Hysteresis-Dependent Synchronized Load Shift Keying and Reconfigurable Class-D Power Amplifier-Based Fully Integrated Adaptive Control in Wireless Power Transfer System

A 13.56-MHz wireless power transfer (WPT) system with fully integrated transmitter (T-X) and receiver (R-X) chips is presented. The receiver's output voltage is locally regulated using a linear current-sink-based regulator, while global power regulation is achieved at the transmitter through a hybrid control strategy that combines constant off-time and hysteretic control for a reconfigurable power amplifier. Synchronized load-shift keying at the receiver improves the relative change in the primary current of the transmitter by >15%. The adaptive digitally controlled active rectifier achieves a voltage conversion ratio (VCR) and power conversion efficiency (PCE) of 0.92 and 92.4%, respectively, for a 200 Omega load resistance. The end-to-end efficiency is improved by 25% at heavy load and 14% at light load by enabling T-X global power regulation. Both T-X and R-X chips were fabricated in the BCDlite 180 nm process with 1.8 V/5 V devices. This system achieves a greater operating distance, higher output power, and faster load-transient response while significantly reducing circuit and system design complexity.