A 40mV start up voltage DC - DC converter for thermoelectric energy harvesting applications

A low start up voltage DC - DC converter for thermoelectric energy harvesting is presented in this paper. Output voltage of a thermoelectric energy generator (TEG) provides an output voltage from 40mV to 400mV, depending of thermal gradient. In order to increase input voltage, a boost converter is used. The proposed DC - DC converter is composed of two main sections. One provides a high duty cycle pulse width modulation for a forward control. It is used when the voltage coming from the TEG, is in the 40mV to 150mV range. As the TEG voltage it is higher than 150mV, a feedback circuit is switched on. It provides a more accurate control of the output voltage. Entire DC - DC converter is implemented in a 65nm bulk CMOS technology.