A Redistributable Capacitive Power Converter for Indoor Light-Powered Batteryless IoT Devices

This letter presents a redistributable capacitive power converter for batteryless optically powered Internet-of-Things (IoT) devices. The proposed converter employs a redistributable two-stage charge pump along with a storage capacitor to power milliwatt order low-power RF power amplifier occasionally using indoor light illumination. The first stage tracks the maximum power point of the photovoltaic (PV) cell and stores the energy to the storage capacitor. The second stage further boosts the output to 1.5 V with voltage regulation. The proposed capacitive converter is composed of 16 1.5×/2× reconfigurable charge pump submodules and a digital low-dropout regulator (DLDO) to adapt 0.45- 0.9-V PV input with high efficiency. The submodules are redistributed among two stages according to operating mode to reduce 46.7% onchip capacitors. The proposed capacitive power converter is fabricated in 0.18-μm CMOS process. The measured results demonstrate the peak power conversion efficiency is 91%, 63.8%, and 68.5% under 1×, 1.5×, and 2× conversion ratios, respectively.