Patent ID: 7834651

Claim:
A power supply circuit that supplies an electronic device with a supply power, comprising: a voltage control section that outputs a control voltage tracking an input voltage with a prescribed frequency characteristic and applies a voltage corresponding to the control voltage to the electronic device; a voltage adjusting section that detects the voltage applied to the electronic device and adjusts the input voltage based on the detected voltage; a current adjusting section that detects a current applied to the electronic device and adjusts the input voltage when the detected current is outside of a prescribed limit range; and a frequency characteristic adjusting section that increases a speed at which the control voltage tracks the input voltage by adjusting the frequency characteristic of the voltage control section when the applied current is outside of the limit range; wherein the voltage control section comprises: a control voltage output section including first input, second input, and output terminals, the first input terminal receiving the input voltage, and the output terminal outputting the control voltage based on a voltage received by the second input terminal and the input voltage; and a feedback section that feeds the control voltage output by the control voltage output section back to the second input terminal, and the frequency characteristic adjusting section reduces a time constant of the feedback section when the applied current is outside of the limit rang; wherein the feedback section includes: a feedback circuit that connects the second input terminal and the output terminal of the control voltage output section to each other; a capacitor section that is serially provided on the feedback circuit between the second input terminal and the output terminal of the control voltage output section; and a resistance section that is provided between the feedback circuit and a ground potential, and the frequency characteristic adjusting section reduces at least one of a resistance of the resistance section and a capacitance of the capacitor section when the applied current is outside of the limit range.