When an insulated gate bipolar transistor turned on starts to transition to turn off, the insulated gate bipolar transistor has between the emitter and the collector a surge voltage caused in proportion to the magnitude of a current gradient provided when a current flowing through a coil in switching is interrupted and an electrode interconnect inductance internal to an inverter circuit. A MOS transistor is temporarily turned on within a period of time for which the insulated gate bipolar transistor turned on transitions to turn off. This can bypass a portion of the current to the MOS transistor. This can provide an alleviated apparent current gradient of the current and thus alleviate or prevent a surge voltage caused at the insulated gate bipolar transistor.