Patent ID: 8093878

Claim:
A switching power supply device comprising: a first capacitor having an output voltage generated there across; an inductor in the current supply path to said first capacitor; a switching circuit that switches voltage applied to said inductor responsive to an input control signal; a ripple signal generator that generates a ripple signal corresponding to the ripple current flowing through said inductor on the basis of the voltage applied to said inductor, wherein said ripple signal generator has an integrator containing a second capacitor that generates a voltage corresponding to the integration value of the voltage applied to said inductor; a comparator that compares a synthetic signal of a voltage feedback signal corresponding to said output voltage and said ripple signal with a reference signal, or compares said synthetic signal of the ripple signal and reference signal with the voltage feedback signal corresponding to said output voltage; a controller that generates said control signal corresponding to the comparison result of said comparator so that the peak or trough of said synthetic signal is equal to said reference signal or said voltage feedback signal; and an amplitude converter that generates said ripple signal, which is a signal related to the ripple voltage generated at said second capacitor, whose amplitude is less than said ripple voltage.