SWITCHING POWER SUPPLY APPARATUS

A DC/DC converter has a EFT, and converts a power supply voltage from EDLC by turning on and off the FET. A control unit outputs a first PWM signal whose duty gradually decrease from 100% to the FET when the power supply from the EDLC to the DC/DC convertor is started. Thereafter, the control unit outputs a second PWM signal having a duty controlled so that an output voltage or an output current of the DC/DC converter becomes a reference value to the FET.