Power Management System With Integrated Maximum Power Extraction Algorithm for Microbial Fuel Cells

Microbial fuel cells (MFC) are alternative renewable power sources that can directly produce electricity from biodegradable substances. However, due to their low power and voltage production, power management systems (PMS) are required to process the MFC power to a more readily usable level. For this application, a monolithic PMS with an integrated maximum power extraction algorithm (MPEA) is proposed. The MPEA allows for quick and accurate pin-pointing of the matching conditions for maximum power transfer from the MFC to the PMS. The PMS delivers a regulated fixed voltage from low fluctuating voltages produced by MFC at maximum power point to a supercapacitor from which electronic devices, such as wireless sensors, for extended operation time can be directly powered. Along with the MPEA system, the PMS is composed of a dc-dc boost converter operating in discontinuous conduction mode to maximize efficiency. In addition, a zero current switching tracking loop is proposed to improve overall system efficiency and minimize losses in the PMS through accurate P-type Metal-oxide-semiconductor field-effect transistor on/off timing control. The PMS circuit was fabricated in 0.5-μm CMOS technology. The maximum dynamic efficiency measured was ~58% for a load of ~250 μW.