Electric lamp and discharge devices: systems – Pulsating or a.c. supply
Patent
1995-07-11
1997-02-18
Pascal, Robert
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
315260, 313607, H05B 4100
Patent
active
056044100
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for operating an incoherently emitting radiation source, and more particularly to ultraviolet, infrared and visible light radiators, such as discharge lamps.
BACKGROUND
A discharge is generated within a discharge vessel. The discharge vessel has a dielectric layer disposed between at least one electrode and the discharge, and for this reason this type of discharge is also known as a silent, or quiet or dielectrically impaired discharge, or barrier discharge. Incoherently emitting radiation sources include ultraviolet (UV) and infrared (IR) radiators, as well as discharge lamps that in particular radiate visible light. The invention is suitable for both low-pressure and high-pressure gas fillings and for all gas pressures that are in the range between low and high pressure.
The excitation of such discharges is typically done with the aid of an alternating current, as disclosed for instance in the German Patent Disclosures DE 40 22 279 , Eliasson et al., and DE 42 03 594, Kim and in U.S. Pat. No. 5,117,160, Konda et al. The excitation frequency there is selected within the range between the frequency of the commercial-technical alternating current and several megahertz (DE 40 22 279), or between 20 and 100 kHz (U.S. Pat. No. 5,117,160).
The disadvantage of this mode of operation is that the desired radiation yields are relatively low, at technologically relevant power densities. Typical UV efficiencies are between 10%, for surface power densities of 1 kW/m.sup.2 and 15% at 10 W/m.sup.2 ; see "3. Tagung des Arbeitskreises UV und IR am Lichttechnischen Institut der Universitat Karlsruhe" ["3rd Conference of the UV and IR Study Group at the Light Technology Institute, University of Karlsruhe"] on Oct. 7, 1992, and "Dielectric Barrier Discharges: An Unusual Light Source", M. Neiger, LTI, University of Karlsruhe, Sixth International Symposium on the Science and Technology of Light Sources, Budapest, 1992.
The Invention
The object of the invention is to improve the efficiency of the desired generation of radiation substantially.
Briefly, the fundamental concept of the invention is based on the fact that a dielectrically impeded, or impaired discharge, also referred to as a barrier discharge, is operated by being repetitively pulsed, so that the successive electrical energy introductions are interrupted by time periods T.sub.On --hereinafter called "idle times"--even at high power density in the individual discharge. The lengths of the individual periods of time are a function of the requirement that the introduction of energy, or more precisely the introduction of the effective power, be essentially ended as soon as the introduction of further electrical energy has resulted in a less-efficient conversion into the desired radiation the idle time is ended as soon as the gas filling has relaxed once again enough, respectively, to enable renewed exciting for efficient emission for the desired radiation. Thus, on a temporal average the radiation efficiency is optimized. In this way, efficiencies of 65% and more, for example, in the conversion of electrical energy into UV radiation can be attained, which is an increase multiple times over the conventionally operated, dielectrically impaired discharge.
In the normal situation, this involves a train of identical voltage pulses, or voltage pulses that merely change their polarity; the total number n of voltage pulses is in principle unlimited. For special cases, however, a train of voltage pulses that regularly vary can be used as well. Finally, the pulse train can also be entirely irregular (for example, in special effect lighting, where a plurality of pulses are combined into a cluster such that a particular light effect that is apparent to the human eye is created).
During the pulse periods T.sub.Pn, a voltage pulse U.sub.Pn (t) is applied between the electrodes, and effective power is introduced. Its course over time is not in principle fixed; it can be chosen from various forms, such as: the pulse times T
REFERENCES:
patent: 4645979 (1987-02-01), Chow
patent: 4887002 (1989-12-01), Dobashi et al.
patent: 5117160 (1992-05-01), Konda et al.
patent: 5436532 (1995-07-01), Benard et al.
"Dielectric Barrier Discharges: An Unusual New Light Source" by M. Neiger, TI, University of Karlsruhe, Germany, Sixth International Symposium on the Science and Technology of Light Source, Budapest, 1992; pp. 75-82 No Month .
Hitzschke Lothar
Vollkommer Frank
Pascal Robert
Patent-Treuhand-Gesellschaft fur elektrische Gluhlampen mbH
Vu David H.
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