A Dynamic Solution to Spatial Misalignment in Strongly Coupled Magnetic Resonance Wireless Power Transfer Systems

Spatial misalignment is the leading cause of power transfer efficiency loss in a wireless power system; the misalignment causes the magnetic coupling of the system to change, resulting in a non-optimal load impedance. This research work presents the design and evaluation of an adaptive, near-field transmitter that can maintain the system efficiency when spatial misalignment occurs. The design consists of a power amplifier, a directional coupler, a tuneable impedance matching network, a gain-phase detector, and a microcontroller. An algorithm was created to determine the varying load impedance; another modified the configuration of the tuneable matching network for one that can match to the new load impedance. The developed class EF2 power amplifier delivered 7.5 W of power to the load, with a drain efficiency of 82.4%, at 13.56 MHz. The adaptive transmitter prototype maintained an average of 55% system efficiency for a separation distance of 1.5 cm to 3 cm.