Design and analysis of MEMS step up voltage converters

This paper presents a comprehensive analysis of voltage step-up converters for energy harvesting and other low-power applications. The step-up operation is based on isolating the charge of a mechanically variable capacitor and varying the gap between the electrodes by an appropriate method of providing an actuation force i.e. electrostatic or physical. Two devices are presented; a bi-stable device and a resonant device, specifically designed for solar and vibration energy harvesting respectively. The bi-stable device introduces a separate electrostatic actuator element to manipulate the variable capacitor electrodes, whereas, in the case of the resonant device, ambient vibrations provide the necessary actuation force. System-level Multisim models have been developed and verified using 3D FEM Coventorware and MEMS+ simulations. The devices were then fabricated using a dicing-free Silicon-on-Insulator (SOI) process developed at the Southampton Nanofabrication Centre.