Electric lamp and discharge devices: systems – Pulsating or a.c. supply
Patent
1997-11-07
1999-10-12
Wong, Don
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
315260, 313497, 313607, H05B 4100
Patent
active
059659882
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns electric lamps and in particular electric discharge lamps. More in particular the invention concerns an electric discharge lamp and a method of operating the lamp having both galvanic and dielectric electrodes.
DESCRIPTION OF THE RELATED ART
From DE-U-89 04 853 an AC powered fluorescent lamp is already known. Inside the discharge chamber of the lamp are two spiral-shaped incandescent electrodes and one metallic element which is separated from the interior of the discharge chamber by a dielectric. A discharge is generated in the discharge chamber by the heated spiral-shaped electrodes. In addition, a voltage is applied to the metallic element during operation. In this manner the metallic element functions as a condenser plate for the discharge so that the electrical resistance of the discharge plasma is increased, alheit localized all the more, the more current density is applied. The object is to spatially homogenize the lamp current and therefore the brightness of the lamp with assistance from the condenser plate and to increase the effectiveness of the lamp.
In EP-A-0 550 047 an AC-powered flat fluorescent lamp was shown which has a discharge chamber constructed of planar plates. On the interior of the plates a pair of planar electrodes are arranged, which are coated with dielectric glass layers. Additionally the lamp has a pair of galvanic electrodes in its interior. Both pairs of electrodes are operated with a high frequency of either differing or identical frequency, in the second case out of phase with each other by 90.degree.. The planar electrodes create capacitatively a plasma which is stable and spatially uniform. The galvanic electrodes create a low pressure discharge with a high light output which is, however, spatially nonuniform. Both discharges supplement each other to create a planar light source of high brightness and uniformity.
Therefore, and because of its flat shape, the lamp is particularly suited for use in the rear illumination of liquid crystal displays.
From EP-A 700 074 a longish lamp with a tubular discharge chamber which is hermetically sealed on both ends and is filled with neon gas is known. The interior surface of the discharge chamber is optionally coated with a phosphor coating, specifically Y.sub.3 Al.sub.5 O.sub.12 :Ce. The interior of the discharge chamber has two opposing unheated electrodes connected to electrical leads.
The lamp can be operated by the two following methods: serves to generate a discharge in the discharge chamber whereby electromagnetic radiation, primarily in the red and infrared regions of the spectrum with low VUV and UV proportions, is emitted. In this operating method the lamp emits mostly a red light and is therefore suited, for example, for use in automobile brake lights. In this case a phosphor coating is not used. in .mu.s range, serves to generate a discharge in the discharge chamber whereby electromagnetic radiation is likewise emitted in the red and infrared regions of the spectrum, but clearly with a higher VUV and UV proportion in contrast to operating method number 1. The VUV and UV radiation excites the Y.sub.3 Al.sub.5 O.sub.12 :Ce phosphor, which fluoresces in the yellow spectrum (mid wavelength: 556 nm, full width at half maximum (FWHM): 103 nm). Therefore, in this operating method the lamp emits primarily a yellow light and is suited, for example, for use in automobile turn-signal lamps.
In the case of the pulse operation of the lamp, a sequence of voltage pulses is applied to the lead-in wires which extend through the ends of the discharge chamber to the exterior. The voltage pulses are separated from each other by relatively long pauses (low duty cycle). The pause durations are necessary for the determination of the desired color locus of the lamp.
Since ionization quickly decreases during the pulse pauses, relatively high pulse voltages are needed to reignite the discharge, particularly in the case of long lamps which have a great distance between the electrodes. Higher pulse vol
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patent: 4260932 (1981-04-01), Johnson
patent: 4427920 (1984-01-01), Proud et al.
patent: 5028847 (1991-07-01), Greb et al.
patent: 5367226 (1994-11-01), Ukegawa et al.
patent: 5604410 (1997-02-01), Vollkommer et al.
Hitzschke Lothar
Stockwald Klaus
Vollkommer Frank
Lee Wilson
Meyer William E.
Patent-Treuhand-Gesellschaft fur Elektrische Gluehlampen mbH
Wong Don
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