| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply circuit which is low in power consumption and capable of efficiently stepping up a voltage. SOLUTION: A power supply source is composed of a step-up circuit 1 and a control circuit 2, which controls the step-up circuit 1. The step-up circuit 1 is composed of capacitors formed on a semiconductor substrate and a switch which switches the connection of wirings to the capacitors. The control circuit 2 turns switching on or off and connects capacitors together in parallel, and the capacitors are charged with the voltage VDD of a power supply. The control circuit 2 charges stray capacitances with the voltage VDD of a power supply, so as to suppress the amount of charge supplied to the stray capacitances which accompany without fail on capacitors from the capacitors, when a stepped-up voltage is outputted. Thereafter, the control circuit 2 generates a stepped-up voltage VUOUT higher than the power supply voltage connecting the charged capacitors together in series and outputs it to an external device.
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