Electric lamp and discharge devices: systems – Pulsating or a.c. supply
Reexamination Certificate
2000-05-24
2002-06-18
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
C315S260000, C315S287000, C313S607000
Reexamination Certificate
active
06407513
ABSTRACT:
TECHNICAL FIELD
This invention relates to a gas-discharge lamp which makes use of a so-called dielectric barrier discharge. To this end, a discharge vessel which is at least partially transparent and filled with a gas filling has at least one anode and at least one cathode. The electrodes have a geometry in the form of strips, that is to say they are in the form of strips at least in places. However, they may also have more complex shapes, for example with branches. In the case of a dielectric barrier discharge, at least one of the electrodes, the anode for unipolar operation, must be covered with a dielectric layer.
However, in the context of this application, the terms anode and cathode should not be regarded as limiting the invention to unipolar operation. In a bipolar case, there is no difference between anodes and cathodes, so that the statements for one of the two electrode groups then apply to all electrodes.
1. Background Art
Lamps with a dielectric barrier discharge are known in the prior art, particularly for back lighting of flat screens. This application area will not be described in detail here.
With respect to a preferred embodiment of the invention described further below, reference is made, as prior art, to Hella-Lichttechnik R & D Review 1996 (08/96), page 119, and to EP 0 813 996 A2. This prior art includes the idea of improving the warning function of a brake warning light by varying the illuminated area, for example varying the illuminated length of the brake warning light.
2. Description of the Invention
This invention is based on the technical problem of extending the application options for gas-discharge lamps using a dielectric barrier discharge. According to the invention, this problem is solved by a gas-discharge lamp having a discharge vessel filled with a gas filling, having at least one anode in the form of a strip and having at least one cathode in the form of a strip, which are arranged essentially parallel to one another, at least in places, and having a dielectric layer at least between the anode and the gas filling, characterized in that in the region of its essentially parallel profile, the electrode arrangement is at least partially inhomogeneous along its length in a form which varies a maintaining voltage.
Furthermore, the invention for solving this problem relates to a method for actuating such a gas-discharge lamp having pulsed real-power injection, in which a maintaining voltage for the lamp is varied by varying at least one time parameter of the supply power.
Finally, one particular solution to this problem according to the invention results from an apparatus for indicating a braking deceleration of a motor vehicle or two-wheeled vehicle having such a lamp, a braking deceleration sensor and a control unit which is supplied with a signal from the braking deceleration sensor and actuates the lamp.
The basic idea of the invention is to design the electrode system of a lamp with a dielectric barrier discharge such that inhomogeneous discharge preconditions exist along at least a part of the length of the electrodes. In this case, the aim is to monotonically vary a maintaining voltage for the discharge in places, at least in terms of an effective mean value. This maintaining voltage may be, in particular, a minimum maintaining voltage which in this case does not correspond to the starting voltage of an individual discharge, but is the minimum voltage which allows a discharge structure to be maintained at a specific point in the electrode arrangement.
In the case of the pulsed real-power injection, which is considered in a preferred manner here, the restarting of an individual discharge in the residual ionization that still remains after one of the regular brief interruptions in the real-power injection, that is to say those brief interruptions which occur in continuous operation of the light, does not mean restarting. In fact, restarting means switching on the lamp again without the gas filling having any specific residual ionization.
A major advantage of a gas-discharge lamp with a dielectric barrier discharge over conventional gas-discharge lamps is the positive current/voltage characteristic. By virtue of the unambiguous relationship between the current and voltage, this allows a change in the supply voltage to lead to a change in the illuminated length of the gas-discharge lamp with a dielectric barrier discharge, and thus to a change in the lamp current. In conventional fluorescent lamps, this is prevented by a negative differential resistance in the current/voltage characteristics.
If the minimum maintaining voltage is now varied over a portion of the length of the electrode arrangement in the manner according to the invention, then it is possible, during operation, to control the portion of this length section with the monotonically varying minimum maintaining voltage over which discharges burn, by adjusting and varying the power supply, in particular its voltage. The illuminated length section is thus adjusted.
There are various options for the minimum maintaining voltage of such an inhomogeneous electrode arrangement to be monotonically dependent on position. A first option is to vary the distance between the electrodes that governs the discharge. The larger the gap becomes, the greater is the minimum maintaining voltage required to maintain a discharge across this distance.
On the other hand, the difference between the starting voltage and the minimum maintaining voltage can be explained in that a discharge to a specific point in the electrode arrangement with a specific gap can always start in an adjacent region with a shorter gap and can move into the region in which the available voltage is just still sufficient for the discharge. This is due to the fundamental phenomenon that the discharge structures are wherever possible distributed over the available electrode surfaces since, for a dielectric barrier discharge, the greater available area on the dieletrically coated electrode provides better high-frequency conductivity and thus a reduced voltage drop across the dielectric.
On the other hand, there are also structures in which the movement of individual discharge structures between points with a gap which is sufficiently short to start a discharge and points at which the gap is only sufficiently short to maintain a discharge that has been started at some other point is not directly possible. For example, in the case of the invention, it is possible to provide the electrodes with projections (which are known per se) for physical localization of individual discharges. These projections may be, for example, small tabs on one or both electrodes, between which the discharge is maintained. The critical distance for starting and maintaining a discharge is then the distance between the tip of such a tab and the opposite electrode, or between the tips of two opposite tabs. It is obvious that, in this case, the discharge structures cannot move continuously and a voltage which is sufficient to maintain the discharge between the projections must first of all be available for a further movement step (to the next projection) to take place. In an extreme case, the situation may thus even arise where the maintaining voltage mentioned in claim
1
corresponds to the discharge starting voltage and not to the minimum maintaining voltage. Compromises between these extreme situations are, of course, also feasible.
Furthermore, it can be seen from the example with the electrode projections that the discharge characteristics of the electrode arrangement need not necessarily be varied continuously or monotonically. However, for various applications (which will be described in more detail in the following text), the discharge characteristics should be monotonic functions of position over a certain region of the electrode arrangement at those points which always support discharges, that is to say, for example, at the tips of the projections.
A further option for varying the discharge voltage is the dependency of the anode width on position. On the one
Hitzschke Lothar
Vollkommer Frank
Lee Wilson
Meyer William E.
Patent-Treuhand-Gesellschaft fuer elektrische Gluehlampen mbH
Wong Don
LandOfFree
Gas-discharge lamp with controllable length of illumination does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas-discharge lamp with controllable length of illumination, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas-discharge lamp with controllable length of illumination will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2970252