Patent ID: 7362591

Claim:
A power supply device comprising: a PWM signal generation circuit that generates a PWM signal; a control power supply circuit that supplies power in accordance with said PWM signal to an electric load; a detection unit that detects one of a supply voltage value and a supply current value of power supplied to said electric load; a determination unit that determines a deviation of a detection value detected by said detection unit from a target value; and a pulse width control unit capable of executing a forward control to change a pulse width of said PWM signal in a direction where said detection value is brought to be close to said target value, and a reverse control to change said pulse width of said PWM signal in a direction opposite to that of said forward control, wherein said pulse width control unit executes said forward control when said determination unit determines that said deviation exists, and then executes said reverse control when said determination unit makes at least one of determinations that said deviation does not exist, and a magnitude relationship between said detection value and said target value is inverted.