Method to detect uneven AC load or parallel load removal
AssigneeUniversal Lighting Technologies, Inc.
InventorsWei Xiong, Danny Pugh
Life of this patent
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Abstract
A ballast configured for multiple parallel lamp operation includes a system for detecting unbalanced loads or absent lamps in a parallel multiple lamp ballast. The ballast includes one or more starting transformers having windings, each winding connected in series with a lamp connected to the ballast. A winding of one or more of the starting transformers that is not connected in series with one of the lamps is monitored for a voltage in excess of a threshold. A voltage in excess of the threshold across the winding is indicative of an unbalanced load (e.g., an absent or broken lamp). If a voltage above the threshold is detected across the monitored load, the ballast ceases powering the lamps.
Claims20
A ballast configured to connect to a plurality of lamps and provide alternating current (AC) power to the plurality of lamps, the ballast comprising:
- an oscillator configured to receive direct current (DC) power from a DC power rail and provide the AC power to the plurality of lamps;
- a starting transformer comprising
- a primary winding configured to connect in series with a first lamp of the plurality of lamps,
- a first secondary winding configured to connect in series with a second lamp of the plurality of lamps, and
- a second secondary winding;
- and
- an unbalanced load sensing circuit connected to the second secondary winding of the starting transformer, wherein the unbalanced load sensing circuit is configured to monitor a voltage across the second secondary winding of the starting transformer and provide a shut down signal to the oscillator when the voltage across the second secondary winding of the starting transformer exceeds a threshold;
- wherein the oscillator is further configured to cease providing the AC power to the plurality of lamps in response to receiving the shut down signal from the unbalanced load sensing circuit.
A ballast configured to connect to a plurality of lamps, provide alternating current (AC) power to the plurality of lamps, and cease providing AC power to the plurality of lamps in response to a missing lamp or uneven lamp current, the ballast comprising:
- an oscillator configured to provide the AC power to the plurality of lamps;
- a first starting transformer comprising
- a primary winding configured to connect in series with a first lamp of the plurality of lamps,
- a first secondary winding configured to connect in series with a second lamp of the plurality of lamps, and
- a second starting transformer having a primary winding and a first secondary winding, wherein
- the primary winding of the second starting transformer is configured to connect in series with the first secondary winding of the first starting transformer and the second lamp, and
- the first secondary winding of the second starting transformer is configured to connect in series with a fourth lamp of the plurality of lamps;
- and
- a third starting transformer having a primary winding and a first secondary winding, wherein
- the primary winding of the third starting transformer is configured to connect in series with a third lamp of the plurality of lamps, and
- the first secondary winding of the third starting transformer is configured to connect in series with the primary winding of the first starting transformer and the first lamp;
- and
- an unbalanced load sensing circuit connected to a second secondary winding of one of the starting transformers, wherein the unbalanced load sensing circuit is configured to monitor a voltage across the connected second secondary winding of the starting transformer and provide a shut down signal to the oscillator when the voltage across the connected second secondary winding of the starting transformer exceeds a threshold;
- wherein the oscillator is further configured to cease providing the AC power to the plurality of lamps in response to receiving the shut down signal from the unbalanced load sensing circuit.
A light fixture configured to receive power from an alternating current (AC) power supply and provide power to a plurality of lamps, the light fixture comprising:
- an input stage configured to connect to the power supply and provide a direct current (DC) power rail;
- a ballast configured to connect to a plurality of lamps and provide AC power to the plurality of lamps, the ballast comprising
- an oscillator configured to receive DC power from the DC power rail and provide the AC power to the plurality of lamps,
- a starting transformer comprising
- a primary winding configured to connect in series with a first lamp of the plurality of lamps,
- a first secondary winding configured to connect in series with a second lamp of the plurality of lamps, and
- a second secondary winding;
- an unbalanced load sensing circuit connected to the second secondary winding of the starting transformer, wherein the unbalanced load sensing circuit is configured to monitor a voltage across the second secondary winding of the starting transformer and provide a shut down signal to the oscillator when the voltage across the second secondary winding of the starting transformer exceeds a threshold;
- wherein the oscillator is further configured to cease providing the AC power to the plurality of lamps in response to receiving the shut down signal from the unbalanced load sensing circuit;
- and
- a housing configured to support the input stage, the ballast, and the plurality of lamps.
Dependencies are inferred from the claim text.