An Area Efficient Thermal Energy Harvester With Reconfigurable Capacitor Charge Pump for IoT Applications

Abstract

This brief introduces an integrated energy harvester system targeting Internet of Things sensor applications such as a wireless temperature sensor. The proposed design provides 1-V regulated voltage boosting the input voltage (0.27–1 V) from a thermoelectric generator (TEG). To ensure the maximum power extraction, the proposed energy harvester includes multiple circuit level techniques. First, the reconfigurable capacitor charge pump distributes on-chip capacitors to required step-up stages. This approach optimizes the silicon area by utilizing 100% of on-chip capacitors regardless of charge pump conversion gain. Second, the design is capable of 3-D maximum power point tracking, matching a source impedance to input impedance of the energy harvester. Thus, the proposed design is able to extract power from a small form factor TEG, having low source impedance. The reconfigurable capacitor charge pump has the highest power density while delivering power up to $500~{\mu W}$ . Experimental results show end-to-end power efficiency of 64% @ 1–V output voltage, and an input impedance matching range of $1 {\Omega } - 5~{\mathbf{k}}{\Omega }$ . The energy harvester was fabricated in 130-nm CMOS standard technology with an active area of 0.835 mm2.