A direct current (DC) power supply apparatus includes an input unit configured to receive an outside DC power; a plurality of polarity correction units configured to correct the polarity of the outside DC power; a plurality of switch units installed to correspond to each of the plurality of polarity correction units; a detection unit configured to detect a flow of current of the plurality of polarity correction unit; and a control unit configured to determine a polarity correction unit, at which current of DC power flows, among the plurality of correction units based on a detection signal of transmitted from the detection unit, and control the switch unit corresponding to the determined polarity correction unit at an ON position such that the current of DC power flows through the switch unit which is controlled at the ON position.