Output over-current suppression device and output over-current protection method of DCDC converter

Abstract

The invention provides an output over-current suppression device and an output over-current protection method of a DCDC converter. The reverse input end of a comparator is electrically connected with an output current sampling signal, and the positive input end of the comparator is electrically connected with an output over-current threshold signal; the setting end of the RS trigger is electrically connected with the output end of the comparator, and the reset end of the RS trigger is electrically connected with the switching tube; the digital signal processor U3 receives the output over-current latch signal, executes an output over-current protection strategy, and outputs a reset signal at a proper time according to a protection algorithm logic; the first end of the switch tube is electrically connected with a reset signal output by the signal processor, and the third end of the switch tube is electrically connected with the reset end of the RS trigger. According to the technical scheme, instantaneous output overcurrent signals can be detected and locked, DCDC current loop integration is reduced when overcurrent is output, power switch tube driving of N1 switching periods is blocked, output current rising is restrained, and stable work of the converter is guaranteed when the output current is not serious.

Description

Technical Field

[0001] The invention belongs to the technical field of high-power power conversion, and in particular relates to an output overcurrent suppression device and an output overcurrent protection method of a DCDC converter. Background Art

[0002] A DCDC converter is a device that converts electrical energy of one voltage value into electrical energy of another voltage value in a DC circuit. It is widely used in communications, automotive, industrial automation, medical equipment and other fields, providing stable and reliable power supply for these devices.

[0003] In practical applications, due to the ever-changing field conditions, output overcurrent is a problem that must be faced. Output overcurrent may be caused by a variety of reasons such as load short circuit, load mutation, improper control strategy, etc. Once output overcurrent occurs, it will cause serious damage to the converter and subsequent circuits.

[0004] The traditional output overcurrent hardware protection circuit compares the output current sampling signal with the protection threshold. When the overcurrent occurs, the comparator output level flips, causing the converter to shut down for protection. When the output current is disturbed, the converter will be frequently protected, affecting the converter's continuous and stable operation. The traditional output overcurrent software protection strategy uses a digital solution, so there is a certain delay in sampling and protection. It can only protect against output overcurrents that last for a long time, but not against instantaneous output overcurrents. To solve the above problems, it is necessary to design a more efficient and reliable output overcurrent suppression device and protection strategy to improve the reliability of the DCDC converter.

[0005] Therefore, how to provide an output overcurrent suppression device and an output overcurrent protection method for a DCDC converter, which can detect and lock the instantaneous output overcurrent signal, reduce the DCDC current loop integral when the output is overcurrent, and block the power switch tube drive for N1 switching cycles, thereby suppressing the output current from rising and ensuring the stable operation of the converter when the output current is not serious, has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] The embodiment of the present invention provides an output overcurrent suppression device and an output overcurrent protection method for a DCDC converter, which can detect and lock the instantaneous output overcurrent signal, reduce the DCDC current loop integral when the output is overcurrent, and block the power switch tube drive for N1 switching cycles, thereby suppressing the output current from rising and ensuring the stable operation of the converter when the output current is not serious.

[0007] In one embodiment of the present invention, there is provided an output overcurrent suppression device for a DCDC converter, the suppression device comprising: a comparator U1, an RS trigger U2, a digital signal processor U3 and a switch tube Q1;

[0008] The comparator U1, whose reverse input terminal is electrically connected to the output current sampling signal Iout, and whose positive input terminal is electrically connected to the output overcurrent threshold signal Vocp, which is obtained by voltage division of the first resistor R1 and the second resistor R2;

[0009] The electrical characteristics of the set terminal S and the reset terminal R of the RS trigger U2 are both low level effective, the set terminal S and the reset terminal R are connected to a high level through the fourth pull-up resistor R4 and the twelfth pull-up resistor R12 respectively, the set terminal S is electrically connected to the output terminal of the comparator U1, and the reset terminal R is electrically connected to the switch tube Q1;

[0010] The digital signal processor U3 is a carrier of the output overcurrent protection strategy, receives the output overcurrent latch signal Ocp, executes the output overcurrent protection strategy, and outputs the reset signal Krst at an appropriate time according to the protection algorithm logic;

[0011] The switch tube Q1 has a first end electrically connected to the reset signal Krst output by the signal processor U3, a second end of the switch tube Q1 is grounded AGND, and a third end of the switch tube Q1 is electrically connected to the reset end R of the RS trigger U2.

[0012] Furthermore, the output end of the comparator U1 is electrically connected to the set end S of the RS trigger U2. When the output current sampling signal Iout is greater than the output overcurrent threshold signal Vocp, the output end of the comparator U1 is at a low level, and the RS trigger U2 is set.

[0013] Furthermore, the forward output terminal Q of the RS trigger U2 is divided by the sixth resistor 6 and the seventh resistor R7 connected to the ground GND to obtain an output overcurrent latch signal Ocp, and the output overcurrent latch signal Ocp is electrically connected to the digital signal processor U3; the reverse output terminal Q' of the RS trigger U2 is an off drive signal DrvOff, and the off drive signal DrvOff is electrically connected to the power switch tube drive network, and is a continuous low-level signal during the output overcurrent latch period, so that the power switch tube drive is continuously turned off.

[0014] Furthermore, when the reset signal Krst is at a high level, the switch tube Q1 is turned on, and the reset terminal R of the RS trigger U2 is at a low level, so that the RS trigger U2 is reset.

[0015] Furthermore, the output current sampling network uses a current Hall sensor or a shunt resistor to convert the output current of the DCDC main power circuit into an output current sampling voltage signal Iout.

[0016] In another embodiment of the present invention, a method for protecting an output overcurrent of a DCDC converter is provided. The output overcurrent suppression device of a DCDC converter according to any one of the above items comprises:

[0017] S101, setting a switching cycle counter and an output overcurrent accumulative counter, adding 1 to the switching cycle counter in each switching cycle, and detecting the output overcurrent latch signal Ocp;

[0018] S102, if it is detected that the output overcurrent latch signal Ocp is at a high level, it means that the output overcurrent occurs, and the output overcurrent latch signal Ocp is in a continuously high level locked state, at this time the output overcurrent is in an undetectable state, and the process goes to S103; on the contrary, if the output overcurrent latch signal Ocp is at a low level, the process goes to step S105;

[0019] S103, adding 1 to the output overcurrent accumulator counter, and suppressing the output current from two aspects at the same time. On the one hand, the DCDC current loop integral variable is reduced, and the reduction method can be the original 1 / K1, and on the other hand, the power switch tube drive of N1 switching cycles is blocked; wherein the coefficient K1 is a natural number, ranging from 2 to 10, and the coefficient N1 is a natural number, ranging from 3 to 6; enter S104;

[0020] S104, setting the reset signal Krst to a high level, resetting the RS trigger U2, so that the blocking of the power switch tube drive is released, and at the same time, the output overcurrent latch signal Ocp is released from the locking state, and the output overcurrent is restored to a detectable state;

[0021] S105. If the value of the output overcurrent accumulative counter is greater than N2 and the switching cycle counter is less than N3, an output overcurrent fault is reported and the DCDC converter is shut down for protection; otherwise, the output overcurrent accumulative counter and the switching cycle counter are cleared; wherein the coefficient N2 and the coefficient N3 are natural numbers, and N2>N3.

[0022] Furthermore, the method comprises:

[0023] When the DCDC converter is working normally, the digital signal processor U3 sets the reset signal Krst to a low level, then the switch tube Q1 is turned off, the reset terminal R of the RS trigger U2 is pulled up to a high level, and the output overcurrent is in a detectable state;

[0024] When the output current sampling value is higher than the output overcurrent threshold, the comparator U1 outputs a low level, the RS trigger U2 is set and locked, the forward output terminal Q of the RS trigger U2 is continuously high, and the reverse output terminal Q' is continuously low, and the power switch tube drive is continuously turned off;

[0025] When the positive output terminal Q of the RS trigger U2 is at a continuous high level, in order to suppress output overcurrent, the digital signal processor U3 reduces the DCDC current loop integral variable on the one hand, and controls the number of switching cycles of the power switch tube drive on the other hand.

[0026] Furthermore, the method comprises:

[0027] When the digital signal processor U3 detects that the power switch tube driver is closed for N1 switching cycles, the reset signal Krst is set to a high level, the switch tube Q1 is turned on, the reset terminal R of the RS trigger U2 is pulled down to a low level, the RS trigger U2 is reset, and the power switch tube driver is restored to enable;

[0028] The digital signal processor U3 sets the reset signal Krst to a low level in the next switching cycle, so that the output overcurrent is restored to a detectable state.

[0029] Furthermore, the method comprises:

[0030] A switching cycle counter and an output overcurrent accumulative counter are set in the digital signal processor U3. In each switching cycle, the switching cycle counter is incremented by 1, and the output overcurrent accumulative counter is incremented by 1 when the positive output terminal Q of the RS trigger U2 is at a high level;

[0031] If the value of the output overcurrent accumulative counter is greater than N2 and the switching cycle counter is less than N3, an output overcurrent fault is reported, and the DCDC converter is switched to a fault state and shut down for protection; otherwise, the output overcurrent accumulative counter and the switching cycle counter are cleared.

[0032] The beneficial effects brought by the present invention are as follows:

[0033] It can be seen from the above scheme that the embodiment of the present invention provides an output overcurrent suppression device and an output overcurrent protection method for a DCDC converter, the reverse input terminal of the comparator is electrically connected to the output current sampling signal, and the positive input terminal of the comparator is electrically connected to the output overcurrent threshold signal; the electrical characteristics of the set terminal and the reset terminal of the RS trigger are low level effective, the set terminal is electrically connected to the output terminal of the comparator, and the reset terminal is electrically connected to the switch tube; the digital signal processor U3 receives the output overcurrent latch signal, executes the output overcurrent protection strategy, and outputs the reset signal at an appropriate time according to the protection algorithm logic; the first terminal of the switch tube is electrically connected to the reset signal output by the signal processor, and the third terminal of the switch tube is electrically connected to the reset terminal of the RS trigger. The technical solution of the present invention can detect and lock the instantaneous output overcurrent signal, reduce the DCDC current loop integral when the output is overcurrent, and block the power switch tube drive of N1 switching cycles, suppress the output current rise, and ensure the stable operation of the converter when the output current is not serious. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic circuit diagram of an output overcurrent suppression device of a DCDC converter according to an embodiment of the present invention is shown;

[0035] Figure 2 A flow chart of an output overcurrent protection method for a DCDC converter according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] like Figure 1 As shown, Figure 1 A circuit diagram of an output overcurrent suppression device of a DCDC converter according to an embodiment of the present invention is shown.

[0038] Figure 1 In the invention, an output overcurrent suppression device of a DCDC converter is provided, the suppression device comprising: a comparator U1, an RS trigger U2, a digital signal processor U3 and a switch tube Q1;

[0039] The comparator U1 has a reverse input terminal electrically connected to the output current sampling signal Iout, and a positive input terminal electrically connected to the output overcurrent threshold signal Vocp. The output overcurrent threshold signal Vocp is obtained by dividing the voltage of the first resistor R1 and the second resistor R2. The resistance values ​​of R1 and R2 can be adjusted as required to change the output overcurrent threshold.

[0040] The electrical characteristics of the set terminal S and the reset terminal R of the RS trigger U2 are both low level effective, the set terminal S and the reset terminal R are connected to a high level through the fourth pull-up resistor R4 and the twelfth pull-up resistor R12 respectively, the set terminal S is electrically connected to the output terminal of the comparator U1, and the reset terminal R is electrically connected to the switch tube Q1;

[0041] The digital signal processor U3 is a carrier of the output overcurrent protection strategy, receives the output overcurrent latch signal Ocp, executes the output overcurrent protection strategy, and outputs the reset signal Krst at an appropriate time according to the protection algorithm logic;

[0042] The switch tube Q1 has a first end electrically connected to the reset signal Krst output by the signal processor U3, a second end of the switch tube Q1 is grounded AGND, and a third end of the switch tube Q1 is electrically connected to the reset end R of the RS trigger U2.

[0043] In the embodiment of the present invention, the DCDC converter needs to use a digital control method, which is applicable to various DCDC power topology types, including a half-bridge three-level converter, an LLC converter, a BUCK converter, etc.

[0044] In one embodiment of the present invention, the output end of the comparator U1 is electrically connected to the set end S of the RS trigger U2. When the output current sampling signal Iout is greater than the output overcurrent threshold signal Vocp, the output end of the comparator U1 is at a low level, and the RS trigger U2 is set.

[0045] In one embodiment of the present invention, the forward output terminal Q of the RS trigger U2 is divided by the sixth resistor 6 and the seventh resistor R7 connected to the ground GND to obtain an output overcurrent latch signal Ocp, and the output overcurrent latch signal Ocp is electrically connected to the digital signal processor U3; the reverse output terminal Q' of the RS trigger U2 is an off drive signal DrvOff, and the off drive signal DrvOff is electrically connected to the power switch tube drive network, and is a continuous low-level signal during the output overcurrent latch period, so that the power switch tube drive is continuously turned off.

[0046] In yet another embodiment of the present invention, when the reset signal Krst is at a high level, the switch tube Q1 is turned on, and the reset terminal R of the RS trigger U2 is at a low level, so that the RS trigger U2 is reset.

[0047] In yet another embodiment of the present invention, the output current sampling network uses a current Hall sensor or a shunt resistor to convert the output current of the DCDC main power circuit into an output current sampling voltage signal Iout.

[0048] Figure 1 In a circuit of an output overcurrent suppression device of a DCDC converter, an eighth resistor R8 and a first capacitor C1 are high-frequency filtering structures of an input current sampling signal, a second capacitor C2 is a high-frequency filtering capacitor of a reset terminal R of an RS trigger U2, and a third resistor R3, a fifth resistor R5, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, and a fourteenth resistor R14 are device matching resistors.

[0049] like Figure 2 As shown, Figure 2 A flow chart of an output overcurrent protection method for a DCDC converter according to an embodiment of the present invention is shown.

[0050] Figure 2 In the present invention, a method for protecting an output overcurrent of a DCDC converter is provided, based on an output overcurrent suppression device of a DCDC converter as described in any one of the above items, comprising:

[0051] S101, setting a switching cycle counter and an output overcurrent accumulative counter, adding 1 to the switching cycle counter in each switching cycle, and detecting the output overcurrent latch signal Ocp;

[0052] S102, if it is detected that the output overcurrent latch signal Ocp is at a high level, it means that the output overcurrent occurs, and the output overcurrent latch signal Ocp is in a continuously high level locked state, at this time the output overcurrent is in an undetectable state, and the process goes to S103; on the contrary, if the output overcurrent latch signal Ocp is at a low level, the process goes to step S105;

[0053] S103, adding 1 to the output overcurrent accumulator counter, and suppressing the output current from two aspects at the same time. On the one hand, the DCDC current loop integral variable is reduced, and the reduction method can be the original 1 / K1, and on the other hand, the power switch tube drive of N1 switching cycles is blocked; wherein the coefficient K1 is a natural number, ranging from 2 to 10, and the coefficient N1 is a natural number, ranging from 3 to 6; enter S104;

[0054] S104, setting the reset signal Krst to a high level, resetting the RS trigger U2, so that the blocking of the power switch tube drive is released, and at the same time, the output overcurrent latch signal Ocp is released from the locking state, and the output overcurrent is restored to a detectable state;

[0055] S105. If the value of the output overcurrent accumulative counter is greater than N2 and the switching cycle counter is less than N3, an output overcurrent fault is reported and the DCDC converter is shut down for protection; otherwise, the output overcurrent accumulative counter and the switching cycle counter are cleared; wherein the coefficient N2 and the coefficient N3 are natural numbers, and N2>N3.

[0056] In one embodiment of the present invention, the method comprises:

[0057] When the DCDC converter is working normally, the digital signal processor U3 sets the reset signal Krst to a low level, then the switch tube Q1 is turned off, the reset terminal R of the RS trigger U2 is pulled up to a high level, and the output overcurrent is in a detectable state;

[0058] When the output current sampling value is higher than the output overcurrent threshold, the comparator U1 outputs a low level, the RS trigger U2 is set and locked, the forward output terminal Q of the RS trigger U2 is continuously high, and the reverse output terminal Q' is continuously low, and the power switch tube drive is continuously turned off;

[0059] When the positive output terminal Q of the RS trigger U2 is at a continuous high level, in order to suppress output overcurrent, the digital signal processor U3 reduces the DCDC current loop integral variable on the one hand, and controls the number of switching cycles of the power switch tube drive on the other hand.

[0060] In another embodiment of the present invention, the method comprises:

[0061] When the digital signal processor U3 detects that the power switch tube driver is closed for N1 switching cycles, the reset signal Krst is set to a high level, the switch tube Q1 is turned on, the reset terminal R of the RS trigger U2 is pulled down to a low level, the RS trigger U2 is reset, and the power switch tube driver is restored to enable;

[0062] The digital signal processor U3 sets the reset signal Krst to a low level in the next switching cycle, so that the output overcurrent is restored to a detectable state.

[0063] In another embodiment of the present invention, the method comprises:

[0064] A switching cycle counter and an output overcurrent accumulative counter are set in the digital signal processor U3. In each switching cycle, the switching cycle counter is incremented by 1, and the output overcurrent accumulative counter is incremented by 1 when the positive output terminal Q of the RS trigger U2 is at a high level;

[0065] If the value of the output overcurrent accumulative counter is greater than N2 and the switching cycle counter is less than N3, an output overcurrent fault is reported, and the DCDC converter is switched to a fault state and shut down for protection; otherwise, the output overcurrent accumulative counter and the switching cycle counter are cleared.

[0066] In an embodiment of the present invention, an output overcurrent suppression device and an output overcurrent protection method of a DCDC converter are provided, wherein the reverse input terminal of the comparator is electrically connected to the output current sampling signal, and the positive input terminal of the comparator is electrically connected to the output overcurrent threshold signal; the electrical characteristics of the set terminal and the reset terminal of the RS trigger are low level effective, the set terminal is electrically connected to the output terminal of the comparator, and the reset terminal is electrically connected to the switch tube; the digital signal processor U3 receives the output overcurrent latch signal, executes the output overcurrent protection strategy, and outputs the reset signal at an appropriate time according to the protection algorithm logic; the first terminal of the switch tube is electrically connected to the reset signal output by the signal processor, and the third terminal of the switch tube is electrically connected to the reset terminal of the RS trigger. The technical solution of the present invention can detect and lock the instantaneous output overcurrent signal, reduce the DCDC current loop integral when the output is overcurrent, and block the power switch tube drive of N1 switching cycles, suppress the output current rise, and ensure the stable operation of the converter when the output current is not serious.

[0067] The DCDC converter output overcurrent suppression device and output overcurrent protection strategy described in the present invention take into account the instantaneousness of hardware circuit detection and the flexibility of software protection strategy, and can detect and lock the instantaneous output overcurrent signal. When the output is overcurrent, the DCDC current loop integral is reduced on the one hand, and the power switch tube drive of N1 switching cycles is blocked on the other hand to suppress the output current from rising, and ensure the stable operation of the converter when the output current is not serious. The technical solution of the present invention uses software to count the number of output overcurrents within a preset switching cycle, and when the output overcurrent exceeds the preset threshold, an output overcurrent fault is reported, causing the converter to shut down for protection, effectively avoiding damage to the converter circuit components or accidents.

[0068] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An output overcurrent suppression device for a DCDC converter, characterized in that: The suppression device comprises: a comparator U1, an RS trigger U2, a digital signal processor U3 and a switch tube Q1; The comparator U1, whose reverse input terminal is electrically connected to the output current sampling signal Iout, and whose positive input terminal is electrically connected to the output overcurrent threshold signal Vocp, which is obtained by voltage division of the first resistor R1 and the second resistor R2; The electrical characteristics of the set terminal S and the reset terminal R of the RS trigger U2 are both low level effective, the set terminal S and the reset terminal R are connected to a high level through the fourth pull-up resistor R4 and the twelfth pull-up resistor R12 respectively, the set terminal S is electrically connected to the output terminal of the comparator U1, and the reset terminal R is electrically connected to the switch tube Q1; The digital signal processor U3 is a carrier of the output overcurrent protection strategy, receives the output overcurrent latch signal Ocp, executes the output overcurrent protection strategy, and outputs the reset signal Krst at an appropriate time according to the protection algorithm logic; The switch tube Q1 has a first end electrically connected to the reset signal Krst output by the signal processor U3, a second end of the switch tube Q1 is grounded AGND, and a third end of the switch tube Q1 is electrically connected to the reset end R of the RS trigger U2.

2. The output overcurrent suppression device of a DCDC converter according to claim 1, characterized in that: The output end of the comparator U1 is electrically connected to the set end S of the RS trigger U2. When the output current sampling signal Iout is greater than the output overcurrent threshold signal Vocp, the output end of the comparator U1 is at a low level, and the RS trigger U2 is set.

3. The output overcurrent suppression device of a DCDC converter according to claim 1, characterized in that: The positive output terminal Q of the RS trigger U2 is divided by the sixth resistor 6 and the seventh resistor R7 connected to the ground GND to obtain the output overcurrent latch signal Ocp, and the output overcurrent latch signal Ocp is electrically connected to the digital signal processor U3; the reverse output terminal Q' of the RS trigger U2 is the off drive signal DrvOff, and the off drive signal DrvOff is electrically connected to the power switch tube drive network, and is a continuous low-level signal during the output overcurrent latch period, so that the power switch tube drive is continuously turned off.

4. The output overcurrent suppression device of a DCDC converter according to claim 1, characterized in that: When the reset signal Krst is at a high level, the switch tube Q1 is turned on, and the reset terminal R of the RS trigger U2 is at a low level, so that the RS trigger U2 is reset.

5. The output overcurrent suppression device of a DCDC converter according to claim 1, characterized in that: The output current sampling network uses a current Hall sensor or a shunt resistor to convert the output current of the DCDC main power circuit into an output current sampling voltage signal Iout.

6. A method for protecting an output overcurrent of a DCDC converter, based on an output overcurrent suppression device of a DCDC converter as claimed in any one of claims 1 to 5, characterized in that: The protection method comprises: S101, setting a switching cycle counter and an output overcurrent accumulative counter, adding 1 to the switching cycle counter in each switching cycle, and detecting the output overcurrent latch signal Ocp; S102, if it is detected that the output overcurrent latch signal Ocp is at a high level, it means that the output overcurrent occurs, and the output overcurrent latch signal Ocp is in a continuously high level locked state, at this time the output overcurrent is in an undetectable state, and the process goes to S103; on the contrary, if the output overcurrent latch signal Ocp is at a low level, the process goes to step S105; S103, adding 1 to the output overcurrent accumulator counter, and suppressing the output current from two aspects at the same time. On the one hand, the DCDC current loop integral variable is reduced, and the reduction method can be the original 1 / K1, and on the other hand, the power switch tube drive of N1 switching cycles is blocked; wherein the coefficient K1 is a natural number, ranging from 2 to 10, and the coefficient N1 is a natural number, ranging from 3 to 6; enter S104; S104, setting the reset signal Krst to a high level, resetting the RS trigger U2, so that the blocking of the power switch tube drive is released, and at the same time, the output overcurrent latch signal Ocp is released from the locking state, and the output overcurrent is restored to a detectable state; S105. If the value of the output overcurrent accumulative counter is greater than N2 and the switching cycle counter is less than N3, an output overcurrent fault is reported and the DCDC converter is shut down for protection; otherwise, the output overcurrent accumulative counter and the switching cycle counter are cleared; wherein the coefficient N2 and the coefficient N3 are natural numbers, and N2>N3.

7. The output overcurrent protection method of a DCDC converter according to claim 6, characterized in that: The method comprises: When the DCDC converter is working normally, the digital signal processor U3 sets the reset signal Krst to a low level, then the switch tube Q1 is turned off, the reset terminal R of the RS trigger U2 is pulled up to a high level, and the output overcurrent is in a detectable state; When the output current sampling value is higher than the output overcurrent threshold, the comparator U1 outputs a low level, the RS trigger U2 is set and locked, the forward output terminal Q of the RS trigger U2 is continuously high, and the reverse output terminal Q' is continuously low, and the power switch tube drive is continuously turned off; When the positive output terminal Q of the RS trigger U2 is at a continuous high level, in order to suppress output overcurrent, the digital signal processor U3 reduces the DCDC current loop integral variable on the one hand, and controls the number of switching cycles of the power switch tube drive on the other hand.

8. The output overcurrent protection method of a DCDC converter according to claim 6, characterized in that: The method comprises: When the digital signal processor U3 detects that the power switch tube driver is closed for N1 switching cycles, the reset signal Krst is set to a high level, the switch tube Q1 is turned on, the reset terminal R of the RS trigger U2 is pulled down to a low level, the RS trigger U2 is reset, and the power switch tube driver is restored to enable; The digital signal processor U3 sets the reset signal Krst to a low level in the next switching cycle, so that the output overcurrent is restored to a detectable state.

9. The output overcurrent protection method of a DCDC converter according to claim 8, characterized in that: The method comprises: A switching cycle counter and an output overcurrent accumulative counter are set in the digital signal processor U3. In each switching cycle, the switching cycle counter is incremented by 1, and the output overcurrent accumulative counter is incremented by 1 when the positive output terminal Q of the RS trigger U2 is at a high level; If the value of the output overcurrent accumulative counter is greater than N2 and the switching cycle counter is less than N3, an output overcurrent fault is reported, and the DCDC converter is switched to a fault state and shut down for protection; otherwise, the output overcurrent accumulative counter and the switching cycle counter are cleared.

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