Transmission circuit

Abstract

The utility model provides a transmission circuit, which is applied to a converter and comprises switch modules, a voltage limiting module and a coupling transformer, and the third end of a first switch module and the first end of a second switch module are respectively connected with the two ends of a first coupling winding of the coupling transformer; the two ends of the first voltage limiting module are electrically connected with the first end of the second switch module and the first end of the first switch module respectively. The two ends of the second voltage limiting module are electrically connected with the third end of the second switch module and the third end of the first switch module respectively. After the transmission circuit controls the high-voltage end and the low-voltage end to be disconnected, the first voltage limiting module and the second voltage limiting module can clamp the voltage between the first end of the first switch module and the second end of the second switch module. Therefore, overhigh pressure voltage caused by the secondary side refraction voltage of the coupling module and the leakage inductance peak voltage of the transmission circuit is avoided, the voltage stress of the switch module is reduced, and the reliability and stability of the system are improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing, and in particular, to a transmission circuit. Background Art

[0002] Auxiliary power supply is an indispensable component in various power electronic converter systems. In power electronic converter systems, power control circuits, communication circuits, operational amplifier circuits, drive circuits and sampling circuits all require stable DC low-voltage power supply to provide energy source for their normal operation. Therefore, the reliable and stable operation of auxiliary switching power supply is particularly important in the entire system.

[0003] In actual photovoltaic energy storage system applications, the bus voltage that supplies power to the auxiliary switching power supply is not only high, with the maximum voltage generally reaching more than 1000V, but also has a wide bus voltage range, generally ranging from 165V to 1000V. The traditional high-voltage wide-input auxiliary switching power supply uses a single-ended flyback converter, but the voltage that the switch tube of the single-ended flyback converter withstands when it is turned off is equal to the sum of the maximum DC input bus voltage, the secondary side refracted voltage, and the leakage inductance peak voltage. At high input voltages, the voltage stress of the switch tube is very large, and MOS tubes made of SIC materials are generally used, which greatly increases the cost of the switch tube. At the same time, the current MOS tube process of SIC materials is not very mature, which also increases the risk of project development.

[0004] Therefore, how to reduce the voltage stress of the switch tube is a technical problem that technicians in this field need to solve urgently. Utility Model Content

[0005] The present application aims to solve at least one of the technical problems existing in the prior art, and proposes a transmission circuit which reduces the voltage stress of each switch module by means of at least two switch modules arranged in series.

[0006] To achieve the purpose of the present application, a transmission circuit is provided, which is applied to a converter, and includes a switch module, a voltage limiting module, and a coupling transformer, wherein the coupling transformer includes a first coupling winding located on a first side, the switch module includes a first switch module and a second switch module, and the third end of the first switch module and the first end of the second switch module are respectively connected to the two ends of the first coupling winding;

[0007] The first end of the first switch module is used to connect the high voltage end of the converter, the second end of the second switch module is used to connect the low voltage end of the converter, and the second end of the first switch module and the second end of the second switch module are both connected to the control device;

[0008] The voltage limiting module includes a first voltage limiting module and a second voltage limiting module, wherein the first end of the first voltage limiting module is electrically connected to the first end of the second switch module, the second end of the first voltage limiting module is electrically connected to the first end of the first switch module, and current can flow from the first end of the first voltage limiting module to the second end; the first end of the second voltage limiting module is electrically connected to the third end of the second switch module, the second end of the second voltage limiting module is electrically connected to the third end of the first switch module, and current can flow from the first end of the second voltage limiting module to the second end.

[0009] In some embodiments, the first switch module includes a first switch MOS tube, the second switch module includes a second switch MOS tube, the first end of the first switch MOS tube is electrically connected to the high voltage end, the third end of the first switch MOS tube is electrically connected to the first end of the second switch MOS tube, the third end of the second switch MOS tube is electrically connected to the low voltage end, and the second end of the first switch MOS tube and the second end of the second switch MOS tube are both used to be electrically connected to a control device to control the switching of the first switch MOS tube and the second switch MOS tube.

[0010] In some embodiments, a driving module is further included. The driving module is arranged between the control device and the first switch module and between the control device and the second switch module, and is used to enhance the control signal of the control device to drive the first switch module and the second switch module.

[0011] In some embodiments, the driving module includes a first transistor and a second transistor, which are electrically connected to form a totem pole circuit, and the totem pole circuit is used to enhance the control signal.

[0012] In some embodiments, an isolation module is further included, for isolating the control device from the first switch module and the second switch module.

[0013] In some embodiments, a filtering module is further included. The filtering module is located between the isolation module and the driving module and is used for filtering.

[0014] In some embodiments, the isolation module includes an isolation transformer, which includes a first isolation winding, a second isolation winding and a third isolation winding, the first isolation winding is located on a first side of the isolation transformer, the second isolation winding and the third isolation winding are located on a second side of the isolation transformer, the first isolation winding is electrically connected to the totem pole circuit, and the second isolation winding and the third isolation winding are electrically connected to the second end of the first switch module and the second end of the second switch module, respectively.

[0015] In some embodiments, an absorption module is further included, wherein the absorption module is used to absorb the peak voltage of the first side of the coupling transformer.

[0016] In some embodiments, the absorption module includes a first absorption module and a second absorption module.

[0017] The first absorption module includes a first absorption capacitor, a first absorption diode and a first absorption resistor, wherein the first end of the first absorption capacitor is electrically connected to the first end of the first switch module, the first end of the first absorption diode and the first end of the first absorption resistor are both electrically connected to the second end of the first absorption capacitor, the second end of the first absorption diode and the second end of the first absorption resistor are both electrically connected to the third end of the first switch module, and the current can flow from the first end of the first absorption diode to the second end;

[0018] The second absorption module includes a second absorption capacitor, a second absorption diode and a second absorption resistor. The first end of the second absorption capacitor is electrically connected to the first end of the second switch module, the first end of the second absorption diode and the first end of the second absorption resistor are both electrically connected to the second end of the second absorption capacitor, the second end of the second absorption diode and the second end of the second absorption resistor are both electrically connected to the third end of the second switch module, and current can flow from the first end of the second absorption diode to the second end.

[0019] In some embodiments, a reset module is further included, for resetting the inductance of the first side of the coupling transformer.

[0020] In some embodiments, a rectification and filtering module is also included, the coupling transformer includes a second coupling winding located on the second side, and the rectification and filtering module is connected to both ends of the second coupling winding and is used for rectifying and filtering the second side of the coupling transformer.

[0021] In some embodiments, the rectification and filtering module includes a rectifier diode and a second filter capacitor, the first end of the rectifier diode is connected to the first end of the second coupling winding, the second end of the rectifier diode is connected to the first end of the second filter capacitor, the second end of the second filter capacitor is connected to the second end of the second coupling winding, and the current can flow from the first end of the diode to the second end.

[0022] This application has the following beneficial effects:

[0023] The transmission circuit provided in the present application is applied to a converter, and includes a switch module, a voltage limiting module and a coupling transformer. The coupling transformer includes a first coupling winding located on a first side. The number of switch modules is two, namely, a first switch module and a second switch module. The third end of the first switch module and the first end of the second switch module are respectively connected to the two ends of the first coupling winding; the first end of the first switch module is used to connect the high-voltage end of the converter, the second end of the second switch module is used to connect the low-voltage end of the converter, and the second end of the first switch module and the second end of the second switch module are both connected to a control device; the number of voltage limiting modules is two, namely, a first voltage limiting module and a second voltage limiting module. The first end of the first voltage limiting module is electrically connected to the first end of the second switch module, and the second end of the first voltage limiting module is electrically connected to the first end of the first switch module, and the current can flow from the first end of the first voltage limiting module to the second end; the first end of the second voltage limiting module is electrically connected to the third end of the second switch module, and the second end of the second voltage limiting module is electrically connected to the third end of the first switch module, and the current can flow from the first end of the second voltage limiting module to the second end.

[0024] After the transmission circuit controls the high voltage end and the low voltage end to be disconnected through the first switch module and the second switch module, the first voltage limiting module and the second voltage limiting module can clamp the voltage between the first end of the first switch module and the second end of the second switch module, thereby avoiding the pressure voltage caused by the secondary side refraction voltage of the coupling module and the leakage inductance spike voltage of the transmission circuit to be too high, thereby reducing the voltage stress of the switch module and increasing the reliability and stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a circuit diagram of a conveying circuit of the present invention;

[0026] Figure 2 is the circuit block diagram of the converter;

[0027] Figure 3 It is a simulation output waveform diagram of the transmission circuit of the present invention.

[0028] in, Figure 1 and Figure 2 The reference numerals in the drawings are:

[0029] The first triode 1, the second triode 2, the first filter capacitor 3, the filter resistor 4, the isolation transformer 5, the first switch resistor 6, the first switch MOS tube 7, the second switch resistor 8, the third switch resistor 9, the second switch MOS tube 10, the fourth switch resistor 11, the first absorption capacitor 12, the first absorption diode 13, the first absorption resistor 14, the second absorption capacitor 15, the second absorption diode 16, the second absorption resistor 17, the first voltage limiting diode 18, the second voltage limiting diode 19, the coupling transformer 20, the rectifier diode 21, the second filter capacitor 22, the anti-interference circuit 100 on the battery side, the anti-interference circuit 200 on the power generation side, the bidirectional BUCK / BOOST circuit 300 on the battery side, the BOOST circuit 400 on the power generation side, and the bus side circuit 500. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solution of the present application, the transmission circuit provided by the present application is described in detail below with reference to the accompanying drawings.

[0031] The transmission circuit provided in the present application is applied to a converter. The converter includes a high-voltage end and a low-voltage end, and the transmission circuit is used to transmit current between the high-voltage end and the low-voltage end. The switch module includes a first switch module and a second switch module, and the third end of the first switch module and the first end of the second switch module are respectively connected to the two ends of the first coupling winding; the first end of the first switch module is used to connect the high-voltage end of the converter, and the second end of the second switch module is used to connect the low-voltage end of the converter. The second ends of the two switch modules are both connected to a control device, and the control device is used to send a control signal, and the control signal can control the switching of the two switch modules. The two switch modules are turned on at the same time to turn on the high-voltage end and the low-voltage end, and the switch module can be a transistor switch circuit, etc. The coupling transformer includes a first coupling winding located on the first side, and the second end of the first switch module and the second end of the second switch module are both connected to the control device; the voltage limiting module includes a first voltage limiting module and a second voltage limiting module, the first end of the first voltage limiting module is electrically connected to the first end of the second switch module, the second end of the first voltage limiting module is electrically connected to the first end of the first switch module, and the current can flow from the first end of the first voltage limiting module to the second end; the first end of the second voltage limiting module is electrically connected to the third end of the second switch module, the second end of the second voltage limiting module is electrically connected to the third end of the first switch module, and the current can flow from the first end of the second voltage limiting module to the second end.

[0032] In this embodiment, the first voltage limiting module and the second voltage limiting module can clamp the voltage between the first end of the first switch module and the second end of the second switch module, thereby avoiding excessive pressure voltage caused by the secondary side refraction voltage of the coupling module and the leakage inductance spike voltage of the transmission circuit, thereby reducing the voltage stress of the switch module, thereby reducing the risk of damage to the switch module and improving the reliability and stability of the system.

[0033] In some embodiments, Figure 1 As shown, the first switch module includes a first switch MOS transistor 7, and the second switch module includes a second switch MOS transistor 10. The first end of the first switch MOS transistor 7 is electrically connected to the high voltage end, the third end of the first switch MOS transistor 7 is electrically connected to the first end of the second switch MOS transistor 10, the third end of the second switch MOS transistor 10 is electrically connected to the low voltage end, and the second end of the first switch MOS transistor 7 and the second end of the second switch MOS transistor 10 are both used to be electrically connected to the control device to control the switching of the first switch MOS transistor 7 and the second switch MOS transistor 10. Figure 1 In the specific implementation manner shown, the first switch MOS transistor 7 and the second switch MOS transistor 10 are both NMOS transistors, the first end of the first switch MOS transistor 7 and the second switch MOS transistor 10 is a drain, the second end is a gate, and the third end is a source. Of course, the first switch MOS transistor 7 and the second switch MOS transistor 10 can also be PMOS transistors, which is not limited here.

[0034] Optionally, the first switch module further includes a first switch resistor 6 and a second switch resistor 8, the first switch resistor 6 is connected in series between the control device and the second end of the first switch MOS tube 7, and the two ends of the second switch resistor 8 are respectively connected to the second end and the third end of the first switch MOS tube 7. The second switch module further includes a third switch resistor 9 and a fourth switch resistor 11, the first switch resistor 6 is connected in series between the control device and the second end of the second switch MOS tube 10, and the two ends of the second switch resistor 8 are respectively connected to the second end and the third end of the second switch MOS tube 10.

[0035] In some embodiments, the transmission circuit further includes a driving module, which is arranged between the control device and the first switch module and between the control device and the second switch module. The control device can send a PWM (Pulse Width Modulation) signal as a control signal, and the control signal may not be sufficient to drive the first switch MOS tube 7 and the second switch MOS tube 10 due to reasons such as low current. The driving module can amplify the current of the control signal so that it meets the conditions for driving the first switch module and the second switch module, thereby ensuring the stability and reliability of the system.

[0036] In some embodiments, the driving module may adopt a totem pole circuit. Specifically, the driving module may include a first transistor and a second transistor 2. Among them, the first transistor is an NPN transistor, the second transistor 2 is a PNP transistor, and the first and second transistors are electrically connected to form a totem pole circuit, the collector of the first transistor is connected to the power supply, the emitter of the first transistor is connected to the emitter of the second transistor 2, the collector of the second transistor 2 is grounded, and the bases of the first transistor and the second transistor 2 are both connected to the control device, thereby forming a totem pole circuit for enhancing the control signal. Of course, users can also use other circuit structures to enhance the control signal as needed, which is not limited here.

[0037] In some embodiments, the transmission circuit further includes an isolation module for isolating the control signal of the previous stage from the MOS switch circuit of the subsequent stage.

[0038] In some embodiments, the isolation module includes an isolation transformer 5, and the isolation transformer 5 includes a first isolation winding, a second isolation winding, and a third isolation winding. The first isolation winding is located on a first side of the isolation transformer 5, and the second isolation winding and the third isolation winding are located on a second side of the isolation transformer 5. The first side of the isolation transformer 5 is the primary side, and the second side is the secondary side. One end of the first isolation winding is electrically connected to the totem pole circuit, such as Figure 1 As shown, one end of the first isolation winding is electrically connected to the emitter of the first triode and the emitter of the second triode 2, and the other end is grounded. One end of the second isolation winding is electrically connected to the gate of the first switch MOS tube 7 through the first switch resistor 6, and the other end of the second isolation winding is electrically connected to the source of the second switch MOS tube 10. One end of the third isolation winding is electrically connected to the gate of the second switch MOS tube 10 through the second switch resistor 8, and the other end of the second isolation winding is electrically connected to the source of the second switch MOS tube 10.

[0039] In some embodiments, the transmission circuit further includes a filtering module for performing DC isolation and current limiting filtering on the control signal to avoid interference caused by DC current and clutter in the control signal. The filtering module can be located in the isolation module and the driving module.

[0040] Optionally, the filter module includes a first filter capacitor 3 and a filter resistor 4. The first end of the first filter capacitor 3 is connected to the emitter of the first transistor and the emitter of the second transistor 2, and the second end of the first filter capacitor 3 is connected to the first end of the first winding of the isolation transformer 5 through the filter resistor 4. The first filter capacitor 3 and the filter resistor 4 form an RC circuit, which can effectively filter out the DC current and clutter in the control signal. Of course, the structure of the filter module is not limited to this.

[0041] In some embodiments, the transmission circuit further includes a coupling module for connecting the first switch module and the second switch module.

[0042] In some embodiments, the coupling module includes a coupling transformer 20, the coupling transformer 20 includes a first coupling winding located at a first side, and the first side of the coupling transformer 20 is a primary side of the coupling transformer 20. The source of the first switch module and the drain of the second switch module are respectively connected to two ends of the first coupling winding.

[0043] In some embodiments, the transmission circuit further includes an absorption module, and the absorption module is used to absorb the peak voltage of the first side of the coupling transformer 20 .

[0044] In some embodiments, the absorption module includes a first absorption module and a second absorption module. The first absorption module includes a first absorption capacitor 12, a first absorption diode 13, and a first absorption resistor 14, wherein the first end of the first absorption capacitor 12 is connected to the drain of the first switch MOS tube 7, the first end of the first absorption diode 13 and the first end of the first absorption resistor 14 are both connected to the second end of the first absorption capacitor 12, the second end of the first absorption diode 13 and the second end of the first absorption resistor 14 are both connected to the source of the first switch MOS tube 7, and the current can flow from the first end of the first absorption diode 13 to the second end;

[0045] The second absorption module includes a second absorption capacitor 15, a second absorption diode 16, and a second absorption resistor 17. The first end of the second absorption capacitor 15 is connected to the drain of the second switch MOS tube 10. The first end of the second absorption diode 16 and the first end of the second absorption resistor 17 are both electrically connected to the second end of the second absorption capacitor 15. The second end of the second absorption diode 16 and the second end of the second absorption resistor 17 are both connected to the source of the second switch MOS tube 10. The current can flow from the first end of the second absorption diode 16 to the second end. Of course, the structure of the absorption module is not limited to this.

[0046] In some embodiments, the voltage limiting module may also be used for inductive voltage limiting of the first side of the coupling transformer 20 .

[0047] In some embodiments, the first voltage limiting module includes a first voltage limiting diode 18, and the second voltage limiting module includes a second voltage limiting diode 19. The first end of the first voltage limiting diode 18 is electrically connected to the first end of the second switch module, and the second end of the first voltage limiting diode 18 is electrically connected to the first end of the first switch module, and the current can flow from the first end of the first voltage limiting diode 18 to the second end; the first end of the second voltage limiting diode 19 is electrically connected to the third end of the second switch module, and the second end of the second voltage limiting diode 19 is electrically connected to the third end of the first switch module, and the current can flow from the first end of the second voltage limiting diode 19 to the second end.

[0048] In some embodiments, the transmission circuit further includes a rectifying and filtering module, and the coupling transformer 20 includes a second coupling winding located at the second side. The second side of the coupling transformer 20 is the secondary side of the coupling transformer 20. The rectifying and filtering module is connected to both ends of the second coupling winding, and is used for rectifying and filtering the second side of the coupling transformer 20.

[0049] In some embodiments, the rectifying and filtering module includes a rectifying diode 21 and a second filtering capacitor 22, wherein the first end of the rectifying diode 21 is connected to the first end of the second coupling winding, the second end of the rectifying diode 21 is connected to the first end of the second filtering capacitor 22, and the second end of the second filtering capacitor 22 is connected to the second end of the second coupling winding, and the current can flow from the first end of the diode to the second end. Of course, the structure of the rectifying and filtering module is not limited thereto.

[0050] The present application also provides a converter, including a high voltage end, a low voltage end, and a transmission circuit in any one of the above embodiments. Figure 2 As shown, the converter also includes an anti-interference circuit on the battery side, an anti-interference circuit on the generator side, a bidirectional BUCK / BOOST circuit on the battery side, a BOOST circuit on the generator side, and a bus side circuit. The structure of other parts of the converter can refer to the prior art and will not be described here.

[0051] Figure 3 The operating waveform of the converter provided in the present application, in which channel 1 is the base and collector driving voltage waveform of the first triode 1 and the second first triode 1, and channel 2 is the drain and source voltage waveform of the first triode 1 and the second first triode 1. The converter works in the inductor current discontinuous working mode and has the following four working states:

[0052] State 1 (t0-t1): At t0, the first switch MOS tube 7 and the second switch MOS tube 10 are turned on at the same time, and the high-voltage end of the converter provides energy for the first winding and leakage inductance of the coupling transformer 20, and the primary inductor current rises linearly with a slope of diLl / dt=HV / (Lm+Ll), where Lm is the inductance of the first winding, L1 is the inductance of the leakage inductance, and HV is the voltage at the high-voltage end. The first voltage-limiting diode 18 and the second voltage-limiting diode 19 are in the cut-off state, the inductance voltage of the second winding is positive at the bottom and negative at the top, the rectifier diode 21 is reversely cut off, no current flows on the secondary side, and the load current is provided by the second filter capacitor 22.

[0053] State 2 (t1-t2): At time t1, the first switch MOS tube 7 and the second switch MOS tube 10 are turned off at the same time, the current of the primary winding leakage inductance L1 begins to decrease, and the voltage across the primary inductance is reversed, so that the first voltage limiting diode 18 and the second voltage limiting diode 19 are immediately turned on, clamping the primary winding induced electromotive force caused by the leakage inductance, so that it is clamped at the input voltage HV, and the excess energy is fed back to the input power supply. The reverse voltage borne by the first triode 1 and the second first triode 1 is HV. At this time, the second filter capacitor 22 is charged and also provides energy to the load.

[0054] State 3 (t2-t3): At t2, the primary inductor current value iL1 drops to zero, the excitation inductor completes the energy transfer to the secondary inductor, the clamped first voltage limiting diode 18 and the second voltage limiting diode 19 are closed, iD drops to zero, iL2 reaches the maximum value, and the voltage across the first switch MOS tube 7 and the second switch MOS tube 10 drops to [HV+(N1 / N2)×Uo]. At this time, the second winding inductor of the coupling transformer 20 provides energy to the capacitor and the load.

[0055] State 4 (t3-t4): At t3, the discharge is completed, the inductance current of the second winding of the coupling transformer 20 is zero, and the refracted voltage generated by the inductance of the second winding of the coupling transformer 20 becomes 0V. At this time, the voltage borne by the second winding of the coupling transformer 20 is HV / 2. When reaching t4, a new working cycle begins.

[0056] From the above working state analysis, it can be seen that the highest voltage stress of the two switch modules of the converter is only the voltage at the high-voltage end, which is smaller than the voltage stress of the switch tube of the single-tube flyback converter, so the voltage stress of a single switch module can be reduced.

[0057] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present application, but the present application is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of the present application, and these modifications and improvements are also considered to be within the scope of protection of the present application.

Claims

1. A transmission circuit, applied to a converter, characterized in that: It includes a switch module, a voltage limiting module and a coupling transformer, wherein the coupling transformer includes a first coupling winding located at a first side, the switch module includes a first switch module and a second switch module, and the third end of the first switch module and the first end of the second switch module are respectively connected to the two ends of the first coupling winding; The first end of the first switch module is used to connect the high voltage end of the converter, the second end of the second switch module is used to connect the low voltage end of the converter, and the second end of the first switch module and the second end of the second switch module are both connected to the control device; The voltage limiting module includes a first voltage limiting module and a second voltage limiting module, wherein the first end of the first voltage limiting module is electrically connected to the first end of the second switch module, the second end of the first voltage limiting module is electrically connected to the first end of the first switch module, and current can flow from the first end of the first voltage limiting module to the second end; the first end of the second voltage limiting module is electrically connected to the third end of the second switch module, the second end of the second voltage limiting module is electrically connected to the third end of the first switch module, and current can flow from the first end of the second voltage limiting module to the second end.

2. The transmission circuit according to claim 1, characterized in that The first switch module includes a first switch MOS tube, and the second switch module includes a second switch MOS tube. The first end of the first switch MOS tube is electrically connected to the high voltage end, the third end of the first switch MOS tube is electrically connected to the first end of the second switch MOS tube, and the third end of the second switch MOS tube is electrically connected to the low voltage end. The second end of the first switch MOS tube and the second end of the second switch MOS tube are both used to be electrically connected to the control device to control the switching of the first switch MOS tube and the second switch MOS tube.

3. The transmission circuit according to claim 2, characterized in that It also includes a driving module, which is arranged between the control device and the first switch module and between the control device and the second switch module, and is used to enhance the control signal of the control device to drive the first switch module and the second switch module.

4. The transmission circuit according to claim 3, characterized in that The driving module includes a first transistor and a second transistor, which are electrically connected to form a totem pole circuit, and the totem pole circuit is used to enhance the control signal.

5. The transmission circuit according to claim 4, characterized in that It also includes an isolation module for isolating the control device from the first switch module and the second switch module.

6. The transmission circuit according to claim 5, characterized in that It also includes a filtering module, which is located between the isolation module and the driving module and is used to filter out the direct current of the control signal.

7. The transmission circuit according to claim 6, characterized in that The isolation module includes an isolation transformer, which includes a first isolation winding, a second isolation winding and a third isolation winding. The first isolation winding is located on a first side of the isolation transformer, the second isolation winding and the third isolation winding are located on a second side of the isolation transformer, the first isolation winding is electrically connected to the totem pole circuit, and the second isolation winding and the third isolation winding are electrically connected to the second end of the first switch module and the second end of the second switch module, respectively.

8. The transmission circuit according to claim 2, characterized in that The device also includes an absorption module, which is used to absorb the peak voltage of the first side of the coupling transformer.

9. The transmission circuit according to claim 8, characterized in that The absorption module comprises a first absorption module and a second absorption module, The first absorption module includes a first absorption capacitor, a first absorption diode and a first absorption resistor, wherein the first end of the first absorption capacitor is electrically connected to the first end of the first switch module, the first end of the first absorption diode and the first end of the first absorption resistor are both electrically connected to the second end of the first absorption capacitor, the second end of the first absorption diode and the second end of the first absorption resistor are both electrically connected to the third end of the first switch module, and the current can flow from the first end of the first absorption diode to the second end; The second absorption module includes a second absorption capacitor, a second absorption diode and a second absorption resistor. The first end of the second absorption capacitor is electrically connected to the first end of the second switch module, the first end of the second absorption diode and the first end of the second absorption resistor are both electrically connected to the second end of the second absorption capacitor, the second end of the second absorption diode and the second end of the second absorption resistor are both electrically connected to the third end of the second switch module, and current can flow from the first end of the second absorption diode to the second end.

10. The transmission circuit according to claim 2, characterized in that A reset module is also included, which is used to reset the inductance of the first side of the coupling transformer.

11. The transmission circuit according to claim 2, characterized in that It also includes a rectifying and filtering module. The coupling transformer includes a second coupling winding located on the second side. The rectifying and filtering module is connected to both ends of the second coupling winding and is used for rectifying and filtering the second side of the coupling transformer.

12. The transmission circuit according to claim 11, characterized in that: The rectification and filtering module includes a rectifier diode and a second filtering capacitor, wherein the first end of the rectifier diode is connected to the first end of the second coupling winding, the second end of the rectifier diode is connected to the first end of the second filtering capacitor, and the second end of the second filtering capacitor is connected to the second end of the second coupling winding, and the current can flow from the first end of the diode to the second end.

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