Patent ID: 7825646
Filing Date: 2010-11-02
Classification: H02M

Abstract:
1. A step-up converter, having an inductor and a main switch connected in series, a rectifier for rectifying the voltage across the two terminals of said main switch and a smoothing section for smoothing the rectified voltage, for stepping up an input DC voltage input to said inductor by the ON/OFF operation of said main switch and outputting an output DC voltage from said smoothing section, comprising: a current detector for generating a current detection signal corresponding to the current of said rectifier; an error amplifier for generating an error signal corresponding to said output DC voltage; and a control circuit for turning ON/OFF said main switch on the basis of said current detection signal and said error signal, wherein said rectifier is a rectifying transistor for alternately turning ON/OFF said main switch, said current detector is equipped with a detection transistor so that said detection transistor and said rectifying transistor form a current mirror circuit at least when turned ON to generate said current detection signal on the basis of the current of said detection transistor, and said current detector is equipped with a differential amplifier to which the voltages at the current output terminals of said rectifying transistor and said detection transistor are input and an adjustment transistor, the conduction resistance of which is adjusted using the output of said differential amplifier, and said adjustment transistor is connected to the current output terminal of said detection transistor to generate said current detection signal on the basis of the current of said detection transistor flowing via said adjustment transistor.