| US 7,586,268 B2 | ||
| Apparatus and method for controlling the filament voltage in an electronic dimming ballast | ||
| Brent Gawrys, Whitehall, Pa. (US); Jecko J. Arakkal, Emmaus, Pa. (US); Mark S. Taipale, Harleysville, Pa. (US); Dragan Veskovic, Allentown, Pa. (US); and Mark Charles Fischer, Siler City, N.C. (US) | ||
| Assigned to Lutron Electronics Co., Inc., Coopersburg, Pa. (US) | ||
| Filed on Jul. 21, 2006, as Appl. No. 11/491,202. | ||
| Claims priority of provisional application 60/748861, filed on Dec. 09, 2005. | ||
| Prior Publication US 2007/0132401 A1, Jun. 14, 2007 | ||
| Int. Cl. H05B 41/16 (2006.01) | ||
| U.S. Cl. 315—274 [315/224; 315/307; 315/312] | 62 Claims |
| 1. An electronic ballast for driving a gas discharge lamp having a plurality of lamp filaments, the ballast comprising:
an output circuit operable to receive a high-frequency AC voltage and comprising an inductor;
a plurality of filament windings magnetically coupled to the inductor, each of the plurality of filament windings connectable
to at least one of the plurality of filaments of the lamp and operable to supply an AC filament voltage to one of the plurality
of filaments;
a control winding magnetically coupled to the inductor;
a controllably conductive device having a control input and first and second terminals coupled such that the controllably
conductive device is operable to control a voltage across the control winding; and
a control circuit coupled to the control input of the controllably conductive device to selectively render the controllably
conductive device to be conductive and to be non-conductive;
wherein when the controllably conductive device is non-conductive, each of the plurality of AC filament voltages has a first
magnitude, and when the controllably conductive device is conductive, each of the plurality of AC filament voltages has a
second magnitude, the control circuit operable to render the controllably conductive device to be non-conductive when an intensity
of the lamp is below a predetermined threshold and to render the controllably conductive device to be conductive when the
intensity of the lamp is above the predetermined threshold.
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