Patent ID: 6979985

Claim:
A switching power supply device comprising: a first power source node and a second power source node; a first switching element coupled between the first power source node and an output node; a second switching element coupled between the second power source and the output node; a comparison circuit having a hysteresis characteristic; a series circuit including a first resistor element and a first capacitor element coupled via a first controlling node therebetween, the first controlling node producing a first controlling voltage which is input to one input of a first comparator of the comparison circuit; a smoothing circuit comprising a first circuit element and a second capacitor element, the smoothing circuit being coupled between the output node and the second power source node, the first circuit element being coupled to the series circuit in parallel, the second capacitor element being coupled to a load in parallel; and wherein the comparison circuit discriminates the first controlling voltage with a first threshold voltage and a second threshold voltage, and the comparison circuit outputs a discrimination result to control the first switching element and the second switching element so as to effect the first controlling voltage in response to variation of the power supply provided to the load.