Recently, research teams led by Professor CHENG Lin from University of Science and Technology of China (USTC) and Professor KI Wing Hung from The Hong Kong University of Science and Technology (HKUST) presented a novel wireless charger for resonant wireless power transfer applications. The results were published in IEEE Journal of Solid-State Circuits (JSSC).

Wireless charging provides a convenient and reliable way to charge batteries of electronic devices. However, unlike a wired charger that has a steady input voltage, the alternating current input voltage of a wireless charger needs to be rectified and regulated first. Due to multistage power processing, the efficiency is much degraded. This puts a stringent limit on the charging current to avoid heating up the device.

Based on the principle of three-mode reconfigurable resonant regulating (R3) rectifier, the research teams proposed a charger that realizes power rectification, voltage regulation, and constant-current constant-voltage (CC-CV) charging in a single power stage, thus achieved high efficiency and low cost. A bootstrapping technique using a single-input-dual-output voltage doubler with adaptive phase control is also proposed to integrate bootstrap capacitors on-chip.

Block diagram of the proposed single-stage wireless charger

The charger was fabricated in a standard 0.35-μm CMOS process and the measured peak efficiency reached 92.3% and 91.4% when the charging currents were 1 A and 1.5 A, respectively. This verified the effectiveness of the proposed techniques. It achieved the highest efficiency and the highest level of integration when compared with state-of-the-art designs, making it a promising approach in designing wireless chargers.

Chip micrograph of the proposed charger 

JSSC is a distinguished journal in the area of integrated circuits design. This is the first time that a scientist from USTC published an article on it as the first author. 

Paper link:

https://ieeexplore.ieee.org/abstract/document/8959424

(Written by YANG Ziyi, edited by YE Zhenzhen, USTC News Center)