| Summary: | 碩士 === 國立中正大學 === 電機工程研究所 === 89 === This thesis presents analysis, design and consideration for an electronic dimming ballast with frequency control. In the dimming analysis, a first order steady state equivalent circuit model is adopted to replace a fluorescent lamp. A half-bridge inverter topology is first described, from which the one equipped with two paralleled series-resonant-parallel-loaded (SRPL) networks used to drive 58W lamps is discussed. Various operation modes and possible problems exist in system are also investigated, on which protection circuits are designed. Component stresses are reduced by adjusting the duty ratio of gate signals. Active filament-temperature detection circuit for minimizing electrode sputtering is proposed, which results in increasing lamp life. Hardware measurements have verified the validity and feasibility of the designed ballast. When the lamps are dimmed out to a lower power level, it might result in striation phenomena, which are also investigated in the thesis. Methods to improve on the phenomena are, therefore, proposed to ensure good performance during dimming operation.
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