Advances in discharge tube materials and optimization of metal halide chemistries of High Intensity Discharge light sources led to a dramatic increase of lamps lifetime. Moreover, the use of electronic power supplies, i.e., "electronics ballasts", made possible operation of lamps, in many instances, beyond their rated life. This combination between lamp longevity and power control raised a new issue for HID lamps EOL (End-of-Life) phenomena. Specifically, the effects of leakage of the discharge tube gas fill inside the outer envelope as result of ceramic wall corrosion or seal failure and the consequential failure of the outer envelope insulation were investigated. A method and a ballast circuit arrangement were developed to shut off the lamp power when End-of-Life condition(s) are reached.
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