Patent ID: 7893667
Filing Date: 2011-02-22
Classification: H02M,Y02B

Abstract:
1. A power supply apparatus comprising: an output transistor to generate an output voltage from an input voltage by being turned on and off; an error amplifier to amplify a voltage difference between a feedback voltage commensurate with the output voltage and a predetermined reference voltage to generate an error voltage; a PWM comparator to compare the error voltage with a predetermined slope voltage to generate a PWM signal having a duty ratio corresponding to a result of comparison; and on/off control means to turn on and off the output transistor with the PWM signal, wherein the PWM comparator is operable to keep the slope voltage shifted from a ground potential to a higher voltage by a predetermined offset voltage so that a lower limit level of the slope voltage is higher than a lower limit level of the error voltage; the PWM comparator comprising, in an input stage thereof: