Topology Selection and Efficiency Improvement of Inductive Power Links

The problem of choosing the right topology for a wireless power transfer (WPT) application to maximize power transfer efficiency has been presented and addressed in this work. We analyze the series and parallel resonant topologies used in inductively coupled links, derive the efficiency expressions and verify them experimentally using planar inductors built on a PCB. We compare and contrast the two topologies and arrive at the frequency boundary that separates them. The results are verified experimentally and corroborated using simulation results from HFSS. We also address the misconception in the context of resonant tuning both qualitatively and quantitatively. Based on the analysis, we then provide the procedure to obtain the maximum power transfer efficiency for a given pair of coil across all frequencies, loads and topologies by proper selection of load, topology and the frequency of operation. The method is presented using an example pair of coils simulated in HFSS and the results agree well with the theoretical results.