Double Sided Conduction in N:1 Transformers

In the high-frequency regime (HF, 3-30 MHz), the proximity effect in transformers can lead to large losses due to undesired current crowding and circulation. Litz wire's efficacy does not scale well past a few and interleaving solid conductors leaves much conduction area underutilized. Field-shaping techniques have recently been proposed to achieve double-sided conduction, resulting in twice as much conduction area in interleaved solid-conductor layers compared to normal interleaving. While double-sided conduction has been demonstrated in 1:1 transformers, we explore in this paper the application of the double sided conduction design methodology to non-unity turns ratio transformers. We validate our conclusions with a 4:1 double sided conduction foil-wound transformer optimized for operation at 13.56 MHz, and compare it to a standard-interleaved foil-wound transformer, a magnet wire-wound transformer and a litz-wound transformer. We find that it is possible to achieve double sided conduction in non-unity turns ratio transformers and that they can achieve better performance than standard interleaving, magnet wire and litz wire in the MHz regime.