The metal halide lamp has become an attractive lighting source because of its compact size, good color rendering, long lamp life, and high luminous efficacy. As a member of high-intensity discharge lamps, it has a negative incremental resistance, which claims the necessity of a ballast circuitry. Similar to other gas discharge lamps, the operating performance can be further improved when driven by a high-frequency electronic ballast. However, there are some obstacles in ballasting the metal halide lamp with the high-frequency inverter. For a cold lamp, an ignition voltage up to several kVs is required for breaking down the electrodes during starting period. The breakdown voltage and the equivalent lamp resistance may vary from time to time and lamp to lamp, and is sensitive to the used time. Furthermore, the ignition voltage for restarting a hot lamp can be ten times that for a cold lamp. On the other hand, the lamp driven by a high-frequency electronic ballast may suffer from acoustic resonance. All these make it difficult in the design of an electronic ballast, especially for the applications with hot restarting. In this dissertation, the operating characteristics for both starting transient and steady-state of the metal halide lamp are first investigated. Then, a simple method by measuring the lamp voltage is proposed to detect the happening of acoustic resonance. Based on the investigated results, several electronic ballasts are designed for driving metal halide lamps with capabilities of wide input voltage range, high input power factor, hot restarting, fast transition. In addition, an inverter circuit is configured for ballasting multiple lamps. A buck-boost power-factor-correction circuit is integrated into the load resonant inverter to achieve a high power factor, fast transition, and constant power operation. The extremely high ignition voltage for hot restarting is generated by an auxiliary ignitor. The electronic ballast is precisely operated at the specific frequency at which acoustic resonance will not occur. In addition to these features, a protection circuit is included to prevent from high voltage and/or current stresses on circuit components in case that the lamp fails to be started up or comes to the end of its life-time. For the ballast with multiple lamps, the load circuits with abnormal lamps can be isolated from the others which are under normal operation. Prototypes of the proposed circuits are built and tested. Experimental results present the satisfactory performances.

A single-stage high-power-factor electronic ballast with class E inverter is proposed for driving the fluorescent lamp. The circuit configuration is obtained from the integration of a buck-boost converter for power-factor- correction (PFC) and a class E resonant inverter for ballasting. The integrated ballast circuit requires only one active power switch and simple control. Operating the buck-boost converter in discontinuous conduction mode (DCM) at a fixed frequency, the electronic ballast can achieve nearly unity power factor. With pulse-width-modulation (PWM), the electronic ballast can provide an appropriate filament current for preheating, a high voltage for ignition, and then a desired lamp current for steady-state operation. An additional control circuit is included to eliminate the glow current during preheating stage. The operation of the ballast-lamp circuit is analyzed by fundamental approximation. Computer simulations are made and design equations are derived on basis of the power-dependent resistance model of the fluorescent lamp. With carefully designed circuit parameters, the active power switch can be switched on at zero current to reduce the switching losses leading to a higher efficiency. An experimental circuit designed for a PL-27W compact fluorescent lamp is built and tested to verify the computer simulations and analytical predictions. Experimental results show that satisfactory performances can be obtained on the proposed electronic ballast.

This thesis proposes a single-stage high-power-factor electronic ballast with series-resonant inverter for rapid-start fluorescent lamps with zero glow current during preheating period. A buck-boost converter is integrated into the ballast as the power-factor-corrector. Two auxiliary windings are wound on the same core of the buck-boost inductor for filament heating. During the preheating period, the buck-boost converter is initiated while the series-resonant inverter is disabled by controlling the corresponding active power switches. Due to zero voltage across the lamp, the glow current can be effectively eliminated. As the filaments reach appropriate emission temperature, the series-resonant inverter is activated. The lamp is then ignited and consequently operated at the rated lamp power. Circuit analyses and experimental tests of the proposed preheating control scheme are carried out on an electronic ballast for a T8-40W rapid-start fluorescent lamp.

The operating characteristics of small-wattage metal halide lamps (35W, 70W, and 150W) are investigated. Included are acoustic resonance, luminous efficacy, and electrical characteristics at steady state. A laboratory electronic ballast is built to operate metal halide lamps with square-wave currents in a frequency range from 50 Hz up to 50 kHz. The operating frequency, amplitude and dead-time can be adjusted independently. Experimental results show that the luminous efficiency decreases slightly as the operating frequency increases but deteriorates considerably as the lamp power is reduced. By examining the acoustic resonance spectra, it is found that the lamp arc instability is highly related to the dead-time of the inverter. The investigated results provide useful information for the design of the electronic ballasts.

This dissertation proposes a new starting profile with some modifications to the definition of American National Standards Institute (ANSI) to interpret the starting process of fluorescent lamps driven by high- frequency electronic ballasts. To identify the times of preheating, ignition, and steady-state, the staring transient waveforms of lamp voltages as well as the lamp currents are scrutinized from the experiments on a diversity of ballasting techniques. A glow-to-arc transition is considered to account for the stage between glow discharging and a stable lamp arc. In addition, the filament preheating is not limited to the constant voltage but can be current preheating which is more commonly used in commercial products. By the new definition, the glow current and the glow-to-arc current can be calculated to evaluate the lamp starting performance. The applicability of the starting profile is confirmed experimentally by the instant-start, preheat-start, rapid-start, modified rapid-start, and programmable rapid-start schemes.

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.

Metal halide lamp is one kind of the most compact high-performance light sources. Because of their good color rendering index and high luminous efficacy, these lamps are often preferred in locations where color and efficacy are important, such as supermarkets, gymnasiums, ice rinks and sporting arenas. Unfortunately, acoustic resonance phenomenon occurs in metal halide lamps and causes light flicker, lamp arc bending and rotation, lamp extinction and in the worst case, arc tube explosion, when the lamps are operated in high-frequency bands. This thesis takes place in the context of developing electronic ballasts with robust acoustic resonance detection and avoidance mechanisms. To this end, several envelope detection methods such as the multiplier circuit, rectifier circuit, and lock-in amplifier, are proposed to characterize fluctuations of acoustic resonance. Furthermore, statistical criteria based on the standard deviation of these fluctuations are proposed to assess acoustic resonance occurrence and classify its severity. The proposed criteria enable classifying between no acoustic resonance and acoustic resonance cases based upon either a two-dimensional plane, a histogram or a boxplot. These analyses are confirmed by the study of spectral variations (variations of the spectral irradiance and colorimetric parameters) as well. Standard deviations and relative standard deviations of these variations are also correlated with the presence of acoustic resonance. The results from this study show that whatever voltage envelope variations or spectral variations are significantly influenced by acoustic resonance phenomena. A set of metal halide lamps from different manufacturers and with different powers are tested in our experiments. We concluded that our designed multiplier and rectifier circuits for acoustic resonance detection have the same sensitivity as the lock-in amplifier, paving the way for the implementation of this function directly into the ballast circuit board.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This paper presents the development of an electronic ballast for high intensity discharge lamps, using the differential connection technique applied to Flyback converters. The power factor correction stage was implemented by a Buck-Boost converter operating in discontinuous conduction mode. Subsequently, the integrating converters technique was used to simplify the power circuit, making the power factor correction stage and Flyback converters share the same active switches. The proposed circuit was dynamically modeled, in order to obtain the mathematical parameters that govern the behavior of the ballast, obtaining the differential equations relating the voltage and current in the lamp, due to the variation of both the input voltage as the duty cycle. Digital control of the output current provided the use of a low cost microcontroller, the compensating system was designed in discrete time from the use of an integrator and a low frequency bandwidth. For effective control of lamp power, an external loop that regulates the circuit current reference was implemented. The practical implementation of the electronic ballast was performed, in order to verify the proposed control performance. / Este trabalho apresenta o desenvolvimento de um reator eletrônico para alimentar lâmpadas de descarga em alta pressão, utilizando a técnica de conexão diferencial aplicada aos conversores Flyback. A etapa de correção de fator de potencia foi implementada através de um conversor Buck-Boost operando em modo de condução descontinuo. Posteriormente, foi utilizada a técnica de integração de conversores para simplificar o circuito de potência, fazendo com que a etapa de correção do fator de potencia e os conversores Flyback compartilhassem os mesmos interruptores ativos. O circuito proposto foi modelado dinamicamente a fim de obter os parâmetros matemáticos que regem o comportamento do reator, obtendo as equações diferenciais referentes à tensão e corrente na lâmpada, em função da variação, tanto da tensão de entrada como da razão cíclica. O controle digital da corrente de saída proporcionou a utilização de um dispositivo microcontrolado de baixo custo, sendo o compensador do sistema projetado em tempo discreto a partir da utilização de um integrador e uma banda passante de baixa frequência. Para o efetivo controle da potência na lâmpada foi adicionada uma malha externa que regula a referência de corrente do circuito. Foi realizada a implementação prática do reator eletrônico a fim de verificar a performance do controle proposto.