Analytical Model and Robust Design of PT-Symmetric CLLC Coreless Transformers With Non-Ideal Parameters

In this article, an analytical model and robust design of parity-time (PT) symmetric CLLC coreless transformers (CLTs) with non-ideal parameters is proposed. Unlike the conventional design with ideal and equal resonant frequencies of the primary and secondary sides, a non-ideal design of resonance parameters is employed to avoid the unsteady frequency jump in the ideal PT-symmetric CLT. More critically, the non-ideal parameters and the effects of power loss on the voltage gain are analyzed and compensated to obtain the weak load-dependent voltage gain characteristic. First, the exact analytical model for the non-ideal PT-symmetric CLT is developed utilizing the Cardano formula. The results show that the frequency characteristics of multiple solutions can be significantly modified when the secondary resonant frequency is lower than the primary side. It has a narrower range and slower frequency change than the ideal design. Second, a non-ideal design methodology is given, considering frequency reliability and robust output voltage. Finally, a 600W experimental prototype is built for verification and comparison. The conversion efficiency of the non-ideal design is similar to the ideal design, and higher than the conventional leakage resonant CLT because of the lower turn-off current, circulating current, and switching frequency.