Patent ID: 7106031
Filing Date: 2006-09-12
Classification: H02M,Y02B

Abstract:
1. A power supply apparatus comprising: a switching power supply circuit, provided with a switching device in a path defined from an input terminal to an output terminal, for turning on and off the switching device to convert an input voltage applied to the input terminal into an output voltage which is lower than the input voltage, and for outputting the output voltage from the output terminal; a voltage reducing power supply circuit, provided with a control transistor in a path defined from an input terminal to an output terminal, for adjusting a conduction condition of the control transistor under an ON state to reduce an input voltage applied to the input terminal to a target output voltage, and for outputting the target output voltage from the output terminal; and a switching circuit for selectively applying any one of the input voltage applied to the input terminal of the switching power supply circuit and the output voltage outputted from the output terminal of the switching power supply circuit to the input terminal of the voltage reducing power supply circuit, wherein the switching circuit applies the input voltage applied to the switching power supply circuit to the voltage reducing power supply circuit when the supply of the input voltage to the switching power supply circuit is commenced, and thereafter switches the input voltage applied to the voltage reducing power supply circuit to the output voltage outputted from the switching power supply circuit when a predetermined condition is established.