Steady-state analysis of series/series-parallel compensated contactless resonant converter

The series/series-parallel (S/SP) compensated contactless resonant converter has a desirable feature of being insensitive to variation of parameters including the transformer's coupling coefficient. However, the error resulting from the use of fundamental harmonic approximation is significant, thus complicating the design procedure and affecting the effectiveness of the control. In this paper a steady-state analysis of the S/SP converter is presented. A generalized equivalent circuit of the S/SP resonant tank is derived, and the cause of the waveform distortion is revealed. Then, more accurate expressions for the key variables of the resonant tank and the output voltage gain are given. Finally, a 1.5 kW contactless resonant converter with S/SP compensation is constructed. Experimental results are in good agreement with the analytical results.