A power supply circuit includes a standard voltage generator; a regulator to control an output voltage, and to be capable of being switched ON/OFF; a capacitor in parallel between the standard voltage generator and the regulator; a discharging circuit including a first switch and a second switch configured to discharge electrical charges from the capacitor via the second switch while the regulator is in an OFF state; and a starting controller configured to transmit a signal for controlling the first switch and the second switch. The first switch is connected in series between the standard voltage generator and the regulator. The second switch has one end connected to a connection node between the first switch and the regulator, and has another end connected to a ground. When the first switch is in OFF state, the second switch is turned to ON state while the regulator is in OFF state.