| 摘要 |
PROBLEM TO BE SOLVED: To provide a step-up circuit capable of applying an optimal step-up voltage constantly to a voltage output terminal even when the power supply voltage is varied. SOLUTION: The step-up circuit 100 comprises a voltage detection circuit 79 for detecting the power supply voltage, and a switch means 80 for selecting a diode and a capacitor being used for step-up among a plurality of diodes 71-73 and a plurality of capacitors 74-76 depending on the power supply voltage detected by the voltage detection circuit 79. Voltage output terminal N2 is applied with a first step-up voltage obtained by doubling the power supply voltage applied to voltage output terminal N1 when the power supply voltage detected by the voltage detection circuit 79 is higher than a predetermined potential otherwise applied with a second step-up voltage obtained by tripling the power supply voltage applied to the voltage output terminal N1 and higher than the first step-up voltage. COPYRIGHT: (C)2006,JPO&NCIPI
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