A switch circuit is configured of a first semiconductor element and a second semiconductor element connected in series, and receives a DC voltage of 100 V or more. The drive circuit causes the first semiconductor element or the second semiconductor element to perform a switching operation. The isolated power supply circuit converts a predetermined power supply voltage into an isolated first power supply voltage, and outputs the first power supply voltage to the drive circuit. The isolation signal converter converts a first signal of 6 MHz or more into an isolated first drive signal, and outputs the first drive signal to the drive circuit. The single substrate mounts the isolated power supply circuit and the isolation signal converter. Both the first semiconductor element and the second semiconductor element are wide bandgap semiconductor elements.