When multiple cold cathode fluorescent lamps (CCFLs) are set up in a backlight module, parasitic capacitances are inevitably existent between the lamps and the aluminum back-plank. These parasitic capacitances are different from each other in introducing different leakage currents, and in turn cause current imbalance between lamps with undesired unequal brightness of the backlight module. In order to tackle this current imbalance problem, it relies critically upon a balance driving scheme. This thesis adopts the impedance-matching principle for a uniform light output. A detailed analysis and design of the balance circuit is implemented in a direct-type backlight module, which employs a series resonant parallel-loaded inverter with a transformer to generate a high AC voltage to drive multiple lamps. Adding appropriate capacitors on the load resonant circuits helps alleviate the discrepancy among lamp currents. Based on the experimental results, the maximum total current deviation is defined as an index of the current imbalance for multiple lamps system. Accordingly, the minimum impedance ratio can be provided for the designers to achieve balance driving. A prototype of the multi-lamp driving circuit with balance capacitors is designed and built for a backlight module with 16 lamps in a 32-inch liquid crystal display (LCD). Simulation and experimental results demonstrate the effectiveness and feasibility of the current balance scheme.

Three novel single-stage electronic ballasts with the advantages of high-power-factor, low current harmonic, high efficiency, and low cost are proposed for rapid-start fluorescent lamps. Included are (1) single-stage high-power-factor electronic ballast with asymmetrical topology, (2) single-stage high- power-factor electronic ballast with symmetrical topology, and (3) single-stage single-switch high-power-factor electronic ballast. The circuit configurations are obtained by integrating the buck-boost power-factor-correction converter into the Class D or the Class E resonant inverter. With simple circuit configuration and less component count, desired circuit performances of high-power-factor and high efficiency are realized. The control methods of pulse-width-modulation (PWM) with asymmetrical and symmetrical approaches are utilized for the three presented ballasts. The buck-boost conversion stage is operated at discontinuous current mode (DCM) to achieve nearly unity power factor at a fixed switching frequency. With carefully designed circuit parameters, the power switches can exhibit either zero-voltage switching-on (ZVS) or zero-current switching-on (ZCS). As a result, high circuit efficiency can be ensured. Design equations are derived and computer analyses are performed based on the lamp¡¦s equivalent resistance model and fundamental approximation. Accordingly, design guidelines for determining circuit parameters are provided. Prototypes of the three proposed circuits designed for a T8-36W lamp, two series-connected T9-40W lamps and a PL-27W lamp are built and tested to verify the computer simulations and analytical predictions.

An approach with ¡§consecutive orthogonal arrays (COA)¡¨ is proposed for solving the problems in designing power electronic circuits. This approach is conceptually based on the orthogonal array method, which has been successfully implemented in quality engineering. The circuit parameters to be determined are assigned as the controlled variables of the orthogonal arrays. Incorporating with the inferential rules, the average effects of each control variable levels are used as the indices to determine the control variable levels of the subsequent orthogonal array. By manipulating on COA, circuit parameters with the desired circuit performances can be found from an effectively reduced number of numerical calculations or experimental tests. In this dissertation, the method with COA is implemented on solving four problems often encountered in the design of power electronic circuits. The first problem one has to deal with is to find a combination with the best performance from a great number of analyzed results. The illustrative example is the design of LC passive filters. Using COA method, the desired component values of the filter can be effectively and efficiently found with far fewer calculations. The second design problem arises from the non-linearity of circuit. An experienced engineer may be able to figure out circuit parameters with satisfactory performance based on their pre-knowledge on the circuit. Nevertheless, they are always questioned whether a better choice can be made. The typical case is the self-excited resonant electronic ballast with the non-linear characteristics of the saturated transformer and the power transistor storage-time. In this case, the average effects of COA obtained from experimental tests are used as the observational indexes to search a combination of circuit parameters for the desired lamp power. The third problem is that circuit functions are mutually exclusive. The designers are greatly perplexed to decide the circuit parameters, with which all functions should be met at the same time. The method with COA is applied to design a filter circuit to achieve the goals of low EMI noise and high power factor simultaneously. Finally, one has to cope with the effects of the uncontrolled variables, such as: ambient temperature, divergence among different manufacturers, and used hours. By applying COA with inferential rules, electronic ballasts can be robustly designed to operate fluorescent lamps at satisfied performance under the influence of these uncontrolled variables.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work presents the design and analysis of an electronic system with universal input to supply a fluorescent lamp. The system includes a self-oscillating electronic ballast and an additional circuit which allows keeping the nominal lamp power although a variation of the input voltage. The electronic ballast design comprises some steps: resonant filter design, self-oscillating gate driver design, additional circuit design and stability test. The electronic ballast is represented as a nonlinear control system in order to achieve a feasible design methodology. Moreover, the system must be analyzed considering the describing function method and the extended Nyquist stability criterion. The proposed electronic ballast must maintain the main characteristics of the traditional self-oscillating electronic ballast. Besides that, the additional circuit has a small number of components and it allows the input voltage full range with automatic selection of the switching frequency. The design, simulation and experimental results of the prototype are presented. / Este trabalho apresenta a análise e o projeto de um sistema eletrônico com entrada universal para alimentação de lâmpadas fluorescentes. O sistema é composto por um reator eletrônico auto-oscilante com um circuito adicional, que permite manter a potência da lâmpada no valor nominal independente da tensão de alimentação. O projeto do reator eletrônico é dividido em etapas, que compreendem o projeto do filtro ressonante, do comando auto-oscilante, do circuito adicional e a análise da oscilação auto-sustentada. Para viabilizar uma metodologia de projeto adequada, o reator eletrônico é representado como um sistema de controle. Para análise e projeto são utilizados a função descritiva e o critério de estabilidade estendido de Nyquist. O reator eletrônico mantém as principais características do reator eletrônico auto-oscilante tradicional. Além disso, o circuito adicional possui um número reduzido de componentes, o que permite empregar o reator eletrônico em qualquer rede de alimentação monofásica sem a necessidade de ajuste manual para escolha da tensão de alimentação. São apresentados resultados de simulação e experimentais do protótipo implementado.

An improved model for reducing the cost of long-term monitoring in Clean Development Mechanism (CDM) lighting retrofit projects is proposed. Cost-effective longitudinal sampling designs use the minimum number of meters required to report yearly savings at the 90% confidence and 10% relative precision level for duration of the project (up to 10 years) as stipulated by the CDM. Improvements to the existing model include a new non-linear Compact Fluorescent Lamp population decay model based on the results of the Polish Efficient Lighting Project, and a cumulative sampling function modified to weight samples exponentially by recency. An economic model altering the cost function to a nett present value calculation is also incorporated. The search space for such sampling models are investigated and found to be discontinuous and stepped, requiring a heuristic for optimisation; in this case the Genetic Algorithm was used. Assuming an exponential smoothing rate of 0.25, an inflation rate of 6.44%, and an interest rate of 10%, results show that sampling should be more evenly distributed over the study duration than is currently considered optimal, and that the proposed improvements in model accuracy increase expected project costs in nett present value terms by approximately 20%. A sensitivity analysis reveals that the expected project cost is most sensitive to the reporting precision level, coefficient of variance, and reporting / Dissertation (MEng)--University of Pretoria, 2014. / gm2014 / Electrical, Electronic and Computer Engineering / Unrestricted

The master’s thesis is devoted to exploiting of gas-discharge lamps and their dependence on frequency of the supply current. The first part describes the theory of discharge, its types and properties, terms of its origin, and ways of its exploitation. The second part concerns electrical ballast systems of gas discharge light sources, inductive (reactive) and electronic ballasts, principles of their functioning, advantages and disadvantages, and the comparison of their properties. The following chapters deal with low-pressure and high-pressure gas-discharged lamps, compare their properties and describe exploitation of fluorescent lamps. Before conducting the experiment we have described the influence of frequency of the supply current on fluorescent tube lamps. Preparations for laboratory measuring have been also implemented. During the experiment the two types of lamps have been analyzed, the results of the research are summed up in the conclusion.

This Master’s Thesis on Simulation of LED retrofits under operational conditions is divided into theoretical and practical part. Theoretical part in the introductory section deals with the concepts of lighting technology and presents some electric light sources, such as classic bulbs, halogen bulbs, linear and compact fluorescent lamps. It also describes the principle of electroluminescent light sources (LED), which discusses principles of yielding a white light, the main advantages of LED etc. The reader is familiar with the issue of compensation the linear fluorescent lamps tubular LED source and with the work environment programme ReluxPro that is used for design of the lighting system. Practical part of the thesis is divided into two chapters. In the first chapter, measured linear fluorescent lamps and LED modules for the light-technical parameters, luminous intensity, radiation spectrum and settling time of light sources are evaluated and compared. The second chapter is solved by using ReluxPro, which explores the impact on the lighting and the brightness of the room layout SA 5.10 while using various light sources. In conclusion, there is an economic aspect of linear fluorescent lamps and LED modules analyzed. Results from the program ReluxPro are continuously compared with real measured values.