A 6.78MHz Regulating Rectifier With Constant On-Time Control for High Resolution and Ultra-Fast Transient Response

This paper presents a novel constant on-time (COT) single-stage reconfigurable regulating rectifier for wireless power transfer system. Compared with the discrete multi-cycle pulsewidth modulation technique adopting in the prior-art regulating rectifiers, the proposed rectifier achieves high regulating resolution by adjusting the duty ratio continuously and smoothly. In addition, the load-transient response is much faster with the COT control method. In order to optimize the output voltage ripples, the regulating cycle is designed to be small via minimizing the on-time. This single-stage wireless power receiver is designed in a 0.18$\mu$m BCD process, and regulates an output voltage of 5V. Simulation results show that the maximum output power is 850mW with a peak efficiency of 93.2% and a minimum regulating cycle of 0.12$\mu$s. For a load switching between 50mA and 170mA, the response of the proposed rectifier is instant with the unnoticeable overshoot and undershoot.