Method for operating a discharge lamp and projection arrangement

Patent metadata

Field	Value
Publication number	US-9788401-B2
Application number	US-201414532022-A
Country	US
Kind code	B2
Filing date	Nov 4, 2014
Priority date	Nov 13, 2013
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

Various embodiments provide a projection arrangement. The projection arrangement may include a discharge lamp; and a ballast for the discharge lamp. The ballast is designed to provide, during operation of the projection arrangement, a lamp current in the form of alternating current and having an average frequency and a preset waveform, which has a preset commutation scheme, to the discharge lamp. The preset commutation scheme is preset by a preset time sequence of commutations of the lamp current. The ballast is designed to provide the lamp current in such a way that the preset commutation scheme of the lamp current is deviated from repeatedly with at least one preset intervening time period by at least one DC phase with a preset time duration.

First claim

What is claimed is:

1. A method for operating a discharge lamp comprising two electrodes for a projection arrangement, the method comprising:
a ballast supplying, during operation, a lamp current in the form of alternating current and having an average frequency and a preset waveform, wherein the lamp current has a preset commutation scheme, to the discharge lamp, wherein the preset commutation scheme is preset by a preset time sequence of commutations of the lamp current, and wherein the preset commutation scheme is deviated from repeatedly with at least one preset intervening time period by at least one DC phase with a preset time duration; and
pre-setting the at least one preset intervening time period to at most 50 seconds using the at least one DC phase with the preset time duration.

2. The method of claim 1 ,
wherein the at least one presettable intervening time period is at most 25 s.

3. The method of claim 2 ,
wherein the at least one presettable intervening time period is at most in the single-digit seconds range.

4. The method of claim 3 ,
wherein the at least one presettable intervening time period is in the milliseconds range.

5. The method of claim 4 ,
wherein the at least one presettable intervening time period is at least 5 milliseconds.

6. The method of claim 1 ,
wherein the at least one DC phase lasts between 5 milliseconds and 100 milliseconds.

7. The method of claim 1 ,
wherein at least one parameter of the at least one DC phase is preset by a measured current intensity of the lamp current.

8. The method of claim 1 ,
wherein the at least one parameter represents a duration of the at least one DC phase and/or the at least one presettable intervening time period, wherein the at least one parameter is preset in such a way that the duration of the at least one DC phase is longer and/or the at least one presettable intervening time period is shorter than for the second measured current intensity.

9. The method of claim 8 ,
wherein the at least one parameter represents a duration of the at least one DC phase and/or the at least one presettable intervening time period, wherein, for a first measured current intensity, which has a magnitude which is less than a second measured current intensity, the at least one parameter is preset in such a way that the duration of the at least one DC phase ( 20 ) is longer and/or the at least one presettable intervening time period is shorter than for the second measured current intensity.

10. The method of claim 1 ,
wherein the at least one DC phase is provided by virtue of the fact that at least one commutation in accordance with the commutation scheme is implemented as double commutation.

11. The method of claim 1 ,
wherein the preset commutation scheme is deviated from by a plurality of successive DC phases, which have the at least one preset intervening time period with respect to one another, wherein in each case two temporally successive DC phases have opposite polarities.

12. The method of claim 1 ,
wherein the preset commutation scheme is deviated from by a plurality of successive DC phases, which have the at least one preset intervening time period with respect to one another, wherein the DC phases each have an identical phase duration.

13. The method of claim 1 ,
wherein the preset commutation scheme is configured in such a way that a current intensity profile of the lamp current in accordance with this commutation scheme is configured in such a way that a preset time interval on average has no DC component.

14. The method of claim 1 ,
wherein the preset commutation scheme is periodic.

15. The method of claim 14 ,
wherein the profile over time of the current intensity in accordance with this periodic commutation scheme is repeated a plurality of times periodically during the at least one preset intervening time period.

16. The method of claim 1 ,
wherein the average frequency of the lamp current is at least 180 Hz.

17. The method of claim 16 ,
wherein the average frequency of the lamp current represents an integral multiple of 60 Hz.

18. The method of claim 1 ,
wherein intervening time periods between in each case two successive commutations in accordance with the preset commutation scheme are at least sometimes unequal.

19. A projection arrangement, comprising:
a discharge lamp; and
a ballast for the discharge lamp, which ballast is designed to provide, during operation of the projection arrangement, a lamp current in the form of alternating current and having an average frequency and a preset waveform, wherein the lamp current has a preset commutation scheme, to the discharge lamp, wherein the preset commutation scheme is preset by a preset time sequence of commutations of the lamp current, wherein the ballast is designed to provide the lamp current in such a way that the preset commutation scheme of the lamp current is deviated from repeatedly with at least one preset intervening time period by at least one DC phase with a preset time duration.

20. The projection arrangement of claim 19 ,
wherein the at least one preset intervening time period is at most 50 seconds.

Assignees

• Osram Gmbh

Inventors

• Czichy Marc
• Magg Norbert

Classifications

• H05B41/2928

  for protecting the lamp against abnormal operating conditions · CPC title

• H05B41/16 Primary

  in which the lamp is fed by DC or by low-frequency AC, e.g. by 50 cycles/sec AC {, or with network frequencies} · CPC title

• H05B41/3928

  for high-pressure lamps, e.g. high-intensity discharge lamps, high-pressure mercury or sodium lamps · CPC title

• H05B41/38

  Controlling the intensity of light · CPC title