Simultaneous Wireless Power Transfer via Magnetic Resonant Coupling to Multiple Receiving Coils

Abstract

An optimal design for a simultaneous wireless power transfer system is difficult to achieve, as the effect of multiple coils on the total efficiency is unclear. The power loss increases with the number of coils when they are arranged in a straight line. On the other hand, simultaneous wireless power transfer to multiple receiving coils surrounded by a large transmitting coil has not been studied. In this paper, the simultaneous wireless power transfer system is represented by an equivalent circuit, and a detailed study of the total efficiency and optimal load is carried out. The number of coils is increased, and an analysis is performed for both the equal coupling coefficient case and the unequal coupling coefficient case. From the theoretical analysis and experimental results, the total efficiency improves when more coils are added. Nevertheless, the final efficiency is bounded by the internal resistance and the load values at the receiving coils. The proposed equivalent circuit model also demonstrates that the maximum efficiency is achievable by using the optimal resistance for wireless power transfer containing a specific number of coils.