A Micro Inertial Energy Harvesting Platform With Self-Supplied Power Management Circuit for Autonomous Wireless Sensor Nodes

A 0.25 cm(3) autonomous energy harvesting micro-platform is realized 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 high-performance vacuum-packaged piezoelectric MEMS energy harvester with a power management IC and surface-mount components including an ultra-capacitor. The power management circuit incorporates a rectification stage with similar to 30 mV voltage drop, a bias-flip stage with a novel control system for increased harvesting efficiency, a trickle charger for permanent storage of harvested energy, and a low power supply-independent bias circuitry. The overall system weighs less than 0.6 grams, does not require a pre-charged battery, and has power consumption of 0.5 mu W in active-mode and <10 pW in sleep-mode operation. While excited with 1 g vibration, the platform is tested to charge an initially depleted 70 mF ultra-capacitor to 1.85 V in 50 minutes (at 155 Hz vibration), and a 20 mF ultra-capacitor to 1.35 V in 7.5 min (at 419 Hz). The end-to-end rectification efficiency from the harvester to the ultra-capacitor is measured as 58-86%. The system can harvest from a minimum vibration level of 0.1 g.