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Based on the investigation results on the starting characteristics of metal halide lamps, the time for entering the steady state is defined in a more reasonable manner. From the effects of the applied current on the generated luminance, several starting scenarios are attempted to accelerate the starting transient. Experimental evidence shows that the starting time can be effectively shortened by increasing the lamp current during the glow-to-arc transition and warm-up stage. A short interval of over-power operation during the warm-up stage enables the lamp to further enhance the production of luminance quickly and hence greatly reduce the starting transient period. Index Terms--Electronic ballast, metal halide lamp, starting scenario, starting transient.

A compact-size and high-conversion-efficiency regulator used to stabilize the luminous flux of alternating-current-operated light-emitting diodes (ACOLEDs) is proposed. The presented regulator is composed of a full-bridge rectifier and a power switch to supply directly from ac power source for the ACOLEDs without any ac/dc converter. Commonly adopted pulsewidth modulation techniques are utilized to regulate the input power fed into ACOLEDs. Design guidelines and experimental results of the prototyping regulator for an 8-W ACOLED operating under different input ac voltages (110 \pm 10\ \Vrms, 60 Hz) are provided. According to the experimental results, the advantages of the proposed regulator include simplified design, compact size, high conversion efficiency, and low cost. Since no magnetic component is required in the presented system, therefore, it can easily be fabricated into the same ACOLED chip in the future. [ABSTRACT FROM AUTHOR]