Multilevel Switched-Capacitor AC-DC Step-Down Rectifier for Wireless Charging With Reduced Conduction Loss and Harmonic Content

In this article, a wireless charging architecture employing a multilevel switched-capacitor (MSC) ac-dc rectifier is investigated. The proposed MSC rectifier features a multilevel design that is scalable to accommodate different power ratings and load ranges. The topology showcases advantages for wireless power transfer (WPT) systems in terms of compactness, efficiency, impedance tunability, and harmonic attenuation. The single-stage active topology is capable of varying its low-distortion staircase input voltage to tune the WPT system for high system-wide efficiency. A seven-level, 20-W prototype is used to verify the WPT loading and loss analysis. The prototype operates at 150 kHz with up to 3:1 step-down conversion ratio to an output voltage of 5.0 V. The experimental peak dc-to-dc efficiency is 93.8% and the rectifier peak efficiency is 98.3%. The rectifier demonstrates low waveform distortion and high efficiency across many WPT loading conditions, solidifying its place as a strong candidate for wireless power applications.