Realization of energy-autonomous wireless sensor nodes requires design & integration of efficient power conditioning circuits to energy harvesters. In this work, a 0.25 cm3 stand-alone energy harvesting micro-platform is introduced to efficiently scavenge, rectify and store ambient vibration energy with batteryless cold start-up and zero sleep-mode power consumption. The fabricated compact system integrates a vacuum-packaged MEMS vibration harvester with an efficient power management IC and a 70 mF ultra-capacitor. The circuitry incorporates a rectification stage with low voltage drop, a bias-flip stage with a novel control system for increased efficiency, a trickle charger for permanent storage of harvested energy, and a low-power supply-independent bias generator. The system is completely self-supplied by vibration energy, does not require a pre-charged battery, and has power consumption of <0.5 μW in active-mode and <10 pW in sleep-mode. The end-to-end rectification efficiency from the harvester to the ultra-capacitor is measured as 58-86%, and the platform can harvest from a minimum vibration level of 0.1 g.
E. E. Aktakka, K. Najafi, “A micro inertial energy harvesting platform with self-supplied power management circuit for autonomous wireless sensor nodes,” IEEE Journal of Solid State Circuits, vol. 49, pp. 2017-2029, 2014. [PDF]
E. E. Aktakka, R.L. Peterson, K. Najafi, “A self-supplied inertial piezoelectric energy harvester with power management IC”, IEEE International Solid-State Circuits Conference (ISSCC’11), San Francisco, USA, pp. 120-121, Feb. 2011. [PDF]