A Single-Switch and Parameter-Insensitive Capacitive Power Transfer System for Biomedical Implants

This letter proposes a non-resonant capacitive power transfer (CPT) system for active biomedical implants (ABIs) that eliminates resonance dependency while maintaining physical isolation. By leveraging biological tissue as the dielectric medium in a four-plate coupler and drawing inspiration from Zeta converter topology, the system achieves parameter insensitivity and singleswitch control. Theoretical analysis via state-space averaging (SSA) confirms output voltage regulation solely through duty-cycle adjustment, independent of component variations. Experimental validation using 20mm×20mm plates through 4-mm pigskin demonstrates 207 mW power transfer with 30.1% efficiency at 1 MHz with a simplified receiver circuit (1 diode/1 inductor/1 capacitor). The system maintains 3.7V output under 150% load transients, 100% inductance variations, fat content change and issue bending.