A 6.78 MHz Wireless Power Transfer System for Simultaneous Charging of Multiple Receivers with Maximum Efficiency using Adaptive Magnetic Field Distributor IC

Abstract

We developed a 6.78 MHz wireless power transfer (WPT) system for simultaneous charging of multiple receiver (RX) coils. On the basis of the transmitter (TX)-RX and RX-RX coupling distinguished by the adaptive magnetic field distributor (AMFD) IC, the distribution of magnetic fields from the TX coils was optimized at each RX coil for the maximum efficiency. A 2-TX 2-RX WPT system was implemented with the AMFD ICs fabricated in 1.8 V, 180 nm CMOS process. Compared with the conventional method, the system efficiency is increased from 8.9 % to 61 % with the load power of 173 mW.