EP1118101B1 - Discharge lamp for dielectrically impeded discharges with improved electrode configuration - Google Patents

Abstract

This application relates to a discharge lamp for producing dielectric impediments which has a new electrode configuration with a meandering shape. In this case, either the anode(s) or both the anode(s) and the cathode(s) are of meandering shape.

Description

Technical area

This invention relates to a dielectrically impeded discharge designed discharge lamps. Such a discharge lamp has in a discharge vessel filled with a discharge medium, at least a cathode and at least one anode, wherein at least the anode is separated from the discharge medium by a dielectric layer. The operation of dielectrically impeded discharges in such Discharge lamps are not interested in detail here. Therefore, it will be up here referred to the prior art, in particular those still below cited documents.

In particular, this invention is concerned with the electrode configuration in FIG a discharge lamp for dielectrically impeded discharges.

State of the art

The invention is based on known strip-shaped electrodes. With strip-shaped electrodes are in particular discharge lamps provided in the form of flat radiators, consisting essentially of two plane-parallel and optionally connected by a frame plates consist. The strip-shaped electrodes are generally on formed one or more of the walls of these plates, wherein in a corresponding flat discharge volume between the plates dielectrically Disabled discharges can be generated. In general, run the strip-shaped cathodes and anodes thereby substantially parallel to each other.

Of course, strip electrodes are also used on other discharge lamps possible, in particular with different discharge vessel geometries. They can also be used on non-flat discharge vessels on interior or exterior surfaces deposited by the discharge vessel forming boundary walls be or independent of a discharge vessel wall, about a plate carrying the electrode strips inside the discharge vessel. In particular, the invention is therefore directed to strip-shaped electrodes, that on a wall of the discharge vessel or on a wall in the Discharge vessel are applied.

In principle, however, no carrier for the electrode strips for this invention necessary.

The invention is thus based on a discharge lamp with a with a Discharge medium filled discharge vessel, a strip-shaped Cathode and a strip-shaped anode and a dielectric Layer between the anode and the discharge medium.

Essential criteria in the development and evaluation of electrode configurations in the discharge lamps with dielectric considered here Disabled discharges are in addition to a beneficial electrical behavior the electrode configuration as an electrical component further also the geometric properties of the electrode configuration or the with it to be generated discharge structures. It can be on the one hand the uniformity of light production both temporally and locally Respect, d. H. on the temporal fluctuation and on a very homogeneous surface distribution. Of course, there can be certain Inhomogeneous area distributions are intended to be. Further, for certain applications, for example in the field of flat panel backlighting or in the case of signal lamps beyond that also with the discharge lamp Areal luminance of interest to achieve.

Presentation of the invention

Overall, the present invention is based on the technical problem a discharge lamp for dielectrically impeded discharges with a improved electrode configuration as well as such a discharge lamp and further comprising a matching ballast lighting system specify.

According to the invention, this problem is solved by a discharge lamp the above-mentioned type, which is characterized in that the anode meandering, so that the distance between the cathode and the Anode is modulated by the meandering shape or

characterized in that the cathode and the anode meander run, wherein the meandering forms are locally out of phase with each other, so that the distance between the cathode and the anode through both Meandering is modulated.

Furthermore, the invention relates to a lighting system with a of these two discharge lamps and a ballast that is pulsed to one Active power coupling is designed in the discharge lamp.

Numerous preferred embodiments of the discharge lamp and the ballast and thus the lighting system are in the dependent Claims are given and will be described in more detail below.

In its most general form, the invention is with regard to the discharge lamp to consider in two variants. The first variant uses the invention meandering course of the electrodes only in the Anode ahead. The exact course of the strip-shaped cathode is Basically open, but should by the meandering shape of the anode of the Discharge relevant distance between the cathode and the anode modulated be. For this purpose, the cathode can be a straight strip shape or a have any other strip shape, as long as the modulation of the discharge distance not canceled by the meandering form or by influencing the discharge distance in such a way in a different way Form is superimposed that intended by the invention Effect is missed. In particular, however, can also be at the cathode a meandering shape, this being in a special case of the second Variant of the invention corresponds.

A prerequisite for this first variant of the invention discussed here is that the anode of the discharge lamp with respect to the cathode in any Form excellent, so in principle distinguishable from the cathode is. This can, in principle, be the case in many different forms Simplest case in that between the cathode and the discharge medium no dielectric layer is located.

Occasionally, however, a dielectric layer on the or Cathode (s) used to protect them from sputter damage due to ion bombardment to protect from the discharge medium. Often this is the dielectric Layer on the cathode or cathodes thinner than the dielectric layer in Anode case. Even then, the anode is excellent with respect to the cathode.

Even the case that the anode only by a corresponding name at the discharge lamp, for example by a polarity symbol on her electrical connection, excellent, is included here. in principle It should be noted in this context that in discharge lamps for dielectrically impeded discharges both a bipolar and a Unipolar power supply is possible. In the bipolar case, replace the Cathodes and anodes, of course, alternating their electric roles and are therefore indistinguishable from each other during operation. Then the apply met in this description for one of the two electrode types Statements for both electrode types. For the first variant just discussed conversely, the invention means that such a discharge lamp designed for unipolar operation.

Before now the effects and advantages of the meander shape according to the invention will be explained in detail, first, the second variant of illustrated discharge lamp according to the invention. In this case, the concerns Meander shape both types of electrodes, d. H. at least one cathode and at least one anode run meandering. It is envisaged that the meandering forms with respect to the modulation of the discharge distance reinforce each other between the cathode and the anode. To they run in opposite phases to each other.

However, the invention is to be understood in general as far as the Meander shapes of the electrodes need not be periodic. Therefore, concerns the concept of antiphase may only be local and other Place altered periodicity and possibly also non-periodic Cases where, however, locally are essentially "mountain on valley" and "valley on the mountain ", so the electrodes in essentially the same places towards each other or away from each other.

Furthermore, it should be clarified that the described antiphase amplification The meandering forms do not necessarily involve an algebraic addition of the the meander shape respectively associated "stroke" in the discharge distance direction must mean. Rather, the meandering forms in different Layers are also not necessarily parallel to each other have to go. For example, the electrode strips on opposite Be formed inside walls of a discharge vessel.

For both variants of the invention applies that the discharge distance between Cathode and anode by at least one meandering shape of an electrode is modulated. Thus, the respective locations of the locally smallest discharge gap form at the same time places the highest local field and thus preferred Starting points for individual discharge structures.

The discharge lamps according to the invention are namely particularly advantageous in connection with a pulsed active power injection method, which is not described here. It is referred to on the WO 94/23 442 and DE-P 43 11 197.1.

In the case described there Operating method for dielectric barrier discharge lamps preferably arise largely spatially stable single discharge structures, in accordance with the coupled active power in different Number first in the places with the largest field strengths form between the electrodes. It can also be less localized Forming "curtain-like" discharge structures, in the context of this Invention are equivalent.

Also come in principle conceivable deviating operating methods Of course, discharges between the electrodes exclusively or at least preferably at the locations between the electrodes, in which the highest field strengths are present. Accordingly, the comments apply to this invention also in a more general sense.

In DE 196 36 965 A1 already electrode structures for local Field enhancement described to improve the temporal and local Inhomogeneity of the overall picture from single discharges provided are. In particular, nose-like punctate projections on the rest straight running electrode plates or wires provided. On this document is also expressly referenced.

In contrast to this prior art, the present invention is directed however, in the case referred to above as the first variant was based on a local field reinforcement by a shaping on sides the anode. For the unipolar case, however, the cited prior art Protrusions on the cathode. The state of the art was at that time namely, the idea that in the pulsed operating method occurring discharge structures at the cathode a rather pointed and have a rather fanned out shape at the anode. Accordingly should by geometric design of the cathode the corresponding Tip of the discharge structure are localized, therefore logically in essential punctiform lugs at the cathode are preferably considered were.

In this invention, however, the observation has been made that the rather fanned out sides of the discharge structures to the anode also can be localized, by anode shapes, here as meandering are circumscribed. This term covers many different things conceivable shapes that are wavy in some way, but there are do not necessarily have to be round. Illustrative examples are sine waves, Square waves, sawtooth waves, etc.

A meandering anode - in combination with a meandering one Cathode according to the so-called second variant or not - provides However, compared to the conventional structures significant advantages. So is a meandering shape over the already described nose-like According to the prior art capacitively much cheaper, because between the electrode strips to a significant proportion of the electrode length can be significantly longer distances than the actual for the discharges significant distance at the places where the Electrodes come closest. With a reduced capacity of the electrode configuration and thus lower reactive currents can be, however the ballasts necessary for the operation of the discharge lamps design smaller and thus save costs, construction volume and weight. Further can with smaller capacities to be operated steeper pulse edges and thus better overall pulse shapes are realized.

In a preferred embodiment, the discharge lamp sees a Electrode configuration of a plurality of cathodes and a plurality Anodes ago, which are arranged alternately in individual strips. This means, in each case only one anode strip between two cathode strips runs and vice versa. Of course, also in this embodiment meet the capacitive points of view, with respect to the opposite of electrodes Polarity surrounded electrodes even to a greater extent. Incidentally, this embodiment with its advantages applies to both initially distinguished variants of the invention.

In the alternating arrangement, however, there is still another side the invention. From the already discussed term "meandering shape" results namely inevitably, that a meandering electrode leading to two Side adjacent to respective electrodes of opposite polarity, the preferred locations for the respective discharge structures on both sides alternate along the considered electrode. Within the scope of the invention has now been found that this is essential in particular for an anode, because the already mentioned somewhat fanned pages of several single discharge structures "disturbing" one another at the same anode. This means that if the distance between the anode-side ends is too short the discharge structures from each other no stable overall discharge pattern can be built.

In the case of a bipolar power supply, this of course applies to all electrodes. In the unipolar case, the discharge structures interfere with the cathodes practically not each other. However, a meandering shape is related here with the described alternating electrode arrangement for capacitive reasons of considerable advantage, as elsewhere executed. In addition, the meandering shape leads to a greater distance between the cathode-side "pointed" ends of the discharge structures on the cathode strip. This is advantageous because the discharge peaks on the cathodes to a certain extent a catchment area have both sides of the cathode strip, in which a Oberflächenglimmentladung on the cathode strip can burn visible, apparently with has to do with the electron supply for the discharge structure. Is now the Distance between the discharge peaks larger, thus increases this catchment area on the cathode, which is the overall effectiveness of the lamp benefits.

However, in the invention according to the first variant, the case is also included, that the strip-shaped cathode has no such meandering shape. she can in particular in the context of this first variant in conventional Way straight. Especially in cases where the mutual Disturbance of the single discharge structures with their narrow cathode side End opposite the wide fanned anode side a significantly subordinate Role plays, z. B. at particularly large discharge intervals have straight cathode strips have the advantage that they are in the direction transverse to the strip direction a dense arrangement of the individual strips Enable discharge structures. It can by an inventively meandering anode form again on the mutual interference of the Individual discharge structures are taken into account.

In this case, it is preferable that the meandering forms of two of them Cathode of adjacent anodes locally in phase with each other to an alternating arrangement of the discharge preferential sites on both sides to achieve the cathode.

With regard to a quantitative geometric description of preferred regions for the electrode configurations according to the invention, two criteria that are independent of one another in principle have proven useful. The first criterion relates to the relationship between the fluctuation of the discharge distance, ie the difference between the maximum discharge distance d _max within half a period length and the minimum discharge distance d _min in the same half period, and this half period length of the meander shape, hereinafter referred to with the abbreviation SL As the upper limit for this ratio, a value of 0.6 has been found to be favorable. Better is the value 0.5, more preferably 0.4.

The relationship just described may also be within the scope of the invention take very small values as long as it is different from zero. noticeable Effects of the invention are already at values from z. B. 0.01 achievable.

The second criterion concerns the minimum already referred to Discharge distance in its relationship to the maximum occurring discharge gap in terms of actually in interpretive mode the discharge lamp occurring discharge structures. For this one must recall that a single discharge structure is present in both in the case of relatively localized discharge structures as well as in the already mentioned "curtain-like" broadened case a certain "averaging" extent has and thus a certain course of discharge distances spans. In this case, a single discharge structure in many cases not reach the maximum discharge distance, but only at one relatively strong power input. The terms minimum and maximum Discharge distance relate in this respect rather to the operation of the lamp in principle achievable discharge distances than on the actual in one certain operating conditions implemented discharge distances. Preferably the minimum discharge distance is greater than 30% and less than 90% of the maximum discharge distance, but preferably greater than 40% or 50% of the maximum discharge distance.

The maximum distance as I said is not necessarily the in a certain operating state actually of discharge structures reached maximum striking distance, but in the electrode configuration reachable to the specific discharge lamp. Essential in this context is another possibility according to the invention namely an operation of the discharge lamp with a ballast for a power control in the discharge lamp is suitable. Here is in a power control device of the ballast a suitable electrical Parameters of the power supply of the discharge lamp changed so that a burning voltage of the discharges is varied and the individual Discharges more or less large impact widths in the electrode configuration can bridge. Accordingly, either changes the total volume of individual discharge structures or the number of individual ones Discharge structures at the respective preferred locations between the Electrodes. Thus, it is possible, in particular, for several individual discharge structures next to one another at the same preferred location of the electrode configuration occur. For further details, please refer to the Parallel application "Dimmable discharge lamp for dielectrically handicapped Discharge "by the same applicant, with number DE 198 44 720.5.

The distinction made in the preceding discussions to the cited document DE 196 36 965 A1 is not to be understood as that the possibilities described there for the training of places local Field enhancement in the electrode configuration in this invention would be excluded. Rather, they may be in addition to the invention Realized features and also be quite beneficial. One An example is the facilitation of the ignition of a single discharge at the start of operation the discharge lamp, especially in such electrode configurations, not already performing the same function Have a corner or peak in the meanders. For this purpose, the embodiments directed.

Another aspect of the invention relates to particular embodiments for the electrode surface in the areas between the meanders. Here are the Zwischenmäanderbereichen example in the already mentioned Sinusform the straight pieces or the middle part of straight pieces between the individual bows, mathematically so meant the zero crossings or inflection points. These areas correspond to a certain extent the boundaries between the discharge structures two sides of the same meandering shape and can according to the invention carried out so be that they broaden a discharge structure into these areas to make it difficult or impossible.

The first possibility in this regard is a targeted change the granularity of a layer applied to the electrode, in particular Fluorescent layers are suitable. It should be in the Zwischenmäanderbereich a coarser-grained phosphor than in the meandering arcs to get voted. The meandering bows can also be completely fluorescent.

Another possibility with the same goal is a variation of the Layer thickness of a dielectric layer located on the electrode. The Dielectric layer should then be thicker in the intermediate meander area than in the remaining area. In the case of cathodes, it is also possible here, the rest Form areas without any dielectric layer.

As already stated, the invention also relates to a combination of a discharge lamp with a corresponding ballast. Here is the ballast according to the invention for the already described pulsed Wirkwirkinopopplungsverfahren suitable or designed. On the possible power control function in this context or, in the continuous or approximately continuous case, dimming function is already been received.

From the point of view of the ballast, it has turned out to be a well-practicable way to select a unipolar active power input. This means, that applied to the discharge lamp at the active power pulses outer Tension, of small due to technical parasitic effects Exceptions except, always has the same sign. this means not necessarily that of the current flowing through the discharge lamp is unipolar. Rather, there may be intentional flashbacks in the Discharge lamp come with corresponding reversed current sign, but in the unipolar case, not immediate consequence of an external Lamp voltage are.

Two further parallel applications filed by the same applicant on the same filing date relate to operating procedures and ballasts for particular also the discharge lamp according to the present invention, the preferably be considered here. It is referred to the German Parallel applications file numbers 19839336.9 and 19839329.6 from 08/28/1998. There are each a ballast according to a Flußwandlerprinzip with one for producing a flashback without bipolar outer Lamp voltage designed operating method or a ballast according to a combined barrier / Flußwandlerprinzip with similar direction described.

On the other hand, especially for the electrode configurations, where both electrode types ([temporary] anode and [temporary] cathode) have a meandering shape, the bipolar operation particularly suitable. The reason for this is first the geometric symmetry of Electrode configuration. However, for a suitability for the bipolar Operation to cover all electrodes with a dielectric layer (two-sided dielectric hindrance). As a result, are also from discharge physics View the electrodes similar and take over time alternating both the role of a temporary anode and cathode.

An advantage of bipolar operation, for example, in a symmetrization the discharge conditions are in the lamp. With that particular problems caused by asymmetric discharge conditions effectively avoided, z. B. ion migrations in the dielectric, which can lead to blackening or the efficiency of the discharge worsening space charge accumulations.

As a ballast for the bipolar operating method comes, for example a modified flux converter into consideration. The modifications are aimed at it for a direction reversal of the voltage pulse in the secondary circuit causing primary circuit current in the transformer of the flux converter to care. This is generally easier than appropriate Electrotechnical measures for direction reversal on the secondary circuit side hold true.

In particular, the transformer can for this purpose two primary circuit side windings have, each associated with one of the two current directions are so used for a primary circuit only one of the two directions become. This means that the two primary circuit side windings be applied alternately with electricity. For example, this can be done by using two clocking switches in the primary circuit, each clocking the current through an associated one of the two windings. Thus, each of the two current directions is its own tact switch and a own primary circuit side winding of the transformer assigned.

When a ballast according to the invention at an AC power source used, it may be advantageous with respect to the two primary circuit side Current directions to use two storage capacitors, the half-period alternately charged from the AC power source become. So it will become the half cycles of a sign for one of the storage capacitors and the half-cycles the other sign used for the other storage capacitor. From these two storage capacitors then the currents for one direction each. This can be done together with the described double execution of the primary circuit winding of the transformer but it is not really necessary here. Rather, a single primary circuit side winding by appropriate Switch alternately powered by the two storage capacitors be, each storage capacitor each associated with a current direction is. To power the storage capacitors from the AC power source a corresponding rectifier circuit can be used, the details of which will be readily apparent to those skilled in the art.

Description of the drawings

Figur 1

eine schematische Darstellung einer Elektrodenkonfiguration mit sinusförmigen Anoden und Kathoden;

Figur 2

eine Variante zu der Elektrodenkonfiguration aus Figur 1,

Figur 3

eine schematische Darstellung einer weiteren Elektrodenkonfiguration mit rechteckwellenförmigen Anoden und Kathoden,

Figur 4

eine weitere schematische Darstellung einer Elektrodenkonfiguration mit sägezahnförmigen Anoden und Kathoden,

Figur 5

eine weitere schematische Darstellung einer Elektrodenkonfiguration mit halbkreiswellenförmigen Anoden und Kathoden,

Figur 6

ein schematisches Schaltdiagramm eines Vorschaltgeräts, das für die bipolare Betriebsverfahrensvariante geeignet ist, mit Entladungslampe; und

Figur 7

ein Diagramm mit Meßkurven für die äußere Spannung an und den Strom durch die Entladungslampe beim Beleuchtungssystem nach Figur 6.

In the following, some exemplary embodiments of electrode configurations according to the invention will be explained with reference to the accompanying figures, wherein the illustrated individual features may also be essential to the invention in other combinations. In detail shows:

FIG. 1

a schematic representation of an electrode configuration with sinusoidal anodes and cathodes;

FIG. 2

a variant of the electrode configuration of Figure 1,

FIG. 3

a schematic representation of another electrode configuration with square wave anodes and cathodes,

FIG. 4

a further schematic representation of an electrode configuration with sawtooth-shaped anodes and cathodes,

FIG. 5

a further schematic representation of an electrode configuration with semicircular anodes and cathodes,

FIG. 6

a schematic circuit diagram of a ballast, which is suitable for the bipolar operating method variant, with discharge lamp; and

FIG. 7

a diagram with curves for the external voltage and the current through the discharge lamp in the illumination system of Figure 6.

FIG. 1 is a schematic representation of an electrode configuration represented by anodes 1 and cathodes 2, the single strip alternating and substantially parallel to each other. From a right and a left straight fitting apart, have all anodes 1 and cathode 2 on a sinusoidal meandering shape, wherein next adjacent Anodes 1 with each other and next adjacent cathodes 2 in-phase with each other and nearest neighboring anodes and cathodes in turn run in opposite phases.

In FIG. 1, upward-facing arcs 3 of the sinusoidal shape are shown as maxima and down-facing sheets 4 referred to as minima, so meet accordingly Cathode maxima 3 on anode minima 4 and vice versa, d. H. lie respectively next to each other opposite. Accordingly, the lie Make the highest field strength between a maximum of 3 and a Minimum 4.

At these points, initially form individual discharge structures, the not shown here. With sufficient power input are all preferred locations occupied by a respective single discharge structure. According to the invention now leads to a further increase in power supply, for example, by increasing the amplitude of the to the discharge lamp applied external stress, to a broadening of the respective single discharge structures from the range of immediate maxima 3 and Minima 4 out. In this case, by a corresponding power control device of a ballast, the power will be increased until the single discharge structures at the border areas between the maxima 3 and the minima 4, ie in the vicinity of the turning points, arrived are. This results in a dimming area, which is completely continuous by a Curtain-like broadening of the individual discharge structures go through can be. Reference is made to the already cited parallel application directed.

FIG. 1 also shows the already described geometric parameters half period length SL, minimum discharge distance d _min and maximum discharge distance d _max . In this case, the half-period length SL corresponds to the control range of the mentioned dimming function by the width of the discharge structure can be adjusted. The minimum discharge distance corresponds to the distance between a nearest adjacent maximum 3 and minimum 4. However, the maximum discharge distance does not correspond to the distance between a maximum 3 and a minimum 4, which respectively point to opposite sides. Rather, the maximum discharge distance d _max corresponds to the discharge distance at the outer limits of the control length SL. The adjacent half-periods of the sine wave do not belong to the control length SL and thus also do not define a larger discharge distance d _max because they are used for discharges to the respective electrodes adjacent to each other on the opposite side (or not used for discharge at edge electrodes).

A largely identical structure is shown in FIG. 2, but in the field 5 of the turning points between the maxima 3 and the minima 4 by a recess in the drawn line a reinforcement of the present there dielectric layer should be indicated.

Namely, there are in all embodiments shown here Anodes 1 and the cathodes 2 symmetrically, d. H. not distinguishable from each other. Accordingly, both types of electrodes with a dielectric Covered layer. The areas 5 in FIG. 2 correspond to a reinforced one Layer thickness of the dielectric.

Also the already described with the phosphor Grain connected Variants of a special structuring of these Zwischenmäanderbereiche 5 are possible here.

With regard to the so-called first variant of the invention results in the figures practically no different representation; you would have to get in Figure 1 only one in the layer thickness alternating dielectric coating the anodes 1 and cathodes 2 or an alternating coating and non-coating.

An alternative meandering shape is shown in FIG. 3, namely a rectangular wave-like one Shape of the anodes 1 and cathodes 2. Accordingly, the maxima 3 and the minima 4 not localized in this example but correspond a half-period of the respective electrode strip.

In this example, nose-like projections 6 are accordingly on the Maxima 3 and minima 4 provided, the respective adjacent minima 4 or maxima 3 are facing.

These nose-like projections 6 facilitate the initial ignition of Discharge structures and put the discharge structures centric in the in this example, extended areas of maximum field between the Electrode strips fixed, as long as the power supply does not cause widening the discharge structures over the entire half-period width leads.

Also in Figure 3, the mentioned geometric sizes are shown. The half-period length SL corresponds to the longitudinal extension of the maxima 3 or minima 4. The minimum discharge distance d _min corresponds to the distance between the described nose-like projections 6, whereas the maximum discharge distance corresponds to the discharge distance in the adjacent straight region of the electrodes. In this figure, obviously, the minimum discharge distance d _{min is} only slightly smaller than the maximum d _max .

However, a lighter ignition can also by the meandering form as such take place, as the example in Figure 4 shows a sawtooth shape.

Here are the reference numerals 3 and 4, the respective meander of the sawtooth referred to, ie the areas around a maximum and minimum. The Maxima and minima themselves each correspond to a point corner 7, the thus the function of the ignition relief in the same way as the already having on the basis of Figure 3 discussed nose-like projections 6.

Again, in FIG. 4, the geometrical reference quantities SL, d _min and d _max mentioned several times are drawn in, the explanation here being analogous to FIG.

Of course, also in this embodiment, at the meander areas, the here the middle range of each straight section of track correspond to the sawtooth shape, measures as in the example be provided from Figure 2. However, this is not shown separately.

Figure 5 shows semicircular wave electrode paths, i. the shape of everyone Electrode corresponds to a sequence of semicircles, which alternately mirror images with respect to the longitudinal axis of the respective electrode track to each other are added such that the upwardly facing semicircular arches 3 as Maxima and the downward semicircular arches 4 are called minima can be. In other words, the electrode tracks can be in Figure 5 from which arise in Figure 1 by thinking that each Sine half-wave was replaced by a suitable in-phase half-rice.

For the geometric quantities minimum discharge distance d _min , maximum discharge distance d _max and half period length SL, the following dimensions (in mm) apply to the exemplary embodiments in FIGS. 1, 2, 3, 4 and 5: example d _min d _max SL FIG. 1 5 8th 9 FIG. 2 5 6 6 FIG. 3 5 6 8th FIG. 4 6 10 17 FIG. 5 4 8th 5

In the overall comparison of the electrode configurations illustrated in Figs. 1-5 4 shows a particularly favorable ignition behavior out.

The example of FIG. 3 is less favorable for various reasons. first, because of the relatively large capacity through the over a relative wide area close to each other extending electrode strips. On the other hand is here, apart from the respective nose 6, in the area of extended Maxima 3 and Minima 4 no further distinct location dependency the discharge conditions, therefore, this structure for power control initially poorly suited. However, this could be through other measures than by a variation of the discharge distance - such as in the examples of Figures 1, 2 and 4 - created such inhomogeneity be, for example, by a variation of the electrode width. Only then is the half-period width SL to be referred to as the control length. For this will turn to the already cited parallel application for power control directed.

The sawtooth shape in FIG. 4 has opposite the sinusoidal shape in FIGS and 2 again the disadvantage that through the corners 7 of the sawtooth shape also on the anode side a discharge structure - in the bipolar case of current anode side - there is a certain current concentration. to Optimization of the overall efficiency of the discharges and the discharge lamp However, it is desirable to minimize the individual discharges as far as possible expand and as few or as small areas with increased To create charge carrier concentrations.

Thus, the double sinusoidal shape shown in Figs favorable compromise with regard to the efficiency of the discharges, the Total capacity, the power control characteristics, the achievable surface luminance and the uniformity of this luminance.

The semicircular waveform shown in FIG. 5 is distinguished from the sinusoidal shape shown in FIGS. 1 and 2 by lower gradients in the range of the control length SL, which has a positive effect on the power controllability, ie the dimming behavior. Therefore, an exemplary embodiment based on the electrode configuration shown in FIG. 5 will be explained in more detail below. It is a flat lamp with a discharge vessel (not shown), which is formed of a bottom and a front plate and a peripheral frame. The plates are made of glass of thickness 2 mm and dimensions 105 mm by 137 mm. The frame height and width are each 5 mm. The inner surface of the bottom plate is 78 mm by 110 mm. On the bottom plate, the electrode configuration of Figure 5 is arranged and covered with a glass solder layer (not shown) of thickness about 150 microns (two-sided dielectrically impeded discharge). Therefore, this flat lamp is also suitable for the bipolar operating method variant. In addition, a light-reflecting layer of Al ₂ O ₃ or TiO _{2 is} applied to the bottom plate and the frame. This is followed by a three-band phosphor layer on all inner surfaces. The discharge vessel is filled with xenon at a pressure of approx. 13 kPa. In unipolar operation and a voltage pulse frequency of 80 kHz can be with the peak voltage as a control variable, the widths of the (not shown) delta-shaped partial discharges in the range of the respective control length SL influence. In this way, when the peak voltage is increased from 1.39 kV to 1.49 kV, the average power consumption can be increased from 7 W to 10 W.

More details on the shape and structure of the pulsed operation dielectrically impeded discharges generated characteristic partial discharges under different operating conditions can be found in the already cited WO 94/23 442.

The electrode configurations shown here are all provided for flat radiators, as used for example in the earlier application WO 98/43277 are described. Regarding further technical Details are otherwise referred to the aforementioned parallel application Dimmable discharge lamp for dielectrically handicapped Discharges ", with the reference DE 198 44 720.5.

Figure 6 shows a schematic circuit diagram of a ballast, which is designed for the bipolar operating method variant. Thus, external voltage pulses of alternating polarity are applied to the dielectrically impeded discharge lamp L, for example of the type described with reference to FIG. For this purpose, the transformer T has two primary windings, which are shown in Figure 6 with opposite winding sense. Each of the primary windings is electrically connected in series with an associated switching transistor T _Q with its own control device SE. Of course, the two control devices can also be understood as two functions of a uniform control device; is to be symbolized only that the two primary windings are not clocked together, but alternately. Due to the reversal of the winding between the two primary windings, the transformer T generates alternating voltage pulses of opposite polarity in the secondary circuit S when the primary windings are clocked. In summary, in the circuit of FIG. 1, the subassembly of the primary winding W1, the switch _TQ and the control device SE is doubled , wherein by the sense of winding a sign reversal is effected.

FIG. 7 shows corresponding real measuring curves of the outer lamp voltage U _L and of the lamp current I _L. It should be noted here that the measured external lamp voltage U _L is composed of the voltage of the actual pulse and the voltage of the natural oscillation of the secondary circuit. The latter, however, has at least no decisive influence on the discharge. Rather, what is decisive are the actual voltage pulses which cause the corresponding lamp current pulses of the ignition and the back ignition and finally result in the already disclosed in WO 94/23442 active power pulse mode. Both the ignition pulses of the external lamp voltage and the lamp current pulses of the ignition and the reignition can be seen that it is a bipolar operating method.

Claims (27)

1. Discharge lamp having a discharge vessel filled with a discharge medium, a strip-shaped cathode (2) and a strip-shaped anode (1) as well as a dielectric layer between at least the anode (1) and the discharge medium, the anode (1) being distinguished from the cathode (2), characterized in that the anode (1) runs in a meandering shape such that the spacing between the cathode (2) and the anode (1) is modulated by the meandering shape.
2. Discharge lamp according to Claim 1, in which the cathode (2) runs essentially in a straight line.
3. Discharge lamp according to Claim 1 or 2, in which a plurality of cathodes (2) and a plurality of anodes (1) are arranged alternately in individual strips.
4. Discharge lamp according to Claims 2 and 3, in which the meandering shapes of anodes (1), which run on both sides of a cathode (2), run in phase locally relative to one another, such that the points of minimum spacing between the cathode (2) and the respective anodes (1) alternate along the cathode (2).
5. Discharge lamp having a discharge vessel filled with a discharge medium, a strip-shaped cathode (2) and a strip-shaped anode (1) as well as a dielectric layer between at least the anode (1) and the discharge medium, characterized in that the cathode (2) and the anode (1) run in a meandering shape, the meandering shapes running in phase oppposition locally relative to one another such that the spacing between the cathode (2) and the anode (1) is modulated by both meandering shapes.
6. Discharge lamp according to Claim 5, in which a plurality of cathodes (2) and a plurality of anodes (1) are arranged alternately in individual strips.
7. Discharge lamp according to one of the preceding claims, in which the meandering shape(s) essentially has/have a sinusoidal course.
8. Discharge lamp according to one of the preceding claims, in which the meandering shape(s) essentially has/have a sawtooth course.
9. Discharge lamp according to one of the preceding claims, in which the meandering shape(s) essentially has/have a rectangular course.
10. Discharge lamp according to one of the preceding claims, in which the meandering shape(s) essentially has/have a course in the shape of semicircular waves.
11. Discharge lamp according to one of the preceding claims, in which it holds for the quantitative ratio of a difference between a maximum striking distance d_max separating the electrodes (1, 2) in half a period length (SL) of the meandering shape and a minimum striking distance d_min separating the electrodes (1, 2) in the half period length (SL) to this half period length (SL) that: (d_max-d_min) /SL≤0.6, preferably (d_max-d_min) /SL≤0.5, particularly preferably (d_max-d_min)/SL≤0.4.
12. Discharge lamp according to one of the preceding claims, in which it holds for the ratio of a minimum striking distance d_min to a maximum striking distance d_max that: 0.3<d_min/d_max<0.9, preferably 0.4<d_min/d_max<0.9, particularly preferably 0.5<d_min/d_max<0.9.
13. Discharge lamp according to one of the preceding claims, in which the cathodes (2) have points (6, 7) for local field reinforcement.
14. Discharge lamp according to one of the preceding claims, in which electrode regions (5) between the meanders are coated with a more coarsely grained fluorescent material, and the adjacent meanders of the same electrode (1, 2) are coated with a more finely grained fluorescent material.
15. Discharge lamp according to one of Claims 1-13, in which electrode regions (5) between the meanders are coated with a more coarsely grained fluorescent material, and the adjacent meanders of the same electrode (1, 2) are free from fluorescent material.
16. Discharge lamp according to one of the preceding claims, in which electrode regions (5) between the meanders are coated with a thicker dielectric layer and the adjacent meanders of the same electrode (1, 2) are coated with a thinner dielectric layer.
17. Discharge lamp according to one of Claims 1-15, in which electrode regions (5) between the meanders are coated with a dielectric layer and the adjacent meanders of the same electrode (1, 2) are free from this dielectric layer.
18. Lighting system having a discharge lamp according to one of the preceding claims and a ballast which is designed for pulsed coupling of active power into the discharge lamp.
19. Lighting system according to Claim 18, in which the ballast has a power control device for controlling the power of the discharge lamp by varying an electric parameter of the pulsed coupling of active power into the discharge lamp.
20. Lighting system according to Claim 18 or 19, in which the ballast is designed for a unipolar coupling of active power.
21. Lighting system according to one of Claims 18-20, in which the ballast is a flux transformer for injecting an external voltage pulse from a primary circuit via a transformer into a secondary circuit with the discharge lamp, in order to effect striking and an inner counter-polarization in the discharge lamp, and has a switching device which is designed to interrupt the flow of current after starting on the primary side through the transformer so as to isolate the secondary circuit in order to permit oscillation of the secondary circuit in order to remove the charge effecting the external voltage across the discharge lamp and to lead to restriking by means of the inner counter-polarization in the discharge lamp.
22. Lighting system according to one of Claims 18-20, in which the ballast is a combined flyback/forward converter and has a switching device in a primary circuit which is designed to interrupt the flow of current on the primary-circuit side through a transformer in order to inject an external voltage pulse into a secondary circuit with the discharge lamp, in order to effect striking and a counter-polarization in the discharge lamp, and then to restart the flow of current on the primary-circuit side through the transformer in order by means of a back-e.m.f. pulse to remove the charge, effecting the external voltage across the discharge lamp, from the discharge lamp in order to effect restriking in the discharge lamp with the aid of the inner counter-polarization.
23. Lighting system according to Claim 18 or 19, in which the ballast comprises a powered primary circuit (P), a secondary circuit (S) containing the discharge lamp (L), and a transformer (T) connecting the primary circuit (P) to the secondary circuit (S), the ballast being designed for the purpose of applying to the discharge lamp (L) external voltages (U_L) with signs alternating from voltage pulse to voltage pulse.
24. Lighting system according to Claim 23, in which the direction of the current (I_W1) on the primary-circuit side in the transformer (T) alternates from voltage pulse to voltage pulse.
25. Lighting system according to Claim 24, in which the transformer has two windings (W1) on the primary-circuit side which are each assigned to one of the two current directions.
26. Lighting system according to Claim 25, in which the primary circuit has two switches (T_Q) which respectively clock the current through one of the two windings (W1).
27. Lighting system according to one of Claims 18-26, in which the primary circuit is supplied from an AC source which alternately charges two storage capacitors in half periods, each storage capacitor respectively being assigned to one of the two current directions.

Images