A Biofuel-Cell-Based Energy Harvester With 86% Peak Efficiency and 0.25-V Minimum Input Voltage Using Source-Adaptive MPPT

Abstract

This article presents an efficient cold-starting energy harvester system, fabricated in 65-nm CMOS. The proposed harvester uses no external electrical components and is compatible with biofuel-cell (BFC) voltage and power ranges. A power-efficient system architecture is proposed to keep the internal circuitry operating at 0.4 V while regulating the output voltage at 1 V using switched-capacitor dc-dc converters and a hysteretic controller. A startup enhancement block is presented to facilitate cold startup with any arbitrary input voltage. A realtime on-chip 2-D maximum power point tracking with source degradation tracing is also implemented to maintain power efficiency maximized over time. The system performs cold startup with a minimum input voltage of 0.39 V and continues its operation if the input voltage degrades to as low as 0.25 V. Peak power efficiency of 86% is achieved at 0.39 V of input voltage and 1.34 µW of output power with 220 nW of average power consumption of the chip. The end-to-end power efficiency is kept above 70% for a wide range of loading powers from 1 to 12 µW. The chip is integrated with a pair of lactate BFC electrodes with 2 mm of diameter on a prototype-printed circuit board (PCB). Integrated operation of the chip with the electrodes and a lactate solution is demonstrated.Index Terms-Biofuel-cell (BFC), CMOS, cold startup, dc-dc voltage converter, energy harvester, health monitoring, power management, source-adaptive maximum power point tracking (MPPT), wearable sensor. I. INTRODUCTIONR ECENT advances in low-power electronics have paved the way for a wide range of wearable and implantable biomedical devices for health monitoring and fitness applications. Integration of such millimeter-scale devices on biocompatible platforms shows great potentials for real-time biochemical sensing [1]- [6]. Many personalized monitoring biodevices are designed to perform multiple tasks, such as on-demand wake-up, multiplexed sensing, data processing, and wireless data transmission. These power-demanding operations are performed continuously or periodically over long Manuscript

Smart Clothing Framework for Health Monitoring Applications

“…Talkhooncheh et al [48] have proposed an efficient cold-starting biofuel-cell-based energy harvester system, fabricated in 65 nm CMOS, which can perform a cold start-up with a low voltage (0.39 V) by employing a start-up enhancement block where a power efficiency of 86% is achieved. The outcome of this research is that the energy harvester chip can attain an enhanced efficiency with below 0.4 V of input voltage and 5.5 µW of average output power.…”

“…Although many research works are currently being conducted on wearable technology and smart clothing, a lot of technical challenges have also been observed in the state of the art. For example, there is a lack of control over oscillation failure at lower supplies in the sensors system of wearable technology [48]. Additionally, there is a shortage of information provided on developing smart clothing materials and a comprehensive framework combining both the development and decision making [50,51].…”

A High Power-Conversion-Efficiency Voltage Boost Converter with MPPT for Wireless Sensor Nodes

“…It uses the accumulation and release of charge in the capacitor to generate high voltage. The efficiency of the conventional Dickson charge pump is minimal due to body-effect, and diodes are difficult to manufacture in actual situations [ 22 , 23 , 24 , 25 , 26 ].…”

A Low-Power CMOS Bandgap Voltage Reference for Supply Voltages Down to 0.5 V

“…One of the main challenges posed by these devices is related to the availability of very low power budgets, typically provided by small batteries and/or energy harvesters. Among the latter, BioFuel Cells (BFCs) [8,9] and ThermoElectric Generators (TEGs) [10][11][12] have received considerable interest in the last few years for applications that include and go beyond wearable devices. TEGs and BFCs provide supply voltages that can drop well below 1 V depending on the environmental conditions, and depending on their size, their available power may be as small as a few hundred nanowatts [13].…”