Comparison of CMOS rectifiers for micropower energy harvesters

This paper presents a comparison of standard topologies for AC-DC converters within micropower energy harvesting systems. The focus is on low input voltage (<; 1 V), low input frequency (<; a few kilohertz), ultra-low power consumption (nanowatts to microwatts), and fully integrated inductor-less cold start topologies. These standard topologies are compared in terms of PCE (power conversion efficiency), VCR (voltage conversion ratio), average output voltage, size and minimum input voltage based on simulation of the topologies using TSMC 0.18 μm MOSFETs. Reconstructed standard full-wave rectifiers were compared with input voltage of 1 V amplitude at 1 kHz and 100 kO load resistor. The bootstrapped and fully cross-coupled topologies provided PCE values exceeding 80% with minimum input voltage of 300 mV and ~20mV respectively. The fully cross-coupled topology provided maximum VCR of ~40% at 1 V input that reduces to ~15% at 0.5 V input. This paper concludes with an overview of the design factors and tradeoffs involved in the selection of such AC-DC converters.