A digital control method and device for inhibiting shutdown stress of a synchronous rectification converter

Abstract

The application discloses a kind of digital control method and device for inhibiting synchronous rectifier converter shutdown stress, applied to synchronous rectifier converter, and synchronous rectifier converter is used to control the output rectification process of switching power supply, the digital control method includes: based on the preset digital control program continuously detects whether switching power supply appears fault;When determining that switching power supply appears fault, then wait for the drive rising edge signal of switch tube in synchronous rectifier converter;When receiving drive rising edge signal, based on the preset digital control program and the drive rising edge signal, close synchronous rectifier converter PWM control, and then inhibit synchronous rectifier converter shutdown stress.The application closes synchronous rectifier converter PWM control when the inductance current of synchronous rectifier converter is positive current, avoids the stress problem of synchronous rectifier tube caused by synchronous rectifier converter inductance negative current under no-load and light load conditions, and then can effectively inhibit synchronous rectifier converter shutdown stress.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, and in particular to a digital control method and device for suppressing shutdown stress of a synchronous rectifier converter. BACKGROUND

[0002] In recent years, switching power supplies are continuously evolving towards smaller size, higher efficiency and higher power density, and synchronous rectification technology has now been quite mature. Compared with ordinary diode rectification, synchronous rectification can greatly improve efficiency and is very suitable for low-voltage high-power application occasions, but it also brings certain problems. Due to the one-way conduction characteristic of diodes, the inductance in the synchronous rectifier converter will not have a negative current, but when synchronous rectification, the inductance will have a negative current when it is idle or lightly loaded, which may cause stress problems of the synchronous rectifier tube during shutdown of the synchronous rectifier converter. This phenomenon exists in many topologies, and in low-voltage high-power application occasions, the voltage stress problem caused by the large negative current of the inductance is particularly prominent.

[0003] Current methods to solve the shutdown stress problem of the synchronous rectifier converter include: using a soft shutdown method, that is, after detecting the shutdown signal, the reference voltage of the synchronous rectifier converter gradually decreases, and the output also gradually decreases under the regulation of the loop, the energy returns to the primary side, until the output decreases to 0V, and the PWM is turned off, at this time there is no energy in the inductance, and no stress problem will occur. However, in order to avoid damage to the subsequent circuit, the synchronous rectifier converter is triggered to immediately turn off the PWM, so this method does not conform to the actual engineering application. Using a method of increasing the absorption capacitor, that is, increasing the absorption capacitor can suppress the stress, but at the same time, the volume of the synchronous rectifier converter is increased, and the absorption capacitor will affect the peak stress in the heavy load condition during normal operation, causing the absorption circuit to heat up. Therefore, this method has high cost, low efficiency and poor effect. The above-mentioned methods for solving the shutdown stress problem of the synchronous rectifier converter cannot turn off the PWM when the shutdown stress is small, thereby causing poor effect of suppressing the shutdown stress of the synchronous rectifier converter and affecting the reliability and service life of the device. SUMMARY

[0004] The present application provides a digital control method and device for suppressing the shutdown stress of a synchronous rectifier converter to solve the above technical problems, which can effectively suppress the shutdown stress of the synchronous rectifier converter.

[0005] In order to solve the above technical problems, the present application provides a digital control method for suppressing the shutdown stress of a synchronous rectifier converter, applied to a synchronous rectifier converter for controlling the output rectification process of a switching power supply, which comprises:

[0006] Detecting whether the switching power supply is faulty based on a preset digital control program continuously;

[0007] When it is determined that the switching power supply is faulty, waiting for a driving rising edge signal of a switch tube in the synchronous rectification converter;

[0008] When the driving rising edge signal is received, closing the PWM control of the synchronous rectification converter based on the preset digital control program and the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectification converter.

[0009] The present application has the following advantages:

[0010] Compared with the prior art, the PWM cannot be closed when the shutdown stress of the synchronous rectification converter is small, resulting in poor suppression effect of the shutdown stress of the synchronous rectification converter. The present application continuously detects whether the switching power supply is faulty based on a preset digital control program. When it is determined that the switching power supply is faulty, a driving rising edge signal of a switch tube in the synchronous rectification converter is waited for. When the driving rising edge signal is received, the PWM control of the synchronous rectification converter is closed based on the driving, so that the PWM control of the synchronous rectification converter is closed when the inductor current of the synchronous rectification converter is positive current, thereby avoiding the problem of the stress of the synchronous rectification tube caused by the negative inductor current of the synchronous rectification converter under no-load and light-load conditions, and effectively suppressing the shutdown stress of the synchronous rectification converter.

[0011] As a preferred solution, the switch tube comprises a primary-side switch tube. When the driving rising edge signal is received, the PWM control of the synchronous rectification converter is closed based on the preset digital control program and the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectification converter, which comprises:

[0012] When the driving rising edge signal of the primary-side switch tube is received, the PWM control of the synchronous rectification converter is closed based on the preset digital control program after a preset delay time, thereby suppressing the shutdown stress of the synchronous rectification converter.

[0013] In the present preferred solution, when the driving rising edge signal of the primary-side switch tube is received, the PWM control of the synchronous rectification converter is closed after a preset delay time, so that the PWM control of the synchronous rectification converter is closed when the inductor current of the synchronous rectification converter is positive current, thereby avoiding the problem of the stress of the synchronous rectification tube caused by the negative inductor current of the synchronous rectification converter under no-load and light-load conditions, and effectively suppressing the shutdown stress of the synchronous rectification converter.

[0014] As a preferred solution, the digital control method for suppressing the shutdown stress of the synchronous rectification converter, the preset digital control program comprises a preset state interruption program and a preset period interruption program.

[0015] The method comprises the following steps: when it is determined that the switching power supply is faulty, waiting for a driving rising edge signal of a switch tube in the synchronous rectification converter, and including the following steps:

[0016] When it is determined that the switching power supply is faulty, obtaining a shutdown signal based on a preset state interruption program, and waiting for a driving rising edge signal of a switch tube in the synchronous rectification converter;

[0017] When the driving rising edge signal of the primary-side switch tube is received, closing the PWM control of the synchronous rectification converter based on a preset digital control program after a preset delay time is delayed, and thereby suppressing the shutdown stress of the synchronous rectification converter, and including the following steps:

[0018] The preset delay time is determined based on the topology structure of the synchronous rectification converter and a switching period of the synchronous rectification converter.

[0019] When the driving rising edge signal of the primary-side switch tube is received, closing the PWM control of the synchronous rectification converter based on the shutdown signal and a preset period interruption program after a preset delay time is delayed, and thereby suppressing the shutdown stress of the synchronous rectification converter.

[0020] In the above preferred solution, considering that the switching periods of synchronous rectification converters of different topologies are different, the preset delay time is determined based on the topology structure of the synchronous rectification converter and a switching period of the synchronous rectification converter, so that the digital control method for suppressing the shutdown stress of the synchronous rectification converter can be applied to all synchronous rectification converters.

[0021] It should be noted that the preset state interruption program and the preset period interruption program are two interruption processes in the DSP digital control program, and the preset state interruption program and the preset period interruption program realize corresponding functions based on a timer interruption request.

[0022] In the above preferred solution, when it is determined that the switching power supply is faulty, a shutdown signal is obtained based on a preset state interruption program, and a driving rising edge signal of a switch tube in the synchronous rectification converter is waited for, and when the driving rising edge signal of the primary-side switch tube is received, the PWM control of the synchronous rectification converter is closed based on the shutdown signal and a preset period interruption program after a preset delay time is delayed, and thereby the shutdown stress of the synchronous rectification converter is suppressed, the PWM control of the synchronous rectification converter is closed when the inductor current of the synchronous rectification converter is positive current, and the problem of the stress of the synchronous rectification tube caused by the negative inductor current of the synchronous rectification converter in the no-load and light-load conditions is avoided, and thereby the shutdown stress of the synchronous rectification converter can be effectively suppressed.

[0023] As a preferred solution, the switch tube further comprises a secondary-side switch tube; when receiving the drive rising edge signal, the synchronous rectifier PWM control is closed based on the preset digital control program and the drive rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier.

[0024] When receiving the drive rising edge signal of the secondary-side switch tube, the synchronous rectifier PWM control is closed based on the preset digital control program, thereby suppressing the shutdown stress of the synchronous rectifier.

[0025] In the preferred solution, when receiving the drive rising edge signal of the secondary-side switch tube, the synchronous rectifier PWM control is closed, which realizes closing the synchronous rectifier PWM control when the inductor current of the synchronous rectifier is positive current, avoids the stress problem of the synchronous rectifier tube caused by the negative inductor current of the synchronous rectifier under no-load and light-load conditions, and thereby effectively suppresses the shutdown stress of the synchronous rectifier.

[0026] As a preferred solution, the digital control method for suppressing the shutdown stress of the synchronous rectifier comprises a preset state interruption program and a preset period interruption program.

[0027] When determining that the switching power supply has a fault, the drive rising edge signal of the switch tube in the synchronous rectifier is waited for, comprising:

[0028] When determining that the switching power supply has a fault, a shutdown signal is obtained based on the preset state interruption program, and the drive rising edge signal of the switch tube in the synchronous rectifier is waited for.

[0029] When receiving the drive rising edge signal of the secondary-side switch tube, the synchronous rectifier PWM control is closed based on the preset digital control program, thereby suppressing the shutdown stress of the synchronous rectifier.

[0030] When receiving the drive rising edge signal of the secondary-side switch tube, the synchronous rectifier PWM control is closed based on the shutdown signal and the preset period interruption program, thereby suppressing the shutdown stress of the synchronous rectifier.

[0031] In the above preferred solution, when determining that the switching power supply has a fault, a shutdown signal is obtained based on the preset state interruption program, and the drive rising edge signal of the switch tube in the synchronous rectifier is waited for. When receiving the drive rising edge signal of the secondary-side switch tube, the synchronous rectifier PWM control is closed based on the shutdown signal and the preset period interruption program, thereby suppressing the shutdown stress of the synchronous rectifier. The synchronous rectifier PWM control is closed when the inductor current of the synchronous rectifier is positive current, which avoids the stress problem of the synchronous rectifier tube caused by the negative inductor current of the synchronous rectifier under no-load and light-load conditions, and thereby effectively suppresses the shutdown stress of the synchronous rectifier.

[0032] As a preferred solution, the digital control method for inhibiting shutdown stress of the synchronous rectifier converter further comprises:

[0033] If the driving rising edge signal is not received within the preset time interval, the original control state of the synchronous rectifier converter PWM is maintained.

[0034] It should be noted that the preset time interval can be set according to actual needs to avoid interfering with the normal operation of the synchronous rectifier converter when the driving rising edge signal is not received all the time.

[0035] In the preferred solution, when the driving rising edge signal is not received within the preset time interval, the original control state of the synchronous rectifier converter PWM is maintained, so as to ensure that the synchronous rectifier converter PWM control is closed only when the failure of the switching power supply is received and the driving rising edge signal is received, and precise control of closing the synchronous rectifier converter PWM control is realized.

[0036] Correspondingly, to solve the above technical problems, the application further provides a digital control device for inhibiting shutdown stress of a synchronous rectifier converter, which is applied to the synchronous rectifier converter for controlling the output rectification process of a switching power supply, and comprises a fault detection module, a signal acquisition module and a PWM control module.

[0037] The fault detection module is used to continuously detect whether the switching power supply fails based on a preset digital control program.

[0038] The signal acquisition module is used to wait for a driving rising edge signal of a switch tube in the synchronous rectifier converter when it is determined that the switching power supply fails.

[0039] The PWM control module is used to close the synchronous rectifier converter PWM control based on the preset digital control program and the driving rising edge signal when the driving rising edge signal is received, so as to inhibit the shutdown stress of the synchronous rectifier converter.

[0040] The application continuously detects whether the switching power supply fails based on a preset digital control program, waits for a driving rising edge signal of a switch tube in the synchronous rectifier converter when it is determined that the switching power supply fails, and closes the synchronous rectifier converter PWM control based on the driving rising edge signal when the driving rising edge signal is received, so as to close the synchronous rectifier converter PWM control when the inductor current of the synchronous rectifier converter is positive current, avoid the stress problem of the synchronous rectifier tube caused by the negative inductor current of the synchronous rectifier converter in the no-load and light-load conditions, and effectively inhibit the shutdown stress of the synchronous rectifier converter.

[0041] As a preferred solution, the switch tube comprises a primary-side switch tube; the PWM control module is configured to, when receiving a driving rising edge signal, turn off the synchronous rectifier PWM control based on a preset digital control program and the driving rising edge signal, thereby suppressing the synchronous rectifier shutdown stress, comprising:

[0042] The PWM control module is configured to, when receiving a driving rising edge signal of the primary-side switch tube, turn off the synchronous rectifier PWM control after delaying a preset delay time based on the preset digital control program, thereby suppressing the synchronous rectifier shutdown stress.

[0043] As a preferred solution, the preset digital control program comprises a preset state interruption program and a preset period interruption program.

[0044] The signal acquisition module is configured to, when determining that the switching power supply has a fault, wait for a driving rising edge signal of a switch tube in the synchronous rectifier, comprising:

[0045] When determining that the switching power supply has a fault, a shutdown signal is obtained based on the preset state interruption program, and a driving rising edge signal of a switch tube in the synchronous rectifier is waited for.

[0046] The PWM control module is configured to, when receiving a driving rising edge signal of the primary-side switch tube, turn off the synchronous rectifier PWM control after delaying a preset delay time based on the preset digital control program, thereby suppressing the synchronous rectifier shutdown stress, comprising:

[0047] The preset delay time is determined based on a synchronous rectifier topology structure and a synchronous rectifier switching period.

[0048] When receiving a driving rising edge signal of the primary-side switch tube, the synchronous rectifier PWM control is turned off after delaying a preset delay time based on the shutdown signal and the preset period interruption program, thereby suppressing the synchronous rectifier shutdown stress.

[0049] As a preferred solution, the PWM control module is further configured to, if no driving rising edge signal is received within a preset time interval, maintain a previous control state of the synchronous rectifier PWM. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 : a flowchart of a digital control method for suppressing a synchronous rectifier shutdown stress according to an embodiment of the present application;

[0051] Figure 2 : a circuit diagram of a full-bridge topology converter with a secondary-side full-bridge synchronous rectifier according to an embodiment of the present application;

[0052] Figure 3: The PWM driving waveform and current waveform diagram of the full-bridge topology converter with secondary side full-bridge synchronous rectification when the full-bridge topology converter is in no-load state are provided for the embodiment of the present application.

[0053] Figure 4 : The waveform diagram of the PWM control of the synchronous rectification converter when the first rectification stage is closed is provided for the embodiment of the present application.

[0054] Figure 5 : The waveform diagram of the PWM control of the synchronous rectification converter when the second rectification stage is closed is provided for the embodiment of the present application.

[0055] Figure 6 : The waveform diagram of the PWM control of the synchronous rectification converter when the first freewheeling stage is closed is provided for the embodiment of the present application.

[0056] Figure 7 : The waveform diagram of the PWM control of the synchronous rectification converter when the second freewheeling stage is closed is provided for the embodiment of the present application.

[0057] Figure 8 : The waveform diagram of the PWM control of the synchronous rectification converter based on the driving rising edge signal of the primary side switch tube is provided for the embodiment of the present application.

[0058] Figure 9 : The flowchart diagram of the PWM control of the synchronous rectification converter based on the driving rising edge signal of the primary side switch tube is provided for the embodiment of the present application.

[0059] Figure 10 : The waveform diagram of the PWM control of the synchronous rectification converter based on the driving rising edge signal of the secondary side switch tube is provided for the embodiment of the present application.

[0060] Figure 11 : The flowchart diagram of the PWM control of the synchronous rectification converter based on the driving rising edge signal of the secondary side switch tube is provided for the embodiment of the present application.

[0061] Figure 12 : The circuit diagram of the non-isolated Buck converter with single-end topology is provided for the embodiment of the present application.

[0062] Figure 13 : The PWM driving waveform and current waveform diagram of the non-isolated Buck converter with single-end topology when the non-isolated Buck converter is in no-load state are provided for the embodiment of the present application. DETAILED DESCRIPTION

[0063] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0064] Embodiment one

[0065] In order to solve the existing technical problems, the present application provides a digital control method and device for inhibiting shutdown stress of a synchronous rectifier converter, which can effectively inhibit the shutdown stress of the synchronous rectifier converter.

[0066] Please refer to Figure 1 , a flowchart of one embodiment of a digital control method for inhibiting shutdown stress of a synchronous rectifier converter provided by the present application.

[0067] The present application provides a digital control method for inhibiting shutdown stress of a synchronous rectifier converter, which is applied to a synchronous rectifier converter for controlling the output rectification process of a switching power supply.

[0068] As shown in Figure 1 , the digital control method for inhibiting shutdown stress of a synchronous rectifier converter comprises steps 101 to 103, specifically:

[0069] Step 101: continuously detecting whether a failure occurs in the switching power supply based on a preset digital control program;

[0070] Step 102: when it is determined that a failure occurs in the switching power supply, waiting for a drive rising edge signal of a switch tube in the synchronous rectifier converter;

[0071] Step 103: when the drive rising edge signal is received, closing the PWM control of the synchronous rectifier converter based on the preset digital control program and the drive rising edge signal, thereby inhibiting the shutdown stress of the synchronous rectifier converter.

[0072] Compared with the prior art which cannot close the PWM when the shutdown stress of the synchronous rectifier converter is small, resulting in poor inhibition effect of the shutdown stress of the synchronous rectifier converter, the present application continuously detects whether a failure occurs in the switching power supply based on a preset digital control program, when it is determined that a failure occurs in the switching power supply, waits for a drive rising edge signal of a switch tube in the synchronous rectifier converter, when the drive rising edge signal is received, closes the PWM control of the synchronous rectifier converter based on the drive, realizes closing the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is positive current, avoids the problem of the stress of the synchronous rectifier tube caused by the negative inductor current of the synchronous rectifier converter in the no-load and light-load conditions, and thereby can effectively inhibit the shutdown stress of the synchronous rectifier converter.

[0073] In the present application, the proposed digital control method for inhibiting shutdown stress of the synchronous rectifier converter is applicable to all types of synchronous rectifier converters, which can be single-ended topologies such as forward converter, BUCK converter and other single-ended topology synchronous rectifier converters, or double-ended topologies such as full-bridge converter, half-bridge converter, push-pull converter and other double-ended topology synchronous rectifier converters.

[0074] It should be noted that the faults of the switching power supply in the present application include overvoltage, overcurrent and overtemperature faults of the switching power supply.

[0075] The following embodiment takes a full-bridge topology converter with full-bridge synchronous rectification on the secondary side as an example to further illustrate the proposed digital control method for inhibiting shutdown stress of the synchronous rectifier converter.

[0076] The following please refer to Figure 2 and Figure 3 , Figure 2 the circuit diagram of the full-bridge topology converter with full-bridge synchronous rectification on the secondary side provided by the embodiment of the present application, Figure 3 the PWM drive waveform and current waveform diagram of the full-bridge topology converter with full-bridge synchronous rectification on the secondary side provided by the embodiment of the present application when the load is empty.

[0077] Figure 2 In the full-bridge topology converter with full-bridge synchronous rectification on the secondary side, the input voltage is Vin, the output voltage is Vo, and the transformer turns ratio is N:1; the switch tubes S1, S2, S3 and S4 are primary side switch tubes; the switch tubes SR1, SR2, SR3 and SR4 are secondary side switch tubes; the output inductor front-end voltage is VFF, the output inductor current is iL, and the input inductor current is im.

[0078] In the present embodiment, all switch tubes are MOS tubes.

[0079] As Figure 3As shown, under no-load steady-state conditions, the switching mode of a full-bridge topology converter with full-bridge synchronous rectification on the secondary side for half a cycle (Ts / 2) includes four stages: (1) In the t0-t1 stage, the primary side switches S1 and S4 are turned on, the secondary side switches SR1 and SR4 are turned on, and the secondary side switches SR2 and SR3 are turned off. Energy is transferred from the input end to the output end. This is the first rectification stage, and the output inductor current gradually decreases in the negative direction; (2) In the t1-t2 stage, the state of the switches remains unchanged. This is the second rectification stage, and the output inductor current turns positive and gradually increases; (3) In the t2-t3 stage, all the primary side switches are turned off, and all the secondary side switches are turned on. This is the first freewheeling stage, and the output inductor current decreases to zero in the positive direction; (4) In the t3-t4 stage, the state of the switches remains unchanged. This is the second freewheeling stage, and the output inductor current turns negative and gradually increases; The switching mode of the second half cycle is the same as above.

[0080] When a synchronous rectifier converter malfunctions and the PWM needs to be turned off, the PWM shutdown point is random and may occur at any time in the four stages mentioned above.

[0081] Please refer to the following. Figures 4 to 7 , Figures 4 to 7 The above four stages show the waveforms of the output inductor front-end voltage, output inductor current, and VDS waveform of the secondary switch when the synchronous rectifier converter PWM control is turned off.

[0082] like Figure 4 As shown, the synchronous rectifier converter PWM control is turned off during the t0-t1 stage: Before PWM is turned off, the VDS voltage of the secondary switch SR2 is Vin / N (N is the transformer turns ratio), the VDS voltage of the secondary switch SR1 is 0, and the output inductor current iL is negative; when PWM is turned off at this time, the negative current will charge the parasitic capacitance and snubber capacitance of the MOSFET, and the voltage at point VFF will rise from Vin / N until the negative current of the inductor is completely discharged; the increased voltage is ΔVa; since the initial VDS voltage of the secondary switch SR2 is Vin / N, its stress is Vin / N+ΔVa / 2, while the VDS voltage of the secondary switch SR1 rises from 0 to ΔVa / 2; then comes the resonance process of the magnetizing inductor, output inductor, and parasitic capacitance of the MOSFET; the turn-off in this interval leads to excessive stress, especially when PWM is turned off near the initial stage close to t0, the negative current is large, and the stress is the greatest.

[0083] like Figure 5As shown, the synchronous rectifier converter's PWM control is turned off during the t1-t2 phase: Before PWM is turned off, the VDS voltage of the secondary-side switch SR2 is Vin / N (N is the transformer turns ratio), the VDS voltage of the secondary-side switch SR1 is 0, and the output inductor current iL is positive. When PWM is turned off, due to the presence of the magnetizing inductor and the transformer magnetizing current, and since iL > im*N, the output inductor enters the freewheeling phase, and the VDS voltages of both secondary-side switches SR1 and SR2 are 0. When iL = im*N, the VDS voltage of the secondary-side switch SR1 rises and is clamped at Vin / N, while the VDS voltage of the secondary-side switch SR2 remains 0. Then, the output inductor current iL and the transformer magnetizing current both slowly decrease to 0. During this period, the output inductor and the parasitic capacitance of the MOSFETs resonate continuously. Afterward, the output inductor, the parasitic capacitances of each MOSFET, and the magnetizing inductor resonate together. During this interval, the stress on the synchronous rectifier is low and there is no risk in turning off PWM.

[0084] like Figure 6 As shown, the synchronous rectifier converter PWM control is turned off during the t2-t3 phase: Before PWM is turned off, the VDS voltage of secondary switch SR2 is 0, the VDS voltage of secondary switch SR1 is 0, and the inductor current is decreasing positively. When PWM is turned off, due to the presence of the magnetizing inductor and transformer magnetizing current, the VDS voltage of secondary switch SR1 is clamped at Vin / N, the VDS voltage of secondary switch SR2 is 0, the voltage across the inductor remains positive, and the current rises again. When iL = im*N, both the output inductor current iL and the transformer magnetizing current slowly decrease to 0. During this period, the output inductor and the parasitic capacitance of the MOSFETs resonate continuously. Afterwards, the output inductor, the parasitic capacitances of each MOSFET, and the magnetizing inductor resonate together. During this interval, the stress on the synchronous rectifier is low and there is no risk in turning off PWM.

[0085] like Figure 7 As shown, the synchronous rectifier converter PWM control is turned off during the t3-t4 stage: Before PWM is turned off, the VDS voltage of secondary switch SR2 is 0, the VDS voltage of secondary switch SR1 is 0, and the inductor current is rising negatively; when PWM is turned off at this time, the negative current will charge the parasitic capacitance and snubber capacitance of the MOSFET, and the voltage at VFF point will rise from 0 until the negative current of the inductor is completely discharged; the increased voltage is ΔVa; under ideal conditions, the stress of secondary switches SR1 and SR2 is ΔVa / 2; however, in reality, due to the presence of transformer magnetizing current, even when all MOSFETs are turned off, the transformer magnetizing current still needs to establish a path, resulting in the stress of secondary switch SR1 being Vin / N+ΔVa / 2 and the stress of secondary switch SR2 being ΔVa / 2; turning off in this interval will lead to excessive stress, especially when PWM is turned off near t4, the negative current is large, and the stress is the greatest.

[0086] From the above, when the synchronous rectifier converter works in no-load or light-load, there is negative current in the output inductor in the t0-t1 and t3-t4 stages, and closing the PWM will form high stress in the DS (drain to source) of one of the MOS tubes, which is easy to cause over-stress and damage. Based on this, the digital control method for suppressing the shutdown stress of the synchronous rectifier converter proposed in the application controls the PWM to close at the appropriate time, and controls the PWM to close at a certain time in the positive current interval of the inductor in the t1-t3 stage, so as to avoid the switch tube stress problem caused by the negative current of the inductor in the no-load and light-load conditions, and further effectively suppress the shutdown stress of the synchronous rectifier converter.

[0087] Further, the switch tube includes a primary side switch tube; and when the rising edge signal is received, the synchronous rectifier converter PWM control is closed based on the preset digital control program and the rising edge signal, so as to suppress the shutdown stress of the synchronous rectifier converter.

[0088] When the rising edge signal of the primary side switch tube is received, the synchronous rectifier converter PWM control is closed after a preset delay time based on the preset digital control program, so as to suppress the shutdown stress of the synchronous rectifier converter.

[0089] In the above scheme, when the rising edge signal of the primary side switch tube is received, the synchronous rectifier converter PWM control is closed after a preset delay time, so as to close the synchronous rectifier converter PWM control when the inductor current of the synchronous rectifier converter is positive, and avoid the synchronous rectifier tube stress problem caused by the negative current of the inductor of the synchronous rectifier converter in the no-load and light-load conditions, and further effectively suppress the shutdown stress of the synchronous rectifier converter.

[0090] In the above scheme, when the synchronous rectifier converter of the application is a full-bridge topology converter using full-bridge synchronous rectification in the secondary side, the preset delay time is 0.25Ts.

[0091] In the embodiment, for the full-bridge topology converter with the full-bridge synchronous rectifier in the secondary side, the input voltage range of the synchronous rectifier is [Vinmin, Vinmax], and the corresponding duty cycle is greater than 0 and less than 0.5, generally between 0.05-0.45; for Vinmin, the maximum duty cycle is 0.45, the output inductor current starts to be positive at 0.225Ts, and at 0.25Ts, it is in the t1-t2 stage, at this time, the synchronous rectifier PWM control is closed, and the stress problem will not be caused; for Vinmax, the minimum duty cycle is 0.05, the output inductor current starts to be negative at 0.275Ts, and at 0.25Ts, it is in the t2-t3 stage, at this time, the synchronous rectifier PWM control is closed, and the stress problem will not be caused; for the intermediate input voltage range greater than Vinmin and less than Vinmax, at 0.25Ts, it is in the t1-t3 stage; in addition, the smaller negative current will not cause large stress, even if there is some negative current at Vinmin, since the stress is only Vinmin / N, the peak stress will not be too large, therefore, the preset delay time can also be 0.25Ts±t, t is less than the preset limit value, that is, the time of closing the synchronous rectifier PWM control can be adjusted around 0.25Ts.

[0092] Please refer to Figure 8 , Figure 8 is the waveform diagram of the PWM control of the full-bridge topology converter with the full-bridge synchronous rectifier in the secondary side based on the driving rising edge signal of the primary side switch tube.

[0093] As Figure 8 shown, the fault is generated when the output inductor current is negative, and the PWM is closed at 0.25Ts, the stress of the synchronous rectifier tube is small, and the effective suppression of the shutdown stress of the synchronous rectifier is realized.

[0094] Further, the digital control method for suppressing the shutdown stress of the synchronous rectifier further comprises a preset state interrupt program and a preset period interrupt program.

[0095] When it is determined that the switching power supply has a fault, the driving rising edge signal of the switch tube in the synchronous rectifier is waited, and the driving rising edge signal of the switch tube in the synchronous rectifier is waited.

[0096] When it is determined that the switching power supply has a fault, the driving rising edge signal of the switch tube in the synchronous rectifier is waited, and the driving rising edge signal of the switch tube in the synchronous rectifier is waited.

[0097] When the driving rising edge signal of the primary side switch tube is received, the synchronous rectifier PWM control is closed after a delay of a preset delay time based on the preset digital control program, and the shutdown stress of the synchronous rectifier is suppressed, and the shutdown stress of the synchronous rectifier is suppressed, and the shutdown stress of the synchronous rectifier is suppressed.

[0098] The preset delay time is determined based on a topology structure of the synchronous rectifier and a switching period of the synchronous rectifier.

[0099] When the rising edge signal of the driving of the primary-side switch tube is received, the synchronous rectifier PWM control is closed after a preset delay time based on the shutdown signal and a preset period interrupt program, thereby suppressing the shutdown stress of the synchronous rectifier.

[0100] In the above scheme, considering that the switching periods of synchronous rectifiers of different topologies are different, the preset delay time is determined based on the topology structure of the synchronous rectifier and the switching period of the synchronous rectifier in the preferred scheme, so that the digital control method for suppressing the shutdown stress of the synchronous rectifier can be applied to all synchronous rectifiers.

[0101] In the above scheme, when the synchronous rectifier of the application is a full-bridge topology converter using full-bridge synchronous rectification on the secondary side, the preset delay time is 0.25Ts based on the topology structure and the switching period of the synchronous rectifier.

[0102] It should be noted that the preset state interrupt program and the preset period interrupt program in the above scheme are two interrupt processes in the DSP digital control program, and the preset state interrupt program and the preset period interrupt program realize corresponding functions based on the timer interrupt request.

[0103] In the embodiment, the preset state interrupt program is used for switching various working states of the synchronous rectifier, detecting faults and data processing, specifically including detecting overvoltage, overcurrent and overtemperature faults of the switching power supply; the preset period interrupt program has the highest priority and is used for loop calculation, closing the synchronous rectifier PWM control and executing the PWM register operation.

[0104] In the above scheme, the preset period interrupt program is a switching period interrupt triggered by the rising edge signal of the driving of the primary-side switch tube; through the switching period interrupt, the application can conveniently and accurately determine the time of closing the synchronous rectifier PWM control, thereby closing the synchronous rectifier PWM control when the inductor current of the synchronous rectifier is positive current, avoiding the problem of the stress of the synchronous rectifier tube caused by the negative inductor current of the synchronous rectifier under no-load and light-load conditions, and effectively suppressing the shutdown stress of the synchronous rectifier.

[0105] In the embodiment, when it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interruption program, and a rising edge signal of a driving of a switch tube in the synchronous rectifier transformer is waited for; when the rising edge signal of the driving of the primary side switch tube is received, the synchronous rectifier transformer PWM control is closed after a preset delay time based on the shutdown signal and a preset period interruption program, thereby suppressing the specific implementation process of the shutdown stress of the synchronous rectifier transformer, as shown in Figure 9 When the preset state interruption program detects the failure that the synchronous rectifier transformer PWM control needs to be closed, the PWM OFF FLAG flag bit is set to 1 (i.e. the shutdown signal is obtained); when the rising edge signal of the driving of the primary side switch tube is received, the preset period interruption program is triggered, the switch period interruption is entered, and the preset period interruption program first judges the state of the PWM OFF FLAG flag bit after the switch period interruption is entered; when the PWM OFF FLAG flag bit is 1, the time delay operation is performed based on the preset delay time, and then the synchronous rectifier transformer PWM control is immediately closed; when the synchronous rectifier transformer of the application is a full-bridge topology converter using full-bridge synchronous rectification on the secondary side, the preset delay time is 0.25Ts based on the topology structure and the switch period of the synchronous rectifier transformer.

[0106] In the above scheme, when it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interruption program, and a rising edge signal of a driving of a switch tube in the synchronous rectifier transformer is waited for; when the rising edge signal of the driving of the primary side switch tube is received, the synchronous rectifier transformer PWM control is closed after a preset delay time based on the shutdown signal and a preset period interruption program, thereby suppressing the specific implementation process of the shutdown stress of the synchronous rectifier transformer, as shown in

[0107] Further, the switch tube further includes a secondary side switch tube; when the driving rising edge signal is received, the synchronous rectifier transformer PWM control is closed based on the preset digital control program and the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier transformer.

[0108] When the driving rising edge signal of the secondary side switch tube is received, the synchronous rectifier transformer PWM control is closed based on the preset digital control program, thereby suppressing the shutdown stress of the synchronous rectifier transformer.

[0109] For the full-bridge topology converter with the full-bridge synchronous rectification of the secondary side, the rising edge of the driving signal of the secondary side switch tube is t2, and the synchronous rectification converter PWM control is closed at t2, so that the synchronous rectification converter PWM control is closed when the inductor current of the synchronous rectification converter is positive current, and the stress problem of the synchronous rectification tube caused by the negative inductor current of the synchronous rectification converter under no-load and light-load conditions is avoided, thereby effectively inhibiting the shutdown stress of the synchronous rectification converter.

[0110] Please refer to the following Figure 10 , Figure 10 is a waveform diagram of closing the PWM control of the full-bridge topology converter with the full-bridge synchronous rectification of the secondary side based on the driving rising edge signal of the secondary side switch tube.

[0111] As shown in Figure 10 , the fault is generated when the output inductor current is negative, and the PWM is closed at the rising edge of the secondary side switch tube SR2, that is, t2, the stress of the synchronous rectification tube is small, and the effective inhibition of the shutdown stress of the synchronous rectification converter is realized.

[0112] Further, the digital control method for inhibiting the shutdown stress of the synchronous rectification converter, the preset digital control program comprises a preset state interruption program and a preset period interruption program;

[0113] When it is determined that the switching power supply has a fault, the driving rising edge signal of the switch tube in the synchronous rectification converter is waited, comprising:

[0114] When it is determined that the switching power supply has a fault, the shutdown signal is obtained based on the preset state interruption program, and the driving rising edge signal of the switch tube in the synchronous rectification converter is waited;

[0115] When the driving rising edge signal of the secondary side switch tube is received, the synchronous rectification converter PWM control is closed based on the preset digital control program, and the shutdown stress of the synchronous rectification converter is inhibited, comprising:

[0116] When the driving rising edge signal of the secondary side switch tube is received, the synchronous rectification converter PWM control is closed based on the shutdown signal and the preset period interruption program, and the shutdown stress of the synchronous rectification converter is inhibited.

[0117] In the above scheme, when it is determined that the switching power supply has a fault, a shutdown signal is obtained based on a preset state interruption program, a rising edge signal of a drive of a switch tube in the synchronous rectifier transformer is waited for, when the rising edge signal of the drive of the switch tube in the secondary side is received, the synchronous rectifier transformer PWM control is closed based on the shutdown signal and the preset period interruption program, and then the shutdown stress of the synchronous rectifier transformer is suppressed, so that the synchronous rectifier transformer PWM control is closed when the inductance current of the synchronous rectifier transformer is positive current, the stress problem of the synchronous rectifier tube caused by the negative inductance current of the synchronous rectifier transformer under no-load and light-load conditions is avoided, and then the shutdown stress of the synchronous rectifier transformer can be effectively suppressed.

[0118] In the above scheme, the preset period interruption program is a switch period interruption triggered by the rising edge signal of the drive of the switch tube in the secondary side.

[0119] In the embodiment, when it is determined that the switching power supply has a fault, a shutdown signal is obtained based on a preset state interruption program, a rising edge signal of a drive of a switch tube in the synchronous rectifier transformer is waited for, when the rising edge signal of the drive of the switch tube in the secondary side is received, the synchronous rectifier transformer PWM control is closed based on the shutdown signal and the preset period interruption program, and then the shutdown stress of the synchronous rectifier transformer is suppressed, so that the synchronous rectifier transformer PWM control is closed when the inductance current of the synchronous rectifier transformer is positive current, the stress problem of the synchronous rectifier tube caused by the negative inductance current of the synchronous rectifier transformer under no-load and light-load conditions is avoided, and then the shutdown stress of the synchronous rectifier transformer can be effectively suppressed, and the specific implementation process is as follows: Figure 11 As shown in the figure, when the preset state interruption program detects a fault that needs to close the synchronous rectifier transformer PWM control, the PWM_OFF_FLAG flag bit is set to 1 (i.e. the shutdown signal is obtained); when the rising edge signal of the drive of the switch tube in the secondary side is received, the preset period interruption program is triggered, the switch period interruption is entered, and after entering the switch period interruption, the preset period interruption program first judges the state of the PWM_OFF_FLAG flag bit; when the PWM_OFF_FLAG flag bit is 1, the synchronous rectifier transformer PWM control is immediately closed.

[0120] Further, the digital control method for suppressing the shutdown stress of the synchronous rectifier transformer further comprises:

[0121] If the rising edge signal is not received within the preset time interval, the original control state of the synchronous rectifier transformer PWM is maintained.

[0122] It should be noted that the preset time interval can be set according to actual needs to avoid interfering with the normal work of the synchronous rectifier transformer when the rising edge signal is not received all the time.

[0123] In the above scheme, when the rising edge signal is not received within the preset time interval, the original control state of the synchronous rectifier transformer PWM is maintained, so as to ensure that the synchronous rectifier transformer PWM control is closed only when the switching power supply has a fault and the rising edge signal is received, and precise control of closing the synchronous rectifier transformer PWM control is realized.

[0124] Correspondingly, in order to solve the above technical problems, the application further provides a digital control device for inhibiting shutdown stress of a synchronous rectification converter, applied to a synchronous rectification converter for controlling an output rectification process of a switching power supply, comprising: a fault detection module, a signal acquisition module and a PWM control module.

[0125] The fault detection module is used to continuously detect whether a fault occurs in the switching power supply based on a preset digital control program.

[0126] The signal acquisition module is used to wait for a drive rising edge signal of a switch tube in the synchronous rectification converter when it is determined that a fault occurs in the switching power supply.

[0127] The PWM control module is used to close the PWM control of the synchronous rectification converter based on the preset digital control program and the drive rising edge signal when the drive rising edge signal is received, thereby inhibiting the shutdown stress of the synchronous rectification converter.

[0128] The application continuously detects whether a fault occurs in the switching power supply based on a preset digital control program, waits for a drive rising edge signal of a switch tube in the synchronous rectification converter when it is determined that a fault occurs in the switching power supply, and closes the PWM control of the synchronous rectification converter based on the drive rising edge signal when the drive rising edge signal is received, thereby closing the PWM control of the synchronous rectification converter when the inductor current of the synchronous rectification converter is positive current, avoiding the problem of stress of the synchronous rectification tube caused by negative inductor current of the synchronous rectification converter in the case of no load and light load, and effectively inhibiting the shutdown stress of the synchronous rectification converter.

[0129] Further, the switch tube comprises a primary side switch tube, and the PWM control module is used to close the PWM control of the synchronous rectification converter based on the preset digital control program and the drive rising edge signal when the drive rising edge signal is received, thereby inhibiting the shutdown stress of the synchronous rectification converter.

[0130] The PWM control module is used to close the PWM control of the synchronous rectification converter based on the preset digital control program after a preset delay time when the drive rising edge signal of the primary side switch tube is received, thereby inhibiting the shutdown stress of the synchronous rectification converter.

[0131] Further, the preset digital control program comprises a preset state interruption program and a preset period interruption program.

[0132] The signal acquisition module is used to wait for a drive rising edge signal of a switch tube in the synchronous rectification converter when it is determined that a fault occurs in the switching power supply.

[0133] When it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interruption program, and a rising edge signal of a switch tube in the synchronous rectifier is waited for;

[0134] The PWM control module is configured to, when receiving the rising edge signal of the primary side switch tube, turn off the PWM control of the synchronous rectifier based on a preset digital control program after a preset delay time, thereby suppressing the shutdown stress of the synchronous rectifier.

[0135] The preset delay time is determined based on the topology of the synchronous rectifier and a switching period of the synchronous rectifier.

[0136] When receiving the rising edge signal of the primary side switch tube, the PWM control of the synchronous rectifier is turned off based on the shutdown signal and a preset period interruption program after a preset delay time, thereby suppressing the shutdown stress of the synchronous rectifier.

[0137] Further, the PWM control module is further configured to, if no rising edge signal is received within a preset time interval, maintain the original control state of the PWM of the synchronous rectifier.

[0138] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0139] Compared with the prior art, the PWM cannot be turned off when the shutdown stress of the synchronous rectifier is small, resulting in poor suppression effect of the shutdown stress of the synchronous rectifier. The present application continuously detects whether the switching power supply fails based on a preset digital control program, waits for a rising edge signal of a switch tube in the synchronous rectifier when it is determined that the switching power supply fails, turns off the PWM control of the synchronous rectifier based on the rising edge signal, and turns off the PWM control of the synchronous rectifier when the inductor current of the synchronous rectifier is positive, thereby avoiding the problem of the stress of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier under no-load and light-load conditions, and effectively suppressing the shutdown stress of the synchronous rectifier.

[0140] Meanwhile, the present application does not require any additional detection circuit, and the digital control method for suppressing the shutdown stress of the synchronous rectifier proposed in the present application can be realized only by a DSP digital control method, so that the present method has higher flexibility and scalability, and the algorithm and parameters can be easily updated to adapt to the changing processing requirements, thereby realizing efficient and low-power signal control processing and saving circuit hardware cost.

[0141] Embodiment Two

[0142] The following embodiment takes a single-ended non-isolated Buck converter as an example to further illustrate the digital control method for suppressing the shutdown stress of the synchronous rectifier proposed in the present application.

[0143] Please refer to the following Figure 12 And Figure 13 , Figure 12 The circuit diagram of the single-ended topology non-isolated Buck converter provided by the embodiment of the application, Figure 13 The PWM drive waveform and current waveform diagram of the single-ended topology non-isolated Buck converter in the idle state provided by the embodiment of the application.

[0144] Figure 12 In the single-ended topology non-isolated Buck converter, the input voltage is Vin1, the output voltage is Vo1, the switch S11 is the primary side switch, the switch SR11 is the secondary side switch, and the output inductor current is iL1.

[0145] As Figure 13 shown, in the idle steady state, the switching mode of the single-ended topology non-isolated Buck converter also includes four stages: (1) in the t0-t1 stage, the output inductor current iL1 is gradually reduced in the negative direction; (2) in the t1-t2 stage, the output inductor current iL1 turns to the positive direction and gradually increases; (3) in the t2-t3 stage, the output inductor current iL1 decreases to zero in the positive direction; (4) in the t3-t4 stage, the output inductor current iL1 turns to the negative direction and gradually increases; thus it can be known that, for the single-ended topology non-isolated Buck converter, the output inductor current iL1 is in the positive direction in the t1-t3 interval, and closing the PWM in this interval will not cause stress problems.

[0146] The application provides a digital control method for suppressing shutdown stress of a synchronous rectification converter, which is applied to a synchronous rectification converter, the synchronous rectification converter being a single-ended topology non-isolated Buck converter, and is used for controlling the output rectification process of a switching power supply, and the digital control method for suppressing shutdown stress of the synchronous rectification converter comprises steps 101 to 103, and specifically comprises the following steps:

[0147] Step 101: continuously detecting whether the switching power supply appears a fault based on a preset digital control program;

[0148] Step 102: when it is determined that the switching power supply appears a fault, waiting for a drive rising edge signal of a switch tube in the synchronous rectification converter;

[0149] Step 103: when the drive rising edge signal is received, closing the PWM control of the synchronous rectification converter based on the preset digital control program and the drive rising edge signal, and then suppressing the shutdown stress of the synchronous rectification converter.

[0150] It should be noted that the fault of the switching power supply in the application includes overvoltage, overcurrent and overtemperature faults of the switching power supply.

[0151] Further, the switch tube comprises a primary side switch tube S11; when receiving a driving rising edge signal, the synchronous rectifier PWM control is closed based on a preset digital control program and the driving rising edge signal, thereby suppressing the synchronous rectifier shutdown stress, comprising:

[0152] When receiving the driving rising edge signal of the primary side switch tube S11, the synchronous rectifier PWM control is closed after delaying a preset delay time, thereby suppressing the synchronous rectifier shutdown stress.

[0153] In the above scheme, when receiving the driving rising edge signal of the primary side switch tube S11, the synchronous rectifier PWM control is closed after delaying a preset delay time, thereby achieving the closing of the synchronous rectifier PWM control when the synchronous rectifier inductor current is positive current, avoiding the problem of synchronous rectifier stress caused by synchronous rectifier inductor negative current in the no-load and light-load conditions, thereby effectively suppressing the synchronous rectifier shutdown stress.

[0154] It should be noted that the full-bridge topology converter with full-bridge synchronous rectification on the secondary side completes a current cycle in half a cycle, and the single-ended topology non-isolated Buck converter completes a current cycle in one cycle, therefore, the preset delay time corresponding to the single-ended topology non-isolated Buck converter is 0.5Ts, therefore, in the above scheme, when the synchronous rectifier of the present application is a single-ended topology non-isolated Buck converter, the preset delay time is 0.5Ts.

[0155] Further, the digital control method for suppressing the synchronous rectifier shutdown stress comprises a preset state interruption program and a preset period interruption program in the preset digital control program.

[0156] When determining that the switching power supply has a fault, the driving rising edge signal of the switch tube in the synchronous rectifier is waited, comprising:

[0157] When determining that the switching power supply has a fault, a shutdown signal is obtained based on the preset state interruption program, and the driving rising edge signal of the switch tube in the synchronous rectifier is waited.

[0158] When receiving the driving rising edge signal of the primary side switch tube S11, the synchronous rectifier PWM control is closed after delaying a preset delay time, thereby suppressing the synchronous rectifier shutdown stress, comprising:

[0159] The preset delay time is determined based on the topology structure of the synchronous rectifier and the switching period of the synchronous rectifier.

[0160] When the driving rising edge signal of the primary side switch tube S11 is received, the synchronous rectifier PWM control is closed after a preset delay time based on the shutdown signal and the preset period interrupt program, thereby suppressing the shutdown stress of the synchronous rectifier.

[0161] In the above scheme, when the synchronous rectifier of the application is a single-ended topology non-isolated Buck converter, the preset delay time is 0.5Ts based on the topology structure and switching period of the single-ended topology non-isolated Buck converter.

[0162] It should be noted that the preset state interrupt program and the preset period interrupt program in the above scheme are two interrupt processes in the DSP digital control program, and the preset state interrupt program and the preset period interrupt program realize corresponding functions based on the timer interrupt request.

[0163] In the embodiment, the preset state interrupt program is used to switch various working states of the synchronous rectifier, detect faults and process data, specifically including detecting overvoltage, overcurrent and overtemperature faults of the switching power supply; the preset period interrupt program has the highest priority and is used to perform loop calculation, close the synchronous rectifier PWM control and execute PWM register operation.

[0164] In the above scheme, the preset period interrupt program is a switching period interrupt triggered by the driving rising edge signal of the primary side switch tube S11; through the switching period interrupt, the application can conveniently and accurately determine the time of closing the synchronous rectifier PWM control, thereby closing the synchronous rectifier PWM control when the inductor current of the synchronous rectifier is positive current, avoiding the problem of synchronous rectifier stress caused by negative inductor current of the synchronous rectifier in no-load and light-load conditions, and effectively suppressing the shutdown stress of the synchronous rectifier.

[0165] In the embodiment, when it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interruption program, and a rising edge signal of a driving of a switch tube in the synchronous rectifier transformer is waited for; when the rising edge signal of the driving of the original side switch tube S11 is received, the synchronous rectifier transformer PWM control is closed after a preset delay time based on the shutdown signal and the preset period interruption program, and thus the specific implementation process of suppressing the shutdown stress of the synchronous rectifier transformer is: when the preset state interruption program detects the failure that the synchronous rectifier transformer PWM control needs to be closed, the PWM_OFF_FLAG flag bit is set to 1 (i.e. the shutdown signal is obtained); when the rising edge signal of the driving of the original side switch tube S11 is received, the preset period interruption program is triggered, the switch period interruption is entered, and the preset period interruption program first judges the state of the PWM_OFF_FLAG flag bit after the switch period interruption is entered; when the PWM_OFF_FLAG flag bit is 1, the time delay operation is performed based on the preset delay time, and then the synchronous rectifier transformer PWM control is immediately closed.

[0166] In the above scheme, when it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interruption program, and a rising edge signal of a driving of a switch tube in the synchronous rectifier transformer is waited for; when the rising edge signal of the driving of the original side switch tube S11 is received, the synchronous rectifier transformer PWM control is closed after a preset delay time based on the shutdown signal and the preset period interruption program, and thus the specific implementation process of suppressing the shutdown stress of the synchronous rectifier transformer is: when the preset state interruption program detects the failure that the synchronous rectifier transformer PWM control needs to be closed, the PWM_OFF_FLAG flag bit is set to 1 (i.e. the shutdown signal is obtained); when the rising edge signal of the driving of the original side switch tube S11 is received, the preset period interruption program is triggered, the switch period interruption is entered, and the preset period interruption program first judges the state of the PWM_OFF_FLAG flag bit after the switch period interruption is entered; when the PWM_OFF_FLAG flag bit is 1, the time delay operation is performed based on the preset delay time, and then the synchronous rectifier transformer PWM control is immediately closed.

[0167] Further, the switch tube further includes a secondary side switch tube SR11; and when the rising edge signal of the driving is received, the synchronous rectifier transformer PWM control is closed based on a preset digital control program and the rising edge signal of the driving, and thus the shutdown stress of the synchronous rectifier transformer is suppressed.

[0168] When the rising edge signal of the driving of the secondary side switch tube SR11 is received, the synchronous rectifier transformer PWM control is closed, and thus the shutdown stress of the synchronous rectifier transformer is suppressed.

[0169] For the full-bridge topology converter with the full-bridge synchronous rectification of the secondary side, the rising edge of the driving signal of the secondary side switch SR11 is t2, at t2, the synchronous rectification converter PWM control is closed without stress, therefore, when the driving rising edge signal of the secondary side switch SR11 is received, the synchronous rectification converter PWM control is closed, the synchronous rectification converter PWM control is closed when the inductor current of the synchronous rectification converter is positive current, the stress problem of the synchronous rectification tube caused by the negative inductor current of the synchronous rectification converter under the conditions of no load and light load is avoided, and the shutdown stress of the synchronous rectification converter can be effectively inhibited.

[0170] Further, the digital control method for inhibiting the shutdown stress of the synchronous rectification converter comprises a preset state interruption program and a preset period interruption program.

[0171] When it is determined that the switching power supply fails, the driving rising edge signal of the switch tube in the synchronous rectification converter is waited for.

[0172] When it is determined that the switching power supply fails, the shutdown signal is obtained based on the preset state interruption program, and the driving rising edge signal of the switch tube in the synchronous rectification converter is waited for.

[0173] When the driving rising edge signal of the secondary side switch SR11 is received, the synchronous rectification converter PWM control is closed based on the shutdown signal and the preset period interruption program, and the shutdown stress of the synchronous rectification converter is inhibited.

[0174] When the driving rising edge signal of the secondary side switch SR11 is received, the synchronous rectification converter PWM control is closed based on the shutdown signal and the preset period interruption program, and the shutdown stress of the synchronous rectification converter is inhibited.

[0175] In the above scheme, when it is determined that the switching power supply fails, the shutdown signal is obtained based on the preset state interruption program, and the driving rising edge signal of the switch tube in the synchronous rectification converter is waited for, when the driving rising edge signal of the secondary side switch SR11 is received, the synchronous rectification converter PWM control is closed based on the shutdown signal and the preset period interruption program, and the shutdown stress of the synchronous rectification converter is inhibited, the synchronous rectification converter PWM control is closed when the inductor current of the synchronous rectification converter is positive current, the stress problem of the synchronous rectification tube caused by the negative inductor current of the synchronous rectification converter under the conditions of no load and light load is avoided, and the shutdown stress of the synchronous rectification converter can be effectively inhibited.

[0176] In the above scheme, the preset period interruption program is a switching period interruption triggered by the driving rising edge signal of the secondary side switch SR11.

[0177] In the embodiment, when it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interruption program, and a rising edge signal of a driving of a switch tube in the synchronous rectifier transformer is waited for; when the rising edge signal of the driving of the secondary side switch tube SR11 is received, the synchronous rectifier transformer PWM control is closed based on the shutdown signal and a preset period interruption program, and then the specific implementation process of the synchronous rectifier transformer shutdown stress suppression is as follows: when the preset state interruption program detects the failure that the synchronous rectifier transformer PWM control needs to be closed, the PWM_OFF_FLAG flag bit is set to 1 (i.e., the shutdown signal is obtained); when the rising edge signal of the driving of the secondary side switch tube SR11 is received, the preset period interruption program is triggered, the switching period interruption is entered, and the preset period interruption program first judges the state of the PWM_OFF_FLAG flag bit after the switching period interruption is entered; when the PWM_OFF_FLAG flag bit is 1, the synchronous rectifier transformer PWM control is immediately closed.

[0178] Further, the digital control method for suppressing the synchronous rectifier transformer shutdown stress further comprises:

[0179] If the rising edge signal of the driving is not received within the preset time interval, the original control state of the synchronous rectifier transformer PWM is maintained.

[0180] It should be noted that the preset time interval can be set according to actual needs to avoid interfering with the normal work of the synchronous rectifier transformer when the rising edge signal of the driving is not received all the time.

[0181] In the above scheme, when the rising edge signal of the driving is not received within the preset time interval, the original control state of the synchronous rectifier transformer PWM is maintained, so as to ensure that the synchronous rectifier transformer PWM control is closed only when the switching power supply fails and the rising edge signal of the driving is received, and the precise control of the synchronous rectifier transformer PWM control is realized.

[0182] Compared with the prior art, the embodiment of the present application has the following beneficial effects:

[0183] Compared with the prior art, the PWM cannot be closed when the synchronous rectifier transformer shutdown stress is small, which leads to poor synchronous rectifier transformer shutdown stress suppression effect. The present application continuously detects whether the switching power supply fails based on a preset digital control program, waits for the rising edge signal of the driving of a switch tube in the synchronous rectifier transformer when it is determined that the switching power supply fails, and closes the synchronous rectifier transformer PWM control based on the driving, so as to realize the closing of the synchronous rectifier transformer PWM control when the synchronous rectifier transformer inductor current is positive current, avoid the synchronous rectifier tube stress problem caused by the synchronous rectifier transformer inductor negative current in the no-load and light-load conditions, and effectively suppress the synchronous rectifier transformer shutdown stress.

[0184] Meanwhile, the application does not need any additional detection circuit, and the digital control method of the application can realize the digital control method of suppressing the shutdown stress of the synchronous rectifier converter, so that the method has higher flexibility and scalability, and the algorithm and parameters can be conveniently updated to adapt to the changing processing requirements, so that efficient and low-power signal control processing can be realized, and the hardware cost of the circuit is saved.

[0185] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the application. It should be understood that the above description is only a specific embodiment of the application and is not intended to limit the protection scope of the application. It is particularly pointed out that any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A digital control method for suppressing shutdown stress in a synchronous rectifier converter, applied to a synchronous rectifier converter used to control the output rectification process of a switching power supply, characterized in that, This digital control method includes: The switching power supply is continuously monitored for faults based on a preset digital control program. When a fault is detected in the switching power supply, wait for the rising edge signal of the drive transistor in the synchronous rectifier converter. When a rising edge signal is received, the synchronous rectifier converter PWM control is turned off based on the preset digital control program and the rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier converter. The switching transistor includes a primary-side switching transistor; the step of shutting down the synchronous rectifier converter PWM control based on a preset digital control program and the driving rising edge signal when a driving rising edge signal is received, thereby suppressing the shutdown stress of the synchronous rectifier converter, includes: When the rising edge signal of the primary-side switching transistor is received, the synchronous rectifier converter PWM control is turned off after a preset delay time based on the preset digital control program, thereby suppressing the shutdown stress of the synchronous rectifier converter. The preset digital control program includes a preset state interrupt program and a preset periodic interrupt program; The step of waiting for the rising edge signal of the drive transistor in the synchronous rectifier converter when a fault is determined in the switching power supply includes: When a fault is detected in the switching power supply, a shutdown signal is obtained based on the preset state interrupt program, and the system waits for the rising edge signal of the drive transistor in the synchronous rectifier converter. When the rising edge signal of the primary-side switch is received, the synchronous rectifier converter PWM control is turned off after a preset delay time based on a preset digital control program, thereby suppressing the shutdown stress of the synchronous rectifier converter, including: The preset delay time is determined based on the synchronous rectifier converter topology and the synchronous rectifier converter switching cycle; When the rising edge signal of the primary-side switch is received, the synchronous rectifier converter PWM control is turned off after a preset delay time based on the shutdown signal and the preset periodic interrupt program, thereby suppressing the shutdown stress of the synchronous rectifier converter.

2. The digital control method for suppressing shutdown stress in a synchronous rectifier converter as described in claim 1, characterized in that, The switching transistor also includes a secondary switching transistor; the step of shutting down the synchronous rectifier converter PWM control based on a preset digital control program and the driving rising edge signal when a driving rising edge signal is received, thereby suppressing the shutdown stress of the synchronous rectifier converter, includes: When the rising edge signal of the drive of the secondary-side switch is received, the PWM control of the synchronous rectifier converter is turned off based on the preset digital control program, thereby suppressing the shutdown stress of the synchronous rectifier converter.

3. The digital control method for suppressing shutdown stress in a synchronous rectifier converter as described in claim 2, characterized in that, The preset digital control program includes a preset state interrupt program and a preset periodic interrupt program; The step of waiting for the rising edge signal of the drive transistor in the synchronous rectifier converter when a fault is determined in the switching power supply includes: When a fault is detected in the switching power supply, a shutdown signal is obtained based on the preset state interrupt program, and the system waits for the rising edge signal of the drive transistor in the synchronous rectifier converter. When the rising edge signal of the drive transistor on the secondary side is received, the synchronous rectifier converter PWM control is turned off based on a preset digital control program, thereby suppressing the shutdown stress of the synchronous rectifier converter, including: When the rising edge signal of the secondary-side switch is received, the synchronous rectifier converter PWM control is turned off based on the shutdown signal and the preset periodic interrupt program, thereby suppressing the shutdown stress of the synchronous rectifier converter.

4. The digital control method for suppressing shutdown stress in a synchronous rectifier converter as described in claim 1, characterized in that, Also includes: If no rising edge signal is received within the preset time interval, the original control state of the synchronous rectifier converter PWM will be maintained.

5. A digital control device for suppressing shutdown stress in a synchronous rectifier converter, applied to a synchronous rectifier converter used to control the output rectification process of a switching power supply, characterized in that, The digital control device includes: a fault detection module, a signal acquisition module, and a PWM control module; The fault detection module is used to continuously detect whether the switching power supply has a fault based on a preset digital control program. The signal acquisition module is used to wait for the rising edge signal of the drive transistor in the synchronous rectifier converter when it is determined that the switching power supply has failed. The PWM control module is used to shut down the PWM control of the synchronous rectifier converter based on a preset digital control program and the driving rising edge signal when a driving rising edge signal is received, thereby suppressing the shutdown stress of the synchronous rectifier converter. The switching transistor includes a primary-side switching transistor; the PWM control module is used to shut down the synchronous rectifier converter PWM control based on a preset digital control program and the driving rising edge signal when a driving rising edge signal is received, thereby suppressing the shutdown stress of the synchronous rectifier converter, including: The PWM control module is used to turn off the PWM control of the synchronous rectifier converter after a preset delay time based on a preset digital control program when it receives the rising edge signal of the primary-side switching transistor, thereby suppressing the shutdown stress of the synchronous rectifier converter. The preset digital control program includes a preset state interrupt program and a preset periodic interrupt program; The signal acquisition module is used to wait for the rising edge signal of the drive transistor in the synchronous rectifier converter when a fault is determined in the switching power supply, including: When a fault is detected in the switching power supply, a shutdown signal is obtained based on the preset state interrupt program, and the system waits for the rising edge signal of the drive transistor in the synchronous rectifier converter. The PWM control module, upon receiving the rising edge signal of the primary-side switching transistor, disables the PWM control of the synchronous rectifier converter after a preset delay time based on a preset digital control program, thereby suppressing the shutdown stress of the synchronous rectifier converter, including: The preset delay time is determined based on the synchronous rectifier converter topology and the synchronous rectifier converter switching cycle; When the rising edge signal of the primary-side switch is received, the synchronous rectifier converter PWM control is turned off after a preset delay time based on the shutdown signal and the preset periodic interrupt program, thereby suppressing the shutdown stress of the synchronous rectifier converter.

6. The digital control device for suppressing shutdown stress of a synchronous rectifier converter as described in claim 5, characterized in that, The PWM control module is also used to maintain the original PWM control state of the synchronous rectifier converter if no driving rising edge signal is received within a preset time interval.

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