A Wireless Charging System Applying Phase-Shift and Amplitude Control to Maximize Efficiency and Extractable Power

TLDR

Wireless power transfer is a growing technology with many potential applications, yet its widespread adoption is limited by the low efficiency of current systems. This study proposes a concept to maximize efficiency and increase extractable power in a nonresonant wireless power transfer system. The approach actively adjusts the secondary‑side load impedance by controlling the phase shift of an active rectifier and its output voltage, and is implemented in a prototype that includes a dc‑dc converter to charge a battery. Experimental results show that the optimization method significantly outperforms existing solutions in both efficiency and extractable power.

Abstract

Wireless power transfer (WPT) is an emerging technology with an increasing number of potential applications to transfer power from a transmitter to a mobile receiver over a relatively large air gap. However, its widespread application is hampered due to the relatively low efficiency of current Wireless power transfer (WPT) systems. This study presents a concept to maximize the efficiency as well as to increase the amount of extractable power of a WPT system operating in nonresonant operation. The proposed method is based on actively modifying the equivalent secondary-side load impedance by controlling the phase-shift of the active rectifier and its output voltage level. The presented hardware prototype represents a complete wireless charging system, including a dc-dc converter which is used to charge a battery at the output of the system. Experimental results are shown for the proposed concept in comparison to a conventional synchronous rectification approach. The presented optimization method clearly outperforms state-of-the-art solutions in terms of efficiency and extractable power.