Title: Dimming circuit with saturated semiconductor device

Abstract: A fluorescent lamp is operated by a-c pulses having a pulse length sufficiently short that the lamp acts like slightly positive impedances. A pulse modulator which produces the pulses has a power transistor biased to saturation. However, varying the base drive of the saturated transistor causes a generally linear change in tube current to permit tube dimming and control. A servo circuit provides feedback control of the base drive to automatically compensate for variable effects to maintain constant tube lighting. Tube dimming is obtained by adjusting the feedback circuits of the servo.

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Inventors: Gray, George (Lambertville, NJ, US)

Application Number: 391953
Filing Date: 1973-08-27
Publication_date: 1976-02-03
Assignee: Lutron Electronics Co., Inc. (Coopersburg, PA)
Primary Class(es): 315/210 315/224, 315/276, 315/DIG4
Other Classes:
US Patent Ref:

3611024	Oct, 1971	Nakatsu et al.	315/DIG.
3619716	Nov, 1971	Spira	315/DIG.
3681654	Aug, 1972	Quinn	315/DIG.

Other Refs:
Primary Examiner: Heyman, John S.
Assistant Examiner: Davis, B. P.
Attorney: Ostrolenk, Faber, Gerb & Soffen