Design of Efficient Resonant Coupling Wireless Charging Systems by Adjustable Couplings

Abstract

In this thesis resonant coupling coils are applied to design wireless charging systems for implantable cardiac pacemakers The coils are implemented based on helical-type structures and the electrical characteristics of helical coil are investigated based on its physical parameters The 4-coil systems are designed according to the practical specifications of cardiac pacemaker for wireless power transmission The reflected load theory is applied to analyze the equivalent circuit of multi-coil system Based on this theory an optimization design method and procedure are proposed by adjusting couplings to achieve optimal power transmission efficiency This method is verified and the measured power transmission efficiency is improved by 5% to 50% and approximately 85 % of power transmission efficiency can be achieved in the purposed 4-coil system from 2 0 cm to 5 0 cm of the operating distance Furthermore the purposed 4-coil system is integrated into a wireless charging transfer system including the front-end power amplifier in the power source transmitter and a rectifier and a regulator in the back-end power pick-up receiver From the power source 31 8 dBm output power and the 73 % of power-added efficiency (PAE) are achieved for the implemented class-E power amplifier The output power is delivered wirelessly by the purposed 4-coil system After being received by back-end circuit the wireless power is converted by a bridge rectifier and then stepped down by a buck regulator to charge the lithium battery (HTC-T5555) By integrating the power amplifier with the 4-coil system maximally 62 07 % (averagely 51 56 %) of receiving efficiency from the source to the output of the receiving coil is achieved for different operating distances of device from 2 0 cm to 5 0 cm The system is verified for battery charging and it takes 150 minutes to restore the lithium battery from 3 % to 87 % battery capacity

Date of Award	2014 Aug 1
Original language	English
Supervisor	Chin-Lung Yang (Supervisor)