Digital control method and device for suppressing shutdown stress of synchronous rectification converter

Abstract

The invention discloses a digital control method and device for suppressing shutdown stress of a synchronous rectification converter, applied to the synchronous rectification converter, the synchronous rectification converter is used for controlling an output rectification process of a switching power supply, and the digital control method comprises the following steps: continuously detecting whether the switching power supply has a fault based on a preset digital control program; waiting for a driving rising edge signal of a switching tube in the synchronous rectification converter when the switching power supply is determined to have a fault; when a driving rising edge signal is received, PWM control of the synchronous rectification converter is closed based on a preset digital control program and the driving rising edge signal, and then the shutdown stress of the synchronous rectification converter is restrained. According to the method, the PWM control of the synchronous rectification converter is closed when the inductive current of the synchronous rectification converter is positive current, the stress problem of a synchronous rectification tube caused by the inductive negative current of the synchronous rectification converter under the no-load and light-load conditions is avoided, and the shutdown stress of the synchronous rectification converter can be effectively inhibited.

Description

Technical Field

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

[0002] In recent years, switching power supplies have been continuously evolving towards being more miniaturized, efficient, and high power density, and synchronous rectification technology has now developed quite maturely; compared with ordinary diode rectification, synchronous rectification can greatly improve efficiency and is very suitable for applications with low-voltage and high-power outputs, but it also brings certain problems: due to the unidirectional conduction characteristic of the diode, the inductor in the synchronous rectifier converter will not have a negative current, but during synchronous rectification, the inductor will have a negative current when it is unloaded or lightly loaded, and this negative current may cause stress problems for the synchronous rectifier tube when the synchronous rectifier converter shuts down. This phenomenon exists in multiple topologies, and in applications with low-voltage and high-power outputs, due to the large negative current of the inductor, the resulting voltage stress problem is particularly prominent.

[0003] Current methods for solving the shutdown stress problem of synchronous rectifier converters include: adopting a soft turn-off 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, and the energy returns to the primary side until the output drops to 0V, and then the PWM is turned off. At this time, there is no energy in the inductor and no stress problem will occur. However, in order to avoid damaging the subsequent circuit, the synchronous rectifier converter hopes to immediately turn off the PWM when triggering many protections, so this method does not quite conform to the actual engineering application; adopting the method of increasing the absorption capacitor, that is, increasing the absorption capacitor can suppress the magnitude of the stress, but at the same time increases the volume of the synchronous rectifier converter, and at the same time this absorption capacitor will affect the peak stress in the heavy load condition during normal operation, resulting in the absorption circuit getting hot. Therefore, this method has high cost, low efficiency, and poor effect. The above methods for solving the shutdown stress problem of synchronous rectifier converters cannot turn off the PWM when the shutdown stress is small, resulting in a poor effect of suppressing the shutdown stress of the synchronous rectifier converter, and affecting the reliability and service life of the device. Summary of the Invention

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

[0005] To solve the above technical problems, the present invention provides a digital control method for suppressing the shutdown stress of a synchronous rectifier converter, which is applied to a synchronous rectifier converter. The synchronous rectifier converter is used to control the output rectification process of a switching power supply. The digital control method includes:

[0006] Continuously detect whether the switching power supply fails based on a preset digital control program;

[0007] When it is determined that the switching power supply fails, wait for the driving rising edge signal of the switching tube in the synchronous rectifier converter;

[0008] When the driving rising edge signal is received, based on the preset digital control program and the driving rising edge signal, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0009] The beneficial effects of the present invention are as follows:

[0010] Compared with the prior art that cannot turn off the PWM when the turn-off stress of the synchronous rectifier converter is small, resulting in a poor suppression effect on the turn-off stress of the synchronous rectifier converter, the present invention continuously detects whether the switching power supply fails based on a preset digital control program. When it is determined that the switching power supply fails, wait for the driving rising edge signal of the switching tube in the synchronous rectifier converter. When the driving rising edge signal is received, based on the driving, turn off the PWM control of the synchronous rectifier converter, realizing the turn-off of the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the turn-off stress of the synchronous rectifier converter.

[0011] As a preferred solution, the switching tube includes a primary switching tube; when the driving rising edge signal is received, based on the preset digital control program and the driving rising edge signal, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter, including:

[0012] When the driving rising edge signal of the primary switching tube is received, based on the preset digital control program, after delaying a preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0013] In this preferred solution, when the driving rising edge signal of the primary switching tube is received, after delaying a preset delay time, turn off the PWM control of the synchronous rectifier converter, realizing the turn-off of the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the turn-off stress of the synchronous rectifier converter.

[0014] As a preferred solution, for the digital control method for suppressing the turn-off stress of the synchronous rectifier converter, the preset digital control program includes a preset state interrupt program and a preset period interrupt program;

[0015] When it is determined that the switching power supply fails, wait for the driving rising edge signal of the switching tube in the synchronous rectifier converter, including:

[0016] When it is determined that the switching power supply fails, obtain a shutdown signal based on a preset state interrupt program, and wait for the driving rising edge signal of the switching tube in the synchronous rectifier converter;

[0017] When the driving rising edge signal of the primary switching tube is received, then based on a preset digital control program, after delaying a preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the shutdown stress of the synchronous rectifier converter, including:

[0018] Determine the preset delay time based on the topology of the synchronous rectifier converter and the switching period of the synchronous rectifier converter;

[0019] When the driving rising edge signal of the primary switching tube is received, then based on the shutdown signal and a preset periodic interrupt program, after delaying the preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the shutdown stress of the synchronous rectifier converter.

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

[0021] It should be noted that the preset state interrupt program and the preset periodic interrupt program in the above preferred solution are both two interrupt processes in the DSP digital control program, and the preset state interrupt program and the preset periodic interrupt program implement corresponding functions based on the timer interrupt request.

[0022] In the above preferred solution, when it is determined that the switching power supply fails, obtain a shutdown signal based on a preset state interrupt program, and wait for the driving rising edge signal of the switching tube in the synchronous rectifier converter. When the driving rising edge signal of the primary switching tube is received, then based on the shutdown signal and a preset periodic interrupt program, after delaying the preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the shutdown stress of the synchronous rectifier converter. This realizes turning off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the problem of synchronous rectifier stress caused by negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus can effectively suppress the shutdown stress of the synchronous rectifier converter.

[0023] As a preferred solution, the switching transistor further includes a secondary-side switching transistor; when receiving a driving rising-edge signal, based on a preset digital control program and the driving rising-edge signal, turning off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter, including:

[0024] When receiving the driving rising-edge signal of the secondary-side switching transistor, based on the preset digital control program, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0025] In this preferred solution, when receiving the driving rising-edge signal of the secondary-side switching transistor, turn off the PWM control of the synchronous rectifier converter, so as to turn off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the turn-off stress of the synchronous rectifier converter.

[0026] As a preferred solution, for the digital control method for suppressing the turn-off stress of the synchronous rectifier converter, the preset digital control program includes a preset state interrupt program and a preset cycle interrupt program;

[0027] When it is determined that the switching power supply fails, wait for the driving rising-edge signal of the switching transistor in the synchronous rectifier converter, including:

[0028] When it is determined that the switching power supply fails, obtain a turn-off signal based on the preset state interrupt program, and wait for the driving rising-edge signal of the switching transistor in the synchronous rectifier converter;

[0029] When receiving the driving rising-edge signal of the secondary-side switching transistor, based on the preset digital control program, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter, including:

[0030] When receiving the driving rising-edge signal of the secondary-side switching transistor, based on the turn-off signal and the preset cycle interrupt program, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0031] In the above preferred solution, when it is determined that the switching power supply fails, obtain a turn-off signal based on the preset state interrupt program, wait for the driving rising-edge signal of the switching transistor in the synchronous rectifier converter, and when receiving the driving rising-edge signal of the secondary-side switching transistor, based on the turn-off signal and the preset cycle interrupt program, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter, so as to turn off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the turn-off stress of the synchronous rectifier converter.

[0032] As a preferred solution, the digital control method for suppressing the turn-off stress of a synchronous rectifier converter further includes:

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

[0034] It should be noted that the preset time interval can be set according to actual requirements to avoid interfering with the normal operation of the synchronous rectifier converter due to the continuous non-receipt of the driving rising edge signal.

[0035] In this preferred solution, when a driving rising edge signal is not received within the preset time interval, the original control state of the PWM of the synchronous rectifier converter is maintained, so as to ensure that the PWM control of the synchronous rectifier converter is turned off only when a fault occurs in the switching power supply and the driving rising edge signal is received, realizing precise control of turning off the PWM control of the synchronous rectifier converter.

[0036] Correspondingly, to solve the above technical problems, the present invention also provides a digital control device for suppressing the turn-off stress of a synchronous rectifier converter, which is applied to the synchronous rectifier converter. The synchronous rectifier converter is used to control the output rectification process of the switching power supply. The digital control device includes: a fault detection module, a signal acquisition module, and a PWM control module;

[0037] Among them, 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;

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

[0039] The PWM control module is used to turn off the PWM control of the synchronous rectifier converter based on a preset digital control program and the driving rising edge signal when the driving rising edge signal is received, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0040] The present invention continuously detects whether a fault occurs in the switching power supply based on a preset digital control program, waits for the driving rising edge signal of the switching tube in the synchronous rectifier converter when it is determined that a fault occurs in the switching power supply, and turns off the PWM control of the synchronous rectifier converter based on the driving when the driving rising edge signal is received, realizing turning off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the turn-off stress of the synchronous rectifier converter.

[0041] As a preferred solution, the switching tube includes a primary switching tube; the PWM control module is configured to, when receiving a driving rising edge signal, based on a preset digital control program and the driving rising edge signal, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter, including:

[0042] When the PWM control module receives the driving rising edge signal of the primary switching tube, it turns off the PWM control of the synchronous rectifier converter after delaying a preset delay time based on a preset digital control program, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0043] As a preferred solution, the preset digital control program includes a preset state interrupt program and a preset cycle interrupt program;

[0044] When the signal acquisition module determines that a fault occurs in the switching power supply, it waits for the driving rising edge signal of the switching tube in the synchronous rectifier converter, including:

[0045] When it is determined that a fault occurs in the switching power supply, a turn-off signal is obtained based on a preset state interrupt program, and the driving rising edge signal of the switching tube in the synchronous rectifier converter is waited for;

[0046] When the PWM control module receives the driving rising edge signal of the primary switching tube, it turns off the PWM control of the synchronous rectifier converter after delaying a preset delay time based on a preset digital control program, thereby suppressing the turn-off stress of the synchronous rectifier converter, including:

[0047] Determine the preset delay time based on the topology of the synchronous rectifier converter and the switching cycle of the synchronous rectifier converter;

[0048] When receiving the driving rising edge signal of the primary switching tube, based on the turn-off signal and a preset cycle interrupt program, after delaying the preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0049] As a preferred solution, the PWM control module is further configured to maintain the original control state of the PWM of the synchronous rectifier converter if no driving rising edge signal is received within a preset time interval. Description of the Drawings

[0050] Figure 1 : is a schematic flowchart of a digital control method for suppressing the turn-off stress of a synchronous rectifier converter provided by an embodiment of the present invention;

[0051] Figure 2 : is a circuit diagram of a full-bridge topology converter with full-bridge synchronous rectification on the secondary side provided by an embodiment of the present invention;

[0052] Figure 3: PWM drive waveform and current waveform diagram of a full-bridge topology converter with full-bridge synchronous rectification on the secondary side provided by an embodiment of the present invention when no-load;

[0053] Figure 4 : A waveform diagram of closing the PWM control of the synchronous rectification converter in the first rectification stage provided by an embodiment of the present invention;

[0054] Figure 5 : A waveform diagram of closing the PWM control of the synchronous rectification converter in the second rectification stage provided by an embodiment of the present invention;

[0055] Figure 6 : A waveform diagram of the PWM control of the synchronous rectifier converter turned off in the first freewheeling stage provided by an embodiment of the present invention;

[0056] Figure 7 : A waveform diagram of the PWM control of the synchronous rectifier converter turned off in the second freewheeling stage provided by an embodiment of the present invention;

[0057] Figure 8 : A waveform diagram of PWM control of a synchronous rectifier converter closed by a driving rising edge signal of a primary switch tube according to an embodiment of the present invention;

[0058] Figure 9 : A schematic diagram of a process of shutting down a synchronous rectifier converter PWM control based on a driving rising edge signal of a primary switch tube according to an embodiment of the present invention;

[0059] Figure 10 : A waveform diagram of the PWM control of the synchronous rectifier converter closed based on the driving rising edge signal of the secondary side switch tube provided in an embodiment of the present invention;

[0060] Figure 11 : A schematic diagram of a process for shutting down a synchronous rectifier converter PWM control based on a driving rising edge signal of a secondary side switch tube according to an embodiment of the present invention;

[0061] Figure 12 : A circuit diagram of a non-isolated Buck converter with a single-ended topology provided in an embodiment of the present invention;

[0062] Figure 13 : PWM drive waveform and current waveform diagram of the no-load non-isolated Buck converter of the single-ended topology provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0063] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0064] Embodiment 1

[0065] To solve the existing technical problems, the present invention provides a digital control method and device for suppressing the turn-off stress of a synchronous rectifier converter, which can effectively suppress the turn-off stress of the synchronous rectifier converter.

[0066] Please refer to Figure 1 , which is a schematic flowchart of an embodiment of a digital control method for suppressing the turn-off stress of a synchronous rectifier converter provided by an embodiment of the present invention.

[0067] A digital control method for suppressing the turn-off stress of a synchronous rectifier converter provided by the present invention is applied to a synchronous rectifier converter, and the synchronous rectifier converter is used to control the output rectification process of a switching power supply.

[0068] As Figure 1 shown, the digital control method for suppressing the turn-off stress of the synchronous rectifier converter includes steps 101 to 103, specifically:

[0069] Step 101: Continuously detect whether the switching power supply fails based on a preset digital control program;

[0070] Step 102: When it is determined that the switching power supply fails, wait for the driving rising edge signal of the switching tube in the synchronous rectifier converter;

[0071] Step 103: When the driving rising edge signal is received, turn off the PWM control of the synchronous rectifier converter based on the preset digital control program and the driving rising edge signal, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0072] Compared with the prior art that cannot turn off the PWM when the turn-off stress of the synchronous rectifier converter is small, resulting in a poor suppression effect on the turn-off stress of the synchronous rectifier converter, the present invention continuously detects whether the switching power supply fails based on a preset digital control program. When it is determined that the switching power supply fails, it waits for the driving rising edge signal of the switching tube in the synchronous rectifier converter. When the driving rising edge signal is received, the PWM control of the synchronous rectifier converter is turned off based on the driving, realizing the turn-off of the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus effectively suppressing the turn-off stress of the synchronous rectifier converter.

[0073] In the present invention, the proposed digital control method for suppressing the turn-off stress of a synchronous rectifier converter is applicable to all types of synchronous rectifier converters. The synchronous rectifier converter can be a single-ended topology, such as a forward converter, a BUCK converter, etc., which are single-ended topology synchronous rectifier converters, or a double-ended topology, such as a full-bridge converter, a half-bridge converter, a push-pull converter, etc., which are double-ended topology synchronous rectifier converters.

[0074] It should be noted that the faults that occur in the switching power supply in the present invention include overvoltage, overcurrent, overheating, etc.

[0075] Next, taking the full-bridge topology converter with full-bridge synchronous rectification on the secondary side as an example, the digital control method for suppressing the turn-off stress of the synchronous rectifier converter proposed by the present invention will be further described.

[0076] Next, please refer to Figure 2 and Figure 3 , Figure 2 which is 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 invention. Figure 3 which is 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 invention when it is no-load.

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

[0078] In this embodiment, all the switching tubes are MOS tubes.

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

[0080] When a fault occurs in the synchronous rectification converter and the PWM needs to be turned off, the turn-off point of the PWM is random and may occur at any moment in the above four stages.

[0081] Please refer to the following Figures 4 to 7 , Figures 4 to 7 respectively, for the waveforms of the voltage at the front end of the output inductor, the output inductor current, and the VDS waveforms of the secondary-side switching transistors when the PWM control of the synchronous rectification converter is turned off in the above four stages.

[0082] As Figure 4 shown, when the PWM control of the synchronous rectification converter is turned off in the t0 - t1 stage: Before the PWM is turned off, the VDS voltage of the secondary-side switching transistor SR2 is Vin / N (N is the transformer turns ratio), the VDS voltage of the secondary-side switching transistor SR1 is 0, and the output inductor current iL is negative. When the PWM is turned off at this time, the negative current will charge the parasitic capacitance and the snubber capacitance of the MOS transistor, and the voltage at the VFF point rises from Vin / N to the point where all the negative inductor current is discharged. The increased voltage is ΔVa. Since the initial VDS voltage of the secondary-side switching transistor SR2 is Vin / N, its stress is Vin / N + ΔVa / 2, and the VDS voltage of the secondary-side switching transistor SR1 rises from 0 to ΔVa / 2. Then follows the resonance process of the magnetizing inductor, the output inductor, and the parasitic capacitance of the MOS transistor. Turning off within this interval results in excessive stress problems, especially when the PWM is turned off at the initial stage close to t0, where the negative current is large and the stress is the greatest.

[0083] As Figure 5As shown in the figure, the PWM control of the synchronous rectifier converter is turned off during the t1 - t2 stage: Before the PWM is turned off, the VDS voltage of the secondary - side switch tube SR2 is Vin / N (N is the transformer turns ratio), the VDS voltage of the secondary - side switch tube SR1 is 0, and the output inductor current iL is in the forward direction; at this time, when the PWM is turned off, due to the existence of the exciting inductor and the transformer exciting current, and at this time iL>im*N, the output inductor enters the free - wheeling stage, and the VDS voltages of the secondary - side switch tubes SR1 and SR2 are both 0; when iL = im*N, the VDS voltage of the secondary - side switch tube SR1 rises and is clamped at Vin / N, and the VDS voltage of the secondary - side switch tube SR2 remains 0, and then both the output inductor current iL and the transformer exciting current slowly decrease to 0. During this period, the output inductor and the MOS - tube parasitic capacitance are always in resonance. Then, the output inductor, the parasitic capacitances of each MOS - tube, and the exciting inductor resonate together. During this interval, turning off the PWM results in relatively low stress on the synchronous rectifier tube and there is no risk.

[0084] As Figure 6 shown, during the t2 - t3 stage, the PWM control of the synchronous rectifier converter is turned off: Before the PWM is turned off, the VDS voltage of the secondary - side switch tube SR2 is 0, the VDS voltage of the secondary - side switch tube SR1 is 0, and the inductor current is decreasing in the forward direction; at this time, when the PWM is turned off, due to the existence of the exciting inductor and the transformer exciting current, the VDS voltage of the secondary - side switch tube SR1 is clamped at Vin / N, the VDS voltage of the secondary - side switch tube SR2 is 0, the voltage across the inductor is still positive, and the current rises again. When iL = im*N, both the output inductor current iL and the transformer exciting current slowly decrease to 0. During this period, the output inductor and the MOS - tube parasitic capacitance are always in resonance. Then, the output inductor, the parasitic capacitances of each MOS - tube, and the exciting inductor resonate together; during this interval, turning off the PWM results in relatively low stress on the synchronous rectifier tube and there is no risk.

[0085] As Figure 7 shown, during the t3 - t4 stage, the PWM control of the synchronous rectifier converter is turned off: Before the PWM is turned off, the VDS voltage of the secondary - side switch tube SR2 is 0, the VDS voltage of the secondary - side switch tube SR1 is 0, and the inductor current is rising in the negative direction; at this time, when the PWM is turned off, the negative current will charge the parasitic capacitance and the snubber capacitance of the MOS - tube, and the voltage at the VFF point rises from 0 to the point where all the negative inductor current is discharged; the increased voltage is ΔVa; in an ideal state, the stresses of the secondary - side switch tubes SR1 and SR2 are both ΔVa / 2; but in reality, due to the existence of the transformer exciting current, when all MOS - tubes are turned off, the transformer exciting current still needs to establish a conduction path, resulting in the stress of the secondary - side switch tube SR1 being Vin / N + ΔVa / 2 and the stress of the secondary - side switch tube SR2 being ΔVa / 2; turning off during this interval will cause excessive stress problems, especially when turning off the PWM near the t4 moment, where the negative current is large and the stress is the greatest.

[0086] As can be seen from the above, when the synchronous rectifier converter operates under no-load or light-load conditions, negative current exists in the output inductor during the two stages of t0 - t1 and t3 - t4. At this time, turning off the PWM will generate a relatively high stress across the DS (drain - to - source) of one of the MOS transistors, which is likely to cause over - stress and damage. Based on this, the digital control method for suppressing the turn - off stress of the synchronous rectifier converter proposed in the present invention controls the PWM to turn off at an appropriate time, that is, controls the PWM to turn off at a certain moment within the positive - current interval of the inductor during t1 - t3, so as to avoid the switch - tube stress problem caused by the negative inductor current under no - load and light - load conditions, and thus can effectively suppress the turn - off stress of the synchronous rectifier converter.

[0087] Further, the switching transistor includes a primary - side switching transistor; when receiving a driving rising - edge signal, based on a preset digital control program and the driving rising - edge signal, turning off the PWM control of the synchronous rectifier converter, and further suppressing the turn - off stress of the synchronous rectifier converter, includes:

[0088] When receiving the driving rising - edge signal of the primary - side switching transistor, based on the preset digital control program, after delaying a preset delay time, turn off the PWM control of the synchronous rectifier converter, and further suppress the turn - off stress of the synchronous rectifier converter.

[0089] In the above - mentioned solution, when receiving the driving rising - edge signal of the primary - side switching transistor, after delaying the preset delay time, turn off the PWM control of the synchronous rectifier converter, realizing turning off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is positive current, avoiding the synchronous - rectifier stress problem caused by the negative inductor current of the synchronous rectifier converter under no - load and light - load conditions, and thus can effectively suppress the turn - off stress of the synchronous rectifier converter.

[0090] In the above - mentioned solution, when the synchronous rectifier converter of the present invention is a full - bridge topology converter with full - bridge synchronous rectification on the secondary side, the preset delay time is 0.25Ts.

[0091] In this embodiment, for a full-bridge topology converter with full-bridge synchronous rectification on the secondary side, the input voltage range of the synchronous rectification converter is [Vinmin, Vinmax], and the corresponding duty cycle is greater than 0 and less than 0.5, generally between 0.05 and 0.45; for Vinmin, the maximum duty cycle is 0.45. At 0.225Ts, the output inductor current starts to turn positive. At 0.25Ts, it is in the t1-t2 stage. At this time, the PWM control of the synchronous rectification converter is turned off, and no stress problem will occur; for Vinmax, the minimum duty cycle is 0.05. At 0.275Ts, the output inductor current starts to turn negative. At 0.25Ts, it is in the t2-t3 stage. At this time, the PWM control of the synchronous rectification converter is turned off, and no stress problem will occur; 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, a small negative current will not generate a 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, where t is less than the preset limit value, that is, the moment to turn off the PWM control of the synchronous rectification converter can be fine-tuned around 0.25Ts.

[0092] Please refer to the following Figure 8 , Figure 8 which is a waveform schematic diagram for turning off the PWM control of a full-bridge topology converter with full-bridge synchronous rectification on the secondary side based on the driving rising edge signal of the primary switching tube.

[0093] As Figure 8 shown, the fault occurs when there is a negative current in the output inductor, and the PWM is turned off at 0.25Ts. The stress on the synchronous rectification tube is small, effectively suppressing the shutdown stress of the synchronous rectification converter.

[0094] Furthermore, for the digital control method for suppressing the shutdown stress of the synchronous rectification converter, the preset digital control program includes a preset state interrupt program and a preset cycle interrupt program;

[0095] When it is determined that a fault occurs in the switching power supply, waiting for the driving rising edge signal of the switching tube in the synchronous rectification converter includes:

[0096] When it is determined that a fault occurs in the switching power supply, a shutdown signal is obtained based on the preset state interrupt program, and the driving rising edge signal of the switching tube in the synchronous rectification converter is waited for;

[0097] When the driving rising edge signal of the primary switching tube is received, after delaying the preset delay time based on the preset digital control program, the PWM control of the synchronous rectification converter is turned off, thereby suppressing the shutdown stress of the synchronous rectification converter, including:

[0098] Determine a preset delay time based on the synchronous rectifier converter topology and the switching period of the synchronous rectifier converter;

[0099] When the driving rising edge signal of the primary side switching tube is received, based on the shutdown signal and the preset periodic interrupt program, after delaying the preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the shutdown stress of the synchronous rectifier converter.

[0100] In the above solution, considering that the switching periods of synchronous rectifier converters with different topologies are different, the preset delay time in this preferred solution is determined based on the synchronous rectifier converter topology and the switching period of the synchronous rectifier converter, so that the digital control method for suppressing the shutdown stress of the synchronous rectifier converter proposed by the present invention can be applied to all synchronous rectifier converters.

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

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

[0103] In this embodiment, the preset state interrupt program is used to switch various working states of the synchronous rectifier converter, detect faults and process data, specifically including detecting faults such as overvoltage, overcurrent, and overtemperature of the switching power supply; the preset periodic interrupt program has the highest priority and is used for loop calculation, turning off the PWM control of the synchronous rectifier converter, and performing PWM register operations.

[0104] In the above solution, the preset periodic interrupt program is a switching period interrupt triggered by the driving rising edge signal of the primary side switching tube; through the switching period interrupt, the present invention can conveniently and accurately determine the moment to turn off the PWM control of the synchronous rectifier converter, so as to turn off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is positive current, avoiding the problem of synchronous rectifier stress caused by negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and effectively suppressing the shutdown stress of the synchronous rectifier converter.

[0105] In this embodiment, when it is determined that a fault occurs in the switching power supply, a shutdown signal is obtained based on a preset state interrupt program, and the driving rising edge signal of the switching transistor in the synchronous rectifier converter is waited for; when the driving rising edge signal of the primary switching transistor is received, based on the shutdown signal and a preset cycle interrupt program, after delaying a preset delay time, the PWM control of the synchronous rectifier converter is turned off, and the specific implementation process of suppressing the shutdown stress of the synchronous rectifier converter is as follows: As Figure 9 shown, when the preset state interrupt program detects a fault that requires turning off the PWM control of the synchronous rectifier converter, the PWM_OFF_FLAG flag bit is set to 1 (i.e., the shutdown signal is obtained); when the driving rising edge signal of the primary switching transistor is received, the preset cycle interrupt program is triggered to enter the switching cycle interrupt. After entering the switching cycle interrupt, the preset cycle interrupt program first judges the state of the PWM_OFF_FLAG flag bit. When the PWM_OFF_FLAG flag bit is 1, a time delay operation is performed based on the preset delay time, and then the PWM control of the synchronous rectifier converter is immediately turned off; when the synchronous rectifier converter of the present invention is a full-bridge topology converter with full-bridge synchronous rectification on the secondary side, based on the topology structure and switching cycle of the synchronous rectifier converter, the preset delay time is 0.25Ts.

[0106] In the above solution, when it is determined that a fault occurs in the switching power supply, a shutdown signal is obtained based on a preset state interrupt program, and the driving rising edge signal of the switching transistor in the synchronous rectifier converter is waited for. When the driving rising edge signal of the primary switching transistor is received, based on the shutdown signal and a preset cycle interrupt program, after delaying a preset delay time, the PWM control of the synchronous rectifier converter is turned off, thereby suppressing the shutdown stress of the synchronous rectifier converter, realizing turning off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus effectively suppressing the shutdown stress of the synchronous rectifier converter.

[0107] Further, the switching transistor further includes a secondary switching transistor; when the driving rising edge signal is received, turning off the PWM control of the synchronous rectifier converter based on a preset digital control program and the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier converter, includes:

[0108] When the driving rising edge signal of the secondary switching transistor is received, the PWM control of the synchronous rectifier converter is turned off based on a preset digital control program, thereby suppressing the shutdown stress of the synchronous rectifier converter.

[0109] For a full-bridge topology converter with full-bridge synchronous rectification on the secondary side, the rising edge of the driving signal of the secondary-side switching transistor is the moment t2. At moment t2, there is no stress when turning off the PWM control of the synchronous rectification converter. Therefore, in the present invention, when the rising-edge signal of the driving of the secondary-side switching transistor is received, the PWM control of the synchronous rectification converter is turned off, realizing the turning off of the PWM control of the synchronous rectification converter when the inductor current of the synchronous rectification converter is a positive current, avoiding the problem of the stress on the synchronous rectification transistors caused by the negative inductor current of the synchronous rectification converter under no-load and light-load conditions, and thus being able to effectively suppress the turn-off stress of the synchronous rectification converter.

[0110] Please refer to the following Figure 10 , Figure 10 which is a waveform schematic diagram of turning off the PWM control of a full-bridge topology converter with full-bridge synchronous rectification on the secondary side based on the rising-edge signal of the driving of the secondary-side switching transistor.

[0111] As Figure 10 shown, the fault occurs when the output inductor has a negative current, and the PWM is turned off at the rising edge of the secondary-side switching transistor SR2, that is, moment t2, with relatively small stress on the synchronous rectification transistors, realizing the effective suppression of the turn-off stress of the synchronous rectification converter.

[0112] Furthermore, for the digital control method for suppressing the turn-off stress of a synchronous rectification converter, the preset digital control program includes a preset state interruption program and a preset periodic interruption program;

[0113] When it is determined that a fault occurs in the switching power supply, waiting for the rising-edge signal of the driving of the switching transistors in the synchronous rectification converter includes:

[0114] When it is determined that a fault occurs in the switching power supply, a turn-off signal is obtained based on the preset state interruption program, and the rising-edge signal of the driving of the switching transistors in the synchronous rectification converter is waited for;

[0115] When the rising-edge signal of the driving of the secondary-side switching transistor is received, turning off the PWM control of the synchronous rectification converter based on the preset digital control program, and thus suppressing the turn-off stress of the synchronous rectification converter, includes:

[0116] When the rising-edge signal of the driving of the secondary-side switching transistor is received, the PWM control of the synchronous rectification converter is turned off based on the turn-off signal and the preset periodic interruption program, and thus the turn-off stress of the synchronous rectification converter is suppressed.

[0117] In the above solution, when it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interrupt program, and the rising edge signal of the drive of the switching tube in the synchronous rectifier converter is awaited. When the rising edge signal of the drive of the secondary-side switching tube is received, the PWM control of the synchronous rectifier converter is turned off based on the shutdown signal and a preset cycle interrupt program, thereby suppressing the shutdown stress of the synchronous rectifier converter. Specifically, when the inductor current of the synchronous rectifier converter is a positive current, the PWM control of the synchronous rectifier converter is turned off, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus effectively suppressing the shutdown stress of the synchronous rectifier converter.

[0118] In the above solution, the preset cycle interrupt program is a switching cycle interrupt triggered by the rising edge signal of the drive of the secondary-side switching tube.

[0119] In this embodiment, when it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interrupt program, and the rising edge signal of the drive of the switching tube in the synchronous rectifier converter is awaited. When the rising edge signal of the drive of the secondary-side switching tube is received, the PWM control of the synchronous rectifier converter is turned off based on the shutdown signal and a preset cycle interrupt program. The specific implementation process of suppressing the shutdown stress of the synchronous rectifier converter is as follows: Figure 11 As shown, when the preset state interrupt program detects a fault that requires turning off the PWM control of the synchronous rectifier converter, it will set the PWM_OFF_FLAG flag bit to 1 (i.e., obtain the shutdown signal). When the rising edge signal of the drive of the secondary-side switching tube is received, the preset cycle interrupt program will be triggered, entering the switching cycle interrupt. After entering the switching cycle interrupt, the preset cycle interrupt program will first judge the state of the PWM_OFF_FLAG flag bit. When the PWM_OFF_FLAG flag bit is 1, the PWM control of the synchronous rectifier converter will be immediately turned off.

[0120] Furthermore, the above digital control method for suppressing the shutdown stress of the synchronous rectifier converter further includes:

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

[0122] It should be noted that the preset time interval can be set according to actual requirements to avoid interfering with the normal operation of the synchronous rectifier converter due to the rising edge signal not being received all the time.

[0123] In the above solution, if the rising edge signal is not received within a preset time interval, the original PWM control state of the synchronous rectifier converter is maintained to ensure that the PWM control of the synchronous rectifier converter is turned off only when a fault in the switching power supply occurs and the rising edge signal is received, realizing precise control of turning off the PWM control of the synchronous rectifier converter.

[0124] Correspondingly, to solve the above technical problems, the present invention further provides a digital control device for suppressing the shutdown stress of a synchronous rectifier converter, which is applied to a synchronous rectifier converter. The synchronous rectifier converter is used to control the output rectification process of a switching power supply. The digital control device includes: a fault detection module, a signal acquisition module, and a PWM control module;

[0125] Among them, 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 the driving rising edge signal of the switching tube in the synchronous rectifier converter when it is determined that a fault occurs in the switching power supply;

[0127] The PWM control module is used to turn off the PWM control of the synchronous rectifier converter based on a preset digital control program and the driving rising edge signal when the driving rising edge signal is received, thereby suppressing the shutdown stress of the synchronous rectifier converter.

[0128] The present invention continuously detects whether a fault occurs in the switching power supply based on a preset digital control program, waits for the driving rising edge signal of the switching tube in the synchronous rectifier converter when it is determined that a fault occurs in the switching power supply, and turns off the PWM control of the synchronous rectifier converter based on the driving when the driving rising edge signal is received, so as to turn off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the shutdown stress of the synchronous rectifier converter.

[0129] Further, the switching tube includes a primary switching tube; the PWM control module is used to turn off the PWM control of the synchronous rectifier converter based on a preset digital control program and the driving rising edge signal when the driving rising edge signal is received, thereby suppressing the shutdown stress of the synchronous rectifier converter, including:

[0130] 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 the driving rising edge signal of the primary switching tube is received, thereby suppressing the shutdown stress of the synchronous rectifier converter.

[0131] Further, the preset digital control program includes a preset state interrupt program and a preset period interrupt program;

[0132] The signal acquisition module is used to wait for the driving rising edge signal of the switching tube in the synchronous rectifier converter when it is determined that a fault occurs in the switching power supply, including:

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

[0134] The PWM control module is used to, when receiving the rising edge signal of the drive of the primary switching tube, based on a preset digital control program, after delaying a preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the shutdown stress of the synchronous rectifier converter, and includes:

[0135] Determine the preset delay time based on the topology of the synchronous rectifier converter and the switching period of the synchronous rectifier converter;

[0136] When receiving the rising edge signal of the drive of the primary switching tube, based on the shutdown signal and a preset period interruption program, after delaying the preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the shutdown stress of the synchronous rectifier converter.

[0137] Furthermore, the PWM control module is also used to, if the rising edge signal of the drive is not received within a preset time interval, maintain the original control state of the PWM of the synchronous rectifier converter.

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

[0139] Compared with the prior art that cannot turn off the PWM when the shutdown stress of the synchronous rectifier converter is small, resulting in a poor suppression effect on the shutdown stress of the synchronous rectifier converter, the present invention continuously detects whether the switching power supply fails based on a preset digital control program, awaits the rising edge signal of the drive of the switching tube in the synchronous rectifier converter when it is determined that the switching power supply fails, and when receiving the rising edge signal of the drive, based on the drive, turn off the PWM control of the synchronous rectifier converter, realizing turning off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the shutdown stress of the synchronous rectifier converter.

[0140] At the same time, the present invention does not require any additional detection circuit, and only through the DSP digital control method can the digital control method for suppressing the shutdown stress of the synchronous rectifier converter proposed by the present invention be realized, making this method have higher flexibility and scalability, and can conveniently update the algorithm and parameters to adapt to the constantly changing processing requirements, thereby being able to realize efficient and low-power signal control processing and saving the circuit hardware cost.

[0141] Embodiment 2

[0142] Below, taking a single-ended topology non-isolated Buck converter as an example, this embodiment further illustrates the digital control method for suppressing the shutdown stress of the synchronous rectifier converter proposed by the present invention.

[0143] Please refer to the following Figure 12 and Figure 13 , Figure 12 which is the circuit diagram of the single-ended topology non-isolated Buck converter provided by the embodiment of the present invention, Figure 13 and which is the PWM drive waveform and current waveform diagram of the single-ended topology non-isolated Buck converter provided by the embodiment of the present invention under no-load condition.

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

[0145] As Figure 13 shown, under no-load steady-state condition, the switching modes of the single-ended topology non-isolated Buck converter also include four stages: (1) In the t0-t1 stage, the output inductor current iL1 decreases gradually in the negative direction; (2) In the t1-t2 stage, the output inductor current iL1 turns to the positive direction and increases gradually; (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 increases gradually; 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 turning off the PWM in this interval will not cause stress problems.

[0146] A digital control method for suppressing the turn-off stress of a synchronous rectifier converter provided by the present invention is applied to a synchronous rectifier converter, and the synchronous rectifier converter is a single-ended topology non-isolated Buck converter for controlling the output rectification process of a switching power supply. The digital control method for suppressing the turn-off stress of the synchronous rectifier converter includes steps 101 to 103, specifically:

[0147] Step 101: Continuously detect whether a fault occurs in the switching power supply based on a preset digital control program;

[0148] Step 102: When it is determined that a fault occurs in the switching power supply, wait for the driving rising edge signal of the switching transistor in the synchronous rectifier converter;

[0149] Step 103: When receiving the driving rising edge signal, turn off the PWM control of the synchronous rectifier converter based on the preset digital control program and the driving rising edge signal, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0150] It should be noted that the faults that occur in the switching power supply in the present invention include faults such as overvoltage, overcurrent, and overtemperature of the switching power supply.

[0151] Further, the switching transistor includes a primary switching transistor S11; when receiving a driving rising edge signal, based on a preset digital control program and the driving rising edge signal, turning off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter, includes:

[0152] When receiving the driving rising edge signal of the primary switching transistor S11, after delaying a preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter.

[0153] In the above solution, when receiving the driving rising edge signal of the primary switching transistor S11, after delaying a preset delay time, turn off the PWM control of the synchronous rectifier converter, realizing turning off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the turn-off stress of the synchronous rectifier converter.

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

[0155] Further, in the digital control method for suppressing the turn-off stress of the synchronous rectifier converter, the preset digital control program includes a preset state interrupt program and a preset period interrupt program;

[0156] When it is determined that the switching power supply fails, waiting for the driving rising edge signal of the switching transistor in the synchronous rectifier converter, includes:

[0157] When it is determined that the switching power supply fails, obtain a turn-off signal based on the preset state interrupt program, and wait for the driving rising edge signal of the switching transistor in the synchronous rectifier converter;

[0158] When receiving the driving rising edge signal of the primary switching transistor S11, after delaying a preset delay time, turn off the PWM control of the synchronous rectifier converter, thereby suppressing the turn-off stress of the synchronous rectifier converter, includes:

[0159] Determine the preset delay time based on the topology structure of the synchronous rectifier converter and the switching period of the synchronous rectifier converter;

[0160] When the driving rising edge signal of the primary side switch tube S11 is received, based on the shutdown signal and the preset periodic interruption program, after delaying for a preset delay time, the PWM control of the synchronous rectifier converter is turned off, thereby suppressing the shutdown stress of the synchronous rectifier converter.

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

[0162] It should be noted that the preset state interruption program and the preset periodic interruption program in the above solution are both two interruption processes in the DSP digital control program, and the preset state interruption program and the preset periodic interruption program implement corresponding functions based on the timer interruption request.

[0163] In this embodiment, the preset state interruption program is used to switch various working states of the synchronous rectifier converter, detect faults and process data, specifically including detecting faults such as overvoltage, overcurrent, and overtemperature of the switching power supply; the preset periodic interruption program has the highest priority and is used for loop calculation, turning off the PWM control of the synchronous rectifier converter, and performing PWM register operations.

[0164] In the above solution, the preset periodic interruption program is a switching period interruption triggered by the driving rising edge signal of the primary side switch tube S11; through the switching period interruption, the present invention can conveniently and accurately determine the moment to turn off the PWM control of the synchronous rectifier converter, so as to turn off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the problem of synchronous rectifier stress caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and effectively suppressing the shutdown stress of the synchronous rectifier converter.

[0165] In this embodiment, when it is determined that a fault occurs in the switching power supply, a shutdown signal is obtained based on a preset state interrupt program, and the driving rising edge signal of the switching tube in the synchronous rectifier converter is waited for; when the driving rising edge signal of the primary switching tube S11 is received, based on the shutdown signal and a preset cycle interrupt program, after delaying a preset delay time, the PWM control of the synchronous rectifier converter is turned off, and the specific implementation process of suppressing the shutdown stress of the synchronous rectifier converter is as follows: when the preset state interrupt program detects a fault that requires turning off the PWM control of the synchronous rectifier converter, the PWM_OFF_FLAG flag bit is set to 1 (i.e., the shutdown signal is obtained); when the driving rising edge signal of the primary switching tube S11 is received, the preset cycle interrupt program is triggered to enter the switching cycle interrupt. After entering the switching cycle interrupt, the preset cycle interrupt program first judges the state of the PWM_OFF_FLAG flag bit. When the PWM_OFF_FLAG flag bit is 1, a time delay operation is performed based on the preset delay time, and then the PWM control of the synchronous rectifier converter is immediately turned off.

[0166] In the above solution, when it is determined that a fault occurs in the switching power supply, a shutdown signal is obtained based on a preset state interrupt program, and the driving rising edge signal of the switching tube in the synchronous rectifier converter is waited for. When the driving rising edge signal of the primary switching tube S11 is received, based on the shutdown signal and a preset cycle interrupt program, after delaying a preset delay time, the PWM control of the synchronous rectifier converter is turned off, thereby suppressing the shutdown stress of the synchronous rectifier converter, realizing turning off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the shutdown stress of the synchronous rectifier converter.

[0167] Further, the switching tube further includes a secondary switching tube SR11; when the driving rising edge signal is received, turning off the PWM control of the synchronous rectifier converter based on a preset digital control program and the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier converter, includes:

[0168] When the driving rising edge signal of the secondary switching tube SR11 is received, the PWM control of the synchronous rectifier converter is turned off, thereby suppressing the shutdown stress of the synchronous rectifier converter.

[0169] For a full-bridge topology converter with full-bridge synchronous rectification on the secondary side, the rising edge of the driving signal of the secondary-side switching transistor SR11 is the moment t2. At moment t2, there is no stress when turning off the PWM control of the synchronous rectification converter. Therefore, in the present invention, when the rising-edge driving signal of the secondary-side switching transistor SR11 is received, the PWM control of the synchronous rectification converter is turned off, realizing the turn-off of the PWM control of the synchronous rectification converter when the inductor current of the synchronous rectification converter is a positive current, avoiding the stress problem of the synchronous rectification transistor caused by the negative inductor current of the synchronous rectification converter under no-load and light-load conditions, and thus being able to effectively suppress the turn-off stress of the synchronous rectification converter.

[0170] Further, in the digital control method for suppressing the turn-off stress of a synchronous rectification converter, the preset digital control program includes a preset state interrupt program and a preset period interrupt program;

[0171] The step of, when it is determined that a switching power supply fails, waiting for the rising-edge driving signal of the switching transistor in the synchronous rectification converter, includes:

[0172] When it is determined that a switching power supply fails, a turn-off signal is obtained based on the preset state interrupt program, and the rising-edge driving signal of the switching transistor in the synchronous rectification converter is waited for;

[0173] The step of, when the rising-edge driving signal of the secondary-side switching transistor SR11 is received, turning off the PWM control of the synchronous rectification converter, and thus suppressing the turn-off stress of the synchronous rectification converter, includes:

[0174] When the rising-edge driving signal of the secondary-side switching transistor SR11 is received, the PWM control of the synchronous rectification converter is turned off based on the turn-off signal and the preset period interrupt program, and thus the turn-off stress of the synchronous rectification converter is suppressed.

[0175] In the above solution, when it is determined that a switching power supply fails, a turn-off signal is obtained based on the preset state interrupt program, and the rising-edge driving signal of the switching transistor in the synchronous rectification converter is waited for. When the rising-edge driving signal of the secondary-side switching transistor SR11 is received, the PWM control of the synchronous rectification converter is turned off based on the turn-off signal and the preset period interrupt program, and thus the turn-off stress of the synchronous rectification converter is suppressed, realizing the turn-off of the PWM control of the synchronous rectification converter when the inductor current of the synchronous rectification converter is a positive current, avoiding the stress problem of the synchronous rectification transistor caused by the negative inductor current of the synchronous rectification converter under no-load and light-load conditions, and thus being able to effectively suppress the turn-off stress of the synchronous rectification converter.

[0176] In the above solution, the preset period interrupt program is a switching period interrupt triggered by the rising-edge driving signal of the secondary-side switching transistor SR11.

[0177] In this embodiment, when it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interruption program, and the driving rising edge signal of the switching tube in the synchronous rectifier converter is waited for; when the driving rising edge signal of the secondary switching tube SR11 is received, based on the shutdown signal and a preset period interruption program, the PWM control of the synchronous rectifier converter is turned off. The specific implementation process of suppressing the shutdown stress of the synchronous rectifier converter is as follows: when the preset state interruption program detects a fault that requires turning off the PWM control of the synchronous rectifier converter, the PWM_OFF_FLAG flag bit is set to 1 (i.e., the shutdown signal is obtained); when the driving rising edge signal of the secondary switching tube SR11 is received, the preset period interruption program is triggered, and the switching cycle interruption is entered. After entering the switching cycle 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 PWM control of the synchronous rectifier converter is immediately turned off.

[0178] Further, the digital control method for suppressing the shutdown stress of the synchronous rectifier converter further includes:

[0179] If the driving rising edge signal is not received within a preset time interval, the original PWM control state of the synchronous rectifier converter 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 operation of the synchronous rectifier converter due to the driving rising edge signal not being received all the time.

[0181] In the above solution, when the driving rising edge signal is not received within the preset time interval, the original PWM control state of the synchronous rectifier converter is maintained to ensure that the PWM control of the synchronous rectifier converter is turned off only when a fault in the switching power supply occurs and the driving rising edge signal is received, realizing precise control of turning off the PWM control of the synchronous rectifier converter.

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

[0183] Compared with the prior art that cannot turn off the PWM when the shutdown stress of the synchronous rectifier converter is small, resulting in a poor suppression effect on the shutdown stress of the synchronous rectifier converter, the present invention continuously detects whether the switching power supply fails based on a preset digital control program, waits for the driving rising edge signal of the switching tube in the synchronous rectifier converter when it is determined that the switching power supply fails, and when the driving rising edge signal is received, turns off the PWM control of the synchronous rectifier converter based on the driving, realizing turning off the PWM control of the synchronous rectifier converter when the inductor current of the synchronous rectifier converter is a positive current, avoiding the stress problem of the synchronous rectifier caused by the negative inductor current of the synchronous rectifier converter under no-load and light-load conditions, and thus being able to effectively suppress the shutdown stress of the synchronous rectifier converter.

[0184] Meanwhile, the present invention does not require any additional detection circuit, and only by means of the DSP digital control method can the digital control method for suppressing the turn-off stress of the synchronous rectifier converter proposed by the present invention be realized, making this method have higher flexibility and scalability, and can conveniently update the algorithm and parameters to adapt to the changing processing requirements, so as to be able to achieve efficient and low-power signal control processing and save the circuit hardware cost.

[0185] The specific embodiments described above have further detailed the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. In particular, it is pointed out that for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A digital control method for suppressing shutdown stress of a synchronous rectifier converter, applied to a synchronous rectifier converter, wherein the synchronous rectifier converter is used to control the output rectification process of a switching power supply, characterized in that: The digital control method includes: 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 fails, the driving rising edge signal of the switch tube in the synchronous rectifier converter is waited for; When a driving rising edge signal is received, the synchronous rectifier converter PWM control is turned off based on a preset digital control program and the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier converter.

2. A digital control method for suppressing shutdown stress of a synchronous rectifier converter as claimed in claim 1, characterized in that: The switch tube includes a primary switch tube; when receiving a driving rising edge signal, the synchronous rectifier converter PWM control is turned off based on a preset digital control program and the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier converter, including: When the driving rising edge signal of the primary switch tube 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.

3. A digital control method for suppressing shutdown stress of a synchronous rectifier converter as claimed in claim 2, characterized in that: The preset digital control program includes a preset state interrupt program and a preset cycle interrupt program; When it is determined that the switching power supply fails, waiting for a driving rising edge signal of a switch tube in a synchronous rectifier converter includes: When it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interrupt program, and a driving rising edge signal of the switch tube in the synchronous rectifier converter is waited for; When receiving the driving rising edge signal of the primary switch tube, 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: Determining a preset delay time based on a synchronous rectifier converter topology and a synchronous rectifier converter switching cycle; When the driving rising edge signal of the primary switch tube 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.

4. A digital control method for suppressing shutdown stress of a synchronous rectifier converter as claimed in claim 1, characterized in that: The switch tube also includes a secondary switch tube; when receiving a driving rising edge signal, the synchronous rectifier converter PWM control is turned off based on a preset digital control program and the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier converter, including: When the driving rising edge signal of the secondary side switch tube 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.

5. A digital control method for suppressing shutdown stress of a synchronous rectifier converter as claimed in claim 4, characterized in that: The preset digital control program includes a preset state interrupt program and a preset cycle interrupt program; When it is determined that the switching power supply fails, waiting for a driving rising edge signal of a switch tube in a synchronous rectifier converter includes: When it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interrupt program, and a driving rising edge signal of the switch tube in the synchronous rectifier converter is waited for; When the driving rising edge signal of the secondary side switch tube 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 driving rising edge signal of the secondary side switch tube 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.

6. A digital control method for suppressing shutdown stress of a synchronous rectifier converter as claimed in claim 1, characterized in that: Also includes: If the driving rising edge signal is not received within the preset time interval, the original control state of the synchronous rectification converter PWM is maintained.

7. A digital control device for suppressing shutdown stress of a synchronous rectifier converter, applied to a synchronous rectifier converter, wherein the synchronous rectifier converter is used to control the output rectification process of a switching power supply, characterized in that: The digital control device comprises: a fault detection module, a signal acquisition module and a PWM control module; Wherein, 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 driving rising edge signal of the switch tube in the synchronous rectifier converter when it is determined that the switch power supply fails; 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 receiving the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier converter.

8. A digital control device for suppressing shutdown stress of a synchronous rectifier converter as claimed in claim 7, characterized in that: The switch tube includes a primary switch tube; 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 receiving the driving rising edge signal, thereby suppressing the shutdown stress of the synchronous rectifier converter, including: The PWM control module is used to shut down the synchronous rectifier converter PWM control after a preset delay time based on a preset digital control program when receiving the driving rising edge signal of the primary switch tube, thereby suppressing the shutdown stress of the synchronous rectifier converter.

9. A digital control device for suppressing shutdown stress of a synchronous rectifier converter as claimed in claim 8, characterized in that: The preset digital control program includes a preset state interrupt program and a preset cycle interrupt program; The signal acquisition module is used to wait for the driving rising edge signal of the switch tube in the synchronous rectifier converter when it is determined that the switching power supply fails, including: When it is determined that the switching power supply fails, a shutdown signal is obtained based on a preset state interrupt program, and a driving rising edge signal of the switch tube in the synchronous rectifier converter is waited for; The PWM control module is used to turn off the synchronous rectifier converter PWM control after a preset delay time based on a preset digital control program when receiving the driving rising edge signal of the primary switch tube, thereby suppressing the shutdown stress of the synchronous rectifier converter, including: Determining a preset delay time based on a synchronous rectifier converter topology and a synchronous rectifier converter switching cycle; When the driving rising edge signal of the primary switch tube 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.

10. A digital control device for suppressing shutdown stress of a synchronous rectifier converter as claimed in claim 7, characterized in that: The PWM control module is also used to maintain the original control state of the synchronous rectification converter PWM if no driving rising edge signal is received within a preset time interval.

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