Fuzzy logic-based solar charge controller for microbatteries

• Main Authors: Singh, P., Rajagopalan, J., LaFollette, R., Fennie, C., Reisner, D.E.
• Format: Conference Proceeding
• Language: English
• Subjects: Buck converters; Circuit topology; Fabrication; Fuzzy control; Fuzzy logic; MOSFET circuits; Optimal control; Photovoltaic cells; Power supplies; Switching converters
• ISSN: 0160-8371
• DOI: 10.1109/PVSC.2000.916237

A severe limitation on the functional capability of remote, autonomous, microelectromechanical (MEMS)-based sensors is the lack of a suitable micropower 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 microbattery ("/spl mu/battery") made rechargeable using integrated circuit fabrication methods. While rechargeable /spl mu/batteries and solar cells have been previously demonstrated, the development of a microcharge/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 /spl mu/batteries. A breadboard implementation of the controller and its integration with a solar cell and /spl mu/attery is presented. The circuit topology of the /spl 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 /spl mu/battery. Discharge data on the /spl mu/batteries and current-voltage characteristics of the solar cell are presented and the fuzzy logic model development for the charge control are also presented.