Lamp ballast system having improved power factor and end-of-lamp-life protection circuit
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United States of America Patent
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Dec 9, 2003
Grant Date -
Oct 9, 2003
app pub date -
Apr 3, 2002
filing date -
Apr 3, 2002
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A ballast system for use with a fluorescent lamp having two filaments disposed at opposite ends of the lamp. The ballast system has a DC input terminal for connection to a DC voltage source or for receiving a rectified DC signal. The ballast system also includes a capacitor operably connected between the DC input terminal and the lamp and an inductor, wherein the lamp operably connects the capacitor in series with the inductor. The ballast system further includes a first power transistor operably connected to a junction joining the DC input terminal to the capacitor and a second power transistor operably connected to drive the first power transistor. The emitter of the first power transistor and the collector of the second power transistor are operably connected to the inductor such that the two power transistors sense a change in voltage across the inductor and control current from the DC voltage source to the capacitor in response to a change in voltage across the inductor.
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