Efficiency Optimization Based Parameter Design Method for the Capacitive Power Transfer System

In this article, a parameter design method is proposed to improve the dc-dc efficiency of the capacitive power transfer (CPT) system. Similar to the inductive power transfer (IPT) system, the capacitive coupler is analyzed by using a T-type model, giving direct insight into the impedance refracted from the secondary side. Compared to the IPT system, the external capacitor of the capacitive coupler introduces extra design freedom, making it easy to realize the optimal load condition by adjusting the external capacitance. To quantify the relationship between the optimal load and the external capacitance, the impedance characteristic of the rectifier is discussed. Then, the efficiency analysis is conducted in detail. Considering the impact of the resonant frequency, and the external capacitance that determines the coupling coefficient, a parameter design method is proposed to improve the dc-dc efficiency. Although the design example is conducted with the double-sided LC compensated CPT system, the analysis and design process can be extended to other compensation networks easily. The effectiveness of the proposed design method is verified with a 100-W output CPT system. The experimental results show that the dc-dc efficiency can reach 89.39% with 10-W output, and reach 93.02% with 100-W output.