Modern switch-mode power supplies (SMPS) used for point-of-load (PoL) applications need to meet increasingly stringent requirements on voltage regulation, while minimizing physical volume and optimizing conversion efficiency. The focus of this thesis is the voltage regulation capability of low-power PoL converters during load transients. The main objective is to investigate converter topologies and control techniques that can achieve fast and smooth transient performance without significant penalty in volume and efficiency. The digital control method is used due to its ability to implement sophisticated control algorithms. The first part of this thesis investigates a dual output stages converter, with a small auxiliary output stage connected in parallel with the main output stage. While the main output stage is responsible for steady-state operation and designed to achieve optimum efficiency, the auxiliary stage is activated when a load transient occurs, to help suppress voltage deviation. Experimental results on a 6 V-to-1 V, 3W buck converter shows 35% improvement in peak transient voltage deviation while maintaining the same efficiency profile, compared to an equivalent buck converter. The second part of this thesis introduces a flyback-transformer based buck (FTBB) converter. In this topology, the conventional buck inductor is replaced with the primary winding of the flyback transformer, an extra switch, and a set of small auxiliary switches on the secondary side. During heavy-to-light load transients the inductor current is steered away from the output capacitor to the input port, achieving both energy recycling and savings due to reduced voltage overshoots. The light-to-heavy transient response is improved by reducing the equivalent inductance of the primary transformer winding to its leakage value. Compared to an equivalent buck converter, experiment results on a 6 V-to-1 V, 3 W prototype show three times smaller maximum output voltage deviation during load transients and, for frequently changing loads, about 7% decrease in power losses.

Modern switch-mode power supplies (SMPS) used for point-of-load (PoL) applications need to meet increasingly stringent requirements on voltage regulation, while minimizing physical volume and optimizing conversion efficiency. The focus of this thesis is the voltage regulation capability of low-power PoL converters during load transients. The main objective is to investigate converter topologies and control techniques that can achieve fast and smooth transient performance without significant penalty in volume and efficiency. The digital control method is used due to its ability to implement sophisticated control algorithms. The first part of this thesis investigates a dual output stages converter, with a small auxiliary output stage connected in parallel with the main output stage. While the main output stage is responsible for steady-state operation and designed to achieve optimum efficiency, the auxiliary stage is activated when a load transient occurs, to help suppress voltage deviation. Experimental results on a 6 V-to-1 V, 3W buck converter shows 35% improvement in peak transient voltage deviation while maintaining the same efficiency profile, compared to an equivalent buck converter. The second part of this thesis introduces a flyback-transformer based buck (FTBB) converter. In this topology, the conventional buck inductor is replaced with the primary winding of the flyback transformer, an extra switch, and a set of small auxiliary switches on the secondary side. During heavy-to-light load transients the inductor current is steered away from the output capacitor to the input port, achieving both energy recycling and savings due to reduced voltage overshoots. The light-to-heavy transient response is improved by reducing the equivalent inductance of the primary transformer winding to its leakage value. Compared to an equivalent buck converter, experiment results on a 6 V-to-1 V, 3 W prototype show three times smaller maximum output voltage deviation during load transients and, for frequently changing loads, about 7% decrease in power losses.

Thesis (M.S.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 85-91)

[pt] Este trabalho apresenta uma solução para o problema de posicionamento automático preciso de um corpo em um plano horizontal, atendendo à restrição de não gerar campo magnético significativo junto ao objeto a ser posicionado. A motivação do trabalho reside na necessidade, por parte do Laboratório de Supercondutividade Aplicada e Magnetismo (LSAM) do Departamento de Física, de um posicionador para experimentação em magnetocardiografia. Inicialmente são discutidas as tecnologias de automação aplicáveis ao problema, justificando-se a opção por um sistema pneumático de atuação. O sistema posicionar montado é então descrito em profundidade, abordando-se os aspectos relacionados à geometria do problema em questão, materiais, montagens mecânicas e o sistema de controle digital. A seguir é apresentada uma abordagem matemática para o problema de controle de posição em malha fechada, visando à definição de uma lei de controle aplicável ao caso em estudo. Alguns resultados analíticos são obtidos para controle de sistema caracterizados por atrito Coulombiano, ao mesmo tempo em que se desenvolve um modelo para simulação numérica da dinâmica de movimento do posicionador. Com base nestas duas ferramentas, é apresentada uma discussão sobre a aplicabilidade dos controladores da família PID ao caso específico considerado. Por fim, resultados reais obtidos com a lei de controle proposta são comparadores aos resultados simulados, mostrando-se a validade e a utilidade do modelo teórico. / [en] This thesis presents a solution or the problem of automatic precise positioning of na object in the horizontal plane, not generating any significative magnetic field in the region close to the object to be positioned. The study presented was developed as part of an effort to fulfill a necessity for a positioning system for magnetocardiography experimentation in the Magnetism and Applied Supercondutivity Laboratory of the Departament of Physics of this University. A discussion over applicable automation option is presents, along with a justification for a choice of a pneumatic actuating system. The whole precise positioning assembly is described in detail, including subjects such as movement geometry, material, mechanical structures and the digital control system. A mathematical study of the closed of the closed loop position control problem is then developed, aiming to define a control algorithm applicable to the problem. Algebraic analysis is used to describe the influence of Coulomb friction over the equations of motion of a proportional position control system, while a model for simulations experiments of the assembly´s positioning dynamics is developed. These tools are used as the basis for a discussion over the applicability of the PID controlers in the case in study. Moreover, the behavior of the proposed algorithm is recorded and compared to the results of the simulations, showing the correctness and the utility of the theoretical analysis.

Made available in DSpace on 2014-06-11T19:22:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-21Bitstream added on 2014-06-13T20:29:10Z : No. of bitstreams: 1 melo_ga_me_ilha.pdf: 6893159 bytes, checksum: a70518b6cdac1869ab5705bc69904150 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta o desenvolvimento e implementação de um emulador para a característica estática de saída (Tensão versus Corrente) equivalente àquela de fontes de energia com células combustível. O emulador apresenta como vantagens, em relação à aquisição de uma FC, o baixo custo, o reduzido espaço físico e a flexibilidade via software para a implementação de diversas características baseadas em diferentes tipos de células combustível. Neste sentido, o emulador proposto permite a realização de ensaios preliminares durante a fase de projeto e os testes dinâmicos dos subsistemas de condicionamento de energia, sem a necessidade do acoplamento com o sistema de geração à células combustível, reduzindo-se os custos associados a estes testes laboratoriais. O emulador proposto consiste em um conversor Buck isolado Full-Bridge, com potência de saída de 2kW e alimentação via barramento de 400VCC, permitindo a emulação da característica nominal de saída de um conjunto de células tipo PEM (Proton Exchange Membrane - Membrana de Troca Protônica), em uma faixa de tensão de saída variando entre 32VCC e 72VCC, dependendo da corrente drenada pela carga. O circuito principal de controle é realizado através... / This work presents a design and implementation of an emulator to the static output characteristic (Voltage versus Current) that is similar to Fuel Cell generators. There are many advantages on using the Fuel Cell emulator. The emulator is cheaper, smaller and more flexible than the real Fuel Cell systems, because it is possible to emulate different characteristics through the use of a computer. In this context, a Fuel Cell emulator is proposed in this work in order to allow laboratory testes in the power conditioning system during its design and development stage. The proposed emulator is an insulated Full-Bridge converter with Buck operation, 2kW output power and 400VCC input voltage. This emulator achieves the output characteristic of a PEM (Proton Exchange Membrane) Fuel Cell stack with output voltage range of 32VCC to 72VCC, depending on the output current. The main control circuit is based on FPGA (Field Programmable Gate Array) and VHDL (Very High Speed Integrated Circuit Hardware Description Language) language. The experimental results demonstrate that the proposed emulator achieves the output static characteristic of the PEMFC Fuel Cell System and this output characteristic can be easily modified in order to obtain another desirable static... (Complete abstract click electronic access below)

Thesis MTech(Electrical Engineering)--Cape Technikon, Cape Town, 1996 / The development of the 8051 Evaluation and Training Board was in response to fulfill a need to have a training board available for students at the start of a micro-controller course. This board must be used to get hands-on experience in the internal architecture, programming and operation of the controller through the testing of sample programs and exercises. It can act as an example of a practical micro-controller application board, and also as part of, or as an aid in the design and application of own projects. The board had to be cheap enough so that each student can be issued with a personal board for the duration of the course. It had to be adequately selfsufficient to be portable and to operate independent of a host PC. In addition, it had to contain adequate "intelligence" to guide the student in the use of the board: have a quick re-programming turn-around cycle; and it must be possible to use the board for user program testing and debugging. After drawing up an initial set of objectives and investigating the economic viability of similar systems in industry, an outline of the required design was made. This included the selection of suitable communication between the onboard Operating System and a user; the easiest way to load user programs into the board memory; and methods to test and debug this program. All the normal support circuitry required by a micro-controller to accommodate a minimum system for operation was included into a single Field Programmable Gate Array. The execution of the project was therefore divided into three distinct sections, the hardware, the firmware (Programmable Array configuration) and the software. In the design, the harmony between these sections had to be consolidated to yield a successful final product. The simplicity and ergonomics of the operation and application from a user's point of view, had to be accentuated and kept in mind throughout. In a design of the complexity such as this, careful planning and the investigation of various methods of approach were essential. The use of many computer-aided design and other relevant computer packages was incorporated. Interaction between the user and the Operating System on the board was done through a standard 16-character by 1-line LCD Display Module and a 32-key keyboard. The main feature of the Operating System was to enable the inspection and editing of all the memory locations on the micro-processor.

Thesis (MTech (Electrical Engineering)--Cape Peninsula University of Technology, 2011 / Modern technologies have led to extensive digital music reproduction and distribution. It is fitting then that digital audio be amplified directly from its source rather than being converted to an analogue waveform before amplification. The benefits of using a digital controller for audio processing include being able to easily reconfigure the system and to add additional functions at a later stage. Digital audio is primarily stored as Pulse Code Modulation (PCM) while Pulse Width Modulation (PWM) is the most popular scheme used to drive a class-D amplifier. The class-D amplifier is selected in many applications due to its very high energy efficiency. Conventional PCM to PWM conversion is inherently nonlinear. Various interpolation schemes are presented in this research project which help to address the nonlinearity. Digitally generated PWM has a limited resolution which is constrained by the system clock. This thesis presents noise shaping techniques which increase the effective resolution of the PWM process without having to use an excessively high system clock. Noise shaping allows a low resolution modulator to be used to reproduce high resolution audio.

CAPES / Este trabalho apresenta a aplicação dos métodos de otimização por enxame de partículas e por colônia de formigas na otimização dos parâmetros de um controlador não linear de estrutura variável baseado em um controlador de variância mínima generalizada. Este controlador é composto por duas parcelas distintas: uma parcela linear e outra não linear. A parcela não linear do controlador apresenta dois parâmetros que afeta diretamente o comportamento do controlador e tais parâmetros são obtidos de maneira empírica. As metaheurísticas foram aplicadas para se obter os valores otimizados destes parâmetros. Foi considerada uma função custo que leva em consideração o erro de rastreamento e a variação da ação de controle. Um exemplo numérico do projeto deste controlador também é apresentado. O controlador otimizado foi experimentado em três plantas reais: controle de velocidade de um servomecanismo, controle de nível e controle de vazão em uma planta didática industrial. Os resultados obtidos enfatizam a melhora do desempenho do controlador com os parâmetros otimizados. Também é apresentada a comparação do desempenho deste controlador com um controlador PI. / This work presents the application of particle swarm optimization and ant colony optimization in the parameters optimization of a non-linear controller with variable structure based on generalized minimum variance control. This controller is composed of two parts: linear and non-linear. The non-linear term of the controller consists of two parameters that directly affects the control action, and are obtained by trial and error. Metaheuristic methods were applied to find out the optimized values of these parameters. The cost function used in metaheuristic methods takes account the error and the control signal. A numerical example of the design of this controller is also presented. Three practical experiments were considered: a servomechanism velocity control and two control loops in a didactic industrial plant, level and flow control. Experimental results emphasize the improvement of the system performance when the optimization methods are applied. A comparision with PI controller is shown.

CAPES / Este trabalho apresenta a aplicação dos métodos de otimização por enxame de partículas e por colônia de formigas na otimização dos parâmetros de um controlador não linear de estrutura variável baseado em um controlador de variância mínima generalizada. Este controlador é composto por duas parcelas distintas: uma parcela linear e outra não linear. A parcela não linear do controlador apresenta dois parâmetros que afeta diretamente o comportamento do controlador e tais parâmetros são obtidos de maneira empírica. As metaheurísticas foram aplicadas para se obter os valores otimizados destes parâmetros. Foi considerada uma função custo que leva em consideração o erro de rastreamento e a variação da ação de controle. Um exemplo numérico do projeto deste controlador também é apresentado. O controlador otimizado foi experimentado em três plantas reais: controle de velocidade de um servomecanismo, controle de nível e controle de vazão em uma planta didática industrial. Os resultados obtidos enfatizam a melhora do desempenho do controlador com os parâmetros otimizados. Também é apresentada a comparação do desempenho deste controlador com um controlador PI. / This work presents the application of particle swarm optimization and ant colony optimization in the parameters optimization of a non-linear controller with variable structure based on generalized minimum variance control. This controller is composed of two parts: linear and non-linear. The non-linear term of the controller consists of two parameters that directly affects the control action, and are obtained by trial and error. Metaheuristic methods were applied to find out the optimized values of these parameters. The cost function used in metaheuristic methods takes account the error and the control signal. A numerical example of the design of this controller is also presented. Three practical experiments were considered: a servomechanism velocity control and two control loops in a didactic industrial plant, level and flow control. Experimental results emphasize the improvement of the system performance when the optimization methods are applied. A comparision with PI controller is shown.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Programmable logic devices were introduced about fifteen years ago and nowadays they are used in areas like Telecommunications, Instrumentation and more recently Power Electronics. This work presents the application of an FPGA device in the control of a ballast circuit for driving high intensity discharge lamps. The electronic ballast presents improvements regarding the previous electromagnetic reactors, due to their small size and weight and also because they guarantee a longer life time for the lamps. In order to test and verify the proposed control strategy, a prototype was built to drive 70W,150W and 250W metal halide and high pressure sodium lamps. Beyond the vantages above mentioned, the prototype also presented a notable reduction in the time needed for the lamp to achieve maximum brightness, in comparison to magnetic reactors. / Os dispositivos lógicos programáveis surgiram há cerca de quinze anos e hoje são utilizados em áreas como Telecomunicações, Instrumentação e mais recentemente em Eletrônica de Potência. Este trabalho apresenta a aplicação de um dispositivo FPGA no controle de um circuito ballast eletrônico para acionamento de lâmpadas de alta intensidade de descarga (AID). Os reatores eletrônicos apresentam sensíveis melhorias com relação aos reatores eletromagnéticos por apresentarem menor peso e volume e também por garantirem uma maior vida útil às lâmpadas. Para testar e verificar a estratégia de controle proposta, dois protótipos foram construídos para alimentar lâmpadas AID de vapor de sódio e de vapor metálico de 70W, 150W e 250W. Além das vantagens citadas anteriormente, entre os resultados apresentados pelo protótipo destaca-se a notável redução no tempo para se atingir o brilho máximo da lâmpada com relação aos reatores magnéticos. / Doutor em Ciências