Computer-Aided Design and Optimization of an Integrated Transformer with Distributed Air Gap and Leakage Path for an LLC Resonant Converter

Integrating all magnetic elements of an LLC resonant converter into the transformer is not yet fully applied in industry products.. This is due to the fact that conventional integrated transformers often suffer from high winding losses caused by the significant proximity effect. This paper addresses this problem by proposing a combination of a distributed air gap and a leakage path within the transformer. A computer-aided design routine is presented in this paper which allows to find a loss-optimal design. The proposed routine is used to design an integrated transformer of 8 kW operated at 300 kHz which was realized as a lab prototype. Compared to a conventional integrated transformer the total losses were reduced by 30%.