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US 5,517,086 AGranted
Modified valley fill high power factor correction ballast
AssigneeGeneral Electric Company
InventorsSayed-Amr El-Hamamsy, Mustansir H. Kheraluwala
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Abstract
A modified valley fill circuit, including a main ballasting inductor for supplying an electrolytic capacitor, has an additional charging winding on the main ballasting inductor for charging the electrolytic capacitor to a predetermined voltage which maximizes the power factor of the input current by optimizing the conduction angle of the input current. In a discharge lamp ballast, the modified valley fill circuit reduces the lamp current crest factor by controlling the frequency with a lamp current control loop.
Claims6
A ballast for a discharge lamp, comprising:
- a rectifier for receiving an ac line voltage and providing a rectified voltage on a dc voltage bus;
- a half-bridge configuration of switching devices coupled across said dc voltage bus;
- an energy-storage capacitance coupled to said dc bus by a diode;
- a resonant output circuit comprising a ballast inductor connected to a junction between said switching devices of said half-bridge and a resonant capacitance, said lamp being connected in parallel with said resonant capacitance, said ballast inductor comprising an additional winding thereon for supplying said energy storage capacitance, said additional winding having a turns ratio with respect to turns of said inductor which is selected to maintain the voltage across said energy-storage capacitance at less than half the peak line voltage in order to optimize conduction time of said rectifier and thereby maximize input power factor;
- and
- a current feedback loop comprising frequency control for maintaining current through said lamp substantially constant.
3 more elements
Dependencies are inferred from the claim text.