An Adaptive Impedance Matching Network with Closed Loop Control Algorithm for Inductive Wireless Power Transfer.

Zhidong Miao,Chen Gong,Dake Liu

doi:10.3390/s17081759

Abstract

For an inductive wireless power transfer (IWPT) system, maintaining a reasonable power transfer efficiency and a stable output power are two most challenging design issues, especially when coil distance varies. To solve these issues, this paper presents a novel adaptive impedance matching network (IMN) for IWPT system. In our adaptive IMN IWPT system, the IMN is automatically reconfigured to keep matching with the coils and to adjust the output power adapting to coil distance variation. A closed loop control algorithm is used to change the capacitors continually, which can compensate mismatches and adjust output power simultaneously. The proposed adaptive IMN IWPT system is working at 125 kHz for 2 W power delivered to load. Comparing with the series resonant IWPT system and fixed IMN IWPT system, the power transfer efficiency of our system increases up to 31.79% and 60% when the coupling coefficient varies in a large range from 0.05 to 0.8 for 2 W output power.

Highlights

inductive wireless power transfer (IWPT) technology can provide power without physical connections
Comparing with the series resonant IWPT system and fixed impedance matching network (IMN) IWPT system, the power transfer efficiency of our system increases up to 31.79% and 60%
We focus on providing an adaptive IMN IWPT system covering region A and B

Summary

Introduction

IWPT technology can provide power without physical connections. Due to this unique feature, IWPT technology has attracted much attention in applications such as battery charging, portable devices, RFID, and medical devices [1,2,3,4,5]. In order to obtain a high efficiency, many optimization efforts have been made by researchers on every step of transferring and coupling, such as the power amplifier [6,7], the coupling coil geometry [4,8,9], the load [10], and the impedance matching networks [11,12,13,14,15,16]. Most of these researches are discussed under fixed relative position of the coils, which means that the coupling is fixed. In most applications, the distance is varied which leads to two problems: one is the efficiency degradation, another is the load power variation on load side

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