A power converter includes a transformer including first and second windings, a switching circuit switching voltages applied to the first winding, a power supply circuit rectifying and smoothing a current in the second winding and generating a DC voltage, an adjustment circuit adjusting the DC voltage according to an operation mode including first and second modes in which the DC voltage is adjusted to first and second voltages, the second voltage less than the first voltage, and a protection circuit including first and second Zener diodes and a switch and stopping output of the adjusted voltage. A cathode of the first diode is connected to the supply circuit, and an anode of the first diode is connected to a cathode of the second diode and the switch, and the switch is connected in parallel to the second diode and is turned on in the second mode.