Field-cannon-technique to Reduce AC Resistance of Foil Windings in High Frequency Transformers

Minimizing transformer winding loss is a prominent factor to increase efficiency of power electronics converters. This is especially valid for modern switched-mode power supplies, where eddy current effects on windings become dominant due to continuously elevated switching frequency. In this paper, a field shaping technique, dubbed the field-cannon-technique, is proposed to mitigate eddy current effects in high frequency transformers' foil windings. The basic principle and the implementation of the proposed technique is introduced. A model is derived using finite difference method, in order to calculate the distribution of the magnetic field within the transformers implemented with the field-cannon-technique. Finally, the technique is verified by experiments, where the winding resistance of the transformer is reduced by a factor of three.