Synchronous rectification turn-off control method and device adaptive to minimum turn-on time

Abstract

The invention relates to a synchronous rectification turn-off control method and device adaptive to minimum turn-on time. The method comprises the following steps: detecting a voltage signal between a drain electrode and a source electrode of a synchronous rectification MOS (Metal Oxide Semiconductor) tube in a conducting state of the synchronous rectification MOS tube in a power supply circuit; when the voltage is greater than the set voltage threshold value, opening an adaptive filtering time window; the length Tf of the adaptive filtering time window is equal to mi < n > (Tf, max, max (Tf, min, alpha * D / fsw)); from the starting time of the adaptive filtering time window, monitoring whether the duration of the voltage signal greater than the set voltage threshold reaches the minimum duration threshold; generating a first effective turn-off signal when the duration reaches a minimum duration threshold; when timing reaches Tf from the starting time of the adaptive filtering time window, generating a second effective turn-off signal; and a turn-off driving control signal is generated according to the first effective turn-off signal and the second effective turn-off signal, and the synchronous rectification MOS tube is controlled to be turned off. According to the scheme, the stable work of the synchronous rectification MOS tube under various frequency conditions is ensured, and the operation reliability of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of power supply circuit technology, and in particular to a synchronous rectification turn-off control method and apparatus with adaptive minimum turn-on time. Background Technology

[0002] Synchronous rectification technology has been widely used in power electronic devices such as switching power supplies and adapters to replace traditional Schottky diodes and reduce conduction losses. Existing synchronous rectification chips typically determine turn-on and turn-off by detecting the polarity of the voltage across the secondary MOSFET. However, at the moment the MOSFET turns on or off, due to the influence of transformer leakage inductance and parasitic parameters, short-term ringing or glitches often appear in the voltage signal. If not handled properly, this can lead to malfunctions of the synchronous rectification MOSFET. To avoid this, existing technologies generally set a fixed minimum turn-on time after the MOSFET turns on, ignoring the reverse voltage signal during this time, thereby preventing false turn-off caused by momentary ringing.

[0003] However, the fixed-time scheme has significant drawbacks: under low-frequency operating conditions, the ringing duration is relatively long, and the fixed minimum turn-on time is often insufficient to cover the interference range, easily causing the MOSFET to turn off prematurely; while under high-frequency operating conditions, the fixed time window may be too long, causing the MOSFET to remain on when it should be off, affecting the system's fast response and conversion efficiency. In other words, the fixed minimum turn-on time cannot simultaneously accommodate the ringing characteristics and conduction duration requirements at different operating frequencies, limiting the reliability and efficiency of the synchronous rectification circuit over a wide frequency range. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a synchronous rectification turn-off control method and apparatus with adaptive minimum turn-on time. By setting an adaptive minimum turn-on time filter window after the synchronous rectification MOSFET is turned on, transient ringing interference caused by leakage inductance and parasitic parameters can be effectively suppressed, avoiding erroneous turn-off of the synchronous rectification MOSFET. Simultaneously, the filter time is adaptively and dynamically adjusted according to the switching frequency and / or the secondary conduction time (which is related to the MOSFET's duty cycle). It is extended at low frequencies to cover long ringing times and shortened at high frequencies to ensure fast response, thereby achieving high-efficiency, stable, and reliable synchronous rectification control over a wide frequency range.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a synchronous rectification turn-off control method with adaptive minimum turn-on time, comprising:

[0006] In the power supply circuit, when the synchronous rectifier MOSFET is turned on, the voltage signal between the drain and source of the synchronous rectifier MOSFET is detected.

[0007] When the detected voltage signal exceeds a set voltage threshold, an adaptive filtering time window is activated; the length T of the adaptive filtering time window is... f =min(T) f,max ,max(T f,min ,α·D / f sw )); where T f,mix The preset lower limit of the filtering time; T f,max The preset upper limit of the filtering time; α is the shutdown protection response coefficient, which is a preset value; D is the duty cycle of the synchronous rectifier MOSFET; f sw This refers to the switching frequency of the power supply circuit.

[0008] Starting from the opening time of the adaptive filtering time window, monitor whether the duration for which the voltage signal is greater than a set voltage threshold reaches a minimum duration threshold; when the duration reaches the minimum duration threshold, generate a first effective shutdown signal;

[0009] When the timing reaches T from the start time of the adaptive filtering time window. f At that time, a second valid turn-off signal is generated;

[0010] A shutdown drive control signal is generated based on the first valid shutdown signal and the second valid shutdown signal to control the synchronous rectifier MOS transistor to turn off.

[0011] Preferred, T f,min =0.8μs; T f,max =1.6μs; α =2%-8%; the minimum duration threshold is 100ns.

[0012] Preferably, the adaptive filtering time window is not activated when the duration does not reach the minimum duration threshold.

[0013] Preferably, the set voltage threshold is greater than the on-state voltage drop VDS(on) of the synchronous rectifier MOSFET and less than the peak reverse current.

[0014] More preferably, the set voltage threshold is VDS(on) + 30mV.

[0015] In a second aspect, the present invention provides a synchronous rectification chip, comprising:

[0016] The detection module is used to detect the voltage signal VDS between the drain and source of the synchronous rectifier MOSFET in the power supply circuit when the synchronous rectifier MOSFET is turned on; when the detected voltage signal is greater than a set voltage threshold, an adaptive filtering time window timing start signal is generated, and the adaptive filtering time window timing start signal and the real-time VDS signal are sent to the leakage inductance filtering monitoring module.

[0017] The leakage inductance filter monitoring module is used to monitor whether the duration of the VDS signal being greater than a set voltage threshold reaches a minimum duration threshold after receiving the adaptive filter time window timing start signal; when the duration reaches the minimum duration threshold, a first effective shutdown signal is generated.

[0018] The leakage inductance filtering monitoring module is further configured to, upon receiving the adaptive filtering time window timing start signal, start the timing of the adaptive filtering time window, and when the timing reaches the length T of the adaptive filtering time window... f At that time, a second valid turn-off signal is generated; T f =min(T) f,max ,max(T f,min ,α·D / f sw )); where T f,mix The preset lower limit of the filtering time; T f,max The preset upper limit of the filtering time; α is the shutdown protection response coefficient, which is a preset value; D is the duty cycle of the synchronous rectifier MOSFET; f sw This refers to the switching frequency of the power supply circuit.

[0019] The leakage inductance filtering monitoring module is also used to generate a shutdown drive control signal based on the first effective shutdown signal and the second effective shutdown signal, and send it to the drive module.

[0020] The driving module is used to control the synchronous rectifier MOS transistor to turn off according to the received shutdown driving control signal.

[0021] Preferably, the synchronous rectification chip has two pins, namely pin A and pin K, wherein pin K is connected to the drain of the synchronous rectification MOS transistor, and pin A is connected to the source of the synchronous rectification MOS transistor; the synchronous rectification MOS transistor is an NMOS.

[0022] More preferably, the synchronous rectification chip further includes: an energy storage capacitor and a self-powered module;

[0023] The self-powered module is used to obtain energy from the rectifier node of the synchronous rectifier circuit to power the internal components of the synchronous rectifier chip.

[0024] The energy storage capacitor is used to stabilize the power supply inside the synchronous rectifier chip.

[0025] Preferably, the detection module is further configured to output a turn-on control signal to the drive module to maintain the synchronous rectifier MOSFET on before the drive module receives the turn-off drive control signal.

[0026] Thirdly, the present invention provides a power supply circuit, the power supply circuit including the synchronous rectification chip described in the second aspect above, or the power supply circuit executing the synchronous rectification shutdown control method with adaptive minimum turn-on time described in the first aspect above.

[0027] The adaptive minimum turn-on time synchronous rectification control method and apparatus provided in this invention can overcome the problem of existing technologies that use fixed delays to shield interference, but which are difficult to balance different operating frequencies (early turn-off is likely at low frequencies, while delayed turn-off may occur at high frequencies). When a reverse voltage signal is detected, this invention first activates a filtering window and determines its duration: if it is less than a minimum duration threshold (e.g., 100ns), it is considered an interference signal and is shielded; if it meets the minimum duration threshold, it is considered a valid turn-off signal and is transmitted to the drive module. Simultaneously, an adaptive control mechanism is used to dynamically adjust the length of the filtering window according to the switching frequency and / or the secondary conduction time (which is related to the MOSFET duty cycle). At high frequencies, the window is shortened to a minimum of approximately 0.8μs to improve turn-off speed; at low frequencies, it is extended to a maximum of approximately 1.6μs to ensure anti-interference capability. Through the synergistic effect of intelligent detection, leakage inductance filtering, and driving logic, the technical solution of this invention not only ensures the stable operation of synchronous rectifier MOSFETs under various frequency conditions, effectively avoids false turn-off caused by ringing, and achieves more accurate and reliable turn-off control, but also minimizes shielding time, improves the accuracy and response speed of turn-off control, and meets the needs of both high-frequency and low-frequency applications. Furthermore, it significantly reduces conduction losses, improves the overall conversion efficiency and operational reliability of the system, and is suitable for various applications such as adapters and power modules. Attached Figure Description

[0028] Figure 1 This is a block diagram of the internal structure of a synchronous rectifier chip provided in an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of an application circuit for a synchronous rectifier chip provided in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of another application circuit of the synchronous rectification chip provided in an embodiment of the present invention. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] In power supply circuits employing synchronous rectifier chips, the turn-on and turn-off of the synchronous rectifier diodes can be determined and controlled based on the drain-source voltage detection across the chip. This invention focuses on optimizing the turn-off control after the synchronous rectifier diodes are turned on: by introducing an adaptive minimum turn-on time mechanism, accurate identification of the turn-off timing is achieved. Accurate turn-off identification and judgment are crucial for power supply circuits. After turn-on, due to ringing oscillations caused by parasitic parameters, the voltage waveform may briefly return to above 0V, triggering an incorrect turn-off signal. To avoid misjudgment, traditional methods typically set a fixed minimum turn-on time or shielding time, but this often lacks compatibility under different frequency conditions. This invention employs an adaptive minimum turn-on time mechanism, dynamically adjusting the shielding time according to the circuit's operating state. This effectively avoids erroneous turn-off caused by ringing, achieving more accurate and reliable turn-off control, while minimizing the shielding time, improving the accuracy and response speed of turn-off control, and accommodating the needs of both high-frequency and low-frequency applications.

[0033] Therefore, embodiments of the present invention provide a synchronous rectification turn-off control method with adaptive minimum turn-on time. This method is implemented in... Figure 1 The synchronous rectifier chip shown is described below. To better understand the technical solution of this invention, the synchronous rectifier chip will be explained first.

[0034] The internal structure block diagram of the synchronous rectification chip used in this invention to implement the adaptive minimum turn-on time synchronous rectification turn-off control method is shown below. Figure 1 As shown, it includes: detection module 1, leakage inductance filtering monitoring module 2, drive module 3, synchronous rectifier MOSFET Q1, energy storage capacitor C1, and self-powered module 4. The connection relationships of each module and component are as follows: Figure 1 As shown in the image.

[0035] This synchronous rectification chip has two pins, A and K. Pin K is connected to the drain of the synchronous rectification MOSFET Q1, and pin A is connected to the source of the synchronous rectification MOSFET Q1. In this embodiment, the synchronous rectification MOSFET is an NMOS.

[0036] The self-powered module 4 is used to obtain energy from the rectifier node of the synchronous rectifier circuit to power the various modules and components inside the synchronous rectifier chip; the rectifier node mentioned here refers to the A terminal and K terminal connected to the synchronous rectifier circuit.

[0037] Energy storage capacitor C1 is used to stabilize the power supply inside the synchronous rectifier chip.

[0038] When the secondary winding or rectifier node of the transformer in the synchronous rectifier circuit is energized, a periodic voltage is generated at terminals A and K. The chip's self-powered module 4 draws energy from this rectifier node and generates the chip's internal operating voltage Vdd through voltage regulation. At the same time, the energy storage capacitor C1 smooths Vdd, suppresses transients, and supplies power to the control circuit for a short period of time.

[0039] Once Vdd reaches the set threshold, the following modules enter normal operating mode and begin sampling and judging the voltage signal VDS between the drain and source of the synchronous rectifier MOSFET Q1, i.e., the voltage at the A / K node.

[0040] Detection module 1 is used to detect the voltage signal VDS between the drain and source of synchronous rectifier MOSFET Q1 when Q1 is turned on in the power supply circuit. When VDS is detected to be greater than a set voltage threshold, an adaptive filtering time window timing start signal is generated and sent to leakage inductance filter monitoring module 2. At the same time, detection module 1 transmits the dynamic characteristics of voltage change (i.e., the real-time VDS signal) to leakage inductance filter monitoring module 2, providing the raw input for the judgment of the turn-off signal.

[0041] The leakage inductance filter monitoring module 2 is used to monitor whether the duration of the VDS signal being greater than the set voltage threshold reaches the minimum duration threshold after receiving the adaptive filter time window timing start signal; when the duration reaches the minimum duration threshold, a first effective shutdown signal is generated.

[0042] The leakage inductance filter monitoring module is also used to start the timing of the adaptive filtering time window after receiving the adaptive filtering time window timing start signal, and to start the timing when the timing reaches the length T of the adaptive filtering time window. f At that time, a second valid turn-off signal is generated. The length T of the adaptive filtering time window. f =min(T) f,max ,max(T f,min ,α·D / f sw )); where T f,mix The preset lower limit of the filtering time; T f,max The preset upper limit of the filtering time; α is the shutdown protection response coefficient, which is a preset value; D is the duty cycle of the synchronous rectifier MOSFET Q1; f sw This refers to the switching frequency of the power supply circuit.

[0043] The leakage inductance filtering monitoring module 2 is also used to generate a shutdown drive control signal based on the first effective shutdown signal and the second effective shutdown signal, and send it to the drive module 3.

[0044] The drive module 3 is used to control the synchronous rectifier MOSFET Q1 to turn off according to the received turn-off drive control signal.

[0045] In addition, the detection module 1 is also used to output a turn-on control signal to the drive module 3 to maintain the synchronous rectifier MOSFET Q1 on before the drive module 3 receives the turn-off drive control signal.

[0046] In the circuit structure of the synchronous rectification chip proposed in this invention, the voltage signal between the drain and source of the synchronous rectification MOSFET Q1 is first monitored by the detection module 1. When the drain voltage of the synchronous rectification MOSFET Q1 is detected to be lower than the output voltage, the detection module 1 determines that the synchronous rectification MOSFET Q1 has the conditions to be turned on, and continuously outputs a turn-on signal to the driving module 3, thereby driving the synchronous rectification MOSFET Q1 to be turned on. Afterwards, the output of the turn-on signal is maintained.

[0047] Based on this chip structure, module function, and control logic, the adaptive minimum turn-on time synchronous rectification turn-off control method proposed in this invention mainly includes the following steps:

[0048] Step 110: With the synchronous rectifier MOSFET in the power supply circuit in the on state, detect the voltage signal between the drain and source of the synchronous rectifier MOSFET.

[0049] Specifically, the voltage signal between the drain and source of the synchronous rectifier MOSFET is the voltage difference VKA between the A and K terminals of the synchronous rectifier MOSFET Q1, which is also known as VDS.

[0050] The detection process involves real-time sampling and monitoring of the amplitude and polarity of the voltage signal to obtain the voltage change curve over time. Through this detection process, voltage fluctuations, ringing, or reverse rising signals that may occur during the conduction of the MOSFET can be identified, providing basic data for determining the start-up and turn-off conditions of the subsequent filtering time window.

[0051] Step 120: When the detected voltage signal is greater than the set voltage threshold, the adaptive filtering time window is opened; otherwise, the adaptive filtering time window is not opened.

[0052] Here, the voltage threshold is set to be greater than the on-state voltage drop VDS(on) of the synchronous rectifier MOSFET and less than the peak reverse current. Preferably, the voltage threshold is set to VDS(on) + 10 to 50 mV, and more preferably, the voltage threshold is set to VDS(on) + 30 mV.

[0053] The set voltage threshold is a fixed reference voltage, pre-set in the chip's control logic, used to distinguish between normal on-state voltage drop and reverse current / leakage inductance oscillation, and to determine whether the drain of the synchronous rectifier MOSFET experiences possible reverse current or transient spikes. In this example, a value slightly larger than VDS(on) is preferred, taking into account factors such as noise, to avoid the on-state voltage drop itself triggering the opening of the adaptive filter time window.

[0054] The length T of the adaptive filtering time window f =min(T) f,max ,max(T f,min ,α·D / f sw )); where T f,mix The preset lower limit of the filtering time; T f,max The preset upper limit of the filtering time; α is the shutdown protection response coefficient, which is a preset value; D is the duty cycle of the synchronous rectifier MOSFET; f sw The switching frequency of the power supply circuit; preferably, T f,min =0.8μs; T f,max =1.6μs; α =2%-8%; minimum duration threshold is 100ns.

[0055] Because the secondary conduction time T on With switching frequency f sw Under a fixed duty cycle, there is an inverse proportional relationship: T on ≈D / f sw Therefore, it can also be written as T. f =min(T) f,max ,max(T f,min ,α·T on )).

[0056] This shows that the length of the adaptive filtering time window is dynamically adjusted according to the switching frequency or the secondary conduction time. In other words, the adaptive filtering time, which is the turn-off control shielding time after activation, is dynamically adjusted according to the switching frequency or the secondary conduction time.

[0057] Step 130: Starting from the opening time of the adaptive filtering time window, monitor whether the duration of the voltage signal being greater than the set voltage threshold has reached the minimum duration threshold; when the duration reaches the minimum duration threshold, generate the first valid shutdown signal; otherwise, do not generate the first valid shutdown signal and close the adaptive filtering time window.

[0058] Specifically, when the synchronous rectifier MOSFET Q1 is first turned on, due to the transformer leakage inductance and parasitic parameters, the voltage signal may experience a short-term ringing, manifested as a momentary rise to above 0V. If this signal is directly transmitted to the drive module, it will trigger the MOSFET to turn off erroneously. To avoid this problem, the leakage inductance filter monitoring module 2 does not immediately trigger shutdown when it detects a signal greater than the set voltage threshold. Instead, it activates a filter window with a minimum duration. Within this time window, if the voltage rise duration is less than the preset threshold (e.g., 100ns), it is considered ringing interference and ignored, and no shutdown signal is transmitted. Only when the signal duration exceeds the threshold is it considered a valid shutdown signal and sent to the drive module.

[0059] Step 140: When the timing reaches T from the start time of the adaptive filtering time window. f At that time, a second valid shutdown signal is generated.

[0060] Step 150: Generate a shutdown drive control signal based on the first valid shutdown signal and the second valid shutdown signal to control the synchronous rectifier MOSFET to turn off.

[0061] In other words, the present invention uses parallel logic to determine the generation of the shutdown drive control signal. The final shutdown drive control signal is only output when the first valid shutdown signal (from the leakage inductance filter module, indicating that a reverse / rising voltage event with a duration exceeding the short pulse threshold has occurred) and the second valid shutdown signal (indicating that the interval from the occurrence of the event exceeds the time specified by the adaptive filter time window) are logically overlapping and are both in a valid state.

[0062] The driver module outputs a valid turn-off signal to the gate of the synchronous rectifier MOSFET Q1, causing the synchronous rectifier MOSFET to turn off.

[0063] The key point of this method is that the filtering window is not a fixed value, but is dynamically adjusted according to the circuit switching frequency through an adaptive algorithm, i.e., the length T of the adaptive filtering time window. f =min(T) f,max ,max(T f,min ,α·D / f sw When the switching frequency is low, the conduction time of the synchronous rectifier MOSFET Q1 is longer, and the system automatically increases the length of the filtering window to cover the possible prolonged ringing process. When the switching frequency is high, the conduction time of the synchronous rectifier MOSFET Q1 becomes shorter, and the system automatically shortens the filtering time window to ensure timely detection and execution of the turn-off action. Through this adaptive control method, the filtering time T... fThe switching frequency or conduction period is proportionally adjusted within a range (e.g., 0.8μs to 1.6μs) to avoid false turn-off at low frequencies and ensure fast response at high frequencies.

[0064] The adaptive minimum turn-on time synchronous rectification control method and apparatus provided in this invention can overcome the problem of existing technologies that use fixed delays to shield interference, but which are difficult to balance different operating frequencies (early turn-off is likely at low frequencies, while delayed turn-off may occur at high frequencies). When a reverse voltage signal is detected, this invention first activates a filtering window and determines its duration: if it is less than a minimum duration threshold (e.g., 100ns), it is considered an interference signal and is shielded; if it meets the minimum duration threshold, it is considered a valid turn-off signal and is transmitted to the drive module. Simultaneously, an adaptive control mechanism is used to dynamically adjust the length of the filtering window according to the switching frequency and / or the secondary conduction time (which is related to the MOSFET duty cycle). At high frequencies, the window is shortened to a minimum of approximately 0.8μs to improve turn-off speed; at low frequencies, it is extended to a maximum of approximately 1.6μs to ensure anti-interference capability. Through the synergistic effect of intelligent detection, leakage inductance filtering, and drive logic, the technical solution of this invention not only ensures the stable operation of synchronous rectifier MOSFETs under various frequency conditions, effectively avoiding false turn-off caused by ringing and achieving more accurate and reliable turn-off control, but also minimizes shielding time, improving the accuracy and response speed of turn-off control, thus meeting the needs of both high-frequency and low-frequency applications. Furthermore, it significantly reduces conduction losses, improves the overall system conversion efficiency and operational reliability, and is suitable for various applications such as adapters and power modules. Figure 2 , Figure 3 In the power supply circuit shown.

[0065] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0066] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented in hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0067] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A synchronous rectification turn-off control method with adaptive minimum turn-on time, characterized in that, The method includes: In the power supply circuit, when the synchronous rectifier MOSFET is turned on, the voltage signal between the drain and source of the synchronous rectifier MOSFET is detected. When the detected voltage signal exceeds a set voltage threshold, an adaptive filtering time window is activated; the length T of the adaptive filtering time window is... f =min(T) f,max ,max(T f,min ,α·D / f sw )); where T f,mix The preset lower limit of the filtering time; T f,max The preset upper limit of the filtering time; α is the shutdown protection response coefficient, which is a preset value; D is the duty cycle of the synchronous rectifier MOSFET; f sw This refers to the switching frequency of the power supply circuit. Starting from the opening time of the adaptive filtering time window, monitor whether the duration for which the voltage signal is greater than a set voltage threshold reaches a minimum duration threshold; when the duration reaches the minimum duration threshold, generate a first effective shutdown signal; When the timing reaches T from the start time of the adaptive filtering time window. f At that time, a second valid turn-off signal is generated; A shutdown drive control signal is generated based on the first valid shutdown signal and the second valid shutdown signal to control the synchronous rectifier MOS transistor to turn off.

2. The adaptive minimum turn-on time synchronous rectification turn-off control method according to claim 1, characterized in that, T f,min =0.8μs; T f,max =1.6μs; α =2%-8%; the minimum duration threshold is 100ns.

3. The adaptive minimum turn-on time synchronous rectification turn-off control method according to claim 1, characterized in that, If the duration does not reach the minimum duration threshold, the adaptive filtering time window is not enabled.

4. The adaptive minimum turn-on time synchronous rectification turn-off control method according to claim 1, characterized in that, The set voltage threshold is greater than the on-state voltage drop VDS(on) of the synchronous rectifier MOSFET and less than the peak reverse current.

5. The adaptive minimum turn-on time synchronous rectification turn-off control method according to claim 4, characterized in that, The set voltage threshold is VDS(on) + 30mV.

6. A synchronous rectification chip, characterized in that, The synchronous rectification chip includes: The detection module is used to detect the voltage signal VDS between the drain and source of the synchronous rectifier MOSFET in the power supply circuit when the synchronous rectifier MOSFET is turned on; when the detected voltage signal is greater than a set voltage threshold, an adaptive filtering time window timing start signal is generated, and the adaptive filtering time window timing start signal and the real-time VDS signal are sent to the leakage inductance filtering monitoring module. The leakage inductance filter monitoring module is used to monitor whether the duration of the VDS signal being greater than a set voltage threshold reaches a minimum duration threshold after receiving the adaptive filter time window timing start signal; when the duration reaches the minimum duration threshold, a first effective shutdown signal is generated. The leakage inductance filtering monitoring module is further configured to, upon receiving the adaptive filtering time window timing start signal, start the timing of the adaptive filtering time window, and when the timing reaches the length T of the adaptive filtering time window... f At that time, a second valid turn-off signal is generated; T f =min(T) f,max ,max(T f,min ,α·D / f sw )); where T f,mix The preset lower limit of the filtering time; T f,max The preset upper limit of the filtering time; α is the shutdown protection response coefficient, which is a preset value; D is the duty cycle of the synchronous rectifier MOSFET; f sw This refers to the switching frequency of the power supply circuit. The leakage inductance filtering monitoring module is further configured to generate a shutdown drive control signal based on the first effective shutdown signal and the second effective shutdown signal, and send it to the drive module. The driving module is used to control the synchronous rectifier MOS transistor to turn off according to the received turn-off driving control signal.

7. The synchronous rectification chip according to claim 6, characterized in that, The synchronous rectification chip has two pins, namely pin A and pin K. Pin K is connected to the drain of the synchronous rectification MOS transistor, and pin A is connected to the source of the synchronous rectification MOS transistor. The synchronous rectification MOS transistor is an NMOS transistor.

8. The synchronous rectification chip according to claim 7, characterized in that, The synchronous rectification chip also includes: an energy storage capacitor and a self-powered module; The self-powered module is used to obtain energy from the rectifier node of the synchronous rectifier circuit to power the internal components of the synchronous rectifier chip. The energy storage capacitor is used to stabilize the power supply inside the synchronous rectifier chip.

9. The synchronous rectification chip according to claim 6, characterized in that, The detection module is also used to output a turn-on control signal to the drive module to maintain the synchronous rectifier MOS transistor on before the drive module receives the turn-off drive control signal.

10. A power supply circuit, characterized in that, The power supply circuit includes the synchronous rectification chip as described in any one of claims 6-9, or the power supply circuit executes the synchronous rectification shutdown control method with adaptive minimum turn-on time as described in any one of claims 1-5.

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