Patent ID: 7847488

Claim:
A power supply circuit, comprising: a charge pump (CHP) type step-up circuit having multiple stages of CHP units including a first through a last CHP units and adapted to step up an inputted power supply voltage to a higher step-up voltage; an output voltage generation circuit for converting said step-up voltage into a required output voltage based on an output voltage setting signal; a voltage comparison circuit having at least one comparator for comparing the detection voltage associated with said output voltage with a reference voltage to generate a comparison signal; and a switchable control circuit for controlling the number of operable stages of said CHP type step-up circuit based on said comparison signal; wherein said output voltage generation circuit has: an output voltage setting circuit, operable at said step-up voltage, for generating an output reference voltage in accordance with said output voltage setting signal; and a buffer amplifier, operable at said step-up voltage, for amplifying said output reference voltage to said output voltage.