A power supply circuit includes, an input part, which has a first input terminal and a second input terminal, and which is configured to connect to an alternating current power supply; a line capacitor that is connected to the first input terminal and the second input terminal; a rectification circuit, which is connected to the first input terminal and the second input terminal, which rectifies and outputs to a load circuit from a high voltage side output terminal and a low voltage side output terminal; a smoothing capacitor, which is connected between the high voltage side output terminal and the low voltage side output terminal, and a remaining charge discharge unit that, when the alternating current flowing is interrupted, detects the interruption and discharges electrical charges remaining in the line capacitor, based on electrical charges of the high voltage side output terminal or charges of the smoothing capacitor.