A High-Voltage PMIC Using an Efficient Perturb and Observe Technique for Energy Harvesting of Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) have drawn much interest for their ability to recycle various forms of unused energy, such as naturally available vibrations and rotations. However, handling the high-voltage (HV) inputs from TENGs has been a challenging task when a power management integrated circuit (PMIC) is considered. Specifically, HV source characteristics limit converter structures and design strategies for maximum power point tracking (MPPT) and input sensing. To address this issue, this study presents a PMIC suitable for TENG energy harvesting. Three key features of this work are perturb and observe based MPPT suitable for TENG energy harvesting implemented efficiently using a novel mixed-signal approach, a filter-based inductor current sensor suitable for measuring the small current from the TENG, and ultralow-power (2.3 nW) voltage and current sensors that measure the HV input from the TENG. Our MPPT approach is based on a simple proportional relationship between the input power and converted digital value. In addition, the proposed approach is implemented using simple pulse counting, which can be realized without a high-power and high-gain amplifier. The digital implementation has a low power consumption of 67 nW. The inductor current sensor is designed to meet the unique TENG characteristics of HV and small current. The proposed PMIC is fabricated using a 180-nm bipolar-CMOS-double-diffused metal oxide semiconductor (DMOS) process. The maximum input voltage to the PMIC is 70 V. All the functions of the integrated circuit are realized using only 786.2 nW. Characterization of the PMIC is performed using fluorinated ethylene propylene-based TENG operating in contact-separation mode. The measured results show a peak tracking efficiency of 97.8% that is achieved at an input power of 88 mu W. A peak end-to-end efficiency of 81.2% is achieved when delivering 153 mu W output power.