.600 W High Pressure Sodium Tune Optical Electronic Ballasts

To save energy, the dimmable ballast for HID lamps has attracted considerable attention and raised market expectations through its diversified product range. This thesis mainly concerns the development of dimmable electronic ballast for HID lamps.At the beginning of the thesis, characteristics of different gas discharge lamps, i.e. fluorescent lamps and HID lamps, are introduced. The operation principles, superiority and developments of electronic ballast are also presented.Chapter 2 analyzes the physical process of the discharge based on microcosmic theory, and then describes the electrical characteristics of HID lamps using the local thermodynamic equilibrium (LTE) concept.Chapter 3 emphases on the development of a PSPICE model for HPS lamps. It is derived by curve-fitting method, and performs well in the design of dimmable electronic ballast for HPS lamps with different power level.Chapter 4 reviews all available dimming methods presently. A prototype of dimmable electronic ballast for 600W HPS lamp is developed. Its design procedure is detailed in this Chapter. Finally, a novel dimming approach based on a T type filter is proposed. Using this method, wide dimming range can be achieved with narrow frequency range and constant DC link voltage. And the lamp current keeps perfect sine wave all the time, which means low lamp current crest factor (CCF) is obtained. Its validity is verified by simulation and experiment.