A power source device is so arranged that one of switching elements forming a plurality of power conversion switching circuits which is used in common during each switching cycle is made to have a switching period in which mainly a current is taken up from a power source of first one of the switching circuits, the switching period being varied in a zone in which an input voltage is higher than a predetermined voltage in a cycle of input voltage waveform. Any distortion of input current waveform occurring around lower voltage period of commercial AC source is thereby reduced, in the power source device wherein the power conversion switching circuits employ commonly the switching elements.
