POWER SUPPLY DEVICE

An AC switch that includes a semiconductor switch and a snubber circuit connected in parallel between a first terminal connected to an AC power supply via a circuit breaker and a second terminal connected to a load. The power converter is connected between a power storage device and the second terminal. The current detector detects a current flowing through the AC switch. When the AC power supply is normal, the controller turns on the semiconductor switch. When an open state of the circuit breaker is detected, the controller controls the power converter to supply a current having a phase opposite to that of the current detected by the current detector to flow through the semiconductor switch and supply the AC power to the load. The controller further turns off the semiconductor switch in response to that the amplitude of the current detected by the current detector is 0.