Design methodology for inductive power transfer systems targeting high power implantable devices

Developing a resonant inductively powered system for implantable devices is difficult due to the constraints on the operating coupling range, power level, and size. It is not trivial to determine the suitable resonant topology, tuning capacitors, power transfer coils, and operating frequency. Often the system parameters, such as the operating frequency, are designed using nominal values or a trial and error approach. We present a detailed numerical model which included frequency dependent parameters to accurately model the resonant system of an inductive power system, so that unexpected characteristics that might be hidden through approximations will be revealed. A procedure based on numerical simulation in the frequency domain is proposed to determine the resonant topology and tuning capacitances for achieving maximum efficiency with a set of power transfer coils across the specified operating coupling and loading conditions. A wireless power supply has been designed using this methodology, which increased the power efficiency by 4% on average over the full operating conditions.