On-chip reconfigurable switched-capacitor DC–DC converter for indoor PV energy harvesting

Abstract

A reconfigurable switched-capacitor DC-DC converter is presented for indoor photovoltaic energy harvesting. A uniform hysteresis controller regulates the PV cell voltage at 1.5 V to extract the maximum power from the PV cell and regulates the load voltage at 0.9 V. To minimise the conversion loss, the energy is transferred from the PV cell to the load directly whenever energy is available in the PV cell. When the load voltage is high, the excess energy in the PV cell is stored in the buffer of 1.8 V. The load draws energy from the buffer when energy is not available in the PV cell. The proposed converter was fabricated in 0.18 μm CMOS process and achieves peak efficiencies of 87, 88 and 78% while delivering energy from the PV cell to the load, from the PV cell to the buffer and from the buffer to the load, respectively.