Patent ID: 7965070
Filing Date: 2011-06-21
Classification: H02M

Abstract:
1. A switching power supply for controlling on/off of a switching element to generate a prescribed output voltage, comprising: an error amplifier, which compares the output voltage, or a divided voltage thereof, with a reference voltage and outputs an error signal according to a difference therebetween; current detection means, which detects a current flowing in the switching element; a slope compensation circuit which generates a slope compensation signal to prevent subharmonic oscillation; and an added slope circuit, which generates an added slope signal that is reset to zero prior to turn-on of the switching means, begins to increase when the switching means turns on and is stopped from increasing after a prescribed time shorter than a switching period of the switching element, wherein a first sum signal is determined by adding an output of the current detection means and the added slope signal, and wherein a second sum signal, obtained by further adding the slope compensation signal to the first sum signal, is compared with the error signal, and the switching element is turned off when the second sum signal becomes equal to the error signal.