Asymmetric half-bridge circuit with output rectifier tube voltage stress control

Abstract

The invention relates to an asymmetric half-bridge circuit with an output rectifier tube voltage stress control function. The asymmetric half-bridge circuit comprises an asymmetric half-bridge main power conversion circuit, an output rectifier circuit and an output rectifier tube voltage stress control circuit, the output rectifying circuit comprises an output rectifying tube and an output capacitor; the output rectifier tube voltage stress control circuit is connected with the output end of the output rectifier circuit; the output rectifier tube voltage stress control circuit comprises a drive control circuit and a voltage discharge circuit. In the steady-state working process, the driving control circuit outputs a first control signal to control the voltage leakage circuit to be kept in the turn-off state, and therefore extra energy is not consumed; after the input voltage is closed, the voltage at the two ends of the output capacitor is reduced, the driving control circuit outputs a second control signal to control the voltage discharge circuit to be switched on, and the discharge of the residual voltage on the output capacitor is accelerated through the voltage discharge circuit; and when the input power supply is connected again, the voltage stress on the output rectifier tube can be reduced, so that the reliability of the power supply system is improved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic circuits, and in particular to an asymmetric half-bridge circuit with output rectifier tube voltage stress control. Background Art

[0002] Asymmetric resonant half-bridge (AHB) circuit is widely used in power electronic conversion applications due to its topological structure characteristics. The primary power tube of this circuit can achieve zero voltage switch-on (ZVS), and the secondary power tube can achieve zero current switch-off (ZCS), thereby improving the power conversion efficiency and achieving efficient power conversion. Due to the use of soft switching technology, the AHB circuit can operate at a higher switching frequency, so the power density is also greatly improved.

[0003] The synchronous rectifier of the AHB circuit is subjected to lower voltage stress. In steady-state operation, the voltage stress of the rectifier is Vin / n (input voltage Vin divided by the primary-to-secondary turns ratio n of the transformer). Compared with the traditional flyback circuit or active clamp flyback circuit, the voltage stress of the rectifier of the AHB circuit is smaller, so a MOS tube with lower withstand voltage can be used as the rectifier, which greatly reduces the system cost and debugging difficulty.

[0004] In light-emitting diode (LED) driving applications, the AHB topology is favored for its high efficiency and high power density. However, due to the particularity of LED loads, when the power supply is continuously turned on and off, the voltage stress of the output rectifier is higher than that of traditional resistive loads. Specifically, when the input voltage is turned off, at first, the voltage on the output capacitor will gradually decrease as the LED is turned off, and when the output voltage drops to a level lower than the LED's conduction voltage, the LED is turned off, and the rate of decrease of the voltage on the output capacitor becomes slower. When the power supply is restarted, the voltage stress across the output rectifier will be superimposed on the residual voltage of the output capacitor, resulting in an increase in the voltage stress of the rectifier. This phenomenon is particularly obvious during continuous switching, which may affect the reliability of the circuit. Summary of the invention

[0005] The purpose of the present invention is to provide an asymmetric half-bridge circuit with output rectifier tube voltage stress control to reduce the voltage stress of the output rectifier tube, thereby improving the reliability of the power supply system.

[0006] To achieve the above object, the present invention provides an asymmetric half-bridge circuit with output rectifier tube voltage stress control, comprising: an asymmetric half-bridge main power conversion circuit, an output rectifier circuit and an output rectifier tube voltage stress control circuit;

[0007] The asymmetric half-bridge main power conversion circuit includes: a high-side switch tube Q3 and a low-side switch tube Q4, a resonant capacitor Cr and a transformer T1; wherein the high-side switch tube Q3 and the low-side switch tube Q4 form an asymmetric half-bridge structure for driving the primary winding Np of the transformer T1; the secondary winding Ns of the driving transformer T1 is connected to the output rectifier circuit;

[0008] The output rectifier circuit includes an output rectifier tube D1 and an output capacitor EC2, which are used to convert the voltage of the secondary winding Ns of the transformer into an output voltage Vo; the output capacitor EC2 is connected between the output end of the output rectifier tube D1 and the ground;

[0009] The output rectifier tube voltage stress control circuit is connected to the output end of the output rectifier circuit; the output rectifier tube voltage stress control circuit includes: a drive control circuit and a voltage discharge circuit; when the asymmetric half-bridge circuit is in steady-state operation, the drive control circuit outputs a first control signal to control the voltage discharge circuit to remain in an off state; after the input voltage of the asymmetric half-bridge circuit is turned off, the voltage across the output capacitor EC2 drops, and the drive control circuit outputs a second control signal to control the voltage discharge circuit to turn on, thereby accelerating the discharge of the residual voltage on the output capacitor EC2 through the voltage discharge circuit.

[0010] Preferably, the driving control circuit specifically includes: a first voltage divider circuit and a MOS tube Q1;

[0011] The first voltage divider circuit is connected in parallel across the output capacitor EC2;

[0012] The gate of the MOS transistor Q1 is connected to the first voltage-dividing node of the first voltage-dividing circuit; the drain of the MOS transistor Q1 is the control signal output terminal of the driving control circuit;

[0013] When the asymmetric half-bridge circuit is in steady-state operation, the MOS transistor Q1 is turned on through the first voltage divider circuit, and the control signal output terminal outputs a first control signal that keeps the voltage discharge circuit turned off;

[0014] After the input voltage of the asymmetric half-bridge circuit is turned off, the voltage across the output capacitor EC2 drops, the MOS tube Q1 is turned off through the first voltage divider circuit, and the control signal output terminal outputs a second control signal to turn on the voltage discharge circuit.

[0015] Further preferably, the first voltage divider circuit is a first series resistor voltage divider circuit.

[0016] Preferably, the voltage discharge circuit specifically includes: a second voltage divider circuit, a MOS tube Q2 and a voltage divider network;

[0017] The second voltage divider circuit is connected in parallel across the output capacitor EC2;

[0018] The output terminal of the driving control circuit is connected to the gate of the MOS tube Q2, and is also connected to the second voltage dividing node of the second voltage dividing circuit;

[0019] The voltage divider network is connected to the output end of the output rectifier tube D1 and is connected to the voltage discharge circuit through the MOS tube Q2;

[0020] When the asymmetric half-bridge circuit is in steady-state operation, the gate of the MOS transistor Q2 receives the first control signal, and the MOS transistor Q2 remains turned off;

[0021] After the input voltage of the asymmetric half-bridge circuit is turned off, the voltage across the output capacitor EC2 drops, the gate of the MOS tube Q2 receives the second control signal, the MOS tube Q2 is turned on, and the voltage divider network is connected to the voltage discharge circuit, so that the residual voltage on the output capacitor EC2 is accelerated to be discharged through the voltage divider network.

[0022] Further preferably, the second voltage divider circuit is a second series resistor voltage divider circuit.

[0023] Further preferably, the voltage divider network specifically includes a plurality of load resistors connected in parallel.

[0024] Preferably, the upper end of the high-side switch tube Q3 is connected to the input voltage, the lower end is connected to the low-side switch tube Q4, and the lower end of the low-side switch tube Q4 is grounded;

[0025] One end of the primary winding Np is connected to the input voltage, and the resonant capacitor Cr is connected in series between a common point between the high-side switch tube Q3 and the low-side switch tube Q4 and the other end of the primary winding Np.

[0026] Preferably, the asymmetric half-bridge main power conversion circuit further includes an input filter capacitor EC1.

[0027] Preferably, the asymmetric half-bridge circuit with output rectifier tube voltage stress control is used in a driving circuit of an LED load.

[0028] Further preferably, after the input voltage of the asymmetric half-bridge circuit is turned off, the voltage across the output capacitor EC2 drops, and the drive control circuit outputs the second control signal to control the voltage discharge circuit to be turned on, specifically:

[0029] After the input voltage of the asymmetric half-bridge circuit is turned off, when the voltage across the output capacitor EC2 drops to the turn-on voltage threshold of the LED load, the drive control circuit outputs a second control signal to control the voltage discharge circuit to turn on.

[0030] The asymmetric half-bridge circuit with output rectifier voltage stress control provided by the embodiment of the present invention realizes the voltage stress control of the output rectifier through the output rectifier voltage stress control circuit. The output rectifier voltage stress control circuit includes: a drive control circuit and a voltage discharge circuit; when the circuit is in steady-state operation, the drive control circuit outputs a first control signal to control the voltage discharge circuit to remain in an off state, so as not to consume additional energy; after the input voltage is turned off, the voltage across the output capacitor drops, and the drive control circuit outputs a second control signal to control the voltage discharge circuit to turn on, and the voltage discharge circuit accelerates the discharge of the residual voltage on the output capacitor; so that when the asymmetric half-bridge circuit is connected to the input power supply again, the voltage stress on the output rectifier can be effectively reduced, especially in the scenario of continuous switching, the voltage stress of the output rectifier can be effectively and quickly reduced, thereby improving the reliability of the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A structural block diagram of an asymmetric half-bridge circuit with output rectifier tube voltage stress control provided by an embodiment of the present invention;

[0032] Figure 2 A specific implementation circuit of an asymmetric half-bridge circuit with output rectifier tube voltage stress control provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0034] An embodiment of the present invention provides an asymmetric half-bridge circuit with output rectifier tube voltage stress control. Figure 1 The structure block diagram of the asymmetric half-bridge circuit with output rectifier voltage stress control provided by the embodiment of the present invention is first combined with Figure 1 , the technical solution of the present invention is described.

[0035] like Figure 1 As shown, the asymmetric half-bridge circuit with output rectifier tube voltage stress control of the present invention includes: an asymmetric half-bridge main power conversion circuit 10, an output rectifier circuit 20 and an output rectifier tube voltage stress control circuit 30.

[0036] The asymmetric half-bridge main power conversion circuit 10 is used to achieve efficient conversion of input electric energy, convert the DC input voltage Vin into a high-frequency AC signal, and provide a stable voltage for subsequent circuits through voltage conversion. At the same time, the input circuit is isolated from the output circuit to improve the safety and anti-interference ability of the circuit.

[0037] The output rectifier circuit 20 converts the high-frequency AC signal from the asymmetric half-bridge main power conversion circuit 10 into a stable DC voltage, adapts to the load requirements of the DC power supply, and outputs a stable DC voltage Vo.

[0038] The output rectifier tube voltage stress control circuit 30 is connected to the output end of the output rectifier circuit 20; the output rectifier tube voltage stress control circuit 30 includes: a drive control circuit 31 and a voltage discharge circuit 32. The drive control circuit 31 is used to control the opening or closing of the voltage discharge circuit 32. When the asymmetric half-bridge circuit is in steady-state operation, the drive control circuit 31 controls the voltage discharge circuit 32 to remain in an off state, so as not to consume additional energy; after the input voltage Vin of the asymmetric half-bridge circuit is turned off, the drive control circuit 31 controls the voltage discharge circuit 32 to turn on, and accelerates the residual voltage discharge on the output capacitor in the output rectifier circuit through the voltage discharge circuit 32. When the asymmetric half-bridge circuit is connected to the input power supply Vin again, the voltage stress on the output rectifier tube in the output rectifier circuit is reduced, thereby improving the reliability of the power supply system.

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following will be combined with the attached Figure 2 The present invention is further described in detail. It can be understood that the attached Figure 2 The described embodiment is only a specific circuit that can realize the technical solution of the present invention, rather than the only circuit form. Based on the embodiment 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.

[0040] like Figure 2 As shown, the asymmetric half-bridge main power conversion circuit includes: a high-side switch tube Q3 and a low-side switch tube Q4, a resonant capacitor Cr and a transformer T1; wherein the high-side switch tube Q3 and the low-side switch tube Q4 are connected in series between the input voltage Vin and the ground to form an asymmetric half-bridge structure for driving the primary winding Np of the transformer T1; one end of the primary winding Np is connected to the input voltage Vin, and the resonant capacitor Cr is connected in series between the common point HB between the high-side switch tube Q3 and the low-side switch tube Q4 and the other end of the primary winding Np. The secondary winding Ns of the driving transformer T1 is connected to the output rectifier circuit. In addition, the asymmetric half-bridge main power conversion circuit also includes an input filter capacitor EC1, which is connected in series between the input voltage Vin and the ground.

[0041] The output rectifier circuit includes an output rectifier tube D1 and an output capacitor EC2. The input end of the output rectifier tube D1 is connected to the secondary winding Ns, and is used to convert the voltage of the secondary winding Ns of the transformer T1 into an output voltage Vo; the output capacitor EC2 is connected between the output end of the output rectifier tube D1 and the ground.

[0042] In this circuit, the AHB transfer function in steady-state operation is: (Vi n-Vcr)·D·T=n·Vo·(1-D)·T; where Vin is the input voltage, Vcr is the voltage across the resonant capacitor Cr, D is the duty cycle, T is the switching period, and n is the primary-to-secondary turns ratio of the transformer T1.

[0043] The duty cycle D here refers to the ratio of the on-time of the main switch tube (in this case, the high-side switch tube Q3) to a switching period T: D = t on / T; where t on The switching cycle T is the time when the main switch tube is turned on. The switching cycle T refers to the complete cycle formed by the alternating conduction of the two switch tubes Q3 and Q4.

[0044] In the steady state, the voltage Vcr of the resonant capacitor Cr is approximately nVo, so the steady-state transfer function can be simplified to: Vo≈Vi n·D.

[0045] When the power is turned on and off continuously:

[0046] The voltage Vcr of the resonant capacitor Cr will be released quickly after the power is turned off. At the subsequent startup moment, since the resonant capacitor voltage Vcr cannot change suddenly (limited by the capacitor characteristics), it can be considered that Vcr≈0 when the power is just turned on.

[0047] Combined transfer function: (Vi n-Vcr)·D·T=n·Vo·(1-D)·T;

[0048] When Vcr≈0, it is simplified to: Vin·D·T=n·Vo·(1-D)·T;

[0049] Therefore, the transfer function of the AHB transient is Vo=[Vi n / n]·D / (1-D).

[0050] This shows that at the moment of power-on, the characteristics of the output voltage Vo and the duty cycle D show a relationship similar to that of the flyback topology. At the moment of power-on, because Vcr≈0, the resonant capacitor temporarily does not play a major role, and the voltage on the primary side of the transformer is approximately equal to Vin, which is similar to the primary side working mode in the flyback topology, and the input voltage directly drives the primary winding of the transformer. In continuous operation, the voltage of the resonant capacitor Vcr gradually builds up, and after entering the steady state, Vcr begins to divide the primary voltage of the transformer, reflecting the characteristics of the AHB topology. Therefore, the asymmetric half-bridge can be considered to be a gradual transition from the flyback topology to the AHB topology at the moment of power-on.

[0051] The voltage stress of the output rectifier tube D1 refers to the maximum reverse voltage it withstands during operation, which is related to the following factors: 1. The voltage of the secondary winding Ns of the transformer; 2. The residual voltage Vres of the output capacitor EC2.

[0052] In the continuous switching, if there is a residual voltage Vres on the output capacitor EC2 when the power is turned off, the voltage stress of the output rectifier tube D1 will increase when the power is turned on again.

[0053] At the moment of power on, due to the superposition of the output voltage of the transformer secondary winding Ns and the residual voltage Vres of the output capacitor EC2, the maximum reverse voltage that the output rectifier D1 bears is: V D1,max =1 / n·(Vi n-Vcr)+Vres.

[0054] When Vcr≈0V, the secondary winding voltage reaches its maximum value, and the voltage stress of the output rectifier is mainly determined by the input voltage Vin and the output capacitor residual voltage Vres. If Vres is high, this superposition effect will significantly increase the voltage stress of the output rectifier D1, which may exceed its withstand voltage design range and cause device damage.

[0055] Therefore, it can be understood that when the machine is turned on and off continuously, the voltage stress of the output rectifier tube is related to the residual voltage of the output capacitor. When the residual voltage of the output capacitor is higher at the moment of power on, the stress of the output rectifier tube will be superimposed on the residual voltage, resulting in excessive voltage stress.

[0056] To this end, the present invention improves and optimizes the traditional asymmetric half-bridge circuit, and adds an output rectifier tube voltage stress control circuit. The output rectifier tube voltage stress control circuit accelerates the discharge of the residual voltage on the output capacitor after the input power is turned off, so that when the input power is connected again, the voltage stress on the output rectifier tube can be effectively reduced.

[0057] like Figure 2 As shown, the driving control circuit in the output rectifier tube voltage stress control circuit includes: a first voltage divider circuit and a MOS tube Q1; the first voltage divider circuit is a first series resistor voltage divider circuit, which is composed of resistors R1 and R2. The first voltage divider circuit is connected in parallel to both ends of the output capacitor EC2. The gate of the MOS tube Q1 is connected to the first voltage divider node A of the first voltage divider circuit. The drain of the MOS tube Q1 is the control signal output end of the driving control circuit. The source of the MOS tube Q1 is grounded.

[0058] The voltage discharge circuit in the output rectifier tube voltage stress control circuit specifically includes: a second voltage divider circuit, a MOS tube Q2 and a voltage divider network. The second voltage divider circuit is a second series resistor voltage divider circuit, which is composed of resistors R3 and R4. The second voltage divider circuit is connected in parallel to both ends of the output capacitor EC2. The output end of the drive control circuit (i.e., the drain of the MOS tube Q1) is connected to the gate of the MOS tube Q2, and is connected together to the second voltage divider node B of the second voltage divider circuit. The drain of the MOS tube Q2 is connected to the voltage divider network, and the source is grounded.

[0059] The voltage divider network is connected to the output end of the output rectifier tube D1 and connected to the voltage discharge circuit through the MOS tube Q2. In this example, the voltage divider network specifically includes a plurality of load resistors R5, R6, and R7 connected in parallel.

[0060] In this circuit, MOS tube Q1 serves as the control driving part of MOS tube Q2. According to the output voltage Vo and the voltage division and bias formed by resistors R1, R2, R3, and R4, the on and off states of MOS tube Q2 are determined to ensure that it is turned on at the right time and reduce conduction loss.

[0061] When the asymmetric half-bridge circuit is in steady-state operation, the MOS tube Q1 is turned on through the first voltage divider circuit, and the control signal output terminal outputs a first control signal that keeps the voltage discharge circuit off; the gate of the MOS tube Q2 receives the first control signal, and the MOS tube Q2 remains off.

[0062] After the input voltage of the asymmetric half-bridge circuit is turned off, the voltage across the output capacitor EC2 drops, and the MOS tube Q1 is turned off through the first voltage divider circuit. After the MOS tube Q1 is turned off, the resistors R3 and R4 form a pull-down path, so that the gate voltage of the MOS tube Q2 is pulled up, that is, the control signal output terminal outputs the second control signal that turns on the voltage discharge circuit. The MOS tube Q2 is turned on, and the voltage divider network is connected to the voltage discharge circuit, so that the residual voltage on the output capacitor EC2 is accelerated to be discharged through the voltage divider network.

[0063] It is further explained that the role of resistor R3 is mainly to provide a pull-down path after the MOS tube Q1 is turned off, so that the gate voltage of the MOS tube Q2 increases, ensuring that the MOS tube Q2 is reliably turned on. The role of resistor R4 is mainly to limit the gate current of the MOS tube Q2 to avoid overdriving, and at the same time provide a certain pull-down effect when the MOS tube Q1 is turned on to prevent the MOS tube Q2 from being mis-turned on. R3 and R4 work together to automatically trigger the load resistors R5, R6, and R7 to discharge the output capacitor when the input is turned off, thereby reducing the output rectifier tube voltage stress when the next power-on.

[0064] The asymmetric half-bridge circuit with output rectifier tube voltage stress control of the present invention can be used in the driving circuit of LED load, and provides a solution to the problem that the voltage stress of the output rectifier tube is higher than that of the traditional resistance load when the power supply is continuously turned on and off due to the particularity of the LED load.

[0065] In steady-state operation, the MOS tube Q1 is turned on and the MOS tube Q2 is turned off through the voltage division of the resistors R1 and R2. At this time, the parallel resistors R5, R6 and R7 forming the voltage division network are not connected to the circuit and no additional energy is consumed.

[0066] After the input power is turned off, when the output voltage drops to the LED off state (i.e., drops to the turn-on voltage threshold of the LED load), the residual voltage on the output capacitor EC2 continues to decrease, so that the voltage division of the resistors R1 and R2 is insufficient to maintain the conduction of the MOS tube Q1. At this time, the drain voltage of the MOS tube Q1 flips, and the MOS tube Q2 is turned on. Here, the resistance values ​​of the resistors R1 and R2 can be set according to the actual situation of the circuit application with the LED load, so that when the output voltage drops to the LED off state, the voltage division of the resistors R1 and R2 just reaches the critical value that is insufficient to maintain the conduction of the MOS tube Q1. The setting of the resistance values ​​of the resistors R1 and R2 based on the above ideas can be achieved by those skilled in the art without creative labor.

[0067] When the MOS tube Q2 is turned on, the parallel resistors R5, R6, and R7 are connected to the circuit to consume the residual voltage of the output capacitor EC2 as a load, so that the residual voltage on the output capacitor EC2 is quickly released through the voltage divider network, accelerating the drop of the residual voltage and preventing the residual voltage from being superimposed on the output rectifier tube D1 when the power is turned on again, thereby reducing transient voltage stress and improving the reliability of the power supply.

[0068] When the power is turned on again, the voltage stress of the output rectifier tube is effectively reduced because the residual voltage on the output capacitor EC2 has been reduced.

[0069] The present invention proposes an improved AHB circuit suitable for LED driving applications, specifically an asymmetric half-bridge circuit with output rectifier voltage stress control. Through the intelligent voltage stress control mechanism, the voltage stress of the output rectifier is effectively reduced, and the stress accumulation problem during continuous switching is avoided. This solution can not only improve the reliability of the circuit, but also reduce the cost of the output rectifier, making it more practical in LED driving applications.

[0070] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An asymmetric half-bridge circuit with output rectifier voltage stress control, characterized in that: The asymmetric half-bridge circuit with output rectifier tube voltage stress control comprises: an asymmetric half-bridge main power conversion circuit, an output rectifier circuit and an output rectifier tube voltage stress control circuit; The asymmetric half-bridge main power conversion circuit includes: a high-side switch tube Q3 and a low-side switch tube Q4, a resonant capacitor Cr and a transformer T1; wherein the high-side switch tube Q3 and the low-side switch tube Q4 form an asymmetric half-bridge structure for driving the primary winding Np of the transformer T1; the secondary winding Ns of the driving transformer T1 is connected to the output rectifier circuit; The output rectifier circuit includes an output rectifier tube D1 and an output capacitor EC2, which are used to convert the voltage of the secondary winding Ns of the transformer into an output voltage Vo; the output capacitor EC2 is connected between the output end of the output rectifier tube D1 and the ground; The output rectifier tube voltage stress control circuit is connected to the output end of the output rectifier circuit; the output rectifier tube voltage stress control circuit includes: a drive control circuit and a voltage discharge circuit; when the asymmetric half-bridge circuit is in steady-state operation, the drive control circuit outputs a first control signal to control the voltage discharge circuit to remain in an off state; after the input voltage of the asymmetric half-bridge circuit is turned off, the voltage across the output capacitor EC2 drops, and the drive control circuit outputs a second control signal to control the voltage discharge circuit to turn on, thereby accelerating the discharge of the residual voltage on the output capacitor EC2 through the voltage discharge circuit.

2. The asymmetric half-bridge circuit with output rectifier voltage stress control according to claim 1, characterized in that: The driving control circuit specifically includes: a first voltage divider circuit and a metal oxide semiconductor field effect transistor (MOS tube) Q1; The first voltage divider circuit is connected in parallel across the output capacitor EC2; The gate of the MOS transistor Q1 is connected to the first voltage-dividing node of the first voltage-dividing circuit; the drain of the MOS transistor Q1 is the control signal output terminal of the driving control circuit; When the asymmetric half-bridge circuit is in steady-state operation, the MOS transistor Q1 is turned on through the first voltage divider circuit, and the control signal output terminal outputs a first control signal that keeps the voltage discharge circuit turned off; After the input voltage of the asymmetric half-bridge circuit is turned off, the voltage across the output capacitor EC2 drops, the MOS tube Q1 is turned off through the first voltage divider circuit, and the control signal output terminal outputs a second control signal to turn on the voltage discharge circuit.

3. The asymmetric half-bridge circuit with output rectifier voltage stress control according to claim 2, characterized in that: The first voltage divider circuit is a first series resistor voltage divider circuit.

4. The asymmetric half-bridge circuit with output rectifier voltage stress control according to claim 1, characterized in that: The voltage discharge circuit specifically includes: a second voltage divider circuit, a MOS tube Q2 and a voltage divider network; The second voltage divider circuit is connected in parallel across the output capacitor EC2; The output terminal of the driving control circuit is connected to the gate of the MOS tube Q2, and is also connected to the second voltage dividing node of the second voltage dividing circuit; The voltage divider network is connected to the output end of the output rectifier tube D1 and is connected to the voltage discharge circuit through the MOS tube Q2; When the asymmetric half-bridge circuit is in steady-state operation, the gate of the MOS transistor Q2 receives the first control signal, and the MOS transistor Q2 remains turned off; After the input voltage of the asymmetric half-bridge circuit is turned off, the voltage across the output capacitor EC2 drops, the gate of the MOS tube Q2 receives the second control signal, the MOS tube Q2 is turned on, and the voltage divider network is connected to the voltage discharge circuit, so that the residual voltage on the output capacitor EC2 is accelerated to be discharged through the voltage divider network.

5. The asymmetric half-bridge circuit with output rectifier voltage stress control according to claim 4, characterized in that: The second voltage divider circuit is a second series resistor voltage divider circuit.

6. The asymmetric half-bridge circuit with output rectifier voltage stress control according to claim 4, characterized in that: The voltage divider network specifically includes a plurality of load resistors connected in parallel.

7. The asymmetric half-bridge circuit with output rectifier voltage stress control according to claim 1, characterized in that: The upper end of the high-side switch tube Q3 is connected to the input voltage, and the lower end is connected to the low-side switch tube Q4, and the lower end of the low-side switch tube Q4 is grounded; One end of the primary winding Np is connected to the input voltage, and the resonant capacitor Cr is connected in series between a common point between the high-side switch tube Q3 and the low-side switch tube Q4 and the other end of the primary winding Np.

8. The asymmetric half-bridge circuit with output rectifier voltage stress control according to claim 1, characterized in that: The asymmetric half-bridge main power conversion circuit also includes an input filter capacitor EC1.

9. The asymmetric half-bridge circuit with output rectifier voltage stress control according to claim 1, characterized in that: The asymmetric half-bridge circuit with output rectifier tube voltage stress control is used in a driving circuit of an LED load.

10. The asymmetric half-bridge circuit with output rectifier voltage stress control according to claim 9, characterized in that: After the input voltage of the asymmetric half-bridge circuit is turned off, the voltage across the output capacitor EC2 drops, and the drive control circuit outputs the second control signal to control the voltage discharge circuit to be turned on. Specifically, After the input voltage of the asymmetric half-bridge circuit is turned off, when the voltage across the output capacitor EC2 drops to the turn-on voltage threshold of the LED load, the drive control circuit outputs a second control signal to control the voltage discharge circuit to turn on.

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