Design of high-efficiency inductive power transfer coils for biomedical implants

This paper presents design of wirelessly powered coils for implantable micro-system for blood flow sensing, and a technique of optimal resonant load transformation. Basics and calculations are also introduced for the wireless powering structure to achieve optimal power transfer efficiency. Measurement results show that the implemented wirelessly powered coils in the implantable blood flow sensing micro-system can supply 100μW with an efficiency of 1.7%. The optimal resonant load transformation technique can improve the power transfer efficiency by 47% compared to the conventional technique, at a coil distance of 10mm.