A Series-Parallel Switched-Photovoltaic DC–DC Converter

This article introduces a switched-photovoltaic (SPV) DC–DC converter that switches the photovoltaic (PV) cells of a series solar string periodically in parallel to balance their voltages and extract the maximum available power under mismatch conditions. Without any assistance from an external DC–DC converter, the SPV converter exploits the intrinsic capacitance of the PV cells to establish an implicit 1:
$n$
switched-capacitor (SC) converter that allows the extra current of the stronger cells in the string to flow around the underperforming cells to the output, instead of getting shunted to the ground. Fabricated in a
$0.18 \mu \text{m}$
CMOS process, the SPV converter achieves a peak harvesting efficiency of 91.3% under 50% current mismatch among the employed PV cells, demonstrating 30.2% efficiency improvement over the prior solutions.