Short-circuit protection circuit using current sensor to detect IGBT overcurrent

Because there is no driving signal, the IGBT is turned off, and the power supply stops working. No current flows through the current sensor, making VA < Vref, VB = 0.2V, and C3 is discharged through R1. When C3 is discharged to make VC < Vref, IC2 outputs a low level again, and the power supply re-enters the working state. If the overcurrent continues to exist, the protection circuit returns to the original current limiting protection working state. Repeated cycles make the output drive waveform of the PWM control circuit in the interval output state, as shown in the waveform in Figure (b). Potentiometer RP1 adjusts the comparator overcurrent action threshold. Capacitor C3 is quickly charged through D5 and slowly discharged through R1. As long as the parameters of R1 and C3 are reasonably selected to make the PWM driving signal off time t2>>t1, the power supply can be guaranteed to enter the sleep state. The positive feedback resistor R7 ensures that IC2 has only two states, high and low. The D5, R1, and C3 charging and discharging circuits ensure that the output of IC2 does not frequently change between high and low levels, that is, the IGBT is not frequently turned on and off and damaged.