A delay time controlled active rectifier with 95.3% peak efficiency for wireless power transmission systems

Active rectifier with comparators (CMPs) is often used in wireless power transmission (WPT) systems. However, it suffers from low power conversion efficiency (PCE) in light load condition and multiple pulse problem (MPP) due to the CMPs with delay compensation. In this paper, a novel active rectifier with delay time controller is proposed to solve both issues. A current control delay line (CCDL) is introduced to adjust the rising and the falling edges of the gate voltages of the NMOS (Fgns), controlled by a negative feedback loop consisting of a switched-capacitor (SC) sample module and a supply independent bias current controller (IB controller). The proposed rectifier is designed with a standard 0.18μm CMOS process. Post-layout simulation results show that the delay time controller consumes only 34μA, which is much smaller than the power consumptions induced by controller with CMPs, thus significantly enhancing the PCE of the rectifier. The PCE of the rectifier is higher than 88% in the whole load range from 629μA to 32.1mA, and exceeds 92% when load resistance Rl varies from 100Ω to 1200Ω. A peak PCE of 95.3% is achieved when Rl is 200Ω and Vac is 2V.