A 27 W Wireless Power Transceiver With Compact Single-Stage Regulated Class-E Architecture and Adaptive ZVS Control

Abstract

This work presents a reconfigurable single-stage regulated Class-E (SSRE) wireless power transceiver that deliv- ers 27 W for wireless charging at 6.78 MHz. The power stage of the transmitter merges a buck and a Class-E power amplifier (PA) into one conversion stage, saving one inductor and one capacitor with improved system efficiency. Instead of using a bulky external impedance tuning block to ensure a 50% duty cycle operating point, the proposed Class-E zero-voltage switching (ZVS) controller allows the Class-E stage to work at an adaptive duty cycle without an off-chip tuning circuit. The high voltage and high current stress of the Class-E stage is handled by a GaN transistor, the driver of which uses an NMOS transistor for the high-side switch that realizes a rising edge of 2.8 ns with no overshoot. For directly sensing high voltage without using a resistor divider, an HV-NMOS shielded push-pull comparator is designed. An adaptive dead time control based on a sample-and- hold (S/H) feedback loop is proposed to reduce reverse conduction and recovery loss of the buck stage. The proposed solution demonstrates good trade-off among power level, efficiency, and power density. The SSRE WPT system delivers a maximum dc output power of 27 W with an end-to-end (E2E) efficiency of 63.0% if the receiver uses a traditional passive rectifier. The peak E2E efficiency of 80.0% is achieved at dc output power of 9.5 W; furthermore, in a two-chip differential transmitter configuration, the