A power supply circuit is a power supply circuit that generates a direct current (DC) voltage from an alternating current (AC) voltage, and includes a rectifying circuit that rectifies the AC voltage, a capacitor that smooths the rectified voltage, a first switching element disposed on a path for charging the capacitor, a comparison circuit that compares an index voltage depending on the smoothed voltage with a reference voltage, and a driving circuit that sets the first switching element to an ON state, in a state in which the index voltage is lower than the reference voltage, and sets the first switching element to an OFF state, in a state in which the index voltage exceeds the reference voltage.