Optimize the Winding Structure of Flyback Transformers with Arbitrary Phase-Shifted Current Waveforms

The paper proposes a technique to calculate the ac winding loss of transformer windings with arbitrary phase-shifted current waveforms. An ac winding loss formula based on the vector form is derived, which can decouple the skin and proximity effect concisely, and is convenient to be applied for the design of the switching transformers in power adapters. Based on the technique, a guideline to optimize the transformer winding structure is introduced and applied to an active-clamp Flyback power converter. The auxiliary, cancellation and shielding windings which are commonly used in power adapters products are also taken into consideration. Simulation verifies the theory and technique.