PURPOSE: To quicken the switching speed without causing a surge voltage by bring the output of a driving circuit to a high impedance state depending on an output current when the output current in excess of the short-circuit protection level flows from the output of a current detector so as to make a gate discharge transistor(TR) conductive.

CONSTITUTION: When a current in excess of the short-circuit protection level flows to a MOS group power TR 1, a current detector 5 detects the overcurrent and gives an H level signal to a short-circuit protection circuit 3, which brings the output of a driving circuit 2 into a high impedance state Z. Simultaneously, the gate of the MOS group power TR 1 is discharged through a gate resistor 6 to turn off the MOS group power TR 1. Thus, a usual switching speed is quickened and a surge voltage at short-circuit protection is reduced.