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

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 irradiance 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-mu m 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.