Electronic elimination of striations in linear lamps

Details Electronic elimination of striations in linear lamps Electronic elimination of striations in linear lamps

2001-07-05

2004-12-28

Lee, Wilson (Department: 2821)

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Silicon controlled rectifier ignition

C315S224000, C315S219000

Reexamination Certificate

active

06836077

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is directed to improving the visual appearance of linear fluorescent lamps, and more particularly, to the elimination of visual striations which may occur in gas discharge lamps. Generally, a gas discharge lamp will have an elongated gas-filled tube having electrodes at each end. A voltage between the electrode accelerates the movement of electrons. This causes the electrons to collide with gas atoms producing positive ions and additional electrons forming a gas plasma of positive and negative charge carriers. Electrons continue to stream toward the lamp's anode and the positive ions toward its cathode sustaining an electric discharge in the tube and further heating the electrodes. The electric discharge causes an emission of radiation having a wavelength dependent on the particular fill gas and the electrical parameters of the discharge.
A fluorescent lamp is a gas discharge lamp in which the inner surface of the tube is coated with a fluorescent phosphor. The phosphor is excited by the ultraviolet radiation from the electric discharge and fluoresces, providing visible light.
During operation of a gas discharge lamp, such as a fluorescent lamp, a phenomenon known as striations can occur. Striations are zones of light intensity, appearing as dark bands. This phenomenon can give a lamp an undesirable strobing effect. An example of the striation phenomenon is shown in
FIG. 1
, which depicts a linear fluorescent lamp
10
employing Krypton added as a buffer gas to improve the efficacy of the lamp. In
FIG. 1
, lamp
10
has striation zones
12
which appear as the dark bands moving along the length of the lamp. Striations in gas discharge lamps are known to occur in cold applications and in other contexts such as Krypton content lamps.
A variety of theories as to why striations occur have been set forth. For example, in U.S. Pat. No. 5,001,386 to Sullivan, it is stated that striations are believed to occur as a result of high-frequency currents re-enforcing a standing wave of varying charge distribution between the lamp electrodes.
Sullivan attempts to solve the striation problem by injecting a dc component superimposed on top of a driving ac current. A disadvantage to this technique is that, by adding the dc bias, it is possible to cause damage to the lamp by moving mercury in the lamp to one end, creating an unbalanced light output. It has also been suggested that increasing the crest factor in a lamp lighting system will eliminate the usual striations. However, increasing the crest factor may also increase the stress on a lamp, which will lead to a shorter lamp life.
Therefore, it would be beneficial to provide a ballast that solves the above-described problems without adding a dc bias and without substantially increasing the crest factor.
SUMMARY OF INVENTION
The present invention provides a ballast circuit powered by a system power source. The ballast is in operative connection with the system power source wherein the ballast is designed to convert the AC system power source to a DC voltage on a DC bus included within the ballast circuit. An inverter circuit is included in the ballast circuit in operative connection with the DC bus to generate an asymmetric alternating current on a lamp input line. Further, a gas discharge lamp is in operative connection to the lamp input line, configured to receive the asymmetric alternating current, thereby eliminating visual striations otherwise occurring in the lamp.


REFERENCES:
patent: 4415839 (1983-11-01), Lesea
patent: 4723098 (1988-02-01), Grubbs
patent: 5001386 (1991-03-01), Sullivan et al.
patent: 5057721 (1991-10-01), Miyazaki et al.
patent: 5744915 (1998-04-01), Nilssen
patent: 5880562 (1999-03-01), Nakagawa et al.
patent: 6031699 (2000-02-01), Dollar, II et al.
patent: 6088205 (2000-07-01), Neiger et al.
patent: 6121732 (2000-09-01), Parker et al.
patent: 6194840 (2001-02-01), Chang
patent: 6195241 (2001-02-01), Brooks et al.
patent: 6229679 (2001-05-01), Macbeth
patent: 6239962 (2001-05-01), Seymour et al.
patent: 6259996 (2001-07-01), Haun et al.
patent: 6262871 (2001-07-01), Nemir et al.
patent: 6275044 (2001-08-01), Scott
Stan Gibilisco, TAB Encyclopedia of Electronics for Technicians and Hobbyists, pp. 101 and 919.

Affiliated with

Also associated with

Rating

Electronic elimination of striations in linear lamps does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Electronic elimination of striations in linear lamps, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electronic elimination of striations in linear lamps will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3274599