Secondary-side de-tuning to enable wide-range Inductive Power Transfer for a wrist worn sensor

Powering body worn electronics via inductive power transfer is made more challenging by the poorly constrained relative position of the coils and the consequential wide range of magnetic coupling between them. Somewhat counter intuitively for systems that must operate with coupling factors varying over an order of magnitude it is the design of the receiver side circuits during periods of high coupling that can be most problematic. In this paper a novel low-cost, low power receiver circuit is presented that can automatically compensate for higher coupling by altering the secondary tuning. (paper)