Miniature Wireless Power Transfer System for Charging Vertically Oriented Receivers

TL;DR

This paper presents a compact wireless power transfer system optimized for charging miniature, vertically oriented devices, achieving 60% efficiency at 4mm distance using a butterfly coil design.

Contribution

The study introduces a novel WPT system with a butterfly coil for vertical receivers, improving efficiency despite angular misalignment and receiver orientation.

Findings

Achieved 60% power transfer efficiency at 4 mm distance.

Demonstrated system effectiveness with vertically oriented receivers.

Analyzed the impact of misalignment and rotation on efficiency.

Abstract

Development of compact wireless power transfer (WPT) systems for charging miniature randomly oriented electronic devices is quite a challenge. Traditionally, WPT systems based on resonant magnetic coupling utilize face-to-face aligned transmitter and receiver coils providing sufficient efficiency at relatively large distances. However, with the presence of angular receiver misalignment in a such system, the mutual coupling decreases resulting in a low power transfer efficiency. Here we develop a compact WPT system for wireless charging of miniature receivers vertically oriented with respect to the transmitter. As a transmitter, we employ a butterfly coil that provides a strong tangential component of the magnetic field. Thus, a vertically oriented receiver located in the magnetic field can be charged wirelessly. We perform numerical and experimental studies of the WPT system power transfer efficiency as a function of the distance between the transmitter and the receiver. The misalignment and rotation dependencies of power transfer efficiency are also experimentally studied. We demonstrate the power transfer efficiency of 60 % within transfer distance of 4 mm for a vertically oriented receiver with an overall dimension of 20 mm X 14 mm at the frequency of 6.78 MHz.