A 300-mV Low-Power Management System for Energy Harvesting Applications

In this paper, a power management system (PMS) for low-voltage and low-power harvesters is presented. The PMS consists of an energy storage module and a supply regulation (SR) unit. The energy provided by the harvester is first stored in a capacitor CTN. When enough energy is accumulated in CTN, the SR block is enabled and transfers the charge from CTN to an output capacitor COUτ at a higher voltage. The storage process is controlled by a 300-mV voltage supervisor. The voltage stepup process is realized through a two-stage self-starting switching converter, which is able to automatically reconfigure itself after the cold start to improve conversion efficiency during the steady state. Correct system operation is ensured with harvesters that deliver at least 8 μA at 300 mV. The PMS exhibits an average steadystate charge transfer efficiency of 55% in the 2.5 μW-1 mW input power range. The circuit is built with no need for programmable devices and is battery free, low cost, and small sized. A prototype was realized and tested with two different low-voltage harvesters, namely a microbial fuel cell and a photovoltaic cell.