A 14-nA, Highly Efficient Triple-Output Thermoelectric Energy Harvesting System Based on a Reconfigurable TEG Array

This paper presents an inductorless triple-output thermoelectric energy harvesting (EH) system based on a reconfigurable thermoelectric generator (TEG) array. The TEG array in the proposed system can be dynamically reconfigured to achieve maximum power point tracking (MPPT) and voltage conversion (VC) for three outputs. Two regulated outputs and an energy recycling mechanism that can store excessive energy in the battery and supplement insufficient energy to the load are provided. An optimization method based on Lagrange multipliers is proposed to size the switches in the switch array and the areal cost can be reduced by 43%. To optimize the control overhead, the building blocks in the control stage are designed to operate in four different frequency domains. An adaptive frequency control scheme is applied to the regulation control loop, making the system able to maintain regulation over a wide power range while achieving 14-nA quiescent current. In addition, a fast wake-up response scheme is designed to cater for the requirement of some applications with duty-cycled operation. The experimental results show that a higher than 86% efficiency can be achieved over an input voltage range of 0.15-10.8 V and an output power range of 38 μW-200 mW with a 99% peak efficiency.