Patent ID: 8655216

Claim:
A switching power supply device comprising: a transformer configured to include a primary winding, a secondary winding, and an auxiliary winding; a switching unit configured to switch a current that flows through the primary winding of the transformer; a control unit configured to control a switching operation of the switching unit, the control unit including a power supply terminal to which a power-supply voltage is supplied and an ON/OFF terminal for activating the control unit; a starting resistor connected between a voltage input side of the primary winding and the power supply terminal of the control unit; a voltage supply unit configured to rectify and smooth a voltage output from the auxiliary winding and supply the rectified and smoothed voltage to the power supply terminal; and a timing control unit configured supply a value according to a voltage to be input to the primary winding to the ON/OFF terminal of the control unit so as to control startup timing of the control unit.