Sub 1V Charge Pump based Micro Scale Energy Harvesting for Low Power Application

Harvesting energy from our environment is a promising solution to provide power to wireless sensor network, wearable devices and biomedical implantation. Now a days, usage of battery power system has disappeared because of replacement issues, installation costs every periodic year and the possibility of health hazard in the case of biomedical implants. Considering these issues, energy harvesting proves to be the most feasible and convenient option in the case of wearable devices and biomedical implantation. Hence, we have focused on indoor single solar cell energy harvesting to power ultra-low power load. The tree topology DC-DC converter is used for power management circuit with optimized efficiency. High efficiency is achieved by using ZVT MOSCAP. The power management circuit includes DC-DC converter and feed forward maximum power point tracking algorithm to transfer maximum power from the single solar cell. The system has ultra-low power battery protection and input condition sensor circuit to extend the life of the battery by protecting from overcharging and over discharging. Also, cold start up circuit is used to run the system when battery voltage drains out to zero. The objective of this system to make complete energy harvester unit is to drive wide range of ultra-low power applications. We have driven the ZigBee receiver to validate our system and the system works effectively

Power Management Circuits for Energy Harvesting Applications

Energy harvesting is the process of converting ambient available energy into usable electrical energy. Multiple types of sources are can be used to harness environmental energy: solar cells, kinetic transducers, thermal energy, and electromagnetic waves. This dissertation proposal focuses on the design of high efficiency, ultra-low power, power management units for DC energy harvesting sources. New architectures and design techniques are introduced to achieve high efficiency and performance while achieving maximum power extraction from the sources. The first part of the dissertation focuses on the application of inductive switching regulators and their use in energy harvesting applications. The second implements capacitive switching regulators to minimize the use of external components and present a minimal footprint solution for energy harvesting power management. Analysis and theoretical background for all switching regulators and linear regulators are described in detail. Both solutions demonstrate how low power, high efficiency design allows for a self-sustaining, operational device which can tackle the two main concerns for energy harvesting: maximum power extraction and voltage regulation. Furthermore, a practical demonstration with an Internet of Things type node is tested and positive results shown by a fully powered device from harvested energy. All systems were designed, implemented and tested to demonstrate proof-of-concept prototypes

Design and Fabrication of Bond Wire Micro-Magnetics

This thesis presents a new approach for the design and fabrication of bond wire magnetics for power converter applications by using standard IC gold bonding wires and micro-machined magnetic cores. It shows a systematic design and characterization study for bond wire transformers with toroidal and race-track cores for both PCB and silicon substrates. Measurement results show that the use of ferrite cores increases the secondary self-inductance up to 315 µH with a Q-factor up to 24.5 at 100 kHz. Measurement results on LTCC core report an enhancement of the secondary self-inductance up to 23 µH with a Q-factor up to 10.5 at 1.4 MHz. A resonant DC-DC converter is designed in 0.32 µm BCD6s technology at STMicroelectronics with a depletion nmosfet and a bond wire micro-transformer for EH applications. Measures report that the circuit begins to oscillate from a TEG voltage of 280 mV while starts to convert from an input down to 330 mV to a rectified output of 0.8 V at an input of 400 mV. Bond wire magnetics is a cost-effective approach that enables a flexible design of inductors and transformers with high inductance and high turns ratio. Additionally, it supports the development of magnetics on top of the IC active circuitry for package and wafer level integrations, thus enabling the design of high density power components. This makes possible the evolution of PwrSiP and PwrSoC with reliable highly efficient magnetics

Contribution to modeling and realization of ultralow voltage oscillators with application to energy harvesting

Orientadores: José Antenor Pomilio, Saulo FincoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Sistemas autônomos como dispositivos implantáveis, redes de sensores sem fio e sistemas embarcados requerem uma fonte de energia usualmente na forma de bateria ou supercapacitor. A miniaturização e a redução do consumo de potência em dispositivos eletrônicos modernos permite o uso de fontes alternativas como forma de estender a vida útil destes sistemas. A energia pode ser fornecida pelo ambiente, na forma de luz solar, vibração, calor ou ondas eletromagnéticas. O processo de captação e adequação desta energia é chamado de extração ou coleta de energia. O desenvolvimento de sistemas de extração de energia envolve desafios. Algumas fontes fornecem apenas dezenas de milivolts ou nanoamperes. Uma abordagem para extrair energia de fontes de baixa tensão é o projeto de osciladores que possam operar nestas condições. Esta área do conhecimento vem sendo objeto de intensa pesquisa. Várias estratégias são utilizadas, e sistemas operando com até 3,5 mV são descritos. Há, contudo um compromisso entre mínima tensão de operação, capacidade de potência e volume/complexidade. O comportamento de osciladores em tensão ultrabaixa é altamente não-linear e dependente dos parâmetros dos dispositivos e condições de operação. Técnicas convencionais são inadequadas para a análise destes circuitos em situação tão extrema. A impossibilidade de prever com precisão aceitável parâmetros como excursão de tensão e frequência de oscilação e a falta de compreensão mais profunda do mecanismo de funcionamento tornam difícil a especificação dos blocos seguintes ao oscilador no sistema de extração de energia. Este trabalho propõe a aplicação do oscilador com acoplamento nas portas como um módulo de extração de energia de tensão ultrabaixa. O comportamento do circuito é tipicamente como multivibrador astável e uma modelagem utilizando a teoria de oscilações não lineares é apresentada, tanto para circuitos com transistores MOS (MOSFETs) como com transistores bipolares (BJTs). A validade do modelo é verificada através de experimentos com protótipos discretos e uma boa concordância é obtida entre a teoria e a prática. A topologia necessita de uma tensão nas bases dos BJTs ou portas de MOSFETs convencionais de forma que a oscilação possa se iniciar. Um novo módulo, chamado de bloco de partida, é proposto que deriva esta tensão de polarização da fonte de alimentação, tornando o circuito independente de uma tensão preexistente. Um modelo linear para este bloco é apresentado e verificado através da caracterização de um protótipo. Experimentos com circuitos discretos utilizando o bloco de partida mostram que os osciladores podem iniciar sua operação com uma tensão única tão baixa quanto 50 mV. Os protótipos com BJTs e MOSFETs foram capazes de fornecer 173 µW e 560 µW para uma alimentação de 100 mV, respectivamente, demonstrando que a topologia pode ser uma alternativa competitiva em termos de desempenho, tensão de operação e complexidade quando comparada a outras já apresentadas na literaturaAbstract: Autonomous systems, such as implanted devices, wireless sensor networks, and embedded systems, require an energy source which is usually in the form of a battery or a supercapacitor. The miniaturization and reduction of power consumption in modern electronic devices enables the use of alternative energy sources as a way of extending the life-span of these systems. The energy can be supplied by the environment, such as sunlight, vibration, heat, or RF waves. The process of extracting and fitting this energy is usually called energy harvesting. The development of energy harvesting systems presents challenges. Some sources can only supply dozens of millivolts or nanoamperes. One approach to harvest the energy of low-voltage sources is by designing oscillators that can operate in these conditions. This knowledge area is subject of intensive research. Many approaches are proposed, and systems operating with voltages as low as 3.5 mV are described. However, there is a tradeoff between minimum operating voltage, power capacity and volume/complexity. The behavior of oscillators at ultralow voltage is very nonlinear and dependent of the device parameters and operational conditions. Conventional techniques are not able to give reasonable results in the analysis of circuits in such extreme levels. The lack of a prediction of parameters like voltage excursion and oscillation frequency with acceptable precision and a deeper understanding of the working mechanism turn difficult the specification of the blocks that follow the oscillator in the energy harvesting system. This work proposes the application of the oscillator with coupling at the gates as an ultralow voltage energy harvesting module. The behavior of the circuit is typically as astable multivibrator and a modeling using the theory of nonlinear oscillations is presented, when applying MOS transistors (MOSFETs) or bipolar junction transistors (BJTs). The validity of the models is verified through experiments with discrete prototypes and good agreement is found between theory and practice. The topology needs a voltage biasing at the bases of the BJTs or gates of the conventional MOSFETs in order it starts oscillating. A new module, called starting block, is proposed that derives this biasing voltage from the voltage source, turning the circuit independent of a preexistent voltage. A linear model for this block is presented and checked by the characterization of a prototype. Experiments with discrete prototypes with the starting block show that the oscillators can start operating with a unique source as low as 50 mV. Prototypes with BJTs and MOSFETs were able to provide 173 µW and 560 µW from a supply of 100 mV, respectively, demonstrating that the proposed topology can be a competitive option regarding performance, operating voltage and complexity when compared with those previously presentedDoutoradoEletrônica, Microeletrônica e OptoeletrônicaDoutor em Engenharia Elétric

2.45ghz Rf-front End for a Micro Neural Interface System

Active implants inside the human body must be capable of performing their intended function for decades without replacement with minimal tissue heating. It is therefore necessary for them to efficiently operate reliably in a battery free environment at very low power levels. Traditionally inductive coupling has been the preferred choice of power transfer to the active implants. Inductive coupling suffers from bandwidth and alignment issues that limit their usefulness for distributed sensor systems. The ability to use both near-field and far-field RF to power and communicate with sensors distributed in the body would provide a major advance in implantable device technology. Recent advances in wafer packaging technologies and advanced VLSI processes offer the possibility of highly reliable system on chip (SOC) solutions using RF energy as a source to power the active implants. In this paper we present a CMOS VLSI implementation of a front end system for a RFID Sensor (RFIDS) capable of harvesting up to 42�W at -3dBm power levels and providing 700mV and 400mV regulated DC voltages under 50 �A and 4�A continuous load currents respectively. In addition the RFIDS contains both an AM demodulator and a 400mV voltage reference. The RF front end chip occupies an area of 2.32 mm2 and has been fabricated in 180nm IBM CMRF7SF processSchool of Electrical & Computer Engineerin

Optimisation de la récupération d'énergie dans les applications de rectenna

Les progrès réalisés durant ces dernières années dans le domaine de la microélectronique et notamment vis-à-vis de l augmentation exponentielle de la densité d intégration des composants et des systèmes a participé activement à l apparition et au développement de systèmes portables communicants de plus en plus performants et polyvalents. La R&D dans les technologies de stockage d énergie n a pas suivi cette tendance d évolution très rapide ; ce qui constitue un handicap majeur dans les évolutions futures des systèmes portables. La transmission d énergie sans fils sur des distances considérables (plusieurs dizaines de mètres) grâce aux microondes constitue une solution très prometteuse pour pallier aux problèmes d autonomie dans le cas des systèmes sans fils communicants. De plus, du fait de l omniprésence des ondes électromagnétiques dans notre environnement avec des niveaux plus ou moins importants, la récupération et l exploitation de cette énergie libre est également possible. La rectenna (Rectifying Antenna) est le dispositif permettant de capter et de convertir une onde électromagnétique en une tension continue. Plusieurs travaux de thèse axés sur l étude et l optimisation de la rectenna ont été réalisés au sein du laboratoire. Ces travaux avaient montré que pour des faibles niveaux de champs les tensions délivrées par la rectenna sont généralement très faibles et inexploitables. Aussi, comme la majorité des micro-sources d énergie et à cause de son impédance interne, les performances de la rectenna dépendent fortement de sa charge de sortie. Ainsi, le développement d un système d interfaçage de la rectenna est nécessaire afin de pallier ces manquements inhérents du convertisseur RF/DC. Ce genre de système d interfaçage est généralement absent dans la littérature à cause des faibles niveaux de puissance exploités. Par conséquent, la rectenna est très souvent utilisée tel quelle ; ce qui limite fortement le champ applicatif. Dans ce projet de recherche, un système de gestion énergétique de la rectenna complètement autonome a été conçu, développé et optimisé afin de garantir les performances optimales de la rectenna quelques soient les fluctuations de la puissance d entrée et celles de la charge de sortie. Le circuit d interfaçage permet également de fournir à la charge des niveaux de tension utilisables. Le système réalisé est basé tout d abord sur l utilisation d un convertisseur DC/DC résonant pouvant fonctionner d une manière complètement autonome à partir de niveaux très bas de la tension et de la puissance de la source. Ce convertisseur permet donc de garantir l autonomie du système en éliminant la nécessité d une source d énergie auxiliaire. A cause de ses faibles performances énergétiques, ce convertisseur ne sera utilisé que durant la phase de démarrage. L efficacité du système en termes de rendement énergétique et d adaptation d impédance est garantie grâce à l utilisation d un convertisseur Flyback fonctionnant dans son régime de conduction discontinu. Ainsi, une adaptation d impédance très efficace est réalisée entre la rectenna et la charge de sortie. Ce convertisseur principal fonctionnera durant le régime permanent. Les deux convertisseurs ont été optimisés pour des niveaux de tension et de puissance aussi bas que quelques centaines de mV et quelques W respectivement. Des mesures expérimentales réalisées sur plusieurs prototypes ont démontré le bon fonctionnement et les excellentes performances prédites par la procédure de conception ; ce qui nous permet de valider notre approche. De plus, les performances obtenues se distinguent parfaitement vis-à-vis de l état de l art. Enfin, en fonction de l application désirée, plusieurs synoptiques d association des deux structures sont proposés. Ceci inclut également la gestion énergétique de la charge de sortie.Latest advancements in microelectronic technologies and especially with the exponential increase of components and devices integration density have yield novel high technology and polyvalent portable systems. Such polyvalent communication devices need more and more available energy. Nonetheless, research in energy storage technology did not evolve with a similar speed. This constitutes a substantial handicap for the future evolution of portable devices. Wireless energy transfer through large distances such as tens of meters using microwaves is a very promising solution in order to deal with the autonomy problem in portable devices. In addition, since electromagnetic waves are ubiquitous in our environment, harvesting and using this free and available energy is also possible. Rectenna (Rectifying Antenna) is the device that allows to collect and to convert an electromagnetic wave into DC power. Several thesis research projects focusing on studying and optimizing the rectenna was carried-out into the Ampere laboratory. It has been shown that for a low level of the electromagnetic field the voltage provided by the rectenna is ultra-low and thus impractical. Further, as it is the case for the majority of energy harvesting micro-sources, the performances of the rectenna depend highly with the loading conditions. So, the development of an interfacing circuit for the rectenna is a necessary task in order to relieve the RF/DC converter inherent flaws. As it is pointed out into the literature, such power management circuit is in most cases absent due to the ultra-low power levels. In most cases, the rectenna is used as it; which reduces strongly the applications area. Within this research project, an ultra-low power and fully-autonomous power management system dedicated to rectennas was developed and optimized. It allows to guarantee highest performances of the rectenna whatever are the fluctuation of the input power level and the output load conditions. In addition, this power management system allows to provide a conventional voltage level to the load. The first part of the developed system is composed by a resonant DC/DC converter which plays the role of start-up circuit. In this case, no external energy source is required even with low voltage and ultra-low power source conditions. Because of its general poor energetic performances, this resonant converter will be used only during the start-up phase. The second part of the developed system is composed by a Flyback converter operating in its discontinuous conduction mode. Using this mode, the converter realizes static and very effective impedance matching with the rectenna in order to extract the maximum available power whatever are the input and the output conditions. Furthermore, thanks to the optimization procedure, the converter shows excellent efficiency performances even for W power levels based on a discrete demonstrator. Finally, the converter provides conventional voltage levels allowing to power standard electronics. Experimental tests based on discrete prototypes for the both converters show distinguish results for the start-up voltage, the impedance matching effectiveness and the efficiency as regard to the state of the art. 6LYON-Ecole Centrale (690812301) / SudocSudocFranceF

Modeliranje efikasnosti minijaturnih termoelektričnih modula

The research includes the development of a transient thermo-electric SPICE compatible model of the Wireless Sensor Network (WSN) node with aluminum core printed circuit boards. The model enables the characterization of commercial miniature thermoelectric modules (TEMs) within the node in terms of efficiency, cold boot time, dimensions and compactness of the system, as well as the minimum and maximum temperatures of application. The criteria for selecting the geometry and material of the heatsinks optimal to use with different TEMs as parts of thermoelectric systems are set. The design and optimization of voltage booster circuits for use in energy harvesting systems are presented. The analysis is based on simulations using LTspice software, numerical multiphysics simulations, and experimental measurements

A 120mV startup circuit based on charge pump for energy harvesting circuits

In this paper, a 120mV input startup circuit based on novel charge pump architecture is proposed. The startup circuit can boost input voltages ranging from 120mV to 300mV while supplying voltages 280mV to 1.6V at the output with approximately 23% efficiency. To verify the circuit behavior, the test circuit has been implemented using 0.18µm CMOS process. The low voltage, low area startup circuit is suitable for ultra low voltage applications such as energy harvesters and allows for single chip integration