Efficient RF-to-DC Converters for Biomedical Implantable Devices

The power management section associated with the biomedical circuit is very crucial and should be optimally designed for optimal utilization of power. This work discusses the different power shaping or conversion circuits that had been taken for their performance analysis. The two-performance metrics power conversion efficiency and susceptibility against the wireless power transfer have been taken to investigate the operational performance of the biomedical circuits against the input signal strength and operating frequencies. Simulated results confirm the CNFET-based circuit performance is very good at a small value of input voltage 0.6V and a broad range of operating frequency (953 MHz). Therefore, a CNFET-based circuit can be used suitably in implantable devices with optimum power utilization and a remote powering mechanism over the RF link

Transmission d'énergie sans fil pour les implants biomédicaux

Au cours des dernières années, le progrès des dispositifs électroniques implantables alimentés par des technologies sans fil a évolué continuellement et le besoin d'une alimentation sans fil et durable devient nécessaire pour le développement de ces appareils. La transmission d'énergie sans fil est l'une des technologies clés ayant été utilisée dernièrement pour alimenter les implants biomédicaux. Elle a été en effet l'objet des recherches scientifiques pour le traitement des maladies chroniques. La recherche en neuroscience est l'une des applications où le transfert d'énergie sans fil a amélioré la performance des implants neuronaux et a participé à la réduction de la taille, la complexité et à la consommation d'énergie de ces dispositifs. Ces implants ne peuvent pas utiliser de grosses batteries en raison de l'espace limité et pour éviter le risque associé à la chirurgie invasive pouvant également changer les résultats des expériences. Cette thèse présente le développement d'un système de transmission d'énergie sans fil par couplage inductif pour l'alimentation d'une interface d'enregistrement neuronal. Le système réalisé évite d'utiliser des grosses batteries ou câbles pour fournir l'énergie à ces interfaces et augmente la durée de vie des batteries implantables afin d'effectuer des opérations électrophysiologiques sur les animaux vivants à long terme. Cette base aidera les médecins et neuroscientifiques à suivre le comportement de ces animaux en mouvement libre et pendant une longue période de temps et en tout sécurité. La plateforme sans fil développée utilise une cage énergétique afin d'effectuer ces opérations et dans le but de distribuer la puissance dans plusieurs positions en fonction des déplacements et les mouvements effectués par des animaux des tests à l'intérieur de la cage. Le travail réalisé dans ce mémoire fournit de nouvelles stratégies pour la conception optimale des systèmes d'alimentations sans fil avec des améliorations et de forts résultats expérimentaux. Il comprend en outre le développement de quatre systèmes. Tout d'abord, l'architecture de chaque système sera présentée d'une manière ingénieuse. Par la suite, les performances du système pour des tests expérimentaux seront expliqués. Les résultats de ces tests seront bien sûr interprétés tout en comparant avec des systèmes existants. Une validation de ces résultats sera finalement effectuée avec des animaux vivants pour tester la fonctionnalité de la plateforme dans un cadre réel.In recent years, the progress of implantable electronic devices powered by wireless technologies has evolved continuously and the need for wireless and sustainable power becomes necessary for the development of these devices. The transmission of energy without wire is one of the key technologies used lately to power biomedical implants and which has been the subject of scientific research for the treatment of several diseases such as chronic diseases. Research in neuroscience is indeed one of the applications where wireless energy transfer has improved the performance of neural implants and participated in reducing the size, complexity, and power consumption of these devices. Since these implants cannot use large batteries due to the limited space of these implants and to avoid the risk associated with the surgery, the change of the folds which can also change the results of experiment. In this thesis, a wireless energy transmission system by inductive coupling is presented, this system is used to power a neural interface. Which has made it possible to avoid the use of large batteries or cables to provide energy to these interfaces and which has increase the lifespan of implantable batteries in order to perform electrophysiological operations on living animals and in the long term, this will help physicians and neuroscientists to follow the behavior of these animals in free movement and during a long period of time and in complete safety. The developed wireless platform uses an energy cage to perform these operations and to distribute the power in several positions according to the displacements and the movements carried out by the animals of the tests inside the cage. The work carried out in this thesis provides new strategies for the optimal design of wireless power systems, with innovations and strong experimental results. It also includes the development of four systems with innovations. Firstly, the architecture of each system will be genuinely presented. Furthermore, the performance of the system for testing of the experimental will be explained. The results of these tests will be indeed interpreted in comparison with existing systems. A validation of these results will be finally performed with live animals to test the functionality of the platform in a real setting

Circuits and systems for inductive power transfer

Recently, the development of Wireless Power Transfer (WPT) systems has shown to be a key factor for improving the robustness, usability and autonomy of many mobile devices. The WPT link relaxes the trade-off between the battery size and the power availability, enabling highly innovative applications. This thesis aims to develop novel techniques to increase efficiency and operating distance of inductive power transfer systems. We addressed the design of the inductive link and various circuits used in the receiver. Moreover, we performed a careful system-level analysis, taking into account the design of different blocks and their interaction. The analysis is oriented towards the development of low power applications, such as Active Implantable Medical Device (AIMD) or Radio-Frequency Identification (RFID) systems. Three main approaches were considered to increase efficiency and operating distance: 1) The use of additional resonant coils, placed between the transmitter and the receiver. 2) The receiver coil impedance matching. 3) The design of high-efficiency rectifiers and dc-dc converters. The effect of the additional coils in the inductive link is usually studied without considering its influence on other parts of the WPT system. In this work, we theoretically analyzed and compared 2 and 3-coil links, showing the advantages of using the additional coil together with a matching network in the receiver. The effect of the additional coils in a closed-loop regulated system is also addressed, demonstrating that the feedback-loop design should consider the number of coils used in the link. Furthermore, the inclusion of one additional resonant coil in an actual half-duplex RFID system at 134:2 kHz is presented. The maximum efficiency point can be achieved by adjusting the receiver coil load impedance in order to reach its optimum value. In inductive powering, this optimum impedance is often achieved by adapting the input impedance of a dc-dc converter in the receiver. A matching network can also be used for the same purpose, as have been analyzed in previous works. In this thesis, we propose a joint design using both, matching network and dc-dc converters, highlighting the benefits of using the combined approach. A rectifier must be included in any WPT receiver. Usually, a dc-dc converter is included after the rectifier to adjust the output voltage or control the rectifier load impedance. The efficiency of both, rectifier and dc-dc converter, impacts not only the load power but also the receiver dissipation. In applications such as AIMDs, to get the most amount of power with low dissipation is crucial to full safety requirements. We present the design of an active rectifier and a switched capacitor dc-dc converter. In low-power applications, the power consumption of any auxiliary block used in the circuit may decrease the efficiency due to its quiescent consumption. Therefore, we have carefully designed these auxiliary blocks, such as operational transconductance amplifiers and voltage comparators. The main contributions of this thesis are: . Deduction of simplified equations to compare 2 and 3-coil links with an optimized Matching Network (MN). . Development of a 3-coil link half-duplex RFID 134.2 kHz system. . Analysis of the influence of the titanium case in the inductive link of implantable medical devices. . Development of a joint design ow which exploits the advantages of using both MNs and dc-dc converters in the receiver to achieve load impedance matching. . Analysis of closed-loop postregulated systems, highlighting the effects that the additional coils, receiver resonance (series or parallel), and type of driver (voltage or current) used in the transmitter, have in the feedback control loop. . Proposal of systematic analysis and design of charge recycling switches in step-up dc-dc converters. . New architecture for low-power high slew-rate operational transconductance amplifier. Novel architecture for high-efficiency active rectifier. The thesis is essentially based on the publications [1{9]. During the PhD program, other publications were generated [10{15] that are partially or non-included in the thesis. Additionally, some contributions presented in the text, are in process of publication.Hace ya un buen tiempo que las redes inalámbricas constituyen uno de los temas de investigación más estudiados en el área de las telecomunicaciones. Actualmente un gran porcentaje de los esfuerzos de la comunidad científifica y del sector industrial están concentrados en la definición de los requerimientos y estándares de la quinta generación de redes móviles. 5G implicará la integración y adaptación de varias tecnologías, no solo del campo de las telecomunicaciones sino también de la informática y del análisis de datos, con el objetivo de lograr una red lo suficientemente flexible y escalable como para satisfacer los requerimientos para la enorme variedad de casos de uso implicados en el desarrollo de la “sociedad conectada”. Un problema que se presenta en las redes inalámbricas actuales, que por lo tanto genera un desafío más que interesante para lo que se viene, es la escasez de espectro radioeléctrico para poder asignar bandas a nuevas tecnologías y nuevos servicios. El espectro está sobreasignado a los diferentes servicios de telecomunicaciones existentes y las bandas de uso libre o no licenciadas están cada vez más saturadas de equipos que trabajan en ellas (basta pensar lo que sucede en la banda no licenciada de 2.4 GHz). Sin embargo, existen análisis y mediciones que muestran que en diversas zonas y en diversas escalas de tiempo, el espectro radioeléctrico, si bien está formalmente asignado a algún servicio, no se utiliza plenamente existiendo tiempos durante los cuales ciertas bandas están libres y potencialmente podrían ser usadas. Esto ha llevado a que las Redes Radios Cognitivas, concepto que existe desde hace un tiempo, sean consideradas uno de los pilares para el desarrollo de las redes inalámbricas del futuro. En los ultimos años la transferencia inalámbrica de energía (WPT) ha cobrado especial atención, ya que logra aumentar la robustez, usabilidad y autonomía de los dispositivos móviles. Transferir energía inalámbricamente relaja el compromiso entre el tamaño de la batería y la disponibilidad de energía, permitiendo aplicaciones que de otro modo no serían posibles. Esta tesis tiene como objetivo desarrollar técnicas novedosas para aumentar la eficiencia y la distancia de transmisión de sistemas de transferencia inalámbrica por acople inductivo (IPT). Se abordó el diseño del enlace inductivo y varios circuitos utilizados en el receptor de energía. Además, realizamos un cuidadoso análisis a nivel sistema, teniendo en cuenta el diseño conjunto de diferentes bloques. Todo el trabajo está orientado hacia el desarrollo de aplicaciones de bajo consumo, como dispositivos médicos implantables activos (AIMD) o sistemas de identificación por radio frecuencia (RFID). Se consideraron principalmente tres enfoques para lograr mayor eficienciay distancia: 1) El uso de bobinas resonantes adicionales, colocadas entre el transmisor y el receptor. 2) El uso de redes de adaptación de impedancia en el receptor. 3) El diseño de circuitos rectificdores y conversores dc-dc con alta eficiencia.El efecto ocasionado por las bobinas resonantes adicionales en el enlace inductivo es usualmente abordado sin tener en cuenta su influenciaen todas las partes del sistema. En este trabajo, analizamos teóricamente y comparamos sistemas de 2 y 3 bobinas, mostrando las ventajas que tiene la bobina adicional en conjunto con el uso de redes de adaptación. El efecto de dicha bobina, en sistemas de lazo cerrado fue también estudiado, demostrando que el diseño del lazo debe considerar el número de bobinas que utiliza el link. Se trabajó con un sistema real de RFID, analizando el uso de una bobina resonante en una aplicación práctica existente y de amplio uso en el Uruguay