Coupling invariant inductive link for wireless power delivery to a retinal prosthesis

Inductive links are used in various applications to transfer power and data wirelessly. To achieve optimal performance in terms of voltage gain and maximum power transfer, these links are often operated at high coupling regime or under resonant frequency condition. However, these conditions may vary due to variations in the link itself or load. As a result, the link performance drops and the design of driving circuit become more complicated in order to compensate for the reduction in performance. In this work, we investigate an inductive link that has constant coupling. The tradeoff for invariant coupling is a reduction in coupling coefficient. In this study, we found that a reduction of 66 % exist between the traditional inductive link and our design. However, the advantage of coupling invariance outweighs the negative effect of large coil separation and varying conditions of a traditional one-pair coil link. The new link has the potential for powering a retinal implant.