An Efficient Polarity Detection Technique for Thermoelectric Harvester in L-based Converters

This paper presents a new method for detecting and reversing the polarity of a low-voltage thermoelectric generator (TEG) in inductor-based converters. The proposed technique makes use of the inductor response to a voltage change due to the flip in the TEG polarity. The inductor voltage provides two distinguishable states which correspond to the normal and the reversed TEG polarity. A switch matrix circuit is then used to correct the polarity by physically reversing the TEG connection. The detection circuit along with the switch matrix provide a positive input voltage from the TEG to the inductor-based converter. The proposed technique is an efficient polarity detection with all-digital implementation, fully integrated, small area and power overhead. The prototype chip is fabricated in 65-nm CMOS and occupies an area of 0.09 mm². Measurement results confirm a maximum efficiency of 70% at 50 mV TEG voltage and 40 μA output current. The proposed technique is part of an autonomous thermal energy harvesting system that detects and corrects the TEG polarity.