An object of the present invention is to diagnose an abnormality detecting circuit that detects an abnormality, such as an overcurrent of a power semiconductor, with the number of insulating elements to be additionally provided, inhibited from increasing. There are provided: a drive circuit configured to output a gate signal to a power semiconductor; an abnormality detecting circuit configured to detect an abnormality of the power semiconductor; and a diagnosis signal applying circuit configured to apply a diagnosis signal to the abnormality detecting circuit. The diagnosis signal applying circuit applies the diagnosis signal, on the basis of the gate signal output by the drive circuit.