating the turn-off efficiency of the power switch. When the power switch is turned on, the absorption capacitor quickly releases the stored energy through the switching path. Because the resistance of the switching path is also less than that of the current-limiting resistor, the discharge speed of the absorption capacitor can be increased, thereby accelerating the turn-on efficiency of the power switch. By switching the circuit to different paths when the power switch is in different on-off states, the switching efficiency of the power switch is accelerated, thereby reducing switching losses and improving the energy conversion efficiency of the switching power supply circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0024] Figure 1 A schematic diagram of the structure of a switching power supply circuit provided in an embodiment of the present application;

[0025] Figure 2 A schematic diagram of the structure of a switching power supply circuit provided in an embodiment of the present application;

[0026] Figure 3 A schematic diagram of the structure of a switching power supply circuit provided in an embodiment of the present application;

[0027] Figure 4 A schematic diagram of the structure of a switching power supply circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0029] The disclosure below provides many different embodiments or examples for implementing different configurations of the present invention. To simplify the disclosure of the present invention, the components and configurations of specific examples are described below. Of course, these are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or configurations discussed.

[0030] Figure 1 FIG1 is a schematic diagram of a switching power supply circuit in an embodiment of the present invention. The switching power supply circuit is applied to electronic devices, which may be power supply devices, industrial devices, smart home devices, terminal devices, or any other devices requiring power conversion.

[0031] Reference Figure 1The switching power supply circuit specifically includes a power switch Q1, an absorption circuit 110, a converter 120, and a secondary rectifier circuit 130. The source of the power switch Q1 is connected to the negative electrode of the power supply, the drain of the power switch Q1 is connected to the absorption circuit 110 and the primary side of the converter 120, respectively, the gate of the power switch Q1 is connected to the switching power supply chip 140, the absorption circuit 110 is connected between the positive electrode of the power supply and the primary side of the converter 120, and the secondary side of the converter 120 is connected to the secondary rectifier circuit 130.

[0032] The absorption circuit 110 includes an absorption capacitor C1 and a switching circuit 111. The first end of the absorption capacitor C1 is connected to the positive electrode of the power supply and the first end of the primary side of the converter 120, respectively. The second end of the absorption capacitor C1 is connected between the switching circuit 111 and the second end of the primary side of the converter 120. The switching circuit 111 is also connected to the drain of the power switch Q1.

[0033] The switching circuit 111 switches to a direct-connect path when the power switch Q1 is turned off, and the absorption capacitor C1 absorbs the turn-off voltage energy of the power switch Q1 through the direct-connect path. When the power switch Q1 is turned on, the switching circuit 111 switches to a switch path, and the absorption capacitor C1 releases stored energy through the switch path. The resistance of the direct-connect path and the resistance of the switch path are both smaller than the resistance of the current-limiting resistor.

[0034] Specifically, the power switch Q1 is a SIC MOS, and the absorption circuit 110 includes an absorption capacitor C1 and a switching circuit 111. The switching circuit 111 switches to different paths to connect to the absorption capacitor C1 when the power switch Q1 is in different on-off states. The switching circuit 111 switches to a direct-connect path when the power switch Q1 is turned off. The resistance of the direct-connect path is much smaller than the resistance of the current-limiting resistor. Therefore, the absorption capacitor C1 can quickly absorb the turn-off voltage energy of the power switch Q1 to accelerate the turn-off efficiency of the power switch Q1.

[0035] The switching circuit 111 switches to the switch path when the power switch Q1 is turned on. The resistance of the switch path is also smaller than the resistance of the current limiting resistor. Therefore, the absorption capacitor C1 can quickly release the stored energy to increase the conduction efficiency of the power switch Q1.

[0036] The switching circuit 111 switches to different paths when the power switch Q1 is in different on / off states, thereby increasing the switching efficiency of the power switch Q1 and reducing switching losses, thereby improving the energy conversion efficiency of the switching power supply circuit.

[0037] In one embodiment, referring to Figure 2 A first body diode is connected between the source and drain of the power switch Q1.

[0038] Specifically, when the power switch Q1 is turned on, its gate voltage causes a channel to be formed, and current can flow from the drain through the channel to the source. At this time, the drain voltage is higher than the source voltage. Because the cathode of the first body diode is connected to the drain and the anode is connected to the source, the first body diode is in a reverse biased state, that is, the first body diode is in a cut-off state.

[0039] When the power switch Q1 is turned off, the first body diode conducts forward, and current flows from the source of the power switch Q1 to the drain through the first body diode, thereby avoiding excessive drain voltage caused by the back electromotive force of the switching circuit 111 and protecting the power switch Q1.

[0040] In one embodiment, referring to Figure 2 A parasitic capacitor is connected between the source and drain of the power switch Q1.

[0041] Specifically, when the power switch Q1 is turned off, the drain voltage begins to rise. At this point, the power supply charges the parasitic capacitance of the power switch Q1 through the converter 120 and the switching circuit 111. Because the absorption capacitor C1 exists in the current path, according to Lenz's law, the current cannot change suddenly. Therefore, the charging process of the parasitic capacitance is a relatively slow process, and the charging current is limited by other resistive components.

[0042] When power switch Q1 turns on, the gate-to-source voltage rises above the threshold voltage. At this point, the parasitic capacitance discharges through the internal resistance of the gate drive circuit and related loops, with the discharge current flowing from the drain to the source. Due to the low on-resistance of power switch Q1, the parasitic capacitance discharges relatively quickly.

[0043] In one embodiment, the switching circuit 111 includes a switching switch Q2 and an electromagnetic induction device. The first end of the switching switch Q2 is connected to the second end of the absorption capacitor C1, the second end of the switching switch Q2 is connected to the first end of the electromagnetic induction device, and the third end of the switching switch Q2 is respectively connected to the second end of the primary side of the converter 120, the second end of the electromagnetic induction device, and the drain of the power switch Q1. A second body diode is connected between the third end of the switching switch Q2 and the drain.

[0044] When the power switch Q1 is turned on, the electromagnetic induction device is powered on and turns on the switching switch Q2 to switch the switching circuit 111 to the switching path; when the power switch Q1 is turned off, the electromagnetic induction device is de-energized and turns off the switching switch Q2, turning on the second body diode to switch the switching circuit 111 to the direct-connect path.

[0045] Specifically, when the power switch Q1 is turned on, the electromagnetic induction device is energized, so that the second end of the switching switch Q2 can be energized, thereby turning on the switching switch Q2. The switching circuit 111 is switched to the switching path when the switching switch Q2 is turned on. The switching path includes the switching switch Q2, and the absorption capacitor C1 is quickly discharged through the switching switch Q2 and the power switch Q1, that is, the stored energy is quickly released.

[0046] When the power switch Q1 is turned off, the electromagnetic induction device is not energized, and thus the second end of the switching switch Q2 cannot be energized, i.e., the switching switch Q2 is turned off. Turning off the switching switch Q2 causes the switching circuit 111 to switch to a direct-connection path. The direct-connection path includes the second body diode of the switching switch Q2, i.e., the absorption capacitor C1 quickly absorbs the turn-off voltage energy of the power switch Q1 through the second body diode.

[0047] By switching the switch Q2 to different on-off states when the power switch Q1 is in different on-off states, the switching circuit 111 is switched to different paths. Whether in the direct path or the switching path, the switching efficiency of the power switch Q1 can be accelerated, thereby reducing switching losses and improving the energy conversion efficiency of the switching power supply circuit.

[0048] In one embodiment, the electromagnetic induction device includes an auxiliary winding L1 and / or an inductor.

[0049] Specifically, the electromagnetic induction device includes an auxiliary winding L1 and / or an inductor and other inductive components, refer to Figure 2 In this embodiment, the electromagnetic induction device is implemented using the auxiliary winding L1.

[0050] When the power switch Q1 is turned on, Figure 3 The arrow in the figure indicates the direction of current flow. The potential at point c of the auxiliary winding L1 is positive, and the potential at point d is negative. At this time, point c of the auxiliary winding L1 is energized, causing the second end of the switching switch Q2 to be energized and turned on. The switching switch Q2 is turned on, causing the switching circuit 111 to switch to the switching path. The switching path includes the switching switch Q2, and the absorption capacitor C1 is quickly discharged through the switching switch Q2 and the power switch Q1, that is, the stored energy is quickly released.

[0051] When the power switch Q1 is turned off, Figure 4 The arrow in the figure indicates the direction of current flow. The potential at point c of the auxiliary winding L1 is negative, and the potential at point d is positive, so that the voltage at the second end of the switching switch Q2 is 0, that is, the switching switch Q2 is turned off. When the switching switch Q2 is turned off, the switching circuit 111 switches to a direct-connection path. The direct-connection path includes the second body diode of the switching switch Q2, that is, the absorption capacitor C1 quickly absorbs the turn-off voltage energy of the power switch Q1 through the second body diode.

[0052] In one embodiment, referring to Figure 2 , the switching switch Q2 is a field effect transistor.

[0053] Specifically, a field effect transistor is used to implement the switching switch Q2, and the gate of the field effect transistor is connected to the first end (point c) of the auxiliary winding L1, the drain of the field effect transistor is connected to the absorption capacitor C1, and the source of the field effect transistor is respectively connected to the second end of the primary side of the converter 120 and the second end (point d) of the auxiliary winding L1.

[0054] Reference Figure 3 When the power switch Q1 is turned on, the potential at point c of the auxiliary winding L1 is positive and the potential at point d is negative. At this time, point c of the auxiliary winding L1 is energized, causing the gate of the field-effect transistor to be energized and turned on. The field-effect transistor is turned on, causing the switching circuit 111 to switch to the switching path. The switching path includes the field-effect transistor, and the absorption capacitor C1 is quickly discharged through the field-effect transistor and the power switch Q1, that is, the stored energy is quickly released.

[0055] Reference Figure 4 When the power switch Q1 is turned off, the potential at point c of the auxiliary winding L1 is negative and the potential at point d is positive, so that the gate voltage of the field effect transistor is 0, that is, the field effect transistor is turned off. The field effect transistor is turned off, and the switching circuit 111 switches to a direct-connection path. The direct-connection path includes the second body diode of the field effect transistor, that is, the absorption capacitor C1 quickly absorbs the turn-off voltage energy of the power switch Q1 through the second body diode.

[0056] In one embodiment, referring to Figure 2 The secondary rectifier circuit 130 includes a rectifier diode D2 and a rectifier capacitor C2. The positive electrode of the rectifier diode D2 is connected to the first end of the secondary side of the converter 120, and the negative electrode of the rectifier diode D2 is connected back to the second end of the secondary side of the converter 120 through the rectifier capacitor C2.

[0057] Specifically, the secondary rectifier circuit 130 is used to convert the voltage outputted from the secondary side of the converter 120 into a DC voltage that meets the DC power requirements of the load.

[0058] Reference Figure 3 When power switch Q1 turns on, the current in the primary side of converter 120 increases, and transformer TR1 stores energy. Due to the same-terminal characteristics of transformer TR1 and the principle of electromagnetic induction, the polarity of the voltage induced in the secondary winding causes rectifier diode D2 to experience reverse voltage. This intensifies the magnetic field generated by the primary current of transformer TR1. According to Lenz's law, the polarity of the electromotive force induced in the secondary winding causes the cathode potential of rectifier diode D2 to be higher than the anode potential. Therefore, rectifier diode D2 cannot conduct, preventing reverse current flow. At this point, rectifier capacitor C2 supplies power to the subsequent load, releasing the previously stored energy.

[0059] Reference Figure 4 When the power switch Q1 is turned off, the primary side current of the converter 120 drops rapidly, the energy stored in the converter 120 begins to be released, and the voltage polarity induced by the secondary winding changes, causing the rectifier diode D2 to bear a forward voltage. When the forward voltage exceeds the conduction voltage drop of the diode, the rectifier diode D2 turns on. At this time, the current of the secondary winding of the converter 120 charges the rectifier capacitor C2 through the rectifier diode D2 and supplies power to the load. During the charging process, the rectifier capacitor C2 stores the energy released by the converter 120 and provides a stable DC voltage for the subsequent load. When the capacitor voltage of the rectifier capacitor C2 reaches a certain value, the charging current will gradually decrease and eventually reach a dynamic equilibrium state to maintain the stability of the output voltage.

[0060] In one embodiment, the converter 120 is a DC-DC transformer TR1 .

[0061] Specifically, converter 120 is implemented using a DC-DC transformer TR1, which converts one DC voltage into one or more DC voltages of different amplitudes. This transformer can step down a higher DC input voltage to a lower DC voltage suitable for load operation, or step up a lower DC voltage to a higher DC voltage. Its output voltage is typically highly stable, maintaining a specified accuracy within a certain load range and under input voltage fluctuations.

[0062] Reference Figure 3 When the power switch Q1 is turned on, according to Lenz's law, the potential at point a is positive and the potential at point b is negative; the potential at point e of the secondary winding is negative and the potential at point f is positive, and the secondary rectifier diode D2 is in the off state; the potential at point c of the auxiliary winding L1 is positive, energizing the gate of the field-effect transistor Q2, turning on Q2, and discharging the voltage surge stored in the capacitor C1 through the field-effect transistor Q2 and the power switch Q1.

[0063] Reference Figure 4 When the power switch Q1 is turned off, according to Lenz's law, the potential at point a is negative and the potential at point b is positive; the potential at point e of the secondary winding is positive and the potential at point f is negative, and the secondary rectifier diode D2 is in the on state; the potential at point c of the auxiliary winding L1 is negative, that is, the gate voltage of the field effect transistor Q2 is 0, Q2 is turned off, and the voltage surge reflected from the secondary winding to the primary passes through the body diode of Q2, charging C1 and absorbing the voltage surge.

[0064] In one embodiment, when the power switch Q1 is turned off, the absorption capacitor C1 absorbs the turn-off voltage energy of the power switch Q1 and the leakage inductance voltage energy reflected from the secondary side of the DC-DC transformer TR1 to the primary side through the direct-connection path.

[0065] Specifically, when the power switch Q1 is turned off, the secondary side of the DC-DC transformer TR1 will also reflect voltage energy to the primary side. At this time, the absorption capacitor C1 will not only absorb the turn-off voltage energy of the power switch Q1 through the direct-connection path, but also absorb the leakage inductance voltage energy reflected from the secondary side of the DC-DC transformer TR1 to the primary side. This prevents the reverse electromotive force generated by the leakage inductance voltage from being superimposed on the turn-off voltage and exceeding the withstand voltage limit of the power switch Q1. At this time, the voltage of the absorption capacitor C1 rises rapidly to suppress the drain-source voltage of the power switch Q1 within a safe range.

[0066] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a general hardware platform, or of course, by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the relevant technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling an electronic device (which can be a personal computer, a server, or a network device, etc.) to execute the switching power supply circuit described in each embodiment or certain parts of the embodiment.

[0067] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an", and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The switching power supply circuit steps, processes, and operations described herein are not to be interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative methods may be used.

[0068] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but is intended to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A switching power supply circuit, characterized in that: The switching power supply circuit includes a power switch, an absorption circuit, a converter, and a secondary rectifier circuit. The source of the power switch is connected to the negative electrode of the power supply, the drain of the power switch is connected to the absorption circuit and the primary side of the converter respectively, the gate of the power switch is connected to the switching power supply chip, the absorption circuit is connected between the positive electrode of the power supply and the primary side of the converter, and the secondary side of the converter is connected to the secondary rectifier circuit. The absorption circuit includes an absorption capacitor and a switching circuit, wherein the first end of the absorption capacitor is connected to the positive electrode of the power supply and the first end of the primary side of the converter respectively, the second end of the absorption capacitor is connected between the switching circuit and the second end of the primary side of the converter, and the switching circuit is also connected to the drain of the power switch; The switching circuit switches to a direct-connection path when the power switch is turned off, and the absorption capacitor absorbs the turn-off voltage energy of the power switch through the direct-connection path; The switching circuit switches to the switch path when the power switch is turned on, and the absorption capacitor releases stored energy through the switch path. The resistance of the direct-connect path and the resistance of the switch path are both smaller than the resistance of the current-limiting resistor.

2. The switching power supply circuit according to claim 1, wherein: A first body diode is connected between the source and the drain of the power switch.

3. The switching power supply circuit according to claim 2, wherein: A parasitic capacitor is connected between the source and drain of the power switch.

4. The switching power supply circuit according to claim 1, wherein: The switching circuit includes a switching switch and an electromagnetic induction device, wherein a first end of the switching switch is connected to the second end of the absorption capacitor, a second end of the switching switch is connected to the first end of the electromagnetic induction device, a third end of the switching switch is respectively connected to the second end of the primary side of the converter, the second end of the electromagnetic induction device, and the drain of the power switch, and a second body diode is connected between the third end of the switching switch and the drain; When the power switch is turned on, the electromagnetic induction device is powered on and turns on the switching switch to switch the switching circuit to the switching path; when the power switch is turned off, the electromagnetic induction device is powered off and turns off the switching switch and turns on the second body diode to switch the switching circuit to the direct-connect path.

5. The switching power supply circuit according to claim 4, characterized in that: The electromagnetic induction device includes an auxiliary winding and / or an inductor.

6. The switching power supply circuit according to claim 4, characterized in that: The switch is a field effect transistor.

7. The switching power supply circuit according to claim 1, wherein: The secondary rectifier circuit includes a rectifier diode and a rectifier capacitor. The positive electrode of the rectifier diode is connected to the first end of the secondary side of the converter, and the negative electrode of the rectifier diode is connected back to the second end of the secondary side of the converter through the rectifier capacitor.

8. The switching power supply circuit according to claim 1, wherein: The converter is a DC to DC transformer.

9. The switching power supply circuit according to claim 8, wherein: When the power switch is turned off, the absorption capacitor absorbs the turn-off voltage energy of the power switch and the leakage inductance voltage energy reflected from the secondary side of the DC-DC transformer to the primary side through the direct-connection path.

10. An electronic device, characterized in that: The electronic device includes the switching power supply circuit according to any one of claims 1 to 9.

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