Characteristic Analysis of MEMS Electrostatic Vibration Energy Harvester based on the Bennet’s Doubler Circuit

Abstract

Recently, IoT(Internet of Things) technology is one of the hot research topics. With the advent of MEMS(Micro Electro-Mechanical System) technology, the IoT modules (sensors, microcontroller, signal processing circuit, transceiver, power supply, etc.) have become smaller, and it has been possible to integrate all the IoT modules on a single chip. But the power supply still relies on the battery, which needs to be replaced periodically. The MEMS electrostatic vibration energy harvester is one of the solutions removing the troublesome replacement of the battery.

In this thesis, an electrostatic MEMS resonator was designed and fabricated on the top layer of an SOI (Silicon on Insulator) wafer, and the fabricated resonator was inspected by an optical microscope and actuated by electric force. Its driving characteristics were evaluated in terms of moving distance, which makes the capacitance variance and generates current flow. An equivalent circuit of Bennet’s doubler was introduced for rectifying the current and charging the reservoir capacitor. The energy harvester was characterized by investigating the regime in time domain for the first time, showing sufficient electrical power could be stored for operating an accelerometer, one of typical IoT sensors.