Patent ID: 8115461

Claim:
A power supply circuit, that steps down an input voltage and outputs it, comprising: a charge pump circuit for outputting an intermediate voltage in which the input voltage has been stepped down; a voltage regulator circuit including an active element circuit being connected between an output terminal of the intermediate voltage of the charge pump circuit and an output terminal of the power supply voltage and a feedback control circuit for feedback-controlling the active element circuit so that the power supply voltage approaches a predetermined voltage; a voltage detecting circuit for detecting said input voltage or the voltage being applied to the active element circuit; a control circuit that switches the operating mode of the charge pump circuit so that the step-down ratio is increased if the voltage being detected in the voltage detecting circuit exceeds a predetermined voltage threshold; and a power detecting circuit for detecting the power being consumed in the active element circuit; the charge pump circuit has several operating modes with different step-down ratios; and the control circuit judges whether or not the voltage being detected in the voltage detecting circuit is included in any of several predetermined voltage ranges and switches the operating mode of the charge pump circuit so that it is operated at a step-down ratio in which the allowable upper limit for a voltage range of said judgment result is not exceeded and a step-down ratio in which the power consumption being detected is smaller than a predetermined power threshold, if the power consumption being detected in the power detecting circuit is larger than the predetermined power threshold.