Reconfigurable Resonant Regulating Rectifier With Primary Equalization for Extended Coupling- and Loading-Range in Bio-Implant Wireless Power Transfer

Wireless power transfer using reconfigurable resonant regulating ( ${\rm R}^{3}$ ) rectification suffers from limited range in accommodating varying coupling and loading conditions. A primary-assisted regulation principle is proposed to mitigate these limitations, of which the amplitude of the rectifier input voltage on the secondary side is regulated by accordingly adjusting the voltage amplitude ${\rm V}_{\rm eq}$ on the primary side. A novel current-sensing method and calibration scheme track ${\rm V}_{\rm eq}$ on the primary side. A ramp generator simultaneously provides three clock signals for different modules. Both the primary equalizer and the ${\rm R}^{3}$ rectifier are implemented as custom integrated circuits fabricated in a 0.35 $\mu{\rm m}$ CMOS process, with the global control implemented in FPGA. Measurements show that with the primary equalizer, the workable coupling and loading ranges are extended by 250% at 120 mW load and 300% at 1.2 cm coil distance compared to the same system without the primary equalizer. A maximum rectifier efficiency of 92.5% and a total system efficiency of 62.4% are demonstrated.