13 research outputs found

    Nano-Power Integrated Circuits for Energy Harvesting

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    The energy harvesting research field has grown considerably in the last decade due to increasing interests in energy autonomous sensing systems, which require smart and efficient interfaces for extracting power from energy source and power management (PM) circuits. This thesis investigates the design trade-offs for minimizing the intrinsic power of PM circuits, in order to allow operation with very weak energy sources. For validation purposes, three different integrated power converter and PM circuits for energy harvesting applications are presented. They have been designed for nano-power operations and single-source converters can operate with input power lower than 1 μW. The first IC is a buck-boost converter for piezoelectric transducers (PZ) implementing Synchronous Electrical Charge Extraction (SECE), a non-linear energy extraction technique. Moreover, Residual Charge Inversion technique is exploited for extracting energy from PZ with weak and irregular excitations (i.e. lower voltage), and the implemented PM policy, named Two-Way Energy Storage, considerably reduces the start-up time of the converter, improving the overall conversion efficiency. The second proposed IC is a general-purpose buck-boost converter for low-voltage DC energy sources, up to 2.5 V. An ultra-low-power MPPT circuit has been designed in order to track variations of source power. Furthermore, a capacitive boost circuit has been included, allowing the converter start-up from a source voltage VDC0 = 223 mV. A nano-power programmable linear regulator is also included in order to provide a stable voltage to the load. The third IC implements an heterogeneous multisource buck-boost converter. It provides up to 9 independent input channels, of which 5 are specific for PZ (with SECE) and 4 for DC energy sources with MPPT. The inductor is shared among channels and an arbiter, designed with asynchronous logic to reduce the energy consumption, avoids simultaneous access to the buck-boost core, with a dynamic schedule based on source priority

    Sistemas eficientes de transmissão de energia sem-fios e identificação por radiofrequência

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    Doutoramento em Engenharia EletrotécnicaIn the IoT context, where billions of connected objects are expected to be ubiquitously deployed worldwide, the frequent battery maintenance of ubiquitous wireless nodes is undesirable or even impossible. In these scenarios, passive-backscatter radios will certainly play a crucial role due to their low cost, low complexity and battery-free operation. However, as passive-backscatter devices are chiefly limited by the WPT link, its efficiency optimization has been a major research concern over the years, gaining even more emphasis in the IoT context. Wireless power transfer has traditionally been carried out using CW signals, and the efficiency improvement has commonly been achieved through circuit design optimization. This thesis explores a fundamentally different approach, in which the optimization is focused on the powering waveforms, rather than the circuits. It is demonstrated through theoretical analysis, simulations and measurements that, given their greater ability to overcome the built-in voltage of rectifying devices, high PAPR multi-sine (MS) signals are capable of more efficiently exciting energy harvesting circuits when compared to CWs. By using optimal MS signals to excite rectifying devices, remarkable RF-DC conversion efficiency gains of up to 15 dB with respect to CW signals were obtained. In order to show the effectiveness of this approach to improve the communication range of passive-backscatter systems, a MS front-end was integrated in a commercial RFID reader and a significant range extension of 25% was observed. Furthermore, a software-defined radio RFID reader, compliant with ISO18000-6C standard and with MS capability, was constructed from scratch. By interrogating passive RFID transponders with MS waveforms, a transponder sensitivity improvement higher than 3 dB was obtained for optimal MS signals. Since the amplification and transmission of high PAPR signals is critical, this work also proposes efficient MS transmitting architectures based on space power combining techniques. This thesis also addresses other not less important issues, namely self-jamming in passive RFID readers, which is the second limiting factor of passive-backscatter systems. A suitable self-jamming suppression scheme was first used for CW signals and then extended to MS signals, yielding a CW isolation up to 50 dB and a MS isolation up 60 dB. Finally, a battery-less remote control system was developed and integrated in a commercial TV device with the purpose of demonstrating a practical application of wireless power transfer and passive-backscatter concepts. This allowed battery-free control of four basic functionalities of the TV (CH+,CH-,VOL+,VOL-).No contexto da internet das coisas (IoT), onde são esperados bilhões de objetos conectados espalhados pelo planeta de forma ubíqua, torna-se impraticável uma frequente manutenção e troca de baterias dos dispositivos sem fios ubíquos. Nestes cenários, os sistemas radio backscatter passivos terão um papel preponderante dado o seu baixo custo, baixa complexidade e não necessidade de baterias nos nós móveis. Uma vez que a transmissão de energia sem fios é o principal aspeto limitativo nestes sistemas, a sua otimização tem sido um tema central de investigação, ganhando ainda mais ênfase no contexto IoT. Tradicionalmente, a transferência de energia sem-fios é feita através de sinais CW e a maximização da eficiência é conseguida através da otimização dos circuitos recetores. Neste trabalho explora-se uma abordagem fundamentalmente diferente, em que a otimização foca-se nas formas de onda em vez dos circuitos. Demonstra-se, teoricamente e através de simulações e medidas que, devido à sua maior capacidade em superar a barreira de potencial intrínseca dos dispositivos retificadores, os sinais multi-seno (MS) de elevado PAPR são capazes de excitar os circuitos de colheita de energia de forma mais eficiente quando comparados com o sinal CW tradicional. Usando sinais MS ótimos em circuitos retificadores, foram verificadas experimentalmente melhorias de eficiência de conversão RF-DC notáveis de até 15 dB relativamente ao sinal CW. A fim de mostrar a eficácia desta abordagem na melhoria da distância de comunicação de sistemas backscatter passivos, integrou-se um front-end MS num leitor RFID comercial e observou-se um aumento significativo de 25% na distância de leitura. Além disso, desenvolveu-se de raiz um leitor RFID baseado em software rádio, compatível com o protocolo ISO18000-6C e capaz de gerar sinais MS, com os quais interrogou-se transponders passivos, obtendo-se ganhos de sensibilidade dos transponders maiores que 3 dB. Uma vez que a amplificação de sinais de elevado PAPR é uma operação crítica, propôs-se também novas arquiteturas eficientes de transmissão baseadas na combinação de sinais em espaço livre. Esta tese aborda também outros aspetos não menos importantes, como o self-jamming em leitores RFID passivos, tido como o segundo fator limitativo neste tipo de sistemas. Estudou-se técnicas de cancelamento de self-jamming CW e estendeu-se o conceito a sinais MS, tendo-se obtido isolamentos entre o transmissor e o recetor de até 50 dB no primeiro caso e de até 60 dB no segundo. Finalmente, com o objetivo de demonstrar uma aplicação prática dos conceitos de transmissão de energia sem fios e comunicação backscatter, desenvolveu-se um sistema de controlo remoto sem pilhas, cujo protótipo foi integrado num televisor comercial a fim de controlar quatro funcionalidades básicas (CH+,CH-,VOL+,VOL-)

    Grid-Connected Renewable Energy Sources

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    The use of renewable energy sources (RESs) is a need of global society. This editorial, and its associated Special Issue “Grid-Connected Renewable Energy Sources”, offers a compilation of some of the recent advances in the analysis of current power systems that are composed after the high penetration of distributed generation (DG) with different RESs. The focus is on both new control configurations and on novel methodologies for the optimal placement and sizing of DG. The eleven accepted papers certainly provide a good contribution to control deployments and methodologies for the allocation and sizing of DG

    Power-Efficient and High-Performance Cicruit Techniques for On-Chip Voltage Regulation and Low-Voltage Filtering

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    This dissertation focuses on two projects. The first one is a power supply rejection (PSR) enhanced with fast settling time (TS) bulk-driven feedforward (BDFF) capacitor-less (CL) low-dropout (LDO) regulator. The second project is a high bandwidth (BW) power adjustable low-voltage (LV) active-RC 4th -order Butterworth low pass filter (LPF). As technology improves, faster and more accurate LDOs with high PSR are going to be required for future on-chip applications and systems.The proposed BDFF CL-LDO will accomplish an improved PSR without degrading TS. This would be achieved by injecting supply noise through the pass device’s bulk terminal in order to cancel the supply noise at the output. The supply injection will be achieved by creating a feedforward path, which compared to feedback paths, that doesn’t degrade stability and therefore allows for faster dynamic performance. A high gain control loop would be used to maintain a high accuracy and dc performance, such as line/load regulation. The proposed CL-LDO will target a PSR better than – 90 dB at low frequencies and – 60 dB at 1 MHz for 50 mA of load current (IvL). The CL-LDO will target a loop gain higher than 90 dB, leading to an improved line and load regulation, and unity-gain frequency (UGF) higher than 20 MHz, which will allow a TS faster than 500 ns. The CL-LDO is going to be fabricated in a CMOS 130 nm technology; consume a quiescent current (IQ) of less than 50 μA; for a dropout voltage of 200 mV and an IvL of 50 mA. As technology scales down, speed and performance requirements increase for on-chip communication systems that reflect the current demand for high speed data-oriented applications. However, in small technologies, it becomes harder to achieve high gain and high speed at the same time because the supply voltage (VvDvD) decreases leaving no room for conventional high gain CMOS structures. The proposed active-RC LPF will accomplish a LV high BW operation that would allow such disadvantages to be overcome. The LPF will be implemented using an active RC structure that allows for the high linearity such communication systems demand. In addition, built-in BW and power configurability would address the demands for increased flexibility usually required in such systems. The proposed LV LPF will target a configurable cut-off frequency (ƒо) of 20/40/80/160 MHz with tuning capabilities and power adjustability for each ƒо. The filter will be fabricated in a CMOS 130 nm technology. The filter characteristics are as following: 4th -order, active-RC, LPF, Butterworth response, VDD = 0.6 V, THD higher than 40 dB and a third-order input intercept point (IIP3) higher than 10 dBm

    Topical Workshop on Electronics for Particle Physics

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    The purpose of the workshop was to present results and original concepts for electronics research and development relevant to particle physics experiments as well as accelerator and beam instrumentation at future facilities; to review the status of electronics for the LHC experiments; to identify and encourage common efforts for the development of electronics; and to promote information exchange and collaboration in the relevant engineering and physics communities

    Solid State Circuits Technologies

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    The evolution of solid-state circuit technology has a long history within a relatively short period of time. This technology has lead to the modern information society that connects us and tools, a large market, and many types of products and applications. The solid-state circuit technology continuously evolves via breakthroughs and improvements every year. This book is devoted to review and present novel approaches for some of the main issues involved in this exciting and vigorous technology. The book is composed of 22 chapters, written by authors coming from 30 different institutions located in 12 different countries throughout the Americas, Asia and Europe. Thus, reflecting the wide international contribution to the book. The broad range of subjects presented in the book offers a general overview of the main issues in modern solid-state circuit technology. Furthermore, the book offers an in depth analysis on specific subjects for specialists. We believe the book is of great scientific and educational value for many readers. I am profoundly indebted to the support provided by all of those involved in the work. First and foremost I would like to acknowledge and thank the authors who worked hard and generously agreed to share their results and knowledge. Second I would like to express my gratitude to the Intech team that invited me to edit the book and give me their full support and a fruitful experience while working together to combine this book

    Electrospun piezoelectric polymer 3D structures for wearable energy harvesters

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    Wearable devices have emerged as one of the most rapidly growing branches of the consumer electronics industry in recent years. Having a wide breadth of applications, ranging from leisure and fitness tracking to therapeutics and diagnostics, their development has become a critical driving force in the field of personalised medicine and point-of-care technologies. With the availability of more powerful processing techniques, efficient design approaches, and the miniaturisation of the basic building blocks that conform them, the capabilities of wearable devices have great potential for growth. Energy sources are one of the critical challenges associated with the design of wearable electronics. Renewable sources such as piezoelectric energy harvesters are of great interest, offering a viable alternative that can help tackle the problem of e-waste by enhancing the lifespan of a primary power source or as an independent power source. The piezoelectric active core materials of energy harvesters are the elements that allow for the conversion of mechanical energy to electrical energy. Contrary to the case of using piezoelectric ceramics, polymer based active cores offer superior flexibility, low manufacturing costs, and are non-toxic. However, their piezoelectric properties are comparatively lower than those of ceramics. Micro and nanofabrication methods for the manufacture of polymer based piezoelectric structures are of great interest in the field of energy harvesting because they allow for the tuning of specific morphological properties of these materials, offering the possibility of tailoring the material to the intended application and for the enhancement of the piezoelectric properties of the manufactured structures in some cases, which can bring the piezoelectric performance of polymer based materials closer to that of ceramics Electrospinning is a technique for the fabrication of nano and microfibrous structures based on the principles of electrohydrodynamics. This versatile manufacturing method not only allows for the fabrication of diverse morphologies of a material depending on the working parameters, ambient conditions and reagents, but can also intrinsically enhance the properties of the product. In this thesis, electrospinning will be used for the fabrication of polymer based piezoelectric materials. The work presented in the following chapters will focus firstly on the optimisation of the working parameters and on the composition of the polymer solutions for the fabrication of morphologically stable fibres and consequently will deal with improving the electrical response of these structures when they are used as the active core of a piezoelectric generator. Initial experimental work deals with the optimisation of polymer solutions containing the ferroelectric polymer poly(vinylidene fluoride) (PVDF). Favourable conditions for the fabrication of PVDF nanofibres were identified, and the resulting 2D fibrous mats were used for assembling a first iteration of piezoelectric generators. The findings indicated that the electrospun PVDF product had a favourable electrical response in spite of the morphology of the fibrous product not being ideal. Thus, improving the quality of the electrospun products would certainly allow for the fabrication of better performing generators. The use of chemical additives, solvent systems, and the combination of polymers for electrospinning can heavily influence the quality of the product. This thesis proceeds with the exploration of this premise, using combinations of PVDF with poly(ethylene oxide) (PEO) and lithium chloride (LiCl) for improving the quality of the material. Fibre morphology improved dramatically with the use of these additives, and it was observed that the fabricated fibrous structures could now transition to 3D materials under specific conditions, with variants ranging from a cloud-like structure to thick sponge-like fibrous mats. The conditions required for the production of 3D structures were found to be compatible with poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE), a copolymer known to have intrinsically superior piezoelectric properties than PVDF. The fabricated structures were used for assembling piezoelectric generators, and their electrical properties were shown to be comparable or to outperform similar state-of-the-art devices. Design opportunities were identified while working on the proposed piezoelectric generator architecture and the interfacing methods used for bonding the active core to the electrode materials. The thesis finalises with an exploration of additional methods that can be used to further increase the electrical response of generators with thick sponge-like fibrous PVDF-TrFE/PEO active cores. The findings of this final study revealed that electrode placement and design that conforms to the characteristics of the electrospun fibrous core and the use of electrode materials that can interface with both the surface of the active core and the fibrous network within the core material can improve the electrical output of the generators dramatically. The multidisciplinary work presented in this thesis explored fields ranging from chemistry and materials science to electronics and electrical engineering, laying the ground work upon which new research opportunities for the development of portable renewable energy sources can develop

    Smart Materials and Devices for Energy Harvesting

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    This book is devoted to energy harvesting from smart materials and devices. It focusses on the latest available techniques recently published by researchers all over the world. Energy Harvesting allows otherwise wasted environmental energy to be converted into electric energy, such as vibrations, wind and solar energy. It is a common experience that the limiting factor for wearable electronics, such as smartphones or wearable bands, or for wireless sensors in harsh environments, is the finite energy stored in onboard batteries. Therefore, the answer to the battery “charge or change” issue is energy harvesting because it converts the energy in the precise location where it is needed. In order to achieve this, suitable smart materials are needed, such as piezoelectrics or magnetostrictives. Moreover, energy harvesting may also be exploited for other crucial applications, such as for the powering of implantable medical/sensing devices for humans and animals. Therefore, energy harvesting from smart materials will become increasingly important in the future. This book provides a broad perspective on this topic for researchers and readers with both physics and engineering backgrounds

    Advanced Sensors for Real-Time Monitoring Applications

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    It is impossible to imagine the modern world without sensors, or without real-time information about almost everything—from local temperature to material composition and health parameters. We sense, measure, and process data and act accordingly all the time. In fact, real-time monitoring and information is key to a successful business, an assistant in life-saving decisions that healthcare professionals make, and a tool in research that could revolutionize the future. To ensure that sensors address the rapidly developing needs of various areas of our lives and activities, scientists, researchers, manufacturers, and end-users have established an efficient dialogue so that the newest technological achievements in all aspects of real-time sensing can be implemented for the benefit of the wider community. This book documents some of the results of such a dialogue and reports on advances in sensors and sensor systems for existing and emerging real-time monitoring applications
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