Patent ID: 7755340

Claim:
A control circuit for controlling a step-up switching regulator, comprising: a switching transistor having one end connected to the ground; a first terminal to which the other end of said switching transistor is connected; a second terminal to which the other end of an inductor whose one end is to be connected to said first terminal is connected; a third terminal to which an input voltage is applied; an auxiliary transistor disposed between said second terminal and said third terminal; a first soft start circuit that generates a first soft start voltage that increases with lapse of time; a second soft start circuit that generates a second soft start voltage that increases with a delay to said first soft start voltage; an error amplifier that controls a voltage of a control terminal of said auxiliary transistor on the basis of an error voltage between the output voltage of said step-up switching regulator and said first soft start voltage; a pulse width modulator that receives an input of the output voltage of said step-up switching regulator and a voltage obtained by shifting said second soft start voltage by a predetermined voltage, and generates a pulse width modulation signal whose duty ratio is controlled so that the two voltages will be approximated to each other; and a driver circuit that drives said switching transistor on the basis of said pulse width modulation signal.