Magnetic Field Projection and Current Phase Control in a 2-D Planar Transmitting Coil Array

Wireless power transfer systems operating at frequencies of several megahertz are of interest due to their high spatial freedom and compactness. Combining multiple transmitting (Tx) coils for magnetic field shaping has emerged as a promising candidate to further improve the spatial freedom of the power transfer. In this article, a new closed-loop-based scheme is developed for detecting the spatial position / orientation of multiple receivers (Rxs) and controlling the magnetic field distribution accordingly. Inspired by the orthogonal projection of visible light, this article proposes the concept of magnetic field projection to detect the position and orientation of multiple Rxs. Using a 2×2 Tx-coil array as an example, a coding-based detection approach is developed using the results of the magnetic field projections in the
x
,
y
, and
z
directions. A control flow is then proposed for determining the optimal phase combination of the power amplifier (PA) output currents to achieve the desired magnetic field shaping. Finally, the above concepts are experimentally realized and verified. Light-emitting-diode arrays were specially fabricated to visualize the actual magnetic field shaping results. It is found that the final system can accomplish the closed-loop detection of the three spatially distributed Rxs and the phase control of the PA output current within 25 ms. This article is accompanied by two video files to demonstrate the actual detection and control process.