A 40.68-MHz Active Rectifier With Hybrid Adaptive On/Off Delay-Compensation Scheme for Biomedical Implantable Devices

This paper presents an active rectifier operating at 40.68 MHz for wirelessly powered biomedical implant devices. The commonly used current-injection-based compensation and delay-based compensation schemes are analyzed. To tackle design difficulties at high frequency, a hybrid delay-compensation scheme is proposed to compensate for the turn-on and turn-off delays. The proposed scheme has a simple control logic that results in a power-efficient comparator design. A fully integrated active rectifier was fabricated in a standard 0.18- $\mu \text{m}$ CMOS process with a total area of 1.581 mm ² and a maximum output power of 56.6 mW. With the input ac voltage ranging from 2.5 to 4 V and the load resistor ranging from $200~\Omega $ to 2 $\text{k}\Omega $ , the measured peak voltage conversion ratio and peak power conversion efficiency reach 91% and 80.9%, respectively.