Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Plural cathode and/or anode discharge device load
Reexamination Certificate
2000-03-17
2001-10-02
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Plural cathode and/or anode discharge device load
C315S246000, C313S497000, C313S607000
Reexamination Certificate
active
06297599
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a lighting arrangement equipped with a dielectric barrier discharge lamp comprising
a gas tight discharge vessel enclosing a discharge space and containing a filling,
a first main electrode and a second main electrode,
a dielectric sheet situated between the first main electrode and the discharge space,
a circuit arrangement coupled to the main electrodes for igniting and operating the dielectric barrier discharge lamp, comprising
a first circuit part for generating an operating voltage that is present between the two main electrodes.
The invention also relates to a dielectric barrier discharge lamp.
A lighting arrangement as described above is known from U.S. Pat. No. 5,343,114. The dielectric barrier discharge that is present in the discharge space during operation of the known lighting arrangement is a high very suitable for the generation of excimers or ozone. The filling typically contains one or more noble gases, a metal halide or a metal vapor and traces of other gases for excimers generation or a mixture of oxygen or air with other gases for the generation of ozone. A discharge is maintained by applying a high voltage between the first and second main electrode. The dielectric sheet that covers the first main electrode serves to distribute the discharge over the electrode area and to interrupt the discharge at an early stage due to the build up of an electrical field by charge accumulation on the dielectric sheet. The electrical field counteracts the electrical field present between the two main electrodes. Due to the early interruption of the discharge, the dielectric barrier discharge lamp (further also called lamp) has to be operated with a high frequency AC operating voltage and the discharge is far from equilibrium. This latter property of the discharge together with a suitable filling allows efficient generation of excimers. Excimers are a source of UV radiation. This UV radiation can for instance be used in photochemical processes. Dielectric barrier discharges are also often used to generate ozon. Alternatively, by making use of a suitable luminescent material, this UV radiation can be converted into visible radiation. A disadvantage of the known lighting arrangement, however, is the very high amplitude of the operating voltage necessary to reignite the dielectric barrier discharge lamp at the beginning of each half period of the operating voltage. In fact this high amplitude of the operating voltage raises the requirements that the circuit arrangement for operating the lamp has to meet to such an extent, that it forms the main impediment for a much more widespread use of the lighting arrangement.
SUMMARY OF THE INVENTION
According to the invention the dielectric barrier discharge lamp further comprises auxiliary electrode means and the circuit arrangement further comprises a second circuit part coupled to the auxiliary electrode means for generating an auxiliary discharge in the discharge space.
The auxiliary electrode means are so constructed that the second circuit part only needs to apply an auxiliary voltage with a relatively low amplitude to it in order to generate the auxiliary discharge. The auxiliary discharge generates free electrons and other charged particles. Because of the presence of these free electrons and other charged particles a discharge between the two main electrodes can be established by applying an operating voltage with only a relatively low amplitude between them. In other words the dielectric barrier discharge lamp can be operated making use of an operating voltage with only a relatively low amplitude.
The auxiliary electrode means may comprise a number n of electrode bodies, n being bigger than or equal to 2 . In that case the second circuit part may comprise means for generating n−1 auxiliary voltages that are present between neighbouring electrode bodies and that during operation cause a discharge to be present between neighboring electrode bodies. Preferably all these n−1 auxiliary voltages have the same amplitude, so that the second circuit part only needs to generate one voltage that is applied to each of the n−1 pairs of neighbouring electrode bodies.
Alternatively, the auxiliary electrode means may comprise a number n of electrode bodies, while the second circuit part comprises means for generating n auxiliary voltages that are present between the electrode bodies and the surrounding discharge space during ignition. During operation these voltages generate discharges that are known as corona discharges. Preferably all these n auxiliary voltages have the same amplitude, so that the second circuit part only needs to generate one voltage that is applied to each of the n electrode bodies. The number n of electrode bodies can in this case be equal to 1. An important advantage of embodiments in which one or more corona discharges are used as auxiliary discharge, is that the first and the second circuit part can be integrated.
The electrode bodies can be mounted in or on the dielectric sheet. Good results have been obtained for embodiments of a lighting arrangement according to the invention, wherein the electrode bodies are evenly distributed over the dielectric sheet. During stationary operation the auxiliary discharge maintained by the electrode bodies is also evenly distributed over the dielectric sheet. As a result the homogeneity of the main discharge remains intact.
More in particular in case the auxiliary discharge consists of Corona discharges, the electrode bodies may protrude from the dielectric sheet into the discharge space.
Alternatively, the electrode bodies may be separated from the discharge space by means of the dielectric sheet. In this case the electrode bodies are not in contact with the filling. Depending on the nature of the filling and the material that is used to construct the electrode bodies this construction may prevent deterioration of the electrode bodies or changes in the composition of the filling.
In a preferred embodiment one of the main electrodes comprises n electrode segments and the electrode bodies of the auxiliary electrode means are formed by the electrode segments. In this preferred embodiment both the main electrodes and the auxiliary electrodes are formed out of the same amount of electrode material. In case n=1 there is only one electrode body comprised in the auxiliary electrode means and this electrode body is formed by one of the main electrodes.
Alternatively, one of the main electrodes may comprise n electrode segments while the electrode bodies are separate from the electrode segments and each of the electrode bodies is electrically connected to an electrode segment. This construction of the main electrodes and the auxiliary electrodes allows the auxiliary voltage to be applied via the electrode segments, so that the electrical connections can be relatively simple. In this construction n can be chosen equal to 1, in other words the dielectric barrier discharge lamp may comprise only one electrode body in the auxiliary electrode means, while this electrode body is connected to a main electrode that consists of one segment only.
In a further preferred embodiment of a lighting arrangement the second circuit part comprises selection means for selecting a number of electrode bodies and for coupling the auxiliary voltage to the selected electrode bodies only. During operation of this embodiment the auxiliary discharge will only be present in the vicinity of the selected electrode bodies. As a consequence also the main discharge between the two main electrodes will only be established in the vicinity of the selected electrode bodies. The selection means can thus be used to control the light output of the lamp by determining the size of the discharge between the two main electrodes. Alternatively the selection means can be used for color variation, by coating different parts of the wall of the discharge vessel with different luminescent materials and by subsequently establishing the discharge between the two main
Dirscherl Jürgen
Klein Markus
Scholl Robert P.
Halajian Dicran
Lee Wilson
U.S. Philips Corporation
Wong Don
LandOfFree
Dielectric barrier discharge lamp with a segmented electrode does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dielectric barrier discharge lamp with a segmented electrode, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dielectric barrier discharge lamp with a segmented electrode will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2576225