Patent ID: 8044642
Filing Date: 2011-10-25
Classification: H02M,Y02B

Abstract:
1. A power supply device comprising: a synchronous rectifier step-down converter to alternately turn on and off a switch and a synchronous rectifier switch; a reference voltage generator to generate a predetermined reference voltage; an error amplifier to output an error voltage such that an output voltage of the step-down converter approaches the predetermined reference voltage; a pulse-width signal generator to generate a pulse-width signal controlling timing of turning on and off the switch and the synchronous rectifier switch based on the error voltage; a driver circuit to control turning on and off the switch and the synchronous rectifier switch based on the signal generated by the pulse-width signal generator; an inductor connected in series with output of the step-down converter; a bypass switch to short-circuit an output terminal of the step-down converter to an input terminal of the step-down converter; and a mode controller to control turning on and off the bypass switch, wherein, while the bypass switch is turned on, output of the error amplifier having a reference voltage value that is set to a predetermined divided voltage ratio of the output voltage is inverted.