CN219535886U - Anti-impact current circuit - Google Patents

Abstract

The utility model discloses an anti-impact current circuit which is applied to a switching power supply and mainly comprises a high-voltage power taking circuit, a driving circuit, a current limiting circuit, a sampling turn-off circuit, a turn-off delay circuit, an input port and an output port, wherein the high-voltage power taking circuit is used for reducing voltage at the input end and taking power, the driving circuit is used for generating a driving control signal, the current limiting circuit is used for limiting input current, the sampling turn-off circuit is used for detecting that the input current reaches a set value to turn off driving, and the turn-off delay circuit is used for prolonging turn-off time; the utility model adopts a self-excitation control mode, limits the input current to a set value in the starting process, limits the input current when the input current reaches the set value, and prolongs the starting period to realize soft start, thereby achieving the purpose of inhibiting the impact current.

Description

Anti-impact current circuit

Technical Field

The utility model belongs to the field of switching power supplies, and particularly relates to an anti-impact current circuit.

Background

The input voltage of the switching power supply is usually rectified and filtered by a capacitor connected in parallel after the input end is rectified, and the voltage at two ends of the capacitor is almost zero at the moment of starting the switching power supply, so that a large current pulse, namely a surge current, is required to be provided at the input end when the switching power supply is started. In order to prevent the system from being adversely affected by the rush current, it is necessary for the designer to consider adding the rush current suppressing circuit.

In a conventional switching power supply circuit, the magnitude of the impact current is equal to the magnitude of the input voltage divided by the impedance of the input loop, and the common practice is to connect a negative temperature coefficient thermistor in series with the input loop, as shown in fig. 1, the impact current is effectively inhibited by the thermistor when the switching power supply is started, and the resistance value of the impact current is reduced along with the temperature rise of the thermistor after the switching power supply is started, so that the loss of the switching power supply when the switching power supply normally works is reduced.

The scheme of connecting the negative temperature coefficient thermistor in series in the input loop has some defects, for example, the switching power supply is powered on immediately after being powered off, the temperature of the thermistor is not reduced yet, the resistance is very small, and the purpose of inhibiting the impact current cannot be achieved. Meanwhile, the scheme of connecting the negative temperature coefficient thermistor in series is not suitable for designs with high requirements on impact current. In order to consider the temperature rise of the thermistor and the influence on the system loss, the resistance of the thermistor cannot be too large, the suppression effect on the impact current can only be about 50A, and the larger the power of the switching power supply is, the larger the input current is, the higher the input voltage is, and the lower the effect of the thermistor can be achieved.

The high-power switching power supply sometimes uses a switching device connected in parallel with two ends of the thermistor, as shown in fig. 2, when the power is turned on, the impact current flows through the thermistor, after the power is turned on, the switching device K1 is turned on to reduce the system loss, when the resistance requirement of the thermistor is higher along with the increase of the input voltage, the loss of the thermistor is extremely high at the moment of power on, the stability of the system is seriously affected, and meanwhile, the impact current repeatedly turned on and off cannot be restrained.

Disclosure of Invention

In view of the above, the present utility model provides an anti-impact current circuit, which can realize the suppression of impact current during high voltage input and can satisfy the suppression effect of impact current during repeated startup and shutdown:

in order to achieve the above purpose, the present utility model adopts the following technical scheme:

in a first aspect, an anti-impact current circuit is provided, and is applied to a switching power supply, and the anti-impact current circuit comprises a high-voltage power taking circuit, a driving circuit, a current limiting circuit, a sampling turn-off circuit, a turn-off delay circuit, an input port and an output port; the first input end of the high-voltage power taking circuit is connected with the input vin+ of the input port, the second input end of the high-voltage power taking circuit is connected with the input Vin-, of the input port, the first output end of the turn-off delay circuit and the first output end of the sampling turn-off circuit, and the first output end of the high-voltage power taking circuit is connected with the first input end of the driving circuit and the first input end of the sampling turn-off circuit; the first output end of the driving circuit is connected with the second input end of the sampling turn-off circuit and the second input end of the turn-off delay circuit, and the second output end of the driving circuit is connected with the second input end of the current limiting circuit; the first input end of the current limiting circuit is connected with the output Vo-of the output port, the second output port is connected with the output vo+ of the output port, and the first output end is connected with the first input end of the sampling turn-off circuit and the third output end of the driving circuit;

the high-voltage power-taking circuit is used for reducing voltage input by the input port and taking power, and generating a direct-current voltage signal to the driving circuit and the turn-off delay circuit;

the driving circuit is used for generating a driving control signal according to the direct-current voltage signal and outputting the driving control signal to the current limiting circuit;

the current limiting circuit is used for conducting according to the driving control signal and limiting the input current;

the sampling turn-off circuit is used for comparing the input current with a preset value, and controlling the drive circuit to turn off when the input current is judged to be larger than the preset value;

the turn-off delay circuit is used for controlling the drive circuit to accelerate turn-off when the sampling turn-off circuit judges that the input current is larger than a preset value, and controlling the drive circuit to start to generate a drive control signal after the preset delay time is finished so as to enter the next period.

The current limiting circuit is added between the input port and the output port to limit the impact current, so that the input current is slowed down; detecting the impact current through a sampling turn-off circuit, and limiting the impact current to a reasonable range; the turn-off delay circuit is used for accelerating the turn-off of the drive control signal and delaying the establishment of the drive control signal, so that the switching loss of the current limiting circuit is effectively reduced, and the switching frequency of the current limiting circuit is controlled; the driving circuit provides a driving control signal for the current limiting circuit, and the driving control signal is controlled by the sampling turn-off circuit and the turn-off delay circuit, so that the aim of self-excitation control of the impact current is fulfilled.

Preferably, the high-voltage power taking circuit comprises a resistor R1, a resistor R10, a resistor R11, a switching tube TR2, a zener diode Z2 and a capacitor C3; one end of the resistor R1 is connected with one end of the resistor R10 and then is used as a first input end of the high-voltage power taking circuit; the other end of the resistor R10 is connected with the first end of the switching tube TR2, and the control end of the switching tube TR2 is connected with the other end of the resistor R1 and the cathode of the zener diode Z2; the second end of the switching tube TR2 is connected with one end of the capacitor C3 and then used as a first output end of the high-voltage power taking circuit; the capacitor C3 is connected with the anode of the voltage stabilizing diode Z2 and then serves as a second input end of the high-voltage power taking circuit.

Preferably, the driving circuit comprises a resistor R8, a resistor R9, a triode Q5 and a triode Q6; one end of the resistor R8 is connected with the collector electrode of the triode Q5 and then used as a first input end of the driving circuit; the other end of the resistor R8 is connected with the base electrode of the triode Q5 and the base electrode of the triode Q6 and then used as a first output end of the driving circuit; the emitter of the triode Q5 is connected with the collector of the triode Q6 and one end of the resistor R9 and then used as a second output end of the driving circuit; the emitter of the transistor Q6 is connected to the other end of the resistor R9, and then serves as a third output terminal of the driving circuit.

Preferably, the current limiting circuit comprises an inductor L1, a diode D7 and a switching tube TR1; the control end of the switching tube TR1 is used as a second input end of the current limiting circuit, the second end of the switching tube TR1 is used as a first output end of the current limiting circuit, the first end of the switching tube TR1 is connected with one end of the inductor L1 and the anode of the diode D7, the other end of the inductor L1 is used as the first input end of the current limiting circuit, and the cathode of the diode D7 is used as the second output end of the current limiting circuit.

Preferably, the sampling turn-off circuit comprises a resistor R6, a resistor R7, a capacitor C2 and a triode Q4; the collector of triode Q4 is as the first input of sampling shutoff circuit, and the emitter of triode Q4 is connected with one end of electric capacity C2, resistance R6's one end back, and as the first output of sampling shutoff circuit, and electric capacity C2's the other end is connected with resistance R7's one end, triode Q4's base, and resistance R7's the other end is connected with resistance R6's the other end back, and as the first input of sampling shutoff circuit.

Preferably, the turn-off delay circuit comprises a resistor R2, a resistor R3, a resistor R4, a resistor R5, a triode Q1, a triode Q2, a triode Q3 and a capacitor C1; the collector of the triode Q1 is used as a first input end of the turn-off delay circuit, the base is connected with one end of a resistor R2, and the emitter is connected with one end of a capacitor C1 and the emitter of the triode Q2; the other end of the resistor R2 is connected with one end of the resistor R3 and one end of the resistor R5 and then is used as a second input end of the turn-off delay circuit; the other end of the resistor R3 is connected with the base electrode of the triode Q2, the collector electrode of the triode Q2 is connected with one end of the resistor R4, the other end of the resistor R4 is connected with the base electrode of the triode Q3, the collector electrode of the triode Q3 is connected with the other end of the resistor R5, and the emitter electrode of the triode Q3 is connected with the other end of the capacitor C1 and then serves as a first output end of the turn-off delay circuit.

In a second aspect, an anti-impact current circuit is provided, and is applied to a switching power supply, and the anti-impact current circuit comprises a high-voltage power taking circuit, a driving circuit, a current limiting circuit, a sampling turn-off circuit, a turn-off delay circuit, an input port and an output port;

the high-voltage power taking circuit comprises a resistor R1, a resistor R10, a resistor R11, a switching tube TR2, a voltage stabilizing diode Z2 and a capacitor C3;

the driving circuit comprises a resistor R8, a resistor R9, a triode Q5 and a triode Q6; the current limiting circuit comprises an inductor L1, a diode D7 and a switching tube TR1;

the sampling turn-off circuit comprises a resistor R6, a resistor R7, a capacitor C2 and a triode Q4;

the turn-off delay circuit comprises a resistor R2, a resistor R3, a resistor R4, a resistor R5, a triode Q1, a triode Q2, a triode Q3 and a capacitor C1;

one end of the resistor R1 is connected with one end of the resistor R10, the cathode of the diode D7, the input vin+ of the input port and the output vo+ of the output port; the other end of the resistor R10 is connected with the first end of the switching tube TR2, and the control end of the switching tube TR2 is connected with the other end of the resistor R1 and the cathode of the zener diode Z2; the second end of the switching tube TR2 is connected with one end of the capacitor C3, the collector of the triode Q1, one end of the resistor R8 and the collector of the triode Q5; the capacitor C3 is connected with the anode of the voltage stabilizing diode Z2, the input Vin of the input port, one end of the capacitor C1, the emitter of the triode Q3, the emitter of the triode Q4, one end of the capacitor C2 and one end of the resistor R6; the other end of the resistor R8 is connected with the base electrode of the triode Q5, the base electrode of the triode Q6, one end of the resistor R2, one end of the resistor R3, one end of the resistor R5 and the collector electrode of the triode Q4; the emitter of the triode Q5 is connected with the collector of the triode Q6, one end of a resistor R9 and the control end of a switching tube TR1; the emitter of the triode Q6 is connected with the other end of the resistor R9, the other end of the resistor R6, one end of the resistor R7 and the second end of the switching tube TR1; the first end of the switching tube TR1 is connected with one end of the inductor L1 and the anode of the diode D7, and the other end of the inductor L1 is connected with the output Vo of the output port; the other end of the capacitor C2 is connected with the other end of the resistor R7 and the base electrode of the triode Q4; the base electrode of the triode Q1 is connected with the other end of the resistor R2, and the emitter electrode of the triode Q1 is connected with the other end of the capacitor C1 and the emitter electrode of the triode Q2; the other end of the resistor R3 is connected with the base electrode of the triode Q2, the collector electrode of the triode Q2 is connected with one end of the resistor R4, the other end of the resistor R4 is connected with the base electrode of the triode Q3, and the collector electrode of the triode Q3 is connected with the other end of the resistor R5.

Compared with the prior art, the utility model has the beneficial effects that:

1. the utility model does not need a thermistor, can effectively reduce the internal loss of the switching power supply, and meets the protection requirement of continuous on-off on impact current.

2. According to the utility model, the size of the impact current can be limited by adjusting the sampling threshold value of the sampling circuit, the size specification of the impact current can be designed to be below 10A, soft start is realized by prolonging the start-up process, the influence of the start-up process on power grid fluctuation is reduced, the impact current cannot change along with the change of input voltage, and the protection requirement of the impact current of high-voltage input is met.

3. The utility model adopts a self-excitation control mode, is provided with a control circuit, does not need additional control signals, has simple circuit system, and can effectively control the cost and the volume by sharing an inductance device in the current-limiting circuit with a differential mode filter device in a switching power supply.

Drawings

Fig. 1 is a schematic diagram of a conventional thermistor anti-surge current circuit.

Fig. 2 is a schematic diagram of a switching device parallel thermistor anti-surge current circuit.

Fig. 3 is a schematic block diagram of the current surge protection circuit of the present utility model.

Fig. 4 is a schematic diagram of a specific circuit of the anti-rush current circuit of the present utility model.

Detailed Description

In order that the utility model may be more readily understood, a more particular description thereof will be rendered by reference to specific embodiments that are illustrated in the appended drawings. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the utility model.

As shown in fig. 3, a schematic block diagram of an anti-impact current circuit of the present utility model includes a high-voltage power taking circuit 01, a driving circuit 02, a current limiting circuit 03, a sampling off circuit 04, a turn-off delay circuit 05, an input port 06 and an output port 07, wherein the anti-impact current circuit adopts a self-excitation control scheme. The high-voltage power taking circuit 01 comprises a first input end, a second input end and a first output end; the driving circuit 02 includes a first input terminal, a first output terminal, a second output terminal, and a third output terminal (not shown in the figure); the current limiting circuit 03 comprises a first input end, a second input end, a first output end and a second output end; the sampling turn-off circuit 04 comprises a first input end, a second input end and a first output end; the turn-off delay circuit 05 includes a first input terminal, a second input terminal, and a first output terminal; input port 06 contains input vin+, input Vin-; the output port 07 contains an input vo+, an input Vo-; the first input end of the high-voltage power taking circuit 01 is connected with the input vin+ of the input port 06, the second input end of the high-voltage power taking circuit 01 is connected with the first output end of the input Vin-, turn-off delay circuit 05 and the first output end of the sampling turn-off circuit 04 of the input port 06, and the first output end of the high-voltage power taking circuit 01 is connected with the first input end of the driving circuit 02 and the first input end of the sampling turn-off circuit 04; a first output end of the driving circuit 02 is connected with a second input end of the sampling turn-off circuit 04 and a second input end of the turn-off delay circuit 05, and a second output end of the driving circuit 02 is connected with a second input end of the current limiting circuit 03; the first input end of the current limiting circuit 03 is connected with the output Vo-of the output port 07, the second output port 07 is connected with the output vo+ of the output port 07, and the first output end is connected with the first input end of the sampling cut-off circuit 04 and the third output end of the driving circuit 02;

the high-voltage power taking circuit 01 is used for reducing voltage and taking power of the voltage input by the input port 06, and generating a direct-current voltage signal to the driving circuit 02 and the turn-off delay circuit 05;

the driving circuit 02 is used for generating a driving control signal according to the direct-current voltage signal and outputting the driving control signal to the current limiting circuit 03;

the current limiting circuit 03 is used for conducting according to the driving control signal and limiting the input current;

the sampling turn-off circuit 04 is used for comparing the input current with a preset value, and when the input current is judged to be larger than the preset value, the driving circuit 02 is controlled to be turned off;

the turn-off delay circuit is used for controlling the driving circuit 02 to accelerate turn-off when the sampling turn-off circuit 04 judges that the input current is larger than a preset value, and controlling the driving circuit 02 to start generating a driving control signal after the preset delay time is over so as to enter the next period.

Specifically, the driving circuit 02 generates a driving control signal by providing a direct current voltage by the high-voltage power taking circuit 01, and controls the establishment and the disconnection of the driving control signal through a first output port of the driving circuit 02, when the power-on is started, an impact current flows into a first input port of the current limiting circuit 03 through an output port 07 to output vo+ and output Vo-, and when the driving control signal is disconnected, the impact current flows into the output port 07 through a second output port to output vo+ and freewheel; the impulse current flows into the first input port of the sampling cut-off circuit 04 through the first output end of the current limiting circuit 03, then flows out to the input port 06 input Vin-from the first output end of the sampling cut-off circuit 03, when the impulse current reaches a set value, the sampling cut-off circuit 04 pulls down the voltage of the second input port, and the second output end of the driving circuit 02 is controlled to pull down the driving control signal; when the driving control signal is pulled down by the second input port of the sampling turn-off circuit 04, the second input port of the turn-off delay circuit 05 drops the acceleration driving control signal, and the driving control signal is used for controlling the driving control signal, and the driving control signal and the acceleration driving control signal are in synchronous relation. The second input port of the turn-off delay circuit 05 is pulled down for a while, and then the pulled down state is released, and the drive control signal is re-established by the drive circuit 02 to start the next cycle.

In the embodiment, the current limiting circuit 03 is added between the input port 06 and the output port 07 to limit the impact current, so that the input current is slowed down; detecting the impact current through a sampling turn-off circuit 04, and limiting the impact current to a reasonable range; the turn-off delay circuit 05 is used for accelerating the turn-off of the drive control signal and delaying the establishment of the drive control signal, so that the switching loss of the current limiting circuit is effectively reduced, and the switching frequency of the current limiting circuit is controlled; the driving circuit 02 supplies a driving control signal to the limiting circuit 03, and then the driving control signal is controlled by the sampling turn-off circuit 04 and the turn-off delay circuit 05, so that the aim of self-excitation control of the impulse current is fulfilled.

As shown in fig. 4, fig. 4 is a specific circuit diagram of an anti-impact current circuit according to the present embodiment; the high-voltage power taking circuit 01 comprises a resistor R1, a resistor R10, a resistor R11, a switching tube TR2, a voltage stabilizing diode Z2 and a capacitor C3; the driving circuit 02 comprises a resistor R8, a resistor R9, a triode Q5 and a triode Q6; the current limiting circuit 03 comprises an inductor L1, a diode D7 and a switching tube TR1; the sampling turn-off 04 circuit comprises a sampling resistor R6, a resistor R7, a capacitor C2 and a triode Q4; the turn-off delay circuit 05 comprises a resistor R2, a resistor R3, a resistor R4, a resistor R5, a triode Q1, a triode Q2, a triode Q3 and a capacitor C1; the input port 05 includes an input vin+, an input Vin-; the output port 06 contains an input vo+, an input Vo-.

The connection relation of the components of the anti-impact current circuit in this embodiment is as follows:

one end of the resistor R1 is connected with one end of the resistor R10, the cathode of the diode D7, the input vin+ of the input port and the output vo+ of the output port; the other end of the resistor R10 is connected with the first end of the switching tube TR2, and the control end of the switching tube TR2 is connected with the other end of the resistor R1 and the cathode of the zener diode Z2; the second end of the switching tube TR2 is connected with one end of the capacitor C3, the collector of the triode Q1, one end of the resistor R8 and the collector of the triode Q5; the capacitor C3 is connected with the anode of the voltage stabilizing diode Z2, the input Vin of the input port, one end of the capacitor C1, the emitter of the triode Q3, the emitter of the triode Q4, one end of the capacitor C2 and one end of the resistor R6; the other end of the resistor R8 is connected with the base electrode of the triode Q5, the base electrode of the triode Q6, one end of the resistor R2, one end of the resistor R3, one end of the resistor R5 and the collector electrode of the triode Q4; the emitter of the triode Q5 is connected with the collector of the triode Q6, one end of a resistor R9 and the control end of a switching tube TR1; the emitter of the triode Q6 is connected with the other end of the resistor R9, the other end of the resistor R6, one end of the resistor R7 and the second end of the switching tube TR1; the first end of the switching tube TR1 is connected with one end of the inductor L1 and the anode of the diode D7, and the other end of the inductor L1 is connected with the output Vo of the output port; the other end of the capacitor C2 is connected with the other end of the resistor R7 and the base electrode of the triode Q4; the base electrode of the triode Q1 is connected with the other end of the resistor R2, and the emitter electrode of the triode Q1 is connected with the other end of the capacitor C1 and the emitter electrode of the triode Q2; the other end of the resistor R3 is connected with the base electrode of the triode Q2, the collector electrode of the triode Q2 is connected with one end of the resistor R4, the other end of the resistor R4 is connected with the base electrode of the triode Q3, and the collector electrode of the triode Q3 is connected with the other end of the resistor R5.

As shown in fig. 4, the specific working mode of the anti-impact current circuit in this embodiment is that, when the switch tube TR1 is in an off state during startup, the voltages at two ends of the output port 07 are zero, the resistors R1, R10 and R11 are current limiting resistors, the high-voltage power taking circuit 01 steps down and takes power through the input port 06, a direct-current voltage is established on the capacitor C3, and when the voltage of C3 is greater than or equal to the voltage stabilizing value of the zener diode Z2, the switch tube TR2 is turned off, so as to ensure the stability of the voltage of C3; the resistor R8 is a current limiting resistor, the resistor R9 is a pull-down resistor, the voltage of the capacitor C3 is connected with a totem pole formed by the triodes Q5 and Q6 through the resistor R8, a driving control signal is generated, the driving control signal is amplified by the triode Q5 to become a driving control signal, meanwhile, the triode Q1 of the delay circuit 05 is turned on, and the capacitor C1 is charged through the triode Q1; the driving control signal gradually rises, the switching tube TR1 is conducted, input impact current flows into the inductor L1, the inductor L1 limits to enable the input impact current to linearly increase, at the moment, the inductor L1 is excited positively, and meanwhile, the voltage at two ends of the output port 07 starts to rise; the resistor R7 and the resistor C2 form RC filtering, the resistor R6 is a sampling resistor, input impact current is converted into a voltage signal through the sampling resistor R6, as the current linearly increases, the voltage drop of the sampling resistor R6 reaches the base bias voltage of the triode Q4, the triode Q4 is conducted to pull down a driving control signal, the driving control signal is pulled down along with the driving control signal, and the switching tube TR1 of the current limiting circuit 03 is turned off; the resistors R2, R3, R4 and R5 are current limiting resistors, when the driving control signal is pulled down, the triode Q1 of the turn-off delay circuit 04 is cut off, the capacitor C1 discharges through the triode Q2, the current limiting resistor R3 and the current limiting resistor R4, and at the moment, the triode Q3 is conducted to accelerate the driving control signal to be pulled down. Because of the current limiting effect of the resistor R3 and the resistor R4, the discharging time of the capacitor C1 is the delay time of the drive turn-off, and the current limiting circuit 02 inductance L1 freewheels through the freewheeled diode D7 in the delay time, and the voltage at two ends of the output port 07 continuously rises; after the capacitor C1 of the turn-off delay circuit 05 is discharged, the transistor Q3 and the transistor Q4 are turned off, the driving control signal of the driving circuit 02 is reestablished, the switching tube TR1 of the current limiting circuit 03 starts to be turned on, and the next period starts. After repeating the above steps for a plurality of periods, the voltage across the output port 07 is established, and then the switching tube TR1 of the current limiting circuit 03 is normally on, and the inductor L1 acts as a differential mode filter.

The foregoing is merely a preferred embodiment of the present utility model, and it should be noted that the foregoing preferred embodiment should not be considered as limiting the utility model, and it will be apparent to those skilled in the art that modifications and adaptations can be made without departing from the spirit and scope of the utility model, such that the examples and features of the examples can be combined with each other without conflict, and the scope of the utility model is to be considered as protection of the utility model, which is not repeated herein, and is intended to be limited by the scope of the claims.

Claims (7)

1. The anti-impact current circuit is applied to a switching power supply and is characterized by comprising a high-voltage power taking circuit, a driving circuit, a current limiting circuit, a sampling turn-off circuit, a turn-off delay circuit, an input port and an output port; the first input end of the high-voltage power taking circuit is connected with the input vin+ of the input port, the second input end of the high-voltage power taking circuit is connected with the input Vin-, of the input port, the first output end of the turn-off delay circuit and the first output end of the sampling turn-off circuit, and the first output end of the high-voltage power taking circuit is connected with the first input end of the driving circuit and the first input end of the sampling turn-off circuit; the first output end of the driving circuit is connected with the second input end of the sampling turn-off circuit and the second input end of the turn-off delay circuit, and the second output end of the driving circuit is connected with the second input end of the current limiting circuit; the first input end of the current limiting circuit is connected with the output Vo-of the output port, the second output port is connected with the output vo+ of the output port, and the first output end is connected with the first input end of the sampling turn-off circuit and the third output end of the driving circuit;

the high-voltage power-taking circuit is used for reducing voltage input by the input port and taking power, and generating a direct-current voltage signal to the driving circuit and the turn-off delay circuit;

the driving circuit is used for generating a driving control signal according to the direct-current voltage signal and outputting the driving control signal to the current limiting circuit;

the current limiting circuit is used for conducting according to the driving control signal and limiting the input current;

the sampling turn-off circuit is used for comparing the input current with a preset value, and controlling the drive circuit to turn off when the input current is judged to be larger than the preset value;

the turn-off delay circuit is used for controlling the drive circuit to accelerate turn-off when the sampling turn-off circuit judges that the input current is larger than a preset value, and controlling the drive circuit to start to generate a drive control signal after the preset delay time is finished so as to enter the next period.

2. The anti-impact current circuit according to claim 1, wherein the high-voltage sampling circuit comprises a resistor R1, a resistor R10, a resistor R11, a switching tube TR2, a zener diode Z2 and a capacitor C3; one end of the resistor R1 is connected with one end of the resistor R10 and then is used as a first input end of the high-voltage power taking circuit; the other end of the resistor R10 is connected with the first end of the switching tube TR2, and the control end of the switching tube TR2 is connected with the other end of the resistor R1 and the cathode of the zener diode Z2; the second end of the switching tube TR2 is connected with one end of the capacitor C3 and then used as a first output end of the high-voltage power taking circuit; the capacitor C3 is connected with the anode of the voltage stabilizing diode Z2 and then serves as a second input end of the high-voltage power taking circuit.

3. The anti-surge current circuit of claim 1, wherein the driving circuit comprises a resistor R8, a resistor R9, a transistor Q5, a transistor Q6; one end of the resistor R8 is connected with the collector electrode of the triode Q5 and then used as a first input end of the driving circuit; the other end of the resistor R8 is connected with the base electrode of the triode Q5 and the base electrode of the triode Q6 and then used as a first output end of the driving circuit; the emitter of the triode Q5 is connected with the collector of the triode Q6 and one end of the resistor R9 and then used as a second output end of the driving circuit; the emitter of the transistor Q6 is connected to the other end of the resistor R9, and then serves as a third output terminal of the driving circuit.

4. The anti-rush current circuit according to claim 1, wherein the current limiting circuit includes an inductance L1, a diode D7, and a switching tube TR1; the control end of the switching tube TR1 is used as a second input end of the current limiting circuit, the second end of the switching tube TR1 is used as a first output end of the current limiting circuit, the first end of the switching tube TR1 is connected with one end of the inductor L1 and the anode of the diode D7, the other end of the inductor L1 is used as the first input end of the current limiting circuit, and the cathode of the diode D7 is used as the second output end of the current limiting circuit.

5. The anti-impact current circuit according to claim 1, wherein the sampling off circuit comprises a resistor R6, a resistor R7, a capacitor C2 and a triode Q4; the collector of triode Q4 is as the first input of sampling shutoff circuit, and the emitter of triode Q4 is connected with one end of electric capacity C2, resistance R6's one end back, and as the first output of sampling shutoff circuit, and electric capacity C2's the other end is connected with resistance R7's one end, triode Q4's base, and resistance R7's the other end is connected with resistance R6's the other end back, and as the first input of sampling shutoff circuit.

6. The anti-surge current circuit of claim 1 wherein the turn-off delay circuit comprises a resistor R2, a resistor R3, a resistor R4, a resistor R5, a transistor Q1, a transistor Q2, a transistor Q3, a capacitor C1; the collector of the triode Q1 is used as a first input end of the turn-off delay circuit, the base is connected with one end of a resistor R2, and the emitter is connected with one end of a capacitor C1 and the emitter of the triode Q2; the other end of the resistor R2 is connected with one end of the resistor R3 and one end of the resistor R5 and then is used as a second input end of the turn-off delay circuit; the other end of the resistor R3 is connected with the base electrode of the triode Q2, the collector electrode of the triode Q2 is connected with one end of the resistor R4, the other end of the resistor R4 is connected with the base electrode of the triode Q3, the collector electrode of the triode Q3 is connected with the other end of the resistor R5, and the emitter electrode of the triode Q3 is connected with the other end of the capacitor C1 and then serves as a first output end of the turn-off delay circuit.

7. The anti-impact current circuit is applied to a switching power supply and is characterized by comprising a high-voltage power taking circuit, a driving circuit, a current limiting circuit, a sampling turn-off circuit, a turn-off delay circuit, an input port and an output port;

the high-voltage power taking circuit comprises a resistor R1, a resistor R10, a resistor R11, a switching tube TR2, a voltage stabilizing diode Z2 and a capacitor C3;

the driving circuit comprises a resistor R8, a resistor R9, a triode Q5 and a triode Q6; the current limiting circuit comprises an inductor L1, a diode D7 and a switching tube TR1;

the sampling turn-off circuit comprises a resistor R6, a resistor R7, a capacitor C2 and a triode Q4;

the turn-off delay circuit comprises a resistor R2, a resistor R3, a resistor R4, a resistor R5, a triode Q1, a triode Q2, a triode Q3 and a capacitor C1;

one end of the resistor R1 is connected with one end of the resistor R10, the cathode of the diode D7, the input vin+ of the input port and the output vo+ of the output port; the other end of the resistor R10 is connected with the first end of the switching tube TR2, and the control end of the switching tube TR2 is connected with the other end of the resistor R1 and the cathode of the zener diode Z2; the second end of the switching tube TR2 is connected with one end of the capacitor C3, the collector of the triode Q1, one end of the resistor R8 and the collector of the triode Q5; the capacitor C3 is connected with the anode of the voltage stabilizing diode Z2, the input Vin of the input port, one end of the capacitor C1, the emitter of the triode Q3, the emitter of the triode Q4, one end of the capacitor C2 and one end of the resistor R6; the other end of the resistor R8 is connected with the base electrode of the triode Q5, the base electrode of the triode Q6, one end of the resistor R2, one end of the resistor R3, one end of the resistor R5 and the collector electrode of the triode Q4; the emitter of the triode Q5 is connected with the collector of the triode Q6, one end of a resistor R9 and the control end of a switching tube TR1; the emitter of the triode Q6 is connected with the other end of the resistor R9, the other end of the resistor R6, one end of the resistor R7 and the second end of the switching tube TR1; the first end of the switching tube TR1 is connected with one end of the inductor L1 and the anode of the diode D7, and the other end of the inductor L1 is connected with the output Vo of the output port; the other end of the capacitor C2 is connected with the other end of the resistor R7 and the base electrode of the triode Q4; the base electrode of the triode Q1 is connected with the other end of the resistor R2, and the emitter electrode of the triode Q1 is connected with the other end of the capacitor C1 and the emitter electrode of the triode Q2; the other end of the resistor R3 is connected with the base electrode of the triode Q2, the collector electrode of the triode Q2 is connected with one end of the resistor R4, the other end of the resistor R4 is connected with the base electrode of the triode Q3, and the collector electrode of the triode Q3 is connected with the other end of the resistor R5.