Battery-assisted and photovoltaic-sourced switched-inductor CMOS harvesting charger-supply

A challenge wireless microsensors and other microsystems face is short lifetime, because tiny batteries store little energy. Fortunately, the environment holds vast amounts of energy, and of available sources, like light, motion, temperature, and radiation, solar light produces the highest power density. Still, micro-scale photovoltaic (PV) cells harness a diminutive fraction of light and artificial lighting avails a small percentage of what solar light can, which means the PV cell needs assistance from a battery. Mixing PV and battery power to supply a microwatt system, however, requires a smart and low-loss circuit. For that, the battery-assisted pulse-width-modulated (PWM) buck-boost single-inductor 0.18-μm CMOS harvester-supply proposed and simulated here uses up to 100 μW from a PV cell to supply up to 1 mA and regulate 1 V within 25 mV at 10-80 kHz and with 77%-89% efficiency.