Improvement of ZVS range in Dual Active Bridge Converters using nonlinear inductors by ferrite block insertion

Abstract:
The zero-voltage-switching (ZVS) range of a phase shift modulated Dual Active Bridge converter is limited to a certain power transfer at a fixed voltage input-to-output ratio. The reason is the fixed inductance of the series power transfer element. This paper discusses the advantages of nonlinear inductors as series element in Dual Active Bridge Converters. The improvement is a larger zero voltage switching range especially for non-unity voltage ratios. Nonlinear behavior in the inductor is achieved by insertion of a ferrite block into the constant air-gap of the series inductor. With a nonlinear inductor the minimum power for ZVS can be significantly reduced while achieving the same maximum power transfer.