A Self-Tuning Inductive Powering System for Biomedical Implants

Abstract

This paper describes the design and implementation of a self-tuning inductive powering system conceived for biomedical applications. The circuit operates at 1 MHz and delivers 380 mW to the implant with an efficiency of 50%, at a distance of 1 cm. Absorption modulation is used to monitor the circuit parameters allowing the system to deal with distance increases up to 5 cm as well as small coil misalignments. The automatic-tuning system adjusts the configuration of the coil driver depending on the self-monitored coupling, acting on a bank of switchable capacitors with a pattern defined by the received data. It is demonstrated that the implemented tuning strategy boosts the transmitted power by a factor two. In addition, the combination of tuning and smart power regulation was proven to sensibly increase the system efficiency by maintaining a constant energy level at the secondary.