FLYBACK BASICS
Flyback operation will be illustrated with reference to the basic circuit and the waveforms of fig. 1. It is a two step process. During the ON-time of the switch, energy is taken from the input and stored in the primary winding of the flyback transformer (actually, two coupled inductors). At the secondary side, the catch diode is reverse biased, thus the load is being supplied by the energy stored in the output bulk capacitor.