Here’s’ a video tutorial from Linear Technology describing how to design a simple flyback DC/DC converter. The video promotes the use of LT’s LT3573 IC, but it also provides information that could be applied to other designs as well.
Isolated power supplies are needed in a wide variety of applications. Galvanic isolation is achieved by isolating two or more circuits using a transformer or optocoupler, and is desirable for many reasons: safety, noise immunity, circuit protection, etc. Traditionally, isolated power supplies use an optocoupler to transfer regulation information across the isolation barrier.