Electrostatic Energy Harvesting Interface Circuits for Microsystems

Abstract

Lilas Al Rahis, 'Electrostatic Energy Harvesting Interface Circuits for Microsystems', M.Sc. Thesis, M. Sc. in Electrical and Computer Engineering, Department of Electrical and Computer Engineering, Khalifa University of Science, Technology and Research, United Arab Emirates, June 2016. The development of electronics systems and Internet of Things (IoT) devices that can operate at low power (mu to n W) range paved the road to alternative energy sources other than traditional battery. The need for small size, low cost, low maintenance of such devices coupled with near perpetual life time operation increase emphasize on energy harvesting. Mechanical vibration is one of the most stable, adaptable and universal existing ambient energy sources. Converting vibrational kinetic energy to electrical energy is implemented using electromagnetic induction, piezoelectric materials or electrostatic transducers. Electrostatic energy scavenging is the most compatible method with Complementary Metal Oxide Semiconductor (CMOS) processes. Electrostatic transduction requires conditioning circuits for biasing and regulating the output voltage.This study provides a comprehensive overview of the conditioning circuits used for electrostatic energy harvesting. In addition to the review, system level analysis of the harvester and the type of interface circuit is designed using the Global Foundries (GF) 65nm process technology and Cadence Electronic Design Automation (EDA) tools. In particular, the impact of initial voltage level and harvester resonance frequency has been studied. The interface circuit prefers higher resonance frequency and high initial voltage level to increase the efficiency, but the preferred output voltage from the harvester exceeds the tolerable voltage by CMOS technology. One of the proposed designs is to have a DC-to-DC buck converter to reduce the electrostatic energy harvesting circuit voltage level to lower value at the load. The second proposed design includes a voltage comparator structure to increase the output power delivered to the load. Last but not least, the third proposed system employs a duty cycle mechanism targetingWireless Sensor Networks (WSN) applications. Indexing Terms: Energy harvesting; Vibration; Electrostatic transducer; Conditioning circuits; WSN.

Date of Award	Jun 2016
Original language	American English
Supervisor	Baker Mohammad (Supervisor)