Patent ID: 7486059

Claim:
A power-supply circuit for supplying voltage to a load, comprising: a power supply that generates power-supply voltage; an inverted outputting circuit having a positive voltage terminal for outputting positive voltage based on said power-supply voltage and a negative voltage terminal for outputting negative voltage generated based on said power-supply voltage and having different polarity from said positive voltage and outputting said positive and negative voltage while keeping the same direction in terms of the directions of electric current flowing between said positive voltage terminal and the outside of the inverted outputting circuit and of electric current flowing between said negative voltage terminal and the outside of the inverted outputting circuit; a step-down output circuit for supplying predetermined step-down output voltage to the outside of the inverted outputting circuit by connecting said positive voltage terminal and said negative voltage terminal to the outside of the inverted outputting circuit while switching said positive and negative voltage terminals with a predetermined duty ratio; and a step-up output circuit for supplying step-up output voltage whose absolute value is greater than that of said step-down output voltage by switching whether or not to connect said step-down output circuit with said load with a predetermined duty ratio.