Synchronous rectification controller, method, power supply, chip, control circuit and equipment

Abstract

The invention provides a synchronous rectification controller, a control method, a switching power supply, a chip, a control circuit and electronic equipment. When the indication signal indicates that the power supply voltage is not established, the first control circuit transmits a first control signal to the charging circuit, the driving signal output circuit and the second control circuit. The charging circuit charges the control end of the low-side power transistor and the second control circuit according to the first control signal. The second control circuit transmits a second control signal to the driving signal output circuit according to the first control signal. The driving signal output circuit stops transmitting the turn-off signal to the driving circuit according to the first control signal, and stops transmitting the turn-on signal to the driving circuit according to the second control signal. The driving circuit clamps the voltage of the control end of the rectification transistor to a preset voltage by using the turned-on low-side power transistor. The driving circuit multiplexes the low-side power transistor, so that the synchronous rectification controller does not need to additionally add a clamping tube, and the area of the synchronous rectification controller is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of power management chips, and in particular to a synchronous rectification controller, a control method, a switching power supply, a chip, a control circuit and an electronic device. Background Art

[0002] With the development of power electronics technology, high efficiency and small size of switching power supplies have become a trend. Under this trend, synchronous rectification technology for improving power conversion efficiency is widely used in switching power supplies such as AC-DC converters and DC-DC converters. Synchronous rectification technology usually uses diodes as rectifiers. Due to the large forward voltage drop of the diode, the power loss of the rectifier is significant in high current applications. Therefore, synchronous rectification technology uses rectifier transistors MOSFET instead of diodes as rectifiers. The on-resistance of the rectifier transistor MOSFET is low, which can significantly reduce the power loss of the rectifier. Especially in low voltage and high current applications, the advantages of using rectifier transistors MOSFET as rectifiers are more obvious.

[0003] However, when the switching power supply is in the startup phase, when the synchronous rectification controller in the switching power supply is in the process of triggering the undervoltage protection UVLO of the power supply voltage, the power supply voltage of the synchronous rectification controller is not established, resulting in the synchronous rectification controller being unable to control the rectifier transistor MOSFET. Therefore, the synchronous rectification controller needs to clamp the gate terminal Gate of the rectifier transistor MOSFET to prevent the rectifier transistor MOSFET from being turned on by mistake. Thus, the risk of mutual communication between the primary and secondary sides of the switching power supply can be avoided.

[0004] In the related art, before the power supply voltage is established, the synchronous rectification controller needs to add an additional clamping tube to clamp the gate of the rectifier transistor MOSFET to prevent the rectifier transistor MOSFET from being turned on by mistake. Moreover, in order to achieve a better clamping effect, a clamping tube with a small impedance and high voltage is often used, resulting in a larger area of ​​the synchronous rectification controller. Summary of the invention

[0005] The present application provides a synchronous rectification controller, a control method, a switching power supply, a chip, a control circuit and an electronic device, which can reduce the area of ​​the synchronous rectification controller.

[0006] In a first aspect, the present application provides a synchronous rectification controller, which is applied to a switching power supply, wherein the switching power supply comprises: a rectification transistor; the synchronous rectification controller comprises: a charging circuit, a drive signal output circuit, a first control circuit, a second control circuit and a drive circuit;

[0007] The input end of the first control circuit is used to access an indication signal, and the indication signal is used to indicate the establishment of the power supply voltage of the synchronous rectification controller. The output end of the first control circuit is electrically connected to the control end of the charging circuit, the first end of the drive signal output circuit and the first end of the second control circuit respectively. The input end of the charging circuit is electrically connected to the drain end of the rectifier transistor. The first output end of the charging circuit and the output end of the drive signal output circuit are both electrically connected to the input end of the drive circuit. The output end of the drive circuit is electrically connected to the gate end of the rectifier transistor. The second output end of the charging circuit is electrically connected to the second end of the second control circuit. The output end of the second control circuit is electrically connected to the second end of the drive signal output circuit.

[0008] The first control circuit is used to transmit a first control signal to the charging circuit, the drive signal output circuit and the second control circuit respectively when the indication signal indicates that the power supply voltage is not established, and the first control signal is used to instruct the drive circuit to turn on the clamping function;

[0009] The charging circuit is used to charge the control terminal of the low-side power transistor in the driving circuit according to the first control signal to turn on the low-side power transistor, and to charge the second control circuit to make the second control circuit generate a second control signal, wherein the second control signal is used to control the driving signal output circuit to stop outputting the conduction signal, and the conduction signal is used to drive the rectifier transistor to turn on;

[0010] The second control circuit is used to transmit the second control signal to the drive signal output circuit;

[0011] The drive signal output circuit is used to stop transmitting the shutdown signal to the drive circuit according to the first control signal, and to stop transmitting the on signal to the drive circuit according to the second control signal, wherein the shutdown signal is used to drive the rectifier transistor to turn off so that the drive circuit turns on the clamping function;

[0012] The driving circuit is used to clamp the voltage of the control terminal of the rectifier transistor to a preset voltage by using the turned-on low-side power transistor after the clamping function is turned on.

[0013] By the synchronous rectification controller provided by the first aspect, when the indication signal indicates that the power supply voltage is not established, the first control circuit can transmit the first control signal for instructing the driving circuit to turn on the clamping function to the charging circuit, the driving signal output circuit and the second control circuit respectively. The charging circuit can charge the control end of the low-side power transistor in the driving circuit according to the first control signal to turn on the low-side power transistor. In addition, the charging circuit can charge the second control circuit so that the second control circuit generates a second control signal for controlling the driving signal output circuit to stop outputting the conduction signal. Among them, the conduction signal is used to drive the rectifier transistor to turn on. The second control circuit transmits the second control signal to the driving signal output circuit. The driving signal output circuit can stop transmitting the shutdown signal for driving the rectifier transistor to turn off to the driving circuit according to the first control signal, and stop transmitting the conduction signal to the driving circuit according to the second control signal, so that the driving circuit turns on the clamping function. In this way, after turning on the clamping function, the driving circuit uses the turned-on low-side power transistor to clamp the voltage of the control end of the rectifier transistor to a preset voltage. Since the driving circuit can reuse the low-side power transistor to clamp the voltage of the control terminal of the rectifier transistor, the synchronous rectifier controller does not need to add an additional clamping transistor, thereby reducing the area of ​​the synchronous rectifier controller.

[0014] In a possible design, the first control circuit is further configured to transmit a third control signal to the charging circuit, the drive signal output circuit and the second control circuit respectively when the indication signal indicates that the power supply voltage has been established, and the third control signal is used to instruct the drive circuit to turn off the clamping function;

[0015] The charging circuit is further used to stop charging the control terminal of the low-side power transistor according to the third control signal, so that the drive circuit turns off the clamping function, and stop charging the second control circuit, so that the second control circuit generates a fourth control signal, and the fourth control signal is used to control the drive signal output circuit to output the conduction signal;

[0016] The second control circuit is further configured to transmit the fourth control signal to the drive signal output circuit;

[0017] The drive signal output circuit is further configured to transmit the shutdown signal to the drive circuit according to the third control signal, and transmit the on signal to the drive circuit according to the fourth control signal;

[0018] The driving circuit is used for driving the rectifying transistor to be turned off according to the turn-off signal after the clamping function is turned off, and driving the rectifying transistor to be turned on according to the turn-on signal.

[0019] In a possible design, the first control circuit includes: a first resistor, a second resistor, a first switch tube, a first capacitor and a first voltage-controlled voltage source;

[0020] The first end of the first resistor is used to access the power supply voltage, the second end of the first resistor is electrically connected to the first end of the first switch tube, the control end of the first switch tube is used to access the indication signal, the second end of the first switch tube is electrically connected to the first end of the second resistor, the upper plate of the first capacitor and the input end of the first voltage-controlled voltage source are both electrically connected between the second end of the first switch tube and the first end of the second resistor, the output end of the first voltage-controlled voltage source is electrically connected to the control end of the charging circuit, and the second end of the second resistor and the lower plate of the first capacitor are both grounded;

[0021] The first voltage-controlled voltage source is used to amplify the first voltage on the first capacitor to obtain an amplified first amplified voltage, so that the first control circuit uses the amplified first amplified voltage as the first control signal or the third control signal.

[0022] In a possible design, the second control circuit includes: a second capacitor, a second switch tube, and a second voltage-controlled voltage source;

[0023] The upper plate of the second capacitor is electrically connected to the second output terminal of the charging circuit, the first terminal of the second switch tube and the input terminal of the second voltage-controlled voltage source are both electrically connected between the upper plate of the second capacitor and the second output terminal of the charging circuit, the control terminal of the second switch tube is electrically connected to the output terminal of the first control circuit, the output terminal of the second voltage-controlled voltage source is electrically connected to the second terminal of the drive signal output circuit, and the lower plate of the second capacitor and the second terminal of the second switch tube are both grounded;

[0024] The second voltage-controlled voltage source is used to amplify the second voltage on the second capacitor to obtain an amplified second amplified voltage, so that the second control circuit uses the amplified second amplified voltage as the second control signal or the fourth control signal.

[0025] In a possible design, the driving signal output circuit includes: a first driver, a second driver, a third switch tube and a selection output circuit;

[0026] The power supply end of the first driver, the power supply end of the second driver and the power supply end of the selection output circuit are all used to access the power supply voltage, the output end of the first driver is electrically connected to the first input end of the selection output circuit, the output end of the second driver is electrically connected to the second input end of the selection output circuit, the output end of the selection output circuit is electrically connected to the input end of the drive circuit, the first end of the third switch tube is electrically connected between the output end of the second driver and the second input end of the selection output circuit, the control end of the third switch tube is electrically connected to the output end of the second control circuit, the first end of the selection output circuit is electrically connected to the output end of the first control circuit, and the ground end of the first driver, the ground end of the second driver and the second end of the third switch tube are all grounded;

[0027] The first driver is used to transmit the shutdown signal to the selection output circuit;

[0028] The second driver is used to transmit the conduction signal to the selection output circuit;

[0029] The third switch tube is used to be turned off according to the second control signal; or turned on according to the fourth control signal;

[0030] The selection output circuit is used to stop outputting the shutdown signal according to the first control signal, and to stop outputting the conduction signal under the action of the shut-down third switch tube; or to output the shutdown signal according to the third control signal, and to output the conduction signal under the action of the conduction third switch tube.

[0031] In a possible design, the selection output circuit includes: a fourth switch tube, a fifth switch tube, a sixth switch tube and a first diode;

[0032] The first end of the fourth switch tube is used to connect to the power supply voltage, the control end of the fourth switch tube is electrically connected to the output end of the first driver, the second end of the fourth switch tube is electrically connected to the positive electrode of the first diode, the negative electrode of the first diode is electrically connected to the first end of the fifth switch tube, the control end of the fifth switch tube is electrically connected to the output end of the second driver, the sixth switch tube is connected in parallel with the first diode, the control end of the sixth switch tube is electrically connected to the output end of the first control circuit, the input end of the drive circuit is electrically connected between the negative electrode of the first diode and the first end of the fifth switch tube, and the second end of the fifth switch tube is grounded.

[0033] In a possible design, the charging circuit includes: a field effect transistor, a seventh switch tube, a third resistor, a second diode and a third diode;

[0034] The first end of the field effect transistor is electrically connected to the drain end of the rectifier transistor, the control end of the field effect transistor is grounded, the second end of the field effect transistor is electrically connected to the first end of the third resistor, the second end of the third resistor is electrically connected to the anode of the second diode, the cathode of the second diode is electrically connected to the input end of the drive circuit, the anode of the third diode and the first end of the seventh switch tube are both electrically connected between the second end of the third resistor and the anode of the second diode, the cathode of the third diode is electrically connected to the second end of the second control circuit, the control end of the seventh switch tube is electrically connected to the output end of the first control circuit, and the second end of the seventh switch tube is grounded.

[0035] In one possible design, the driving circuit includes: a high-side power transistor, a low-side power transistor, and a level-reversing circuit;

[0036] The first end of the high-side power transistor is used to access the power supply voltage, the control end of the high-side power transistor is electrically connected to the output end of the level reversal circuit, the second end of the high-side power transistor is electrically connected to the first end of the low-side power transistor, the gate end of the rectifier transistor is electrically connected between the second end of the high-side power transistor and the first end of the low-side power transistor, the control end of the low-side power transistor is electrically connected to the first output end of the charging circuit, the input end of the level reversal circuit is electrically connected between the control end of the low-side power transistor and the first output end of the charging circuit, and the second end of the low-side power transistor is grounded;

[0037] The level inversion circuit is used to change the state of the level of the control terminal of the low-side power transistor to turn on or off the high-side power transistor.

[0038] In a possible design, the driving circuit further includes: a voltage stabilizing diode;

[0039] The cathode of the voltage stabilizing diode is electrically connected between the control terminal of the low-side power transistor and the first output terminal of the charging circuit, and the anode of the voltage stabilizing diode is grounded.

[0040] In a possible design, the level inversion circuit includes: a NOT gate module and a level conversion module;

[0041] The input end of the NOT gate module is electrically connected between the control end of the low-side power transistor and the first output end of the charging circuit, the output end of the NOT gate module is electrically connected to the input end of the level conversion module, and the output end of the level conversion module is electrically connected to the control end of the high-side power transistor;

[0042] The NOT gate module is used to change the state of the level of the control end of the low-side power transistor to obtain a first level, and transmit the first level to the level conversion module;

[0043] The level conversion module is used to enhance the driving strength of the first level to turn on or off the high-side power transistor.

[0044] In a second aspect, the present application provides a synchronous rectification control method, which is performed by a synchronous rectification controller in the above-mentioned first aspect and each possible design of the above-mentioned first aspect, wherein the synchronous rectification controller is applied to a switching power supply, wherein the switching power supply comprises: a rectifier transistor; the synchronous rectification controller comprises: a charging circuit, a drive signal output circuit, a first control circuit, a second control circuit and a drive circuit, wherein the output end of the first control circuit is electrically connected to the control end of the charging circuit, the first end of the drive signal output circuit and the first end of the second control circuit respectively, the input end of the charging circuit is electrically connected to the drain end of the rectifier transistor, the first output end of the charging circuit and the output end of the drive signal output circuit are both electrically connected to the input end of the drive circuit, the output end of the drive circuit is electrically connected to the gate end of the rectifier transistor, the second output end of the charging circuit is electrically connected to the second end of the second control circuit, and the output end of the second control circuit is electrically connected to the second end of the drive signal output circuit; the method comprises:

[0045] The input end of the first control circuit receives an indication signal, and the indication signal is used to indicate the establishment of the power supply voltage of the synchronous rectification controller; when the indication signal indicates that the power supply voltage is not established, the first control circuit transmits a first control signal to the charging circuit, the drive signal output circuit and the second control circuit respectively, and the first control signal is used to instruct the drive circuit to turn on the clamping function;

[0046] The charging circuit charges the control terminal of the low-side power transistor in the driving circuit according to the first control signal to turn on the low-side power transistor, and charges the second control circuit to make the second control circuit generate a second control signal, wherein the second control signal is used to control the driving signal output circuit to stop outputting the conduction signal, and the conduction signal is used to drive the rectifier transistor to turn on;

[0047] The second control circuit transmits the second control signal to the drive signal output circuit;

[0048] The drive signal output circuit stops transmitting the shutdown signal to the drive circuit according to the first control signal, and stops transmitting the on signal to the drive circuit according to the second control signal, wherein the shutdown signal is used to drive the rectifier transistor to turn off so that the drive circuit turns on the clamping function;

[0049] After the clamping function is turned on, the driving circuit uses the turned-on low-side power tube transistor to clamp the voltage of the control end of the rectifier transistor to a preset voltage.

[0050] In a possible design, when the indication signal indicates that the power supply voltage has been established, the first control circuit transmits a third control signal to the charging circuit, the drive signal output circuit and the second control circuit respectively, wherein the third control signal is used to instruct the drive circuit to turn off the clamping function;

[0051] The charging circuit stops charging the control terminal of the low-side power transistor according to the third control signal, so that the drive circuit turns off the clamping function, and stops charging the second control circuit, so that the second control circuit generates a fourth control signal, and the fourth control signal is used to control the drive signal output circuit to output the conduction signal;

[0052] The second control circuit transmits the fourth control signal to the drive signal output circuit;

[0053] The drive signal output circuit transmits the shutdown signal to the drive circuit according to the third control signal, and transmits the on signal to the drive circuit according to the fourth control signal;

[0054] After turning off the clamping function, the driving circuit drives the rectifying transistor to turn off according to the shut-down signal, and drives the rectifying transistor to turn on according to the turn-on signal.

[0055] The beneficial effects of the methods provided in the above-mentioned second aspect and each possible design of the above-mentioned second aspect can be referred to the beneficial effects brought about by the above-mentioned first aspect and each possible implementation method of the first aspect, and will not be repeated here.

[0056] In a third aspect, the present application provides a switching power supply, comprising: a transformer, a rectifier transistor, an output capacitor, and a synchronous rectifier controller in the first aspect and each possible design of the first aspect;

[0057] The like-name end of the secondary winding of the transformer is electrically connected to the upper plate of the output capacitor, the opposite-name end of the secondary winding of the transformer is electrically connected to the drain end of the rectifier transistor and the power supply end of the synchronous rectifier controller respectively, the gate end of the rectifier transistor is electrically connected to the output end of the synchronous rectifier controller, and the ground end of the synchronous rectifier controller, the source end of the rectifier transistor and the lower plate of the output capacitor are all grounded.

[0058] In a fourth aspect, the present application provides a control circuit. The control circuit includes a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the steps of the method provided in the second aspect and each possible design of the second aspect are implemented.

[0059] In a fifth aspect, the present application provides a chip comprising any one of the following: the synchronous rectification controller in the first aspect and each possible design of the first aspect, the switching power supply in the third aspect and the control circuit in the fourth aspect.

[0060] In a sixth aspect, the present application provides an electronic device, comprising: the chip in the fifth aspect above.

[0061] The above description is only an overview of the technical solution of the embodiment of the present application. In order to more clearly understand the technical means of the embodiment of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions of the embodiments of the present application, a brief introduction will be given below to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0063] Figure 1 It is a structural diagram of a synchronous rectification controller in the related art;

[0064] Figure 2 A schematic diagram of the structure of a switching power supply provided in one embodiment of the present application;

[0065] Figure 3 A schematic diagram of the structure of a synchronous rectification controller provided in one embodiment of the present application;

[0066] Figure 4 A schematic flow chart of a synchronous rectification control method provided in one embodiment of the present application;

[0067] Figure 5 A working timing diagram of a synchronous rectification controller provided in one embodiment of the present application;

[0068] Figure 6 A control principle diagram of a synchronous rectification controller provided in an embodiment of the present application with the clamping function turned on;

[0069] Figure 7 A schematic diagram of a control method of a synchronous rectification controller under a shutdown clamping function provided in one embodiment of the present application. DETAILED DESCRIPTION

[0070] In this application, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c alone can represent: a, b, c, a and b, a and c, or a, b, and c, where a, b, and c can be single or multiple. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0071] The directions or positional relationships indicated by terms such as "center", "longitudinal", "lateral", "up", "down", "left", "right", "front", and "back" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0072] The terms "connected" and "connected" should be understood in a broad sense. For example, the "connected" or "connected" of a circuit structure can refer to not only physical connection, but also electrical connection or signal connection. For example, it can be directly connected, that is, physically connected, or indirectly connected through at least one intermediate element, as long as the circuit is connected, or it can be the internal connection of two elements; signal connection can refer to signal connection through a circuit or through a media medium, such as radio waves. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0073] Reference Figure 1 , Figure 1FIG. 1 is a schematic diagram of the structure of a synchronous rectification controller in the related art. Figure 1 As shown, the synchronous rectification controller in the related art may include: a transistor J1', a resistor R1', a diode D1', a switch S1', a switch S2', a switch S3', a driver U1', a driver U2', a NOT gate U3', a level converter U4', an upper tube M1', a lower tube M2' and a clamp tube M3'.

[0074] The first end of the transistor J1 ′ is electrically connected to the drain of the rectifying transistor MOSFET, and the first end DRV1 of the clamping transistor M3 ′ is electrically connected to the gate of the rectifying transistor MOSFET.

[0075] When the switching power supply is in the startup stage, that is, before the power supply voltage VDD1 is established, when the level of the drain voltage VD1 of the rectifier transistor MOSFET is high, the drain voltage VD1 of the rectifier transistor MOSFET charges the junction capacitance Cgs' of the clamp tube M3' through the transistor J1', the resistor R1' and the diode D1'. After the junction capacitance Cgs' of the clamp tube M3' is charged, the clamp tube M3' is turned on, so that the potential of the first terminal DRV1 of the clamp tube M3' is pulled to the low potential GND. Thus, the clamp tube M3' can clamp the gate terminal of the rectifier transistor MOSFET. In other words, the synchronous rectification controller is in a clamping working state.

[0076] After the power supply voltage VDD1 is established, the signal VDD_OK1 closes the switch S3'. In this way, the potential of the gate terminal of the clamp tube M3' is pulled to the low potential GND, so that the first terminal DRV1 of the clamp tube M3' is controlled by the upper tube M1' and the lower tube M2'. In other words, the synchronous rectification controller is in a normal working state.

[0077] When the synchronous rectification controller is in normal working state, when the conduction signal ON_I1 is at a high level, the signal ON_O1 after the driver U1' is at a high level, so that the switch S2' is closed. In this way, the voltage V_GATE1 at the control end of the lower tube M2' is at a low level, so that the lower tube M2' is disconnected and the upper tube M1' is turned on. As a result, the first terminal DRV1 of the clamp tube M3' outputs a high level, so that the rectifying transistor MOSFET is turned on.

[0078] When the off signal OFF_I1 is at a high level, the signal OFF_O1 after the driver U2' is at a high level, so that the switch S1' is closed. In this way, the voltage V_GATE1 at the control end of the lower tube M2' is at a high level, so that the lower tube M2' is turned on and the upper tube M1' is turned off. As a result, the first terminal DRV1 of the clamp tube M3' outputs a low level, so that the rectifier transistor MOSFET is turned off.

[0079] However, in order to achieve the clamping of the rectifier transistor MOSFET, the synchronous rectifier controller in the related art needs to add an additional clamping tube M3', and in order to have a good clamping effect, the impedance of the clamping tube M3' needs to be smaller, and the clamping tube M3' is a high-voltage tube. Since the smaller the impedance of the clamping tube M3', the larger the area of ​​the clamping tube M3'. Therefore, the synchronous rectifier controller uses a clamping tube M3' with smaller impedance and high voltage, resulting in a larger area of ​​the synchronous rectifier controller.

[0080] In order to solve the above problems, the present application provides a synchronous rectification controller, a control method, a switching power supply, a chip and an electronic device.

[0081] The synchronous rectification controller and the switching power supply may be chips or circuit modules.

[0082] In addition, the synchronous rectification controller and the switching power supply may be integrated into one chip or into different chips, which is not specifically limited in the embodiments of the present application.

[0083] In this application, electronic devices may include, but are not limited to: power adapters, power tools, household appliances, and electric vehicle chargers.

[0084] The switching power supply is, for example, a flyback converter (Flyback). For ease of understanding, the embodiments of the present application are described by taking the flyback converter as an example.

[0085] Reference Figure 2 , Figure 2 This is a schematic diagram of the structure of a switching power supply provided by an embodiment of the present application. Figure 2 As shown, the switching power supply 1000 may include: a transformer 200 , a rectifying transistor Q1 , an output capacitor Cout and a synchronous rectifying controller 100 .

[0086] The like-name end of the secondary winding of the transformer 200 is electrically connected to the upper plate of the output capacitor Cout, the opposite-name end of the secondary winding of the transformer 200 is electrically connected to the drain end of the rectifier transistor Q1 and the power supply end of the synchronous rectifier controller 100, respectively, the gate end of the rectifier transistor Q1 is electrically connected to the output end of the synchronous rectifier controller 100, and the ground end of the synchronous rectifier controller 100, the source end of the rectifier transistor Q1 and the lower plate of the output capacitor Cout are all grounded.

[0087] When the switching power supply 1000 is in the startup phase, the synchronous rectification controller 100 turns on the clamping function, so that the synchronous rectification controller 100 can reuse the low-side power transistor M2 to clamp the voltage at the gate end of the rectifier transistor Q1. Thus, the rectifier transistor Q1 can be prevented from being turned on by mistake, so that the switching power supply 1000 will not have the risk of the primary and secondary sides being common.

[0088] Among them, the low-side power transistor M2 usually refers to the lower tube, and the high-side power transistor M1 usually refers to the upper tube.

[0089] After the switching power supply 1000 is in the startup phase, the synchronous rectification controller 100 turns off the clamping function, so that the synchronous rectification controller 100 can control the rectification transistor Q1 to be turned on or off, so that the synchronous rectification controller 100 can work normally.

[0090] Since the synchronous rectification controller 100 can reuse the low-side power transistor M2 to clamp the voltage at the gate terminal of the rectification transistor Q1, it is avoided that the synchronous rectification controller 100 needs to add an extra clamping transistor, thereby reducing the area of ​​the synchronous rectification controller 100.

[0091] Reference Figure 3 , Figure 3 Shows Figure 2 The structural diagram of the synchronous rectification controller is shown in Figure 2. Figure 3 As shown, the synchronous rectification controller 100 may include: a charging circuit 110 , a driving signal output circuit 120 , a first control circuit 130 , a second control circuit 140 and a driving circuit 150 .

[0092] The input end of the first control circuit 130 is used to access the indication signal VDD_OK2, and the indication signal VDD_OK2 is used to indicate the establishment of the power supply voltage VDD2 of the synchronous rectification controller 100. The output end of the first control circuit 130 is electrically connected to the control end of the charging circuit 110, the first end of the drive signal output circuit 120, and the first end of the second control circuit 140 respectively. The input end of the charging circuit 110 is electrically connected to the drain end of the rectifier transistor Q1, the first output end of the charging circuit 110 and the output end of the drive signal output circuit 120 are both electrically connected to the input end of the drive circuit 150, the output end of the drive circuit 150 is electrically connected to the gate end of the rectifier transistor Q1, the second output end of the charging circuit 110 is electrically connected to the second end of the second control circuit 140, and the output end of the second control circuit 140 is electrically connected to the second end of the drive signal output circuit 120.

[0093] Among them, the charging circuit 110, the driving signal output circuit 120, the first control circuit 130, the second control circuit 140 and the driving circuit 150 can be provided separately or integrated, and the embodiment of the present application does not specifically limit this.

[0094] When the power supply voltage VDD2 of the synchronous rectifier controller 100 is greater than or equal to the threshold voltage, the establishment of the power supply voltage VDD2 of the synchronous rectifier controller 100 is established. When the power supply voltage VDD2 of the synchronous rectifier controller 100 is less than the threshold voltage, the establishment of the power supply voltage VDD2 of the synchronous rectifier controller 100 is not established.

[0095] Below, refer to Figure 4 , Figure 4 A schematic flow chart of a synchronous rectification control method provided in one embodiment of the present application.

[0096] S101 : When the indication signal indicates that the power supply voltage is not established, the first control circuit transmits a first control signal to the charging circuit, the driving signal output circuit and the second control circuit respectively.

[0097] The first control signal is used to instruct the driving circuit to start the clamping function.

[0098] S102, the charging circuit charges the control terminal of the low-side power transistor in the driving circuit according to the first control signal to turn on the low-side power transistor, and charges the second control circuit to generate a second control signal.

[0099] The second control signal is used to control the drive signal output circuit to stop outputting the conduction signal, and the conduction signal is used to drive the rectifying transistor to conduct.

[0100] S103: The second control circuit transmits a second control signal to the driving signal output circuit.

[0101] S104 . The drive signal output circuit stops transmitting the shutdown signal to the drive circuit according to the first control signal, and stops transmitting the on signal to the drive circuit according to the second control signal, so that the drive circuit starts the clamping function.

[0102] The shutdown signal is used to drive the rectifier transistor to shut down.

[0103] S105 , after the clamping function is turned on, the driving circuit uses the turned-on low-side power tube transistor to clamp the voltage of the control terminal of the rectifier transistor to a preset voltage.

[0104] Combine the following Figure 5 , Figure 5 1 is a working timing diagram of a synchronous rectification controller provided in one embodiment of the present application. The working contents of the synchronous rectification controller 100 are described in detail. Figure 5As shown, during the time period t1-t2, that is, when the indication signal VDD_OK2 indicates that the power supply voltage VDD2 is not established, the first control circuit 130 can transmit the first control signal to the charging circuit 110, the drive signal output circuit 120 and the second control circuit 140 respectively, so that the charging circuit 110, the drive signal output circuit 120 and the second control circuit 140 can obtain the first control signal.

[0105] The first control signal is used to instruct the synchronous rectification controller 100 to start the clamping function.

[0106] The charging circuit 110 can charge the control terminal of the low-side power transistor M2 in the driving circuit 150 according to the first control signal, so that the junction capacitance Cgs of the low-side power transistor M2 is in a charged state. In this way, the voltage V_GATE2 at the control terminal of the low-side power transistor M2 increases, so that the low-side power transistor M2 is turned on. At the same time, the charging circuit 110 can charge the second control circuit 140, so that the second control circuit 140 can generate a second control signal.

[0107] The second control signal is used to control the driving signal output circuit 120 to stop outputting the on-signal ON_O2 , and the on-signal ON_O2 is used to drive the rectifying transistor Q1 to turn on.

[0108] In this way, under the action of the first control signal, the second control circuit 140 can generate a second control signal and transmit the second control signal to the driving signal output circuit 120, so that the driving signal output circuit 120 can obtain the second control signal.

[0109] The driving signal output circuit 120 may stop transmitting the off signal OFF_O2 to the driving circuit 150 according to the first control signal, and stop transmitting the on signal ON_O2 to the driving circuit 150 according to the second control signal, so that the driving circuit 150 turns on the clamping function.

[0110] The turn-off signal OFF_O2 is used to drive the rectifier transistor Q1 to turn off.

[0111] Furthermore, after the clamping function is turned on, the driving circuit 150 can use the turned-on low-side power transistor M2 to clamp the voltage at the control end of the rectifier transistor Q1 to a preset voltage, so that the synchronous rectifier controller 100 can clamp the voltage at the control end of the rectifier transistor Q1.

[0112] The preset voltage is, for example, 0V or close to 0V.

[0113] When the power supply voltage VDD2 is not established, the driving circuit 150 can reuse the low-side power transistor M2 to clamp the voltage of the control terminal of the rectifier transistor Q1, so that the synchronous rectifier controller 100 does not need to add an additional clamping transistor, thereby reducing the area of ​​the synchronous rectifier controller 100.

[0114] The synchronous rectification controller provided by the present application, when the indication signal indicates that the power supply voltage is not established, the first control circuit can transmit the first control signal for indicating that the driving circuit turns on the clamping function to the charging circuit, the driving signal output circuit and the second control circuit respectively. The charging circuit can charge the control end of the low-side power transistor in the driving circuit according to the first control signal to turn on the low-side power transistor. In addition, the charging circuit can charge the second control circuit so that the second control circuit generates a second control signal for controlling the driving signal output circuit to stop outputting the conduction signal. Among them, the conduction signal is used to drive the rectifier transistor to turn on. The second control circuit transmits the second control signal to the driving signal output circuit. The driving signal output circuit can stop transmitting the shutdown signal for driving the rectifier transistor to turn off to the driving circuit according to the first control signal, and stop transmitting the conduction signal to the driving circuit according to the second control signal, so that the driving circuit turns on the clamping function. In this way, after turning on the clamping function, the driving circuit uses the low-side power transistor that is turned on to clamp the voltage of the control end of the rectifier transistor to a preset voltage. Since the driving circuit can reuse the low-side power transistor to clamp the voltage of the control terminal of the rectifier transistor, the synchronous rectifier controller does not need to add an additional clamping transistor, thereby reducing the area of ​​the synchronous rectifier controller.

[0115] In some examples, such as Figure 5 As shown, during the time period t2-t3, that is, when the indication signal VDD_OK2 indicates that the power supply voltage VDD2 has been established, the first control circuit 130 can transmit the third control signal to the charging circuit 110, the drive signal output circuit 120 and the second control circuit 140 respectively, so that the charging circuit 110, the drive signal output circuit 120 and the second control circuit 140 can obtain the third control signal.

[0116] The third control signal is used to instruct the driving circuit 150 to turn off the clamping function.

[0117] The charging circuit 110 can stop charging the control terminal of the low-side power transistor M2 according to the third control signal, so that the junction capacitance Cgs of the low-side power transistor M2 is not in a charged state. In this way, the voltage V_GATE2 of the control terminal of the low-side power transistor M2 is controlled by the drive signal output circuit 120, so that the drive circuit 150 turns off the clamping function. In addition, the charging circuit 110 stops charging the second control circuit 140, so that the second control circuit 140 generates a fourth control signal.

[0118] The fourth control signal is used to control the driving signal output circuit 120 to output the on-signal ON_O2.

[0119] In this way, the second control circuit 140 can transmit the fourth control signal to the driving signal output circuit 120, so that the driving signal output circuit 120 can obtain the fourth control signal.

[0120] The driving signal output circuit 120 can transmit the shutdown signal OFF_O2 to the driving circuit 150 according to the third control signal, and can transmit the on signal ON_O2 to the driving circuit 150 according to the fourth control signal, so that the driving circuit 150 can obtain the shutdown signal OFF_O2 and the on signal ON_O2.

[0121] Furthermore, after turning off the clamping function, the driving circuit 150 can drive the rectifier transistor Q1 to turn off according to the shutdown signal OFF_O2, and can drive the rectifier transistor Q1 to turn on according to the turn-on signal ON_O2, so that the synchronous rectifier controller 100 can control the rectifier transistor Q1 to turn on or off, avoiding affecting the normal operation of the synchronous rectifier controller 100.

[0122] Based on the description of the above embodiment, a possible implementation of the first control circuit 130 is exemplified. Figure 3 As shown, the first control circuit 130 may include: a first resistor R1, a second resistor R2, a first switch tube S1, a first capacitor C1 and a first voltage-controlled voltage source VCVS1.

[0123] The first end of the first resistor R1 is used to access the power supply voltage DVDD2, the second end of the first resistor R1 is electrically connected to the first end of the first switch tube S1, the control end of the first switch tube S1 is used to access the indication signal VDD_OK2, the second end of the first switch tube S1 is electrically connected to the first end of the second resistor R2, the upper plate of the first capacitor C1 and the input end of the first voltage-controlled voltage source VCVS1 are both electrically connected between the second end of the first switch tube S1 and the first end of the second resistor R2, the output end of the first voltage-controlled voltage source VCVS1 is electrically connected to the control end of the charging circuit 110, and the second end of the second resistor R2 and the lower plate of the first capacitor C1 are both grounded.

[0124] The first voltage-controlled voltage source VCVS1 and the second voltage-controlled voltage source VCVS2 are both voltage-controlled voltage sources (VCVS).

[0125] The supply voltage DVDD2 is obtained by stepping down the power supply voltage VDD2.

[0126] The first switch tube S1 in the present application may be a bipolar transistor or a field effect transistor, etc. For example, when the first switch tube S1 is a bipolar transistor, the control end of the first switch tube S1 refers to the base of the bipolar transistor, the first end of the first switch tube S1 may be the collector or emitter of the bipolar transistor, and correspondingly, the second end of the first switch tube S1 may be the emitter or collector of the bipolar transistor; when the first switch tube S1 is a field effect transistor, the control end of the first switch tube S1 refers to the gate of the field effect transistor, the first end of the first switch tube S1 may be the drain or source of the field effect transistor, and correspondingly, the second end of the first switch tube S1 may be the source or drain of the field effect transistor.

[0127] The control end of the first switch tube S1 is the input end of the first control circuit 130 , and the output end of the first voltage-controlled voltage source VCVS1 is the output end of the first control circuit 130 .

[0128] When the indication signal VDD_OK2 indicates that the power supply voltage VDD2 is not established, the first switch tube S1 is turned off, so that the power supply voltage DVDD2 cannot charge the first capacitor C1, so that the first voltage V1 on the first capacitor C1 is 0V. In this way, the first voltage-controlled voltage source VCVS1 can amplify the first voltage V1 on the first capacitor C1 to obtain the amplified first amplified voltage βV1. In this way, the first control circuit 130 uses the amplified first amplified voltage βV1 as the first control signal. Thus, the first control circuit 130 can output the first control signal.

[0129] When the indication signal VDD_OK2 indicates that the power supply voltage VDD2 has been established, the first switch tube S1 is turned on, so that the power supply voltage DVDD2 can charge the first capacitor C1. In this way, the first voltage V1 on the first capacitor C1 is established in a very short time, that is, the first voltage V1 on the first capacitor C1 is not 0V. In this way, the first voltage control voltage source VCVS1 can amplify the first voltage V1 on the first capacitor C1 to obtain the amplified first amplified voltage βV1. Furthermore, the first control circuit 130 uses the amplified first amplified voltage βV1 as the third control signal. Thus, the first control circuit 130 can output the third control signal.

[0130] Based on the description of the above embodiment, a possible implementation of the second control circuit 140 is exemplified. Figure 3 As shown, the second control circuit 140 may include: a second capacitor C2, a second switch tube S2 and a second voltage-controlled voltage source VCVS2.

[0131] The upper plate of the second capacitor C2 is electrically connected to the second output terminal of the charging circuit 110, the first end of the second switch tube S2 and the input end of the second voltage-controlled voltage source VCVS2 are both electrically connected between the upper plate of the second capacitor C2 and the second output terminal of the charging circuit 110, the control end of the second switch tube S2 is electrically connected to the output end of the first control circuit 130, the output end of the second voltage-controlled voltage source VCVS2 is electrically connected to the second end of the drive signal output circuit 120, and the lower plate of the second capacitor C2 and the second end of the second switch tube S2 are both grounded.

[0132] The second switch tube S2 in the present application may be a bipolar transistor or a field effect transistor, etc. For example, when the second switch tube S2 is a bipolar transistor, the control end of the second switch tube S2 refers to the base of the bipolar transistor, the first end of the second switch tube S2 may be the collector or emitter of the bipolar transistor, and correspondingly, the second end of the second switch tube S2 may be the emitter or collector of the bipolar transistor; when the second switch tube S2 is a field effect transistor, the control end of the second switch tube S2 refers to the gate of the field effect transistor, the first end of the second switch tube S2 may be the drain or source of the field effect transistor, and correspondingly, the second end of the second switch tube S2 may be the source or drain of the field effect transistor.

[0133] The control end of the second switch tube S2 is the first end of the second control circuit 140 , the upper plate of the second capacitor C2 is the second end of the second control circuit 140 , and the output end of the second voltage control voltage source VCVS2 is the output end of the second control circuit 140 .

[0134] When the indication signal VDD_OK2 indicates that the power supply voltage VDD2 is not established, under the action of the first control signal, the second switch tube S2 is turned off, so that the charging circuit 110 can charge the second capacitor C2. In this way, the second voltage V2 on the second capacitor C2 is established in a very short time, that is, the second voltage V2 on the second capacitor C2 is not 0V. In this way, the second voltage control voltage source VCVS2 can amplify the second voltage V2 on the second capacitor C2 to obtain the amplified second amplified voltage βV2. Furthermore, the second control circuit 140 uses the amplified second amplified voltage βV2 as the second control signal. Thus, the second control circuit 140 can output the second control signal.

[0135] When the indication signal VDD_OK2 indicates that the power supply voltage VDD2 has been established, under the action of the third control signal, the second switch tube S2 is turned on, so that the charging circuit 110 stops charging the second capacitor C2, and the second capacitor C2 is in a discharging state. In this way, the second voltage V2 on the second capacitor C2 will drop to 0V. In this way, the second voltage control voltage source VCVS2 can amplify the second voltage V2 on the second capacitor C2 to obtain the amplified second amplified voltage βV2. Furthermore, the second control circuit 140 uses the amplified second amplified voltage βV2 as the fourth control signal. Thus, the second control circuit 140 can output the fourth control signal.

[0136] Wherein, β is the amplification factor of the second voltage-controlled voltage source VCVS2 and the amplification factor of the first voltage-controlled voltage source VCVS1.

[0137] Based on the description of the above embodiment, a possible implementation of the driving signal output circuit 120 is exemplified. Figure 3 As shown, the driving signal output circuit 120 may include: a first driver U1 , a second driver U2 , a third switch tube S3 and a selection output circuit 121 .

[0138] The power supply end of the first driver U1, the power supply end of the second driver U2 and the power supply end of the selection output circuit 121 are all used to connect to the power supply voltage DVDD2, the output end of the first driver U1 is electrically connected to the first input end of the selection output circuit 121, the output end of the second driver U2 is electrically connected to the second input end of the selection output circuit 121, the output end of the selection output circuit 121 is electrically connected to the input end of the driving circuit 150, the first end of the third switch tube S3 is electrically connected between the output end of the second driver U2 and the second input end of the selection output circuit 121, the control end of the third switch tube S3 is electrically connected to the output end of the second control circuit 140, the first end of the selection output circuit 121 is electrically connected to the output end of the first control circuit 130, and the ground end of the first driver U1, the ground end of the second driver U2 and the second end of the third switch tube S3 are all grounded.

[0139] The first end of the selection output circuit 121 is the first end of the drive signal output circuit 120 , the output end of the selection output circuit 121 is the output end of the drive signal output circuit 120 , and the control end of the third switch tube S3 is the second end of the drive signal output circuit 120 .

[0140] The third switch tube S3 in the present application may be a bipolar transistor or a field effect transistor, etc. For example, when the third switch tube S3 is a bipolar transistor, the control end of the third switch tube S3 refers to the base of the bipolar transistor, the first end of the third switch tube S3 may be the collector or emitter of the bipolar transistor, and correspondingly, the second end of the third switch tube S3 may be the emitter or collector of the bipolar transistor; when the third switch tube S3 is a field effect transistor, the control end of the third switch tube S3 refers to the gate of the field effect transistor, the first end of the third switch tube S3 may be the drain or source of the field effect transistor, and correspondingly, the second end of the third switch tube S3 may be the source or drain of the field effect transistor.

[0141] In some examples, the selection output circuit 121 may include: a fourth switch tube S4 , a fifth switch tube S5 , a sixth switch tube S6 , and a first diode D1 .

[0142] A first end of the fourth switch tube S4 is used to connect to the power supply voltage DVDD2, a control end of the fourth switch tube S4 is electrically connected to the output end of the first driver U1, a second end of the fourth switch tube S4 is electrically connected to the anode of the first diode D1, a cathode of the first diode D1 is electrically connected to a first end of the fifth switch tube S5, a control end of the fifth switch tube S5 is electrically connected to the output end of the second driver U2, a sixth switch tube S6 is connected in parallel with the first diode D1, a control end of the sixth switch tube S6 is electrically connected to the output end of the first control circuit 130, an input end of the drive circuit 150 is electrically connected between the cathode of the first diode D1 and the first end of the fifth switch tube S5, and a second end of the fifth switch tube S5 is grounded.

[0143] The fourth switch tube S4 , the fifth switch tube S5 and the sixth switch tube S6 in the present application may be bipolar transistors or field effect transistors. When the fourth switch tube S4, the fifth switch tube S5 and the sixth switch tube S6 are bipolar transistors, the control ends of the fourth switch tube S4, the fifth switch tube S5 and the sixth switch tube S6 refer to the base of the bipolar transistor, the first ends of the fourth switch tube S4, the fifth switch tube S5 and the sixth switch tube S6 may be the collector or emitter of the bipolar transistor, and correspondingly, the second ends of the fourth switch tube S4, the fifth switch tube S5 and the sixth switch tube S6 may be the emitter or collector of the bipolar transistor; when the fourth switch tube S4, the fifth switch tube S5 and the sixth switch tube S6 are field effect transistors, the control ends of the fourth switch tube S4, the fifth switch tube S5 and the sixth switch tube S6 refer to the gate of the field effect transistor, the first ends of the fourth switch tube S4, the fifth switch tube S5 and the sixth switch tube S6 may be the drain or source of the field effect transistor, and correspondingly, the second ends of the fourth switch tube S4, the fifth switch tube S5 and the sixth switch tube S6 may be the source or drain of the field effect transistor.

[0144] Among them, the control end of the fourth switch tube S4 is the first input end of the selection output circuit 121, the control end of the fifth switch tube S5 is the second input end of the selection output circuit 121, the output end of the selection output circuit 121 is located between the cathode of the first diode D1 and the first end of the fifth switch tube S5, and the control end of the sixth switch tube S6 is the first end of the selection output circuit 121.

[0145] The first driver U1 may transmit an off signal OFF_O2 to the selection output circuit 121 .

[0146] The second driver U2 may transmit a turn-on signal ON_O2 to the selection output circuit 121 .

[0147] Under the action of the second control signal, the third switch tube S3 is turned off, so that the conduction signal ON_O2 is always at a low level. In this way, the fifth switch tube S5 is always turned off, so that the conduction signal ON_O2 cannot be transmitted to the selection output circuit 121. In this way, the selection output circuit 121 stops outputting the conduction signal ON_O2. Under the action of the first control signal, the sixth switch tube S6 is turned off, so that the shutdown signal OFF_O2 cannot directly act on the drive circuit 150, so that the selection output circuit 121 stops outputting the shutdown signal OFF_O2. Thus, the drive signal output circuit 120 stops transmitting the shutdown signal to the drive circuit 150, and stops transmitting the conduction signal to the drive circuit 150. At the same time, the third switch tube S3 remains in a turned-off state to prevent the voltage on the junction capacitor Cgs of the low-side power transistor M2 from being discharged through other paths.

[0148] Under the action of the fourth control signal, the third switch tube S3 is turned on, so that the on-signal ON_O2 is not always at a low level. In this way, the fifth switch tube S5 is always turned on, so that the on-signal ON_O2 can be transmitted to the selection output circuit 121. In this way, under the action of the third control signal, the sixth switch tube S6 is turned on, short-circuiting the first diode D1, so that the off-signal OFF_O2 can directly act on the drive circuit 150, so that the selection output circuit 121 can output the off-signal OFF_O2. Thus, the drive signal output circuit 120 can transmit the off signal to the drive circuit 150, and transmit the on signal to the drive circuit 150.

[0149] Based on the description of the above embodiment, a possible implementation of the charging circuit 110 is exemplified. Figure 3 As shown, the charging circuit 110 may include: a field effect transistor J1, a seventh switch tube S7, a third resistor R3, a second diode D2 and a third diode D3.

[0150] A first end of the field effect transistor J1 is electrically connected to the drain end of the rectifier transistor Q1, a control end of the field effect transistor J1 is grounded, a second end of the field effect transistor J1 is electrically connected to a first end of a third resistor R3, a second end of the third resistor R3 is electrically connected to an anode of a second diode D2, a cathode of the second diode D2 is electrically connected to an input end of the drive circuit 150, an anode of the third diode D3 and a first end of the seventh switch tube S7 are both electrically connected between the second end of the third resistor R3 and the anode of the second diode D2, a cathode of the third diode D3 is electrically connected to a second end of the second control circuit 140, a control end of the seventh switch tube S7 is electrically connected to an output end of the first control circuit 130, and a second end of the seventh switch tube S7 is grounded.

[0151] The seventh switch tube S7 in the present application may be a bipolar transistor or a field effect transistor, etc. For example, when the seventh switch tube S7 is a bipolar transistor, the control end of the seventh switch tube S7 refers to the base of the bipolar transistor, the first end of the seventh switch tube S7 may be the collector or emitter of the bipolar transistor, and correspondingly, the second end of the seventh switch tube S7 may be the emitter or collector of the bipolar transistor; when the seventh switch tube S7 is a field effect transistor, the control end of the seventh switch tube S7 refers to the gate of the field effect transistor, the first end of the seventh switch tube S7 may be the drain or source of the field effect transistor, and correspondingly, the second end of the seventh switch tube S7 may be the source or drain of the field effect transistor.

[0152] Among them, the first end of the field effect transistor J1 is the input end of the charging circuit 110, the control end of the seventh switch tube S7 is the control end of the charging circuit 110, the cathode of the second diode D2 is the first output end of the charging circuit 110, and the cathode of the third diode D3 is the second output end of the charging circuit 110.

[0153] The field effect transistor J1 may be a junction field effect transistor JFET or a metal-oxide semiconductor field effect transistor MOSFET, which is not specifically limited in the embodiment of the present application.

[0154] Wherein, when the field effect transistor J1 is a junction field effect transistor JFET, its control end refers to the gate of the junction field effect transistor JFET, the first end may be the drain or source of the junction field effect transistor JFET, and the corresponding second end may be the source or drain of the junction field effect transistor JFET. When the field effect transistor J1 is a metal-oxide semiconductor field effect transistor MOSFET, its control end refers to the gate of the metal-oxide semiconductor field effect transistor MOSFET, the first end may be the drain or source of the metal-oxide semiconductor field effect transistor MOSFET, and the corresponding second end may be the source or drain of the metal-oxide semiconductor field effect transistor MOSFET.

[0155] Based on the description of the above embodiment, a possible implementation of the driving circuit 150 is exemplified. Figure 3 As shown, the driving circuit 150 may include: a high-side power transistor M1 , a low-side power transistor M2 , and a level inversion circuit 151 .

[0156] The first end of the high-side power transistor M1 is used to access the power supply voltage VDD2, the control end of the high-side power transistor M1 is electrically connected to the output end of the level reversal circuit 151, the second end of the high-side power transistor M1 is electrically connected to the first end of the low-side power transistor M2, the gate end of the rectifier transistor Q1 is electrically connected between the second end of the high-side power transistor M1 and the first end of the low-side power transistor M2, the control end of the low-side power transistor M2 is electrically connected to the first output end of the charging circuit 110, the input end of the level reversal circuit 151 is electrically connected between the control end of the low-side power transistor M2 and the first output end of the charging circuit 110, and the second end of the low-side power transistor M2 is grounded.

[0157] The control terminal of the low-side power transistor M2 is the input terminal of the driving circuit 150 , and the output terminal of the driving circuit 150 is located between the second terminal of the high-side power transistor M1 and the first terminal of the low-side power transistor M2 .

[0158] The level inversion circuit 151 can change the state of the level of the voltage V_GATE2 at the control terminal of the low-side power transistor M2 to turn on or off the high-side power transistor M1 .

[0159] Among them, if the level of the voltage V_GATE2 at the control end of the low-side power transistor M2 is a low level, the level inversion circuit 151 can change the level of the voltage V_GATE2 at the control end of the low-side power transistor M2 to a high level. If the level of the voltage V_GATE2 at the control end of the low-side power transistor M2 is a high level, the level inversion circuit 151 can change the level of the voltage V_GATE2 at the control end of the low-side power transistor M2 to a low level.

[0160] In some examples, the level inversion circuit 151 may include: a NOT gate module U3 and a level conversion module U4.

[0161] The input end of the NOT gate module U3 is electrically connected between the control end of the low-side power transistor M2 and the first output end of the charging circuit 110, the output end of the NOT gate module U3 is electrically connected to the input end of the level conversion module U4, and the output end of the level conversion module U4 is electrically connected to the control end of the high-side power transistor M1.

[0162] The output end of the level conversion module U4 is the output end of the level inversion circuit 151 , and the input end of the NOT gate module U3 is the input end of the level inversion circuit 151 .

[0163] The NOT gate module U3 can change the state of the level of the voltage V_GATE2 at the control end of the low-side power transistor M2 to obtain a first level, and transmit the first level to the level conversion module U4 so that the level conversion module U4 can obtain the first level.

[0164] In this way, the level conversion module U4 can enhance the driving strength of the first level to turn on or off the high-side power transistor M1.

[0165] In some examples, the driving circuit 150 may further include: a Zener diode ZD.

[0166] The cathode of the voltage zener diode ZD is electrically connected between the control terminal of the low-side power transistor M2 and the first output terminal of the charging circuit 110 , and the anode of the voltage zener diode ZD is grounded.

[0167] The voltage on the junction capacitor Cgs of the low-side power transistor M2 is prevented from being too high by the voltage zener diode ZD, thereby preventing the voltage V_GATE2 at the control terminal of the low-side power transistor M2 from being too high, thereby preventing the low-side power transistor M2 from being damaged.

[0168] Combine the following Figure 6 , Figure 6 Shows Figure 3 The control principle diagram of the synchronous rectification controller with the clamping function turned on. Figure 6 As shown, when the power supply voltage VDD2 is not established, the indication signal VDD_OK2 is low level, so that the first switch tube S1 is turned off. In this way, the voltage V1 on the first capacitor C1 is 0V, so that the second switch tube S2, the sixth switch tube S6 and the seventh switch tube S7 are all turned off. In this way, under the action of the turned-off seventh switch tube S7, the drain terminal voltage VD2 of the rectifier transistor Q1 can charge the junction capacitance Cgs of the low-side power transistor M2 through the field effect transistor J1, the third resistor R3 and the second diode D2, so that the synchronous rectification controller 100 turns on the clamping function. Based on this, the voltage V_GATE1 of the control terminal of the low-side power transistor M2 rises in a very short time, so that the low-side power transistor M2 is turned on. In this way, the voltage of the output terminal DRV2 of the drive circuit 150 is clamped to a preset voltage of, for example, 0V.

[0169] At the same time, the drain voltage VD2 of the rectifier transistor Q1 charges the second capacitor C2 through the field effect transistor J1, the third resistor R3 and the third diode D3. Based on this, under the action of the second switch tube S2 that is turned off, the second capacitor C2 is in a charged state, so that the voltage V2 on the second capacitor C2 is established in a very short time. In this way, the voltage V2 on the established second capacitor C2 turns on the third switch tube S3 through the second voltage control voltage source VCVS2, so that the turn-on signal ON_O2 is always low level, so that the turn-on signal ON_O2 cannot control the low-side power transistor M2. Then, the fifth switch tube S5 always keeps the turned-off state, ensuring that the voltage on the junction capacitor Cgs of the low-side power transistor M2 will not be discharged through other paths. And, under the action of the turned-off sixth switch tube S6, the turn-off signal OFF_O2 cannot directly act on the control end of the low-side power transistor M2. Because the power supply voltage VDD2 is not established, the power supply voltage DVDD2 is not established. Therefore, the turn-off signal OFF_O2 cannot control the low-side power transistor M2.

[0170] The first diode D1 can prevent the voltage V_GATE2 at the control terminal of the low-side power transistor M2 from flowing back to DVDD2.

[0171] Combine the following Figure 7 , Figure 7 Shows Figure 3 The control principle diagram of the synchronous rectification controller in the shutdown clamping function. Figure 7 As shown, when the power supply voltage VDD2 has been established, the indication signal VDD_OK2 is at a high level, so that the first switch tube S1 is turned on, and the power supply voltage DVDD2 charges the first capacitor C1 through the first resistor R1, so that the voltage V1 on the first capacitor C1 is established in a very short time. The established voltage V1 on the first capacitor C1 is controlled by the first voltage source VCVS1, so that the second switch tube S2, the sixth switch tube S6 and the seventh switch tube S7 are all turned on. Under the action of the turned-on seventh switch tube S7, the second diode D2 is short-circuited, so that the junction capacitance Cgs of the low-side power transistor M2 is not in a charging state, so that the synchronous rectification controller 100 turns off the clamping function.

[0172] Under the action of the second switch tube S2 that is turned on, the second capacitor C2 is in a discharging state and is no longer in a charging state, so that the voltage V2 on the second capacitor C2 is reduced to 0V. In this way, the third switch tube S3 is turned off, so that the conduction signal ON_O2 can control the fifth switch tube S5, so that the conduction signal ON_O2 can control the low-side power transistor M2. Under the action of the sixth switch tube S6 that is turned on, the first diode D1 is short-circuited, so that the turn-off signal OFF_O2 can directly act on the control end of the low-side power transistor M2, so that the turn-off signal OFF_O2 can control the low-side power transistor M2. Based on this, the synchronous rectification controller 100 is in a normal working state.

[0173] Furthermore, when receiving the on-signal ON_O2, the fifth switch tube S5 is turned on, so that the high-side power transistor M1 is turned on and the low-side power transistor M2 is turned off. Thus, the output terminal DRV2 of the drive circuit 150 outputs a high level, so that the rectifier transistor Q1 is turned on. When receiving the off-signal OFF_O2, the fourth switch tube S4 is turned on, so that the high-side power transistor M1 is turned off and the low-side power transistor M2 is turned on. Thus, the output terminal DRV2 of the drive circuit 150 outputs a low level, so that the rectifier transistor Q1 is turned off.

[0174] Finally, it should be noted that the above embodiments are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A synchronous rectification controller, characterized in that: The synchronous rectification controller is applied to a switching power supply, and the switching power supply comprises: a rectification transistor; the synchronous rectification controller comprises: a charging circuit, a driving signal output circuit, a first control circuit, a second control circuit and a driving circuit; The input end of the first control circuit is used to access an indication signal, and the indication signal is used to indicate the establishment of the power supply voltage of the synchronous rectification controller. The output end of the first control circuit is electrically connected to the control end of the charging circuit, the first end of the drive signal output circuit and the first end of the second control circuit respectively. The input end of the charging circuit is electrically connected to the drain end of the rectifier transistor. The first output end of the charging circuit and the output end of the drive signal output circuit are both electrically connected to the input end of the drive circuit. The output end of the drive circuit is electrically connected to the gate end of the rectifier transistor. The second output end of the charging circuit is electrically connected to the second end of the second control circuit. The output end of the second control circuit is electrically connected to the second end of the drive signal output circuit. The first control circuit is used to transmit a first control signal to the charging circuit, the drive signal output circuit and the second control circuit respectively when the indication signal indicates that the power supply voltage is not established, and the first control signal is used to instruct the drive circuit to turn on the clamping function; The charging circuit is used to charge the control terminal of the low-side power transistor in the driving circuit according to the first control signal to turn on the low-side power transistor, and to charge the second control circuit to make the second control circuit generate a second control signal, wherein the second control signal is used to control the driving signal output circuit to stop outputting the conduction signal, and the conduction signal is used to drive the rectifier transistor to turn on; The second control circuit is used to transmit the second control signal to the drive signal output circuit; The drive signal output circuit is used to stop transmitting the shutdown signal to the drive circuit according to the first control signal, and to stop transmitting the on signal to the drive circuit according to the second control signal, wherein the shutdown signal is used to drive the rectifier transistor to turn off so that the drive circuit turns on the clamping function; The driving circuit is used to clamp the voltage of the control terminal of the rectifier transistor to a preset voltage by using the turned-on low-side power transistor after the clamping function is turned on.

2. The synchronous rectification controller according to claim 1, characterized in that: The first control circuit is further configured to transmit a third control signal to the charging circuit, the drive signal output circuit and the second control circuit respectively when the indication signal indicates that the power supply voltage has been established, wherein the third control signal is used to instruct the driven circuit to turn off the clamping function; The charging circuit is further used to stop charging the control terminal of the low-side power transistor according to the third control signal, so that the drive circuit turns off the clamping function, and stop charging the second control circuit, so that the second control circuit generates a fourth control signal, and the fourth control signal is used to control the drive signal output circuit to output the conduction signal; The second control circuit is further configured to transmit the fourth control signal to the drive signal output circuit; The drive signal output circuit is further configured to transmit the shutdown signal to the drive circuit according to the third control signal, and transmit the on signal to the drive circuit according to the fourth control signal; The driving circuit is used for driving the rectifying transistor to be turned off according to the turn-off signal after the clamping function is turned off, and driving the rectifying transistor to be turned on according to the turn-on signal.

3. The synchronous rectification controller according to claim 2, characterized in that: The first control circuit includes: a first resistor, a second resistor, a first switch tube, a first capacitor and a first voltage-controlled voltage source; The first end of the first resistor is used to access the power supply voltage, the second end of the first resistor is electrically connected to the first end of the first switch tube, the control end of the first switch tube is used to access the indication signal, the second end of the first switch tube is electrically connected to the first end of the second resistor, the upper plate of the first capacitor and the input end of the first voltage-controlled voltage source are both electrically connected between the second end of the first switch tube and the first end of the second resistor, the output end of the first voltage-controlled voltage source is electrically connected to the control end of the charging circuit, and the second end of the second resistor and the lower plate of the first capacitor are both grounded; The first voltage-controlled voltage source is used to amplify the first voltage on the first capacitor to obtain an amplified first amplified voltage, so that the first control circuit uses the amplified first amplified voltage as the first control signal or the third control signal.

4. The synchronous rectification controller according to claim 2, characterized in that: The second control circuit includes: a second capacitor, a second switch tube and a second voltage-controlled voltage source; The upper plate of the second capacitor is electrically connected to the second output terminal of the charging circuit, the first terminal of the second switch tube and the input terminal of the second voltage-controlled voltage source are both electrically connected between the upper plate of the second capacitor and the second output terminal of the charging circuit, the control terminal of the second switch tube is electrically connected to the output terminal of the first control circuit, the output terminal of the second voltage-controlled voltage source is electrically connected to the second terminal of the drive signal output circuit, and the lower plate of the second capacitor and the second terminal of the second switch tube are both grounded; The second voltage-controlled voltage source is used to amplify the second voltage on the second capacitor to obtain an amplified second amplified voltage, so that the second control circuit uses the amplified second amplified voltage as the second control signal or the fourth control signal.

5. The synchronous rectification controller according to claim 2, characterized in that: The driving signal output circuit comprises: a first driver, a second driver, a third switch tube and a selection output circuit; The power supply end of the first driver, the power supply end of the second driver and the power supply end of the selection output circuit are all used to access the power supply voltage, the output end of the first driver is electrically connected to the first input end of the selection output circuit, the output end of the second driver is electrically connected to the second input end of the selection output circuit, the output end of the selection output circuit is electrically connected to the input end of the drive circuit, the first end of the third switch tube is electrically connected between the output end of the second driver and the second input end of the selection output circuit, the control end of the third switch tube is electrically connected to the output end of the second control circuit, the first end of the selection output circuit is electrically connected to the output end of the first control circuit, and the ground end of the first driver, the ground end of the second driver and the second end of the third switch tube are all grounded; The first driver is used to transmit the shutdown signal to the selection output circuit; The second driver is used to transmit the conduction signal to the selection output circuit; The third switch tube is used to be turned off according to the second control signal; or turned on according to the fourth control signal; The selection output circuit is used to stop outputting the shutdown signal according to the first control signal, and to stop outputting the conduction signal under the action of the shut-down third switch tube; or, to output the shutdown signal according to the third control signal, and to output the conduction signal under the action of the conduction third switch tube.

6. The synchronous rectification controller according to claim 5, characterized in that: The selection output circuit includes: a fourth switch tube, a fifth switch tube, a sixth switch tube and a first diode; The first end of the fourth switch tube is used to connect to the power supply voltage, the control end of the fourth switch tube is electrically connected to the output end of the first driver, the second end of the fourth switch tube is electrically connected to the positive electrode of the first diode, the negative electrode of the first diode is electrically connected to the first end of the fifth switch tube, the control end of the fifth switch tube is electrically connected to the output end of the second driver, the sixth switch tube is connected in parallel with the first diode, the control end of the sixth switch tube is electrically connected to the output end of the first control circuit, the input end of the drive circuit is electrically connected between the negative electrode of the first diode and the first end of the fifth switch tube, and the second end of the fifth switch tube is grounded.

7. The synchronous rectification controller according to claim 2, characterized in that: The charging circuit comprises: a field effect transistor, a seventh switch tube, a third resistor, a second diode and a third diode; The first end of the field effect transistor is electrically connected to the drain end of the rectifier transistor, the control end of the field effect transistor is grounded, the second end of the field effect transistor is electrically connected to the first end of the third resistor, the second end of the third resistor is electrically connected to the anode of the second diode, the cathode of the second diode is electrically connected to the input end of the drive circuit, the anode of the third diode and the first end of the seventh switch tube are both electrically connected between the second end of the third resistor and the anode of the second diode, the cathode of the third diode is electrically connected to the second end of the second control circuit, the control end of the seventh switch tube is electrically connected to the output end of the first control circuit, and the second end of the seventh switch tube is grounded.

8. The synchronous rectification controller according to any one of claims 1 to 7, characterized in that: The driving circuit comprises: a high-side power transistor, a low-side power transistor and a level reversal circuit; The first end of the high-side power transistor is used to access the power supply voltage, the control end of the high-side power transistor is electrically connected to the output end of the level reversal circuit, the second end of the high-side power transistor is electrically connected to the first end of the low-side power transistor, the gate end of the rectifier transistor is electrically connected between the second end of the high-side power transistor and the first end of the low-side power transistor, the control end of the low-side power transistor is electrically connected to the first output end of the charging circuit, the input end of the level reversal circuit is electrically connected between the control end of the low-side power transistor and the first output end of the charging circuit, and the second end of the low-side power transistor is grounded; The level inversion circuit is used to change the state of the voltage level of the control terminal of the low-side power transistor to turn on or off the high-side power transistor.

9. The synchronous rectification controller according to claim 8, characterized in that: The driving circuit further includes: a voltage stabilizing diode; The cathode of the voltage stabilizing diode is electrically connected between the control terminal of the low-side power transistor and the first output terminal of the charging circuit, and the anode of the voltage stabilizing diode is grounded.

10. The synchronous rectification controller according to claim 9, characterized in that: The level inversion circuit comprises: a NOT gate module and a level conversion module; The input end of the NOT gate module is electrically connected between the control end of the low-side power transistor and the first output end of the charging circuit, the output end of the NOT gate module is electrically connected to the input end of the level conversion module, and the output end of the level conversion module is electrically connected to the control end of the high-side power transistor; The NOT gate module is used to change the state of the voltage level of the control terminal of the low-side power transistor to obtain a first level, and transmit the first level to the level conversion module; The level conversion module is used to enhance the driving strength of the first level to turn on or off the high-side power transistor.

11. A synchronous rectification control method, characterized in that: The method is performed by a synchronous rectification controller, which is applied to a switching power supply, wherein the switching power supply comprises: a rectification transistor; the synchronous rectification controller comprises: a charging circuit, a drive signal output circuit, a first control circuit, a second control circuit and a drive circuit, wherein the output end of the first control circuit is electrically connected to the control end of the charging circuit, the first end of the drive signal output circuit and the first end of the second control circuit respectively, the input end of the charging circuit is electrically connected to the drain end of the rectification transistor, the first output end of the charging circuit and the output end of the drive signal output circuit are both electrically connected to the input end of the drive circuit, the output end of the drive circuit is electrically connected to the gate end of the rectification transistor, the second output end of the charging circuit is electrically connected to the second end of the second control circuit, and the output end of the second control circuit is electrically connected to the second end of the drive signal output circuit; the method comprises: The input end of the first control circuit receives an indication signal, and the indication signal is used to indicate the establishment of the power supply voltage of the synchronous rectification controller; when the indication signal indicates that the power supply voltage is not established, the first control circuit transmits a first control signal to the charging circuit, the drive signal output circuit and the second control circuit respectively, and the first control signal is used to instruct the drive circuit to turn on the clamping function; The charging circuit charges the control terminal of the low-side power transistor in the driving circuit according to the first control signal to turn on the low-side power transistor, and charges the second control circuit to make the second control circuit generate a second control signal, wherein the second control signal is used to control the driving signal output circuit to stop outputting the conduction signal, and the conduction signal is used to drive the rectifier transistor to turn on; The second control circuit transmits the second control signal to the drive signal output circuit; The drive signal output circuit stops transmitting the shutdown signal to the drive circuit according to the first control signal, and stops transmitting the on signal to the drive circuit according to the second control signal, wherein the shutdown signal is used to drive the rectifier transistor to turn off, so that the drive circuit turns on the clamping function; After the clamping function is turned on, the driving circuit uses the turned-on low-side power transistor to clamp the voltage of the control terminal of the rectifier transistor to a preset voltage.

12. The control method according to claim 11, characterized in that: When the indication signal indicates that the power supply voltage has been established, the first control circuit transmits a third control signal to the charging circuit, the drive signal output circuit and the second control circuit respectively, wherein the third control signal is used to instruct the drive circuit to turn off the clamping function; The charging circuit stops charging the control terminal of the low-side power transistor according to the third control signal, so that the drive circuit turns off the clamping function, and stops charging the second control circuit, so that the second control circuit generates a fourth control signal, and the fourth control signal is used to control the drive signal output circuit to output the conduction signal; The second control circuit transmits the fourth control signal to the drive signal output circuit; The drive signal output circuit transmits the shutdown signal to the drive circuit according to the third control signal, and transmits the on signal to the drive circuit according to the fourth control signal; After turning off the clamping function, the driving circuit drives the rectifying transistor to turn off according to the shut-down signal, and drives the rectifying transistor to turn on according to the turn-on signal.

13. A switching power supply, characterized in that: The switching power supply comprises: a transformer, a rectifier transistor, an output capacitor and a synchronous rectifier controller as claimed in any one of claims 1 to 10; The like-name end of the secondary winding of the transformer is electrically connected to the upper plate of the output capacitor, the opposite-name end of the secondary winding of the transformer is electrically connected to the drain end of the rectifier transistor and the power supply end of the synchronous rectifier controller respectively, the gate end of the rectifier transistor is electrically connected to the output end of the synchronous rectifier controller, and the ground end of the synchronous rectifier controller, the source end of the rectifier transistor and the lower plate of the output capacitor are all grounded.

14. A control circuit, characterized in that: It comprises a processor and a memory, wherein a computer program is stored in the memory, and when the processor executes the computer program, the steps of the synchronous rectification control method as claimed in claim 11 or 12 are implemented.

15. A chip, characterized in that: It comprises any one of the following: a synchronous rectification controller as described in any one of claims 1 to 10, a switching power supply as described in claim 13, and a control circuit as described in claim 14.

16. An electronic device, characterized in that: include: The chip as claimed in claim 15.

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