Importance

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Abstract

A stable output, widely dimmable light source (20) utilizing a gas discharge lamp (14) including an external igniter (12) which is utilized to provide lamp ignition at approximately the same time as an AC potential source (22) provides power to the lamp (14) cathodes. A high voltage pulse is applied to the external igniter (12) causing ionization of the lamp gasses at the start of each time period during which the ballasted AC potential source (22) is applied to the lamp (14). Average light output level is controlled by a light output selector (36) which controls lamp on time and thus the average light output of the lamp (44). During operation lamp (14) is turned on several times per second, such as sixty-eight and the AC potential source (22) has a relatively high frequency, such as 45 KHz. When utilized for providing backlighting for a liquid crystal display, the average lamp light output can be controlled in response to ambient light to provide proper backlighting in conditions which vary from total darkness to bright sunlight. For LCD applications lamp (14) has a serpentine shape to provide increased and uniform backlighting.

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First Claim