Abstract: In a power conversion circuit operating with high frequency, an off-voltage control circuit 101u of a lower-arm gate drive circuit 24u controls the output voltage of a gate drive power supply 103u to change the output voltage to a voltage lower than a predetermined off voltage during a time period from termination of turn-off operation of a lower arm 22u until start of turn-on operation of an upper arm 21u, and thereafter return the output voltage to the predetermined off voltage immediately after termination of the turn-on operation of the upper arm 21u. With this control, short-circuiting through the upper and lower arms occurring due to a high voltage change dv/dt can be avoided, and the life of a switching element constituting the power conversion circuit improves, increasing the reliability of the power conversion circuit.

Abstract: A high-side MOSFET (12) is connected in parallel to a high-side MOSFET (11) via an inductor (13). When the flow-out of a current is started, the high-side MOSFET (12) is turned on earlier. A recovery current of a body diode (21a) of the low-side MOSFET (21) flows via the inductor (13) and the high-side MOSFET (12), and therefore, the rate at which the current changes over time can be suppressed to a lower level. Thereafter, the high-side MOSFET (11) for a main current is turned on, and the high-side MOSFET (12) for suppressing a recovery current is turned off, whereby the former causes a current to flow out. When the high-side MOSFET (11) to turned off to stop the flow-out of a current, surge is not caused by the inductor (13).