A new Approach of Resonant Converter using Large Air Gap Transformer

A major topic of resonant converter is the need of additional resonant tank components. The use of stray inductance of a conventional transformer for this purpose is very limited. For high power and high frequency applications these additional components are challenging and have low acceptance due to its additional costs. For a high efficiency and to cover the whole operating area a well-considered design with respect to ZVS capability from zero to full load range is essential. In this paper, a new Large Air Gap Transformer is proposed which includes all inductive resonant tank elements for series-parallel resonant converter and the transformer in a single component. This simple design is very easy to handle but still operates in the full operating area and high efficiency. A reduction about 80% of ferrite material is achieved by using this new Large Air Gap Transformer. A field simulation to exclude possible electromagnetic interactions with the environment has been carried out. The new approach is demonstrated with LLC converter based on SiC with 10 kW output power and 200 kHz switching frequency.