To reduce a surge voltage generated when turning off switching elements due to an overcurrent, in a power supply unit having a plurality of switching elements.

A control device 40 generates upper arm control signals for controlling upper arm switching elements 11, 21, 31 and lower arm control signals for controlling lower arm switching elements 12, 22, 32. An interrupt signal generation circuit 50 generates an upper arm interrupt signal and a lower arm interrupt signal when the overcurrent is detected. The upper arm interrupt signal is obtained by delaying the lower arm interrupt signal with a delay circuit 52. A lower arm interrupt circuit 70 interrupts the lower arm control signals when the lower arm interrupt signal is inputted, while an upper arm interrupt circuit 60 interrupts the upper arm control signals when the upper arm interrupt signal is inputted.