Optimisation of Magnetic Loss Trade-offs in High-Frequency Litz Wire Transformers

Magnetic design poses numerous challenges, such as oversized components and excessive losses. Based on validated magnetic loss models, this paper presents an extensive analysis of the trade-offs in high-frequency transformer designs. Specifically, the trade-offs between core losses and winding losses are demonstrated in both analytical models and based on experimental data. From the validated loss models, this paper presents a practical and fast magnetic design method for high-frequency transformers in isolated DC-DC converters. The methodology enables a flexible design of litz wire windings and planar transformers based on an exhaustive search that identifies the Pareto optimal combinations of design parameters. Different core materials, shapes, sizes, and winding types can be considered, whereby four Pareto optimal planar transformers of different sizes are constructed. Finally, an optimised transformer is implemented in a 600 W dual active bridge converter operating at 460 V, with thermal images and waveforms indicating its operation.