A power supply includes a second capacitor, an overcharge suppression circuit, a power supply circuit, and a controller. The controller includes: an overcharge suppression control circuit that controls the overcharge suppression circuit in accordance with a magnitude of a voltage of the second capacitor; and a resistance switching circuit that changes a resistance value of the current-limiting resistance circuit depending on whether a gate block state occurs or not and in accordance with a magnitude of the voltage of the first capacitor. In the gate block state, each of the switching elements is fixed in a non-conductive state.