Coil Design and Analysis for High-Quality Thin Wireless Power Transfer Systems

To develop thinner electronic devices with wireless charging, a thin coil design is necessary. We propose a coil structure that minimizes thickness and mitigates the increase in resistance due to proximity and skin effects to achieve the high efficiency wireless power transfer (WPT) systems. The proposed coil consists of multiple thin wires created by dividing a single copper wire, with their start and end points connected. To determine an appropriate coil structure, various coil designs are compared using simulation software based on the finite element method. The proposed coil features ideal number of turns, inner diameter, copper wire width, and number of divisions optimized by a deep neural network (DNN) to achieve the highly efficient WPT systems under the specified power conditions. Simulation results show that for a coil with an outer diameter of 44 mm, copper wire thickness of 0.1 mm, coil distance of 2 mm, and frequency of 120 kHz, the proposed design improves the quality factor Q from 14.8 to 22.0, a 49% increase compared with a nondivision coil. Consequently, the power transfer efficiency increased from $\mathbf{8 5. 4 \%}$ to $\mathbf{9 0. 0 \%}$.