A rectification circuit rectifies an alternating current voltage of an alternating current power supply. A parallel converter comprises converters that correspond to phases and that are connected in parallel to an output terminal of the rectification circuit. Each converter comprising a reactor, a switching circuit that is connected in series to the reactor and a diode that is connected in series to the reactor. A smoothing capacitor is connected to an output terminal of the parallel converter. A control circuit generates pulse signals corresponding to phases based on an error voltage between an output voltage of the smoothing capacitor and a reference voltage and on an output voltage of the rectification circuit, and switches the switching circuits in the converters using the pulse signals. Current detection circuits are provided corresponding to the converters and that detect currents flowing through the switching circuits.