US 6,982,528 B2 | ||
Thermal protection for lamp ballasts | ||
David E. Cottongim, Sellersville, Pa. (US); Jecko Arakkal, Emmaus, Pa. (US); Venkatesh Chitta, Center Valley, Pa. (US); and Mark S. Taipale, Harleysville, Pa. (US) | ||
Assigned to Lutron Electronics Co., Inc., Coopersburg, Pa. (US) | ||
Filed on Nov. 12, 2003, as Appl. No. 10/706,677. | ||
Prior Publication US 2005/0099142 A1, May 12, 2005 | ||
Int. Cl. G05F 1/00 (2006.01); H01H 5/04 (2006.01) |
U.S. Cl. 315—309 | 47 Claims |
1. A circuit for controlling output current from a ballast to a lamp comprising:
a) a temperature sensing circuit thermally coupled to the ballast to provide a temperature signal having a magnitude indicative
of ballast temperature, Tb, and
b) control circuitry capable of causing the ballast to enter a current limiting mode when the magnitude of the temperature
signal indicates that Tb has exceeded a predetermined maximum desired ballast temperature, T1;
wherein the control circuitry reduces the output current in response to the temperature signal according to one of (i) a step
function or (ii) a combination of step and continuous functions, while continuing to operate the ballast.
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