Switching control circuit and switching power supply

Abstract

This enables stable output voltage control when the load current decreases in a flyback type power supply. [Solution] The switching control circuit 1 of the embodiment controls the on / off state of a transistor Q that switches the energized state of the primary winding L1 of a transformer T constituting a switching power supply device 100 by outputting a PWM signal SP based on the flyback voltage VFB generated in the primary winding L1. The switching control circuit 1 includes a detection circuit 2 that generates a load state signal CF at a level corresponding to the generation state of the flyback voltage VFB at a judgment criterion time set according to the transition of transistor Q to the off state, and a signal generation circuit 3 that generates a PWM signal SP and switches the period of the PWM signal SP according to the load state signal CF.

Images