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

Abstract

The invention discloses a self-driven synchronous rectification circuit, a switching power supply and a circuit board. 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 peak absorption unit, a second peak 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 the primary side resonance unit is used for controlling the first MOS tube and the second MOS tube to be switched on alternately; 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 peak 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 and the third end of the first potential maintaining unit, the first end of the output electrolytic capacitor and the first grounding end. According to the invention, the MOS tube can be prevented from being damaged by peak voltage, and the problem of driving oscillation of the MOS tube can be eliminated.

Description

Technical Field

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

[0002] MOS tubes are increasingly widely used as switches in switching power supply circuits. However, due to their small size and lack of protection, when feedback charging or spike pulses occur, large currents and voltages appear in the main circuit. If the protection is not timely, or there is no discharge circuit for the voltage and current, the bus voltage will exceed the withstand voltage and current of the MOS tube, which will burn the MOS tube, which is not conducive to the continuity and safety performance of the circuit.

[0003] Figure 1 This is a schematic diagram of the structure of an existing self-driven synchronous rectification circuit. Figure 1 , the primary resonance unit 110 can control the first MOS transistor Q1 and the second MOS transistor Q2 in the secondary circuit to alternately conduct so as to realize the power conversion from input to output. When the primary resonance unit 110 stops working, the secondary circuit will produce self-excited oscillation because the electricity of the output electrolytic capacitor E1 will not disappear immediately. The process is as follows: assuming that the first terminal A of the secondary side of the transformer is at a high potential just before the primary side stops working, the second MOS transistor Q2 is turned on, and the first MOS transistor Q1 is turned off. Then, the current flows from the positive electrode of the output electrolytic capacitor E1 to the third terminal B of the secondary side of the transformer, flows to the second MOS transistor Q2 through the second terminal C of the secondary side of the transformer, and returns to the negative electrode of the output electrolytic capacitor E1. When the voltage of the secondary winding is reversed, the first MOS transistor Q1 is turned on, the second MOS transistor Q2 is turned off, and the current flows from the positive electrode of the output electrolytic capacitor E1 to the third terminal B of the secondary side of the transformer, flows to the first MOS transistor Q1 through the first terminal A of the secondary side of the transformer, 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 tube and the second MOS tube. During the oscillation process, the first MOS tube Q1 and the second MOS tube Q2 will generate a high peak each time they are turned off, which exceeds the rated withstand voltage of the MOS tube and has the risk of damaging the MOS. Figure 2 This is a schematic diagram of the peak pulse voltage generated when the MOS tube is turned off. Figure 2 , pulse 1 represents the voltage difference between the source and drain of the MOS tube, pulse 2 represents the voltage difference between the gate and drain of the MOS tube, pulse 3 is a partial enlarged view of pulse 1, and pulse 4 is a partial enlarged view of pulse 2. Figure 2 It can be seen that the MOS tube will produce a higher spike each time it is turned off, which will damage the MOS tube. Summary of the invention

[0004] The present invention provides a self-driven synchronous rectification circuit, a switching power supply and a circuit board, which can prevent MOS tubes from being damaged by peak voltages and can eliminate the problem of MOS tube drive oscillation.

[0005] According to one aspect of the present invention, a self-driven synchronous rectification circuit is provided, the self-driven synchronous rectification circuit comprising: a primary resonance unit, a transformer, a first MOS tube, a second MOS tube, an output electrolytic capacitor, a first peak absorption unit, a second peak absorption unit, a first potential maintaining unit and a second potential maintaining unit;

[0006] The primary resonance unit is electrically connected to the first end and the second end of the primary side of the transformer, and the primary resonance unit is used to control the first MOS transistor and the second MOS transistor to be alternately turned on;

[0007] The first end of the first MOS transistor is electrically connected to the first end of the secondary side of the transformer and the first end of the first peak absorption unit, the control end of the first MOS transistor is electrically connected to the first end of the first potential maintaining unit, and the second end of the first MOS transistor is electrically connected to 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;

[0008] The first end of the second MOS transistor is electrically connected to the second end of the secondary side of the transformer and the first end of the second peak absorption unit, the control end of the second MOS transistor is electrically connected to the first end of the second potential maintaining unit, and the second end of the second MOS transistor is electrically connected to the second end, the third end of the second potential maintaining unit and the first end of the output electrolytic capacitor;

[0009] The second end of the first peak absorption unit is electrically connected to the third end of the secondary side of the transformer, the second end of the second peak absorption unit and the second end of the output electrolytic capacitor;

[0010] The fourth end of the first potential maintaining unit is electrically connected to the second end of the secondary side of the transformer, and the first potential maintaining unit is used to control the potential of the control end of the first MOS tube to maintain a low level when the potential of the second end of the secondary side of the transformer is at a low level; the fourth end of the second potential maintaining unit is electrically connected to the first end of the secondary side of the transformer, and the first potential maintaining unit is used to control the potential of the control end of the first MOS tube to maintain a low level when the potential of the first end of the secondary side of the transformer is at a low level.

[0011] According to another aspect of the present invention, a switching power supply is provided. The switching power supply includes the self-driven synchronous rectification circuit provided by any embodiment of the present invention.

[0012] According to another aspect of the present invention, a circuit board is provided. The circuit board includes the self-driven synchronous rectification circuit provided by any embodiment of the present invention.

[0013] The present embodiment provides a self-driven synchronous rectification circuit, which includes a primary resonance unit, a transformer, a first MOS tube, a second MOS tube, an output electrolytic capacitor, a first peak absorption unit electrically connected to 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 peak absorption unit electrically connected to 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 peak absorption unit can absorb the peak voltage between the first end and the second end of the first MOS tube when the first MOS tube is turned off. The second peak absorption unit can absorb the peak 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 present embodiment also 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 low level when the third end of the first transformer is low level, thereby eliminating the problem of driving oscillation of the first MOS tube, and the second potential maintaining unit can control the control end of the second MOS tube to be low level when the first end of the first transformer is low level, thereby eliminating the problem of driving oscillation of the second MOS tube. In summary, the self-driven synchronous rectification circuit provided in this embodiment can prevent the MOS tube from being damaged by the peak voltage and can eliminate the problem of MOS tube driving oscillation.

[0014] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 It is a structural schematic diagram of an existing self-driven synchronous rectification circuit;

[0017] Figure 2 It is a schematic diagram of the peak 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 provided according to an embodiment of the present invention;

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

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

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

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

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

[0024] Fig. 9 Detailed description is a structural diagram of another self-driven synchronous rectification circuit provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

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

[0027] Figure 3 is a schematic diagram of a self-driven synchronous rectification circuit according to an embodiment of the present invention, with reference to Figure 3The self-driven synchronous rectification circuit provided in this embodiment includes: a primary resonance unit 110, a transformer T1, a first MOS tube Q1, a second MOS tube Q2, an output electrolytic capacitor E1, a first peak absorption unit 120, a second peak absorption unit 130, a first potential maintaining unit 140 and a second potential maintaining unit 150.

[0028] The primary resonance unit 110 is electrically connected to the first end 1 and the second end 2 of the primary side of the transformer, and the primary resonance unit 110 is used to control the first MOS transistor Q1 and the second MOS transistor Q2 to be alternately turned on; the first end of the first MOS transistor Q1 is electrically connected to the first end A of the secondary side of the transformer and the first end of the first peak absorption unit 120, the control end of the first MOS transistor Q1 is electrically connected to the first end of the first potential maintaining unit 140, and the second end of the first MOS transistor Q1 is electrically connected to the second end, the third end, the first end of the output electrolytic capacitor E1 and the first grounding end GND of the first potential maintaining unit 140; the first end of the second MOS transistor Q2 is electrically connected to the second end C of the secondary side of the transformer and the first end of the second peak absorption unit 130, the control end of the second MOS transistor Q2 is electrically connected to the first end of the second potential maintaining unit 150, and the second MO The second end of the S transistor Q2 is electrically connected to the second end and 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 peak absorption unit 120 is electrically connected to the third end B of the secondary side of the transformer, the second end of the second peak 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 to the second end C of the secondary side of the transformer, and the first potential maintaining unit 140 is used to control the potential of the control end of the first MOS transistor Q1 to maintain a low level when the potential of the second end C of the secondary side of the transformer is at a low level; the fourth end of the second potential maintaining unit 150 is electrically connected to the first end A of the secondary side of the transformer, and the second potential maintaining unit 150 is used to control the potential of the control end of the first MOS transistor Q1 to maintain a low level when the potential of the first end A of the secondary side of the transformer is at a low level.

[0029] Specifically, the control end of the first MOS transistor Q1 is the gate, the first end of the first MOS transistor Q1 is the source, and the second end of the first MOS transistor Q1 is the drain. The control end of the second MOS transistor Q2 is the gate, the first end of the second MOS transistor Q2 is the source, and the second end of the second MOS transistor Q2 is the drain.

[0030] The primary resonance unit 120 is used to control the first MOS tube Q1 and the second MOS tube Q2 to be alternately turned on, and the specific control process can be: the primary resonance unit 120 controls the potential of the first end A of the secondary side of the transformer to be high level and the potential of the second end C to be low level to control the second MOS tube Q2 to be turned on, and the first MOS tube Q1 to be turned off. The primary resonance unit 120 controls the potential of the first end A of the secondary side of the transformer to be low level and the potential of the second end C to be high level to control the first MOS tube Q1 to be turned on, and the second MOS tube Q2 to be turned off. In one cycle, the conduction ratio of the first MOS tube Q1 and the conduction ratio of the second MOS tube Q2 can be 50% each.

[0031] The specific working principle of the self-driven synchronous rectification circuit provided in this embodiment can be: when the primary resonance unit 110 stops working, the potential of the first terminal A of the secondary side of the transformer is low, the potential of the second terminal C is high, the first MOS tube Q1 is turned on, and the second MOS tube Q2 is turned off. At this time, since the current between the third terminal B and the second terminal C of the secondary side of the transformer cannot change suddenly, a spike voltage will be generated between the first terminal and the second terminal of the second MOS tube Q2 (the waveform of the spike voltage is as shown in FIG. Figure 2 In the embodiment, a second peak absorption unit 130 is provided to absorb the peak voltage between the first end and the second end of the second MOS tube Q2, so that the voltage between the first end and the second end of the second MOS tube Q2 drops below the rated specification, thereby solving the problem that the second MOS tube Q2 is damaged by the peak voltage. At the same time, when the potential of the first end A of the secondary side of the transformer is at a low level, the second potential maintaining unit 150 controls the potential of the control end of the second MOS tube Q2 to maintain a low level, that is, the second potential maintaining unit 150 controls the control end of the second MOS tube Q2 to be connected to the first ground end GND, which can eliminate the voltage oscillation problem between the control end and the second end of the second MOS tube Q2 (the waveform of the voltage oscillation is as shown in FIG. 1 ). Figure 22 and the spike waveform in pulse 4 in the secondary side). Similarly, when the primary resonance unit 110 stops working, the potential of the first terminal A of the secondary side of the transformer is high, the potential of the second terminal C is low, the first MOS transistor Q1 is turned off, and the second MOS transistor Q2 is turned on. At this time, since the current between the third terminal B and the first terminal A of the secondary side of the transformer cannot change suddenly, a spike voltage will be generated between the first terminal and the second terminal of the first MOS transistor Q1. In this embodiment, a first spike absorption unit 120 is provided to absorb the spike voltage between the first terminal and the second terminal of the first MOS transistor Q1, so that the voltage between the first terminal and the second terminal of the first MOS transistor Q1 drops below the rated specification, solving the problem that the first MOS transistor Q1 is damaged by the spike voltage. At the same time, when the potential of the second terminal C of the secondary side of the transformer is low, the first potential maintaining unit 140 controls the potential of the control terminal of the first MOS transistor Q1 to maintain a low level, that is, the first potential maintaining unit 140 controls the control terminal of the first MOS transistor Q2 to be turned on with the first ground terminal GND, which can eliminate the voltage oscillation problem between the control terminal and the second terminal of the first MOS transistor Q1. It can be seen that the self-driven synchronous rectification circuit provided in this embodiment can prevent the first MOS transistor Q1 and the second MOS transistor Q2 from being damaged by the peak voltage, and can eliminate the problem of driving oscillation of the first MOS transistor Q1 and the second MOS transistor Q2.

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

[0033] Optional, Figure 4 is a structural diagram of another self-driven synchronous rectification circuit provided according to an embodiment of the present invention, with reference to Figure 4 The first peak absorption unit 120 includes a first diode D1, a first capacitor C1 and a first resistor R1; the second peak absorption unit 130 includes 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 tube Q1, and 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 tube Q2, and 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 a spike voltage exists between the first end and the second end of the first MOS tube Q1, the first capacitor C1 absorbs and stores the spike voltage between the first end and the second end of the first MOS tube Q1, the first resistor R1 consumes the voltage stored in the first capacitor C1, and finally eliminates the spike voltage between the first end and the second end of the first MOS tube Q1, and the first diode D1 is used to prevent the current from flowing to the first MOS tube Q1 through the second end of the first resistor R1 and damaging the first MOS tube Q1. Similarly, when a spike voltage exists between the first end and the second end of the second MOS tube Q2, the second capacitor C2 absorbs and stores the spike voltage between the first end and the second end of the second MOS tube Q2, the second resistor R2 consumes the voltage stored in the second capacitor C2, and finally eliminates the spike voltage between the first end and the second end of the second MOS tube Q2, and the second diode D2 is used to prevent the current from flowing to the second MOS tube Q2 through the second end of the second resistor R2 and damaging the second MOS tube Q2.

[0035] Optional, Figure 5 is a structural diagram of another self-driven synchronous rectification circuit provided according to an embodiment of the present invention, with reference to Figure 5The first potential maintaining unit 140 includes 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 includes 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 to the second end C of the secondary side of the transformer, the second end of the third capacitor C3 is electrically connected to the control end of the first MOS tube 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 to 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 to the fourth capacitor C4, the fifth resistor R5, the fourth diode D4, the second transistor T2 and the sixth resistor R6; the first end of the third capacitor C3 is electrically connected to the second end C of the secondary side of the transformer, the second end of the third capacitor C3 is electrically connected to the control end of the first MOS tube 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 to 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 to the fourth The first end of the fourth resistor R4 is electrically connected to the second end of the first MOS tube Q1 and the first end of the output electrolytic capacitor E1; the first end of the fourth capacitor C4 is electrically connected to the first end A of the secondary side of the transformer, and the second end of the fourth capacitor C4 is electrically connected to the control end of the second MOS tube 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 to 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 to the first end of the sixth resistor R6; the second end of the sixth resistor R6 is electrically connected to the second end of the second MOS tube 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 blocking direct current and passing alternating current.

[0037] When the primary resonance unit 110 stops working and the potential of the second end C of the secondary side of the transformer is at a low level, since the voltage across the third capacitor C3 cannot change suddenly, the voltage at the second end of the third capacitor C3 is at a low level, and when the control end of the first transistor T1 is at a low level, the first transistor T1 is turned on, so that the control end of the first MOS tube Q1 is grounded, even if the control end of the first MOS tube Q1 maintains a low level, the problem of oscillation of the driving voltage between the control end of the first MOS tube Q1 and its second end is eliminated. The third resistor R3 and the fourth resistor R4 are used for current limiting, the third diode D3 is used to prevent current backflow, and the third capacitor C3 is used to block DC and pass AC. Similarly, when the primary resonance unit 110 stops working and the potential of the first terminal A of the secondary side of the transformer is at a low level, since the voltage across the fourth capacitor C4 cannot change suddenly, the voltage at the second terminal of the fourth capacitor C4 is at a low level, and when the control terminal of the second transistor T2 is at a low level, the second transistor T2 is turned on, so that the control terminal of the second MOS tube Q2 is grounded, even if the control terminal of the second MOS tube Q2 maintains a low level, the problem of oscillation of the driving voltage between the control terminal and the second terminal of the second MOS tube Q2 is eliminated. The fifth resistor R5 and the sixth resistor R6 are used for current limiting, the fourth diode D4 is used to prevent current backflow, and the fourth capacitor C4 is used to block DC and pass AC.

[0038] Optional, Figure 6 is a structural diagram of another self-driven synchronous rectification circuit provided according to an embodiment of the present invention, with reference to Figure 6 The self-driven synchronous rectification circuit provided in this embodiment also includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a first voltage regulator tube Z1, a second voltage regulator tube Z2, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a third voltage regulator tube Z3 and a fourth voltage regulator tube Z4.

[0039] The first end of the seventh resistor R7 is electrically connected to the second end C of the secondary side of the transformer, and the second end of the seventh resistor R7 is electrically connected to the first end of the third capacitor C3; the first end of the eighth resistor R8 is electrically connected to the second end of the third capacitor C3, and the second end of the eighth resistor R8 is electrically connected to the control end of the first MOS tube Q1 and the first end of the ninth resistor R9; the second end of the ninth resistor R9 is electrically connected to the first end of the output electrolytic capacitor E1; the cathode of the first voltage regulator tube Z1 is electrically connected to the second end of the third capacitor C3, and the anode of the first voltage regulator tube Z1 is electrically connected to the anode of the second voltage regulator tube Z2; the cathode of the second voltage regulator tube Z2 is electrically connected to the first end of the output electrolytic capacitor E1; the tenth resistor R The first end of the first resistor R10 is electrically connected to the first end A of the secondary side of the transformer, the second end of the tenth resistor R10 is electrically connected to the first end of the fourth capacitor C4; the first end of the eleventh resistor R11 is electrically connected to the second end of the fourth capacitor C4, the second end of the eleventh resistor R11 is electrically connected to the control end of the second MOS tube Q2 and the first end of the twelfth resistor R12; the second end of the twelfth resistor R12 is electrically connected to the first end of the output electrolytic capacitor E1; the cathode of the third voltage-stabilizing tube Z3 is electrically connected to the second end of the fourth capacitor C4, the anode of the third voltage-stabilizing tube Z3 is electrically connected to the anode of the fourth voltage-stabilizing tube Z4; the cathode of the fourth voltage-stabilizing tube Z4 is electrically connected to 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 to release the voltage of the control end of the first MOS tube Q1 when the second end C of the secondary side of the transformer is at a low level, so that the first MOS tube Q1 is quickly turned off. The eleventh resistor R11 and the twelfth resistor R12 are used to release the voltage of the control end of the second MOS tube Q2 when the first end A of the secondary side of the transformer is at a low level, so that the second MOS tube Q2 is quickly turned off.

[0041] The first voltage regulator tube Z1 and the second voltage regulator tube Z2 are used to stabilize the voltage between the first end and the second end of the first MOS tube Q1 within a specific range. The third voltage regulator tube Z3 and the fourth voltage regulator tube Z4 are used to stabilize the voltage between the first end and the second end of the second MOS tube Q2 within a specific range.

[0042] Optional, Figure 7 is a structural diagram of another self-driven synchronous rectification circuit provided according to an embodiment of the present invention, with reference to Figure 7The primary resonance unit includes a control unit 111, a third MOS transistor Q3 and a fourth MOS transistor Q4; a first output terminal H0 of the control unit 111 is electrically connected to a control terminal of the third MOS transistor Q3, a second output terminal L0 of the control unit 111 is electrically connected to a control terminal of the fourth MOS transistor Q4, a high voltage pin terminal HV of the control unit 111 is electrically connected to a first terminal of the third MOS transistor Q3, and the control unit 111 is used to control the third MOS transistor Q3 and the fourth MOS transistor Q4 to be alternately turned on; a second terminal of the third MOS transistor Q3 is electrically connected to a first terminal 1 of the primary side of the transformer and a first terminal of the fourth MOS transistor Q4; a second terminal of the fourth MOS transistor Q4 is electrically connected to a second terminal 2 of the primary side of the transformer and a second ground terminal SGND.

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

[0044] Optional, Figure 8 is a structural diagram of another self-driven synchronous rectification circuit provided according to an embodiment of the present invention, with reference to Figure 8The primary resonance unit also includes 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 to the first output end H0 of the control unit 111 and the cathode of the fifth diode D5, a second end of the thirteenth resistor R13 is electrically connected to the first end of the fourteenth resistor R14, a first end of the fifteenth resistor R15 and the control end of the third MOS tube Q3; a second end of the fourteenth resistor R14 is electrically connected to the anode of the fifth diode D5; a second end of the fifteenth resistor R15 is electrically connected to the first end 1 of the primary side of the transformer; The first end is electrically connected to the first end of the third MOS tube Q3, and the second end of the fifth capacitor C5 is electrically connected to the second end of the third MOS tube Q3; the first end of the sixteenth resistor R16 is electrically connected to the second output end L0 of the control unit 111 and the cathode of the sixth diode D6, and the second end of the sixteenth resistor R16 is electrically connected to the first end of the seventeenth resistor R17, the first end of the eighteenth resistor R18 and the control end of the fourth MOS tube Q4; the second end of the seventeenth resistor R17 is electrically connected to the anode of the sixth diode D6; the second end of the eighteenth resistor R18 is electrically connected to the second end 2 of the primary side of the transformer; the first end of the sixth capacitor C6 is electrically connected to the first end of the fourth MOS tube Q4, and the second end of the sixth capacitor C6 is electrically connected to the 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 at a low level, 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 at a low level, so that the fourth MOS tube Q4 is quickly turned off. The fifth diode D5 is used to prevent the current from passing through the fourteenth resistor R14 when the first output end H0 of the control unit 111 is at a high level, and the sixth diode D6 is used to prevent the current from passing through the seventeenth resistor R17 when the second output end L0 of the control unit 111 is at a high level. 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] Optional, continue to refer to Figure 8The primary resonance unit also includes 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 to the current collection terminal 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 to the second end of the nineteenth resistor R19 and the second ground terminal SGND; a second end of the twentieth resistor R20 is electrically connected to the first end of the eighth capacitor C8; a second end of the eighth capacitor C8 is electrically connected to the first end of the ninth capacitor C9 and the second end 2 of the primary side of the transformer The first end of the resonant inductor L1 is electrically connected to the anode of the seventh diode D7, and the second end of the resonant inductor L1 is electrically connected to the second ground terminal SGND; the cathode of the seventh diode D7 is electrically connected to the first end of the auxiliary power supply E2 and the power supply terminal VCC of the control unit 111; the second end of the auxiliary power supply E2 is electrically connected to the second ground terminal SGND; the first end of the twenty-first resistor R21 is electrically connected to the high-voltage pin terminal HV of the control unit 111, and the second end of the twenty-first resistor R21 is electrically connected to the first end of the third MOS tube Q3 and the first end of the input electrolytic capacitor E3; the second end of the input electrolytic capacitor E3 is electrically connected to the second ground terminal 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 to isolate DC and pass AC, and the current collection terminal CS of the control unit 111 is used to collect the current of the second terminal 2 of the primary side of the transformer. The leakage inductance of the transformer T1 can be the resonant inductor L1 provided in this embodiment. The seventh diode D7 is used for rectification. The auxiliary power supply E2 is electrically connected to the power supply terminal VCC of the control unit 111, and the auxiliary power supply E2 is used to power the control unit 111. The twenty-first resistor R21 is used for current limiting. The input electrolytic capacitor E3 is also electrically connected to the external power supply VBUCK. The external power supply VBUCK also powers the control unit 111.

[0048] Optional, Fig. 9 is a structural diagram of another self-driven synchronous rectification circuit provided according to an embodiment of the present invention, with reference to Fig. 9The self-driven synchronous rectification circuit provided in this embodiment also includes a voltage acquisition feedback unit; the voltage acquisition feedback unit is used to collect the output voltage of the output electrolytic capacitor E1 and feed the output voltage back to the primary resonance unit; the voltage acquisition feedback unit includes 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, a photocoupler, a transient suppression diode U1 and an eleventh capacitor C11; the first end of the twenty-second resistor R22 is electrically connected to the second end of the output electrolytic capacitor E1 and the first end of the twenty-third resistor R23, and the second end of the twenty-second resistor R22 is electrically connected to the first end of the tenth capacitor C10 and the first end of the twenty-fourth resistor R24; the twenty-third resistor R23 The second end is electrically connected to the first end of the transmitting part PC1A of the photocoupler and the first end of the twenty-fifth resistor R25; the second end of the transmitting part PC1A of the photocoupler is electrically connected to the second end of the twenty-fifth resistor R25, the first end of the twenty-sixth resistor R26 and the cathode of the transient suppression diode U1; the second end of the twenty-sixth resistor R26 is electrically connected to the second end of the tenth capacitor C10; the anode of the transient suppression diode U1 is electrically connected to the second end of the twenty-fourth resistor R24 ​​and the first ground terminal GND; the first end of the receiving part PC1B of the photocoupler is electrically connected to the first end of the eleventh capacitor C11 and the feedback terminal FB of the control unit 111, and the second end of the receiving part PC1B of the photocoupler is electrically connected to the second end of the eleventh capacitor C11 and the second ground terminal SGND.

[0049] Specifically, the twenty-third resistor R23 is used for current limiting, and the twenty-second resistor R22, the twenty-fourth resistor R24 ​​and the transient suppression diode U1 are used to collect the output voltage of the output electrolytic capacitor E1. The twenty-fifth resistor R25, the twenty-sixth resistor R26 and the tenth capacitor C10 are used for filtering. When the collected output voltage exceeds the set value, the transmitting part PC1A of the photocoupler emits light, which can turn on the receiving part PC1B of the photocoupler, thereby feeding back the collected voltage to the control unit 111, and the control unit controls the conduction ratio of the third MOS tube Q3 and the fourth MOS tube Q4 according to the collected voltage.

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

[0051] Specifically, compared with MOS transistors, triodes have lower costs, and setting the first transistor and the second transistor to be triodes can reduce the manufacturing cost of the self-driven synchronous rectification circuit.

[0052] This embodiment further provides a switching power supply, which is the self-driven synchronous rectification circuit provided by any embodiment of the present invention.

[0053] This embodiment also provides a circuit board, which includes the self-driven synchronous rectification circuit provided by any embodiment of the present invention.

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

[0055] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0056] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A self-driven synchronous rectification circuit, characterized in that: include: A primary resonance unit, a transformer, a first MOS tube, a second MOS tube, an output electrolytic capacitor, a first peak absorption unit, a second peak absorption unit, a first potential maintaining unit, and a second potential maintaining unit; The primary resonance unit is electrically connected to the first end and the second end of the primary side of the transformer, and the primary resonance unit is used to control the first MOS transistor and the second MOS transistor to be alternately turned on; The first end of the first MOS transistor is electrically connected to the first end of the secondary side of the transformer and the first end of the first peak absorption unit, the control end of the first MOS transistor is electrically connected to the first end of the first potential maintaining unit, and the second end of the first MOS transistor is electrically connected to 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 first end of the second MOS transistor is electrically connected to the second end of the secondary side of the transformer and the first end of the second peak absorption unit, the control end of the second MOS transistor is electrically connected to the first end of the second potential maintaining unit, and the second end of the second MOS transistor is electrically connected to the second end, the third end of the second potential maintaining unit and the first end of the output electrolytic capacitor; The second end of the first peak absorption unit is electrically connected to the third end of the secondary side of the transformer, the second end of the second peak absorption unit and the second end of the output electrolytic capacitor; The fourth end of the first potential maintaining unit is electrically connected to the second end of the secondary side of the transformer, and the first potential maintaining unit is used to control the potential of the control end of the first MOS tube to maintain a low level when the potential of the second end of the secondary side of the transformer is at a low level; the fourth end of the second potential maintaining unit is electrically connected to the first end of the secondary side of the transformer, and the first potential maintaining unit is used to control the potential of the control end of the first MOS tube to maintain a low level when the potential of the first end of the secondary side of the transformer is at a low level.

2. The self-driven synchronous rectification circuit according to claim 1, characterized in that: The first peak absorption unit includes a first diode, a first capacitor and a first resistor; the second peak absorption unit includes a second diode, a second capacitor and a second resistor; An anode of the first diode is electrically connected to a first end of the first MOS transistor, and a cathode of the first diode is electrically connected to a first end of the first capacitor and a first end of the first resistor; The second end of the first capacitor is electrically connected to the third end of the secondary side of the transformer, the second end of the first resistor and the second end of the output electrolytic capacitor; An anode of the second diode is electrically connected to a first end of the second MOS transistor, and a cathode of the second diode is electrically connected to a first end of the second capacitor and a first end of the second resistor; The second end of the second capacitor is electrically connected to the third end of the secondary side of the transformer and the second end of the second resistor.

3. The self-driven synchronous rectification circuit according to claim 2, characterized in that: The first potential maintaining unit includes a third capacitor, a third resistor, a third diode, a first transistor and a fourth resistor; The second potential maintaining unit includes a fourth capacitor, a fifth resistor, a fourth diode, a second transistor and a sixth resistor; The first end of the third capacitor is electrically connected to the second end of the secondary side of the transformer, and the second end of the third capacitor is electrically connected to 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 to the anode of the third diode and the control end of the first transistor; The second end of the first transistor is electrically connected to the first end of the fourth resistor; The second end of the fourth resistor is electrically connected to 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 to the first end of the secondary side of the transformer, and the second end of the fourth capacitor is electrically connected to the control end of the second MOS transistor, 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 to the anode of the fourth diode and the control end of the second transistor; The second end of the second transistor is electrically connected to the first end of the sixth resistor; The second end of the sixth resistor is electrically connected to the second end of the second MOS tube and the first end of the output electrolytic capacitor.

4. The self-driven synchronous rectification circuit according to claim 3, characterized in that: It also includes a seventh resistor, an eighth resistor, a ninth resistor, a first voltage regulator tube, a second voltage regulator tube, a tenth resistor, an eleventh resistor, a twelfth resistor, a third voltage regulator tube and a fourth voltage regulator tube; The first end of the seventh resistor is electrically connected to the second end of the secondary side of the transformer, and the second end of the seventh resistor is electrically connected to the first end of the third capacitor; the first end of the eighth resistor is electrically connected to the second end of the third capacitor, and the second end of the eighth resistor is electrically connected to 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 to the first end of the output electrolytic capacitor; the cathode of the first voltage regulator tube is electrically connected to the second end of the third capacitor, and the anode of the first voltage regulator tube is electrically connected to the anode of the second voltage regulator tube; the cathode of the second voltage regulator tube is electrically connected to the first end of the output electrolytic capacitor; The first end of the tenth resistor is electrically connected to the first end of the secondary side of the transformer, and the second end of the tenth resistor is electrically connected to the first end of the fourth capacitor; the first end of the eleventh resistor is electrically connected to the second end of the fourth capacitor, and the second end of the eleventh resistor is electrically connected to 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 to the first end of the output electrolytic capacitor; the cathode of the third voltage regulator tube is electrically connected to the second end of the fourth capacitor, and the anode of the third voltage regulator tube is electrically connected to the anode of the fourth voltage regulator tube; the cathode of the fourth voltage regulator tube is electrically connected to the first end of the output electrolytic capacitor.

5. The self-driven synchronous rectification circuit according to claim 1, characterized in that: The primary resonance unit includes a control unit, a third MOS tube and a fourth MOS tube; The first output end of the control unit is electrically connected to the control end of the third MOS tube, the second output end of the control unit is electrically connected to the control end of the fourth MOS tube, the high-voltage pin end of the control unit is electrically connected to the first end of the third MOS tube, and the control unit is used to control 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 to the first end of the primary side of the transformer and the first end of the fourth MOS tube; the second end of the fourth MOS tube is electrically connected to the second end of the primary side of the transformer and the second grounding end.

6. The self-driven synchronous rectification circuit according to claim 5, characterized in that: The primary resonance unit further includes 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 to 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 to 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 to the anode of the fifth diode; The second end of the fifteenth resistor is electrically connected to the first end of the primary side of the transformer; The first end of the fifth capacitor is electrically connected to the first end of the third MOS transistor, and the second end of the fifth capacitor is electrically connected to the second end of the third MOS transistor; The first end of the sixteenth resistor is electrically connected to 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 to the first end of the seventeenth resistor, the first end of the eighteenth resistor and the control end of the fourth MOS transistor; The second end of the seventeenth resistor is electrically connected to the anode of the sixth diode; The second end of the eighteenth resistor is electrically connected to the second end of the primary side of the transformer; The first end of the sixth capacitor is electrically connected to the first end of the fourth MOS transistor, and the second end of the sixth capacitor is electrically connected to the second end of the fourth MOS transistor.

7. The self-driven synchronous rectification circuit according to claim 5, characterized in that: The primary resonance unit further includes a seventh capacitor, a nineteenth resistor, a twentieth resistor, an eighth capacitor, a resonant 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 to 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 to the second end of the nineteenth resistor and the second ground end; The second end of the twentieth resistor is electrically connected to the first end of the eighth capacitor; The second end of the eighth capacitor is electrically connected to the first end of the ninth capacitor and the second end of the primary side of the transformer; The second end of the ninth capacitor is electrically connected to the second end of the fourth MOS tube; The first end of the resonant inductor is electrically connected to the anode of the seventh diode, and the second end of the resonant inductor is electrically connected to the second ground terminal; The cathode of the seventh diode is electrically connected to 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 to 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; The second end of the input electrolytic capacitor is electrically connected to the second ground end.

8. The self-driven synchronous rectification circuit according to claim 7, characterized in that: It also includes a voltage acquisition feedback unit; The voltage collection and feedback unit is used to collect the output voltage of the output electrolytic capacitor and feed the output voltage back to the primary resonance unit; The voltage collection feedback unit includes a twenty-second resistor, a twenty-third resistor, a twenty-fourth resistor, a twenty-fifth resistor, a twenty-sixth resistor, a tenth capacitor, a photocoupler, a transient suppression diode and an eleventh capacitor; The first end of the twenty-second resistor is electrically connected to the second end of the output electrolytic capacitor and the first end of the twenty-third resistor, and the second end of the twenty-second resistor is electrically connected to the first end of the tenth capacitor and the first end of the twenty-fourth resistor; The second end of the twenty-third resistor is electrically connected to the first end of the transmitting portion of the photocoupler and the first end of the twenty-fifth resistor; The second end of the transmitting portion of the photocoupler is electrically connected to the second end of the twenty-fifth resistor, the first end of the twenty-sixth resistor, and the cathode of the transient suppression diode; The second end of the twenty-sixth resistor is electrically connected to the second end of the tenth capacitor; The anode of the transient suppression diode is electrically connected to the second end of the twenty-fourth resistor and the first ground terminal; The first end of the receiving part of the photocoupler is electrically connected to the first end of the eleventh capacitor and the feedback end of the control unit, and the second end of the receiving part of the photocoupler is electrically connected to the second end of the eleventh capacitor and the second ground end.

9. The self-driven synchronous rectification circuit according to claim 3, characterized in that: The first transistor and the second transistor are both triodes.

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

11. A circuit board, characterized in that: A self-driven synchronous rectification circuit comprising any one of claims 1 to 9.

Images