A Near-Optimum 13.56 MHz CMOS Active Rectifier with Circuit-Delay Real-Time Calibrations for High-Current Biomedical Implants

In this paper, a near-optimum active rectifier is proposed to achieve well-optimized power conversion efficiency (PCE) and voltage conversion ratio (VCR) under various process, voltage, temperature (PVT) and loading conditions. The near-optimum operation includes: eliminated reverse current loss and maximized conduction time achieved by the proposed sampling-based real-time calibrations with automatic circuit-delay compensation for both on- and off-time of active diodes considering PVT variations; and power stage optimizations with adaptive sizing over a wide loading range. The design is fabricated in TSMC 65 nm process with standard I/O devices. Measurement results show more than 36% and 17% improvement in PCE and VCR, respectively, by the proposed techniques. A peak PCE of 94.8% with an 80Ω loading, a peak VCR of 98.7% with 1 kΩ loading, and a maximum output power of 248.1 mW are achieved with 2.5 V input amplitude.