Control circuit and switching power source

Abstract

Provided is a control circuit for controlling an ON period and an OFF period in a switching cycle of a switching element configured to perform switching control of a principal current flowing through a transformer of a switching power source, and performing control to turn off the switching element when an overcurrent is detected after an elapse of an invalidation period in the switching cycle and to set a period in which the switching element is turned on in the switching cycle to be minimum period or more, the control circuit including a shared timer unit configured to output a first timer signal for defining the invalidation period and a second timer signal for defining the minimum period.