23.6 A 43V 400mW-to-21W global-search-based photovoltaic energy harvester with 350μs transient time, 99.9% MPPT efficiency, and 94% power efficiency

Standalone systems such as outdoor lighting and remote monitoring stations can be self-powered by solar panels (SPs) having output powers of tens of watts. When the size of the SP is large, part of it can be shaded by birds, trees and other objects resulting in partial shading conditions (PSCs). Multiple local maxima in the power-versus-voltage (P-V) curve of the SP are generated during PSCs. Based on a 10W SP measurement, ~30% of the available power of the SP can be lost if an energy harvester only operates at the lower local maximum power point during PSC. This issue was previously addressed by using the approach of module-integrated converters (MIC), which are tied to smaller modules of the SP. Since none of the previously reported integrated maximum power point tracking (MPPT) techniques in MIC can track the global maximum power point (GMPP) of the P-V curve, the number of MICs would have to increase significantly in a large-size tens-of-watt SP. This increases the volume, weight, and cost of the photovoltaic system. In addition, previous harvester ICs have adopted the constant-frequency pulse-width-modulation control scheme, which has significant switching power loss under low solar irradiance.