| Abstract |
Energy-storage transformers, such as transformers for flyback or LLC converters, have different design constraints than typical transformers. Since primary and secondary currents are not in phase, interleaving does not necessarily reduce high-frequency losses. Such transformers often must be designed with low leakage as well. In this work, we propose design guidelines for a transformer structure that uses field shaping to achieve current conduction along most of the skin of the conductors (double-sided conduction), equal current sharing between paralleled turns, even for out-of-phase currents, and near zero MMF drop across the leakage reluctance paths. The transformer therefore has low leakage inductance and low conduction loss without the use of litz wire and can be used effectively at frequencies beyond a few megahertz. Step-by-step design guidelines are proposed and a prototype transformer is built which achieves a leakage to magnetizing ratio of 1.12\%, a power loss 14-17\% of a traditional lumped-gap transformer, and current sharing variation less than 1.5\% between paralleled turns. |
