Control circuit of asymmetric half-bridge flyback circuit, power module and electronic device

Abstract

The application provides a control circuit of an asymmetric half-bridge flyback circuit, a power module and an electronic device. The control circuit is used for outputting a control signal to control a main power tube and an auxiliary power tube. In response to an input voltage falling below a first voltage threshold, the auxiliary power tube is alternately turned off and turned on according to a first preset off time and a second preset on time. In response to the input voltage rising above a second voltage threshold, the main power tube and the auxiliary power tube are alternately turned on and turned off. The resonance capacitor and the resonance inductor of the asymmetric half-bridge flyback circuit constitute a resonance circuit, and the ratio of the second preset on time to the length of the resonance period of the resonance circuit is less than or equal to 0.25. The application can ensure the stable operation of the control circuit of the asymmetric half-bridge flyback circuit, the power module and the electronic device, and improve the service life.

Description

Technical Field

[0001] This application relates to the field of electronic power technology, and in particular to a control circuit, power supply module and electronic device for an asymmetric half-bridge flyback circuit. Background Technology

[0002] A power supply module typically includes a DC-DC converter circuit and a control circuit. The control circuit outputs control signals to control the DC-DC converter circuit. Taking an asymmetric half-bridge flyback circuit as an example, the asymmetric half-bridge flyback circuit includes a half-bridge circuit, a transformer, a resonant capacitor, and an output capacitor. The half-bridge circuit includes a main power transistor and an auxiliary power transistor. When the input voltage of the asymmetric half-bridge flyback circuit is in a low phase, the control circuit needs to control the asymmetric half-bridge flyback circuit to stop working.

[0003] Typically, the voltage across the output capacitor is V before the input voltage enters a low-phase state. o And the voltage across the resonant capacitor is N*V o After the input voltage enters a low phase, the voltage across the resonant capacitor can be maintained at N*V. o As the output load continues to pull down the voltage of the output capacitor in the asymmetric half-bridge flyback circuit, when it exits the low phase, the voltage of the output capacitor will become V. o_ini V o_ini Much smaller than V o This causes a mismatch between the voltage of the output capacitor and the voltage of the resonant capacitor. When the asymmetric half-bridge flyback circuit resumes operation, the control circuit controls the auxiliary power transistor to conduct, and the discharge of the resonant capacitor will generate an overshoot current. This will cause a huge current surge to the auxiliary power transistor and the rectifier circuit, affecting the life of the device and even causing direct damage to the device. Summary of the Invention

[0004] In view of this, this application provides a control circuit, power supply module, and electronic equipment for an asymmetric half-bridge flyback circuit, which can avoid overcurrent problems caused by the mismatch between the output capacitor voltage and the resonant capacitor voltage, ensure the stability of the power supply module and electronic equipment, and enhance the competitiveness of the product.

[0005] A first aspect of this application provides a power supply module including an asymmetric half-bridge flyback circuit and a control circuit. The asymmetric half-bridge flyback circuit receives an input voltage and provides an output voltage. The asymmetric half-bridge flyback circuit includes a transformer, a resonant capacitor, a main power transistor, and an auxiliary power transistor. The control circuit outputs a control signal to control the main power transistor and the auxiliary power transistor. In response to an input voltage drop below a first voltage threshold, the auxiliary power transistor alternately turns off and on according to a first preset off duration and a second preset on duration. In response to an input voltage rise above a second voltage threshold, the main power transistor and the auxiliary power transistor alternately turn on and off. The ratio of the second preset on duration to the resonant period of the asymmetric half-bridge flyback circuit is less than or equal to 0.25.

[0006] This application controls the main power transistor and the auxiliary power transistor through a control circuit, which can avoid overcurrent problems caused by the mismatch between the output capacitor voltage and the resonant capacitor voltage, reduce the current stress generated on the auxiliary power transistor and transformer during the discharge of the resonant capacitor, ensure the stable operation of the power module, and improve the service life of the power module.

[0007] As an optional implementation, the main power transistor is configured to remain off according to the control signal in response to the input voltage dropping below a first voltage threshold. This design can improve the efficiency of the power supply module.

[0008] As an optional implementation, the transformer includes a primary winding and a secondary winding. The source of the main power transistor is connected to the drain of the auxiliary power transistor and the first terminal of the primary winding. The source of the auxiliary power transistor is connected to a reference ground and one end of a resonant capacitor. The other end of the resonant capacitor is connected to the second terminal of the primary winding. The resonant capacitor discharges when the auxiliary power transistor is turned on and stops discharging when the auxiliary power transistor is turned off. This reduces the current stress generated on the auxiliary power transistor and the transformer during the discharge of the resonant capacitor, improving the stability of the power supply module.

[0009] As an optional implementation, the power module includes an auxiliary winding circuit, which includes an auxiliary winding for supplying power to the control circuit, and the auxiliary winding is coupled to the primary winding.

[0010] A second aspect of this application also provides a control circuit for an asymmetric half-bridge flyback circuit, the asymmetric half-bridge flyback circuit including a transformer, a resonant capacitor, a main power transistor, and an auxiliary power transistor. The control circuit is used to: obtain a comparison result of the input voltage value of the asymmetric half-bridge flyback circuit with a first voltage threshold or a second voltage threshold; in response to the input voltage value dropping below the first voltage threshold, control the auxiliary power transistor to alternately turn off and on according to a first preset off duration and a second preset on duration; in response to the input voltage value rising above the second voltage threshold, control the main power transistor and the auxiliary power transistor to alternately turn on and off; wherein the ratio of the second preset duration to the duration of the resonant period of the asymmetric half-bridge flyback circuit is less than or equal to 0.25. This application can control the main power transistor and the auxiliary power transistor through the control circuit, which can avoid the overcurrent problem caused by the mismatch between the output capacitor voltage and the resonant capacitor voltage, reduce the current stress generated on the auxiliary power transistor and transformer during the discharge current of the resonant capacitor, ensure the stable operation of the power module, and improve the service life of the power module.

[0011] As an optional implementation, the control circuit is also used to: control the main power transistor to remain off in response to the input voltage falling below a first voltage threshold, which can improve the efficiency of the power supply module.

[0012] As an optional implementation, the control circuit is used to obtain the second preset conduction duration based on the resonant period of the resonant circuit, or the control circuit is used to obtain the second preset conduction duration based on the resonant capacitor and the resonant inductor.

[0013] As an optional implementation, the control circuit is further configured to: in response to the input voltage dropping to below the first voltage threshold and the input voltage rising to above the second voltage threshold, acquire the voltage difference of the resonant capacitor before the auxiliary power transistor is turned on in two consecutive first cycles, wherein the duration of the first cycle is the sum of a first preset off duration and a second preset on duration; in response to the voltage difference of the resonant capacitor before the auxiliary power transistor is turned on in two consecutive first cycles not increasing and the input voltage rising to above the second voltage threshold, control the main power transistor to be turned on for a first duration in each second cycle; in response to the voltage difference of the resonant capacitor before the auxiliary power transistor is turned on in two consecutive first cycles increasing and the input voltage rising to above the second voltage threshold, control the main power transistor to be turned on for a second duration in each second cycle; wherein the second duration is longer than the first duration. With this design, after the power module exits intermittent mode and enters normal operating mode, the peak current of the main power transistor can be increased by increasing the on-time of the main power transistor in multiple cycles.

[0014] As an optional implementation, the control circuit is further configured to: in response to the input voltage dropping to below a first voltage threshold and the input voltage rising to above a second voltage threshold, acquire the voltage difference of the resonant capacitor before the auxiliary power transistor is turned on in two consecutive first cycles, wherein the duration of the first cycle is the sum of a first preset off duration and a second preset on duration; in response to the voltage difference of the resonant capacitor before the auxiliary power transistor is turned on in two consecutive first cycles being less than a third voltage threshold and the input voltage rising to above the second voltage threshold, control the main power transistor to be turned on for a first duration in each second cycle; in response to the voltage difference of the resonant capacitor before the auxiliary power transistor is turned on in two consecutive first cycles being greater than a third voltage threshold and the input voltage rising to above the second voltage threshold, control the main power transistor to be turned on for a second duration in each second cycle; wherein the second duration is longer than the first duration. This design helps the control circuit to confirm whether the power module is connected to a heavy load during intermittent states. With this design, after the power module exits intermittent mode and enters normal operation mode, the peak current of the main power transistor can be increased by increasing the conduction time of the main power transistor in multiple cycles.

[0015] A third aspect of this application also provides an electronic device, including a power module as described above, or a control circuit including an asymmetric half-bridge flyback circuit as described above.

[0016] The control circuit, power supply module, and electronic equipment of the asymmetric half-bridge flyback circuit of this application control the state of the auxiliary power transistor in the asymmetric half-bridge flyback circuit through the control circuit when the input voltage enters a low phase. This can avoid the overcurrent problem caused by the mismatch between the output capacitor voltage and the resonant capacitor voltage, improve the safety and stability of the power supply module, and enhance the competitiveness of the product. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application.

[0018] Figure 2 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application.

[0019] Figure 3 This is a schematic diagram of a power module provided in an embodiment of this application.

[0020] Figure 4 This is a schematic diagram of the circuit structure of a power supply module provided in an embodiment of this application.

[0021] Figure 5 This is a simplified circuit diagram of a power supply module.

[0022] Figure 6This is a schematic diagram of the equivalent circuit after the auxiliary power transistor in the power module is turned on.

[0023] Figure 7 A schematic diagram of the control logic of the control circuit provided in this application.

[0024] Figure 8 A schematic diagram of the control circuit provided in this application controlling the asymmetric half-bridge flyback circuit.

[0025] Figure 9 Another schematic diagram of the control circuit provided in this application for controlling the asymmetric half-bridge flyback circuit. Detailed Implementation

[0026] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] Please see Figure 1 , Figure 1 The diagram shown is a structural schematic of an electronic device 100 provided in one embodiment of this application.

[0029] like Figure 1 As shown, the electronic device 100 may include a power supply module 10 and a load 20. The power supply module 10 is used to receive an input voltage V. in and provides output voltage V out Power is supplied to the load 20. In one embodiment, the input voltage V in It can be powered by an external power source, or it can be powered by the internal power source of the electronic device 100. It is understood that, for example... Figure 1 The electronic device 100 provided in the illustrated embodiment can be a mobile phone, laptop computer, computer case, electric vehicle, smart speaker, smartwatch, or wearable device, etc. The power module 10 can be applied to, for example... Figure 1 In the electronic device 100 shown.

[0030] Please see Figure 2 , Figure 2The diagram shown is another structural schematic of the electronic device 100 provided in an embodiment of this application. Figure 2 As shown, the electronic device 100 may include a power supply module 10. The power supply module 10 can be used to receive an input voltage V. in and provides output voltage V out This provides power to the load subsequently connected to the electronic device 100. In one embodiment, the input voltage V in It can be powered by an external power source, or it can be powered by the internal power source of the electronic device 100.

[0031] like Figure 2 As shown, the electronic device 100 provided in this embodiment can be a power adapter, charger, power bank, or other power supply device. The power module 10 provided in this embodiment can be applied to, for example... Figure 2 In the electronic device 100 shown.

[0032] In one embodiment of this application, the electronic device 100 may further include a plurality of power modules 10, which provide an output voltage V. out The power supply module 10 provides power to the load 20. In one embodiment of this application, the electronic device 100 may include multiple loads 20, and the power module 10 may provide multiple output voltages V. out The electronic device 100 provides power to multiple loads 20 respectively. In one embodiment of this application, the electronic device 100 may include multiple power modules 10 and multiple loads 20, and the multiple power modules 10 may respectively provide multiple output voltages V. out Powers multiple loads 20.

[0033] In one embodiment of this application, the input voltage V in The power supply can be alternating current, and the power module 10 may include an AC / DC conversion circuit. In this embodiment, the input voltage V... in The power supply can be direct current (DC), and the internal power source may include an energy storage device. The power module 10 may include a DC-DC converter circuit. Accordingly, when the electronic device 100 is operating independently, the energy storage device of the internal power source can supply power to the power module 10.

[0034] In one embodiment of this application, the input voltage V inThe power supply can be direct current (DC). The load 20 of the electronic device 100 may include one or more of a power-consuming device, an energy storage device, or an external device. In one embodiment, the load 20 may be a power-consuming device of the electronic device 100, such as a processor or a display. In one embodiment, the load 20 may be an energy storage device of the electronic device 100, such as a battery. In one embodiment, the load 20 may be an external device of the electronic device 100, such as a display, a keyboard, or other electronic devices.

[0035] Please see Figure 3 , Figure 3 The diagram shown is a structural schematic of a power module provided in an embodiment of this application. Figure 3 As shown, the power supply module 10 includes a control circuit 11, a DC-DC converter circuit 12, an auxiliary winding circuit 13, and a rectifier circuit 14. The power supply module 10 is used to receive the input voltage V provided by the input power supply. in and provides output voltage V out Power is supplied to load 20.

[0036] The control circuit 11 is connected to the DC-DC converter 12. The control circuit 11 can be used to control the operation of the DC-DC converter 12. In one embodiment, the control circuit 11 can be used to output a control signal, which can be used to control the DC-DC converter 12. For example, the input terminal of the DC-DC converter 12 is used to receive an input voltage V. in The control circuit 11 controls the DC-DC converter 12 to adjust the input voltage V. in After processing, an output voltage V1 is provided. In this embodiment of the application, the input voltage V... in It is direct current.

[0037] The rectifier circuit 14 can be used to rectify the output voltage V1 provided by the DC-DC converter circuit 12 and then provide the output voltage V. out .

[0038] The auxiliary winding circuit 13 can be used to receive power from the transformer in the DC-DC converter circuit 12 and to supply power to the control circuit 11. In this embodiment, the auxiliary winding circuit 13 may include a voltage regulator circuit, etc.

[0039] Please see Figure 4 , Figure 4 This is a schematic diagram of the circuit structure of a power supply module provided in an embodiment of this application. Figure 4 As shown, the power module 10 includes a DC-DC converter circuit 12, a rectifier circuit 14, an auxiliary winding circuit 13, and a control circuit 11.

[0040] The example of the DC-DC converter circuit 12 in the power supply module 10 is an asymmetrical half-bridge (AHB) flyback circuit 12a. The asymmetrical half-bridge flyback circuit 12a may include a half-bridge circuit 121, a transformer 122, and a resonant capacitor Cr.

[0041] The half-bridge circuit 121 may include the main power transistor Q. L and auxiliary power transistor Q H The main power transistor Q L and the auxiliary power transistor Q H An asymmetric half-bridge topology can be formed. In one embodiment, the control circuit 11 can send signals to the main power transistor Q. L and auxiliary power transistor Q H Send a control signal so that the main power transistor Q... L and the auxiliary power transistor Q H It can be turned on according to the received control signal. The main power transistor Q L The drain receives the input voltage V in The main power transistor Q L The source of the auxiliary power transistor Q H The drain of the auxiliary power transistor Q is connected to the drain of the transistor. H The source of the transistor is connected to the reference ground. The main power transistor Q... L The gate of the auxiliary power transistor Q can be used to receive a first control signal sent by the control circuit 11, and can be turned on according to the first control signal. H The gate can be used to receive the second control signal of the control circuit 11, and can be turned on according to the second control signal.

[0042] It should be noted that, in the embodiments of this application, the main power transistor and the auxiliary power transistor can be metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), bipolar power transistors, or wide-bandgap semiconductor field-effect transistors, etc.

[0043] In the embodiments of this application, the main power transistor and the auxiliary power transistor can be different types of transistors. For example, the main power transistor is a MOSFET, and the auxiliary power transistor is an IGBT. Alternatively, the main power transistor and the auxiliary power transistor can be the same type of transistor. For example, both the main power transistor and the auxiliary power transistor are MOSFETs. It is understood that the embodiments of this application only use MOSFETs as an example to illustrate the main power transistor and the auxiliary power transistor, but the embodiments of this application do not limit the transistor type of the main power transistor and the auxiliary power transistor.

[0044] In this embodiment, the main power transistor and the auxiliary power transistor are driven by a high-level signal to turn on and a low-level signal to turn off. For example, the main power transistor turns on when it receives a high-level drive signal and turns off when it receives a low-level drive signal. It is understood that other driving methods can also be used for the main power transistor and the auxiliary power transistor in this embodiment, and this embodiment does not limit the driving method of the main power transistor and the auxiliary power transistor.

[0045] The control circuit 11 provided in this application embodiment may include a pulse-width modulation (PWM) controller, a central processing unit (CPU), other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, etc.

[0046] The half-bridge circuit 121 can be used to receive the input voltage V. inAccording to the control signal provided by the control circuit 11, the output voltage is provided to the primary winding 1221 of the transformer 122 through the resonant capacitor Cr. The transformer 122 includes a primary winding 1221, a secondary winding 1222, and a magnetic core 1223. The secondary winding 1222 of the transformer 122 is coupled to the primary winding 1221 through the magnetic core 1223, and the auxiliary winding 131 is coupled to the primary winding 1221 of the transformer 122 through the magnetic core 1223. The primary winding 1221 of the transformer 122 is used to receive the output voltage of the half-bridge circuit 121 and can generate the primary winding voltage. The secondary winding 1222 of the transformer 122 is coupled to the primary winding 1221, and a secondary winding voltage can be generated on the secondary winding 1222. The rectifier circuit 14 can be used to receive the secondary winding voltage on the secondary winding 1222 and convert it into an output voltage V. out .

[0047] It is understandable that the primary winding can refer to the winding placed at the primary side of the transformer, corresponding to the input voltage V. in The secondary winding is the winding that carries the current from the transformer. The secondary winding can refer to the winding located on the secondary side of the transformer that carries the current corresponding to the output voltage V1. The auxiliary winding circuit 13 may include an auxiliary winding that is coupled to the transformer.

[0048] like Figure 4 In the example shown, one end of the resonant capacitor Cr can be connected to the auxiliary power transistor Q. H The source of the resonant capacitor Cr is connected to the first terminal of the primary winding 1221 and the resonant inductor L. m The first end of the primary winding 1221 and the second end of the primary winding 1221 are connected to the main power transistor Q through the resonant inductor Lr. L The source and the auxiliary power transistor Q H The drain of the resonant inductor L. m The second end is connected to the second end of the primary winding 1221. The output voltage V1 provided by the secondary winding 1222 of the transformer 122 is processed by the rectifier circuit 14 to provide the output voltage V. out .

[0049] In one embodiment, the rectifier circuit 14 may include a diode D1 and an output capacitor C1. The anode of the diode D1 is connected to a first terminal of the secondary winding 1222. The two terminals of the output capacitor C1 are respectively connected to the cathode of the diode D1 and a second terminal of the secondary winding 1222.

[0050] The half-bridge circuit 121 may include diode D2, diode D3, capacitor C2, and capacitor C3. The cathode of diode D2 is connected to the first terminal of capacitor C2 and the main power transistor Q. LThe drain of diode D2 is connected to the second terminal of capacitor C2 and the main power transistor Q. L The source of the diode. The cathode of the diode D3 is connected to the first terminal of the capacitor C3 and the auxiliary power transistor Q. H The drain of diode D3 is connected to the second terminal of capacitor C3 and the auxiliary power transistor Q. H The source pole.

[0051] The auxiliary winding circuit 13 may include an auxiliary winding 131. The auxiliary winding 131 can be coupled to the primary winding 1221 through the magnetic core 1223. The primary winding voltage on the primary winding 1221 is coupled to generate an auxiliary winding voltage on the auxiliary winding 131. The auxiliary winding circuit 13 can supply power to the control circuit 11 according to the auxiliary winding voltage. The auxiliary winding circuit 13 may include a boost circuit, a buck circuit, a buck-boost circuit, etc. In one embodiment, the auxiliary winding circuit 13 may also be a low dropout regulator (LDO) or other voltage regulator circuit.

[0052] In one embodiment, the control circuit 11 can send a control signal to control the main power transistor Q in the half-bridge circuit 121 of the asymmetric half-bridge flyback circuit 12a. L and auxiliary power transistor Q H This controls the operating state of the asymmetric half-bridge flyback circuit 12a. For example, by adjusting the frequency or duty cycle of the control signal, the control circuit 11 can control the main power transistor Q in the half-bridge circuit 121. L and auxiliary power transistor Q H The conduction frequency or conduction duration is adjusted accordingly, thereby adjusting the output voltage value of the half-bridge circuit 121, and further adjusting the output voltage V1 value of the asymmetric half-bridge flyback circuit 12a, and controlling the output voltage V of the power supply module 10. out The voltage value. In one embodiment, the control circuit 11 can send a control signal to control the main power transistor Q in the half-bridge circuit 121. L and auxiliary power transistor Q H The conduction and shutdown.

[0053] For example, the control circuit 11 can control the main power transistor Q by sending a signal to the main power transistor Q. L The main power transistor Q is controlled by sending a first control signal. L Turning the transistor on or off, and by supplying power to the auxiliary power transistor Q. H The auxiliary power transistor Q is controlled by sending a second control signal. HTo turn on or off. In embodiments of this application, the first control signal and the second control signal may include implementations such as high-level signals or low-level signals. In one embodiment, the main power transistor Q... L The auxiliary power transistor Q can be turned on according to the first control signal. H It can be turned on according to the second control signal. In one embodiment, the main power transistor Q... L The auxiliary power transistor Q can be turned off according to the first control signal. H It can be turned off according to the second control signal, etc.

[0054] Figure 5 This is a simplified circuit diagram of a power supply module. Based on... Figure 4 The power module 10 shown can provide the following: Figure 5 The simplified circuit is shown. In this circuit, the primary winding 1221 of the transformer 122 in the asymmetric half-bridge flyback circuit 12a can provide a resonant inductance Lr. For example, the resonant inductance Lr can be parasitic on the primary winding 1221 of the transformer 122. The main power transistor Q of the asymmetric half-bridge flyback circuit 12a... L and auxiliary power transistor Q H Alternating on and off. The output voltage V of the power module 10. out Stabilize at the rated output voltage, and record the rated output voltage value as V. o Meanwhile, based on the simplified circuit, an approximate equation V can be obtained. cr ≈N*V out , where V cr is the voltage across the resonant capacitor Cr, and N is the turns ratio of the primary winding 1221 and the secondary winding 1222 of the transformer 122.

[0055] Although in the asymmetric half-bridge flyback circuit 12a, the main power transistor Q L and auxiliary power transistor Q H When the circuit is alternately switched on, the voltage across the resonant capacitor Cr is equal to the output voltage V of the power supply module 11. out The relationship expressed by the above approximate equation exists. However, in some cases, the voltage across the resonant capacitor Cr may be much higher than N*V. out This makes the above approximate equation impossible to hold. For example, when the control circuit 11 periodically supplies power to the main power transistor Q in the asymmetric half-bridge flyback circuit 12a... L and auxiliary power transistor Q H Sending control signals to control the main power transistor Q L and auxiliary power transistor Q H Alternating between on and off. At this time, the output voltage V of the power module 10... out Stabilize at the rated voltage. Subsequently, if the input voltage Vin When the phase is low, the control circuit 11 needs to control the asymmetric half-bridge flyback circuit 12a to stop working, that is, to prevent the main power transistor Q of the asymmetric half-bridge flyback circuit 12a from working. L and auxiliary power transistor Q H The entire system is in a switched-off state. At this time, the voltage across the resonant capacitor Cr can be maintained at N*V. out As the output load continues to pull down the voltage across the output capacitor of the asymmetric half-bridge flyback circuit, the voltage across capacitor C1 will become V. o_ini V o_ini It will be much smaller than V out .

[0056] At the input voltage V in When entering the high phase, the control circuit 11 can then control the asymmetric half-bridge flyback circuit 12a from the main power transistor Q. L and auxiliary power transistor Q H The system switches back to the operating state from the off state. The control circuit 11 supplies power to the main power transistor Q in the asymmetric half-bridge flyback circuit 12a. L and auxiliary power transistor Q H Send a control signal to cause the main power transistor Q to... L and the auxiliary power transistor Q H The system alternately turns the circuit on and off based on control signals.

[0057] Figure 6 This is a schematic diagram of the equivalent circuit after the auxiliary power transistor Q in the power supply module is turned on. It can be seen that when the auxiliary power transistor Q in the power supply module 10 is turned on... H After conduction, the voltage V across the resonant capacitor Cr is cr It may be much greater than the output voltage V at the output terminal of power module 10. out *N. Therefore, the current generated by the resonant capacitor Cr will be directly transmitted to the secondary rectifier circuit 14 through the transformer 122. Therefore, when the auxiliary power transistor Q... H After being turned on, the resonant capacitor Cr generates an overshoot current, which is then transmitted through the auxiliary power transistor Q. H Extremely high current stress is generated on the transformer 122 and the rectifier circuit 14.

[0058] This application provides a control circuit, power supply module, and electronic device for an asymmetric half-bridge flyback circuit, which can be used to overcome the above-mentioned problems. The technical solution of this application is described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0059] Figure 7This is a schematic diagram of the control logic of the control circuit provided in the embodiment of this application.

[0060] The control circuit 11 can be applied to, for example... Figure 4 The power supply module 10 shown. The control circuit 11 provided in this application can be used to control, for example, Figure 4 The asymmetric half-bridge flyback circuit 12a shown is used for control. Figure 7 In the example shown, DC-DC converter circuit 12 is used as an example. Figure 4 The asymmetric half-bridge flyback circuit 12a in the example is used here. It can be understood that the control logic executed by the control circuit 11 provided in this application can also be applied to the control circuit 11 to control other types of DC-DC converter circuits 12.

[0061] Combination Figure 4 The circuit diagram shown indicates that when the auxiliary power transistor Q... H When the circuit is turned on, the resonant capacitor Cr can pass through the primary winding 1221, the resonant inductor Lr, and the auxiliary power transistor Q. H Discharge. When the auxiliary power transistor Q... H When shut down, the resonant capacitor Cr stops discharging.

[0062] It is understood that the control circuit 11 can control the input voltage V of the asymmetric half-bridge flyback circuit 12a. in The detection is performed. If the control circuit 11 receives the input voltage V... in The voltage drops to less than or equal to the first voltage value V. in1 That is, the asymmetric half-bridge flyback circuit 12a has entered intermittent mode, and the control circuit 11 will execute as follows: Figure 7 The control logic is shown. For example, the control circuit 11 can control the auxiliary power transistor Q. H The auxiliary power transistor Q is periodically switched on and off alternately. H The duration of each shutdown according to the first control signal of the control circuit 11 is a first preset shutdown duration T1. The auxiliary power transistor Q... H The duration of each conduction of the second control signal of the control circuit 11 is a second preset conduction duration T2. ​​In other words, when the input voltage V... in The voltage drops below the first voltage threshold V. in1 At that time, the auxiliary power transistor Q H The device can alternately turn off and on based on the first preset off duration T1 and the second preset on duration T2.

[0063] like Figure 7 As shown, when the control circuit 11 receives the input voltage V in The voltage drops to less than or equal to the first voltage value V. in1At that time, the control circuit 11 outputs a first control signal to the auxiliary power transistor Q. H To control the auxiliary power transistor Q H Shut down the first preset duration T1.

[0064] like Figure 7 As shown, in the auxiliary power transistor Q H After the first preset shutdown time T1 is turned off according to the first control signal, the voltage V across the resonant capacitor Cr is... cr It is already greater than the reflected voltage N*V of the output capacitor C1. out The control circuit 11 outputs a second control signal to the auxiliary power transistor Q. H To control the auxiliary power transistor Q H The second preset conduction duration T2 is activated.

[0065] It is understood that the second preset conduction time T2 is less than a predetermined value. The predetermined value can be 25% of the resonant period of the resonant circuit in the half-bridge circuit 121. For example, the second preset conduction time T2 can be 10%-15% of the resonant period. When the resonant time of the zero-input corresponding resonance of the resonant circuit is less than 25% of the resonant period, the voltage V across the resonant capacitor Cr... cr It will not exceed the reflected voltage N*V of the output capacitor C1. out And the voltage change ΔV of the resonant capacitor Cr Cr Proportional to the auxiliary power transistor Q H Before conduction, the voltage V across the resonant capacitor Cr is cr With N*V out The voltage difference can effectively limit the resonance duration and reduce the overshoot current of the resonant circuit.

[0066] In the auxiliary power transistor Q H During the periodic alternating switching on and off process, the resonant capacitor Cr periodically stops discharging and discharges alternately, thus allowing the charge within the resonant capacitor Cr to be gradually released. Figure 7 The voltage value V of the resonant capacitor Cr shown is... cr On the waveform diagram, the voltage across the resonant capacitor Cr exhibits a step-like decreasing pattern.

[0067] It is understood that in this embodiment, the first preset turn-off duration T1 and the second preset turn-on duration T2 can be preset fixed values, or they can be calculated by the control circuit. For example, the first preset turn-off duration T1 and the second preset turn-on duration T2 can be pre-set fixed values.

[0068] In one embodiment, the control circuit 11 can acquire the circuit parameters of the asymmetric half-bridge flyback circuit 12a through a Universal Asynchronous Receiver / Transmitter (UART) interface or other means. The circuit parameters may include the capacitance value of the resonant capacitor Cr, the inductance value of the resonant inductor Lr, the frequency fpre of the control signal sent by the control circuit 11, and the preset number 20 of the auxiliary power transistor QH being turned on. The circuit parameters acquired by the control circuit 11 can be configured by engineers. The control circuit 11 can calculate a first preset turn-off duration T1 and a second preset turn-on duration T2 based on these circuit parameters. In some embodiments, the second preset turn-on duration T2 can be 10%-15% of the resonant period length formed by the resonant capacitor Cr and the resonant inductor Lr, for example, a second preset turn-on duration T2 of 300 ns. It can be understood that, to balance the voltage difference before each discharge with the number of discharges, the first preset turn-off duration T1 can be set to 250 μs.

[0069] During the time interval 0-t1, the control circuit 11 controls the auxiliary power transistor Q. H The circuit is switched off to stop the resonant capacitor Cr from discharging. The voltage V across the resonant capacitor Cr... cr It can remain unchanged from time 0 to t1. From time t1 to t2, the control circuit 11 controls the auxiliary power transistor Q. H The circuit is turned on so that the resonant capacitor Cr discharges, and the voltage V across the resonant capacitor Cr... cr It begins to decrease. At time t2, the voltage V across the resonant capacitor Cr... cr With N*V out The difference is less than a preset value. The preset value can be set relatively small. At time t2, the voltage V across the resonant capacitor Cr is... cr Approximately and slightly greater than N*V out So that the approximate equation Vcr≈N*V is achieved. out Established.

[0070] Between time t2 and t3, the control circuit 11 controls the auxiliary power transistor Q. H The circuit is switched off to stop the resonant capacitor Cr from discharging. During the time interval t3-t4, the control circuit 11 controls the auxiliary power transistor Q. H The circuit is turned on so that the resonant capacitor Cr discharges, and the voltage V across the resonant capacitor Cr... cr The voltage V across the resonant capacitor Cr decreases at time t4. cr With N*V outThe difference is less than the preset value. At time t4, the voltage V across the resonant capacitor Cr is... cr Approximately and slightly greater than N*V out So that the approximate equation Vcr≈N*V is achieved. out Established.

[0071] The control circuit 11 controls the auxiliary power transistor Q. H The system alternately turns off and on periodically until the input voltage V is detected. in Rise to a value greater than or equal to the second voltage value V in2 At that time, the control circuit 11 will control the main power transistor Q. L and auxiliary power transistor Q H Alternating on and off. At this time, the asymmetric half-bridge flyback circuit 12a exits the intermittent mode and can operate in normal working condition, outputting a rated voltage according to the input voltage. In the main power transistor Q... L and the auxiliary power transistor Q H When the capacitor is alternately turned on and off, the voltage V across the resonant capacitor Cr is... cr Approximately and slightly greater than N*V out This ensures that the discharge current of the resonant capacitor Cr will not affect the auxiliary power transistor Q. H Extremely high current stress is generated on the transformer 122 and the rectifier circuit 14.

[0072] In summary, the control circuit 11 provided in this application embodiment controls the asymmetric half-bridge flyback circuit 12a, reducing the current discharge of the resonant capacitor Cr during the discharge of the auxiliary power transistor Q. H The current stress generated on the transformer 122 and the rectifier circuit 14 ensures the stable operation of the asymmetric half-bridge flyback circuit 12a, the power supply module 10 and the electronic equipment 100, and improves the service life of the asymmetric half-bridge flyback circuit 12a, the power supply module 10 and the electronic equipment 100.

[0073] Figure 8 This is a schematic diagram of the control circuit for controlling an asymmetric half-bridge flyback circuit according to an embodiment of this application.

[0074] In S81, the asymmetric half-bridge flyback circuit 12a is controlled to operate in normal working condition.

[0075] by Figure 4 Taking the power module 10 shown as an example, the control circuit 11 can control the asymmetric half-bridge flyback circuit 12a to operate in a normal working state, that is, the control circuit 11 controls the main power transistor Q. L and the auxiliary power transistor Q H Alternately turn on and off.

[0076] In S82, it checks whether the input voltage has dropped to less than or equal to a first voltage value. If the input voltage drops to less than or equal to the first voltage value, it executes S83; otherwise, it returns to S82.

[0077] It is understood that the control circuit 11 can obtain the input voltage V in The magnitude of the input voltage V. When the control circuit 11 receives the input voltage V in The voltage drops to less than or equal to the first voltage value V. in1 When the asymmetric half-bridge flyback circuit 12a is in time, it is controlled to enter an intermittent state.

[0078] In S83, the auxiliary power transistor is turned off for a first preset turn-off time T1.

[0079] When the input voltage V in The voltage drops to less than or equal to the first voltage value V. in1 At that time, after the asymmetric half-bridge flyback circuit 12a enters the intermittent mode, the control circuit 11 controls the auxiliary power transistor Q in the asymmetric half-bridge flyback circuit 12a. H Shut down the first preset duration T1.

[0080] In S84, the auxiliary power transistor is turned on for a second preset on-time T2.

[0081] The control circuit 11 controls the auxiliary power transistor Q. H After the first preset shutdown duration T1 is turned off, the auxiliary power transistor Q is then controlled. H The circuit is turned on for a second preset on-time T2. This second preset on-time T2 can be less than a predetermined value. The predetermined value can be 25% of the resonant period of the resonant circuit in the half-bridge circuit 121. For example, the second preset on-time T2 can be 10%-15% of the resonant period. Specifically, the resonant time at which the resonant circuit achieves zero-input resonance is less than 25% of the resonant period.

[0082] The first preset shutdown duration T1 and the second preset turn-on duration T2 can be preset fixed values, or they can be calculated by the control circuit 11. For example, the first preset shutdown duration T1 and the second preset turn-on duration T2 can be pre-set fixed values.

[0083] In S85, it checks whether the input voltage has risen to a level greater than or equal to the second voltage value. If the input voltage has risen to a level greater than or equal to the second voltage value, it executes S86; otherwise, it returns to S83.

[0084] The control circuit 11 detects the input voltage V. in The voltage value, if the input voltage Vin Rise to a value greater than or equal to the second voltage value V in2 This indicates that the asymmetric half-bridge flyback circuit 12a can exit intermittent mode. If the input voltage V in Rise to a value greater than the second voltage value V in2 This indicates that the control circuit 111 needs to repeatedly execute S83-S84 until the input voltage V... in Rise to a value greater than or equal to the second voltage value V in2 .

[0085] In S86, the asymmetric half-bridge flyback circuit 12a is controlled to operate in normal working condition.

[0086] The control circuit 11 responds to the input voltage Vin rising to a value greater than or equal to the second voltage value V. in2 At that time, the asymmetric half-bridge flyback circuit 12a is controlled to operate in normal working state, so that the control circuit 11 controls the main power transistor Q. L and the auxiliary power transistor Q H Alternately turn on and off.

[0087] The control circuit of the asymmetric half-bridge flyback circuit provided in this application embodiment stops operating in the conventional mode when the input voltage drops below a first voltage value and enters intermittent control until the input voltage rises above a second voltage value, at which point the asymmetric half-bridge flyback circuit resumes operating in the conventional mode. For example, in the intermittent control of the asymmetric half-bridge flyback circuit, the control circuit controls the auxiliary power transistor in the asymmetric half-bridge flyback circuit to turn off for a first preset turn-off duration T1, and then controls the auxiliary power transistor to turn on for a second preset turn-on duration T2. ​​The second preset turn-on duration T2 is less than 25% of the resonant period of the resonant cavity composed of the resonant inductor and resonant capacitor in the asymmetric half-bridge flyback circuit. This reduces the current stress generated by the discharge current of the resonant capacitor on the auxiliary power transistor, transformer, and rectifier circuit, ensuring the stable operation of the asymmetric half-bridge flyback circuit, power supply module, and their associated electronic equipment, and improving the service life of the asymmetric half-bridge flyback circuit, power supply module, and electronic equipment.

[0088] Figure 9 This is a schematic diagram of the control circuit for controlling an asymmetric half-bridge flyback circuit, provided in another embodiment of this application.

[0089] In S91, the asymmetric half-bridge flyback circuit 12a is controlled to operate in normal working condition.

[0090] by Figure 4 Taking the power module 10 shown as an example, the control circuit 11 can control the main power transistor Q.L and the auxiliary power transistor Q H Alternately turn on and off.

[0091] In S92, it checks whether the input voltage has dropped to less than or equal to a first voltage value. If the input voltage drops to less than or equal to the first voltage value, then S93 is executed; otherwise, it returns to S92.

[0092] If the control circuit 11 detects the input voltage V in The voltage drops to less than or equal to the first voltage value V. in1 At that time, the control circuit controls the asymmetric half-bridge flyback circuit 12a to enter an intermittent state.

[0093] In S93, the auxiliary power transistor is turned off.

[0094] In S94, the voltage across the resonant capacitor is acquired and recorded as V. cr_pre .

[0095] In the auxiliary power transistor Q H After being turned off, the control circuit 11 can begin to acquire the voltage across the resonant capacitor Cr and record the acquired voltage as V. cr_pre .

[0096] It is understood that, in some embodiments, the control circuit 11 can measure the voltage V across the resonant capacitor using a resistor divider network. cr It can be converted into a digital quantity by an analog-to-digital converter.

[0097] In S95, it is confirmed whether the turn-off time of the auxiliary power transistor has reached the first preset turn-off duration. If the turn-off time of the auxiliary power transistor has reached the first preset turn-off duration, then S96 is executed; otherwise, return to S95.

[0098] In S96, the auxiliary power transistor is turned on for a second preset on-time.

[0099] The control circuit 11 controls the auxiliary power transistor Q. H After the first preset shutdown duration T1 is turned off, the auxiliary power transistor Q will then be controlled. H The circuit is turned on for a second preset on-time T2. This second preset on-time T2 can be less than a predetermined value. The predetermined value can be 25% of the resonant period of the resonant circuit in the half-bridge circuit 121. For example, the second preset on-time T2 can be 10%-15% of the resonant period. Specifically, the resonant time at which the resonant circuit achieves zero-input resonance is less than 25% of the resonant period.

[0100] In S97, the auxiliary power transistor is turned off.

[0101] In S98, the voltage across the resonant capacitor is acquired and recorded as V. cr .

[0102] In the auxiliary power transistor Q H After being turned off, the control circuit 11 can begin to acquire the voltage across the resonant capacitor Cr and record the acquired voltage as V. cr At this time, V cr It can be an auxiliary power transistor Q H The resonant capacitor voltage before the next cycle turns on. V cr_pre It can be an auxiliary power transistor Q H The resonant capacitor voltage before the previous cycle's conduction. In other words, the control circuit 11 can respond to the input voltage V. in The voltage drops to less than the first voltage value V. in1 With the input voltage V in Rise to a value greater than the second voltage value V in2 Between, obtain the auxiliary power transistor Q in two consecutive first cycles. H The voltage difference of the resonant capacitor Cr before it is turned on. The duration of the first cycle is the sum of the first preset turn-off duration T1 and the second preset turn-on duration T2.

[0103] It is understandable that if the auxiliary power transistor Q is in two consecutive first cycles... H Before conduction, the voltage difference of the resonant capacitor did not increase and the input voltage V in Rise to a value greater than the second voltage value V in2 The control circuit 11 can control the main power transistor Q. L The auxiliary power transistor Q is turned on for the first duration during each second cycle. H Before conduction, the voltage difference across the resonant capacitor Cr increases and the input voltage V... in Rise to a value greater than the second voltage value V in2 The control circuit 11 can control the main power transistor Q. L The circuit is activated for a second duration within each second cycle. The second duration is longer than the first duration.

[0104] In S99, check if the overload flag is 1. If it is, proceed to S100; otherwise, proceed to S101.

[0105] In S100, it checks whether the input voltage has risen to a level greater than or equal to the third voltage value. If the input voltage has risen to a level greater than or equal to the third voltage value, it proceeds to S107. Otherwise, it proceeds to S102.

[0106] The control circuit 11 can detect the input voltage V. in And determine the input voltage V in Does it rise to a value greater than or equal to the third voltage value V? in3 .

[0107] In S101, it is detected whether the input voltage rises to a level greater than or equal to the second voltage value. If the input voltage rises to a level greater than or equal to the second voltage value, proceed to S107. Otherwise, proceed to S102.

[0108] It is understood that the control circuit 11 can also determine the input voltage V. in Does it rise to a level greater than or equal to the second voltage value V? in2 .

[0109] In S102, confirm V cr and V cr_pre Pressure difference ΔV between cr Is it less than a preset threshold? If △V cr If the value is less than the preset threshold, proceed to S103; otherwise, proceed to S104.

[0110] The control circuit 11 can be used in the auxiliary power transistor Q H Before conduction, the voltage V across the resonant capacitor Cr is measured. cr And the voltage V cr Compared to the previous auxiliary power transistor Q H V collected before conduction cr_pre Subtract.

[0111] In S103, it was confirmed that the power module was not connected to a heavy load.

[0112] In this embodiment, when the pressure difference ΔV cr Less than the preset threshold V th At that time, the control circuit 11 can confirm that the power module 10 is not connected to a heavy load.

[0113] In S104, it is confirmed that the power module is connected to a heavy load.

[0114] In this embodiment, when the pressure difference ΔV cr Greater than the preset threshold V th At that time, the control circuit can confirm that the power module 10 has been connected to heavy load in the intermittent state.

[0115] It is understandable that if the auxiliary power transistor Q is in two consecutive first cycles... H Before conduction, the voltage difference of the resonant capacitor is less than a preset threshold V. th And the input voltage V in Rise to a value greater than the second voltage value V in2The control circuit 11 can control the main power transistor Q. L The auxiliary power transistor Q is turned on for the first duration during each second cycle. H Before conduction, the voltage difference across the resonant capacitor Cr is greater than a preset threshold V. th And the input voltage V in Rise to a value greater than the second voltage value V in2 The control circuit 11 can control the main power transistor Q. L The second duration is activated within each second cycle.

[0116] In S105, V cr The value assigned to V cr_pre .

[0117] Subsequently, the control circuit 11 can also convert V cr The value assigned to V cr_pre .

[0118] In S106, it is confirmed whether the turn-off time of the auxiliary power transistor has reached the first preset turn-off duration. If the turn-off time of the auxiliary power transistor has reached the first preset turn-off duration, proceed to S96; otherwise, return to S106.

[0119] In S107, the asymmetric half-bridge flyback circuit 12a is controlled to operate in normal working condition.

[0120] This application also provides an electronic device, including a control circuit 11 as provided in any embodiment of this application, or a power module 10 as provided in any embodiment of this application.

[0121] In the foregoing embodiments, the method executed by the control circuit 11 provided in the embodiments of this application has been described. To realize the functions of the methods provided in the embodiments of this application, the control circuit 11, as the execution subject, may include hardware structures and / or software modules, implementing the above functions in the form of hardware structures, software modules, or a combination of hardware structures and software modules. Whether a particular function is executed in the form of hardware structures, software modules, or a combination of hardware structures and software modules depends on the specific application and design constraints of the technical solution. It should be noted that the division of the various modules in the above device is merely a logical functional division; in actual implementation, they can be fully or partially integrated into a single physical entity, or physically separated. Furthermore, these modules can all be implemented by software through processing element calls; they can all be implemented in hardware; or some modules can be implemented by processing element calls to software, and some modules can be implemented in hardware. A separate processing element can be established, or it can be integrated into a chip in the above device. Alternatively, it can be stored in the memory of the above device as program code, and called and executed by a processing element of the above device. The implementation of other modules is similar. Furthermore, these modules can be integrated, either wholly or partially, or implemented independently. The processing element described here can be an integrated circuit with signal processing capabilities. During implementation, each step of the above method or each of the above modules can be completed through integrated logic circuits in the hardware of the processor element or through software instructions. For example, these modules can be one or more integrated circuits configured to implement the above method, such as one or more application-specific integrated circuits (ASICs), one or more digital signal processors (DSPs), or one or more field-programmable gate arrays (FPGAs), etc. As another example, when a module is implemented through processing element scheduler code, the processing element can be a general-purpose processor, such as a central processing unit (CPU) or other processor capable of calling program code. Furthermore, these modules can be integrated together as a system-on-a-chip (SOC).

[0122] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although the preferred embodiment has been disclosed above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A power supply module, characterized in that, It includes an asymmetric half-bridge flyback circuit and a control circuit. The asymmetric half-bridge flyback circuit is used to receive input voltage and provide output voltage. The asymmetric half-bridge flyback circuit includes a transformer, a resonant capacitor, a main power transistor, and an auxiliary power transistor. The control circuit is used to output control signals to control the main power transistor and the auxiliary power transistor. In response to the input voltage dropping below a first voltage value, the main power transistor remains off, and the auxiliary power transistor alternately turns off and on according to a first preset off duration and a second preset on duration. In response to the input voltage rising to a value greater than the second voltage value, the main power transistor and the auxiliary power transistor alternately turn on and off; Wherein, the second voltage value is greater than the first voltage value; The ratio of the second preset conduction duration to the resonant period of the asymmetric half-bridge flyback circuit is less than or equal to 0.

25.

2. The power module according to claim 1, characterized in that, The transformer includes a primary winding and a secondary winding. The source of the main power transistor is connected to the drain of the auxiliary power transistor and the first end of the primary winding. The source of the auxiliary power transistor is connected to a reference ground and one end of the resonant capacitor. The other end of the resonant capacitor is connected to the second end of the primary winding. When the auxiliary power transistor is turned on, the resonant capacitor discharges. When the auxiliary power transistor is turned off, the resonant capacitor stops discharging.

3. The power supply module according to claim 2, characterized in that, The power module includes an auxiliary winding circuit for supplying power to the control circuit. The auxiliary winding circuit includes an auxiliary winding that is coupled to the primary winding.

4. A control circuit for an asymmetric half-bridge flyback circuit, the asymmetric half-bridge flyback circuit comprising a transformer, a resonant capacitor, a main power transistor, and an auxiliary power transistor, characterized in that, The control circuit is used for: Obtain the comparison result between the input voltage value of the asymmetric half-bridge flyback circuit and the first voltage value or the second voltage value; In response to the input voltage value dropping below a first voltage value, the main power transistor is controlled to remain off, and the auxiliary power transistor is controlled to alternately turn off and on according to a first preset off duration and a second preset on duration; In response to the input voltage rising to a value greater than the second voltage value, the main power transistor and the auxiliary power transistor are controlled to alternately turn on and off; Wherein, the second voltage value is greater than the first voltage value; The ratio of the second preset conduction duration to the resonant period of the asymmetric half-bridge flyback circuit is less than or equal to 0.

25.

5. The control circuit according to claim 4, characterized in that, The control circuit is used to obtain the second preset conduction duration based on the resonant period of the asymmetric half-bridge flyback circuit, or the control circuit is used to obtain the second preset conduction duration based on the resonant capacitance value and resonant inductance value of the asymmetric half-bridge flyback circuit.

6. The control circuit according to claim 4, characterized in that, The control circuit is used for: In response to the input voltage dropping to less than the first voltage value and the input voltage rising to greater than the second voltage value, the difference in voltage of the resonant capacitor before the auxiliary power transistor is turned on in two consecutive first cycles is obtained, and the duration of the first cycle is the sum of the first preset off duration and the second preset on duration; In response to the fact that the voltage difference of the resonant capacitor does not increase before the auxiliary power transistor is turned on in two consecutive first cycles and the input voltage rises to a value greater than the second voltage value, the main power transistor is controlled to be turned on for a first duration in each second cycle; In response to an increase in the voltage difference of the resonant capacitor before the auxiliary power transistor is turned on in two consecutive first cycles and the input voltage rises to a value greater than the second voltage value, the main power transistor is controlled to be turned on for a second duration in each second cycle; wherein the second duration is longer than the first duration.

7. The control circuit according to claim 4, characterized in that, The control circuit is used for: In response to the input voltage dropping to less than the first voltage value and the input voltage rising to greater than the second voltage value, the voltage difference of the resonant capacitor before the auxiliary power transistor is turned on in two consecutive first cycles is obtained, and the duration of the first cycle is the sum of the first preset off duration and the second preset on duration; In response to the fact that the voltage difference of the resonant capacitor is less than a third voltage value before the auxiliary power transistor is turned on in two consecutive first cycles and the input voltage rises to be greater than the second voltage value, the main power transistor is controlled to be turned on for a first duration in each second cycle; In response to the voltage difference of the resonant capacitor being greater than a third voltage value before the auxiliary power transistor is turned on in two consecutive first cycles and the input voltage rising to be greater than the second voltage value, the main power transistor is controlled to be turned on for a second duration in each second cycle; wherein the third voltage value is greater than the second voltage value; and the second duration is greater than the first duration.

8. An electronic device comprising a power module as described in any one of claims 1-3, or a control circuit comprising an asymmetric half-bridge flyback circuit as described in any one of claims 4-7.

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