A turn-off feedback unit (23OFF) of a semiconductor device driving unit generates a feedback voltage as part of a voltage of a drive signal for establishing electrical continuity or disconnection in a bus according to a temporal variation of a collector current of a first semiconductor device (11U) when the first semiconductor device (11U) is turned off from on. A turn-on feedback unit (23ON) generates the feedback voltage according to a commutation current flowing through a free wheeling diode (12D) connected to a second semiconductor device (11D) when the first semiconductor device (11U) is turned on from off.