A 220-mV Power-on-Reset Based Self-Starter With 2-nW Quiescent Power for Thermoelectric Energy Harvesting Systems
Miniaturized thin-film thermoelectric generators (TEGs) are emerging energy harvesting sources suitable for wearable and implantable applications. However, these sources usually exhibit large internal equivalent series resistance (ESR) that leads to low energy conversion efficiency and self-startup failures at ultra-low voltages. This paper presents a highly efficient boost converter with a novel Power-on-Reset (PoR) based self-startup circuit for systems harvesting the micro-scale thermal energy. The proposed circuit generates a train of pulses to kick start the self-startup through an internal feedback loop formed by the ESR of TEG, an auxiliary boost converter and a PoR circuit. The self-startup circuit is automatically disabled after the startup operation with a quiescent power consumption of 2 nW. A boost converter test chip with the proposed self-starter was fabricated in 65-nm CMOS technology node. It achieved a self-startup TEG voltage of 220 mV and a peak conversion efficiency of 76%. The minimum input voltage to sustain the boost operation is as low as 85 mV after the startup.