Primary-side conduction determination method, control method, control circuit, and flyback circuit

Abstract

The present invention discloses a primary conduction determination method, a control method, a control circuit and a flyback circuit, which detect the drain-source voltage of the synchronous rectifier tube of the flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube is integrated from zero in terms of volt-second. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration is ended to obtain a first integral. When the first integral is greater than a first integral threshold, it indicates that the primary side conducts during the volt-second integration, and the current in the transformer of the flyback circuit exceeds a first current threshold.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and specifically relates to a method for judging primary conduction, a control method, a control circuit and a flyback circuit. Background Art

[0002] In a flyback circuit, the freewheeling diode on the secondary side is replaced with a synchronous rectifier tube to improve the system conversion efficiency. However, the control circuit of the synchronous rectifier tube does not detect the primary circuit and cannot obtain the information of the conduction and cut-off of the primary main switch tube. It can only judge whether the primary side is conducting by the drain-source voltage value on the secondary synchronous rectifier tube, so as to control the conduction and cut-off of the secondary synchronous rectifier tube. Therefore, how to accurately control the conduction and cut-off of the secondary synchronous rectifier tube without the information of the conduction of the primary main switch tube is an important problem in the flyback circuit with synchronous rectification. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for judging primary conduction, a control method, a control circuit and a flyback circuit to solve the problem that the conduction and cut-off of the secondary synchronous rectifier tube cannot be accurately controlled in the prior art.

[0004] The technical solution of the present invention is to provide a method for judging primary conduction, which detects the drain-source voltage of the synchronous rectifier tube of the flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube is integrated from zero in volt-second. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration is ended to obtain a first integral;

[0005] When the first integral is greater than a first integral threshold, it indicates that the primary side is conducting and the transformer current exceeds a first current threshold during the volt-second integration.

[0006] The present invention also provides a synchronous rectification control method, which detects the drain-source voltage of the synchronous rectifier tube of the flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube is integrated from zero in volt-second. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration is ended to obtain a first integral;

[0007] That the first integral is greater than a first integral threshold is a necessary condition for the conduction of the synchronous rectifier tube.

[0008] Optionally, the drain-source voltage of the synchronous rectifier tube is sampled, and the drain-source voltage of the synchronous rectifier tube is filtered to output the average value of the drain-source voltage representing the synchronous rectifier tube.

[0009] Optionally, the necessary conduction condition of the synchronous rectifier tube is that the drain-source voltage of the synchronous rectifier tube is less than a first voltage threshold or / and the absolute value of the rate of change of the drain-source voltage of the synchronous rectifier tube with respect to time is greater than a first slope threshold.

[0010] The present invention provides a synchronous rectification control circuit that detects the drain-source voltage of the synchronous rectifier tube of a flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the synchronous rectification control circuit performs volt-second integration starting from zero on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration ends, and a first integration is obtained.

[0011] That the first integration is greater than a first integration threshold is a necessary condition for the synchronous rectifier tube to conduct.

[0012] Optionally, the synchronous rectification control circuit samples the drain-source voltage of the synchronous rectifier tube and filters the drain-source voltage of the synchronous rectifier tube to output an average value representing the drain-source voltage of the synchronous rectifier tube.

[0013] Optionally, it includes an integration circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the integration circuit performs volt-second integration starting from zero on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration ends, and a first integration is obtained. The first integration is compared with a first integration threshold to obtain a first voltage. When the first integration is greater than the first integration threshold, the first voltage is valid; otherwise, the first voltage is invalid. The integration circuit latches the first voltage to obtain a first latching result and clears the volt-second integration. The first latching result is the output voltage of the integration circuit.

[0014] Optionally, it further includes a comparison circuit and a logic circuit. The comparison circuit compares the drain-source voltage of the synchronous rectifier tube with a first voltage threshold. The logic circuit receives the output voltages of the comparison circuit and the integration circuit. When the output voltage of the integration circuit is valid and the drain-source voltage of the synchronous rectifier tube is less than the first voltage threshold, the output of the logic circuit changes from invalid to valid.

[0015] Optionally, it further includes a slope detection and comparison circuit, which compares the absolute value of the change rate of the drain-source voltage of the synchronous rectifier tube with respect to time and a first slope threshold. By comparing the absolute value of the change rate of the drain-source voltage of the synchronous rectifier tube with respect to time and the first slope threshold, a second voltage is obtained. If the absolute value of the change rate of the drain-source voltage of the synchronous rectifier tube with respect to time is greater than the first slope threshold, the second voltage is valid. The slope detection and comparison circuit latches the second voltage to obtain a second latching result, and the second latching result is the output voltage of the slope detection and comparison circuit.

[0016] The logic circuit receives the output voltage of the slope detection and comparison circuit. When the output voltage of the integration circuit is valid, and the drain-source voltage of the synchronous rectifier tube is less than the first voltage threshold, and the output voltage of the slope detection and comparison circuit is valid, the output of the logic circuit changes from invalid to valid.

[0017] Another technical solution of the present invention is to provide a flyback circuit.

[0018] Adopting the circuit structure and method of the present invention, compared with the prior art, it has the following advantages: accurately controlling the turn-on of the synchronous rectifier tube on the secondary side of the flyback circuit. Description of the Drawings

[0019] Figure 1 It is a flyback circuit with a synchronous rectifier tube M21, and the synchronous rectifier tube is connected to the positive end of the secondary output voltage;

[0020] Figure 2 It is a flyback circuit with a synchronous rectifier tube M21, and the synchronous rectifier tube is connected to the negative end of the secondary output voltage;

[0021] Figure 3 It is the waveform diagram of the drain-source current I DS of the synchronous rectifier tube, the drain-source voltage SW of the synchronous rectifier tube, and the drive signal GT of the synchronous rectifier tube;

[0022] Figure 4 It is the circuit block diagram of the synchronous rectification control circuit 100. Detailed Embodiments

[0023] The following describes the preferred embodiments of the present invention in detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any alternatives, modifications, equivalent methods, and solutions within the spirit and scope of the present invention.

[0024] In order to enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, and those skilled in the art can fully understand the present invention without these detailed descriptions.

[0025] The present invention will be described more specifically by way of example with reference to the accompanying drawings in the following paragraphs. It should be noted that the accompanying drawings are all in a relatively simplified form and use non-precise scales, only for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0026] The present invention provides a method for judging the primary conduction of a flyback circuit. The flyback circuit includes a transformer TR11, a main switch tube M11, and a synchronous rectifier tube M21. Detect the drain-source voltage of the synchronous rectifier tube M21 of the flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube M21 is greater than the average value of the drain-source voltage of the synchronous rectifier tube M21, perform volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube starting from zero. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, end the integration to obtain a first integration; when the first integration is greater than a first integration threshold, it indicates that the primary side is conducting during the volt-second integration and the transformer current exceeds a first current threshold.

[0027] The method for judging the primary conduction of the flyback circuit of the present invention is applicable to the high-voltage end and the low-voltage end where the synchronous rectifier tube is connected to the output. Please refer to Figure 1 and Figure 2 shown, which are respectively flyback circuits with a synchronous rectifier tube M21, where Figure 1 the synchronous rectifier tube is connected to the positive end of the secondary output voltage, Figure 2 and Figure 1 the synchronous rectifier tube is connected to the negative end of the secondary output voltage. It should be noted that in Figure 2 and Figure 3 the ground of the primary side, that is, the source of M11 and the source of the synchronous rectifier tube M21, marked as ground GND, are different reference grounds and not at the same potential. Please refer to DS shown, which is a waveform diagram of the drain-source current I

[0028] The present invention also provides a synchronous rectification control method. Detect the drain-source voltage of the synchronous rectifier tube of the flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, perform volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube starting from zero. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, end the integration to obtain a first integration; that the first integration is greater than a first integration threshold is a necessary condition for the synchronous rectifier tube to conduct. Specifically, in one embodiment, please refer to Figure 3As shown, at time t0, the volt-second integration of the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube starts from zero. At time t1, the integration ends. At this time, the first integration is greater than the first integration threshold, and this comparison result is latched to obtain the first latching result, and the first latching result is valid. After latching, the first integration can be cleared. Only when the first latching result is valid and other conduction conditions of the synchronous rectifier tube are met can the synchronous rectifier tube conduct. The first latching result can be cleared when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube next time, that is, cleared at time t4, and the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube is integrated again. At time t5, the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, and the integration ends. At this time, the first integration is less than the first integration threshold, and even if the conduction conditions of the synchronous rectifier tube are met later, the synchronous rectifier tube will not conduct. In another embodiment, continue to refer to Figure 3 As shown, at time t1, the first integration is greater than the first integration threshold, and the first integration is maintained without clearing the first integration. When other conduction conditions of the synchronous rectifier tube are met, the synchronous rectifier tube can conduct; the first integration can be cleared when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube next time, that is, cleared at time t4, and the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube is integrated again.

[0029] It should be noted that since the average value of the drain-source voltage of the synchronous rectifier tube is equal to the output voltage, so in Figure 3 , the output voltage VO is used to replace the average value of the drain-source voltage of the synchronous rectifier tube. Among them, the shaded parts S1 and S2 are the values of the volt-second integration twice, and each integration starts from zero for volt-second integration.

[0030] In one embodiment, by sampling the drain-source voltage of the synchronous rectifier tube and filtering the drain-source voltage of the synchronous rectifier tube, the average value of the drain-source voltage of the synchronous rectifier tube is output. A resistor-capacitor RC can be used to filter the drain-source voltage of the synchronous rectifier tube.

[0031] In one embodiment, the necessary conduction condition of the synchronous rectifier tube is that the drain-source voltage of the synchronous rectifier tube is less than the first voltage threshold. Please refer to Figure 3As shown, at time t1, the first integral is greater than the first integral threshold. At time t2, the drain-source voltage of the synchronous rectifier is less than the first voltage threshold by 300 mV. Due to the delay in the turn-on of the synchronous rectification, at time t3, the drive signal GT of the synchronous rectifier changes from low to high. In another embodiment, if the absolute value of the rate of change of the drain-source voltage of the synchronous rectifier with respect to time is greater than the first slope threshold, then the comparison result is latched to obtain a second latched result, and the second latch is valid. When the second latched result is valid and the drain-source voltage of the synchronous rectifier is less than the first voltage threshold, it is a necessary conduction condition for the synchronous rectifier.

[0032] The present invention provides a synchronous rectification control circuit that detects the drain-source voltage of the synchronous rectifier of a flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier is greater than the average value of the drain-source voltage of the synchronous rectifier, the synchronous rectification control circuit performs a volt-second integration starting from zero on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier and the average value of the drain-source voltage of the synchronous rectifier. When the instantaneous value of the drain-source voltage of the synchronous rectifier is less than the average value of the drain-source voltage of the synchronous rectifier, the integration ends to obtain a first integral; the first integral being greater than the first integral threshold is a necessary condition for the conduction of the synchronous rectifier.

[0033] Please refer to Figure 1 and Figure 2 shown, which are respectively a flyback circuit with a synchronous rectifier M21. The synchronous rectification control circuit 100 is connected to the gate, source, and drain of the synchronous rectifier M21, and the source of the synchronous rectifier M21 is the reference ground of the synchronous rectification control circuit 100. Among them Figure 1 the synchronous rectifier M21 is connected to the positive terminal of the secondary output voltage, Figure 2 the synchronous rectifier M21 is connected to the negative terminal of the secondary output voltage. It should be noted that in Figure 1 and Figure 2 the ground of the primary side, that is, the source of M11 and the reference ground of the synchronous rectification control circuit 100, are not at the same potential.

[0034] In one embodiment, the synchronous rectification control circuit samples the drain-source voltage of the synchronous rectifier and filters the drain-source voltage of the synchronous rectifier to output an average value representing the drain-source voltage of the synchronous rectifier. A resistor-capacitor RC can be used to filter the drain-source voltage of the synchronous rectifier.

[0035] Please refer to Figure 4As shown, it is a block diagram of the implementation of the synchronous rectification control circuit 100, including an integration circuit 110. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the integration circuit performs volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube starting from zero. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration ends, obtaining a first integration. The first integration is compared with a first integration threshold to obtain a first voltage. When the first integration is greater than the first integration threshold, the first voltage is valid; otherwise, the first voltage is invalid. The integration circuit latches the first voltage to obtain a first latching result, clears the volt-second integration, and the first latching result is the output voltage of the integration circuit. The first latching result can be cleared when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube next time.

[0036] Please continue to refer to Figure 4 As shown, it further includes a comparison circuit 120 and a logic circuit 140. The comparison circuit compares the drain-source voltage SW of the synchronous rectifier tube with a first voltage threshold. The logic circuit 140 receives the output voltages of the comparison circuit and the integration circuit 110. When the output voltage of the integration circuit is valid and the drain-source voltage of the synchronous rectifier tube is less than the first voltage threshold, the output of the logic circuit changes from invalid to valid. It further includes a drive circuit 150. The drive circuit receives the output voltage of the logic circuit 140. When the output of the logic circuit is valid, the drive circuit 150 drives the synchronous rectifier tube to conduct; when the output of the logic circuit is invalid, the drive circuit 150 drives the synchronous rectifier tube to turn off.

[0037] In one embodiment, please continue to refer to Figure 4 As shown, it further includes a slope detection and comparison circuit 140. The slope detection and comparison circuit 140 compares the absolute value of the rate of change of the drain-source voltage of the synchronous rectifier tube with respect to time and a first slope threshold. The absolute value of the rate of change of the drain-source voltage of the synchronous rectifier tube with respect to time is compared with the first slope threshold to obtain a second voltage. When the absolute value of the rate of change of the drain-source voltage of the synchronous rectifier tube with respect to time is greater than the first slope threshold, the second voltage is valid. The slope detection and comparison circuit latches the second voltage to obtain a second latching result, and the second latching result is the output voltage of the slope detection and comparison circuit.

[0038] The logic circuit 140 receives the output voltage of the slope detection and comparison circuit 130. When the output voltage of the integration circuit 110 is valid, and the drain-source voltage of the synchronous rectifier is less than the first voltage threshold, and the output voltage of the slope detection and comparison circuit 130 is valid, the output of the logic circuit 140 changes from invalid to valid, and the drive circuit 150 drives the synchronous rectifier to conduct.

[0039] Another technical solution of the present invention is to provide a flyback circuit including the above-mentioned synchronous rectification control circuit.

[0040] Although the embodiments are separately described and elaborated above, for some common technologies, in the view of those of ordinary skill in the art, substitutions and integrations can be made between the embodiments. For the content not clearly recorded in one embodiment, reference can be made to another recorded embodiment.

[0041] The above-described embodiments do not limit the protection scope of the technical solution. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the above embodiments shall be included in the protection scope of the technical solution.

Claims

1. A primary-side conduction judgment method, which detects the drain-source voltage of the synchronous rectifier tube in the flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube is integrated from zero in terms of volt-second. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration ends, and a first integration is obtained. When the first integration is greater than the first integration threshold, it indicates that the primary side is conducting during the volt-second integration and the transformer current exceeds the first current threshold.

2. A synchronous rectification control method, which detects the drain-source voltage of the synchronous rectifier tube in the flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube is integrated from zero in terms of volt-second. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration ends, and a first integration is obtained. That the first integration is greater than the first integration threshold is a necessary condition for the synchronous rectifier tube to conduct.

3. The synchronous rectification control method according to claim 2, characterized in that: By sampling the drain-source voltage of the synchronous rectifier tube and filtering the drain-source voltage of the synchronous rectifier tube, the average value of the drain-source voltage of the synchronous rectifier tube is output.

4. The synchronous rectification control method according to claim 3, characterized in that: The necessary conduction condition of the synchronous rectifier tube is that the drain-source voltage of the synchronous rectifier tube is less than the first voltage threshold or / and the absolute value of the rate of change of the drain-source voltage of the synchronous rectifier tube with respect to time is greater than the first slope threshold.

5. A synchronous rectification control circuit, which detects the drain-source voltage of the synchronous rectifier tube in the flyback circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the synchronous rectification control circuit integrates the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero in terms of volt-second. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration ends, and a first integration is obtained. That the first integration is greater than the first integration threshold is a necessary condition for the synchronous rectifier tube to conduct.

6. The synchronous rectification control circuit according to claim 5, characterized in that: The synchronous rectification control circuit samples the drain-source voltage of the synchronous rectifier tube and filters the drain-source voltage of the synchronous rectifier tube, and outputs the average value of the drain-source voltage of the synchronous rectifier tube.

7. The synchronous rectification control circuit according to claim 6, characterized in that: It includes an integrating circuit. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube, the integrating circuit performs volt-second integration starting from zero on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube. When the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, the integration ends, and a first integration is obtained. The first integration is compared with a first integration threshold to obtain a first voltage. When the first integration is greater than the first integration threshold, the first voltage is valid; otherwise, the first voltage is invalid. The integrating circuit latches the first voltage to obtain a first latching result and clears the volt-second integration. The first latching result is the output voltage of the integrating circuit.

8. The synchronous rectification control circuit according to claim 7, characterized in that: it further includes a comparison circuit and a logic circuit. The comparison circuit compares the drain-source voltage of the synchronous rectifier tube with a first voltage threshold. The logic circuit receives the output voltages of the comparison circuit and the integrating circuit. When the output voltage of the integrating circuit is valid and the drain-source voltage of the synchronous rectifier tube is less than the first voltage threshold, the output of the logic circuit changes from invalid to valid.

9. The synchronous rectification control circuit according to claim 8, characterized in that: it further includes a slope detection and comparison circuit. The slope detection and comparison circuit compares the absolute value of the rate of change of the drain-source voltage of the synchronous rectifier tube with respect to time with a first slope threshold. The absolute value of the rate of change of the drain-source voltage of the synchronous rectifier tube with respect to time is compared with the first slope threshold to obtain a second voltage. When the absolute value of the rate of change of the drain-source voltage of the synchronous rectifier tube with respect to time is greater than the first slope threshold, the second voltage is valid. The slope detection and comparison circuit latches the second voltage to obtain a second latching result. The second latching result is the output voltage of the slope detection and comparison circuit; the logic circuit receives the output voltage of the slope detection and comparison circuit. When the output voltage of the integrating circuit is valid, the drain-source voltage of the synchronous rectifier tube is less than the first voltage threshold, and the output voltage of the slope detection and comparison circuit is valid, the output of the logic circuit changes from invalid to valid.

10. A flyback circuit, characterized in that: it includes the synchronous rectification control circuit according to any one of claims 5 to 9, or adopts the synchronous rectification control method according to any one of claims 2 to 4.

Images