Filament lamp light source unit and filament lamp light quantity control method
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United States of America Patent
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Nov 9, 2004
Grant Date -
Feb 26, 2004
app pub date -
May 23, 2003
filing date -
May 29, 2002
priority date (Note) -
Expired
status (Latency Note)
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Abstract
The invention relates to a light source unit control method and a light source control unit, and a light source unit comprising a filament lamp with a characteristic of having a light quantity changing almost in proportion to a control voltage, which includes: a current detection sensor connected in series to the lamp; a multiplication circuit for generating a voltage V.sub.w proportionate to the product of a terminal voltage V of the lamp and an output voltage V.sub.1 of the current detection sensor; a square root circuit for generating a voltage V.sub.2 proportionate to the square root of the control voltage V.sub.1 ; an error amplifier circuit for controlling an error to the minimum by comparing the output voltage V.sub.w of the multiplication circuit and the output voltage V.sub.2 of the square root circuit; and a constant voltage power source unit for supplying an electric power to the filament lamp, the unit being connected to an output terminal of the error amplifier circuit, wherein the light quantity of the lamp is controlled by controlling the control voltage.
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