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1. Split-Capacitor Boost Converter Operating in Boundary Conduction Mode with Impedance Matching for Kinetic Energy Harvesting

   https://doi.org/10.1109/MWSCAS48704.2020.9184507  

   Jaquan Dancy, Alante ; Li, Jiayu ; Sam Ha, Dong ( August 2020 , 2020 IEEE 63rd International Midwest Symposium on Circuits and Systems (MWSCAS))

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   The proposed circuit intends for an electromagnetic generator to harvest kinetic energy. A synchronous split-capacitor boost converter operating in boundary conduction mode (BCM) is proposed to efficiently convert the AC input to a DC output. BCM operation is uniquely achieved through zero current detection (ZCD) control of an AC input enabling impedance matching. The ZCD control offers simplicity over previously reported methodologies. To reduce power consumption and increase efficiency, the proposed circuit topology combines the rectifier and power stage while dynamically controlling the power stage. The proposed circuit is designed and laid out in 0.13 μm BiCMOS technology. Post layout simulations verify the operation of the proposed circuit. 

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2. A Circuit for Simultaneous Reception of Data and Power using a Solar Cell

   https://doi.org/10.1109/TGCN.2021.3087008  

   Kadirvelu, Sindhubala ; Leon-Salas, Walter D. ; Fan, Xiaozhe ; Kim, Jongseok ; Peleato, Borja ; Mohammadi, Saeed ; Vijayalakshmi, B. ( June 2021 , IEEE Transactions on Green Communications and Networking)

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   This paper presents a circuit for simultaneous reception of optical power and data using a solar cell. The circuit employs a switched-inductor boost DC-DC converter for energy harvesting and a low-power thresholding receiver for data reception. The thresholding data receiver comprises a current-sense resistor that monitors the current output of the solar cell, an instrumentation amplifier, a band-pass filter and a comparator. A system-level analysis of an optical communication system employing the proposed circuit is presented along with a circuit-level analysis and implementation. As a proof-of-concept, the proposed circuit for simultaneous power and data reception is implemented using off-the-shelf components and tested using a custom-built test setup. Measurement results, including harvested power, electronic noise and bit error rate (BER), are reported for a GaAs solar cell and a red LED light source. Results show that 223 μW of power are harvested by the DC-DC converter at a distance of 32.5 cm and a radiated power of 9.3 mW. At a modulation depth of 50% and a transmission speed of 2.5 kbps, a BER of 1.008×10^-3 is achieved. Measurement results reveal that the proposed solution exhibits a trade-off between harvested power, transmission speed and BER. 

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3. Highly Efficient Rectifier and DC-DC Converter Designed in 180 nm CMOS Process for Ultra-Low Frequency Energy Harvesting Applications

   https://doi.org/10.1109/DCAS51144.2020.9330671  

   Gunti, Avinash ; Biswas, Dipon K. ; Mahbub, Ifana ; Adhikari, Pashupati R. ; Reid, Russell C. ( November 2020 , 2020 IEEE 14th Dallas Circuits and Systems Conference (DCAS))

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   This paper presents the integration of an AC-DC rectifier and a DC-DC boost converter circuit designed in 180 nm CMOS process for ultra-low frequency (<; 10 Hz) energy harvesting applications. The proposed rectifier is a very low voltage CMOS rectifier circuit that rectifies the low-frequency signal of 100-250 mV amplitude and 1-10 Hz frequency into DC voltage. In this work, the energy is harvested from the REWOD (reverse electrowetting-on-dielectric) generator, which is a reverse electrowetting technique that converts mechanical vibrations to electrical energy. The objective is to develop a REWOD-based self-powered motion (such as walking, running, jogging, etc.) tracking sensors that can be worn, thus harvesting energy from regular activities. To this end, the proposed circuits are designed in such a way that the output from the REWOD is rectified and regulated using a DC-DC converter which is a 5-stage cross-coupled switching circuit. Simulation results show a voltage range of 1.1 V-2.1 V, i.e., 850-1200% voltage conversion efficiency (VCE) and 30% power conversion efficiency (PCE) for low input signal in the range 100-250 mV in the low-frequency range. This performance verifies the integration of the rectifier and DC-DC boost converter which makes it highly suitable for various motion-based energy harvesting applications. 

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4. MaxTracker: Continuously Tracking the Maximum Computation Progress for Energy Harvesting ReRAM-based CNN Accelerators

   https://doi.org/10.1145/3477009  

   Qiu, Keni ; Jao, Nicholas ; Zhou, Kunyu ; Liu, Yongpan ; Sampson, Jack ; Kandemir, Mahmut Taylan ; Narayanan, Vijaykrishnan ( October 2021 , ACM Transactions on Embedded Computing Systems)

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   There is an ongoing trend to increasingly offload inference tasks, such as CNNs, to edge devices in many IoT scenarios. As energy harvesting is an attractive IoT power source, recent ReRAM-based CNN accelerators have been designed for operation on harvested energy. When addressing the instability problems of harvested energy, prior optimization techniques often assume that the load is fixed, overlooking the close interactions among input power, computational load, and circuit efficiency, or adapt the dynamic load to match the just-in-time incoming power under a simple harvesting architecture with no intermediate energy storage. Targeting a more efficient harvesting architecture equipped with both energy storage and energy delivery modules, this paper is the first effort to target whole system, end-to-end efficiency for an energy harvesting ReRAM-based accelerator. First, we model the relationships among ReRAM load power, DC-DC converter efficiency, and power failure overhead. Then, a maximum computation progress tracking scheme ( MaxTracker ) is proposed to achieve a joint optimization of the whole system by tuning the load power of the ReRAM-based accelerator. Specifically, MaxTracker accommodates both continuous and intermittent computing schemes and provides dynamic ReRAM load according to harvesting scenarios. We evaluate MaxTracker over four input power scenarios, and the experimental results show average speedups of 38.4%/40.3% (up to 51.3%/84.4%), over a full activation scheme (with energy storage) and order-of-magnitude speedups over the recently proposed (energy storage-less) ResiRCA technique. Furthermore, we also explore MaxTracker in combination with the Capybara reconfigurable capacitor approach to offer more flexible tuners and thus further boost the system performance. 

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5. Thermoelectric energy harvesting for wireless onboard rail condition monitoring

   https://doi.org/10.1080/23248378.2023.2201247  

   Foltz, Heinrich ; Tarawneh, Constantine ; Amaro, Martin ; Thomas, Sebastian ; Capitanachi Avila, Danna ( April 2023 , International Journal of Rail Transportation)

   A thermoelectric energy harvesting device is evaluated to power a bearing health monitoring system. Unlike wayside equipment, the new system is an onboard wireless solution utilizing accelerometer and temperature sensors to assess the bearing condition continuously. The harvesting system consists of two thermoelectric generator modules with aluminium heat sinks, a switching boost converter, a battery management circuit, and a lithium rechargeable battery. The performance of the harvester is validated on an AAR class bearing mounted on a laboratory tester, with load and speed simulating common freight routes of up to 896 miles. The energy harvested varies with operating conditions, and data is presented showing the effect of load and speed. Over a realistic route, the net energy harvested is more than double that needed to indefinitely power a Bluetooth Low Energy sensor. The critical design parameters are the ratio of open-circuit voltage to the temperature difference for the thermoelectric module, and the cold start voltage of the boost converter. 

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