SEMICONDUCTOR SWITCH WITH OVERCURRENT CUTOFF FUNCTION

摘要

PROBLEM TO BE SOLVED: To provide a semiconductor switch with an overcurrent cutoff function that shifts at high speed to an OFF state by speeding up the charge elimination at the control end of the semiconductor switch device when the overcurrrent cutoff operation on the semiconductor switch has actuated normally. SOLUTION: When the overcurrent cutoff is actuated, the source current of the output N-type MOSFET Q1 exceeds the prescribed current; when the voltages at both ends of a resistance R1 exceeds the ON threshold of the N-type MOSFET Q3 the current is determined to be an overcurrent. The overcurrent is cut off with the cutoff N-type MOSFET Q2 maintaining the ON state and the output N-type MOSFET Q1 going into an OFF state with the gate voltage becoming roughly 0 V. At this time, the charge accumulated in the reverse bias circuit B1 during normal operation is discharged via the capacity between the gate sources of the output N-type MOSFET Q1 so that a reverse bias is applied to the output N-type MOSFET Q1.