Voltage conversion circuit

Abstract

The present invention provides a voltage conversion circuit. The voltage change circuit provided by the present invention includes a conversion circuit, a drive circuit, and a resonant circuit; the conversion circuit includes: a switch tube; the drain of the switch tube is connected to an input power supply; the drive circuit is connected to the source and gate of the switch tube, and the drive circuit is used to drive the on and off between the drain and source of the switch tube; the resonant circuit is connected to the drain and source of the switch tube, and the resonant circuit is used to control the current input to the drain of the switch tube to gradually increase when the drive circuit controls the opening between the drain and source of the switch tube, and is also used to control the voltage between the drain and source of the switch tube to gradually increase when the drive circuit controls the disconnection between the drain and source of the switch tube. The present invention reduces the switching loss of the switch tube and improves the efficiency of the conversion circuit.

Description

Technical Field

[0001] The invention relates to power electronic technology, and in particular to a voltage conversion circuit. Background Art

[0002] With the widespread application of electronic equipment, switching power supplies have been widely used in various fields. Among them, the DC switching power supply is a DC-DC converter, which has a conversion circuit, and the conversion circuit has a switch tube located between the input and output. The output DC voltage is controlled by adjusting the on-off ratio of the switch tube in the conversion circuit.

[0003] In the prior art, hard switching technology is used to control the on / off of the switch tube in the conversion circuit. When the switch tube is turned on, the current of the switch tube rises rapidly, and when the switch tube is turned off, the voltage of the switch tube rises rapidly, that is, during the on / off process of the switch tube, the current or voltage of the switch tube changes rapidly.

[0004] When the switch is turned on or off, the current and voltage will overlap. The current or voltage of the switch changes quickly, which will cause a large overlap of the current and voltage, resulting in large switching losses in the conversion equipment due to the overlap of current and voltage, and low conversion efficiency. Summary of the invention

[0005] The present invention provides a voltage conversion circuit to reduce the switching loss of a switch tube and improve the conversion efficiency.

[0006] The present invention provides a voltage conversion circuit, comprising: a conversion circuit, a drive circuit, and a resonance circuit;

[0007] The conversion circuit comprises: a switch tube; the drain of the switch tube is connected to the input power supply;

[0008] The driving circuit is connected to the source and gate of the switch tube, and is used to drive the on and off between the drain and source of the switch tube;

[0009] The resonant circuit is connected to the drain and source of the switching tube. The resonant circuit is used to control the current input to the drain of the switching tube to gradually increase when the driving circuit controls the drain and source of the switching tube to be turned on, and is also used to control the voltage between the drain and source of the switching tube to gradually increase when the driving circuit controls the drain and source of the switching tube to be turned off.

[0010] Optionally, the conversion circuit further includes: a freewheeling diode, a filter inductor, and a filter capacitor;

[0011] The source of the switch tube is connected to one end of the filter inductor, and the source of the switch tube is also connected to the negative electrode of the freewheeling diode;

[0012] The other end of the filter inductor is connected to one end of the filter capacitor; the positive electrode of the freewheeling diode is connected to the other end of the filter capacitor;

[0013] The other end of the filter capacitor is grounded.

[0014] Optionally, the resonant circuit includes a first resonant capacitor, a second resonant capacitor, a resonant inductor, a coupled inductor, a first auxiliary diode, a second auxiliary diode, and a third auxiliary diode;

[0015] One end of the first resonant capacitor is connected to the drain of the switch tube, the other end of the first resonant capacitor is connected to the positive electrode of the first auxiliary diode, and the other end of the first resonant capacitor is also connected to the negative electrode of the second auxiliary diode;

[0016] The cathode of the first auxiliary diode is connected to the source of the switch tube;

[0017] The anode of the second auxiliary diode is connected to the cathode of the third auxiliary diode, and the anode of the second auxiliary diode is also connected to one end of the second resonant capacitor;

[0018] The anode of the third auxiliary diode is connected to the anode of the freewheeling diode;

[0019] The other end of the second resonant capacitor is connected to the cathode of the freewheeling diode, and the other end of the second resonant capacitor is also connected to one end of the resonant inductor;

[0020] The other end of the resonant inductor is connected to one end of the coupling inductor; the other end of the coupling inductor is connected to one end of the filter inductor.

[0021] Optionally, the driving circuit includes: a first diode, a second diode, a third diode, a first resistor, a second resistor, and a third resistor;

[0022] The anode of the first diode is connected to the gate of the switch tube, and the cathode of the first diode is connected to the cathode of the second diode;

[0023] The anode of the second diode is connected to the source of the switch tube;

[0024] One end of the first resistor is connected to the anode of the first diode, the other end of the first resistor is connected to the anode of the second diode, and the other end of the first resistor is also connected to the voltage reference point;

[0025] One end of the second resistor is connected to one end of the first resistor, one end of the second resistor is connected to the anode of the third diode, the cathode of the third diode is connected to one end of the third resistor, and the other end of the third resistor is connected to the other end of the second resistor.

[0026] Optionally, the voltage conversion circuit further includes: a current sampling circuit and a voltage sampling circuit;

[0027] The current sampling circuit is connected to the conversion circuit and is used to sample the current of the conversion circuit;

[0028] The voltage sampling circuit is connected to the conversion circuit and is used for sampling the voltage of the conversion circuit.

[0029] Optionally, the current feedback circuit includes: a transformer, a fourth resistor, a fifth resistor, and a fourth diode;

[0030] One end of the primary side of the transformer is connected to the source of the switch tube, and the other end of the primary side of the transformer is connected to one end of the filter inductor;

[0031] One end of the secondary side of the transformer is connected in parallel with the fourth resistor;

[0032] The anode of the fourth diode is connected to one end of the fourth resistor, the cathode of the fourth diode is connected to one end of the fifth resistor, and the other end of the fifth resistor is grounded.

[0033] Optionally, the voltage sampling circuit includes: a sixth resistor, a seventh resistor, a fifth diode, and a sixth diode;

[0034] The sixth resistor and the seventh resistor are connected in series and then in parallel with the filter capacitor;

[0035] The fifth diode and the sixth diode are respectively connected in parallel with the sixth resistor.

[0036] Optionally, the voltage conversion circuit further includes: an eighth resistor, a first light emitting diode;

[0037] The eighth resistor and the first light emitting diode are connected in series and then connected in parallel with the filter capacitor.

[0038] Optionally, the voltage conversion circuit further includes: a ninth resistor and a second light emitting diode;

[0039] One end of the ninth resistor is connected to the drain of the switch tube, the other end of the ninth resistor is connected to the anode of the second light emitting diode, and the cathode of the second light emitting diode is grounded.

[0040] Optionally, the coupling inductor is mutually inductively coupled with the filter inductor.

[0041] The present invention provides a voltage conversion circuit. The circuit includes: a conversion circuit, a drive circuit, and a resonant circuit; the conversion circuit includes: a switch tube; the drain of the switch tube is connected to an input power supply; the drive circuit is connected to the source and gate of the switch tube, and the drive circuit is used to drive the on and off between the drain and source of the switch tube; the resonant circuit is connected to the drain and source of the switch tube, and the resonant circuit is used to control the current input to the drain of the switch tube to gradually increase when the drive circuit controls the on and off between the drain and source of the switch tube, and is also used to control the voltage between the drain and source of the switch tube to gradually increase when the drive circuit controls the off and on between the drain and source of the switch tube. The voltage conversion circuit provided by the present invention adds a resonant circuit on the basis of the conversion circuit, and the resonant circuit serves as a buffer circuit, so that the current or voltage of the switch tube gradually increases when the drive circuit controls the on and off of the switch tube, thereby reducing the switching loss of the switch tube and improving the efficiency of the conversion circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] 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, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 A schematic diagram of the structure of a voltage conversion circuit according to a first embodiment of the present invention;

[0044] Figure 2 This is a circuit diagram of Embodiment 2 of the voltage variation circuit provided by the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Figure 1 This is a schematic diagram of the structure of the voltage conversion circuit embodiment 1 provided by the present invention. Figure 1 As shown, the voltage conversion circuit of this embodiment may include: a conversion circuit 101 , a drive circuit 102 , and a resonant circuit 103 .

[0047] The conversion circuit 101 includes: a switch tube Q1; a drain of the switch tube Q1 is connected to an input bus DCBUS-IN of a direct current power supply.

[0048] The driving circuit 102 is connected to the source and gate of the switch tube Q1, and is used to drive the drain and source of the switch tube Q1 to be turned on and off. Specifically, the driving circuit receives a pulse signal from a control device, thereby driving the switch tube Q1 to be turned on and off. The control device may be a control chip for controlling the voltage conversion circuit.

[0049] The resonant circuit 103 is connected to the drain and source of the switch tube Q1. The resonant circuit 103 is used to control the current input to the drain of the switch tube Q1 to gradually increase when the drive circuit 102 controls the drain and source of the switch tube Q1 to be turned on. The resonant circuit 103 is also used to control the voltage between the drain and source of the switch tube Q1 to gradually increase when the drive circuit 102 controls the drain and source of the switch tube Q1 to be turned off.

[0050] Specifically, the resonant circuit 103 may include a capacitor and an inductor, and a buffer circuit is formed by the charging and discharging characteristics of the capacitor and the inductor to avoid a sudden increase in the current and voltage of the switch tube Q1.

[0051] The voltage conversion circuit provided in this embodiment includes: a conversion circuit, a drive circuit, and a resonant circuit. The conversion circuit includes: a switch tube; the drain of the switch tube is connected to the input power supply; the drive circuit is connected to the source and gate of the switch tube, and the drive circuit is used to drive the on and off between the drain and source of the switch tube; the resonant circuit is connected to the drain and source of the switch tube, and the resonant circuit is used to control the current input to the drain of the switch tube to gradually increase when the drive circuit controls the opening between the drain and source of the switch tube, and is also used to control the voltage between the drain and source of the switch tube to gradually increase when the drive circuit controls the disconnection between the drain and source of the switch tube. The voltage conversion circuit provided by the present invention adds a resonant circuit on the basis of the conversion circuit. The resonant circuit acts as a buffer circuit so that the current or voltage of the switch tube gradually increases when the drive circuit controls the on and off of the switch tube, thereby reducing the switching loss of the switch tube and improving the efficiency of the conversion circuit.

[0052] The technology used in the embodiment of the present invention to control the on or off of the switch tube is also called soft switching technology because the current changes slowly during the on process and the voltage changes slowly during the off process.

[0053] exist Figure 1 Based on the illustrated embodiment, the present invention can also provide a voltage conversion circuit. Figure 2 This is a circuit diagram of Embodiment 2 of the voltage variation circuit provided by the present invention.

[0054] like Figure 2 As shown, in Figure 1On the basis of the circuit shown, the conversion circuit 101 further includes: a freewheeling diode D11, a filter inductor L11, and a filter capacitor C11.

[0055] Specifically, in the conversion circuit 101 , the source of the switch tube Q1 is connected to one end of the filter inductor L11 , and the source of the switch tube Q1 is also connected to the cathode of the freewheeling diode D11 .

[0056] The other end of the filter inductor L11 is connected to one end of the filter capacitor C11, the positive electrode of the freewheeling diode D11 is connected to the other end of the filter capacitor C11, and the other end of the filter capacitor C11 is grounded.

[0057] The filter inductor L11 and the filter capacitor C11 form a low-pass filter.

[0058] Optionally, in practical applications, the filter capacitor C11 may include two capacitors, which are connected in parallel.

[0059] Optionally, the driving circuit 102 includes: a first diode D21, a second diode D22, a third diode D23, a first resistor R21, a second resistor R22, and a third resistor R23.

[0060] Specifically, in the driving circuit 102, the anode of the first diode D21 is connected to the gate of the switch tube Q1, and the cathode of the first diode D21 is connected to the cathode of the second diode D22. The anode of the second diode D22 is connected to the source of the switch tube Q1. The first diode D21 and the second diode D22 are used to perform feedforward protection on the switch tube Q1.

[0061] One end of the first resistor R21 is connected to the anode of the first diode D21 , the other end of the first resistor R21 is connected to the anode of the second diode D22 , and the other end of the first resistor R21 is also connected to the voltage reference point VSS.

[0062] One end of the second resistor R22 is connected to one end of the first resistor R21 , and one end of the second resistor R22 is connected to the anode of the third diode D23 .

[0063] A cathode of the third diode D23 is connected to one end of the third resistor R23 , and the other end of the third resistor R23 is connected to the other end of the second resistor R22 .

[0064] The first resistor R21 is a gate-source parallel resistor of the switch tube Q1, which can prevent the switch tube Q1 from being turned on by mistake. The connection point of the second resistor R22 and the third resistor R23 is connected to the output end of the control device, and the output end of the control device is used to output a pulse signal PWM for controlling the on-off of the switch tube Q1. The control device can be a control chip for controlling the voltage conversion circuit.

[0065] Optionally, the resonant circuit 103 includes: a first resonant capacitor C31, a second resonant capacitor C32, a resonant inductor L31, a coupling inductor L32, a first auxiliary diode D31, a second auxiliary diode D32, and a third auxiliary diode.

[0066] Specifically, in the resonant circuit 103, one end of the first resonant capacitor C31 is connected to the drain of the switch tube Q1, the other end of the first resonant capacitor C31 is connected to the anode of the first auxiliary diode D31, and the other end of the first resonant capacitor C31 is also connected to the cathode of the second auxiliary diode D32.

[0067] The cathode of the first auxiliary diode D31 is connected to the source of the switch tube Q1 .

[0068] The anode of the second auxiliary diode D32 is connected to the cathode of the third auxiliary diode D33 , and the anode of the second auxiliary diode D32 is also connected to one end of the second resonant capacitor C32 .

[0069] An anode of the third auxiliary diode D33 is connected to an anode of the freewheeling diode D11 .

[0070] The other end of the second resonant capacitor C32 is connected to the cathode of the freewheeling diode D11 , and the other end of the second resonant capacitor C32 is also connected to one end of the resonant inductor L31 .

[0071] The other end of the resonant inductor L31 is connected to one end of the coupling inductor L32 ; the other end of the coupling inductor L32 is connected to one end of the filter inductor L11 .

[0072] Optionally, the coupling inductor L32 is mutually coupled with the filter inductor L11. The mutual coupling between the coupling inductor L32 and the filter inductor L11 can accelerate the resonance process when the switch tube Q1 is turned on and off, making the switch tube Q1 turn on and off faster.

[0073] Preferably, in this embodiment, the resonant inductor L31 is an inductor independent of the coupling inductor L32 and the filter inductor L11 , which can reduce the heat generation of the inductor in practical applications.

[0074] Figure 2 The working process of the circuit shown when the switch tube Q1 is turned on and off is:

[0075] When the switch tube Q1 switches from off to on, the presence of the resonant inductor L31 greatly suppresses the reverse recovery of the freewheeling diode D11, causing the current of the freewheeling diode D11 to rise slowly and linearly, thereby causing the current of the switch tube Q1 to rise slowly and linearly, so that the switch tube Q1 obtains the zero current switch (ZCS) condition.

[0076] When the reverse recovery of the freewheeling diode D11 is completed, the first resonant capacitor C31, the second resonant capacitor C32, and the resonant inductor L31 form a resonant circuit through the switch tube Q1 and the second auxiliary diode D32, and begin to resonate. In this process, the first resonant capacitor C31 is discharged, and the second resonant capacitor C32 is charged. When the voltage on the first resonant capacitor C31 drops to zero, the switch tube Q1 obtains the zero voltage switch (ZVS) condition.

[0077] When the voltage of the first resonant capacitor C31 is zero, the first auxiliary diode D31 is turned on, and the resonant inductor L31 and the second resonant capacitor C32 form a loop through the second auxiliary diode D32 and the first auxiliary diode D31, and begin to resonate. The electric energy of the resonant inductor L31 is transferred to the second resonant capacitor C32, and when the current on the resonant inductor L31 drops to zero, the resonance process ends.

[0078] When the switch tube Q1 is turned off, due to the existence of the first resonant capacitor C31, the drain-source voltage of the switch tube Q1 rises slowly, thereby achieving ZVS turn-off.

[0079] When the first resonant capacitor C31 reaches a certain value, the third auxiliary diode D33 is turned on, and the second resonant capacitor C32 and the resonant inductor L31 resonantly discharge, so that the current of the coupling inductor L32 continues to increase, and the first resonant capacitor C31 continues to charge, and at this stage, the voltage of the first resonant capacitor C31 gradually rises to the voltage of the input power supply DC-BUSIN, thereby ensuring that the switch tube Q1 realizes ZCS opening in the next switching cycle.

[0080] When the voltage of the first resonant capacitor C31 rises to the voltage of the input power supply DC-BUSIN, the second resonant capacitor C32 and the resonant inductor L31 continue to resonate.

[0081] When the voltage of the second resonant capacitor C32 is zero, the third auxiliary diode D33 is turned off, the freewheeling diode D11 is turned on, and then the next cycle process is entered.

[0082] The voltage conversion circuit provided in this embodiment has Figure 1 On the basis of the embodiment shown, the resonant circuit includes a first resonant capacitor, a second resonant capacitor, a resonant inductor, a coupled inductor, a first auxiliary diode, a second auxiliary diode and a third auxiliary diode. Through the charging and discharging of the resonant capacitors and the resonant inductor in the resonant circuit, the current input to the drain of the switch tube gradually increases when the drive circuit controls the switch tube to turn on, and the voltage between the drain and the source of the switch tube gradually increases when the drive circuit controls the switch tube to turn off, thereby reducing the switching loss of the switch tube and improving the conversion efficiency.

[0083] Continue to refer to Figure 2The present invention can also provide a voltage conversion circuit, which, based on the above embodiment, also includes: a current sampling circuit 104 and a voltage sampling circuit 105.

[0084] The current sampling circuit 104 is connected to the conversion circuit 101 and is used to sample the current of the conversion circuit 101. The voltage sampling circuit 105 is connected to the conversion circuit 101 and is used to sample the voltage of the conversion circuit 101. The current signal and the voltage signal obtained by the current sampling circuit 104 and the voltage sampling circuit 105 can realize the double closed-loop control of the voltage conversion circuit.

[0085] Optionally, the current sampling circuit 104 includes: a transformer L4, a fourth resistor R41, a fifth resistor R42, and a fourth diode D41.

[0086] Specifically, one end of the primary side of the transformer L4 is connected to the source of the switch tube Q1 , and the other end of the primary side of the transformer L4 is connected to one end of the filter inductor L11 .

[0087] The secondary side of the transformer L4 is connected in parallel with the fourth resistor R41.

[0088] An anode of the fourth diode D41 is connected to one end of the fourth resistor R41 , a cathode of the fourth diode D41 is connected to one end of the fifth resistor R42 , and the other end of the fifth resistor R42 is grounded.

[0089] Optionally, the fourth resistor R41 may include a plurality of resistors connected in parallel. The fifth resistor R42 may include a plurality of resistors connected in parallel.

[0090] The current signal at one end of the fifth resistor R42 is a sampling current signal CS. The sampling current signal CS can be fed back to the control device.

[0091] The transformation ratio between the primary side and the secondary side of the transformer L4 can be set according to actual needs.

[0092] Optionally, the voltage sampling circuit 105 includes: a sixth resistor R51, a seventh resistor R52, a fifth diode D51, and a sixth diode D52.

[0093] Specifically, the sixth resistor R51 and the seventh resistor R52 are connected in series and then connected in parallel with the filter capacitor C11.

[0094] The fifth diode D51 and the sixth diode D52 are respectively connected in parallel with the sixth resistor R51.

[0095] Optionally, the seventh resistor R52 may include a plurality of resistors, and the seventh resistor R52 is used to divide the output voltage DC-BUS of the voltage conversion circuit. The voltage signal of the sixth resistor R51 is a sampled voltage signal FB. The sampled voltage signal FB may be fed back to the control device.

[0096] The control device implements double closed-loop control of the voltage conversion circuit by sampling the current signal CS and the voltage signal FB.

[0097] The voltage conversion circuit provided in this embodiment further includes a current sampling circuit and a voltage sampling circuit on the basis of the above-mentioned embodiment. The output current signal and voltage signal obtained by the current sampling circuit and the voltage sampling circuit can realize double closed-loop control of the voltage conversion circuit, so as to stabilize the output of the voltage conversion circuit and improve the conversion efficiency.

[0098] Continue to refer to Figure 2 The present invention can also provide a voltage conversion circuit. Based on the above embodiment, the voltage conversion circuit further includes: an eighth resistor R61 and a first light emitting diode D61.

[0099] The eighth resistor R61 and the first light emitting diode D61 are connected in series and then connected in parallel with the filter capacitor.

[0100] Optionally, the voltage conversion circuit also includes: a ninth resistor R71 and a second light emitting diode D71.

[0101] One end of the ninth resistor R71 is connected to the drain of the switch tube Q1 , the other end of the ninth resistor R71 is connected to the anode of the second light emitting diode D71 , and the cathode of the second light emitting diode D71 is grounded.

[0102] The voltage conversion circuit provided in this embodiment further includes a first light-emitting diode and a second light-emitting diode on the basis of the above embodiment. The input end and the voltage state of the input end of the voltage conversion circuit can be intuitively displayed through the two light-emitting diodes, which is more practical.

[0103] The terms "first", "second", and "third" etc. of the various parts of the embodiments of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0104] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0105] In the description of the present invention, it should be understood that the terms "including" and "having" and any variations thereof used herein are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0106] In the description of this specification, the description with reference to the term "example" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0107] Those skilled in the art can understand that all or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, disk or optical disk and other media that can store program codes.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A voltage conversion circuit, characterized in that: include: Conversion circuit, drive circuit, resonant circuit; The conversion circuit comprises: a switch tube; the drain of the switch tube is connected to the input power supply; The driving circuit is connected to the source and gate of the switch tube, and the driving circuit is used to drive the on and off between the drain and source of the switch tube; The resonant circuit is connected to the drain and source of the switch tube, and the resonant circuit is used to control the current input to the drain of the switch tube to gradually increase when the drive circuit controls the drain and source of the switch tube to be turned on, and is also used to control the voltage between the drain and source of the switch tube to gradually increase when the drive circuit controls the drain and source of the switch tube to be turned off; The driving circuit comprises: a first diode, a second diode, a third diode, a first resistor, a second resistor, and a third resistor; The anode of the first diode is connected to the gate of the switch tube, and the cathode of the first diode is connected to the cathode of the second diode; The anode of the second diode is connected to the source of the switch tube; One end of the first resistor is connected to the anode of the first diode, the other end of the first resistor is connected to the anode of the second diode, and the other end of the first resistor is also connected to a voltage reference point; One end of the second resistor is connected to one end of the first resistor, one end of the second resistor is connected to the positive electrode of the third diode, the negative electrode of the third diode is connected to one end of the third resistor, and the other end of the third resistor is connected to the other end of the second resistor; the connection point of the second resistor and the third resistor is connected to the output end of the control device, and the output end of the control device is used to output a pulse signal PWM for controlling the on and off of the switch tube; The voltage conversion circuit also includes: a current sampling circuit and a voltage sampling circuit; The current sampling circuit is connected to the conversion circuit and is used to sample the current of the conversion circuit; The voltage sampling circuit is connected to the conversion circuit and is used to sample the voltage of the conversion circuit; The control device performs double closed-loop control on the voltage conversion circuit through the sampled current signal of the current sampling circuit and the sampled voltage signal of the voltage sampling circuit; The conversion circuit also includes: a freewheeling diode, a filter inductor, and a filter capacitor; The source of the switch tube is connected to one end of the filter inductor, and the source of the switch tube is also connected to the cathode of the freewheeling diode; The other end of the filter inductor is connected to one end of the filter capacitor; the positive electrode of the freewheeling diode is connected to the other end of the filter capacitor; The other end of the filter capacitor is grounded; The current sampling circuit includes: a transformer, a fourth resistor, a fifth resistor, and a fourth diode; One end of the primary side of the transformer is connected to the source of the switch tube, and the other end of the primary side of the transformer is connected to one end of the filter inductor; One end of the secondary side of the transformer is connected in parallel with the fourth resistor; The anode of the fourth diode is connected to one end of the fourth resistor, the cathode of the fourth diode is connected to one end of the fifth resistor, and the other end of the fifth resistor is grounded; The voltage sampling circuit comprises: a sixth resistor, a seventh resistor, a fifth diode, and a sixth diode; The sixth resistor and the seventh resistor are connected in series and then in parallel with the filter capacitor; The fifth diode and the sixth diode are respectively connected in parallel with the sixth resistor.

2. The voltage conversion circuit according to claim 1, characterized in that: The resonant circuit includes a first resonant capacitor, a second resonant capacitor, a resonant inductor, a coupled inductor, a first auxiliary diode, a second auxiliary diode, and a third auxiliary diode; One end of the first resonant capacitor is connected to the drain of the switch tube, the other end of the first resonant capacitor is connected to the anode of the first auxiliary diode, and the other end of the first resonant capacitor is also connected to the cathode of the second auxiliary diode; The cathode of the first auxiliary diode is connected to the source of the switch tube; The anode of the second auxiliary diode is connected to the cathode of the third auxiliary diode, and the anode of the second auxiliary diode is also connected to one end of the second resonant capacitor; The anode of the third auxiliary diode is connected to the anode of the freewheeling diode; The other end of the second resonant capacitor is connected to the cathode of the freewheeling diode, and the other end of the second resonant capacitor is also connected to one end of the resonant inductor; The other end of the resonant inductor is connected to one end of the coupling inductor; the other end of the coupling inductor is connected to one end of the filter inductor; The resonant inductor is used to suppress the reverse recovery of the freewheeling diode when the switch tube is turned from off to on, so that the current of the freewheeling diode rises slowly and linearly, thereby making the current of the switch tube rise slowly, so that the switch tube obtains the condition of zero current switching; The resonant inductor is also used to resonate with the first resonant capacitor, the second resonant capacitor, the switch tube and the second auxiliary diode to form a resonant circuit after the reverse recovery of the freewheeling diode ends; during the resonance process of the resonant circuit, the first resonant capacitor is discharged and the second resonant capacitor is charged, so that when the voltage on the first resonant capacitor drops to zero, the switch tube obtains a zero voltage shutdown condition.

3. The voltage conversion circuit according to claim 1, characterized in that: The voltage conversion circuit further includes: an eighth resistor and a first light emitting diode; The eighth resistor and the first light emitting diode are connected in series and then connected in parallel with the filter capacitor.

4. The voltage conversion circuit according to claim 1, characterized in that: The voltage conversion circuit further includes: a ninth resistor and a second light emitting diode; One end of the ninth resistor is connected to the drain of the switch tube, the other end of the ninth resistor is connected to the anode of the second light emitting diode, and the cathode of the second light emitting diode is grounded.

5. The voltage conversion circuit according to claim 2, characterized in that: The coupling inductor and the filter inductor are mutually coupled.

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