Minimizing Eddy Current Loss for Implanted Wireless Charger Through Phase Difference Optimization

Rechargeable implantable medical devices (IMDs) inherently incorporate metallic casings, which induce substantial eddy current losses (ECL) and subsequent thermal elevation during wireless charging cycles. This paper presents a phase modulation strategy to mitigate ECL by optimizing the current phase difference ϕ between TX and RX coils. Through analytical modeling of loss mechanisms, we demonstrate that increasing ϕ beyond the conventional 90° operating point significantly suppresses ECL generation. The proposed methodology is rigorously validated via simulations and experimental prototypes. Results confirm the existence of an ECL-minimizing optimal phase ϕ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</inf>, where ϕ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</inf> exhibits strong correlation with TX and RX coils diameter and current distribution.