Power Conversion Circuitry for Electrostatic Energy Harvester

Abstract

Energy harvesting is a potential approach to power autonomous wireless sensor systems and electronic circuits. It can potentially replace batteries, reduce the required size of batteries or even make sensors possible where batteries cannot be used. One among several possibilities is to harvesting energy from ambient vibrations. This project focuses on designing a power circuit for electrostatic energy harvesters which is based on the doubler of charge. The advantages of the circuit are very low power loss thanks to a simple structure, achieving high power by maintaining high bias voltage, able to recharge a storage capacitor without using additional circuits. The efficiency of the circuit remarkably depends on the displacement of a proof mass. The thesis carries out the analyses and comparisons between the doubler operation in asymmetrical energy harvesters and that in symmetrical ones to propose many advantages of asymmetrical structures in terms of higher output power and smaller minimum required mass displacement. Furthermore, buck converters with an autonomous MEMS switch or a controlled electronic switch are utilized in order to transfer the energy in the storage capacitor into a load and keep the output power maximal. LTSPICE simulations and experiments show intriguing results of the doubler circuit in symmetrical and asymmetrical energy harvesting systems.