In this thesis, a high voltage discharging testing circuit is proposed for cold cathode fluorescent lamps(CCFLs). The testing circuit uses only a single active power switch operating at a high frequency incorporating with reactive components to accumulate a relatively high voltage on the capacitor. This voltage is then stepped up by a transformer to provide the required high voltage for discharging the CCFLs. The circuit has the advantages of simple configuration, less component count, and low cost. In addition, a high power factor at the ac line source can be achieved. The proposed circuit is analyzed based on the mode operation. Accordingly, the design equations are derived to determine the circuit parameters. A prototype is designed and built for testing the 19 inch CCFLs. The discharging tests are made to recognize the malfunctions during the manufacturing process. Moreover, the distributions on the spectral power and chromaticity of lamps can be examined to ensure the product quality.

This thesis presents a single-stage high-power-factor electronic ballast for metal halide lamps. The proposed ballast integrates a buck-boost converter, a buck converter and a full-bridge inverter into a single power conversion circuit. The buck-boost converter is designed to be operated at the discontinuous conduction mode (DCM) with a constant duty ratio at a fixed switching frequency to provide a constant lamp power and to achieve a high power factor for a given ac input voltage. The full-bridge inverter supplies a square-wave current for the lamp at a low frequency the same as the line frequency to avoid acoustic resonance. For the universal input voltage ranged from 90 V to 264 V, the lamp remains at the rated power by controlling the duty-ratio of the buck converter. The circuit operation is analyzed in detail to derive the design equations. An electronic ballast for 70 W lamps is designed and tested. Computer simulations and experimental measurements are provided to verify that the proposed ballast has the merits of a nearly unity input power factor, a high efficiency greater than 82 % and can drive the lamp at a constant power.

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.

The research presents two novel high power factor ac-to-dc resonant converters with symmetrical topologies and zero-voltage-switching (ZVS) operation. The derived circuits are obtained from the integration of a dual-switch boost-type or buck-boost-type power factor corrector (PFC) into a half-bridge resonant converter. With symmetrical topology, the circuit is simple and the voltage and current stresses on the two active power switches are identical to each other. The PFC is operated at discontinuous conduction mode (DCM) to achieve unity power factor. The resonant energy tank of half-bridge resonant converter is designed to be inductive to retain ZVS operation. The design equations are derived based on fundamental approximation. Prototypes of the two proposed converters designed for 100 W and 50 W, respectively, were built and tested to verify the computer simulations and analytical predictions. Satisfactory results are obtained experimentally.

銅銻硒礦是具有 0.3 eV狹窄能帶間隙的P型半導體，且已被發現是在中溫區下極具潛力的熱電材料。銅銻硒礦的晶體結構具有三維銅硒子框架可提供導電的電洞，而有較高的功率因子900 μW/mK2。銻硒四面體結構可藉由其他元素取代銻的位置，扭曲其鑽石結構以達到提高功率因子以及降低熱傳導的目的。理論預測可藉由 IV 族元素鍺、錫、鉛和過渡金屬鈦等元素取代銻來提供電洞載子。本研究藉由燒結與電漿放電製備樣品，探討鈦、錫、鉛、鍺取代銻的熱電效應。 在上述之元素取代效應後，鈦與鉛並沒有帶來顯卓的熱電效應提升，反之錫與鍺能有效地提升電洞載子濃度，然而與摻錫的研究相似的結果已被其他團隊發表，惟鍺的取代效應則尚未被做完整的探討。2 % 鍺的取代有1200μW/mK2的功率因子，相較於母材(900μW/mK2)有 30 % 的提升，因此我們會對鍺的取代效應做完整一系列的研究。摻雜比例從 1~8 % 的結果裡，發現晶格熱傳導係數隨摻雜比例提升減少的合金效應，然而高於 6 % 的取代造成電導大幅提升，使得熱傳導的載子貢獻高於 50% 並嚴重降低載子移動率，致使功率因子大幅衰減與優質係數降低。 4% 的鍺摻雜在提高功率因子與降低熱傳導係數上皆有顯卓的表現，使得優質係數在溫度650 K達到 0.7 相對於母材 (0.54) 有30 ％的提升。 / Cu3SbSe4 is a p-type semiconductor with a narrow band gap near 0.3 eV, and has been found to be a promising thermoelectric material at medium temperatures. The crystal structure of Cu3SbSe4 consists a three-dimensional [Cu3Se4] framework acting as electron hole conduction pathway which cause high power factor near 900 μW/mK2. The inserting guest atom to the Sb site of tetrahedral [SbSe4] framework cause a more distorted diamond-like structure, thus providing a relatively lower lattice thermal conductivity in relatively large electric conductivity. According to theoretical predication which are based on the defect formation energy and band structure calculations, p-type doping can be achieved by substituting Sb with group IV elements, as Ge, Sn, and Pb, and transition metals as Ti. This study is investigation of the doping effect in Cu3SbSe4 semiconductor which are prepared by melting and spark plasma sintering. Herein, we take a close look at the thermoelectric properties of Cu3SbSe4 which are mentioned in previous paragraph. No significant change in results of Ti and Pb. Carrier concentrations are dramatic increasing in results of Sn and Ge, but the results of Sn substitution were already reported by another group. Power factor of Ge substitution is 1,200μW/mK2 which is 30 % more than raw material. We did more study in germanium doping series because it have high power factor which did not be investigated in Cu3SbSe4. Alloy effects, as description of lattice thermal conductivity reducing with doping fraction increasing, are explored in Ge doping fraction from 1 % to 8 %. Although electric conductivity were largely enhanced, figure of merit were reducing by electric contribution of thermal conductivity were higher than 50 % and carrier mobility were significantly reducing when the doping fraction were higher than 4 %. Doping fraction in 4 % have relatively high power factor and relatively low thermal conductivity. Figure of merit in 4 % doping fraction is 0.7, as 30% more than 0.5 of raw material.