Winding Losses in High-Current, High-Frequency Transformer Foil Windings with Leakage Layer

High-frequency, high-power transformers are becoming of increasing importance. Such transformers often use foil windings because of their superior thermal properties. Transformers in resonant converters require a specific leakage inductance. The specific leakage inductance value can be obtained by implementation of so called leakage layer. The leakage layer might not influence only the leakage inductance value but also the losses in winding foils. The influence of the leakage layer geometry on the winding losses is discussed in this paper. FEM simulations are used to analyse the influence of several leakage layer configurations and the results are compared with the performance of transformer prototypes. The investigation showed that the leakage layer spanning the whole width of the winding window gives the best results with a relatively simple shape of the layer.