A 6.78MHz mid-range wireless power charging system for milliwatt-power-level long-term vital monitoring applications

Abstract

This paper presents a methodology and system architecture to supply power over mid-distance, in the context of bio-sensors for long-term vital monitoring purposes. The first part of the paper introduces a novel non-coupling coil array system with a beamforming-control algorithm to enhance the power transfer efficiency, up to 25cm distance, regardless of the receiver’s position. In the second part an on-chip wireless power charger system with high efficiency and trimming function to charge the mAh-level NiMH battery and provide stabilized power supply to devices, is presented. Overall, the system achieves 0.74% power efficiency at a distance of up to 25cm (with 0.86% from the beamforming-control power transfer system and 86% from the wireless power charger system).