Self-driven synchronous rectification circuit, LLC resonance circuit and power supply device

Abstract

The embodiment of the utility model discloses a self-driven synchronous rectification circuit, an LLC resonance circuit and a power supply device, the self-driven synchronous rectification circuit comprises a first switch circuit, a second switch circuit, a first driving circuit, a second driving circuit, a first clamping circuit and a second clamping circuit, the input end of the first switch circuit is grounded, and the input end of the second switch circuit is grounded; the output end of the first switching circuit is connected with the first end of the first secondary coil; the input end of the second switching circuit is grounded, and the output end of the second switching circuit is connected with the second end of the second secondary coil; the input end of the first driving circuit is connected with the second end of the second secondary coil; the input end of the second driving circuit is connected with the first end of the first secondary coil; the first clamping circuit and the second clamping circuit respectively clamp the voltage of the corresponding driving circuit, so that the damage probability of the first driving circuit and the second driving circuit is reduced, and the self-driven synchronous rectification circuit can have a relatively long service life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of driving control, in particular to a self-driven synchronous rectification circuit, an LLC resonant circuit and a power supply device. BACKGROUND

[0002] In the field of power supply design, the LLC resonant circuit is widely used in various power supplies as a common design method. Among them, the LLC resonant circuit mainly includes a primary coil, a secondary coil, a switch tube and a driving circuit, and the most important feature is that the voltage at the high potential end of the secondary coil drives the switch tube through the driving circuit, so that the low potential end of the secondary coil and the load are turned on to form a power supply loop.

[0003] In actual application, since the controlled end of the switch tube has a parasitic capacitor, when the switch tube is closed, the parasitic capacitor of the switch tube discharges, and the discharge voltage of the parasitic capacitor will be applied to the driving circuit, which is easy to cause damage to the driving circuit, thereby affecting the service life of the self-driven synchronous rectification circuit. CONTENT OF THE INVENTION

[0004] The embodiments of the present application provide a self-driven synchronous rectification circuit, an LLC resonant circuit and a power supply device, which are aimed at clamping the voltage between the output end voltage of the first driving circuit and the controlled end of the first driving circuit to the first voltage by the first clamping circuit, so as to prevent the first driving circuit from being damaged, so that the first driving circuit can have a longer service life, and thus the self-driven synchronous rectification circuit can have a longer service life, so that the LLC resonant circuit can have a longer service life; the voltage between the output end voltage of the second driving circuit and the controlled end of the second driving circuit is clamped to the second voltage by the second clamping circuit, so as to prevent the second driving circuit from being damaged, so that the second driving circuit can have a longer service life, and thus the self-driven synchronous rectification circuit can have a longer service life, so that the LLC resonant circuit can have a longer service life.

[0005] The embodiment of the present application provides a self-driven synchronous rectification circuit, which is suitable for an LLC resonant circuit, the LLC resonant circuit comprising a first secondary coil, a second secondary coil and the self-driven synchronous rectification circuit, an output end of the self-driven synchronous rectification circuit being connected with a second end of the first secondary coil and a first end of the second secondary coil, the self-driven synchronous rectification circuit comprising a first switch circuit, a second switch circuit, a first driving circuit, a second driving circuit, a first clamping circuit and a second clamping circuit, an input end of the first switch circuit being grounded, an output end of the first switch circuit being used for being connected with a first end of the first secondary coil; an input end of the second switch circuit being grounded, an output end of the second switch circuit being used for being connected with a second end of the second secondary coil; an input end of the first driving circuit being used for being connected with the second end of the second secondary coil; an input end of the second driving circuit being used for being connected with the first end of the first secondary coil; an input end of the first clamping circuit being connected with an output end of the first driving circuit, an output end of the first clamping circuit being connected with a controlled end of the first driving circuit, so that when the first clamping circuit is turned on, the voltage between the output end of the first driving circuit and the controlled end of the first driving circuit is clamped at a first voltage; an input end of the second clamping circuit being connected with an output end of the second driving circuit, an output end of the second clamping circuit being connected with a controlled end of the second driving circuit, so that when the second clamping circuit is turned on, the voltage between the output end of the second driving circuit and the controlled end of the second driving circuit is clamped at a second voltage.

[0006] Based on the above embodiment, when the first switch circuit is turned off, the first clamping circuit is forwardly turned on, the parasitic capacitance of the controlled end of the first switch circuit can be discharged through the first clamping circuit, and because the first clamping circuit is forwardly turned on, the voltage between the output end of the first driving circuit and the controlled end of the first driving circuit can be clamped at the first voltage, the first voltage being less than the voltage resistance value between the output end and the controlled end of the first driving circuit, so that the first driving circuit can be prevented from being damaged, so that the first driving circuit can have a longer service life, and further so that the self-driven synchronous rectification circuit can have a longer service life, and further so that the LLC resonant circuit can have a longer service life.

[0007] When the second switch circuit is turned off, the second clamping circuit is forwardly turned on, the parasitic capacitance of the controlled end of the second switch circuit can be discharged through the second clamping circuit, and because the second clamping circuit is forwardly turned on, the voltage between the output end of the second driving circuit and the controlled end of the second driving circuit can be clamped at the second voltage, the second voltage being less than the voltage resistance value between the output end and the controlled end of the second driving circuit, so that the second driving circuit can be prevented from being damaged, so that the second driving circuit can have a longer service life, and further so that the self-driven synchronous rectification circuit can have a longer service life, and further so that the LLC resonant circuit can have a longer service life.

[0008] In some embodiments, the first clamping circuit includes a first clamping diode, a positive electrode of the first clamping diode being an input end of the first clamping circuit, and a negative electrode of the first clamping diode being an output end of the first clamping circuit; and / or, the second clamping circuit includes a second clamping diode, a positive electrode of the second clamping diode being an input end of the second clamping circuit, and a negative electrode of the second clamping diode being an output end of the second clamping circuit.

[0009] Based on the above embodiments, when the first switch circuit is off, the first clamping diode is forward biased, and the parasitic capacitance of the controlled end of the second switch circuit can be discharged through the first clamping diode; and since the first clamping diode is forward biased, the voltage between the output end of the first drive circuit and the controlled end is clamped to 0.7V, which is less than the withstand voltage between the output end and the controlled end of the first drive circuit, so that the first drive circuit can be prevented from being damaged, and the first drive circuit can have a longer service life.

[0010] When the second switch circuit is off, the second clamping diode is forward biased, and the parasitic capacitance of the controlled end of the second switch circuit can be discharged through the first clamping diode; and since the second clamping diode is forward biased, the voltage between the output end of the second drive circuit and the controlled end is clamped to 0.7V, which is less than the withstand voltage between the output end and the controlled end of the second drive circuit, so that the second drive circuit can be prevented from being damaged, and the second drive circuit can have a longer service life.

[0011] In some embodiments, the first switch circuit includes a first switch element and a first resistor, an input end of the first switch element being an input end of the first switch circuit, an output end of the first switch element being an output end of the first switch circuit, and a controlled end of the first switch element being a controlled end of the first switch circuit; a first end of the first resistor being connected to the controlled end of the first switch element, and a second end of the first resistor being connected to the input end of the first switch element.

[0012] Based on the above embodiment, when the same name end of the primary coil is the reverse pulse alternating current, the second end of the second secondary coil outputs a high level signal, and the first end of the first secondary coil outputs a low level signal, so that the first driving circuit can receive the high level signal, thereby outputting a conduction signal to the controlled end of the first switch element. When the controlled end of the first switch element receives the conduction signal, the input end and the output end of the first switch element are conducted, so that the first switch circuit is conducted, thereby enabling the power supply device to output direct current through the first power supply loop. The conduction signal output by the first driving circuit to the controlled end of the first switch element is divided by the first resistor, and then applied to the input end of the first switch element, so as to facilitate the conduction of the first switch element.

[0013] In some embodiments, the second switch circuit includes a second switch element and a second resistor, the input end of the second switch element is the input end of the second switch circuit, the output end of the second switch element is the output end of the second switch circuit, and the controlled end of the second switch element is the controlled end of the second switch circuit; the first end of the second resistor is connected with the controlled end of the second switch element, and the second end of the second resistor is connected with the input end of the second switch element.

[0014] Based on the above embodiment, when the same name end of the primary coil is the reverse pulse alternating current, the second end of the second secondary coil outputs a high level signal, and the first end of the first secondary coil outputs a low level signal, so that the first driving circuit can receive the high level signal, thereby outputting a conduction signal to the controlled end of the second switch element. When the controlled end of the second switch element receives the conduction signal, the input end and the output end of the second switch element are conducted, so that the second switch circuit is conducted, thereby enabling the power supply device to output direct current through the second power supply loop. The conduction signal output by the second driving circuit to the controlled end of the second switch element is divided by the second resistor, and then applied to the input end of the second switch element, so as to facilitate the conduction of the second switch element.

[0015] In some embodiments, the first driving circuit includes a first filter circuit, a first voltage stabilizing circuit and a first current limiting circuit, the input end of the first filter circuit is the input end of the first driving circuit; the input end of the first voltage stabilizing circuit is connected with the output end of the first filter circuit; the input end of the first current limiting circuit is connected with the output end of the first voltage stabilizing circuit, and the output end of the first current limiting circuit is the output end of the first driving circuit.

[0016] Based on the above embodiment, when the first driving circuit receives a high level signal, the first filter circuit can filter the high level signal to reduce the interference of noise signals on the first voltage stabilizing circuit, thereby improving the stability of the conduction signal output by the first voltage stabilizing circuit to the first switch element through the first current limiting circuit, and further improving the conduction stability of the first switch element, so as to stabilize the output voltage of the self-driven synchronous rectification circuit.

[0017] In some embodiments, the first filter circuit includes a first capacitor and a third resistor, a first substrate of the first capacitor is the input terminal of the first filter circuit, and a second substrate of the first capacitor is the output terminal of the first filter circuit; a first end of the third resistor is connected to the first pole plate of the first capacitor, and a second end of the third resistor is connected to the second end of the third resistor.

[0018] Based on the above embodiments, the first capacitor is used to filter out the direct current signal in the high-level signal, so as to improve the accuracy of the signal input to the input terminal of the first voltage stabilizing circuit. The third resistor is used to protect the first capacitor. When the voltage between the first substrate and the second substrate of the first capacitor exceeds the rated voltage of the first capacitor, the first capacitor can discharge through the third resistor, thereby reducing the probability of damage to the first capacitor, so that the first filter circuit can have a longer service life, and thus the first driving circuit can have a longer service life.

[0019] In some embodiments, the first voltage stabilizing circuit includes a third switching element, a fourth resistor, and a first voltage stabilizing element, an input terminal of the third switching element is the input terminal of the first voltage stabilizing circuit, and an output terminal of the third switching element is the output terminal of the first voltage stabilizing circuit; a first end of the fourth resistor is connected to the input terminal of the third switching element, and a second end of the fourth resistor is connected to the controlled terminal of the third switching element; a negative electrode of the first voltage stabilizing element is connected to the controlled terminal of the third switching element, and a positive electrode of the first voltage stabilizing element is grounded.

[0020] Based on the above embodiments, the high-voltage signal enters the controlled terminal of the third switching element after being filtered by the first filter circuit, so that the third switching element is turned on, thereby enabling the output terminal of the third switching element to output a conduction signal to the controlled terminal of the first switching element, so that the first switching element is turned on; the fourth resistor is used to limit the current and divide the voltage of the high-level signal entering the controlled terminal of the third switching element, so as to reduce the probability of damage to the third switching element; the first voltage stabilizing element can stabilize the voltage of the controlled terminal of the third switching element, thereby ensuring that the third switching element can be in the on state, so as to improve the conduction stability of the third switching element, and thus the conduction stability of the first switching element can be improved.

[0021] In some embodiments, the first current limiting circuit includes a fifth resistor, a first end of the fifth resistor is the input terminal of the first current limiting circuit, and a second end of the fifth resistor is the output terminal of the first current limiting circuit.

[0022] Based on the above embodiments, the fifth resistor can be used to limit the current entering the controlled terminal of the first switching element, so as to reduce the probability of damage to the first switching element, thereby enabling the first switching element to have a longer service life, enabling the self-driven synchronous rectification circuit to have a longer service life, and thus enabling the LLC resonant circuit to have a longer service life.

[0023] In some embodiments, the second driving circuit comprises a second filtering circuit, a second voltage stabilizing circuit and a second current limiting circuit, an input end of the second filtering circuit is the input end of the second driving circuit; an input end of the second voltage stabilizing circuit is connected with an output end of the second filtering circuit; an input end of the second current limiting circuit is connected with an output end of the second voltage stabilizing circuit, and an output end of the second current limiting circuit is the output end of the second driving circuit.

[0024] Based on the above-mentioned embodiments, when the second driving circuit receives a high-level signal, the second filtering circuit can filter the high-level signal to reduce the interference of noise signals on the second voltage stabilizing circuit, so as to improve the stability of the conduction signal output by the second voltage stabilizing circuit through the second current limiting circuit, and further improve the conduction stability of the second switching element, so as to stabilize the output voltage of the self-driven synchronous rectification circuit.

[0025] In some embodiments, the second filtering circuit comprises a second capacitor and a sixth resistor, a first substrate of the second capacitor is the input end of the second filtering circuit, and a second substrate of the second capacitor is the output end of the second filtering circuit; a first end of the sixth resistor is connected with a first pole plate of the second capacitor, and a second end of the sixth resistor is connected with a second pole plate of the second capacitor.

[0026] Based on the above-mentioned embodiments, the second capacitor is used to filter out the direct current signal in the high-level signal to improve the accuracy of the signal input to the input end of the second voltage stabilizing circuit. The sixth resistor is used to protect the second capacitor. When the voltage between the first substrate and the second substrate of the second capacitor exceeds the rated voltage of the second capacitor, the second capacitor can discharge through the sixth resistor, thereby reducing the probability of damage to the second capacitor, so that the second filtering circuit can have a longer service life, and further so that the second driving circuit can have a longer service life.

[0027] In some embodiments, the second voltage stabilizing circuit comprises a fourth switching element, a seventh resistor and a second voltage stabilizing element, an input end of the fourth switching element is the input end of the second filtering circuit, and an output end of the fourth switching element is the output end of the second filtering circuit; a first end of the seventh resistor is connected with the input end of the fourth switching element, and a second end of the seventh resistor is connected with a controlled end of the fourth switching element; a negative electrode of the second voltage stabilizing element is connected with the controlled end of the fourth switching element, and a positive electrode of the second voltage stabilizing element is grounded.

[0028] Based on the above embodiment, the high voltage signal is filtered by the second filter circuit and enters the control end of the fourth switch element, so that the fourth switch element is turned on, thereby enabling the output end of the fourth switch element to output a conduction signal to the control end of the second switch element, so that the second switch element is turned on; the seventh resistor is used to limit the current and divide the voltage of the high level signal entering the control end of the fourth switch element, so as to reduce the probability of damage to the fourth switch element; the second voltage stabilizing element can stabilize the voltage of the control end of the fourth switch element, thereby ensuring that the fourth switch element can be in an on state, so as to improve the conduction stability of the fourth switch element, and further improve the conduction stability of the second switch element.

[0029] In some embodiments, the second current limiting circuit includes an eighth resistor, a first end of the eighth resistor being an input end of the second current limiting circuit, and a second end of the eighth resistor being an output end of the second current limiting circuit.

[0030] Based on the above embodiment, the eighth resistor can be used to limit the current entering the control end of the second switch element, so as to reduce the probability of damage to the second switch element, thereby enabling the second switch element to have a longer service life, enabling the self-driven synchronous rectification circuit to have a longer service life, and further enabling the LLC resonant circuit to have a longer service life.

[0031] The embodiments of the present application also provide an LLC resonant circuit, which comprises a primary circuit, a primary coil, a first secondary coil, a second secondary coil and a self-driven synchronous rectification circuit, an input end of the primary circuit being used to access a direct current; the primary coil is connected with an output end of the primary circuit; the first secondary coil is coupled with the primary coil; the second secondary coil is coupled with the primary coil; the self-driven synchronous rectification circuit is connected with a first end of the first secondary coil and a second end of the second secondary coil, and an output end of the self-driven synchronous rectification circuit is connected with a second end of the first secondary coil and a first end of the second secondary coil.

[0032] Based on the above embodiment, when the same name end of the primary coil is an inverse pulse alternating current, the first end of the first secondary coil outputs a low level, and the second end of the second secondary coil outputs a high level signal, so that the first drive circuit can receive a high level signal, thereby sending a conduction signal to the control end of the first switch circuit to make the first switch circuit conductive, so that the second end of the first secondary coil can supply power to an external device through the output end of the self-driven synchronous rectification circuit, and form a first power supply loop via the first switch circuit and the first end of the first secondary coil. At this time, the second drive circuit receives a low level signal, and the second drive circuit remains in an off state.

[0033] When the same-named end of the primary coil is positive pulse alternating current, the first end of the first secondary coil outputs a high level signal, and the second end of the second secondary coil outputs a low level signal, so that the second driving circuit can receive a high level signal, thereby sending a conduction signal to the controlled end of the second switch circuit, so that the second switch circuit is turned on, so that the first end of the second secondary coil can supply power to an external device through the output end of the self-driven synchronous rectification circuit, and form a second power supply loop through the second switch circuit and the second end of the second secondary coil. At this time, the first driving circuit receives a low level signal, and the first driving circuit remains in an off state.

[0034] The above process is alternately executed, so that the LLC resonant circuit can output direct current to supply power to an external device.

[0035] The application also provides a power supply device, comprising a circuit board and an LLC resonant circuit, wherein the LLC resonant circuit is arranged on the circuit board.

[0036] Based on the self-driven synchronous rectification circuit of the application, when the first switch circuit is off, the first clamping circuit is forwardly turned on, the parasitic capacitance of the controlled end of the first switch circuit can be discharged through the first clamping circuit, and because the first clamping circuit is forwardly turned on, the voltage between the output end voltage of the first driving circuit and the controlled end of the first driving circuit can be clamped to a first voltage, and the first voltage is less than the withstand voltage between the output end and the controlled end of the first driving circuit, thereby preventing the first driving circuit from being damaged, so that the first driving circuit can have a longer service life, and further, the self-driven synchronous rectification circuit can have a longer service life, and the LLC resonant circuit can have a longer service life.

[0037] When the second switch circuit is off, the second clamping circuit is forwardly turned on, the parasitic capacitance of the controlled end of the second switch circuit can be discharged through the second clamping circuit, and because the second clamping circuit is forwardly turned on, the voltage between the output end voltage of the second driving circuit and the controlled end of the second driving circuit can be clamped to a second voltage, and the second voltage is less than the withstand voltage between the output end and the controlled end of the second driving circuit, thereby preventing the second driving circuit from being damaged, so that the second driving circuit can have a longer service life, and further, the self-driven synchronous rectification circuit can have a longer service life, and the LLC resonant circuit can have a longer service life. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0039] Figure 1 a schematic diagram of a LLC resonant circuit in an embodiment of the present application;

[0040] Figure 2 a specific schematic diagram of a LLC resonant circuit in an embodiment of the present application;

[0041] Figure 3 a schematic diagram of a LLC resonant circuit in an embodiment of the present application;

[0042] Figure 4 a schematic diagram of a LLC resonant circuit in an embodiment of the present application;

[0043] Figure 5 a specific schematic diagram of a LLC resonant circuit in an embodiment of the present application;

[0044] Figure 6 a schematic diagram of a LLC resonant circuit in an embodiment of the present application.

[0045] BRIEF DESCRIPTION OF DRAWINGS 1, LLC resonant circuit; 11, primary circuit; 12, self-driven synchronous rectification circuit; 121, first switching circuit; 122, second switching circuit; 123, first driving circuit; 1231, first filter circuit; 1232, first voltage stabilizing circuit; 1233, first current limiting circuit; 124, second driving circuit; 1241, second filter circuit; 1242, second voltage stabilizing circuit; 1243, second current limiting circuit; 125, first cut-off circuit; 126, second cut-off circuit; 127, first clamping circuit; 128, second clamping circuit; L1, primary coil; L21, first secondary coil; L22, second secondary coil; D1, first cut-off diode; D2, second cut-off diode; D3, first clamping diode; D4, second clamping diode; Q1, first switching element; Q2, second switching element; Q3, third switching element; Q4, fourth switching element; R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor; R7, seventh resistor; R8, eighth resistor; C1, first capacitor; C2, second capacitor; ZD1, first voltage stabilizing element; ZD2, second voltage stabilizing element. DETAILED DESCRIPTION

[0046] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0047] In the field of power supply design, LLC resonant circuit as a common design method is widely used in various power supplies. Among them, the LLC resonant circuit mainly includes a primary coil, a secondary coil, a switch tube and a driving circuit, and the most important feature is that the voltage at the high potential end of the secondary coil is used to drive the switch tube through the driving circuit, so that the low potential end of the secondary coil and the load are turned on to form a power supply loop.

[0048] The embodiment of the present application provides a power supply device (not shown in the figure), which comprises a circuit board (not shown in the figure) and an LLC resonant circuit 1.

[0049] The LLC resonant circuit 1 is used to convert alternating current into direct current output. The LLC resonant circuit 1 is arranged on the circuit board. Illustratively, the LLC resonant circuit 1 can be formed on the circuit board by etching process, so as to improve the manufacturing efficiency of the LLC resonant circuit 1, and also improve the production quality of the LLC resonant circuit 1.

[0050] Please refer to Figure 1 , the LLC resonant circuit 1 can include a primary circuit 11, a primary coil L1, a first secondary coil L21, a second secondary coil L22 and a self-driven synchronous rectification circuit 12.

[0051] The input end of the primary circuit 11 is used to access direct current, which can be obtained by rectifying alternating current, and the primary circuit 11 includes at least one of full-bridge resonant circuit and half-bridge resonant circuit. In the embodiment of the present application, the specific form of the primary circuit 11 is not limited.

[0052] The primary coil L1 is connected with the output end of the primary circuit 11, and the primary coil L1 is coupled with the first secondary coil L21 and the second secondary coil L22, so as to induce corresponding direction voltage on the first secondary coil L21 and the second secondary coil L22 according to the voltage direction change of the output end of the primary circuit 11.

[0053] The self-driven synchronous rectification circuit 12 is connected with the first end of the first secondary coil L21 and the second end of the second secondary coil L22, and the output end of the self-driven synchronous rectification circuit 12 is connected with the second end of the first secondary coil L21 and the first end of the second secondary coil L22. The self-driven synchronous rectification circuit 12 can rectify the voltage output by the first secondary coil L21 and the second secondary coil L22, so as to realize synchronous rectification of the oscillation signal, and reduce the power consumption of the power supply device as a whole, so as to improve the output efficiency of the power supply device.

[0054] Please refer to Figure 1 , the self-driven synchronous rectification circuit 12 includes a first switch circuit 121, a second switch circuit 122, a first driving circuit 123 and a second driving circuit 124.

[0055] The input end of the first switch circuit 121 is grounded, and the output end of the first switch circuit 121 is connected with the first end of the first secondary coil L21; the input end of the second switch circuit 122 is grounded, and the output end of the second switch circuit 122 is connected with the second end of the second secondary coil L22; the input end of the first drive circuit 123 is connected with the second end of the second secondary coil L22, and the output end of the first drive circuit 123 is connected with the controlled end of the first switch circuit 121; the input end of the second drive circuit 124 is connected with the first end of the first secondary coil L21, and the output end of the second drive circuit 124 is connected with the controlled end of the second switch circuit 122.

[0056] When the same end of the primary coil L1 is connected with the reverse pulse alternating current, the first end of the first secondary coil L21 outputs low level, and the second end of the second secondary coil L22 outputs high level signal, so that the first drive circuit 123 can receive high level signal, thereby sending the on signal to the controlled end of the first switch circuit 121, so that the first switch circuit 121 is turned on, so that the second end of the first secondary coil L21 can supply power to the external device through the output end of the self-driven synchronous rectifier circuit 12, and form the first power supply loop through the first switch circuit 121 and the first end of the first secondary coil L21. At this time, the second drive circuit 124 receives low level signal, and the second drive circuit 124 remains off state.

[0057] When the same end of the primary coil L1 is connected with the reverse pulse alternating current, the first end of the first secondary coil L21 outputs low level, and the second end of the second secondary coil L22 outputs high level signal, so that the first drive circuit 123 can receive high level signal, thereby sending the on signal to the controlled end of the first switch circuit 121, so that the first switch circuit 121 is turned on, so that the second end of the first secondary coil L21 can supply power to the external device through the output end of the self-driven synchronous rectifier circuit 12, and form the first power supply loop through the first switch circuit 121 and the first end of the first secondary coil L21. At this time, the second drive circuit 124 receives low level signal, and the second drive circuit 124 remains off state.

[0058] The above process is alternately executed, so that the LLC resonant circuit 1 can output direct current to supply power to the external device.

[0059] Please refer to Figures 1-3, specifically, the first switch circuit 121 includes a first switch element Q1 and a first resistor R1, an input end of the first switch element Q1 is an input end of the first switch circuit 121, an output end of the first switch element Q1 is an output end of the first switch circuit 121, a controlled end of the first switch element Q1 is a controlled end of the first switch circuit 121; a first end of the first resistor R1 is connected with the controlled end of the first switch element Q1, and a second end of the first resistor R1 is connected with the input end of the first switch element Q1. When a conduction signal is received at the controlled end of the first switch element Q1, the input end and the output end of the first switch element Q1 are turned on, so that the first switch circuit 121 is turned on, thereby enabling the power supply device to output direct current through the first power supply loop. The conduction signal output by the first drive circuit 123 to the controlled end of the first switch element Q1 is divided by the first resistor R1 and then applied to the input end of the first switch element Q1, so as to facilitate the conduction of the first switch element Q1.

[0060] It can be understood that the first switch element Q1 can be at least one of a field effect transistor (FET) and a bipolar junction transistor (BJT).

[0061] Please refer to Figures 1-3 , for example, the first switch element Q1 can be a field effect transistor. Specifically, the first switch element Q1 can be a first NMOS tube (N-Metal-Oxide-Semiconductor Field-Effect Transistor, N-type metal oxide semiconductor field effect transistor), the gate G of the first NMOS tube is the controlled end of the first switch element Q1, the source S of the first NMOS tube is the input end of the first switch element Q1, and the drain D of the first NMOS tube is the output end of the first switch element Q1. When a conduction signal is received at the gate G of the first NMOS tube, the conduction signal is high, and when the gate G voltage of the first NMOS tube is higher than the source S voltage of the first NMOS tube, the source S and the drain D of the first NMOS tube are turned on, so that the input end and the output end of the first switch element Q1 are turned on. When the gate G of the first NMOS tube receives an off signal, the off signal is low, and the source S and the drain D of the first NMOS tube are turned off. It can be understood that the first switch element Q1 can also be a PMOS tube (P-Metal-Oxide-Semiconductor Field-Effect Transistor, P-type metal oxide semiconductor field effect transistor), which will not be described in detail here.

[0062] Please refer to Figures 1-3Specifically, the second switch circuit 122 includes a second switch element Q2 and a second resistor R2. The input end of the second switch element Q2 is the input end of the second switch circuit 122, the output end of the second switch element Q2 is the output end of the second switch circuit 122, and the controlled end of the second switch element Q2 is the controlled end of the second switch circuit 122. The first end of the second resistor R2 is connected with the controlled end of the second switch element Q2, and the second end of the second resistor R2 is connected with the input end of the second switch element Q2. When the controlled end of the second switch element Q2 receives the conduction signal, the input end and the output end of the second switch element Q2 are turned on, so that the second switch circuit 122 is turned on, thereby enabling the power supply device to output direct current through the second power supply loop. The conduction signal output by the second drive circuit 124 to the controlled end of the second switch element Q2 is divided by the second resistor R2 and then applied to the input end of the second switch element Q2, so as to turn on the second switch element Q2.

[0063] It can be understood that the second switch element Q2 can also be at least one of a field effect tube and a triode.

[0064] Please refer to Figures 1-3 For example, the second switch element Q2 can be a field effect tube. Specifically, the second switch element Q2 can be a second NMOS tube, the gate G of the second NMOS tube is the controlled end of the second switch element Q2, the source S of the second NMOS tube is the input end of the second switch element Q2, and the drain D of the second NMOS tube is the output end of the second switch element Q2. When the gate G of the second NMOS tube receives the conduction signal, the conduction signal is high, and when the gate G voltage of the second NMOS tube is higher than the source S voltage of the second NMOS tube, the source S and the drain D of the second NMOS tube are turned on, so that the input end and the output end of the second switch element Q2 are turned on. When the gate G of the second NMOS tube is the off signal, the off signal is low, and the source S and the drain D of the second NMOS tube are turned off. It can be understood that the second switch element Q2 can also be a PMOS tube, which will not be described in detail here.

[0065] Since the controlled end of the first switch element Q1 and the controlled end of the second switch element Q2 both have parasitic capacitances, when the first switch element Q1 or the second switch element Q2 is turned off, the corresponding parasitic capacitances are slowly discharged, which is easy to cause the voltage borne by the corresponding drive circuit to exceed the withstand voltage value, resulting in damage to the drive circuit and affecting the service life of the self-driven synchronous rectification circuit.

[0066] Based on the above problems, please refer to Figure 1 and Figure 2In an embodiment, the self-driven synchronous rectification circuit 12 further comprises a first cut-off circuit 125 and a second cut-off circuit 126. The input end of the first cut-off circuit 125 is connected with the output end of the first driving circuit 123, and the output end of the first cut-off circuit 125 is connected with the controlled end of the first switch circuit 121, so as to cut off the voltage path from the controlled end of the first switch circuit 121 to the first driving circuit 123, thereby preventing the discharge voltage of the parasitic capacitance of the controlled end of the first switch element Q1 from being applied to the first driving circuit 123 when the first switch element Q1 is turned off, reducing the probability of damage of the first driving circuit 123, so that the first driving circuit 123 has a longer service life, and further so that the self-driven synchronous rectification circuit 12 has a longer service life, and so that the LLC resonant circuit 1 has a longer service life.

[0067] The input end of the second cut-off circuit 126 is connected with the output end of the second driving circuit 124, and the output end of the second cut-off circuit 126 is connected with the controlled end of the second switch circuit 122, so as to cut off the voltage path from the controlled end of the second switch circuit 122 to the second driving circuit 124, thereby preventing the discharge voltage of the parasitic capacitance of the controlled end of the second switch element Q2 from being applied to the second driving circuit 124 when the second switch element Q2 is turned off, reducing the probability of damage of the second driving circuit 124, so that the second driving circuit 124 has a longer service life, and further so that the self-driven synchronous rectification circuit 12 has a longer service life, and so that the LLC resonant circuit 1 has a longer service life.

[0068] Please refer to Figure 3 In particular, the first cut-off circuit 125 can comprise a first cut-off diode D1, the anode of the first cut-off diode D1 being the input end of the first cut-off circuit 125, and the cathode of the first cut-off diode D1 being the output end of the first cut-off circuit 125. When the first switch circuit 121 is turned off, the reverse cut-off of the first cut-off diode D1 is used to limit the voltage of the parasitic capacitance of the controlled end of the first switch circuit 121 from entering the first driving circuit 123, so as to prevent the voltage borne by the first driving circuit 123 from exceeding the withstand voltage value, thereby making the first driving circuit 123 have a longer service life, and further making the self-driven synchronous rectification circuit 12 have a longer service life.

[0069] Please refer to Figure 3, specifically, the second cut-off circuit 126 can include a second cut-off diode D2, the anode of the second cut-off diode D2 being the input terminal of the second cut-off circuit 126, and the cathode of the second cut-off diode D2 being the output terminal of the second cut-off circuit 126. When the second switch circuit 122 is off, the reverse cut-off of the second cut-off diode D2 can be used to limit the voltage of the parasitic capacitance of the controlled terminal of the second switch circuit 122 from entering the second drive circuit 124, so as to prevent the voltage borne by the second drive circuit 124 from exceeding the withstand voltage value, thereby enabling the second drive circuit 124 to have a longer service life, and enabling the self-driven synchronous rectification circuit 12 to have a longer service life.

[0070] Please refer to Figure 4 and Figure 5 In another embodiment, the self-driven synchronous rectification circuit 12 can further include a first clamping circuit 127 and a second clamping circuit 128. The input terminal of the first clamping circuit 127 is connected to the output terminal of the first drive circuit 123, and the output terminal of the first clamping circuit 127 is connected to the controlled terminal of the first drive circuit 123. When the first switch element Q1 is off, the first clamping circuit 127 is forward-biased, the parasitic capacitance of the controlled terminal of the first switch element Q1 can be discharged through the first clamping circuit 127, and due to the forward bias of the first clamping circuit 127, the voltage between the output terminal of the first drive circuit 123 and the controlled terminal of the first drive circuit 123 can be clamped to a first voltage, which is less than the withstand voltage value between the output terminal and the controlled terminal of the first drive circuit 123, thereby preventing the first drive circuit 123 from being damaged, enabling the first drive circuit 123 to have a longer service life, and further enabling the self-driven synchronous rectification circuit 12 to have a longer service life, and enabling the LLC resonant circuit 1 to have a longer service life.

[0071] The input terminal of the second clamping circuit 128 is connected to the output terminal of the second drive circuit 124, and the output terminal of the second clamping circuit 128 is connected to the controlled terminal of the second drive circuit 124. When the second switch element Q2 is off, the second clamping circuit 128 is forward-biased, the parasitic capacitance of the controlled terminal of the second switch element Q2 can be discharged through the second clamping circuit 128, and due to the forward bias of the second clamping circuit 128, the voltage between the output terminal of the second drive circuit 124 and the controlled terminal of the second drive circuit 124 can be clamped to a second voltage, which is less than the withstand voltage value between the output terminal and the controlled terminal of the second drive circuit 124, thereby preventing the second drive circuit 124 from being damaged, enabling the second drive circuit 124 to have a longer service life, and further enabling the self-driven synchronous rectification circuit 12 to have a longer service life, and enabling the LLC resonant circuit 1 to have a longer service life.

[0072] Please refer toFigure 6 Specifically, the first clamping circuit 127 includes a first clamping diode D3, a positive electrode of the first clamping diode D3 being an input end of the first clamping circuit 127, and a negative electrode of the first clamping diode D3 being an output end of the first clamping circuit 127. When the first switching element Q1 is off, the first clamping diode D3 is forward conducting, and the parasitic capacitance of the controlled end of the first switching element Q1 can be discharged through the first clamping diode D3. Since the first clamping diode D3 is forward conducting, the voltage between the output end of the first driving circuit 123 and the controlled end is clamped to 0.7V, which is less than the withstand voltage between the output end and the controlled end of the first driving circuit 123, so that the first driving circuit 123 can be prevented from being damaged, and the first driving circuit 123 can have a longer service life.

[0073] Please refer to Figure 6 Specifically, the second clamping circuit 128 includes a second clamping diode D4, a positive electrode of the second clamping diode D4 being an input end of the second clamping circuit 128, and a negative electrode of the second clamping diode D4 being an output end of the second clamping circuit 128. When the second switching element Q2 is off, the second clamping diode D4 is forward conducting, and the parasitic capacitance of the controlled end of the second switching element Q2 can be discharged through the first clamping diode D3. Since the second clamping diode D4 is forward conducting, the voltage between the output end of the second driving circuit 124 and the controlled end is clamped to 0.7V, which is less than the withstand voltage between the output end and the controlled end of the second driving circuit 124, so that the second driving circuit 124 can be prevented from being damaged, and the second driving circuit 124 can have a longer service life.

[0074] Please refer to Figure 3 and Figure 6In an embodiment, the first driving circuit 123 comprises a first filter circuit 1231, a first voltage stabilizing circuit 1232, and a first current limiting circuit 1233. The input end of the first filter circuit 1231 is the input end of the first driving circuit 123. The input end of the first voltage stabilizing circuit 1232 is connected with the output end of the first filter circuit 1231. The controlled end of the first voltage stabilizing circuit 1232 is the controlled end of the first driving circuit 123. The input end of the first current limiting circuit 1233 is connected with the output end of the first voltage stabilizing circuit 1232, and the output end of the first current limiting circuit 1233 is the output end of the first driving circuit 123. When the first driving circuit 123 receives a high-level signal, the first filter circuit 1231 can filter the high-level signal to reduce the interference of noise signals on the first voltage stabilizing circuit 1232, thereby improving the stability of the conduction signal output by the first voltage stabilizing circuit 1232 through the first current limiting circuit 1233, and further improving the conduction stability of the first switching element Q1, so as to stabilize the output voltage of the self-driven synchronous rectification circuit 12.

[0075] Please refer to Figure 3 and Figure 6 In an embodiment, the first filter circuit 1231 can comprise a first capacitor C1 and a third resistor R3. The first substrate of the first capacitor C1 is the input end of the first filter circuit 1231, and the second substrate of the first capacitor C1 is the output end of the first filter circuit 1231. The first capacitor C1 is used to filter out the direct current signal in the high-level signal, so as to improve the accuracy of the signal input to the input end of the first voltage stabilizing circuit 1232. The first end of the third resistor R3 is connected with the first plate of the first capacitor C1, and the second end of the third resistor R3 is connected with the second end of the third resistor R3. The third resistor R3 is used to protect the first capacitor C1. When the voltage between the first substrate and the second substrate of the first capacitor C1 exceeds the rated voltage of the first capacitor C1, the first capacitor C1 can be discharged through the third resistor R3, thereby reducing the probability of damage to the first capacitor C1, so that the first filter circuit 1231 can have a longer service life, and further so that the first driving circuit 123 can have a longer service life.

[0076] Please refer to Figure 3 and Figure 6In an embodiment, the first voltage stabilizing circuit 1232 comprises a third switching element Q3, a fourth resistor R4, and a first voltage stabilizing element ZD1. The input terminal of the third switching element Q3 is the input terminal of the first voltage stabilizing circuit 1232, and the output terminal of the third switching element Q3 is the output terminal of the first voltage stabilizing circuit 1232. The control terminal of the third switching element Q3 is the control terminal of the first voltage stabilizing circuit 1232. The first terminal of the fourth resistor R4 is connected to the input terminal of the third switching element Q3, and the second terminal of the fourth resistor R4 is connected to the control terminal of the third switching element Q3. The negative terminal of the first voltage stabilizing element ZD1 is connected to the control terminal of the third switching element Q3, and the positive terminal of the first voltage stabilizing element ZD1 is grounded.

[0077] The high voltage signal is filtered by the first filter circuit 1231 and then enters the control terminal of the third switching element Q3, so that the third switching element Q3 is turned on, thereby enabling the output terminal of the third switching element Q3 to output a conduction signal to the control terminal of the first switching element Q1, so that the first switching element Q1 is turned on. The fourth resistor R4 is used to limit the current and voltage of the high voltage signal entering the control terminal of the third switching element Q3, thereby reducing the probability of damage to the third switching element Q3. The first voltage stabilizing element ZD1 can stabilize the voltage at the control terminal of the third switching element Q3, thereby ensuring that the third switching element Q3 can be in the on state, thereby improving the conduction stability of the third switching element Q3, and further improving the conduction stability of the first switching element Q1.

[0078] It can be understood that the third switching element Q3 can be at least one of a field effect transistor, a triode, and an electromagnetic relay.

[0079] Please refer to Figure 3 and Figure 6 For example, the third switching element Q3 can be a triode. Specifically, the third switching element Q3 can be a first NPN triode, the base B of the first NPN triode is the control terminal of the third switching element Q3, the collector C of the first NPN triode is the input terminal of the third switching element Q3, and the emitter E of the first NPN triode is the output terminal of the third switching element Q3. When the same terminal of the primary coil L1 is a reverse pulse alternating current, the second end of the second secondary coil L22 outputs a high-level signal, so that the base B of the first NPN triode is high, thereby turning on the collector C and the emitter E of the first NPN triode, so that the input terminal and the output terminal of the third switching element Q3 are turned on, and a conduction signal is output to the control terminal of the first switching circuit 121. It can be understood that the third switching element Q3 can also be a PNP triode, which will not be described in detail here.

[0080] Please refer to Figure 3 and Figure 6For example, the first voltage stabilizing element ZD1 can be a first voltage stabilizing diode. When a high level signal is received at the controlled end of the third switch element Q3, the first voltage stabilizing diode is reversely broken down, so that the voltage at the controlled end of the third switch element Q3 is stabilized at the breakdown voltage of the first voltage stabilizing diode, and the voltage at the controlled end of the third switch element Q3 is stabilized, thereby ensuring that the third switch element Q3 can be in the on state, so as to improve the on stability of the third switch element Q3, and further improve the on stability of the first switch element Q1.

[0081] Please refer to Figure 3 and Figure 6 In an embodiment, the first current limiting circuit 1233 can include a fifth resistor R5, a first end of the fifth resistor R5 being an input end of the first current limiting circuit 1233, and a second end of the fifth resistor R5 being an output end of the first current limiting circuit 1233. The fifth resistor R5 can be used to limit the current entering the controlled end of the first switch element Q1, so as to reduce the probability of damage of the first switch element Q1, thereby prolonging the service life of the first switch element Q1, the self-driven synchronous rectification circuit 12, and the LLC resonant circuit 1.

[0082] Please refer to Figure 3 and Figure 6 In an embodiment, the second driving circuit 124 includes a second filtering circuit 1241, a second voltage stabilizing circuit 1242, and a second current limiting circuit 1243. An input end of the second filtering circuit 1241 is an input end of the second driving circuit 124. An input end of the second voltage stabilizing circuit 1242 is connected with an output end of the second filtering circuit 1241, and a controlled end of the second voltage stabilizing circuit 1242 is a controlled end of the second driving circuit 124. An input end of the second current limiting circuit 1243 is connected with an output end of the second voltage stabilizing circuit 1242, and an output end of the second current limiting circuit 1243 is an output end of the second driving circuit 124. When a high level signal is received by the second driving circuit 124, the second filtering circuit 1241 can filter the high level signal, so as to reduce the interference of noise signals on the second voltage stabilizing circuit 1242, thereby improving the stability of the on signal output by the second voltage stabilizing circuit 1242 to the second switch element through the second current limiting circuit 1243, and further improving the on stability of the second switch element Q2, so as to stabilize the output voltage of the self-driven synchronous rectification circuit 12.

[0083] Please refer to Figure 3 and Figure 6In an embodiment, the second filter circuit 1241 can include a second capacitor C2 and a sixth resistor R6. The first substrate of the second capacitor C2 is the input end of the second filter circuit 1241, and the second substrate of the second capacitor C2 is the output end of the second filter circuit 1241. The second capacitor C2 is used to filter out the direct current signal in the high-level signal, so as to improve the accuracy of the signal input to the input end of the second voltage stabilizing circuit 1242. The first end of the sixth resistor R6 is connected with the first pole plate of the second capacitor C2, and the second end of the sixth resistor R6 is connected with the second pole plate of the second capacitor C2. The sixth resistor R6 is used to protect the second capacitor C2. When the voltage between the first substrate and the second substrate of the second capacitor C2 exceeds the rated voltage of the second capacitor C2, the second capacitor C2 can be discharged through the sixth resistor R6, so as to reduce the probability of damage of the second capacitor C2, so that the second filter circuit 1241 can have a longer service life, and thus the second driving circuit 124 can have a longer service life.

[0084] Please refer to Figure 3 and Figure 6 In an embodiment, the second voltage stabilizing circuit 1242 includes a fourth switching element Q4, a seventh resistor R7, and a second voltage stabilizing element ZD2. The input end of the fourth switching element Q4 is the input end of the second filter circuit 1241, the output end of the fourth switching element Q4 is the output end of the second filter circuit 1241, and the controlled end of the fourth switching element Q4 is the controlled end of the second voltage stabilizing circuit 1242. The first end of the seventh resistor R7 is connected with the input end of the fourth switching element Q4, and the second end of the seventh resistor R7 is connected with the controlled end of the fourth switching element Q4. The negative electrode of the second voltage stabilizing element ZD2 is connected with the controlled end of the fourth switching element Q4, and the positive electrode of the second voltage stabilizing element ZD2 is grounded.

[0085] The high-voltage signal filtered by the second filter circuit 1241 enters the controlled end of the fourth switching element Q4, so that the fourth switching element Q4 is turned on, so that the output end of the fourth switching element Q4 can output a conduction signal to the controlled end of the second switching element Q2, so that the second switching element Q2 is turned on. The seventh resistor R7 is used to limit the current and voltage of the high-level signal entering the controlled end of the fourth switching element Q4, so as to reduce the probability of damage of the fourth switching element Q4. The second voltage stabilizing element ZD2 can stabilize the voltage of the controlled end of the fourth switching element Q4, so as to ensure that the fourth switching element Q4 can be in the on state, so as to improve the conduction stability of the fourth switching element Q4, and thus the conduction stability of the second switching element Q2 can be improved.

[0086] It can be understood that the fourth switching element Q4 can be at least one of a field effect tube, a triode, and an electromagnetic relay.

[0087] Please refer to Figure 3 andFigure 6 For example, the fourth switch element Q4 can be a triode. Specifically, the fourth switch element Q4 can be a second NPN triode, the base B of the second NPN triode is the controlled end of the fourth switch element Q4, the collector C of the second NPN triode is the input end of the fourth switch element Q4, and the emitter E of the second NPN triode is the output end of the fourth switch element Q4. When the same end of the primary coil L1 is a positive pulse alternating current, the second end of the first secondary coil L21 outputs a high level signal, so that the base B of the second NPN triode is high level, so that the collector C and the emitter E of the second NPN triode are turned on, so that the input end and the output end of the fourth switch element Q4 are turned on, and then the controlled end of the second switch circuit 122 outputs a conduction signal. It can be understood that the fourth switch element Q4 can also be a PNP triode, which will not be described in detail here.

[0088] Please refer to Figure 3 and Figure 6 For example, the second voltage stabilizing element ZD2 can be a second voltage stabilizing diode. When the controlled end of the fourth switch element Q4 receives a high level signal, the second voltage stabilizing diode is reversely broken down, so that the voltage of the controlled end of the fourth switch element Q4 is stabilized at the breakdown voltage of the second voltage stabilizing diode, so that the voltage of the controlled end of the fourth switch element Q4 is stabilized, thereby ensuring that the fourth switch element Q4 can be in the on state, thereby improving the conduction stability of the fourth switch element Q4, and further improving the conduction stability of the second switch element Q2.

[0089] Please refer to Figure 3 and Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure 6 Figure 3 Figure In an embodiment, the second current limiting circuit 1243 can include an eighth resistor R8, the first end of the eighth resistor R8 is the input end of the second current limiting circuit 1243, and the second end of the eighth resistor R8 is the output end of the second current limiting circuit 1243. The eighth resistor R8 can be used to limit the current entering the controlled end of the second switch element Q2, thereby reducing the probability of damage to the second switch element Q2, so that the second switch element Q2 can have a longer service life, so that the self-driven synchronous rectifier circuit 12 can have a longer service life, and further so that the LLC resonant circuit 1 has a longer service life.

[0090] The same or similar reference numerals in the drawings of the embodiments correspond to the same or similar components; in the description of the present application, it is understood that if the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right" and the like are based on the orientations or positional relationships shown in the drawings, they are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationships in the drawings are only used for exemplary illustration, and cannot be understood as a limitation on the present patent, for those skilled in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0091] The above is only a preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A self-driven synchronous rectification circuit, characterized by comprising: The application is suitable for LLC resonant circuit, the LLC resonant circuit includes first secondary coil, second secondary coil and self-driven synchronous rectification circuit, the output end of the self-driven synchronous rectification circuit is connected with the second end of the first secondary coil and the first end of the second secondary coil, the self-driven synchronous rectification circuit includes: First switch circuit, the input end of the first switch circuit is grounded, the output end of the first switch circuit is used for being connected with the first end of the first secondary coil; Second switch circuit, the input end of the second switch circuit is grounded, the output end of the second switch circuit is used for being connected with the second end of the second secondary coil; First drive circuit, the input end of the first drive circuit is used for being connected with the second end of the second secondary coil, the output end of the first drive circuit is connected with the controlled end of the first switch circuit; Second drive circuit, the input end of the second drive circuit is used for being connected with the first end of the first secondary coil, the output end of the second drive circuit is connected with the controlled end of the second switch circuit; First clamping circuit, the input end of the first clamping circuit is connected with the output end of the first drive circuit, the output end of the first clamping circuit is connected with the controlled end of the first drive circuit, so that the output end voltage of the first drive circuit and the controlled end voltage of the first drive circuit are clamped at the first voltage when the first clamping circuit is turned on; Second clamping circuit, the input end of the second clamping circuit is connected with the output end of the second drive circuit, the output end of the second clamping circuit is connected with the controlled end of the second drive circuit, so that the output end voltage of the second drive circuit and the controlled end voltage of the second drive circuit are clamped at the second voltage when the second clamping circuit is turned on.

2. The self-driven synchronous rectification circuit of claim 1, wherein: The first clamping circuit includes: A first clamping diode, the anode of the first clamping diode is the input end of the first clamping circuit, and the cathode of the first clamping diode is the output end of the first clamping circuit; and / or, The second clamping circuit includes: A second clamping diode, the anode of the second clamping diode is the input end of the second clamping circuit, and the cathode of the second clamping diode is the output end of the second clamping circuit.

3. The self-driven synchronous rectification circuit of claim 1, wherein: The first switch circuit includes: A first switch element, the input end of the first switch element is the input end of the first switch circuit, the output end of the first switch element is the output end of the first switch circuit, and the controlled end of the first switch element is the controlled end of the first switch circuit; A first resistor, the first end of the first resistor is connected with the controlled end of the first switch element, and the second end of the first resistor is connected with the input end of the first switch element; and / or, The second switch circuit includes: A second switch element, the input end of the second switch element is the input end of the second switch circuit, the output end of the second switch element is the output end of the second switch circuit, and the controlled end of the second switch element is the controlled end of the second switch circuit; A second resistor, the first end of the second resistor is connected with the controlled end of the second switch element, and the second end of the second resistor is connected with the input end of the second switch element. A second switch element, an input end of the second switch element being an input end of the second switch circuit, an output end of the second switch element being an output end of the second switch circuit, and a controlled end of the second switch element being a controlled end of the second switch circuit; A second resistor, a first end of the second resistor being connected with the controlled end of the second switch element, and a second end of the second resistor being connected with the input end of the second switch element.

4. The self-driven synchronous rectification circuit of claim 1, wherein, The first driving circuit comprises: A first filter circuit, an input end of the first filter circuit being an input end of the first driving circuit; A first voltage stabilizing circuit, an input end of the first voltage stabilizing circuit being connected with an output end of the first filter circuit, and a controlled end of the first voltage stabilizing circuit being a controlled end of the first driving circuit; A first current limiting circuit, an input end of the first current limiting circuit being connected with an output end of the first voltage stabilizing circuit, and an output end of the first current limiting circuit being an output end of the first driving circuit.

5. The self-driven synchronous rectification circuit of claim 4, wherein, The first filter circuit comprises: A first capacitor, a first substrate of the first capacitor being an input end of the first filter circuit, and a second substrate of the first capacitor being an output end of the first filter circuit; A third resistor, a first end of the third resistor being connected with a first pole plate of the first capacitor, and a second end of the third resistor being connected with a second end of the third resistor.

6. The self-driven synchronous rectification circuit of claim 4, wherein, The first voltage stabilizing circuit comprises: A third switch element, an input end of the third switch element being an input end of the first voltage stabilizing circuit, an output end of the third switch element being an output end of the first voltage stabilizing circuit, and a controlled end of the third switch element being a controlled end of the first voltage stabilizing circuit; A fourth resistor, a first end of the fourth resistor being connected with the input end of the third switch element, and a second end of the fourth resistor being connected with the controlled end of the third switch element; A first voltage stabilizing element, a negative electrode of the first voltage stabilizing element being connected with the controlled end of the third switch element, and a positive electrode of the first voltage stabilizing element being grounded.

7. The self-driven synchronous rectification circuit of claim 4, wherein, The first current limiting circuit comprises: A fifth resistor, a first end of the fifth resistor being an input end of the first current limiting circuit, and a second end of the fifth resistor being an output end of the first current limiting circuit.

8. The self-driven synchronous rectification circuit of claim 1, wherein, The second driving circuit comprises: A second filter circuit, an input end of the second filter circuit being an input end of the second driving circuit; A second voltage stabilizing circuit, an input end of the second voltage stabilizing circuit being connected with an output end of the second filter circuit, and a controlled end of the second voltage stabilizing circuit being connected with a controlled end of the second driving circuit; A second current limiting circuit, an input end of the second current limiting circuit being connected with an output end of the second voltage stabilizing circuit, and an output end of the second current limiting circuit being an output end of the second driving circuit.

9. The self-driven synchronous rectification circuit of claim 8, wherein, The second filter circuit comprises: A second capacitor, a first substrate of the second capacitor being an input end of the second filter circuit, and a second substrate of the second capacitor being an output end of the second filter circuit; A sixth resistor, a first end of the sixth resistor being connected with a first pole plate of the second capacitor, and a second end of the sixth resistor being connected with a second pole plate of the second capacitor.

10. The self-driven synchronous rectification circuit of claim 8, wherein, The second voltage stabilizing circuit comprises: A fourth switch element, an input end of the fourth switch element being an input end of the second filter circuit, an output end of the fourth switch element being an output end of the second filter circuit, a controlled end of the fourth switch element being a controlled end of the second voltage stabilizing circuit; A seventh resistor, a first end of the seventh resistor being connected with the input end of the fourth switch element, a second end of the seventh resistor being connected with the controlled end of the fourth switch element; A second voltage stabilizing element, a negative electrode of the second voltage stabilizing element being connected with the controlled end of the fourth switch element, a positive electrode of the second voltage stabilizing element being grounded.

11. The self-driven synchronous rectification circuit of claim 8, wherein the first and second transistors are configured to operate as a pair of complementary transistors. The second current limiting circuit comprises: An eighth resistor, a first end of the eighth resistor being an input end of the second current limiting circuit, a second end of the eighth resistor being an output end of the second current limiting circuit.

12. An LLC resonant circuit characterized by, Comprise: A primary circuit, an input end of the primary circuit being used for accessing an alternating current; A primary coil, connected with an output end of the primary circuit; A first secondary coil, coupled with the primary coil; A second secondary coil, coupled with the primary coil; A self-driven synchronous rectification circuit as claimed in any one of claims 1 to 11, connected with a first end of the first secondary coil and a second end of the second secondary coil, an output end of the self-driven synchronous rectification circuit being connected with a second end of the first secondary coil and a first end of the second secondary coil.

13. A power supply device, characterized by comprising: Comprise: A circuit board; The LLC resonant circuit as claimed in claim 12, arranged on the circuit board.

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