Compact Distance-Adaptive Wireless Power Transfer Using a Reconfigurable Auxiliary Coil

In this letter, we propose a distance-adaptive wireless power transfer (WPT) system using a reconfigurable transmitter. The proposed transmitter incorporates a main coil and an auxiliary coil with adjustable currents. The auxiliary coil can be configured to directly control the coupling strength, which can mitigate excessive or insufficient coupling caused by distance variations. The distance adaptation capability of the proposed WPT system is verified through both simulations and experiments. Measurements of transmission coefficients show maximum increase of 64% at close range (15 mm) and 57% at long range (110 mm). The overall effective transmission range has been improved by 59%. The proposed design offers a simple yet effective approach to distance adaptation while maintaining compact system dimensions.