Switch control circuit and power supply equipment

Abstract

The present application is applicable to the field of power electronics technology, and provides a switch control circuit and a power supply device, including a first switch tube, a second switch tube, a first pulse transformer, a second pulse transformer, a first drive circuit and a second drive circuit. In the above-mentioned switch control circuit, two pulse transformers and two drive circuits are used to drive the two switch tubes respectively, which can improve the flexibility and safety of the switch tube control. When the switch control circuit is working in a non-power conversion state, the drive circuit presets a negative voltage to the control end of the switch tube to ensure that the switch tube maintains a reliable shutdown state; and when the switch control circuit is working in a power conversion state, the drive circuit applies a set pulse signal to the control end of the switch tube to ensure that the drive voltage of the switch tube is negative during the shutdown process, prompting the switch tube to shut down quickly, and effectively preventing the switch tube from being mis-turned on due to the Miller effect.

Description

Technical Field

[0001] The present application belongs to the field of power electronics technology, and in particular, relates to a switch control circuit and a power supply device. Background Art

[0002] As an important core device in power electronic products, the working state of semiconductor power switch tubes determines the key performance indicators of the products. The working state of the power switch tube is determined by its gate drive circuit. The requirements for the gate drive circuit are: to form the smallest possible on-resistance when the switch tube is turned on, and to form the largest possible open-circuit resistance when it is turned off, in order to achieve the ideal switching characteristics. However, due to the physical properties of semiconductors and the limitations of the switch tube gate drive circuit structure, in fact, the power switch tube cannot achieve the ideal switching characteristics. Since the physical properties of semiconductors cannot be changed, the design of the switch tube gate drive circuit structure can only be optimized.

[0003] Figure 1 and Figure 2 The circuit shown is a common switch tube gate drive circuit. When the switch tube is in the off state where the system is not performing power conversion, its gate voltage is non-negative. Due to the Miller effect, it is easy to reach the threshold voltage that makes it turn on, causing the switch tube to be mis-turned on, resulting in damage to the switch tube and other components, reducing the reliability and safety of the system operation. Summary of the invention

[0004] The embodiments of the present application provide a switch control circuit and a power supply device, which can solve the problem that the switch tube in the gate drive circuit is disturbed and mis-conducted, resulting in damage to the switch tube and other components.

[0005] In a first aspect, an embodiment of the present application provides a switch control circuit, including:

[0006] A first switch tube, a high potential end of which is connected to the power signal, and a low potential end of which is used to be connected to the first end of the primary winding of the main power transformer;

[0007] A second switch tube, whose high potential end is used to be connected to the second end of the primary winding of the main power transformer, and whose low potential end is grounded;

[0008] A first pulse transformer, whose primary winding is used to receive a first pulse signal;

[0009] A second pulse transformer, whose primary winding is used to receive a second pulse signal;

[0010] a first drive circuit, wherein a first end thereof is connected to a like-name end of a secondary winding of the first pulse transformer, a second end thereof is connected to an opposite-name end of a secondary winding of the first pulse transformer, a third end thereof is connected to a control end of the first switch tube, and a fourth end thereof is connected to a low potential end of the first switch tube, the first drive circuit being used to access an induced voltage of the secondary winding of the first pulse transformer to provide the first switch tube with a positive drive voltage for turning on the first switch tube and a negative drive voltage for turning off the first switch tube; and

[0011] A second drive circuit, a first end of which is connected to the same-name end of the secondary winding of the second pulse transformer, a second end of which is connected to the opposite-name end of the secondary winding of the second pulse transformer, a third end of which is connected to the control end of the second switch tube, and a fourth end of which is connected to the low-potential end of the second switch tube. The second drive circuit is used to access the induced voltage of the secondary winding of the second pulse transformer to provide the second switch tube with a positive drive voltage for turning on the second switch tube and a negative drive voltage for turning off the second switch tube.

[0012] In a possible implementation manner of the first aspect, the switch control circuit further includes a first signal source connected to the primary winding of the first pulse transformer and a second signal source connected to the primary winding of the second pulse transformer;

[0013] When the output power of the main power transformer is zero and the first pulse signal output by the first signal source is at a high level, the second pulse signal output by the second signal source is at a low level.

[0014] In a possible implementation of the first aspect, when the output power of the main power transformer is zero and the first pulse signal output by the first signal source is at a low level, the second pulse signal output by the second signal source is at a high level or a low level.

[0015] In a possible implementation manner of the first aspect, the first driving circuit includes a first resistor, a second resistor, and a first voltage stabilizing module;

[0016] The first end of the first resistor is connected to the same-name end of the secondary winding of the first pulse transformer as the first end of the first drive circuit, the second end of the first resistor is connected to the control end of the first switch tube as the third end of the first drive circuit, the first end of the first voltage stabilizing module is connected to the opposite-name end of the secondary winding of the first pulse transformer as the second end of the first drive circuit, the second end of the first voltage stabilizing module is connected to the low-potential end of the first switch tube as the fourth end of the first drive circuit, the first end of the second resistor is connected to the second end of the first resistor, and the second end of the second resistor is connected to the first end of the first voltage stabilizing module.

[0017] In a possible implementation manner of the first aspect, the first voltage stabilizing module includes a first voltage stabilizing diode and a first capacitor;

[0018] The anode of the first voltage stabilizing diode is connected to the second end of the second resistor as the first end of the first voltage stabilizing module, the cathode of the first voltage stabilizing diode is connected to the low potential end of the first switching tube as the second end of the first voltage stabilizing module, and the first capacitor is connected in parallel with the first voltage stabilizing diode.

[0019] In a possible implementation manner of the first aspect, the second driving circuit includes a third resistor, a fourth resistor, and a second voltage stabilization module;

[0020] The first end of the third resistor is connected to the same-name end of the secondary winding of the second pulse transformer as the first end of the second drive circuit, the second end of the third resistor is connected to the control end of the second switch tube as the third end of the second drive circuit, the first end of the second voltage stabilizing module is connected to the opposite-name end of the secondary winding of the second pulse transformer as the second end of the second drive circuit, the second end of the second voltage stabilizing module is connected to the low-potential end of the second switch tube as the fourth end of the second drive circuit, the first end of the fourth resistor is connected to the second end of the third resistor, and the second end of the fourth resistor is connected to the first end of the second voltage stabilizing module.

[0021] In a possible implementation manner of the first aspect, the second voltage stabilizing module includes a second voltage stabilizing diode and a second capacitor;

[0022] The anode of the second voltage stabilizing diode is connected to the second end of the fourth resistor as the first end of the second voltage stabilizing module, the cathode of the second voltage stabilizing diode is connected to the low potential end of the second switch tube as the second end of the second voltage stabilizing module, and the second capacitor is connected in parallel with the second voltage stabilizing diode.

[0023] In a possible implementation manner of the first aspect, the primary winding of the first pulse transformer and the primary winding of the second pulse transformer are grounded to a common ground.

[0024] In a possible implementation manner of the first aspect, the first switch tube and the second switch tube are MOS tubes, or the first switch tube and the second switch tube are IGBTs.

[0025] In a second aspect, an embodiment of the present application provides a power supply device, comprising a switch control circuit as described in any one of the above-mentioned first aspects.

[0026] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0027] The above switch control circuit uses two pulse transformers and two drive circuits to drive two switch tubes respectively, which can improve the flexibility and safety of switch tube control. When the switch control circuit works in the non-power conversion state, the drive circuit presets a negative voltage on the control end of the switch tube to ensure that the switch tube maintains a reliable shutdown state; when the switch control circuit works in the power conversion state, the drive circuit applies a set pulse signal to the control end of the switch tube to ensure that the drive voltage of the switch tube is negative during the shutdown process, prompting the switch tube to shut down quickly, effectively preventing the switch tube from being mis-turned on due to the Miller effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0029] Figure 1 It is a schematic diagram of the structure of a traditional switch tube gate drive circuit;

[0030] Figure 2 It is a schematic diagram of the structure of another traditional switch tube gate drive circuit;

[0031] Figure 3 is a structural schematic diagram of a switch control circuit provided in an embodiment of the present application;

[0032] Figure 4 is a timing diagram of a first pulse signal and a second pulse signal when a switch control circuit provided by an embodiment of the present application is in a power conversion state;

[0033] Figure 5 This is a timing diagram of a first pulse signal and a second pulse signal when a switch control circuit provided in an embodiment of the present application is in a non-power conversion state. DETAILED DESCRIPTION

[0034] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0035] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0036] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0037] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0038] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0039] In order to illustrate the technical solution described in this application, a specific embodiment is provided below for illustration.

[0040] Figure 3 A structural schematic diagram of a switch control circuit provided in an embodiment of the present application is shown. The switch control circuit may include a first switch tube M1, a second switch tube M2, a first pulse transformer T1, a second pulse transformer T2, a first drive circuit 100 and a second drive circuit 200.

[0041] The high potential end of the first switch tube M1 is connected to the power supply signal, and the low potential end is used to connect to the first end of the primary winding of the main power transformer T3. The high potential end of the second switch tube M2 is used to connect to the second end of the primary winding of the main power transformer T3, and the low potential end is grounded. The primary winding of the first pulse transformer T1 is used to access the first pulse signal VDRV1; the primary winding of the second pulse transformer T2 is used to access the second pulse signal VDRV2.

[0042] The first end of the first drive circuit 100 is connected to the same-name end of the secondary winding of the first pulse transformer T1, the second end of the first drive circuit 100 is connected to the opposite-name end of the secondary winding of the first pulse transformer T1, the third end of the first drive circuit 100 is connected to the control end of the first switch tube M1, and the fourth end of the first drive circuit 100 is connected to the low potential end of the first switch tube M1. The first drive circuit 100 is used to access the induced voltage of the secondary winding of the first pulse transformer T1 to provide the first switch tube M1 with a positive drive voltage to turn on the first switch tube M1 and a negative drive voltage to turn off the first switch tube M1.

[0043] The first end of the second drive circuit 200 is connected to the same-name end of the secondary winding of the second pulse transformer T2, the second end of the second drive circuit 200 is connected to the opposite-name end of the secondary winding of the second pulse transformer T2, the third end of the second drive circuit 200 is connected to the control end of the second switch tube M2, and the fourth end of the second drive circuit 200 is connected to the low potential end of the second switch tube M2. The second drive circuit 200 is used to access the induced voltage of the secondary winding of the second pulse transformer T2 to provide the second switch tube M2 with a positive drive voltage to turn on the second switch tube M2 and a negative drive voltage to turn off the second switch tube M2.

[0044] Specifically, the first switch tube M1 and the second switch tube M2 jointly drive the main power transformer T3. When the first switch tube M1 and the second switch tube M2 are turned on at the same time, current will flow through the primary winding of the main power transformer T3 to drive the main power transformer T3 to work (output power).

[0045] When the first pulse signal VDRV1 changes from a low level to a high level, the secondary winding of the first pulse transformer T1 induces a high level pulse into the first drive circuit 100, and the first drive circuit 100 applies a positive drive voltage (the positive drive voltage is greater than the threshold voltage of the first switch tube M1) to the gate of the first switch tube M1, so that the first switch tube M1 is turned on; when the first pulse signal VDRV1 changes from a high level to a low level, the secondary winding of the first pulse transformer T1 is equivalent to a wire, and at this time, the first drive circuit 100 applies a negative drive voltage (a voltage less than zero) to the gate of the first switch tube M1, and the first switch tube M1 is turned off. The working principle of the second switch tube M2 is the same as that of the first switch tube M1. When the second switch tube M2 is turned off, the signal applied by the second drive circuit 200 to the gate of the second switch tube M2 is also a negative drive voltage (a voltage less than zero).

[0046] When the first switch tube M1 is turned off, due to the existence of Miller capacitance, the gate voltage of the second switch tube M2 will be raised, and the faster the switch is turned off, the higher the gate voltage of the second switch tube M2 will be raised. When the gate voltage of the second switch tube M2 is turned off at 0V, the raised voltage may exceed the threshold voltage and turn on the second switch tube M2. At this time, the second switch tube M2 will be mis-turned on. The voltage at which the second switch tube M2 in the switch control circuit is turned off is a negative voltage, and the raised voltage can offset the negative voltage, so that the gate voltage of the second switch tube M2 is difficult to be raised to the threshold voltage, thereby avoiding the risk of the second switch tube M2 being mis-turned on. In addition, negative voltage is used for shutdown, and the existence of negative voltage during shutdown makes the shutdown speed faster, which can reduce the shutdown loss. At the same time, two pulse transformers are used to drive the two switch tubes respectively to ensure that the two drive signals (the first pulse signal VDRV1 and the second pulse signal VDRV2) do not affect each other. When the switch control circuit works in the non-power conversion state, the first pulse signal VDRV1 applied to the first switch tube M1 and the second pulse signal VDRV2 applied to the second switch tube M2 are asynchronous signals, realizing the pre-made negative voltage at the control end of the first switch tube M1 and the second switch tube M2, while ensuring that the first switch tube M1 and the second switch tube M2 will not be turned on at the same time, and the main power transformer T3 has no power output.

[0047] In one embodiment of the present application, the first driving circuit 100 may include a first resistor R1, a second resistor R2 and a first voltage stabilizing module 110. The first end of the first resistor R1 is connected to the same-name end of the secondary winding of the first pulse transformer T1 as the first end of the first driving circuit 100, the second end of the first resistor R1 is connected to the control end of the first switch tube M1 as the third end of the first driving circuit 100, the first end of the first voltage stabilizing module 110 is connected to the opposite-name end of the secondary winding of the first pulse transformer T1 as the second end of the first driving circuit 100, the second end of the first voltage stabilizing module 110 is connected to the low-potential end of the first switch tube M1 as the fourth end of the first driving circuit 100, the first end of the second resistor R2 is connected to the second end of the first resistor R1, and the second end of the second resistor R2 is connected to the first end of the first voltage stabilizing module 110.

[0048] Specifically, when the first pulse signal VDRV1 changes from a low level to a high level, the secondary winding of the first pulse transformer T1 induces a high level pulse, and charges the capacitor between the gate and the source of the first switch tube M1 through the first resistor R1. When the voltage between the gate and the source of the first switch tube M1 is greater than the threshold voltage, the first switch tube M1 is turned on, and the first voltage stabilizing module 110 stores negative voltage potential energy at this time; when the first pulse signal VDRV1 changes from a high level to a low level, the secondary winding of the first pulse transformer T1 is equivalent to a wire, and the negative voltage potential energy of the first voltage stabilizing module 110 is loaded between the gate and the source of the first switch tube M1, so that the voltage on the gate of the first switch tube M1 is less than the voltage on the source, so that the first switch tube M1 forms a negative driving voltage (the voltage on the gate of the first switch tube M1 is less than the voltage on the source) and is turned off.

[0049] In one embodiment of the present application, the first voltage stabilizing module 110 may include a first voltage stabilizing diode Z1 and a first capacitor C1. The anode of the first voltage stabilizing diode Z1 is connected to the second end of the second resistor R2 as the first end of the first voltage stabilizing module 110, the cathode of the first voltage stabilizing diode Z1 is connected to the low potential end of the first switch tube M1 as the second end of the first voltage stabilizing module 110, and the first capacitor C1 is connected in parallel with the first voltage stabilizing diode Z1.

[0050] Specifically, when the first pulse signal VDRV1 changes from a low level to a high level, the secondary winding of the first pulse transformer T1 induces a high level pulse, and charges the capacitor between the gate and the source of the first switch tube M1 through the first resistor R1. When the voltage between the gate and the source of the first switch tube M1 is greater than the threshold voltage, the first switch tube M1 is turned on, and the first capacitor C1 is charged at this time. Finally, the voltage across the first capacitor C1 is the same as the stabilization value of the first voltage-stabilizing diode Z1; when the first pulse signal VDRV1 changes from a high level to a low level, the secondary winding of the first pulse transformer T1 is equivalent to a wire, and the first end of the first capacitor C1 is at the same potential as the gate of the first switch tube M1, and the second end of the first capacitor C1 is at the same potential as the source of the first switch tube M1. At this time, the gate voltage of the first switch tube M1 is less than the source voltage, and the first switch tube M1 forms a negative driving voltage (the gate voltage of the first switch tube M1 is less than the source voltage) and is turned off.

[0051] In one embodiment of the present application, the second driving circuit 200 may include a third resistor R3, a fourth resistor R4, and a second voltage stabilizing module 210. The first end of the third resistor R3 is connected to the same-name end of the secondary winding of the second pulse transformer T2 as the first end of the second driving circuit 200, the second end of the third resistor R3 is connected to the control end of the second switch tube M2 as the third end of the second driving circuit 200, the first end of the second voltage stabilizing module 210 is connected to the opposite-name end of the secondary winding of the second pulse transformer T2 as the second end of the second driving circuit 200, the second end of the second voltage stabilizing module 210 is connected to the low potential end of the second switch tube M2 as the fourth end of the second driving circuit 200, the first end of the fourth resistor R4 is connected to the second end of the third resistor R3, and the second end of the fourth resistor R4 is connected to the first end of the second voltage stabilizing module 210.

[0052] Specifically, when the second pulse signal VDRV2 changes from a low level to a high level, the secondary winding of the second pulse transformer T2 induces a high level pulse, and charges the capacitor between the gate and the source of the second switch tube M2 through the third resistor R3. When the voltage between the gate and the source of the second switch tube M2 is greater than the threshold voltage, the second switch tube M2 is turned on, and the second voltage stabilizing module 210 stores negative voltage potential energy. When the second pulse signal VDRV2 changes from a high level to a low level, the secondary winding of the second pulse transformer T2 is equivalent to a wire. At this time, the negative voltage potential energy of the second voltage stabilizing module 210 is loaded between the gate and the source of the second switch tube M2, so that the voltage on the gate of the second switch tube M2 is less than the voltage on the source, so that the second switch tube M2 forms a negative driving voltage (the voltage on the gate of the second switch tube M2 is less than the voltage on the source) and is turned off.

[0053] In one embodiment of the present application, the second voltage stabilizing module 210 may include a second voltage stabilizing diode Z2 and a second capacitor C2. The anode of the second voltage stabilizing diode Z2 is connected to the second end of the fourth resistor R4 as the first end of the second voltage stabilizing module 210, the cathode of the second voltage stabilizing diode Z2 is connected to the low potential end of the second switch tube M2 as the second end of the second voltage stabilizing module 210, and the second capacitor C2 is connected in parallel with the second voltage stabilizing diode Z2.

[0054] Specifically, when the second pulse signal VDRV2 changes from a low level to a high level, the secondary winding of the second pulse transformer T2 induces a high level pulse, and charges the capacitor between the gate and the source of the second switch tube M2 through the third resistor R3. When the voltage between the gate and the source of the second switch tube M2 is greater than the threshold voltage, the second switch tube M2 is turned on, and the second capacitor C2 is charged at this time. Finally, the voltage across the second capacitor C2 is the same as the stabilization value of the second voltage-stabilizing diode Z2; when the second pulse signal VDRV2 changes from a high level to a low level, the secondary winding of the second pulse transformer T2 is equivalent to a wire, and the first end of the second capacitor C2 is at the same potential as the gate of the second switch tube M2, and the second end of the second capacitor C2 is at the same potential as the source of the second switch tube M2. At this time, the gate voltage of the second switch tube M2 is less than the source voltage, and the second switch tube M2 forms a negative driving voltage (the voltage of the gate of the second switch tube M2 is less than the voltage of the source) and is turned off.

[0055] In one embodiment of the present application, the primary winding of the first pulse transformer T1 and the primary winding of the second pulse transformer T2 are connected to a common ground.

[0056] Specifically, the common grounding of the primary windings of the two pulse transformers can reduce the number of primary power supplies and reduce the complexity and cost of the switch control circuit.

[0057] In an embodiment of the present application, the first switch tube M1 and the second switch tube M2 are MOS tubes or IGBTs. In addition to MOS tubes or IGBTs, the first switch tube M1 and the second switch tube M2 may also be other power switch devices.

[0058] The switch control circuit has two states, namely, a non-power conversion state (the main power transformer T3 has no output power) and a power conversion state (the main power transformer T3 has output power).

[0059] When the switch control circuit is in the power conversion state, the first pulse signal VDRV1 output by the first signal source and the second pulse signal VDRV2 output by the second signal source are synchronization signals (such as Figure 4 As shown), the first switch tube M1 and the second switch tube M2 are driven to be turned on or off synchronously, thereby driving and adjusting the output power of the main power transformer T3.

[0060] When the switch control circuit is in a non-power conversion state, the output power of the main power transformer T3 is zero. At this time, the first switch tube M1 and the second switch tube M2 cannot be turned on at the same time. When the output power of the main power transformer T3 is zero, the first switch tube M1 and the second switch tube M2 cannot be turned on at the same time. When the first pulse signal VDRV1 output by the first signal source is high, the second pulse signal VDRV2 output by the second signal source is low; when the first pulse signal VDRV1 output by the first signal source is low, the second pulse signal VDRV2 output by the second signal source is high or low (such as Figure 5 shown).

[0061] When the switch control circuit is in a non-power conversion state, the first pulse signal VDRV1 drives the first switch tube M1 to be periodically turned on and off, and the second pulse signal VDRV2 drives the second switch tube M2 to be periodically turned on and off. Under the premise of ensuring that the output power of the main power transformer T3 is zero, a preset negative voltage can be continuously present on the first capacitor C1 and the second capacitor C2 to prepare for power output. When the switch control circuit changes from a non-power conversion state to a power conversion state, the negative voltage shutdown of the switch tube during the shutdown period can be achieved at the beginning of the first switching cycle.

[0062] The above switch control circuit can be applied to topology circuits such as dual-tube forward, full-bridge or half-bridge to improve the stability and safety of topology circuits such as dual-tube forward, full-bridge or half-bridge.

[0063] The present application also discloses a power supply device, which may include the switch control circuit described above.

[0064] Specifically, the power supply equipment can be an inverter welding power supply, a UPS power supply, a three-phase or single-phase grid-connected inverter power supply, and a frequency converter, etc. The power supply equipment using the switch control circuit can effectively prevent the switch tube from being misconnected, thereby improving the stability and safety of the power supply equipment.

[0065] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A switch control circuit, characterized in that: include: A first switch tube, a high potential end of which is connected to the power signal, and a low potential end of which is used to be connected to the first end of the primary winding of the main power transformer; A second switch tube, whose high potential end is used to be connected to the second end of the primary winding of the main power transformer, and whose low potential end is grounded; A first pulse transformer, whose primary winding is used to receive a first pulse signal; A second pulse transformer, whose primary winding is used to receive a second pulse signal; a first drive circuit, wherein a first end of the first drive circuit is connected to a like-name end of a secondary winding of the first pulse transformer, a second end of the first drive circuit is connected to an opposite-name end of a secondary winding of the first pulse transformer, a third end of the first drive circuit is connected to a control end of the first switch tube, and a fourth end of the first drive circuit is connected to a low potential end of the first switch tube, wherein the first drive circuit is used to access an induced voltage of the secondary winding of the first pulse transformer to provide the first switch tube with a positive drive voltage for turning on the first switch tube and a negative drive voltage for turning off the first switch tube; as well as a second drive circuit, wherein a first end thereof is connected to the same-name end of the secondary winding of the second pulse transformer, a second end thereof is connected to the opposite-name end of the secondary winding of the second pulse transformer, a third end thereof is connected to the control end of the second switch tube, and a fourth end thereof is connected to the low potential end of the second switch tube, and the second drive circuit is used for accessing the induced voltage of the secondary winding of the second pulse transformer to provide the second switch tube with a positive drive voltage for turning on the second switch tube and a negative drive voltage for turning off the second switch tube; The switch control circuit also includes a first signal source connected to the primary winding of the first pulse transformer and a second signal source connected to the primary winding of the second pulse transformer; When the output power of the main power transformer is zero and the first pulse signal output by the first signal source is at a high level, the second pulse signal output by the second signal source is at a low level; When the output power of the main power transformer is zero and the first pulse signal output by the first signal source is at a low level, the second pulse signal output by the second signal source is at a high level or a low level.

2. The switch control circuit according to claim 1, characterized in that: The first driving circuit includes a first resistor, a second resistor and a first voltage stabilizing module; The first end of the first resistor is connected to the same-name end of the secondary winding of the first pulse transformer as the first end of the first drive circuit, the second end of the first resistor is connected to the control end of the first switch tube as the third end of the first drive circuit, the first end of the first voltage stabilizing module is connected to the opposite-name end of the secondary winding of the first pulse transformer as the second end of the first drive circuit, the second end of the first voltage stabilizing module is connected to the low-potential end of the first switch tube as the fourth end of the first drive circuit, the first end of the second resistor is connected to the second end of the first resistor, and the second end of the second resistor is connected to the first end of the first voltage stabilizing module.

3. The switch control circuit according to claim 2, characterized in that: The first voltage stabilizing module includes a first voltage stabilizing diode and a first capacitor; The anode of the first voltage stabilizing diode is connected to the second end of the second resistor as the first end of the first voltage stabilizing module, the cathode of the first voltage stabilizing diode is connected to the low potential end of the first switching tube as the second end of the first voltage stabilizing module, and the first capacitor is connected in parallel with the first voltage stabilizing diode.

4. The switch control circuit according to claim 1, characterized in that: The second driving circuit includes a third resistor, a fourth resistor and a second voltage stabilizing module; The first end of the third resistor is connected to the same-name end of the secondary winding of the second pulse transformer as the first end of the second drive circuit, the second end of the third resistor is connected to the control end of the second switch tube as the third end of the second drive circuit, the first end of the second voltage stabilizing module is connected to the opposite-name end of the secondary winding of the second pulse transformer as the second end of the second drive circuit, the second end of the second voltage stabilizing module is connected to the low-potential end of the second switch tube as the fourth end of the second drive circuit, the first end of the fourth resistor is connected to the second end of the third resistor, and the second end of the fourth resistor is connected to the first end of the second voltage stabilizing module.

5. The switch control circuit according to claim 4, characterized in that: The second voltage stabilizing module includes a second voltage stabilizing diode and a second capacitor; The anode of the second voltage stabilizing diode is connected to the second end of the fourth resistor as the first end of the second voltage stabilizing module, the cathode of the second voltage stabilizing diode is connected to the low potential end of the second switch tube as the second end of the second voltage stabilizing module, and the second capacitor is connected in parallel with the second voltage stabilizing diode.

6. The switch control circuit according to claim 1, characterized in that: The primary winding of the first pulse transformer and the primary winding of the second pulse transformer are connected to a common ground.

7. The switch control circuit according to claim 1, characterized in that: The first switch tube and the second switch tube are MOS tubes, or the first switch tube and the second switch tube are IGBTs.

8. A power supply device, characterized in that: A switch control circuit comprising the switch control circuit according to any one of claims 1 to 7.

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