Patent ID: 8159846

Claim:
A switching control circuit comprising: a switching device being switched between an ON state and an OFF state repeatedly, a current detection circuit operable to detect the magnitude of the current flowing through said switching device and to generate a current detection signal, a target level setting circuit operable to set the target level of the current detection signal, a comparison circuit operable to compare the level of the current detection signal with the target level and to generate a comparison result signal, a drive signal generating circuit operable to generate a drive signal whose level periodically changes from a first level to a second level and changes from the second level to the first level on the basis of the comparison result signal, a comparison result signal nullification circuit operable to generate a nullification period to nullify the comparison result signal on the basis of the drive signal immediately after the level of the drive signal was changed from the first level to the second level, and a nullification period adjustment circuit operable to generate a nullification period adjustment signal representing a signal for adjusting the nullification period after detecting the overcurrent state of said switching device on the basis of the current detection signal, wherein said switching device is in the ON state when the level of the drive signal is the first level and is in the OFF state when the level of the drive signal is the second level, and the period of the ON state is shortened when the nullification period adjustment circuit is generated.