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Improving Gas Discharge Lamps

Patent

US8456099

Owner

OSRAM GmbH

Filing Date

October 12, 2006

Priority Date

October 17, 2005

Portfolio

Lighting - OSRAM

Intro

HID (high intensity discharge) lamps, which can be used in projectors, have the problem that structures grow on the two electrodes of these lamps over the course of the operating time. Back-burning of the electrodes increases the distance between the electrodes and therefore also the operating voltage of the HID lamp. The increase in the operating voltage may be up to approximately 1 V per hour. This invention relies on the ingenious idea to produce a current pulse such that structures are removed. The patent has amongst others a German counterpart.

Claims

1. A method for operating a gas discharge lamp, in which the shape of at least one electrode of the gas discharge lamp is changed, wherein in this pro...
  1. A method for operating a gas discharge lamp, in which the shape of at least one electrode of the gas discharge lamp is changed, wherein in this process by changing the lamp current for a predeterminable duration, at least one current pulse is generated such that structures which have grown on the at least one electrode are at least partially removed, the current pulse being generated for the duration of at least one entire half cycle of the AC voltage or the alternating current if the gas discharge lamp is fed AC voltage or alternating current, or the current pulse being generated with a pulse duration of between approximately 0.1 s and approximately 5 s if the gas discharge lamp is fed DC voltage or direct current, wherein the electrical pulse is generated during a runup phase of the gas discharge lamp. 
  2. The method as claimed in claim 1, wherein the amplitude of the current pulse and/or the profile of the current pulse and/or the duration of the current pulse and/or the time at which the current pulse is generated is/are produced as a function of at least one operational parameter of the gas discharge lamp.  
  3. The method as claimed in claim 2, wherein a detected lamp voltage of the gas discharge lamp and/or a detected profile of this lamp voltage are used as operational parameters.  
  4. The method as claimed in claim 3, wherein the amplitude of the current pulse and/or the profile of the current pulse and/or the duration of the current pulse and/or the time at which the current pulse is generated is/are produced as a function of a lamp voltage threshold value being exceeded or undershot.  
  5. The method as claimed in claim 1, wherein the amplitude of the current pulse and/or the profile of the current pulse and/or the duration of the current pulse and/or the time at which the current pulse is generated is/are produced such that the structures which have grown on at least one electrode are removed and the current load on an electronic ballast connected to the gas discharge lamp remains essentially unchanged.  
  6. The method as claimed in claim 1, wherein the duration of the current pulse is less than two seconds, in particular less than one second.  
  7. The method as claimed in claim 1, wherein, at least for a predeterminable duration, a peak value for the current pulse is greater than a maximum permissible current value for an electronic ballast which is electrically connected to the gas discharge lamp.
  8. The method as claimed in claim 1, wherein the profile of the lamp voltage of the gas discharge lamp is detected over the duration of the current pulse, and the amplitude of the current pulse and/or the profile of the current pulse and/or the duration of the current pulse is/are generated as a function of the detected profile of the lamp voltage.
  9. The method as claimed in claim 1, wherein the amplitude of the current pulse and/or the profile of the current pulse and/or the duration of the current pulse and/or the time at which the current pulse is generated is/are produced such that the rate of rise of the lamp voltage and/or the value for the lamp voltage once the duration of the current pulse has elapsed correspond to predeterminable values.
  10. The method as claimed in claim 1, wherein the amplitude of the current pulse and/or the profile of the current pulse and/or the duration of the current pulse and/or the time at which the current pulse is generated is/are produced as a function of a thermal load on an electronic ballast which is electrically connected to the gas discharge lamp. 
  11. The method as claimed in claim 1, wherein the gas discharge lamp is fed AC voltage or alternating current, and the current pulse for the duration of in each case at least one half cycle causes structures which have grown on to melt on that electrode which is operated as the anode.  
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Abstract

The invention relates to a method for operating a gas discharge lamp, in which the shape of at least one electrode of the gas discharge lamp is change...
The invention relates to a method for operating a gas discharge lamp, in which the shape of at least one electrode of the gas discharge lamp is changed, in which by changing the lamp current for a predeterminable duration, at least one current pulse is generated such that structures which have grown on the at least one electrode are at least partially removed, the current pulse being generated for the duration of at least one entire half cycle of the AC voltage or the alternating current if the gas discharge lamp is fed AC voltage or alternating current, and the current pulse being generated with a pulse duration of between approximately 0.1 s and approximately 5 s if the gas discharge lamp is fed DC voltage or direct current.
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