A Reconfigurable Self-Clamp CSCR Converter With Fast-Converging MPPT for Energy Harvesting

Abstract

This article presents a reconfigurable self-clamp, continuously scalable-conversion-ratio (CSCR) switched-capacitor (SC) converter for photovoltaic (PV) solar energy harvesting (EH). By reducing flying-capacitor voltage stress without additional SC stages, the proposed architecture enables high-density capacitors and mitigates the complexity-loss tradeoff of conventional CSCR converters. A clamp-stage outphasing technique improves the power conversion efficiency (PCE), while a design methodology for selecting the number of flying and clamping capacitors is established. In addition, an insight is revealed for reducing the energy penalty of open-circuit-voltage (OCV)-based maximum power point tracking (MPPT). The reconfigurable-clamp-mode scheme extends the high-PCE voltage conversion-ratio (VCR) range and improves MPPT accuracy. Fabricated in a 180-nm CMOS process, the prototype exhibits 90% peak PCE, a high-PCE VCR ratio of 3.83 using only thirteen capacitors, and MPPT accuracy above 96.7% over a wide light-intensity (LI) range with a 334-μs convergence time.