Optimal Driving Current Interval for Multiple-Receiver Inductive Power Transfer System

In the wireless charging system, the efficiency is usually affected by the load impedance, current excitation, coupling conditions, etc. In a single-transmitter multiple-receiver system, there is an optimal excitation current to maximize the efficiency under given power demands. This paper analyzes the dependence of optimal driving current on the power and coupling condition. An optimal driving current interval is found by utilizing the coupling variation range. Within this interval, the system is able to maintain a good efficiency performance under uncertain coupling. The experiment verifies the existence of the optimal efficiency point, optimal driving current, and optimal driving current interval. By assigning a fixed current in the interval, it is able to keep the system efficiency at 86.3% for a general two-RX system.