Characteristics and Design of Transformer in Loosely Coupled Inductive Power Transfer System

The transformer in loosely coupled inductive power transfer system is quite different from traditional closely coupled transformer, and its characteristics are very critical to system performance. In this paper, the factors that influence loosely coupled transformer characteristics are first discussed, including coil position, air gap, and magnetic core position shift. Then their influences are detailed by means of ANSYS simulation. Thus the characteristics of the transformer are proposed. Further, some design considerations about loosely coupled transformer are obtained. Finally, a prototype of full-bridge series resonant converter with a 4mm and 10mm air gap loosely coupled transformer are built, and experimental results verify the correctness of the analysis and design.