Optimized Design of Coils for Wireless Power Transfer in Implanted Medical Devices

Abstract

Implanted medical devices (IMDs) wirelessly powered by magnetic resonant coupling has attracted wide attention recently. In this study, an optimized two-coil wireless power transfer system is adopted to eliminate the requirement of an embedded battery in an IMD. In order to deliver stable power to implantable devices with wide coverage range and high efficiency, coil optimization is investigated, including the consideration of the coil structure, pitch, and number of turns. By using finite element analysis (FEA), both the transmitting and receiving coils have been optimized at 6.78 MHz. A 200 mm × 300 mm rounded rectangular transmitting coil and a novel double-layer circular receiving coil with an outer diameter of 24 mm were developed, and the transmitting coil was segmented by multiple resonant capacitors to significantly reduce the coil voltage to a safe level. Experiment results show that stable power transfer efficiency over 40% can be achieved at a distance of 5 cm with the optimized transmitting and receiving coils.