A 6.78 MHz Single-Stage Wireless Power Transmitter Using a 3-Mode Zero-Voltage Switching Class-D PA

• Published in: IEEE transactions on circuits and systems. I, Regular papers Regular papers, 2021-06, Vol.68 (6), p.2736-2748
• Main Authors: Ge, Xinyuan, Cheng, Lin, Yao, Yuan, Ki, Wing-Hung
• Format: Article
• Language: English
• Subjects: Class-D; CMOS; Controllers; Maximum power; Modulation; power amplifier (PA); Power amplifiers; Power generation; Proportional integral; reconfigurable; Regulation; Regulators; single-stage; Switches; Switching; Voltage control; wireless power transfer (WPT); Wireless power transmission; Zero voltage switching; zero-voltage switching (ZVS)
• ISSN: 1549-8328; 1558-0806
• DOI: 10.1109/TCSI.2021.3071265

A 6.78 MHz single-stage transmitter (TX) using a reconfigurable regulating class-D power amplifier (PA) for wireless power transfer (WPT) applications is presented. Based on a 3-mode modulation scheme, the TX achieves power regulation and transmission with only one power stage. A discontinuous-conduction-mode (DCM) zero-voltage switching (ZVS) scheme is adopted to reduce switching loss. A control loop is set to regulate the output voltage of the WPT receiver (RX) by automatically adjusting the transmitting power. With dual-loop control and a proportional-integral (PI) compensation scheme, the loop achieves tight regulation and fast response. The controller is implemented digitally to benefit from the AirFuel ® embedded Bluetooth communication link. The PA was fabricated with a high-voltage 0.35~\mu \text{m} CMOS process, and the digital controller with a standard 0.35~\mu \text{m} CMOS process, respectively. Measurement results show that the output voltage of the RX was correctly regulated to 11.7 V under a load change of 50mA to 500mA, and the WPT system could deliver a maximum power of 7.3 W to the RX over a distance of 4.0 cm, and achieved TX to RX peak efficiency of 57.3%.