A novel Series-Series-Parallel Resonant Converter topology with loosely coupled transformers

A new contactless power converter topology for a seriously low coupling (less than 0.15) using low-cost commercialized ferrite core transformer with high efficiency and wide air-gap (23 mm) is presented in this paper. Among the typical resonant converter topologies for contactless power transferring systems, Series-Series Resonant Converter (SSRC) and Series-Parallel Resonant Converter (SPRC) are widely used in number of power electronic applications. Because of the simple strategy and superior response irrespective of coupling factor and load changes, SSRC topology is widely applied in contactless transformer applications. However, in seriously low coupling and wide air-gap applications, the switching frequency must be increased to several MHz range in order to operate the converter at the optimized operating region. Unless some high-cost, low resistance windings are selected, due to skin effect and proximity effect, the ac conduction loss will be dangerously high when the converter is operating at the high frequency range. To solve this problem, a modified and improved topology of series-series parallel resonant converter for wide-gap (23 mm) contactless power transfer applications with the coupling rate of 0.15 is proposed.