Three-Mode MHz Wireless Power Transfer: Inductive, Capacitive, and Hybrid, With a Unified Coupling Architecture

This paper aims to investigate the deeper wireless power transfer (WPT) mechanism and possibility in the megahertz range: a WPT system with the capability of mode switching among inductive, capacitive, and hybrid power transfer (IPT, CPT, and HPT) with a unified coupling architecture. The proposed transmitter (T×) and/or receiver (R×) consists of a pair of separate concentric planar spiral coils printed on the polytetrafluoroethylene (PTFE) circuit board, and coupling capacitances are formed when T× and R× are aligned, providing a path for CPT. In the meantime, the mutual inductance between the T× and R× coils provides the channel for IPT. The externally used capacitors connecting the concentric coil pairs of T× and R× determine the coupler’s working modes: IPT, CPT, and HPT. Detailed theoretical analysis and system design are provided, and 600W IPT, 400W CPT, and 400W HPT systems are implemented based on the proposed coupler structure with a diameter of 310mm. Experiments demonstrate the long-distance power transfer capability in IPT mode (70mm~100mm) and good misalignment tolerance with a fixed frequency of 1.034MHz. In comparison, the CPT and HPT modes are more suitable for short distances (10mm~20mm) and aligned conditions with frequencies ranging from 2.27MHz to 4.166MHz. With distances of 70mm, 10mm, and 10mm, IPT, CPT, and HPT modes achieve peak DC-DC efficiencies of 93.2%, 90.4%, and 92.6% with power of 585W, 403W, and 391W, respectively.