Patent ID: 8644036

Claim:
A switching power supply device that converts an AC power supply inputted to a primary side into a plurality of secondary side DC power supplies for output, wherein: one DC power supply of the plurality of secondary side DC power supplies being a stabilized output having voltage stabilizing means for taking an output voltage by rectification smoothing a first secondary winding to stabilize the output voltage by feeding back the output voltage to the primary side; the rest of the plurality of secondary side DC power supplies being non-stabilized outputs not having voltage stabilizing means for taking the output voltage by rectificatior smoothing a second secondary winding to control the output voltage to the primary side or a secondary side; the output voltage from the stabilized output is set higher than the output voltage from a non-stabilized output of said non-stabilized outputs; a step-up/down converter is connected between the stabilized output and the non-stabilized output; and the step-up/down converter uses the step-down converter function to step-down the output voltage of the stabilized output to supply power to the non-stabilized output when the output voltage of the non-stabilized output falls below a first predetermined voltage, and uses the step-up converter function to step-up the output voltage of the non-stabilized output to regenerate power to the stabilized output when the output voltage of the non-stabilized output exceeds a second predetermined voltage.