EP0839436B1 - Method for operating a lighting system and suitable lighting system therefor - Google Patents

Abstract

The invention pertains to a method for operating a lighting system with an incoherently-emitting radiation source, in particular a discharge lamp (14) that emits UV, IR or visible-range radiation, by means of dielectrically inhibited discharge, and to a lighting system suitable therefor. The electrodes (16-20), which are arranged side by side and separated from each other and the interior of the discharge vessel (15) by dielectric material (21), are alternatingly connected to the two poles (23, 24) of a voltage source (27). In operation the voltage source (27) supplies a series of voltage pulses separated by quiescent periods. According to the invention, this produces inside the discharge vessel (15) a spatial discharge (26) which in the regions between electrodes of different polarity (16, 17; 17, 18; 18, 19; 19, 20) is at a distance from the surface of the inside wall of the discharge vessel (15). Substantial advantages are less stress on the wall of the discharge vessel and greater efficiency in generating radiation.

Description

The invention relates to a method for operating a lighting system with an incoherently emitting radiation source, in particular Discharge lamp, by means of dielectric barrier discharge according to the Preamble of claim 1. Furthermore, the invention relates to one for this Operating method suitable lighting system according to the preamble of claim 12.

Under incoherently emitting radiation sources are UV (U ltra v Iolet) - and IR (I nfra r ot) emitters as well as discharge lamps which emit visible light in particular, to understand.

Industrial applicability

Such radiation sources are suitable, depending on the spectrum of the emitted radiation, for general and auxiliary lighting, such as home and office illumination or backlighting of displays, such as LCDs (L iquid C rystal D isplays), for the transport and signal lighting, for UV radiation, for example disinfection or photolytics, and for IR radiation, for example for drying paints.

State of the art

WO 94/23442 describes a method for operating an incoherently emitting Radiation source, in particular discharge lamp, by means of dielectric disabled discharge disclosed. The operating procedure sees one Sequence of voltage pulses before, the individual voltage pulses through Dead times are separated. The advantage of this pulsed mode of operation is a high efficiency of radiation generation.

EP 0 363 832 describes a UV high-power lamp with pairs of electrodes connected to both poles of a high voltage source. The electrodes are from each other and from the discharge space of the Radiator separated by dielectric material. Such electrodes are hereinafter referred to as "dielectric electrodes". In addition, the electrodes are arranged side by side, whereby area-like discharge configurations with relatively flat discharge vessels let it be realized. An AC voltage is applied to the dielectric electrodes in the order of magnitude of several 100 V to 20000 V. Frequencies in the range of technical alternating current up to a few kHz placed such that there is essentially only a sliding electrical discharge in the area of the dielectric surface.

The main disadvantage is that sliding discharges in particular place a thermal load on the surface, which is why cooling channels for dissipating the heat from the dielectric are also proposed. Due to the unavoidable, substantial heat generation of this discharge type, the efficiency for generating radiation, in particular in the UV and VUV (V acuum U ltra v Iolet) range is limited. In addition, sliding discharge causes chemical processes on the surface, thereby shortening the life of the lamp.

Presentation of the invention

The object of the invention is to eliminate these disadvantages and a method to operate a lighting system, which both through a flat discharge vessel as well as through efficient production characterized by radiation.

This object is achieved by the characterizing features of claim 1 solved. Further advantageous features are in the Sub-claims explained.

Another object of the invention is to provide a lighting system which is suitable for the operating method. This object is achieved according to the invention by the characterizing features of claim 12 solved.

The basic idea of the invention is in the interior of the discharge vessel with dielectric electrodes arranged next to one another generate spatial discharge in the areas between electrodes opposite polarity a distance from the surface of the inner wall of the discharge vessel. While in the prior art one Variety of sliding discharges along the surface of the dielectric Serve generation of UV radiation, the invention proposes the use one that separates from the dielectric surface, spatially within extended discharge before the discharge vessel.

The advantages achieved thereby are firstly a higher efficiency of generation of UV or VUV (V acuum U ltra v iolet) radiation and hence a lower heat generation. In contrast to the prior art, no cooling liquid is required for heat dissipation. On the other hand, the discharge type according to the invention results in a significantly lower thermal and chemical wall load than is the case with surface sliding discharges. An extension of the life of the discharge vessel is consequently achieved. In addition, according to the invention, a more uniform, area-like, spatially diffuse luminance distribution can be realized between the electrodes. The latter offers considerable advantages over optically imaging lighting or radiation tasks, such as, for example, in photolithographic applications, in comparison to the channel-shaped sliding discharges. Here, diffuse luminance distributions directly improve process efficiency. In this regard, lighting patterns such as the conventional channel-shaped lighting structures are undesirable.

The method according to the invention now provides for those arranged side by side dielectric electrodes with a series of voltage pulses supplying voltage source to connect. The individual voltage pulses are separated from each other by break times. Surprisingly it has been shown that this procedure does not only involve radiation is generated with high efficiency, but that completely beyond that Unexpectedly, a spatial discharge is generated inside the discharge vessel that is in the areas between electrodes of different polarity a distance from the surface of the inner wall of the discharge vessel having.

Starting from a repetitive voltage pulse, pulse width becomes and pause time selected so that the spatial, discharge occurs partially from the dielectric surface. Typical pulse widths and pause times are between 0.1 µs and 5 µs or in the range between 5 µs and 100 µs, corresponding to one Pulse repetition frequency in the range between 200 kHz and 10 kHz.

The optimal values for the pulse width and the pause time are in individual cases depends on the specific discharge configuration, i.e. of type and Pressure of the gas filling and the electrode configuration. The electrode configuration results from the type and thickness of the dielectric, the area and shape of the electrodes and the electrode spacing. According to the The voltage signal to be applied is such a discharge configuration choose that a discharge separates from the dielectric surface that sets a maximum radiation yield at the desired electrical Power density. In principle, those disclosed in WO 94/23442 are also Sequences of voltage pulses are suitable. The amount of voltage pulses is typically between approx. 100 V and 10 kV. The shape of the current pulse is determined by the voltage pulse shape and the discharge configuration.

Two or more elongated ones are suitable for the electrode configuration Electrodes made of electrically conductive material, e.g. metallic wires or Strips also applied to the outside of the vessel wall, for example evaporated, narrow layers. The electrodes are preferred arranged parallel and equidistant to each other. This is important to everyone Discharges between the neighboring electrodes have the same conditions to ensure. This makes a large-scale and homogeneous Illumination ensured. It will also be more appropriate in this way Pulse sequence achieves optimal radiation efficiency. The lateral dimensions - i.e. the diameter of the wires or widths of the strips - from anode or cathode can be different.

The operating method according to the invention is suitable for a large number of possible ones Discharge vessel geometries, especially for all those in the EP 0 363 832 A1. It does not matter whether the discharge vessel contains a gas filling and is sealed gastight, e.g. with discharge lamps, or whether the discharge vessel is open on both sides and is flowed through by a gas or gas mixture, e.g. in photolytic Reactors. The only decisive factor for the mode of operation is that the dielectric Electrodes are arranged side by side. Side by side means here that neighboring electrodes of different polarity as it were lie on one side of the discharge zone.

The electrodes can be arranged in a common plane, e.g. on an outside of a wall of the discharge vessel -vtl. additionally covered with a dielectric protective layer - or directly into the Wall embedded. It is also possible to use different electrodes preferably parallel planes on one side of the discharge zone to arrange. For example, the are consecutive Electrodes of changing polarity depending on the polarity in one of two against each other staggered levels, such as disclosed in DE 40 36122 A1.

In the case of flat discharge vessels, the wall serves to arrange the Electrodes advantageously the base or top surface. Level discharge arrangements are particularly suitable for large, flat lighting purposes, e.g. for backlighting of display boards or LCD screens, or for radiation purposes, e.g. Photolithography or curing of paints.

In addition to a flat arrangement, curved discharge vessels are also suitable, for example tubular. Tubular open on both sides and by one Arrangements through which gas or gas mixture flow are particularly suitable as photolytic reactors. In its simplest execution is one tubular arrangement through a dielectric tube, e.g. with circular Cross section formed. The electrodes are at least on or arranged in a part of the outside or the wall of the tube. The discharge builds up inside the tube during operation out. In a variant, the inner wall of the tube is in the area of the Electrodes with a dielectric layer serving as an optical reflector Mistake.

A continuation of the tubular arrangement consists of two concentric ones Pipes with different diameters and from on or in arranged the inner wall of the tube with the smaller diameter Electrodes. The discharge forms in the room during operation between the two pipes.

The inner wall of the discharge vessel can be covered with a layer of fluorescent material be provided, which converts the UV or VUV radiation of the discharge into light. A variant with a white light-emitting fluorescent layer is particularly suitable for general lighting.

The selection of the ionizable filling and possibly the phosphor layer depends on the application. Noble gases are particularly suitable, e.g. Neon, argon, krypton and xenon as well as mixtures of noble gases. However, other fillers can also be used, e.g. all those who are usually used in light production, in particular Mercury (Hg) and rare gas-Hg mixtures as well as rare earths and their halides.

The lighting system is completed by a voltage source, whose output poles are connected to the electrodes of the discharge vessel are and which delivers the specified sequence of voltage pulses during operation.

Description of the drawings

Fig. 1a

den Querschnitt einer Entladungsanordnung mit zwei nebeneinander angeordneten dielektrischen Elektroden,

Fig. 1b

den Längsschnitt der Entladungsanordnung aus Figur 1a,

Fig. 2

die Stirnansicht der Entladungsanordnung aus Figur 1a im erfindungsgemäßen Betrieb,

Fig. 3

einen Ausschnitt aus dem während des Betriebs gemäß Figur 2 an den Elektroden gemessenen zeitlichen Verlauf von Strom I(t) und Spannung U(t),

Fig. 4

wie Figur 2, aber mit geänderter Elektrodengeometrie,

Fig. 5

einen Ausschnitt aus dem während des Betriebs gemäß Figur 4 an den Elektroden gemessenen zeitlichen Verlauf von Strom I(t) und Spannung U(t),

Fig. 6a

den Querschnitt eines für den erfindungsgemäßen Betrieb geeigneten Beleuchtungssystems,

Fig. 6b

die Draufsicht des Beleuchtungssystems aus Figur 6a.

The invention is explained in more detail below with the aid of some exemplary embodiments. Show it

Fig. 1a

3 shows the cross section of a discharge arrangement with two dielectric electrodes arranged next to one another,

Fig. 1b

the longitudinal section of the discharge arrangement of Figure 1a,

Fig. 2

the front view of the discharge assembly of Figure 1a in operation according to the invention,

Fig. 3

2 shows a section of the time profile of current I (t) and voltage U (t) measured on the electrodes during operation according to FIG. 2,

Fig. 4

as in FIG. 2, but with a modified electrode geometry,

Fig. 5

4 shows a section of the time profile of current I (t) and voltage U (t) measured on the electrodes during operation according to FIG. 4,

Fig. 6a

the cross section of a lighting system suitable for the operation according to the invention,

Fig. 6b

the top view of the lighting system of Figure 6a.

Figures 1a and 1b show a schematic representation of the transverse or Longitudinal section of a discharge arrangement 1. Around the essence of the invention To be able to explain better and to promote clarity is the Presentation deliberately reduced to the essential. The discharge arrangement 1 consists of a cuboid-like, transparent discharge vessel 2 and two parallel strip-shaped electrodes 3, 4 on the outer wall of the discharge vessel 2 are arranged. At this point again pointed out that for the operating method according to the invention of course, similar discharge arrangements with more than two dielectric electrodes arranged next to each other Polarity are suitable. The discharge vessel 2 is made of glass. It consists of a lid 5 and a bottom 6, both of which are trough-shaped are formed and face each other in mirror image, two the longitudinal axis of the discharge vessel 2 defining side walls 7, 8 and two End walls 9,10. Xenon is located inside the discharge vessel 2 with a filling pressure of approx. 8 kPa. The two electrodes 3, 4 are off Made of aluminum foil. They are centric and parallel on the outside of the lid 5 glued on. The lid 5 is made of 1 mm thick glass and also acts as a dielectric layer between the two electrodes and the discharge 11, shown here only roughly schematically, which forms during operation in the interior of the discharge vessel 2. According to the invention is the discharge 11 in the area between the two electrodes 3,4 through a dark zone 12 (in longitudinal section, Figure 1b, not recognizable) separated from the inner wall of the lid 5. I.e. the discharge 11 has a distance from the surface of the inner wall in the area mentioned on.

FIGS. 2 and 4 show photographic recordings of the discharge arrangement from Figures la and 1b. To explain the recordings the corresponding reference numbers already introduced above are used. The two recordings were each made with a view of the front wall 9 in Direction of the longitudinal axis. They differ only in the electrode geometry. The width of the strip-shaped electrodes 3, 4 and their mutual distance is 3 mm or 4 mm in the first case and 1 mm or 10 mm in the second case. Especially in the first case (Figure 2, above) the electrodes 3, 4 can be clearly seen. You stand out as dark areas from the wall of the lid 5, the same as the opposite Wall of the floor 6 due to reflected and scattered Fluorescent light from the glass appears bright. The length of the electrodes is 35 mm each. In both cases, particularly clearly in the second case (Figure 4), it can be seen that the self-lighting of the discharge in the area between the two electrodes 3, 4 through a dark zone 12 is separated from the inner wall of the cover 5. I.e. the discharge 11 has a distance from the surface of the inner wall in the area mentioned on. Viewed in the direction of the longitudinal axis of the discharge arrangement 1, the discharge 11 has a channel-like or trough-like appearance (Not recognizable in Figures 2 and 4 due to the viewing direction, cf. Figures 1a and 1b).

If less power is coupled into the discharge arrangement - e.g. by reducing the voltage amplitude -, the continuous, trough-shaped breaks Discharge structure in individual structures, which however as shown in Figure la, lift off the dielectric surface. The individual structures have a delta-like shape (Δ), which are each in Widen direction (current) anode. In the case of changing polarity the voltage pulses of a bilaterally dielectric discharge there is a visual overlay of two delta-shaped structures.

FIGS. 3 and 5 each show a section of the time profile of voltage U (t) and current I (t) measured on the electrodes during operation according to FIGS. 2 and 4. A comparison of both figures shows the influence of the electrode geometry on voltage and current. The most important electrical quantities are summarized in the following table.

U _p , T _U , f _U , w and P mean the height of the voltage pulses (based on the voltage during the break), the width of the voltage pulses (full width at half the height), the pulse repetition frequency, the electrical energy per pulse or the average electrical power coupled in over time.

FIGS. 6a and 6b schematically show the cross section or the top view (viewing direction on the bottom side) of a lighting system 14 suitable for the operation according to the invention. The lighting system 14 consists of a flat discharge vessel 15 with a rectangular base area and five strip-shaped electrodes 16-20 and a voltage source 27, which supplies a sequence of voltage pulses during operation. The discharge vessel 15 in turn consists of a rectangular base plate 21 and a trough-like cover 22. The base plate 21 and the cover 22 are connected in a gas-tight manner in the region of their peripheral edges and thus enclose the gas filling of the discharge lamp 14. The gas filling consists of xenon with a filling pressure of 10 kPa. The electrodes 16-20 have the same widths and are applied to the outer wall of the base plate 21 parallel to one another and equidistantly. This is important in order to ensure the same conditions for all discharges between the neighboring electrodes. With a suitable pulse sequence, an optimal radiation efficiency or uniformity of the luminance distribution is thereby achieved. For this purpose, the electrodes 16-20 are alternately connected to the two poles 23, 24 of a voltage source. Ie the electrode 16 and the two electrodes 18 and 20 next to the predecessor are connected to a first pole 23 of the voltage source. In contrast, the two electrodes 17 and 19 located between them are connected to the other pole of the voltage source. A phosphor layer 25 is sprayed onto the inner wall of the lid 22 and the bottom 21, which the VUV (V acuum U ltra v iolet) - or UV (U ltra v iolet) radiation of the discharge, only very schematically shown 26 in ( visible) light.

Claims (12)

1. Method for operating an incoherently emitting radiating source (1; 14), in particular a discharge lamp (14), by means of dielectrically obstructed discharge, having an at least partially transparent discharge vessel which is closed (2; 15) and filled with a gas filling or open and through which a gas or gas mixture flows and which is made from electrically nonconductive material and has electrodes (3, 4; 16-20) which are separated from one another and from the interior of the discharge vessel (2; 15) by dielectric material (5; 21), characterized in that the electrodes are arranged next to one another and are connected in an alternating fashion to the two poles (23, 24) of a voltage source supplying a sequence of voltage pulses, and in that the individual voltage pulses are respectively separated from one another by off periods, so that as a result there is generated in the interior of the discharge vessel (2; 15) a spatial discharge (11; 26) which has a spacing from the surface of the inner wall of the discharge vessel in the regions between electrodes of different polarity (3, 4; 16, 17; 17, 18; 18, 19; 19, 20).
2. Method according to Claim 1, characterized in that the pulse width is in the range between 0.1 µs and 10 µs.
3. Method according to Claim 2, characterized in that the pulse width is preferably in the range between 0.5 µs and 5 µs.
4. Method according to Claim 1, characterized in that the pulse repetition frequency is in the range between 1 kHz and 1 MHz.
5. Method according to Claim 4, characterized in that the pulse repetition frequency is preferably in the range between 10 kHz and 100 kHz.
6. Method according to Claim 1, characterized in that the voltage pulses have a semi-sinusoidal shape.
7. Method according to Claim 1, characterized in that the pulse height is in the range between approximately 100 V and 10 kV.
8. Method according to one or more of the preceding claims, characterized in that the wall (5; 21) of the discharge vessel (2; 15) itself serves as dielectric between the electrodes (3, 4; 16-20) and the discharge (11; 26).
9. Method according to Claim 8, characterized in that the electrodes comprise electrically conductive strips (3, 4; 16-20) which are arranged next to one another on the outside of the wall (5; 21).
10. Method according to Claim 9, characterized in that if the number of the strips (16-20) is greater than two, the arrangement of the strips on the outside of the wall (21) is equidistant.
11. Method according to Claim 1, characterized in that the inside of the wall (21) of the discharge vessel (15) is provided at least partially with a phosphor coating (25) .
12. Lighting system having a radiating source, in particular a discharge lamp (14), and a voltage source (27) which supplies a voltage to the radiating source, the radiation being emitted incoherently by the radiating source (14), which radiating source (14) is suitable for a dielectrically obstructed discharge, having an at least partially transparent discharge vessel which is closed (15) and filled with a gas filling or open and through which a gas or gas mixture flows and which is made from electrically nonconductive material and has electrodes (16-20) which are separated from one another and from the interior of the discharge vessel (15) by dielectric material (21) and are connected to the voltage source (27), characterized in that the electrodes are arranged next to one another and are connected in an alternating fashion to the two poles (23, 24) of the voltage source (27), which voltage source (27) is capable of supplying a sequence of voltage pulses, the individual voltage pulses being respectively separated from one another by off periods, so that as a result there is generated in the interior of the discharge vessel (15) a spatial discharge (26) which has a spacing from the surface of the inner wall of the discharge vessel in the regions between electrodes of different polarity (16, 17; 17, 18; 18, 19; 19, 20).

Images