Soft turn-off active clamp protection circuit and power system

1. A soft turn-off active clamp protection circuit, connected with a MOSFET and configured for controlling turn-off of the MOSFET, wherein the circuit comprises a gate connection terminal, a drain connection terminal, a source connection terminal, a discharge capacitor, an overvoltage signal acquisition module, a negative feedback module, a discharge current control module and a turn-off control module;

the gate connection terminal is connected with a gate of the MOSFET;

the source connection terminal is connected with a source of the MOSFET;

the drain connection terminal is connected with a drain of the MOSFET;

the gate connection terminal, the drain connection terminal and the source connection terminal are connected with each other;

one end of the discharge capacitor is connected with the gate connection terminal, and the other end of the discharge capacitor is connected with the drain connection terminal;

the overvoltage signal acquisition module is connected between the source connection terminal and the drain connection terminal;

the discharge current control module and the turn-off control module are connected in series between the gate connection terminal and the source connection terminal;

the negative feedback module is connected to the overvoltage signal acquisition module and the discharge current control module;

the overvoltage signal acquisition module is configured for being turned on when an overvoltage signal is acquired;

the negative feedback module gives negative feedback to the discharge current control module when the overvoltage signal acquisition module is turned on, and the discharge current control module controls a discharge current of the discharge capacitor according to the negative feedback, thereby controlling an output current of the gate connection terminal; and

the turn-off control module is turned off or turned on according to the intended output of the gate connection terminal.

2. The soft turn-off active clamp protection circuit according to claim 1 , wherein the overvoltage signal acquisition module comprises a first diode, a first resistor and a second resistor which are sequentially connected in series, a cathode of the first diode is connected with the drain connection terminal, the negative feedback module comprises a control terminal, the control terminal of the negative feedback module is connected between the first resistor and the second resistor, and an other end of the second resistor is connected with the source connection terminal.

3. The soft turn-off active clamp protection circuit according to claim 2 , wherein the first diode is a Zener diode.

4. The soft turn-off active clamp protection circuit according to claim 2 , wherein the overvoltage signal acquisition module further comprises a first capacitor, and the first capacitor is connected with the first diode in parallel.

5. The soft turn-off active clamp protection circuit according to claim 1 , wherein the negative feedback module comprises a fourth resistor and a first triode; one end of the fourth resistor is connected with the drain connection terminal, and the other end of the fourth resistor is connected with a collector of the first triode; an emitter of the first triode is connected with the source connection terminal, a base of the first triode is connected with the overvoltage signal acquisition module, and the base of the first triode is a control terminal of the negative feedback module; and the discharge current control module comprises a control terminal, and the control terminal of the discharge current control module is connected to the other end of the fourth resistor.

6. The soft turn-off active clamp protection circuit according to claim 1 , wherein the discharge current control module comprises a second triode; a base of the second triode is a control terminal of the discharge current control module; and the base of the second triode is connected with the negative feedback module, a collector of the second triode is connected with the turn-off control module, and an emitter of the second triode is connected with the source connection terminal.

7. The soft turn-off active clamp protection circuit according to claim 6 , wherein the discharge current control module further comprises a fifth resistor, and the second triode is connected with the fifth resistor in series.

8. The soft turn-off active clamp protection circuit according to claim 1 , wherein the turn-off control module comprises a third triode; a base of the third triode is connected with a MOS driving module through a second diode, the base of the third triode is connected with an anode of the second diode, a collector of the third triode is connected with the gate connection terminal, and an emitter of the third triode is connected with the discharge current control module; and the MOS driving module is connected with the gate connection terminal through a third diode, and the gate connection terminal is connected with a cathode of the third diode.

9. A power system comprising a charging and discharging circuit and the soft turn-off active clamp protection circuit according to claim 1 ; wherein

the charging and discharging circuit comprises a power supply and the MOSFET, the power supply, the MOSFET and a load constitute a loop, and the soft turn-off active clamp protection circuit is connected with the MOSFET; and

a control system of the power supply comprises a MOS driving module, the MOS driving module is connected with the turn-off control module and the gate connection terminal, and the MOS driving module controls turn-off or turn-on of the turn-off control module according to the output current of the gate connection terminal.