A Single-Stage Delay-Tuned Active Rectifier for Constant-Current Constant-Voltage Wireless Charging

Abstract

This paper presents a single-stage regulated active rectifier with two operation modes of constant-current charging mode (CC) and constant-voltage charging mode (CV) for battery wireless charging. With the delay-tuned active rectifier, the proposed wireless charger can realize AC-DC power rectification, voltage regulation, CC and CV battery charging in a single power stage with high efficiency and small volume. The adaptive tuning of the delay of the power NMOS gate-drive signals, regulates the average charging current at a constant value for the CC mode, and the output voltage for the CV mode. The circuit achieves a precise average AC current sensing with a replica sensing stage. The utilization of a hysteresis comparator detects the output voltage and changes the charging mode during the battery charging process. The proposed single-stage wireless charger, designed in standard 0.35μm CMOS, operates at 6.78MHz. Simulation results show that the efficiency of the entire CC mode is higher than 89.8% with the battery voltage ranging from 2.8V to 4.2V. And we obtain a peak efficiency of 94.3% with 4.2 V and 1A output.