Dual-Band Free-Positioning Transmitting Coil for Multiple-Receiver Wireless Power Transfer

In recent years, the requirement for a compact wireless power transfer (WPT) system that can supply power to multiple devices in various practical usage scenarios has been attracted many researchers. The receiver (Rx) misalignment problem is contributory to the power transfer efficiency (PTE) degradation. Moreover, in a multiple-output WPT system, the overall system efficiency is also affected by cross-coupling between receivers. This paper proposes a dual-band free-positioning transmitting coil (FPDB-Tx) for multiple-receiver WPT. A three-dimensional Tx structure is modeled by investigating the current direction on each coil loop to adapt the Rx angular and axial misalignment. The Tx configuration is designed following a wireless charging box concept, where multiple Rx devices can receive energy freely without a null efficiency point. The mutual inductance is examined by a mathematical method in various Rx orientations to verify the free-positioning characteristic. Furthermore, an equivalent circuit model of the WPT system is theoretically analyzed to obtain dual operating frequency bands and then maximized the PTE. The experimental results show that the proposed WPT system achieves a stable PTE in various Rx positions. Especially, the WPT system has a maximum PTE of 97.27% and 91% at 6.78 MHz and 13.56MHz, respectively.

Automated summary

This paper proposes a dual-band free-positioning transmitting coil (FPDB-Tx) for multiple-receiver WPT, which adapts to Rx misalignment by examining current direction and is designed with no null efficiency point.