A 0.65-mW-to-1-W Photovoltaic Energy Harvester With Irradiance-Aware Auto-Configurable Hybrid MPPT Achieving >95% MPPT Efficiency and 2.9-ms FOCV Transient Time

Abstract

This article presents an integrated photovoltaic (PV) energy harvester for mobile applications. In the energy harvester, an irradiance-aware hybrid algorithm (IAHA) is developed to automatically select appropriate maximum power point tracking (MPPT) scheme and control methodology under different irradi- ance levels in order to provide high tracking efficiency and power efficiency across wide power ranges. A slew-rate-enhanced (SRE) fractional open-cell voltage (FOCV) method is also proposed to shorten the transient time for MPPT in light loads, thereby increasing energy capture from the solar panel. The proposed input-regulated boost energy harvester was developed in a 0.35- µm CMOS process. With IAHA, the harvester achieves the MPPT efficiency >95% over an output power range from 0.65 mW to 1 W that is significantly wider than other previous state-of-the-art designs. This harvester also provides at least five times improvement in the output power range for achieving >85% power efficiency. The SRE FOCV MPPT scheme achieves a 2.9-ms MPPT transient time that reduces the prior FOCV transient time by 86 times.