Self-driven synchronous rectification circuit, switching power supply and circuit board

Abstract

The application discloses a self-driven synchronous rectification circuit, a switching power supply and a circuit board, and relates to the technical field of switching power supplies. The self-driven synchronous rectification circuit comprises a primary side resonance unit, a transformer, a first MOS tube, a second MOS tube, an output electrolytic capacitor, a first spike absorption unit, a second spike absorption unit, a first potential maintaining unit and a second potential maintaining unit; the primary side resonance unit is electrically connected with the first end and the second end of the primary side of the transformer, and is used for controlling the first MOS tube and the second MOS tube to alternately conduct; the first end of the first MOS tube is electrically connected with the first end of the secondary side of the transformer and the first end of the first spike absorption unit, the control end of the first MOS tube is electrically connected with the first end of the first potential maintaining unit, and the second end of the first MOS tube is electrically connected with the second end, the third end of the first potential maintaining unit, the first end of the output electrolytic capacitor and the first ground end. The application can avoid the damage of the MOS tube caused by the spike voltage, and can eliminate the problem of the MOS tube driving oscillation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power supply, in particular to a self-driven synchronous rectification circuit, a switching power supply and a circuit board. BACKGROUND

[0002] MOS transistors are widely used as switches in switching power supply circuits, but due to their small size, MOS transistors do not have protection functions. When feedback charging or sharp pulses exist, the main circuit will have large current and voltage. If protection is not timely or there is no voltage and current discharge circuit, the bus voltage will exceed the withstand voltage and current of the MOS transistor, which will burn the MOS transistor, which is not conducive to the continuity and safety of the circuit.

[0003] Figure 1 is a structural diagram of a prior art self-driven synchronous rectification circuit, referring to Figure 1 The primary side resonant unit 110 can control the first MOS transistor Q1 and the second MOS transistor Q2 in the secondary side circuit to alternately conduct, thereby realizing power conversion from input to output. When the primary side resonant unit 110 stops working, the secondary side circuit will not immediately disappear due to the output electrolytic capacitor E1, and the secondary side will generate self-oscillation. The process is as follows: assuming that at the moment before the primary side stops working, the first end A of the secondary side of the transformer is at a high potential, the second MOS transistor Q2 is turned on, and the first MOS transistor Q1 is turned off, then at the moment when the primary side stops working, the current flows from the positive electrode of the output electrolytic capacitor E1 to the third end B of the secondary side of the transformer, flows through the second end C of the secondary side of the transformer to the second MOS transistor Q2, and returns to the negative electrode of the output electrolytic capacitor E1. When the secondary side winding voltage reverses, the first MOS transistor Q1 is turned on, the second MOS transistor Q2 is turned off, the current flows from the positive electrode of the output electrolytic capacitor E1 to the third end B of the secondary side of the transformer, flows through the first end A of the secondary side of the transformer to the first MOS transistor Q1, and returns to the negative electrode of the output electrolytic capacitor E1. This oscillation process continues until the voltage of the output electrolytic capacitor E1 is insufficient to maintain the switching of the first MOS transistor and the second MOS transistor. During the oscillation process, the first MOS transistor Q1 and the second MOS transistor Q2 will generate a high spike during each turn-off, which will exceed the rated withstand voltage of the MOS transistor and cause damage to the MOS transistor. Figure 2 is a schematic diagram of the spike pulse voltage generated when the MOS transistor is turned off, referring to Figure 2 , pulse 1 represents the voltage difference between the source and drain of the MOS transistor, pulse 2 represents the voltage difference between the gate and drain of the MOS transistor, pulse 3 is a partial enlarged view of pulse 1, and pulse 4 is a partial enlarged view of pulse 2, as can be seen from Figure 2 , the MOS transistor generates a high spike during each turn-off, which damages the MOS transistor. SUMMARY

[0004] The application provides a self-driven synchronous rectification circuit, a switching power supply and a circuit board, which can avoid damage of a MOS transistor by a sharp voltage and eliminate oscillation of the MOS transistor.

[0005] According to an aspect of the application, a self-driven synchronous rectification circuit is provided, which comprises a primary resonant unit, a transformer, a first MOS transistor, a second MOS transistor, an output electrolytic capacitor, a first sharp peak absorption unit, a second sharp peak absorption unit, a first potential maintaining unit and a second potential maintaining unit.

[0006] The primary resonant unit is electrically connected with a first end and a second end of a primary side of the transformer, and is configured to control the first MOS transistor and the second MOS transistor to be alternately turned on.

[0007] A first end of the first MOS transistor is electrically connected with a first end of a secondary side of the transformer and a first end of the first sharp peak absorption unit, a control end of the first MOS transistor is electrically connected with a first end of the first potential maintaining unit, and a second end of the first MOS transistor is electrically connected with a second end, a third end of the first potential maintaining unit and a first end and a first ground end of the output electrolytic capacitor.

[0008] A first end of the second MOS transistor is electrically connected with a second end of the secondary side of the transformer and a first end of the second sharp peak absorption unit, a control end of the second MOS transistor is electrically connected with a first end of the second potential maintaining unit, and a second end of the second MOS transistor is electrically connected with a second end, a third end of the second potential maintaining unit and a first end of the output electrolytic capacitor.

[0009] A second end of the first sharp peak absorption unit is electrically connected with a third end of the secondary side of the transformer, a second end of the second sharp peak absorption unit and a second end of the output electrolytic capacitor.

[0010] A fourth end of the first potential maintaining unit is electrically connected with the second end of the secondary side of the transformer, and the first potential maintaining unit is configured to maintain a low level of the control end of the first MOS transistor when a potential of the second end of the secondary side of the transformer is low; and a fourth end of the second potential maintaining unit is electrically connected with the first end of the secondary side of the transformer, and the first potential maintaining unit is configured to maintain a low level of the control end of the first MOS transistor when a potential of the first end of the secondary side of the transformer is low.

[0011] According to another aspect of the application, a switching power supply is provided, which comprises the self-driven synchronous rectification circuit provided in any of the embodiments of the application.

[0012] According to another aspect of the present application, there is provided a circuit board comprising the self-driven synchronous rectification circuit according to any of the embodiments of the present application.

[0013] The embodiment provides a self-driven synchronous rectification circuit, which comprises a primary side resonance unit, a transformer, a first MOS tube, a second MOS tube, an output electrolytic capacitor, a first spike absorption unit electrically connected with the first end and the second end of the first MOS tube and the first end and the third end of the transformer, and a second spike absorption unit electrically connected with the first end and the second end of the second MOS tube and the second end and the third end of the transformer. The first spike absorption unit can absorb the spike voltage between the first end and the second end of the first MOS tube when the first MOS tube is turned off. The second spike absorption unit can absorb the spike voltage between the first end and the second end of the second MOS tube when the second MOS tube is turned off. The self-driven synchronous rectification circuit provided by the embodiment further comprises a first potential maintaining unit and a second potential maintaining unit. The first potential maintaining unit can control the control end of the first MOS tube to be low when the third end of the first transformer is low, so as to eliminate the problem of driving oscillation of the first MOS tube. The second potential maintaining unit can control the control end of the second MOS tube to be low when the first end of the first transformer is low, so as to eliminate the problem of driving oscillation of the second MOS tube. In summary, the self-driven synchronous rectification circuit provided by the embodiment can avoid damage of the MOS tube caused by the spike voltage, and can eliminate the problem of driving oscillation of the MOS tube.

[0014] It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the present application or to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0016] Figure 1 is a structural schematic diagram of a self-driven synchronous rectification circuit in the prior art;

[0017] Figure 2 is a schematic diagram of a spike pulse voltage generated when the MOS tube is turned off;

[0018] Figure 3 is a structural schematic diagram of a self-driven synchronous rectification circuit according to an embodiment of the present application;

[0019] Figure 4is a structural schematic diagram of still another self-driven synchronous rectification circuit according to an embodiment of the present application;

[0020] Figure 5 is a structural schematic diagram of still another self-driven synchronous rectification circuit according to an embodiment of the present application;

[0021] Figure 6 is a structural schematic diagram of still another self-driven synchronous rectification circuit according to an embodiment of the present application;

[0022] Figure 7 is a structural schematic diagram of still another self-driven synchronous rectification circuit according to an embodiment of the present application;

[0023] Figure 8 is a structural schematic diagram of still another self-driven synchronous rectification circuit according to an embodiment of the present application;

[0024] Figure 9 is a structural schematic diagram of still another self-driven synchronous rectification circuit according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the personnel in the art better understand the present application scheme, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0026] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0027] Figure 3 is a structural schematic diagram of a self-driven synchronous rectification circuit according to an embodiment of the present application, referring to Figure 3The self-driven synchronous rectification circuit comprises a primary side resonance unit 110, a transformer T1, a first MOS tube Q1, a second MOS tube Q2, an output electrolytic capacitor E1, a first spike absorption unit 120, a second spike absorption unit 130, a first potential maintaining unit 140, and a second potential maintaining unit 150.

[0028] The primary side resonance unit 110 is electrically connected with the first end 1 and the second end 2 of the primary side of the transformer, and is used for controlling the first MOS tube Q1 and the second MOS tube Q2 to be alternately turned on. The first end of the first MOS tube Q1 is electrically connected with the first end A of the secondary side of the transformer and the first end of the first spike absorption unit 120, the control end of the first MOS tube Q1 is electrically connected with the first end of the first potential maintaining unit 140, the second end of the first MOS tube Q1 is electrically connected with the second end, the third end of the first potential maintaining unit 140, the first end of the output electrolytic capacitor E1, and the first ground end GND; the first end of the second MOS tube Q2 is electrically connected with the second end C of the secondary side of the transformer and the first end of the second spike absorption unit 130, the control end of the second MOS tube Q2 is electrically connected with the first end of the second potential maintaining unit 150, the second end of the second MOS tube Q2 is electrically connected with the second end, the third end of the second potential maintaining unit 150, and the first end of the output electrolytic capacitor E1; the second end of the first spike absorption unit 120 is electrically connected with the third end B of the secondary side of the transformer, the second end of the second spike absorption unit 130, and the second end of the output electrolytic capacitor E1; the fourth end of the first potential maintaining unit 140 is electrically connected with the second end C of the secondary side of the transformer, and the first potential maintaining unit 140 is used for maintaining the potential of the control end of the first MOS tube Q1 as low level when the potential of the second end C of the secondary side of the transformer is low level; the fourth end of the second potential maintaining unit 150 is electrically connected with the first end A of the secondary side of the transformer, and the second potential maintaining unit 150 is used for maintaining the potential of the control end of the first MOS tube Q1 as low level when the potential of the first end A of the secondary side of the transformer is low level.

[0029] Specifically, the control end of the first MOS tube Q1 is a gate, the first end of the first MOS tube Q1 is a source, and the second end of the first MOS tube Q1 is a drain.

[0030] The primary-side resonant unit 120 is used to control the alternating conduction of the first MOSFET Q1 and the second MOSFET Q2. Specifically, the primary-side resonant unit 120 controls the potential of the first terminal A of the transformer secondary side to be high and the potential of the second terminal C to be low, thereby controlling the second MOSFET Q2 to conduct and the first MOSFET Q1 to turn off. Alternatively, the primary-side resonant unit 120 controls the potential of the first terminal A of the transformer secondary side to be low and the potential of the second terminal C to be high, thereby controlling the first MOSFET Q1 to conduct and the second MOSFET Q2 to turn off. Within one cycle, the conduction percentage of the first MOSFET Q1 and the conduction percentage of the second MOSFET Q2 can each be 50%.

[0031] The specific working principle of the self-driven synchronous rectifier circuit provided in this embodiment is as follows: When the primary resonant unit 110 stops working, the potential of the first terminal A of the transformer secondary side is low, the potential of the second terminal C is high, the first MOSFET Q1 is turned on, and the second MOSFET Q2 is turned off. At this time, since the current between the third terminal B and the second terminal C of the transformer secondary side cannot change abruptly, a voltage spike will be generated between the first and second terminals of the second MOSFET Q2 (the waveform of this voltage spike is as follows). Figure 2 (The spike waveforms of pulses 1 and 3 in the image). In this embodiment, a second spike absorption unit 130 is provided, which can absorb the spike voltage between the first and second terminals of the second MOSFET Q2, thereby reducing the voltage between the first and second terminals of the second MOSFET Q2 below the rated specification and solving the problem of the second MOSFET Q2 being damaged by spike voltage. At the same time, when the potential of the first terminal A of the transformer secondary side is low, the second potential maintenance unit 150 controls the potential of the control terminal of the second MOSFET Q2 to maintain a low level. That is, the second potential maintenance unit 150 controls the control terminal of the second MOSFET Q2 to be connected to the first ground terminal GND, which can eliminate the voltage oscillation problem between the control terminal and the second terminal of the second MOSFET Q2 (the waveform of this voltage oscillation is shown in the image). Figure 2the first MOS tube Q1 and the second MOS tube Q2 from being damaged by the sharp voltage, and can eliminate the problem of driving oscillation of the first MOS tube Q1 and the second MOS tube Q2. The first ground end GND can be a power supply ground

[0032] The self-driven synchronous rectification circuit provided in the embodiment includes a primary side resonant unit, a transformer, a first MOS tube, a second MOS tube, an output electrolytic capacitor, a first sharp peak absorption unit electrically connected with the first end and the second end of the first MOS tube and the first end and the third end of the transformer, and a second sharp peak absorption unit electrically connected with the first end and the second end of the second MOS tube and the second end and the third end of the transformer. The first sharp peak absorption unit can absorb the sharp voltage between the first end and the second end of the first MOS tube when the first MOS tube is turned off. The second sharp peak absorption unit can absorb the sharp voltage between the first end and the second end of the second MOS tube when the second MOS tube is turned off. The self-driven synchronous rectification circuit provided in the embodiment further includes a first potential maintaining unit and a second potential maintaining unit. The first potential maintaining unit can control the control end of the first MOS tube to be at a low level when the third end of the first transformer is at a low level, thereby eliminating the problem of driving oscillation of the first MOS tube. The second potential maintaining unit can control the control end of the second MOS tube to be at a low level when the first end of the first transformer is at a low level, thereby eliminating the problem of driving oscillation of the second MOS tube. In summary, the self-driven synchronous rectification circuit provided in the embodiment can avoid the MOS tube from being damaged by the sharp voltage, and can eliminate the problem of driving oscillation of the MOS tube.

[0033] Optionally, Figure 4 is a structural schematic diagram of still another self-driven synchronous rectification circuit provided according to the embodiment of the present application, which is described with reference toFigure 4 The first peak absorption unit 120 comprises a first diode D1, a first capacitor C1 and a first resistor R1; the second peak absorption unit 130 comprises a second diode D2, a second capacitor C2 and a second resistor R2; the anode of the first diode D1 is electrically connected to the first end of the first MOS Q1, the cathode of the first diode D1 is electrically connected to the first end of the first capacitor C1 and the first end of the first resistor R1; the second end of the first capacitor C1 is electrically connected to the third end B of the secondary side of the transformer, the second end of the first resistor R1 and the second end of the output electrolytic capacitor E1; the anode of the second diode D2 is electrically connected to the first end of the second MOS Q2, the cathode of the second diode D2 is electrically connected to the first end of the second capacitor C2 and the first end of the second resistor R2; the second end of the second capacitor C2 is electrically connected to the third end B of the secondary side of the transformer and the second end of the second resistor R2.

[0034] Specifically, when the first end and the second end of the first MOS Q1 exist a peak voltage, the first capacitor C1 will absorb and store the peak voltage of the first end and the second end of the first MOS Q1, the first resistor R1 will consume the voltage stored by the first capacitor C1, and finally eliminate the peak voltage existing in the first end and the second end of the first MOS Q1, the first diode D1 is used to prevent the current from flowing through the second end of the first resistor R1 to the first MOS Q1 and damage the first MOS Q1. Similarly, when the first end and the second end of the second MOS Q2 exist a peak voltage, the second capacitor C2 will absorb and store the peak voltage of the first end and the second end of the second MOS Q2, the second resistor R2 will consume the voltage stored by the second capacitor C2, and finally eliminate the peak voltage existing in the first end and the second end of the second MOS Q2, the second diode D2 is used to prevent the current from flowing through the second end of the second resistor R2 to the second MOS Q2 and damage the second MOS Q2.

[0035] Optionally, Figure 5 is another structure diagram of a self-driven synchronous rectification circuit according to an embodiment of the present application, referring to Figure 5The first potential maintaining unit 140 comprises a third capacitor C3, a third resistor R3, a third diode D3, a first transistor T1 and a fourth resistor R4; the second potential maintaining unit 150 comprises a fourth capacitor C4, a fifth resistor R5, a fourth diode D4, a second transistor T2 and a sixth resistor R6; the first end of the third capacitor C3 is electrically connected with the second end C of the transformer secondary side, the second end of the third capacitor C3 is electrically connected with the control end of the first MOS Q1, the first end of the first transistor T1, the cathode of the third diode D3 and the first end of the third resistor R3; the second end of the third resistor R3 is electrically connected with the anode of the third diode D3 and the control end of the first transistor T1; the second end of the first transistor T1 is electrically connected with the first end of the fourth resistor R4; the second end of the fourth resistor R4 is electrically connected with the second end of the first MOS Q1 and the first end of the output electrolytic capacitor E1; the first end of the fourth capacitor C4 is electrically connected with the first end A of the transformer secondary side, the second end of the fourth capacitor C4 is electrically connected with the control end of the second MOS Q2, the first end of the second transistor T2, the cathode of the fourth diode D4 and the first end of the fifth resistor R5; the second end of the fifth resistor R5 is electrically connected with the anode of the fourth diode D4 and the control end of the second transistor T2; the second end of the second transistor T2 is electrically connected with the first end of the sixth resistor R6; the second end of the sixth resistor R6 is electrically connected with the second end of the second MOS Q2 and the first end of the output electrolytic capacitor E1.

[0036] Specifically, the third capacitor C3 and the fourth capacitor C4 have the function of passing alternating current and blocking direct current.

[0037] When the primary side resonant unit 110 stops working and the potential of the second end C of the secondary side of the transformer is low, because the voltage across the third capacitor C3 cannot change abruptly, the voltage at the second end of the third capacitor C3 is low, and the control end of the first transistor T1 is low, the first transistor T1 is turned on, so that the control end of the first MOS Q1 is grounded. Even if the control end of the first MOS Q1 maintains low, the problem of oscillation of the driving voltage between the control end and the second end of the first MOS Q1 is eliminated. The third resistor R3 and the fourth resistor R4 are used for current limiting, and the third diode D3 is used for preventing current from flowing backward. The third capacitor C3 is used for passing alternating current and blocking direct current. Similarly, when the primary side resonant unit 110 stops working and the potential of the first end A of the secondary side of the transformer is low, because the voltage across the fourth capacitor C4 cannot change abruptly, the voltage at the second end of the fourth capacitor C4 is low, and the control end of the second transistor T2 is low, the second transistor T2 is turned on, so that the control end of the second MOS Q2 is grounded. Even if the control end of the second MOS Q2 maintains low, the problem of oscillation of the driving voltage between the control end and the second end of the second MOS Q2 is eliminated. The fifth resistor R5 and the sixth resistor R6 are used for current limiting, and the fourth diode D4 is used for preventing current from flowing backward. The fourth capacitor C4 is used for passing alternating current and blocking direct current.

[0038] Optionally, Figure 6 is another structure diagram of a self-driven synchronous rectification circuit according to an embodiment of the present application, referring to Figure 6 The self-driven synchronous rectification circuit provided in the embodiment further includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a first voltage stabilizing tube Z1, a second voltage stabilizing tube Z2, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a third voltage stabilizing tube Z3, and a fourth voltage stabilizing tube Z4.

[0039] The first end of the seventh resistor R7 is electrically connected with the second end C of the secondary side of the transformer, and the second end of the seventh resistor R7 is electrically connected with the first end of the third capacitor C3; the first end of the eighth resistor R8 is electrically connected with the second end of the third capacitor C3, and the second end of the eighth resistor R8 is electrically connected with the control end of the first MOS Q1 and the first end of the ninth resistor R9; the second end of the ninth resistor R9 is electrically connected with the first end of the output electrolytic capacitor E1; the cathode of the first Zener Z1 is electrically connected with the second end of the third capacitor C3, and the anode of the first Zener Z1 is electrically connected with the anode of the second Zener Z2; the cathode of the second Zener Z2 is electrically connected with the first end of the output electrolytic capacitor E1; the first end of the tenth resistor R10 is electrically connected with the first end A of the secondary side of the transformer, and the second end of the tenth resistor R10 is electrically connected with the first end of the fourth capacitor C4; the first end of the eleventh resistor R11 is electrically connected with the second end of the fourth capacitor C4, and the second end of the eleventh resistor R11 is electrically connected with the control end of the second MOS Q2 and the first end of the twelfth resistor R12; the second end of the twelfth resistor R12 is electrically connected with the first end of the output electrolytic capacitor E1; the cathode of the third Zener Z3 is electrically connected with the second end of the fourth capacitor C4, and the anode of the third Zener Z3 is electrically connected with the anode of the fourth Zener Z4; the cathode of the fourth Zener Z4 is electrically connected with the first end of the output electrolytic capacitor E1.

[0040] Specifically, the seventh resistor R7 and the tenth resistor R10 are used for current limiting. The eighth resistor R8 and the ninth resistor R9 are used for releasing the voltage of the control end of the first MOS Q1 when the second end C of the secondary side of the transformer is low, so that the first MOS Q1 is quickly turned off. The eleventh resistor R11 and the twelfth resistor R12 are used for releasing the voltage of the control end of the second MOS Q2 when the first end A of the secondary side of the transformer is low, so that the second MOS Q2 is quickly turned off.

[0041] The first Zener Z1 and the second Zener Z2 are used for stabilizing the voltage between the first end and the second end of the first MOS Q1 within a certain range. The third Zener Z3 and the fourth Zener Z4 are used for stabilizing the voltage between the first end and the second end of the second MOS Q2 within a certain range

[0042] Optionally, Figure 7 is another structure diagram of a self-driven synchronous rectification circuit according to an embodiment of the application, which is described in detail with reference to Figure 7The primary side resonant unit comprises a control unit 111, a third MOS tube Q3 and a fourth MOS tube Q4. A first output end H0 of the control unit 111 is electrically connected with a control end of the third MOS tube Q3, a second output end L0 of the control unit 111 is electrically connected with a control end of the fourth MOS tube Q4, a high voltage pin end HV of the control unit 111 is electrically connected with a first end of the third MOS tube Q3, and the control unit 111 is used for controlling the third MOS tube Q3 and the fourth MOS tube Q4 to be alternately turned on. A second end of the third MOS tube Q3 is electrically connected with a first end 1 of the primary side of the transformer and a first end of the fourth MOS tube Q4. A second end of the fourth MOS tube Q4 is electrically connected with a second end 2 of the primary side of the transformer and a second ground end SGND.

[0043] Specifically, when the control unit 111 controls the third MOS tube Q3 to be turned on and the fourth MOS tube Q4 to be turned off, the first MOS tube Q1 is turned off and the second MOS tube Q2 is turned on. When the control unit 111 controls the third MOS tube Q3 to be turned off and the fourth MOS tube Q4 to be turned on, the first MOS tube Q1 is turned on and the second MOS tube Q2 is turned off. The second ground end SGND of the control unit 111 is grounded, and the second end of the third MOS tube Q3 is also electrically connected with a common connection end VS of the control unit 111. The second ground end SGND can be a signal ground.

[0044] Optionally, Figure 8 is another structure diagram of a self-driven synchronous rectification circuit according to an embodiment of the present application, referring to Figure 8, the primary side resonant unit further comprises a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a fifth diode D5, a fifth capacitor C5, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a sixth diode D6 and a sixth capacitor C6; a first end of the thirteenth resistor R13 is electrically connected with a first output end H0 of the control unit 111 and a cathode of the fifth diode D5, a second end of the thirteenth resistor R13 is electrically connected with a first end of the fourteenth resistor R14, a first end of the fifteenth resistor R15 and a control end of the third MOS tube Q3; a second end of the fourteenth resistor R14 is electrically connected with an anode of the fifth diode D5; a second end of the fifteenth resistor R15 is electrically connected with a first end 1 of the primary side of the transformer; a first end of the fifth capacitor C5 is electrically connected with a first end of the third MOS tube Q3, and a second end of the fifth capacitor C5 is electrically connected with a second end of the third MOS tube Q3; a first end of the sixteenth resistor R16 is electrically connected with a second output end L0 of the control unit 111 and a cathode of the sixth diode D6, a second end of the sixteenth resistor R16 is electrically connected with a first end of the seventeenth resistor R17, a first end of the eighteenth resistor R18 and a control end of the fourth MOS tube Q4; a second end of the seventeenth resistor R17 is electrically connected with an anode of the sixth diode D6; a second end of the eighteenth resistor R18 is electrically connected with a second end 2 of the primary side of the transformer; a first end of the sixth capacitor C6 is electrically connected with a first end of the fourth MOS tube Q4, and a second end of the sixth capacitor C6 is electrically connected with a second end of the fourth MOS tube Q4.

[0045] Specifically, the thirteenth resistor R13 and the fourteenth resistor R14 can release the voltage of the control end of the third MOS tube Q3 when the first output end H0 of the control unit 111 is low, so that the third MOS tube Q3 is quickly turned off. The sixteenth resistor R16 and the seventeenth resistor R17 can release the voltage of the control end of the fourth MOS tube Q4 when the second output end L0 of the control unit 111 is low, so that the fourth MOS tube Q4 is quickly turned off. The fifth diode D5 is used to prevent current from passing through the fourteenth resistor R14 when the first output end H0 of the control unit 111 is high, and the sixth diode D6 is used to prevent current from passing through the seventeenth resistor R17 when the second output end L0 of the control unit 111 is high. The fifteenth resistor R15 and the eighteenth resistor R18 are used for filtering. The fifth capacitor C5 is used to absorb the peak voltage between the first end and the second end of the third MOS tube Q3. The sixth capacitor C6 is used to absorb the peak voltage between the first end and the second end of the fourth MOS tube Q4.

[0046] Optionally, continuing to refer to Figure 8The primary side resonant unit further comprises a seventh capacitor C7, a nineteenth resistor R19, a twentieth resistor R20, an eighth capacitor C8, a resonant inductor L1, a ninth capacitor C9, a seventh diode D7, an auxiliary power supply E2, a twenty-first resistor R21 and an input electrolytic capacitor E3; a first end of the seventh capacitor C7 is electrically connected with a current collection end CS of the control unit 111, a first end of the nineteenth resistor R19 and a first end of the twentieth resistor R20, a second end of the seventh capacitor C7 is electrically connected with a second end of the nineteenth resistor R19 and a second ground end SGND; a second end of the twentieth resistor R20 is electrically connected with a first end of the eighth capacitor C8; a second end of the eighth capacitor C8 is electrically connected with a first end of the ninth capacitor C9 and a second end 2 of the primary side of the transformer; a second end of the ninth capacitor C9 is electrically connected with a second end of the fourth MOS tube Q4; a first end of the resonant inductor L1 is electrically connected with an anode of the seventh diode D7, and a second end of the resonant inductor L1 is electrically connected with the second ground end SGND; a cathode of the seventh diode D7 is electrically connected with a first end of the auxiliary power supply E2 and a power supply end VCC of the control unit 111; a second end of the auxiliary power supply E2 is electrically connected with the second ground end SGND; a first end of the twenty-first resistor R21 is electrically connected with a high-voltage pin end HV of the control unit 111, and a second end of the twenty-first resistor R21 is electrically connected with a first end of the third MOS tube Q3 and a first end of the input electrolytic capacitor E3; a second end of the input electrolytic capacitor E3 is electrically connected with the second ground end SGND.

[0047] Specifically, the seventh capacitor C7 and the nineteenth resistor R19 can be used for filtering, the twentieth resistor R20 can be used for current limiting, the eighth capacitor C8 is used for direct current isolation and alternating current transmission, and the current collection end CS of the control unit 111 is used for collecting the current of the second end 2 of the primary side of the transformer. The leakage inductance of the transformer T1 can provide the resonant inductor L1 of the embodiment. The seventh diode D7 is used for rectification. The auxiliary power supply E2 is electrically connected with the power supply end VCC of the control unit 111, and the auxiliary power supply E2 is used for supplying power to the control unit 111. The twenty-first resistor R21 is used for current limiting. The input electrolytic capacitor E3 is also electrically connected with an external power supply VBUCK. The external power supply VBUCK also supplies power to the control unit 111.

[0048] Optionally, Figure 9 is another structure diagram of a self-driven synchronous rectification circuit according to an embodiment of the application, which is described with reference to Figure 9The self-driven synchronous rectification circuit provided in the embodiment further comprises a voltage acquisition feedback unit; the voltage acquisition feedback unit is configured to acquire an output voltage of the output electrolytic capacitor E1 and feed back the output voltage to the primary side resonance unit; the voltage acquisition feedback unit comprises a twenty-second resistor R22, a twenty-third resistor R23, a twenty-fourth resistor R24, a twenty-fifth resistor R25, a twenty-sixth resistor R26, a tenth capacitor C10, an optocoupler, a transient suppression diode U1, and an eleventh capacitor C11; a first end of the twenty-second resistor R22 is electrically connected with a second end of the output electrolytic capacitor E1 and a first end of the twenty-third resistor R23, a second end of the twenty-second resistor R22 is electrically connected with a first end of the tenth capacitor C10 and a first end of the twenty-fourth resistor R24; a second end of the twenty-third resistor R23 is electrically connected with a first end of a transmitting part PC1A of the optocoupler and a first end of the twenty-fifth resistor R25; a second end of the twenty-fifth resistor R25, a first end of the twenty-sixth resistor R26, and a cathode of the transient suppression diode U1 are electrically connected with a second end of the transmitting part PC1A of the optocoupler; a second end of the twenty-sixth resistor R26 is electrically connected with a second end of the tenth capacitor C10; an anode of the transient suppression diode U1 is electrically connected with a second end of the twenty-fourth resistor R24 and a first ground terminal GND; a first end of a receiving part PC1B of the optocoupler is electrically connected with a first end of the eleventh capacitor C11 and a feedback terminal FB of the control unit 111, and a second end of the receiving part PC1B of the optocoupler is electrically connected with a second end of the eleventh capacitor C11 and a second ground terminal SGND.

[0049] Specifically, the twenty-third resistor R23 is configured to limit current, the twenty-second resistor R22, the twenty-fourth resistor R24, and the transient suppression diode U1 are configured to acquire the output voltage of the output electrolytic capacitor E1, and the twenty-fifth resistor R25, the twenty-sixth resistor R26, and the tenth capacitor C10 are configured to filter. When the acquired output voltage exceeds a set value, the transmitting part PC1A of the optocoupler emits light, and the receiving part PC1B of the optocoupler is turned on, so as to feed back the acquired voltage to the control unit 111, and the control unit controls the turn-on duty ratio of the third MOS tube Q3 and the fourth MOS tube Q4 according to the acquired voltage.

[0050] Optionally, the first transistor and the second transistor are both triodes.

[0051] Specifically, compared with MOS tubes, triodes have low cost, and setting the first transistor and the second transistor as triodes can reduce the manufacturing cost of the self-driven synchronous rectification circuit.

[0052] The embodiment further provides a switching power supply, and the switching power supply comprises the self-driven synchronous rectification circuit provided in any of the embodiments of the present application.

[0053] The embodiment also provides a circuit board comprising the self-driven synchronous rectification circuit provided by any of the embodiments of the application.

[0054] Specifically, the circuit board provided by the embodiment can be a whole piece or be spliced by multiple small circuit boards.

[0055] It should be understood that the steps can be reordered, added or deleted using the various forms of flow shown above. For example, the steps described in the application can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions of the application can be achieved, which is not limited herein.

[0056] The specific embodiments described above do not constitute a limitation on the protection scope of the application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent replacement and improvement made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A self-driven synchronous rectification circuit, characterized by comprising: The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit.

2. The self-driven synchronous rectification circuit of claim 1, wherein, The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit.

3. The self-driven synchronous rectification circuit of claim 2, wherein, The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. 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The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a power supply circuit. The application relates to a The first end of the third capacitor is electrically connected with the second end of the transformer secondary side, and the second end of the third capacitor is electrically connected with the control end of the first MOS tube, the first end of the first transistor, the cathode of the third diode and the first end of the third resistor; The second end of the third resistor is electrically connected with the anode of the third diode and the control end of the first transistor; The second end of the first transistor is electrically connected with the first end of the fourth resistor; The second end of the fourth resistor is electrically connected with the second end of the first MOS tube and the first end of the output electrolytic capacitor; The first end of the fourth capacitor is electrically connected with the first end of the transformer secondary side, and the second end of the fourth capacitor is electrically connected with the control end of the second MOS tube, the first end of the second transistor, the cathode of the fourth diode and the first end of the fifth resistor; The second end of the fifth resistor is electrically connected with the anode of the fourth diode and the control end of the second transistor; The second end of the second transistor is electrically connected with the first end of the sixth resistor; The second end of the sixth resistor is electrically connected with the second end of the second MOS tube and the first end of the output electrolytic capacitor.

4. The self-driven synchronous rectification circuit of claim 3, wherein, Further comprising a seventh resistor, an eighth resistor, a ninth resistor, a first voltage stabilizing tube, a second voltage stabilizing tube, a tenth resistor, an eleventh resistor, a twelfth resistor, a third voltage stabilizing tube and a fourth voltage stabilizing tube; The first end of the seventh resistor is electrically connected with the second end of the transformer secondary side, and the second end of the seventh resistor is electrically connected with the first end of the third capacitor; the first end of the eighth resistor is electrically connected with the second end of the third capacitor, and the second end of the eighth resistor is electrically connected with the control end of the first MOS tube and the first end of the ninth resistor; the second end of the ninth resistor is electrically connected with the first end of the output electrolytic capacitor; the cathode of the first voltage stabilizing tube is electrically connected with the second end of the third capacitor, and the anode of the first voltage stabilizing tube is electrically connected with the anode of the second voltage stabilizing tube; the cathode of the second voltage stabilizing tube is electrically connected with the first end of the output electrolytic capacitor; The first end of the tenth resistor is electrically connected with the first end of the transformer secondary side, and the second end of the tenth resistor is electrically connected with the first end of the fourth capacitor; the first end of the eleventh resistor is electrically connected with the second end of the fourth capacitor, and the second end of the eleventh resistor is electrically connected with the control end of the second MOS tube and the first end of the twelfth resistor; the second end of the twelfth resistor is electrically connected with the first end of the output electrolytic capacitor; the cathode of the third voltage stabilizing tube is electrically connected with the second end of the fourth capacitor, and the anode of the third voltage stabilizing tube is electrically connected with the anode of the fourth voltage stabilizing tube; the cathode of the fourth voltage stabilizing tube is electrically connected with the first end of the output electrolytic capacitor.

5. The self-driven synchronous rectification circuit of claim 1, wherein, The primary side resonance unit comprises a control unit, a third MOS tube and a fourth MOS tube; The first output end of the control unit is electrically connected with the control end of the third MOS tube, the second output end of the control unit is electrically connected with the control end of the fourth MOS tube, the high-voltage pin end of the control unit is electrically connected with the first end of the third MOS tube, and the control unit is used for controlling the third MOS tube and the fourth MOS tube to be alternately turned on; the second end of the third MOS tube is electrically connected with the first end of the transformer primary side and the first end of the fourth MOS tube; the second end of the fourth MOS tube is electrically connected with the second end of the transformer primary side and the second ground end.

6. The self-driven synchronous rectification circuit of claim 5, wherein, The primary side resonance unit further comprises a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a fifth diode, a fifth capacitor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a sixth diode and a sixth capacitor; The first end of the thirteenth resistor is electrically connected with the first output end of the control unit and the cathode of the fifth diode, and the second end of the thirteenth resistor is electrically connected with the first end of the fourteenth resistor, the first end of the fifteenth resistor and the control end of the third MOS tube; The second end of the fourteenth resistor is electrically connected with the anode of the fifth diode; The second end of the fifteenth resistor is electrically connected with the first end of the transformer primary side; The first end of the fifth capacitor is electrically connected with the first end of the third MOS tube, and the second end of the fifth capacitor is electrically connected with the second end of the third MOS tube; The first end of the sixteenth resistor is electrically connected with the second output end of the control unit and the cathode of the sixth diode, and the second end of the sixteenth resistor is electrically connected with the first end of the seventeenth resistor, the first end of the eighteenth resistor and the control end of the fourth MOS tube; The second end of the seventeenth resistor is electrically connected with the anode of the sixth diode; The second end of the eighteenth resistor is electrically connected with the second end of the transformer primary side; The first end of the sixth capacitor is electrically connected with the first end of the fourth MOS tube, and the second end of the sixth capacitor is electrically connected with the second end of the fourth MOS tube.

7. The self-driven synchronous rectification circuit of claim 5, wherein, The primary side resonance unit further comprises a seventh capacitor, a nineteenth resistor, a twentieth resistor, an eighth capacitor, a resonance inductor, a ninth capacitor, a seventh diode, an auxiliary power supply, a twenty-first resistor and an input electrolytic capacitor; The first end of the seventh capacitor is electrically connected with the current collection end of the control unit, the first end of the nineteenth resistor and the first end of the twentieth resistor, and the second end of the seventh capacitor is electrically connected with the second end of the nineteenth resistor and the second ground end; The second end of the twentieth resistor is electrically connected with the first end of the eighth capacitor; The second end of the eighth capacitor is electrically connected with the first end of the ninth capacitor and the second end of the transformer primary side; The second end of the ninth capacitor is electrically connected with the second end of the fourth MOS tube; The first end of the resonance inductor is electrically connected with the anode of the seventh diode, and the second end of the resonance inductor is electrically connected with the second ground end; The cathode of the seventh diode is electrically connected with the first end of the auxiliary power supply and the power supply end of the control unit; The second end of the auxiliary power supply is electrically connected with the second ground end; A first end of the twenty-first resistor is electrically connected to a high-voltage pin end of the control unit, and a second end of the twenty-first resistor is electrically connected to a first end of the third MOS tube and a first end of the input electrolytic capacitor. A second end of the input electrolytic capacitor is electrically connected to a second ground end.

8. The self-driven synchronous rectification circuit of claim 7, wherein, Further comprising a voltage collection feedback unit; The voltage collection feedback unit is used to collect an output voltage of an output electrolytic capacitor and feed back the output voltage to the primary side resonance unit; The voltage collection feedback unit comprises a twenty-second resistor, a twenty-third resistor, a twenty-fourth resistor, a twenty-fifth resistor, a twenty-sixth resistor, a tenth capacitor, an optoelectronic coupler, a transient suppression diode, and an eleventh capacitor. A first end of the twenty-second resistor is electrically connected to a second end of the output electrolytic capacitor and a first end of the twenty-third resistor, and a second end of the twenty-second resistor is electrically connected to a first end of the tenth capacitor and a first end of the twenty-fourth resistor. A second end of the twenty-third resistor is electrically connected to a first end of an emitting part of the optoelectronic coupler and a first end of the twenty-fifth resistor. A second end of the emitting part of the optoelectronic coupler is electrically connected to a second end of the twenty-fifth resistor, a first end of the twenty-sixth resistor, and a cathode of the transient suppression diode. A second end of the twenty-sixth resistor is electrically connected to a second end of the tenth capacitor. An anode of the transient suppression diode is electrically connected to a second end of the twenty-fourth resistor and a first ground end. A first end of a receiving part of the optoelectronic coupler is electrically connected to a first end of the eleventh capacitor and a feedback end of the control unit, and a second end of the receiving part of the optoelectronic coupler is electrically connected to a second end of the eleventh capacitor and a second ground end.

9. The self-driven synchronous rectification circuit of claim 3, wherein, The first transistor and the second transistor are both triodes.

10. A switching power supply, characterized by comprising: The self-driven synchronous rectification circuit of any one of claims 1-9.

11. A circuit board, characterized by The self-driven synchronous rectification circuit of any one of claims 1-9.

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