Patent ID: 7453287
Filing Date: 2008-11-18
Classification: H02M,Y02B

Abstract:
1. A switching power-supply circuit that generates a predetermined output voltage by controlling a first switching transistor connected to a power supply and a second switching transistor connected between the first switching transistor and the ground, the switching power supply circuit comprising: a first driver configured to drive the first switching transistor; a second driver configured to drive the second switching transistor; a reference voltage generator configured to generate a reference voltage; a soft-start voltage generator configured to generate a soft-start voltage that increases gradually after the time of start; and an error amplifier configured to amplify an error voltage between a feedback voltage based on the predetermined output voltage and the soft-start voltage, and to control the first and second drivers in accordance with an amplified error voltage, wherein the reference voltage is inputted to the error amplifier, and the error amplifier includes an offset applying circuit having a resistor configured to apply an offset voltage to the feedback voltage and the reference voltage, and the error amplifier does not start outputting the amplified error voltage until the soft-start voltage increases to a predetermined value.