High Frequency High Power Integrated Transformer Design for Resonant Converters with SiC Devices

Resonant converters are used extensively for voltage regulation and isolation purposes in electric vehicles. The power level and frequency of the converters is increasing with the ongoing development of the wide-band-gap devices, which brings more challenges to the design of magnetic components. The first challenge is that such high power and frequency make it hard to make proper Litz wire. In this paper, a new current sharing method for paralleled Litz wire transformers is introduced. Using this method, the transformer can stand much higher current without increasing the cost or volume. And the power level can be further increased by integrating more matrix transformers. The second challenge is the resonant inductance integration. Different resonant inductance integration methods are summarized and compared. And controlling the leakage inductance by properly breaking the interleaving structure is proposed in this paper. Using this method, the desired leakage inductance can be reached without sacrificing too much winding loss. Comprehensive transformer design and optimization procedure is also presented in this paper. A 30 kW 100 kHz Serial Half Bridge DC-DC converter prototype is designed to verify the methods at last.