PURPOSE: To lighten he stress of an element by equipping it with a means, which charges the capacitor of a variable voltage source quickly after an overcurrent detecting means detects normal ON condition at the time turning on a voltage driving semiconductor element.

CONSTITUTION: In the case turning on operation of an IGBT element Q1, when a photocoupler PH1 is turned on, a transistor T1 is turned off, and an output transistor T2 is turned on, and T3 is turned off, and ON gate voltage V1 is applied between the gate and the emitter of an IGBTQ1, and Q1 starts to turn on. At this time, T11 and T20 are also turned off together with the transistor T1, so a Zener diode ZD1 becomes ON through a resistor R11 by the OFF of the transistor T11, and transistors T21 and T4 are turned on. And, when it detects that the collector voltage of the element Q1 has dropped to normal turn off voltage after start of the turn off, the gate voltage is established and turn off is ensured by immediately charging the capacitor C2 of an overcurrent soft breaking circuit quickly.