Patent ID: 8164315

Claim:
A power supply circuit in which an output of a switching regulator section and an output of a series regulator section are switched and output to an overall output terminal, the power supply circuit comprising: a switching regulator output unit which activates the switching regulator section, switches a first loop switching switch provided between the switching regulator section and the overall output terminal to an ON state, to form a feedback loop between the overall output terminal and an error amplifier of the switching regulator section, stops operation of the series regulator section, and switches a second loop switching switch between the series regulator section and the overall output terminal to an OFF state, to output the output of the switching regulator section to the overall output terminal; a series regulator output unit which activates the series regulator section, switches the second loop switching switch to an ON state, stops operation of the switching regulator section, and switches the first loop switching switch to an OFF state, to open the feedback loop between the overall output terminal and the error amplifier and output the output of the series regulator section to the overall output terminal; and a transition process unit which applies a transition process in which, when a state is switched from a state where the output of the series regulator section is output to the overall output terminal to a state where the output of the switching regulator section is output to the overall output terminal, the first loop switching switch is switched to an OFF state while the series regulator section and the switching regulator section are activated, to temporarily open the feedback loop of the switching regulator section, the second loop switching switch is maintained in the ON state, to output the output of the series regulator section to the overall output terminal, an artificial feedback loop is formed between an output terminal of the error amplifier and a second terminal of the error amplifier, to output a voltage corresponding to the output of the series regulator section on the output terminal of the error amplifier and charge a phase compensating capacitor of the switching regulator section with the output voltage, and then, the artificial feedback loop is opened, to re-form the feedback loop between the overall output terminal and the error amplifier of the switching regulator section.