High Step-Down Transformers - Single Phase Lower Single-Switch Ac / Dc Converter

Geography aligns a cellular power module (PFC) with DC / DC cell support - support and a portion of the power information is combined with the immediate return after the high power setting. By highlighting this instantaneous flow of power and sharing of capacitor voltages, the converter can achieve dynamic switching, high voltage, high power output at rated transmissions (less than 130V) and low return voltage without the low voltage converter. Changing the absence can reduce the clip and the cost of converting the number. Not at all like most PFC lifting cells, has the proposed converter only dealt with DC / DC cell induction instead of covering both inductor flows

Concepção Modular de Dispositivos Electrónicos

Ao longo deste trabalho são abordados temas relacionados com a concepção modular de dispositivos electrónicos. Esta temática tem sido alvo de diversos trabalhos de investigação a nível mundial, mas grande parte das conclusões são ainda muito dependentes do ponto de vista pessoal dos investigadores. Assim, numa primeira abordagem, são apresentadas algumas das classificações e características da concepção modular de produtos e as principais vantagens e desvantagens desta metodologia relativamente à concepção integral de produtos, isto do ponto de vista geral dos produtos e não restrito aos dispositivos electrónicos, apesar de estes serem usados regularmente nos exemplos devido à temática deste trabalho. Posteriormente é referida uma possível implementação de um dispositivo electrónico modular composto por três módulos diferentes, nomeadamente uma fonte de alimentação comutável, uma interface com o utilizador e um sistema de comunicação sem fios. Estes módulos são dimensionados e caracterizados de forma a serem algo genéricos na sua implementação, sendo igualmente destacadas temáticas de investigação relacionadas com as tecnologias utilizadas em cada um dos módulos ou os seus sistemas concorrentes. Algumas das funções possíveis dos dois últimos módulos são ainda demonstradas recorrendo a dispositivos de prototipagem rápida que incluem a plataforma mbed NXP LPC1768.Throughout this work themes related to the modular design of electronic devices are adressed. This theme has been the subject of several worldwide researches, but most of the findings are still very dependent on the personal standpoint of each researcher. In a first approach, some of the classifications and characteristics of the modular design of products and the main advantages and disadvantages of this method relative to the integral design of products are presented, although initially through a general view of products and not a view restricted to electronic devices, even though these are regularly used in the examples due to the theme of this work. Subsequently it is referred a possible implementation of a modular electronic device composed of three different modules, including a switch mode power supply, a user interface and a wireless communication system. These modules are designed and characterized in order to be something generic in its implementation and some research related with the technology in use in the modules or its competitors is presented in the correspondent chapters. Some possible functions of the last two modules are further demonstrated using rapid prototyping devices that include the mbed NXP LPC1768 platform

Novel Offline Switched Mode Power Supplies for Solid State Lighting Applications

In recent years, high brightness light emitting diodes (HBLEDs) have increasingly attracted the interest of both industrial manufacturers and academic research community. Among the several aspects that make LED technology so attractive, the most appreciated characteristics are related to their robustness, high efficiency, small size, easy dimming capability, long lifetime, very short switch-on/switch-off times and mercury free manufacturing. Even if all such qualities would seem to give to solid state lighting a clear advantage over all the other kinds of competing technologies, the issues deriving from the need of LED technology improvement, on one hand, and of the development of suitable electronic ballasts to properly drive such solid state light sources, on the other, have so far hindered the expected practical applications. The latter problem, in particular, is nowadays considered the main bottleneck in view of a widespread diffusion of solid state technology in the general lighting market, as a suitable replacement of the still dominant solutions, namely halogen and fluorescent lamps. In fact, if it is true that some aspects of the devices’ technology (e.g. temperature dependent performance, light quality, efficiency droop, high price per lumen, etc…) still need further improvements, it is now generally recognized that one of the key requirements, for a large scale spread of solid state lighting, is the optimization of the driver. In particular, the most important specifications for a LED lamp ballast are: high reliability and efficiency, high power factor, output current regulation, dimming capability, low cost and volume minimization (especially in domestic general lighting applications). From this standpoint, the main goal is, therefore, to find out simple switched mode power converter topologies, characterized by reduced component count and low current/voltage stresses, that avoid the use of short lifetime devices like electrolytic capacitors. Moreover, if compactness is a major issue, also soft switching capability becomes mandatory, in order to enable volume minimization of the reactive components by increasing the switching frequency in the range of the hundreds of kHz without significantly affecting converter’s efficiency. It is worth mentioning that, in order to optimize HBLED operation, also other matters, like the lamp thermal management concern, should be properly addressed in order to minimize the stress suffered by the light emitting devices and, consequently, the deterioration of the light quality and of the expected lamp lifetime. However, being this work focused on the issues related to the research of innovative driving solutions, the aforementioned thermal management problems, as also all the topics related to the improvement of solid state devices’ technology, will be left aside. The main goal of the work presented in this thesis is, indeed, to find out, analyze and optimize new suitable topologies, capable of matching the previously described specifications and also of successfully facing the many challenges dictated by the future of general lighting. First of all, a general overview of solid state lighting features, of the state of the art of lighting market and of the main LED driving issues will be provided. After this first introduction, the offline driving concern will be extensively discussed and different ways of approaching the problem, depending on the specific application considered, will be described. The first kind of approach investigated is based on the use of a simple structure relying on a single power conversion stage, capable of concurrently ensuring: compliance with the standards limiting the input current harmonics, regulation of the load current and also galvanic isolation. The constraints deriving from the need to fulfil the EN 61000-3-2 harmonics standard requirements, when using such kind of solution for low power (<15W) LED driving purposes, will be extensively discussed. A low cost, low component count, high switching frequency converter, based on the asymmetrical half bridge flyback topology, has been studied, developed and optimized. The simplicity and high compactness, characterizing this solution, make it a very good option for CFL and bulb replacement applications, in which volume minimization is mandatory in order to reach the goal of placing the whole driving circuitry in the standard E27 sockets. The analysis performed will be presented, together with the design procedure, the simulation outcomes and the different control and optimization techniques that were studied, implemented and tested on the converter's laboratory prototype. Another interesting approach, that will be considered, is based on the use of integrated topologies in which two different power conversion stages are merged by sharing the same power switch and control circuitry. In the resulting converter, power factor correction and LED current regulation are thus performed by two combined semi-stages in which both the input power and the output current have to be managed by the same shared switch. Compared with a conventional two-stages configuration, lower circuit complexity and cost, reduced component count and higher compactness can be achieved through integration, at cost of increased stress levels on the power switch and of losing a degree of freedom in converter design. Galvanic isolation can be provided or not depending on the topologies selected for integration. If non-isolated topologies are considered for both semi-stages, the user safety has to be guaranteed by assuring mechanical isolation throughout the LED lamp case. The issue, deriving from the need of smoothing the pulsating power absorbed from the line while avoiding the use of short lifetime electrolytic capacitors, will be addressed. A set of integrated topologies, used as HBLED lamp power supplies, will be investigated and a generalized analysis will be presented. Their input line voltage ripple attenuation capability will be examined and a general design procedure will be described. Moreover, a novel integrated solution, based on the use of a double buck converter, for an about 15W rated down-lighting application will be presented. The analysis performed, together with converter design and power factor correction concerns will be carefully discussed and the main outcomes of the tests performed at simulation level will be provided. The last kind of approach to be discussed is based on a multi-stage structure that results to be a suitable option for medium power applications, like street lighting, in which compactness is not a major concern. By adopting such kind of solution it is, indeed, possible to optimize converter’s behavior both on line and on load side, thereby guaranteeing both an effective power factor correction at the input and proper current regulation and dimming capability at the output. Galvanic isolation can be provided either by the input or the output stage, resulting in a standard two stage configuration, or by an additional intermediate isolated DC-DC stage (operating in open loop with a constant input/output voltage conversion ratio) that namely turns the AC/DC converter topology into a three stage configuration. The efficiency issue, deriving from the need of multiple energy processing along the path between the utility grid and the LED load, can be effectively addressed thanks to the high flexibility guaranteed by this structure that, relaxing the design constraint, allows to easily optimize each stage. A 150W nominal power rated ballast for street solid state lighting applications, based on the latter (three stage) topology, has been investigated. The analysis performed, the design procedure and the simulations outcomes will be carefully described, as well as the experimental results of the tests made on the implemented laboratory prototype