Patent ID: 7483250

Claim:
A drive circuit for controlling a switching device ON/OFF, comprising: a short circuit detection means that detects short circuit of the switching device; a soft cutoff means that performs a soft-cutoff function by gradually decreasing the gate terminal voltage of the switching device when short circuit is detected by the short circuit detection means; wherein the switching device is one with voltage driven sense function, which is provided with a gate terminal, terminal No. 1, terminal No. 2, and terminal No. 3, with the main current applied between the terminal No. 1 and terminal No. 2 and the sense current in proportion to the main current is applied between the terminal No. 1 and terminal No. 3 by applying voltage to the gate terminal, a gate voltage detection means that detects the gate terminal voltage of the switching device; and an ON-pulse retention means that retains the drive circuit output ON when the gate terminal voltage detected by the gate voltage detection means exceeds a specified value and also the sense current of the switching device exceeds a specified value so that the soft cutoff function continues to operate when the short circuit is detected while preventing breakdown when a narrow pulse is inputted.