A Single-Stage Current-Mode Active Rectifier with Accurate Output-Current Regulation for IoT

摘要

This paper presents a single-stage wireless charger using a current-mode active rectifier with accurate output current regulation for efficient wireless charging. As we know, the rectifier processes an AC input voltage/current and a pulsing output current which are difficult to be accurately sensed on chip with small area and power overheads. The proposed current sensing technique uses a replica sensing stage in parallel with the main power stage. It consists of two small cross-connected sensing PMOS transistors, a small filtering capacitor, and a dynamic replica load. In addition, by adaptively tuning the delay of the power NMOS driving signal, the charging current is regulated precisely. This single-stage wireless charger operates at 6.78MHz, and is designed in a 0.35μm CMOS process. Simulation results show a minimum 97.5% current regulation accuracy over a 10× (from 100mA to 1A) output-current range. The peak efficiency of 94% is achieved with 4.2W output power.