Energy-harvesting microsensors: Low-energy task schedule & fast drought-recovery design

• Published in: 2016 IEEE 59th International Midwest Symposium on Circuits and Systems (MWSCAS) pp. 1 - 4
• Main Authors: Blanco, Andres A., Rincon-Mora, Gabriel A.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.10.2016
• Subjects: Batteries; Circuits and systems; Discharges (electric); energy harvesting; Energy-drought recovery; low-energy task schedule; microsensor; Microsensors; microsystem; Power supplies; Schedules; startup; wake
• ISSN: 1558-3899
• DOI: 10.1109/MWSCAS.2016.7869964

The main challenge with microsensors is limited space, because tiny batteries store little energy. Harvesting energy helps, but only when ambient energy is available. And even then, power is low because miniaturized transducers harness little power. This is why managing how and when to schedule functional tasks is so important. This paper proposes a schedule that requires the battery to hold only the energy necessary to sustain single events and allows the battery to drain across harvesting droughts. When input power returns, an inefficient starter charges a temporary supply that bootstraps the system quickly into an efficient state. This way, when harvested input, idle, and peak load power are 10, 0.5, and 1000 μW, a 0.7% efficient starter and an 87% efficient charger can recharge a 1.8-μF battery to 1 V in 220 ms with a 71-pF temporary supply and in 13 s without the temporary supply. The system therefore wakes 59× faster than without a temporary supply and 1880× faster and with 1800× less capacitance than when forcing the battery to survive a 2-hour power outage.