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

Abstract

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

Description

Technical Field

[0001] This application relates to the field of power management chip technology, and in particular to a synchronous rectifier controller, control method, switching power supply, chip, control circuit and electronic equipment. Background Technology

[0002] With the development of power electronics technology, high efficiency and small size have become the trends in switching power supplies. Under this trend, synchronous rectification technology, used to improve power conversion efficiency, is widely used in switching power supplies such as AC-DC and DC-DC converters. Synchronous rectification technology typically uses diodes as rectifiers. However, due to the large forward voltage drop of diodes, power losses are significant in high-current applications. Therefore, synchronous rectification technology uses MOSFETs (Metal Transistors) instead of diodes as rectifiers. MOSFETs have lower on-resistance, which significantly reduces power losses. The advantages of using MOSFETs as rectifiers are particularly evident in low-voltage, high-current applications.

[0003] However, during the startup phase of the switching power supply, when the synchronous rectifier controller is in the undervoltage lockout (UVLO) protection state, it cannot control the rectifier transistor MOSFET because the power supply voltage has not yet been established. Therefore, the synchronous rectifier controller needs to clamp the gate of the rectifier transistor MOSFET to prevent it from being accidentally turned on. This avoids the risk of interconnection between the primary and secondary sides of the switching power supply.

[0004] In related technologies, before the power supply voltage is established, the synchronous rectification controller needs to add an additional clamping transistor to clamp the gate of the rectifier transistor MOSFET to prevent the rectifier transistor MOSFET from being turned on accidentally. Moreover, in order to achieve a better clamping effect, clamping transistors with low impedance and high voltage are often used, resulting in a large area of ​​the synchronous rectification controller. Summary of the Invention

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

[0006] In a first aspect, this application provides a synchronous rectification controller, which is applied in a switching power supply. The switching power supply includes a rectifier transistor. The synchronous rectification controller includes a charging circuit, a drive signal output circuit, a first control circuit, a second control circuit, and a drive circuit.

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

[0008] The first control circuit is configured 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 has not been established. The first control signal is used to instruct the drive circuit to activate 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, so as to turn on the low-side power transistor, and to charge the second control circuit so as to generate a second control signal. 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 conduct.

[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 a turn-off signal to the drive circuit according to the first control signal, and to stop transmitting the turn-on signal to the drive circuit according to the second control signal. The turn-off signal is used to drive the rectifier transistor to turn off, so that the drive circuit can enable the clamping function.

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

[0013] With the synchronous rectifier controller provided in the first aspect, when the indication signal indicates that the power supply voltage has not been established, the first control circuit can transmit a first control signal to the charging circuit, the drive signal output circuit, and the second control circuit, respectively, to instruct the drive circuit to activate its clamping function. The charging circuit can charge the control terminal of the low-side power transistor in the drive circuit according to the first control signal, causing the low-side power transistor to conduct. Furthermore, the charging circuit can charge the second control circuit, causing the second control circuit to generate a second control signal to control the drive signal output circuit to stop outputting a conduction signal. The conduction signal is used to drive the rectifier transistor to conduct. The second control circuit transmits the second control signal to the drive signal output circuit. The drive signal output circuit can stop transmitting a turn-off signal to the drive circuit to drive the rectifier transistor to turn off according to the first control signal, and stop transmitting a conduction signal to the drive circuit according to the second control signal, thus activating the clamping function of the drive circuit. In this way, after activating the clamping function, the drive circuit uses the conducting low-side power transistor to clamp the voltage at the control terminal of the rectifier transistor to a preset voltage. Because the drive circuit can reuse the low-side power transistor to clamp the voltage at the control terminal of the rectifier transistor, the synchronous rectifier controller does not require an additional clamping transistor. This reduces the area of ​​the synchronous rectifier controller.

[0014] In one 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. The third control signal is used to instruct the drive circuit to turn off the clamping function.

[0015] The charging circuit is also used to stop charging to the control terminal of the low-side power transistor according to the third control signal, so as to turn off the clamping function of the driving circuit, and to stop charging to the second control circuit, so as to generate a fourth control signal of the second control circuit, the fourth control signal being used to control the driving signal output circuit to output the conduction signal.

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

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

[0018] The driving circuit is configured to, after the clamping function is turned off, drive the rectifier transistor to turn off according to the turn-off signal, and drive the rectifier transistor to turn on according to the turn-on signal.

[0019] In one possible design, the first control circuit includes: a first resistor, a second resistor, a first switching transistor, a first capacitor, and a first voltage control voltage source;

[0020] The first end of the first resistor is used to connect to the power supply voltage. The second end of the first resistor is electrically connected to the first end of the first switching transistor. The control end of the first switching transistor is used to connect to the indication signal. The second end of the first switching transistor 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 control voltage source are both electrically connected between the second end of the first switching transistor and the first end of the second resistor. The output end of the first voltage control voltage source is electrically connected to the control end of the charging circuit. The second end of the second resistor and the lower plate of the first capacitor are both grounded.

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

[0022] In one possible design, the second control circuit includes: a second capacitor, a second switching transistor, and a second voltage control 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 and the input terminal of the second voltage control 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 is electrically connected to the output terminal of the first control circuit. The output terminal of the second voltage control voltage source is electrically connected to the second terminal of the drive signal output circuit. The lower plate of the second capacitor and the second terminal of the second switch are both grounded.

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

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

[0026] The power supply terminals of the first driver, the second driver, and the selection output circuit are all connected to the power supply voltage. The output terminal of the first driver is electrically connected to the first input terminal of the selection output circuit, the output terminal of the second driver is electrically connected to the second input terminal of the selection output circuit, the output terminal of the selection output circuit is electrically connected to the input terminal of the driving circuit, the first terminal of the third switch is electrically connected between the output terminal of the second driver and the second input terminal of the selection output circuit, the control terminal of the third switch is electrically connected to the output terminal of the second control circuit, the first terminal of the selection output circuit is electrically connected to the output terminal of the first control circuit, and the ground terminals of the first driver, the second driver, and the third switch are all grounded.

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

[0028] The second driver is used to transmit the turn-on signal to the selected output circuit;

[0029] The third switch is used to turn off according to the second control signal; or to turn on according to the fourth control signal.

[0030] The selection output circuit is configured to, according to the first control signal, stop outputting the shutdown signal and, under the action of the shut-off third switch, stop outputting the turn-on signal; or, according to the third control signal, output the shutdown signal and, under the action of the turn-on third switch, output the turn-on signal.

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

[0032] The first terminal of the fourth switch is used to connect to the power supply voltage. The control terminal of the fourth switch is electrically connected to the output terminal of the first driver. The second terminal of the fourth switch is electrically connected to the anode of the first diode. The cathode of the first diode is electrically connected to the first terminal of the fifth switch. The control terminal of the fifth switch is electrically connected to the output terminal of the second driver. The sixth switch is connected in parallel with the first diode. The control terminal of the sixth switch is electrically connected to the output terminal of the first control circuit. The input terminal of the drive circuit is electrically connected between the cathode of the first diode and the first terminal of the fifth switch. The second terminal of the fifth switch is grounded.

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

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

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

[0036] The first terminal of the high-side power transistor is used to connect to the power supply voltage. The control terminal of the high-side power transistor is electrically connected to the output terminal of the level inverting circuit. The second terminal of the high-side power transistor is electrically connected to the first terminal of the low-side power transistor. The gate terminal of the rectifier transistor is electrically connected between the second terminal of the high-side power transistor and the first terminal of the low-side power transistor. The control terminal of the low-side power transistor is electrically connected to the first output terminal of the charging circuit. The input terminal of the level inverting circuit is electrically connected between the control terminal of the low-side power transistor and the first output terminal of the charging circuit. The second terminal of the low-side power transistor is grounded.

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

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

[0039] The negative terminal of the Zener 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 positive terminal of the Zener diode is grounded.

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

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

[0042] The NOT gate module is used to change the state of the 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;

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

[0044] Secondly, this application provides a synchronous rectification control method, which is executed by a synchronous rectification controller in the first aspect and various possible designs of the first aspect. The synchronous rectification controller is applied in a switching power supply, the switching power supply including a rectifier transistor; the synchronous rectification controller includes a charging circuit, a drive signal output circuit, a first control circuit, a second control circuit, and a drive circuit, wherein the output terminal of the first control circuit is electrically connected to the control terminal of the charging circuit, the first terminal of the drive signal output circuit, and the first terminal of the second control circuit, respectively; the input terminal of the charging circuit is electrically connected to the drain terminal of the rectifier transistor; the first output terminal of the charging circuit and the output terminal of the drive signal output circuit are both electrically connected to the input terminal of the drive circuit; the output terminal of the drive circuit is electrically connected to the gate terminal of the rectifier transistor; the second output terminal of the charging circuit is electrically connected to the second terminal of the second control circuit; and the output terminal of the second control circuit is electrically connected to the second terminal of the drive signal output circuit; the method includes:

[0045] The input terminal of the first control circuit receives an indication signal, which is used to indicate the establishment status of the power supply voltage of the synchronous rectifier controller; when the indication signal indicates that the power supply voltage has not been 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, which is used to instruct the drive circuit to activate 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, so as to turn on the low-side power transistor, and charges the second control circuit so as to generate a second control signal. 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 conduct.

[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 turn-off signal to the drive circuit according to the first control signal and stops transmitting the turn-on signal to the drive circuit according to the second control signal. The turn-off signal is used to drive the rectifier transistor to turn off so that the drive circuit can enable the clamping function.

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

[0050] In one 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. The third control signal is used to instruct the drive circuit to turn off the clamping function.

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

[0054] After the clamping function is turned off, the driving circuit drives the rectifier transistor to turn off according to the turn-off signal, and drives the rectifier transistor to turn on according to the turn-on signal.

[0055] The beneficial effects of the methods provided in the second aspect and the various possible designs of the second aspect can be found in the first aspect and the various possible implementations of the first aspect, and will not be repeated here.

[0056] Thirdly, this application provides a switching power supply, including: a transformer, a rectifier transistor, an output capacitor, and a synchronous rectifier controller in the first aspect and various possible designs of the first aspect;

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

[0058] Fourthly, this application provides a control circuit. The control circuit includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the methods provided in the second aspect and various possible designs of the second aspect described above.

[0059] Fifthly, this application provides a chip comprising any one of the following: the synchronous rectifier controller in the first aspect and various possible designs of the first aspect, the switching power supply in the third aspect, and the control circuit in the fourth aspect.

[0060] Sixthly, this application provides an electronic device, including the chip described in the fifth aspect above.

[0061] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0062] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0063] Figure 1 This is a schematic diagram of the structure of a synchronous rectifier controller in related technologies;

[0064] Figure 2 This is a schematic diagram of the structure of a switching power supply provided in an embodiment of this application;

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

[0066] Figure 4 A flowchart illustrating a synchronous rectification control method provided in an embodiment of this application;

[0067] Figure 5 A timing diagram of a synchronous rectifier controller provided in one embodiment of this application;

[0068] Figure 6 A schematic diagram of the control method of a synchronous rectifier controller with clamping function enabled, provided in an embodiment of this application;

[0069] Figure 7 This is a schematic diagram of the control method of a synchronous rectifier controller under the shutdown clamping function, provided in an embodiment of this application. Detailed Implementation

[0070] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c alone can mean: a alone, b alone, c alone, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0071] The terms “center,” “longitudinal,” “lateral,” “up,” “down,” “left,” “right,” “front,” and “rear,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0072] The terms "connected" and "connected" should be interpreted broadly. For example, in circuit structures, "connected" or "connected" can refer not only to physical connections but also to electrical or signal connections. This could be a direct connection (physical connection) or an indirect connection via at least one intermediate component, as long as the circuit is connected. It could also refer to the internal connection between two components. Similarly, a signal connection can refer to a connection via a circuit or a medium, such as radio waves. Those skilled in the art will understand the specific meaning of these terms in this application based on the specific circumstances.

[0073] Reference Figure 1 , Figure 1This is a schematic diagram of the structure of a synchronous rectifier controller in related technologies. For example... Figure 1 As shown, the synchronous rectification controller in the related technology may include: transistor J1', resistor R1', diode D1', switch S1', switch S2', switch S3', driver U1', driver U2', NOT gate U3', level shifter U4', upper transistor M1', lower transistor M2', and clamping transistor M3'.

[0074] Among them, the first terminal of transistor J1' is electrically connected to the drain of rectifier transistor MOSFET, and the first terminal DRV1 of clamping transistor M3' is electrically connected to the gate of rectifier transistor MOSFET.

[0075] When the switching power supply is in the startup phase, that is, before the power supply voltage VDD1 is established, when 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 clamping transistor M3' through transistor J1', resistor R1', and diode D1'. After the junction capacitance Cgs' of the clamping transistor M3' is charged, the clamping transistor M3' turns on, pulling the potential of its first terminal DRV1 to a low potential GND. Thus, the clamping transistor M3' can clamp the gate terminal of the rectifier transistor MOSFET. In other words, the synchronous rectification controller is in a clamping operation state.

[0076] After the power supply voltage VDD1 is established, the signal VDD_OK1 closes the switch S3'. This pulls the gate potential of the clamping transistor M3' to a low potential GND, causing the first terminal DRV1 of the clamping transistor M3' to be controlled by the upper transistor M1' and the lower transistor M2'. In other words, the synchronous rectifier controller is in normal operating condition.

[0077] When the synchronous rectifier controller is operating normally, if the ON_I1 signal is high, the ON_O1 signal after the driver U1' is also high, causing switch S2' to close. This results in a low voltage V_GATE1 at the control terminal of the lower transistor M2', causing M2' to turn off and the upper transistor M1' to turn on. Consequently, the first terminal DRV1 of the clamping transistor M3' outputs a high level, turning on the rectifier transistor MOSFET.

[0078] When the turn-off signal OFF_I1 is high, the signal OFF_O1 after driver U2' is also high, causing switch S1' to close. This results in the voltage V_GATE1 at the control terminal of the lower transistor M2' being high, turning on the lower transistor M2' and turning off the upper transistor M1'. Consequently, the first terminal DRV1 of clamping transistor M3' outputs a low level, turning off the rectifier transistor MOSFET.

[0079] However, in order to clamp the rectifier MOSFETs, the synchronous rectification controller in related technologies requires an additional clamping transistor M3'. Furthermore, for a good clamping effect, the impedance of clamping transistor M3' needs to be lower, and M3' is a high-voltage transistor. Since a lower impedance clamping transistor M3' results in a larger area, the use of a lower impedance, high-voltage clamping transistor M3' in the synchronous rectification controller leads to a larger controller area.

[0080] To address the aforementioned issues, this application provides a synchronous rectification controller, a control method, a switching power supply, a chip, and an electronic device.

[0081] The synchronous rectifier controller and the switching power supply can be either chips or circuit modules.

[0082] Furthermore, the synchronous rectifier controller and the switching power supply can be integrated into one chip or into different chips; this application does not specifically limit this.

[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 in this application are all described using a flyback converter as an example.

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

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

[0087] When the switching power supply 1000 is in the startup phase, the synchronous rectifier controller 100 activates its clamping function, allowing it to reuse the low-side power transistor M2 to clamp the voltage at the gate of the rectifier transistor Q1. This prevents the rectifier transistor Q1 from being accidentally turned on, eliminating the risk of common conduction between the primary and secondary sides of the switching power supply 1000.

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

[0089] After the switching power supply 1000 is in the startup phase, the synchronous rectifier controller 100 disables the clamping function, enabling the synchronous rectifier controller 100 to control the rectifier transistor Q1 to turn on or off, so that the synchronous rectifier 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 of the rectifier transistor Q1, the synchronous rectification controller 100 avoids the need for an additional clamping transistor. This reduces the area of ​​the synchronous rectification controller 100.

[0091] Reference Figure 3 , Figure 3 It shows Figure 2 A schematic diagram of the structure of a synchronous rectifier controller. (See diagram below.) Figure 3 As shown, the synchronous rectifier controller 100 may include: a charging circuit 110, a drive signal output circuit 120, a first control circuit 130, a second control circuit 140, and a drive circuit 150.

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

[0093] The charging circuit 110, the drive signal output circuit 120, the first control circuit 130, the second control circuit 140, and the drive circuit 150 can be set separately or integrated. This application embodiment does not make specific limitations on this.

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

[0095] Below, refer to Figure 4 , Figure 4 This is a flowchart illustrating a synchronous rectification control method provided in an embodiment of this application.

[0096] S101. When the indicator signal indicates that the power supply voltage has not been established, the first control circuit transmits the first control signal to the charging circuit, the drive signal output circuit, and the second control circuit respectively.

[0097] The first control signal is used to instruct the drive circuit to enable 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, so as to turn on the low-side power transistor, and charges the second control circuit so as to generate the 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 rectifier transistor to conduct.

[0100] S103, The second control circuit transmits the second control signal to the drive signal output circuit.

[0101] S104. The drive signal output circuit stops transmitting the turn-off signal to the drive circuit according to the first control signal and stops transmitting the turn-on signal to the drive circuit according to the second control signal, so that the drive circuit can activate the clamping function.

[0102] The turn-off signal is used to drive the rectifier transistor to turn off.

[0103] S105. After the clamping function is enabled, the drive circuit uses the conducting low-side power transistor to clamp the voltage at the control terminal of the rectifier transistor to the preset voltage.

[0104] The following is combined Figure 5 , Figure 5 This is a timing diagram illustrating the operation of a synchronous rectifier controller according to an embodiment of this application. The operation of the synchronous rectifier controller 100 is described in detail. Figure 5As shown, during the t1-t2 period, that is, when the indicator signal VDD_OK2 indicates that the power supply voltage VDD2 has not been 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 rectifier controller 100 to enable 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 charging state. As a result, the voltage V_GATE2 at the control terminal of the low-side power transistor M2 increases, turning on the low-side power transistor M2. Simultaneously, the charging circuit 110 can charge the second control circuit 140, enabling the second control circuit 140 to generate a second control signal.

[0107] The second control signal is used to control the drive signal output circuit 120 to stop outputting the ON_O2 signal, and the ON_O2 signal is used to drive the rectifier 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 drive signal output circuit 120, so that the drive signal output circuit 120 can acquire the second control signal.

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

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

[0111] Furthermore, after the clamping function is enabled, the drive circuit 150 can use the conducting low-side power transistor M2 to clamp the voltage at the control terminal of the rectifier transistor Q1 to a preset voltage, so that the synchronous rectifier controller 100 can clamp the voltage at the control terminal 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 drive circuit 150 can reuse the low-side power transistor M2 to clamp the voltage at the control terminal of the rectifier transistor Q1, so the synchronous rectifier controller 100 does not need to add an additional clamping transistor. As a result, the area of ​​the synchronous rectifier controller 100 can be reduced.

[0114] The synchronous rectification controller provided in this application, when the power supply voltage is not established as indicated by the indicator signal, allows the first control circuit to transmit a first control signal to the charging circuit, the drive signal output circuit, and the second control circuit, respectively, to instruct the drive circuit to activate its clamping function. The charging circuit can charge the control terminal of the low-side power transistor in the drive circuit according to the first control signal, turning on the low-side power transistor. Furthermore, the charging circuit can charge the second control circuit, causing the second control circuit to generate a second control signal to control the drive signal output circuit to stop outputting a conduction signal. This conduction signal is used to drive the rectifier transistor to conduct. The second control circuit transmits the second control signal to the drive signal output circuit. The drive signal output circuit can stop transmitting a turn-off signal to the drive circuit to turn off the rectifier transistor according to the first control signal, and stop transmitting a conduction signal to the drive circuit according to the second control signal, thus activating the clamping function of the drive circuit. In this way, after activating the clamping function, the drive circuit uses the conducting low-side power transistor to clamp the voltage at the control terminal of the rectifier transistor to a preset voltage. Because the drive circuit can reuse the low-side power transistor to clamp the voltage at the control terminal of the rectifier transistor, the synchronous rectifier controller does not require an additional clamping transistor. This reduces the area of ​​the synchronous rectifier controller.

[0115] In some examples, such as Figure 5 As shown, during the t2-t3 period, that is, when the indicator 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 drive 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 charging state. Thus, the voltage V_GATE2 at the control terminal of the low-side power transistor M2 is controlled by the drive signal output circuit 120, causing the drive circuit 150 to disable its clamping function. Furthermore, the charging circuit 110 stops charging the second control circuit 140, causing the second control circuit 140 to generate a fourth control signal.

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

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

[0120] According to the third control signal, the drive signal output circuit 120 can transmit the off signal OFF_O2 to the drive circuit 150, and according to the fourth control signal, it can transmit the on signal ON_O2 to the drive circuit 150, so that the drive circuit 150 can acquire the off signal OFF_O2 and the on signal ON_O2.

[0121] Furthermore, after the clamping function is turned off, the drive circuit 150 can drive the rectifier transistor Q1 to turn off according to the turn-off 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, thus avoiding affecting the normal operation of the synchronous rectifier controller 100.

[0122] Based on the description of the above embodiments, an exemplary possible implementation of the first control circuit 130 is provided. For example... Figure 3 As shown, the first control circuit 130 may include: a first resistor R1, a second resistor R2, a first switching transistor S1, a first capacitor C1, and a first voltage control voltage source VCVS1.

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

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

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

[0126] In this application, the first switching transistor S1 can be a bipolar transistor or a field-effect transistor, etc. For example, when the first switching transistor S1 is a bipolar transistor, the control terminal of the first switching transistor S1 refers to the base of the bipolar transistor, and the first terminal of the first switching transistor S1 can be the collector or emitter of the bipolar transistor. Correspondingly, the second terminal of the first switching transistor S1 can be the emitter or collector of the bipolar transistor. When the first switching transistor S1 is a field-effect transistor, the control terminal of the first switching transistor S1 refers to the gate of the field-effect transistor, and the first terminal of the first switching transistor S1 can be the drain or source of the field-effect transistor. Correspondingly, the second terminal of the first switching transistor S1 can be the source or drain of the field-effect transistor.

[0127] The control terminal of the first switching transistor S1 is the input terminal of the first control circuit 130, and the output terminal of the first voltage control voltage source VCVS1 is the output terminal of the first control circuit 130.

[0128] When the indicator signal VDD_OK2 indicates that the power supply voltage VDD2 is not established, the first switch S1 is turned off, preventing the power supply voltage DVDD2 from charging the first capacitor C1, resulting in a first voltage V1 of 0V on the first capacitor C1. Thus, the first voltage control voltage source VCVS1 can amplify the first voltage V1 on the first capacitor C1 to obtain an amplified first voltage βV1. The first control circuit 130 then uses this amplified first voltage βV1 as the first control signal. Therefore, the first control circuit 130 can output the first control signal.

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

[0130] Based on the description of the above embodiments, an exemplary possible implementation of the second control circuit 140 is provided. For example... Figure 3 As shown, the second control circuit 140 may include: a second capacitor C2, a second switch S2, and a second voltage control 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 terminal of the second switch S2 and the input terminal of the second voltage control 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 terminal of the second switch S2 is electrically connected to the output terminal of the first control circuit 130. The output terminal of the second voltage control voltage source VCVS2 is electrically connected to the second terminal of the drive signal output circuit 120. The lower plate of the second capacitor C2 and the second terminal of the second switch S2 are both grounded.

[0132] The second switch S2 in this application can be a bipolar transistor or a field-effect transistor, etc. For example, when the second switch S2 is a bipolar transistor, the control terminal of the second switch S2 refers to the base of the bipolar transistor, and the first terminal of the second switch S2 can be the collector or emitter of the bipolar transistor. Correspondingly, the second terminal of the second switch S2 can be the emitter or collector of the bipolar transistor. When the second switch S2 is a field-effect transistor, the control terminal of the second switch S2 refers to the gate of the field-effect transistor, and the first terminal of the second switch S2 can be the drain or source of the field-effect transistor. Correspondingly, the second terminal of the second switch S2 can be the source or drain of the field-effect transistor.

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

[0134] When the indicator signal VDD_OK2 indicates that the power supply voltage VDD2 has not been established, the second switch S2 is turned off under the action of the first control signal, allowing the charging circuit 110 to charge the second capacitor C2. Thus, the second voltage V2 on the second capacitor C2 is established within a very short time, meaning that 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 an amplified second voltage βV2. Furthermore, the second control circuit 140 uses the amplified second voltage βV2 as the second control signal. Therefore, the second control circuit 140 can output the second control signal.

[0135] When the indicator signal VDD_OK2 indicates that the power supply voltage VDD2 has been established, under the action of the third control signal, the second switch S2 is turned on, causing the charging circuit 110 to stop charging the second capacitor C2 and the second capacitor C2 to be in a discharging state. Thus, 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 an amplified second voltage βV2. Furthermore, the second control circuit 140 uses the amplified second voltage βV2 as the fourth control signal. Therefore, the second control circuit 140 can output the fourth control signal.

[0136] Where β is the amplification factor of the second voltage control voltage source VCVS2 and the amplification factor of the first voltage control voltage source VCVS1.

[0137] Based on the description of the above embodiments, an exemplary possible implementation of the drive signal output circuit 120 is provided. For example... Figure 3 As shown, the drive signal output circuit 120 may include: a first driver U1, a second driver U2, a third switch S3, and a selection output circuit 121.

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

[0139] Among them, the first terminal of the selection output circuit 121 is the first terminal of the drive signal output circuit 120, the output terminal of the selection output circuit 121 is the output terminal of the drive signal output circuit 120, and the control terminal of the third switch S3 is the second terminal of the drive signal output circuit 120.

[0140] The third switch S3 in this application can be a bipolar transistor or a field-effect transistor, etc. For example, when the third switch S3 is a bipolar transistor, the control terminal of the third switch S3 refers to the base of the bipolar transistor, and the first terminal of the third switch S3 can be the collector or emitter of the bipolar transistor. Correspondingly, the second terminal of the third switch S3 can be the emitter or collector of the bipolar transistor. When the third switch S3 is a field-effect transistor, the control terminal of the third switch S3 refers to the gate of the field-effect transistor, and the first terminal of the third switch S3 can be the drain or source of the field-effect transistor. Correspondingly, the second terminal of the third switch S3 can be the source or drain of the field-effect transistor.

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

[0142] The first terminal of the fourth switch S4 is used to connect to the power supply voltage DVDD2. The control terminal of the fourth switch S4 is electrically connected to the output terminal of the first driver U1. The second terminal of the fourth switch S4 is electrically connected to the positive terminal of the first diode D1. The negative terminal of the first diode D1 is electrically connected to the first terminal of the fifth switch S5. The control terminal of the fifth switch S5 is electrically connected to the output terminal of the second driver U2. The sixth switch S6 is connected in parallel with the first diode D1. The control terminal of the sixth switch S6 is electrically connected to the output terminal of the first control circuit 130. The input terminal of the drive circuit 150 is electrically connected between the negative terminal of the first diode D1 and the first terminal of the fifth switch S5. The second terminal of the fifth switch S5 is grounded.

[0143] The fourth switch S4, the fifth switch S5, and the sixth switch S6 in this application can be bipolar transistors or field-effect transistors, etc. When the fourth switch S4, the fifth switch S5, and the sixth switch S6 are bipolar transistors, the control terminals of the fourth switch S4, the fifth switch S5, and the sixth switch S6 refer to the base of the bipolar transistor. The first terminal of the fourth switch S4, the fifth switch S5, and the sixth switch S6 can be the collector or emitter of the bipolar transistor, and correspondingly, the second terminal of the fourth switch S4, the fifth switch S5, and the sixth switch S6 can be the emitter or collector of the bipolar transistor. When the fourth switch S4, the fifth switch S5, and the sixth switch S6 are field-effect transistors (FETs), the control terminals of the fourth switch S4, the fifth switch S5, and the sixth switch S6 refer to the gate of the FET. The first terminal of the fourth switch S4, the fifth switch S5, and the sixth switch S6 can be the drain or source of the FET, and correspondingly, the second terminal of the fourth switch S4, the fifth switch S5, and the sixth switch S6 can be the source or drain of the FET.

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

[0145] The first driver U1 can transmit a shutdown signal OFF_O2 to the selection output circuit 121.

[0146] The second driver U2 can 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 S3 is turned off, keeping the on signal ON_O2 constantly low. This keeps the fifth switch S5 off, preventing the on signal ON_O2 from being transmitted to the selection output circuit 121. Consequently, the selection output circuit 121 stops outputting the on signal ON_O2. Under the action of the first control signal, the sixth switch S6 is turned off, preventing the off signal OFF_O2 from directly affecting the drive circuit 150, causing the selection output circuit 121 to stop outputting the off signal OFF_O2. Therefore, the drive signal output circuit 120 stops transmitting the off signal and the on signal to the drive circuit 150. Simultaneously, the third switch S3 remains off, preventing the voltage on the junction capacitance Cgs of the low-side power transistor M2 from dissipating through other paths.

[0148] Under the action of the fourth control signal, the third switch S3 is turned on, making the on signal ON_O2 not constantly low. Thus, the fifth switch S5 is always turned on, allowing the on signal ON_O2 to be transmitted to the selection output circuit 121. Then, under the action of the third control signal, the sixth switch S6 is turned on, short-circuiting the first diode D1, allowing the off signal OFF_O2 to directly affect the drive circuit 150, enabling the selection output circuit 121 to output the off signal OFF_O2. Therefore, the drive signal output circuit 120 can transmit both the off signal and the on signal to the drive circuit 150.

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

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

[0151] The seventh switch S7 in this application can be a bipolar transistor or a field-effect transistor, etc. For example, when the seventh switch S7 is a bipolar transistor, the control terminal of the seventh switch S7 refers to the base of the bipolar transistor, and the first terminal of the seventh switch S7 can be the collector or emitter of the bipolar transistor. Correspondingly, the second terminal of the seventh switch S7 can be the emitter or collector of the bipolar transistor. When the seventh switch S7 is a field-effect transistor, the control terminal of the seventh switch S7 refers to the gate of the field-effect transistor, and the first terminal of the seventh switch S7 can be the drain or source of the field-effect transistor. Correspondingly, the second terminal of the seventh switch S7 can be the source or drain of the field-effect transistor.

[0152] In this circuit, the first terminal of the field-effect transistor J1 is the input terminal of the charging circuit 110, the control terminal of the seventh switch S7 is the control terminal of the charging circuit 110, the cathode of the second diode D2 is the first output terminal of the charging circuit 110, and the cathode of the third diode D3 is the second output terminal of the charging circuit 110.

[0153] The field-effect transistor J1 can be a junction field-effect transistor (JFET) or a metal-oxide-semiconductor field-effect transistor (MOSFET), and this application does not specifically limit it.

[0154] When the field-effect transistor J1 is a junction field-effect transistor (JFET), its control terminal refers to the gate of the JFET. The first terminal can be either the drain or source of the JFET, and the corresponding second terminal can be either the source or drain of the JFET. When the field-effect transistor J1 is a metal-oxide-semiconductor (MOSFET), its control terminal refers to the gate of the MOSFET. The first terminal can be either the drain or source of the MOSFET, and the corresponding second terminal can be either the source or drain of the MOSFET.

[0155] Based on the description of the above embodiments, an exemplary possible implementation of the driving circuit 150 is provided. 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 inverting circuit 151.

[0156] The first terminal of the high-side power transistor M1 is connected to the power supply voltage VDD2. The control terminal of the high-side power transistor M1 is electrically connected to the output terminal of the level inverting circuit 151. The second terminal of the high-side power transistor M1 is electrically connected to the first terminal of the low-side power transistor M2. The gate terminal of the rectifier transistor Q1 is electrically connected between the second terminal of the high-side power transistor M1 and the first terminal of the low-side power transistor M2. The control terminal of the low-side power transistor M2 is electrically connected to the first output terminal of the charging circuit 110. The input terminal of the level inverting circuit 151 is electrically connected between the control terminal of the low-side power transistor M2 and the first output terminal of the charging circuit 110. The second terminal 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 drive circuit 150, and the output terminal of the drive 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 inverting circuit 151 can change 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] Specifically, if the voltage V_GATE2 at the control terminal of the low-side power transistor M2 is low, the level inverting circuit 151 can change the voltage V_GATE2 at the control terminal of the low-side power transistor M2 to high. If the voltage V_GATE2 at the control terminal of the low-side power transistor M2 is high, the level inverting circuit 151 can change the voltage V_GATE2 at the control terminal of the low-side power transistor M2 to low.

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

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

[0162] Among them, the output terminal of the level conversion module U4 is the output terminal of the level inverting circuit 151, and the input terminal of the NOT gate module U3 is the input terminal of the level inverting circuit 151.

[0163] The NOT gate module U3 can change the voltage level V_GATE2 at the control terminal of the low-side power transistor M2 to obtain the 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 shifting module U4 can enhance the drive strength of the first level to turn on or off the high-side power transistor M1.

[0165] In some examples, the drive circuit 150 may also include a Zener diode ZD.

[0166] The negative terminal of the 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, while the positive terminal of the Zener diode ZD is grounded.

[0167] By using the Zener diode ZD, the voltage across the junction capacitance Cgs of the low-side power transistor M2 is prevented from becoming too high. This, in turn, prevents the voltage V_GATE2 at the control terminal of the low-side power transistor M2 from becoming too high, thus preventing damage to the low-side power transistor M2.

[0168] The following is combined Figure 6 , Figure 6 It shows Figure 3 The schematic diagram of the control mode of the synchronous rectifier controller with clamping function enabled. (See diagram for example.) Figure 6 As shown, when the power supply voltage VDD2 is not established, the indicator signal VDD_OK2 is low, turning off the first switch S1. This results in a voltage V1 of 0V across the first capacitor C1, turning off the second, sixth, and seventh switches S2, S6, and S7. With the seventh switch S7 off, the drain 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, enabling the synchronous rectification controller 100 to perform its clamping function. Based on this, the voltage V_GATE1 at the control terminal of the low-side power transistor M2 rises rapidly, turning it on. Thus, the voltage at the output terminal DRV2 of the drive circuit 150 is clamped to a preset voltage, for example, 0V.

[0169] Simultaneously, the drain voltage VD2 of rectifier transistor Q1 charges the second capacitor C2 through field-effect transistor J1, third resistor R3, and third diode D3. Based on this, under the action of the off second switch S2, the second capacitor C2 is in a charging state, causing the voltage V2 on the second capacitor C2 to be established in a very short time. Thus, the established voltage V2 on the second capacitor C2, through the second voltage control voltage source VCVS2, turns on the third switch S3, keeping the on-state signal ON_O2 constantly low, preventing the on-state signal ON_O2 from controlling the low-side power transistor M2. Furthermore, the fifth switch S5 remains off, ensuring that the voltage on the junction capacitance Cgs of the low-side power transistor M2 does not leak through other paths. Moreover, under the action of the off sixth switch S6, the off-state signal OFF_O2 cannot directly act on the control terminal of the low-side power transistor M2. Since the power supply voltage VDD2 is not established, the supply voltage DVDD2 is also not established. Therefore, the off-state signal OFF_O2 cannot control the low-side power transistor M2.

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

[0171] The following is combined Figure 7 , Figure 7 It shows Figure 3 The schematic diagram of the control mode of the synchronous rectifier controller under the shutdown clamping function. (See diagram for example.) Figure 7 As shown, when the power supply voltage VDD2 is established, the indicator signal VDD_OK2 is high, turning on the first switch S1. The power supply voltage DVDD2 charges the first capacitor C1 through the first resistor R1, causing the voltage V1 on the first capacitor C1 to be established in a very short time. The established voltage V1 on the first capacitor C1, through the first voltage control voltage source VCVS1, turns on the second switch S2, the sixth switch S6, and the seventh switch S7. Under the action of the conducting seventh switch S7, the second diode D2 is short-circuited, preventing the junction capacitance Cgs of the low-side power transistor M2 from being charged, thus disabling the clamping function of the synchronous rectifier controller 100.

[0172] Under the action of the conducting second switch S2, the second capacitor C2 is in a discharging state and no longer in a charging state, causing the voltage V2 on the second capacitor C2 to drop to 0V. This turns off the third switch S3, allowing the ON_O2 signal to control the fifth switch S5, which in turn controls the low-side power transistor M2. Under the action of the conducting sixth switch S6, the first diode D1 is short-circuited, allowing the OFF_O2 signal to directly act on the control terminal of the low-side power transistor M2, thus controlling it. Based on this, the synchronous rectifier controller 100 is in normal operating condition.

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

[0174] Finally, it should be noted that the above embodiments are merely specific implementations of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A synchronous rectifier controller, characterized in that, The synchronous rectification controller is used in a switching power supply, which includes a rectifier transistor; the synchronous rectification controller includes a charging circuit, a drive signal output circuit, a first control circuit, a second control circuit, and a drive circuit. The input terminal of the first control circuit is used to receive an indication signal, which is used to indicate the establishment status of the power supply voltage of the synchronous rectifier controller. The output terminal of the first control circuit is electrically connected to the control terminal of the charging circuit, the first terminal of the drive signal output circuit, and the first terminal of the second control circuit, respectively. The input terminal of the charging circuit is electrically connected to the drain terminal of the rectifier transistor. The first output terminal of the charging circuit and the output terminal of the drive signal output circuit are both electrically connected to the input terminal of the drive circuit. The output terminal of the drive circuit is electrically connected to the gate terminal of the rectifier transistor. The second output terminal of the charging circuit is electrically connected to the second terminal of the second control circuit. The output terminal of the second control circuit is electrically connected to the second terminal of the drive signal output circuit. The first control circuit is configured 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 has not been established. The first control signal is used to instruct the drive circuit to activate 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, so as to turn on the low-side power transistor, and to charge the second control circuit so as to generate a second control signal. 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 conduct. 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 a turn-off signal to the drive circuit according to the first control signal, and to stop transmitting the turn-on signal to the drive circuit according to the second control signal. The turn-off signal is used to drive the rectifier transistor to turn off, so that the drive circuit can enable the clamping function. The driving circuit is used to clamp the voltage at the control terminal of the rectifier transistor to a preset voltage by using the conducting low-side power transistor after the clamping function is enabled.

2. The synchronous rectifier 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. The third control signal is used to instruct the driven circuit to turn off the clamping function. The charging circuit is also used to stop charging to the control terminal of the low-side power transistor according to the third control signal, so as to turn off the clamping function of the driving circuit, and to stop charging to the second control circuit, so as to generate a fourth control signal of the second control circuit, the fourth control signal being used to control the driving signal output circuit to output the conduction signal. The second control circuit is also used to transmit the fourth control signal to the drive signal output circuit; The drive signal output circuit is further configured to transmit the off signal to the drive circuit according to the third control signal, and to transmit the on signal to the drive circuit according to the fourth control signal; The driving circuit is configured to, after the clamping function is turned off, drive the rectifier transistor to turn off according to the turn-off signal, and drive the rectifier transistor to turn 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 switching transistor, a first capacitor, and a first voltage control voltage source; The first end of the first resistor is used to connect to the power supply voltage. The second end of the first resistor is electrically connected to the first end of the first switching transistor. The control end of the first switching transistor is used to connect to the indication signal. The second end of the first switching transistor 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 control voltage source are both electrically connected between the second end of the first switching transistor and the first end of the second resistor. The output end of the first voltage control voltage source is electrically connected to the control end of the charging circuit. The second end of the second resistor and the lower plate of the first capacitor are both grounded. The first voltage control voltage source is used to amplify the first voltage on the first capacitor to obtain an amplified first voltage, so that the first control circuit uses the amplified first voltage as the first control signal or the third control signal.

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

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

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

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

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

9. The synchronous rectification controller according to claim 8, characterized in that, The driving circuit also includes: a Zener diode; The negative terminal of the Zener 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 positive terminal of the Zener diode is grounded.

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

11. A synchronous rectification control method, characterized in that, The method is executed by a synchronous rectifier controller, which is applied in a switching power supply. The switching power supply includes a rectifier transistor. The synchronous rectifier controller includes a charging circuit, a drive signal output circuit, a first control circuit, a second control circuit, and a drive circuit. The output terminal of the first control circuit is electrically connected to the control terminal of the charging circuit, the first terminal of the drive signal output circuit, and the first terminal of the second control circuit, respectively. The input terminal of the charging circuit is electrically connected to the drain terminal of the rectifier transistor. The first output terminal of the charging circuit and the output terminal of the drive signal output circuit are both electrically connected to the input terminal of the drive circuit. The output terminal of the drive circuit is electrically connected to the gate terminal of the rectifier transistor. The second output terminal of the charging circuit is electrically connected to the second terminal of the second control circuit, and the output terminal of the second control circuit is electrically connected to the second terminal of the drive signal output circuit. The method includes: The input terminal of the first control circuit receives an indication signal, which is used to indicate the establishment status of the power supply voltage of the synchronous rectifier controller; when the indication signal indicates that the power supply voltage has not been 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, which is used to instruct the drive circuit to activate 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, so as to turn on the low-side power transistor, and charges the second control circuit so as to generate a second control signal. 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 conduct. The second control circuit transmits the second control signal to the drive signal output circuit; The drive signal output circuit stops transmitting the turn-off signal to the drive circuit according to the first control signal and stops transmitting the turn-on signal to the drive circuit according to the second control signal. The turn-off signal is used to drive the rectifier transistor to turn off so that the drive circuit can enable the clamping function. After the clamping function is enabled, the driving circuit uses the conducting low-side power transistor to clamp the voltage at 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. The third control signal is used to instruct the drive circuit to turn off the clamping function. According to the third control signal, the charging circuit stops charging the control terminal of the low-side power transistor so that the driving circuit turns off the clamping function and stops charging the second control circuit so that the second control circuit generates a fourth control signal, which is used to control the driving signal output circuit to output the turn-on signal. The second control circuit transmits the fourth control signal to the drive signal output circuit; The drive signal output circuit transmits the turn-off signal to the drive circuit according to the third control signal, and transmits the turn-on signal to the drive circuit according to the fourth control signal; After the clamping function is turned off, the driving circuit drives the rectifier transistor to turn off according to the turn-off signal, and drives the rectifier transistor to turn on according to the turn-on signal.

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

14. A control circuit, characterized in that, It includes a processor and a memory, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the synchronous rectification control method as described in claim 11 or 12.

15. A chip, characterized in that, Includes any one of the following: the synchronous rectifier controller as described in any one of claims 1-10, the switching power supply as described in claim 13, and the control circuit as described in claim 14.

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

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