Flyback Transformer
Flyback converters are a popular topology for power supplies <150W due to their simplistic design, versatility and low cost. Flyback converters have similar architecture and performance as the boost topology but have the benefits of a secondary winding. The secondary winding can provide galvanic isolation from the input to the output and can step up or step down the input voltage depending on the turns ratio. Flyback transformers can also have multiple secondary windings so multiple outputs can be regulated from a single source. Moreover, since the energy is stored in the transformer, no output filter is required as in other isolated topologies, so the number of components used can be reduced lowering the cost of the design. Flyback transformers differ from other transformers since they store energy in the magnetic field rather than being transferred immediately from the input to the output. The energy is stored in the primary when the switch is closed (Fig. 2) then released to the secondary when the switch is opened (Fig. 3). Since flyback transformers can typically operate in the hundreds of kHz range, a low loss ferrite material is used and gapped to store the energy and prevent saturation.
