Patent ID: 7557547

Claim:
A power supply device comprising: a rectification circuit for rectifying the output of an AC power generator and a DC voltage reduction means for stepping down the DC output from the rectification circuit, said voltage reduction means is a non-insulation type DC/DC converter; a self-excited oscillation type converter having a primary side connected to the output side of said non-insulation type DC/DC converter and a secondary side used as the power supply output; a switching means for performing duty control on said non-insulation type DC/DC converter; and a switching-means driving circuit which maintains said switching means at an ON state until the AC output voltage from said AC power generator exceeds a predetermined value generated by an oscillation circuit when compared in a comparator circuit and starts the duty control with said switching means at the time when said AC output voltage exceeds the predetermined value, wherein the switching-means driving circuit includes said oscillation circuit and said comparator circuit.