<p>A power supply apparatus includes a power supply circuit (100) for converting an input voltage (Vin) into an output voltage (Vout) and supplying the output voltage to a load (160). The power supply circuit (100) includes a plurality of voltage conversion circuits (110,120) having different conversion efficiencies, and a selection circuit (150) for selecting one of the plurality of voltage conversion circuits so as to improve a conversion efficiency of the power supply circuit (100).</p>
