A 0.4W-to-21W Fast-Transient Global-Search-Algorithm Based Integrated Photovoltaic Energy Harvester With 99% GMPPT Efficiency and 94% Power Efficiency

Abstract

This paper presents an integrated photovoltaic energy harvester that is capable of performing global maximum power point tracking (GMPPT) with significant reductions in MPPT transient time, power dissipation and silicon area. A fasttransient global search algorithm is proposed to identify the GMPP of a solar panel within hundreds of μs in the presence of multiple local maxima during partial shading conditions. The pulse integration based MPPT circuitry enables highprecision MPPT. Ripple-based irradiance aware adaptive frequency control (IAAFC) is also developed to lower the switching power loss under low irradiance levels, improving the harvester power efficiency over a wide output power range. The proposed energy harvester was implemented in 50 V 0.35 μm CMOS. It tracks the GMPP in 350 μs in the presence of two local maxima with 99% GMPP tracking efficiency. The IAAFC enables the proposed harvester to achieve > 85% power efficiency over a wide power range from 0.98 to 21 W with the peak power efficiency of 94.2% at 1 MHz. The proposed harvester improves the MPPT transient time and the power density by at least 4.5 times and 6 times, respectively, compared with state-ofthe-art counterparts.