Patent ID: 7199568
Filing Date: 2007-04-03
Classification: H02M

Abstract:
1. A DC (direct current) power supply configured to apply a DC voltage to an output terminal, said DC voltage being output from a system switched selectively between two systems, wherein at least one of said two systems comprises a switching regulator comprising: a first switching element and an inductor serially connected between an input terminal for receiving an input voltage and an output terminal; a second switching element for use in synchronous rectification connected between said first switching element and the ground; a first drive circuit for driving said first switching element; a second drive circuit for driving said second switching element; a control circuit for controlling said first and second drive circuits; a first unit for outputting a voltage proportional to an output voltage; a third switching element for interrupting a current flowing through said first unit during a period in a sleep mode; a reference voltage generator for generating a reference voltage; an operational amplifier circuit for amplifying a voltage difference between a voltage proportional to the output voltage and the reference voltage; an oscillation circuit for switching said switching regulator; a comparator for comparing between an output voltage from said operational amplifier and a further output voltage from said oscillator circuit, and for outputting square waves based on a result from the comparison; and