Fuzzy logic-based micro power supply for MEMS applications

A severe limitation on the functional capability of remote, autonomous, microelectromechanical system (MEMS)-based sensors is the lack of a suitable micro power supply to power these devices. Such sensors often have low power requirements that may be provided by the combination of an energy scavenger (e.g., a solar cell) and a rechargeable microbattery made using integrated circuit fabrication methods. While rechargeable mu batteries and solar cells have been previously demonstrated, the development of a micro-charge/discharge controller has not. In this paper we present a novel fuzzy logic-based solar charge controller that allows control of the charge/discharge of mu batteries. A breadboard implementation of the controller and its integration with a solar cell and mu battery will be presented. The circuit topology of the mu battery controller is based on a buck converter design. During charging the solar cell's operating point is adjusted by modulating the duty cycle of the buck converter's switching MOSFET using a fuzzy logic control algorithm to optimally charge the mu battery.