Patent ID: 8339816

Claim:
A semiconductor device used for controlling a switching power supply apparatus which supplies a regulated output direct current voltage to a load by causing a switching element to switch an input direct current voltage on and off, said semiconductor device comprising: a turn-on control circuit which generates a turn-on signal which is used for periodically turning on the switching element; a feedback control circuit which generates a first reference voltage indicating a limitation level value for a current flowing into the switching element, by referring to a feedback signal indicating a degree of the output direct current voltage, the limitation level value decreasing as the output direct current voltage becomes greater; a current detecting terminal to which a sense voltage is applied, the sense voltage being greater as the current flowing into the switching element is greater; an offset current generating circuit which provides an offset current from said current detecting terminal, the offset current being greater as the output direct current voltage indicated by the feedback signal is greater; a turn-off control circuit which generates a turn-off signal which is used for turning off the switching element, by comparing the sense voltage applied to said current detecting terminal with the first reference voltage; a driving circuit which turns on and off the switching element according to the turn-on signal and the turn-off signal; an overcurrent protection level setting circuit which generates a second reference voltage indicating an overcurrent protection level value for the current flowing into the switching element; and an intermittent oscillation control circuit which keeps the switching element off in the case where the first reference voltage is small enough to satisfy a predetermined reference, wherein said turn-off control circuit generates the turn-off signal, by comparing the sense voltage applied to said current detecting terminal with each of the first reference voltage, and the second reference voltage.