A Smart Health Tracking Ring Powered by Wireless Power Transfer

This paper presents a novel wireless power transfer design to seamlessly power a smart health tracking ring using a smartphone. The reverse wireless charging feature of smartphones allows them to transmit sufficient energy to charge the smart ring when users hold the smartphones in their hands without impacting the user. The tested system includes a transmitter generating 170.07 kHz signals from a 5 V DC supply and a receiver circuit that captures the magnetic signal and converts it into a DC output to charge a 3.7 V battery and power a heart rate sensing monitor. The experimental results demonstrate that the smart ring can receive a maximum power of 102.4 mW from a 5 V DC smartphone power supply. The maximum measured efficiency of the wireless power transfer system from the transmitting power amplifier input to the DC output of a full-bridge rectifier is 13.39%. If the smartphone is held at least 1.52 hours a day, the ring will receive sufficient power to continuously track the user's heart rate in a 24-hour period.