A 11 mV Input Boost Converter for Low Thermal Gradients Energy Harvesting Applications

In this paper an enhanced self-powered ultra-low input voltage DC-DC converter is presented. The circuit is intended to be used as cold startup circuit where extremely low input voltage sources are available. For example, this could be the case of energy harvesting circuits targeting ThermoElectric Generators (TEGs) operating with a very low thermal gradient (i.e. lower than 1°C). An input voltage of only 11mV is enough for a cold startup of the converter and to obtain a 3.3 V output voltage in no load conditions. Experimental results shown as an input voltage of 13 mV is enough to allow the charge of two fully discharged 1 mF capacitor and simultaneously deliver power to a resistive load emulating devices running low duty cycle applications (e.g. low-power wireless sensor nodes). Measurements carried out in a 11÷40 mV input voltage range shown end-to-end conversion efficiencies in the range 18÷22% with output power in the range 15÷300 µW, depending on input voltage and connected load. As further distinguish feature, the proposed solution has been realized using only discrete commercial components.