22.7 An inductively-coupled wireless power-transfer system that is immune to distance and load variations

Biomedical implants are often powered by an external source via an inductively-coupled wireless power link. During actual use the distance between the external and implant coils may change, their axes may misalign, and the load current may change significantly in implants that alternate between monitoring and stimulation. Ideally the wireless power link should deliver a stable voltage to the implant across reasonable ranges of these variations, thereby eliminating a lossy voltage limiter and alignment magnets. We present the analysis and design of a new link architecture to meet all these objectives. It stands apart from similar work in that this link self-regulates against all variations, with no need for a reverse channel.