Power Solutions of A Vibration-Powered Sensor Node

Vibration energy harvesting (VEH) technology enables the Internet of Things (IoT) devices and applications to be deployed at any place, where mechanical vibrations or motions are available. Given the intermittent, stochastic, or impulsive features of many ambient vibration sources, the VEH-based IoT systems must have a reliable energy management unit (EMU), carefully dealing with energy fluctuation and uncertainty. The cyber part of these systems should also schedule tasks by taking a substantial consideration of the source features. Emerging energy-aware state checkpointing technique enables fault-tolerant computations and lets the program survive longer under energy fluctuation or shortage. This paper focuses on the power solutions of energy-aware VEH-based IoT systems. Three possible power solutions are discussed in detail. The most fundamental one is based on an off-the-shelf dc-dc converter with fixed-threshold under-voltage lockout (UVLO). The second one adds an energy-level indicator as a passive interrupt for better realizing the energy-aware computing tasks. The third one uses the on-chip analog-to-digital converter (ADC) to carry out active polling for estimating the energy level in the storage capacitor. Both the second and third designs can reinforce the energy-awareness of the VEH based IoT systems towards a more robust operation. The system performances using these power conditionings under intermittent vibration excitation are experimentally studied based on a vibration-powered IoT platform. The energy overheads of the fundamental regulator module and additional interrupt or polling types of energy storage monitoring are also quantified. Useful comments are drawn based on this comparative study. They help VEH system designers to better select a suitable solution for realizing the specific IoT design targets.