Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Silicon controlled rectifier ignition
Reexamination Certificate
1999-03-31
2001-06-26
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Silicon controlled rectifier ignition
C315S225000, C315S094000, C315S099000
Reexamination Certificate
active
06252357
ABSTRACT:
INCORPORATION BY REFERENCE
This application claims priority from Japanese Patent Application 10-87565 filed Mar. 31, 1998, 10-185372 filed Jun. 30, 1998, and 11-19699 filed Jan. 28, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to self ballasted fluorescent lamps and to lighting fixtures using such lamps.
2. Description of Related Art
Self ballasted fluorescent lamps having fluorescent arc tubes are known. Such self ballasted fluorescent lamps generally have a ballast power supply and an E form base for screwing into a conventional incandescent light socket. The ballast power supply utilizes commercial AC power to provide the high frequency power needed to drive a fluorescent arc tube.
There are operational and safety hazards associated with the operation of fluorescent arc tubes when they reach the end of their useful lives. Near the end of a tube's life, it becomes difficult to operate the tube even when applying the rated voltage. As the tube ages, its electrodes no longer emit as well. The effective resistance of the tube increases. The current being forced through the tube causes the voltage drop across the tube to rise and the electrodes and tube overheat, sometimes to a very dangerous degree. There is a risk of fire and a risk that the tube will explode. Before any dangerous condition arises, it is desirable to stop operation of the ballast power supply and end operation of the tube.
Japanese Patent Laid-open No. 10-189279 discloses a ballast power supply driven fluorescent tube arrangement. The ballast power supply includes a switch that self-destructs at the end of tube life when the current flowing through the switch exceeds a predetermined amount. The switch opening stops the power supply. However, stopping the lamp is not reliable based solely on the current flow through the switch, in part because of wide variation in the electrical characteristics of the switch.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides various self ballasted fluorescent lamps and lighting fixtures using them. Our arrangements have a ballast power supply that self-destructs at the end of the useful life of the lamp. However, our self-destruct arrangements depend not just on current flow through a switch element, but also upon sensing an increasing temperature from the tube itself and/or the electrodes of the tube. Our ballast power supply generates the high frequency power needed to operate the lamp and our self destruct arrangements stop operation of the ballast power supply in the early stages of the fluorescent lamp's end of useful life.
Lamps according to the present invention have a base with a plug portion for receiving commercial power. The base contains a circuit board on which the ballast power supply components are formed. At least a portion of the circuit board is near at least one electrode of the arc tube so that there is heat transfer from the electrode to the ballast power supply. The base covers part of the tube and the ballast power supply. In at least one embodiment of the invention the ballast power supply includes a switch element, preferably constituted by a FET, that is destroyed by a temperature rise of the tube and/or the tube's electrode that occurs at the end of life of the tube.
When the fluorescent arc tube reaches it's end of life there is a so-called half wave discharge. The striking voltage of the fluorescent arc tube increases, and electrode temperature rises. The temperature of the switch element rises due to its proximity to the electrode. The switch element fails completely when a certain predetermined temperature is reached. This switch element failure stops operation of the ballast power supply early enough to avoid the risks associated with tube and electrode overheating that occur at the end of life of fluorescent arc tube.
In another embodiment, a capacitor in the ballast power supply is made of a material that breaks down at high temperature. Overheating of the electrode causes this capacitor to break down and stop operation of the ballast power supply.
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Araki Tsutomu
Hakuta Shinya
Nakaya Fuminori
Osaki Hajime
Tanaka Toshiya
Pillsbury & Winthrop LLP
Toshiba Lighting & Technology Corporation
Vo Tuyet T.
Wong Don
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