A 13.56 MHz CMOS High-Efficiency Active Rectifier With Dynamically Controllable Comparator for Biomedical Wireless Power Transfer Systems

A 13.56-MHz active rectifier with a dynamically controllable common-gate comparator for wirelessly powered supplied implantable medical devices is presented in this paper. The proposed active rectifier is composed of two comparator-controlled PMOS and two cross-coupled NMOS for achieving high-voltage and high-power conversion efficiency. The dynamically controllable common-gate comparator is implemented for high input level and low static power consumption of the rectifier. An active self-body bias is implemented to eliminate the body effect of the power PMOS. An SR latch is adopted for the comparator to control the offset and to stabilize the output pulse. The proposed rectifier is fabricated in a standard 0.13-mu m (3.3-V device) CMOS process with 0.102-mm(2) active area. The measured input and output ranges under 500-Omega output load are 2.14-3.6 V and 2-3.46 V, respectively. The measured power conversion efficiencies versus output load (0.1-1 k Omega) under 3.6 V ac input are 88%-91.9%, and the voltage conversion efficiencies are 86%-96.4%.