Advancements in high power high frequency transformer design for resonant converter circuits

Medium and high frequency converters are gaining increasing interest for high power applications such as renewable energy and dc grids. Medium and high frequency transformers are an essential component in such converters. Advancing resonant converters to higher power levels challenges the transformer design in multiple aspects including power levels, switching frequency, ac and dc voltages insulation requirements and parasitic parameters. This paper presents design methods and recommendations for transformers that accomplish an industry-leading combination of power levels in the MW-class resonant frequencies up to 20kHz, operating AC voltages up to 5 kV, and dc offset voltages up to 300 kV. Design examples and test results of prototypes are presented along with results from applications where the transformers are integrated within high frequency converters.