Search

There are increasing demands for the Internet of Things (IoT), wearable electronics, and medical implants. Wearable devices provide various important daily applications by monitoring real-life human activities. They demand low-cost autonomous operation in a miniaturized form factor, which is challenging to realize using a rechargeable battery. One promising energy source is thermoelectric generators (TEGs), considered the only way to generate a small amount of electric power for the autonomous operation of wearable devices. In this work, we propose a compact and efficient converter system for energy harvesting from TEGs. The system consists of an 83.7% efficient boost converter and a 90 mV self-startup, sharing a single inductor. Innovated techniques are applied to adaptive maximum power point tracking (A-MPPT) and indirect zero current switching (I-ZCS) controllers for efficient operation. The startup circuit is realized using a gain-boosted tri-state buffer, which achieves 69.8% improved gain at the input VIN = 200 mV compared to the conventional approach. To extract the maximum power, we use an A-MPPT controller based on a simple capacitive divider, achieving 95.2% tracking efficiency. To address the challenge of realizing accurate voltage or current sensors, we propose an I-ZCS controller based on a new concept of maximum output voltage tracking (MOVT). The integrated circuit (IC) is fabricated using a 28 nm CMOS in a compact chip area of 0.03 mm2. The compact size, which has not been obtained with previous designs, is suitable for wearable device applications. Measured results show successful startup operation at an ultralow input, VIN = 90 mV. A peak conversion efficiency of 85.9% is achieved for the output of 1.07 mW. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have shown great potential as sustainable energy sources with the advantages of a lightweight, low cost, simple fabrication, and small size. Nevertheless, schemes for efficient power extraction from TENGs remains difficult, partly because of their short, high‐voltage (HV) pulse output. The available power from a single TENG is not usually enough for practical applications. An efficient power management system for TENGs using a dynamically reconfigured combining method and dual‐parameter maximum power point tracking (MPPT) is proposed. A series to parallel/parallel to series (SPPS) adaptive control method, which dynamically reconfigures the connection of multiple TENGs, efficiently combines the outputs. An MPPT method, which adjusts the dual parameters in a closed‐loop, provides a wide range for matching the high output impedance (≈MΩ) of TENGs. The proposed technique is implemented using a 416 nW energy harvester interface integrated circuit (EHI‐IC), realized using a 180 nm, 48 V Bipolar‐CMOS‐DMOS (BCD) process. Measured results show that the proposed approach achieves a 159‐fold improvement in power extraction compared to the results without EHI‐IC. Finally, a triboelectric energy harvesting ball (T‐EHB), which combines 12 TENG pairs for multi‐axis excitation, and several examples of device powering are presented using the T‐EHB. [ABSTRACT FROM AUTHOR]