A Multicriteria Constrained Tuning Method With Critical ZVS Operation for 6.78 MHz WPTS

In general, the tuning of inductor–capacitor–capacitor-series (LCC-S) networks aims to obtain the load-independent output. However, the LCC-S networks require appropriate detuning to provide sufficient high-order harmonics for full-bridge inverters to achieve the critical zero-voltage switching (ZVS) operation at MHz scenario. Moreover, the effect of the parasitic resistance of the auxiliary inductor on the output characteristic and efficiency of LCC-S networks becomes more prominent as the switching frequency increases, introducing a new challenge to the parameter design. In this article, a multicriteria constrained tuning method with critical ZVS operation is proposed for LCC-S type full-bridge 6.78-MHz wireless power transfer systems (WPTS). Based on the time and frequency analysis, the proposed method obtains the ZVS regions over the whole load range. Furthermore, the system achieves the optimal efficiency under the target case with the critical ZVS operation. A 65-W full-bridge 6.78-MHz WPTS is built to verify the accuracy and coherence of the proposed tuning method. The system can achieve an efficiency of 88.51% and 88.29% with an output power of 77.14 W and 62.52 W, respectively. Compared with the control parameters, the power loss of the proposed parameter over the whole load range has been reduced by 15.7%.