Impact of source internal resistance on efficiency of four resonant wireless power transfer topologies

According to the connections of the inductor and the capacitor on both primary and secondary sides, there are four types of topologies in resonant wireless power transfer, namely series-series, series-parallel, parallel-series, and parallel-parallel. Based on the circuit theory, the mathematical models of the four topologies are built. While the same transfer efficiency can be obtained from these four topologies, the system efficiency, which takes the source internal resistance loss into consideration, is different. The system efficiency of primarily parallel connection is proved to be higher than that of primarily series connection. The theoretical calculations and the experimental results confirm the conclusions.