Patent ID: 7545657

Claim:
A switching power source apparatus comprising: a switching element connected through a primary winding of a transformer to a DC power source; a control circuit configured to control ON/OFF operation of the switching element; a start circuit configured to supply a source voltage to the control circuit so that a starting current passes through the control circuit; a first rectify-smooth circuit configured to rectify and smooth a voltage generated by a secondary winding of the transformer into an output voltage and supply the output voltage to a load; and a second rectify-smooth circuit configured to rectify and smooth a voltage generated by a tertiary winding of the transformer into a source voltage to be supplied to the control circuit, wherein the start circuit is configured to: supply a first starting current generated from the DC power source to start the apparatus, and once the apparatus has started, stop the first starting current; if the source voltage to the control circuit decreases to a turn-off voltage after the apparatus has started, supply a second starting current that is smaller than the first starting current; and if the source voltage to the control circuit further decreases to a predetermined voltage that is lower than the turn-off voltage, supply the first starting current.