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1. (WO2007096803) PROCÉDÉ ET MODULE DE COMMANDE D'UNE LAMPE À DÉCHARGE
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

CLAIMS:

1. A method for driving a gas discharge lamp (1), whereby an alternating voltage (U) is applied to the gas discharge lamp (1), the alternating voltage (U) having a first polarity during a first time interval (tfl, tsl) and a second polarity opposite to the first polarity during a second time interval (tf2, ts2), and wherein:
- in a first operation mode, the first time interval (tfl) and the second time interval (tf2) are repeated alternately,
- in a second operation mode, the electrical power (P) being provided to the gas discharge lamp (1) is smaller compared to the first operation mode, and the first time interval (tsl) and the second time interval (ts2) are repeated alternately, whereby, in this second operation mode, the duration of the first time interval (tsl) is at least a multiple of the duration of the second time interval (ts2).

2. The method according to claim 1, wherein during the second operation mode, the duration of the first time interval (tsl) is at least approximately 40 times, preferably at least approximately 100 times, most preferably at least approximately 200 times larger than the duration of the second time interval (ts2).

3. The method according to claim 1 or 2, wherein during the second operation mode, the electrical power (P) being provided to the gas discharge lamp (1) is at least approximately 2 times, preferably at least approximately 4 times, most preferably at least approximately 6 times smaller than the nominal electrical power rating (Pn) of the gas discharge lamp (1).

4. The method according to any of the preceding claims, wherein during the second operation mode, the frequency of the alternating voltage (U) is much smaller than the frequency of the alternating voltage (U) during the first operation mode.

5. The method according to claim 4, wherein during the second operation mode, the frequency of the alternating voltage (U) is equal or less than 100Hz, preferably between 0.1Hz and 90Hz, most preferably between 0.5Hz and 60Hz.

6. The method according to any of the preceding claims, wherein during the second operation mode, the duration of the second time interval (ts2) is smaller than 10ms, preferably smaller than lms, most preferably smaller than 0.1ms.

7. The method according to any of the preceding claims, wherein the electrical power (P) being provided to the gas discharge lamp (1) is reduced directly before or during the transition from the first operation mode to the second operation mode.

8. The method according to any of the preceding claims, wherein the electrical power (P) being provided to the gas discharge lamp (1) is reduced in a number of steps.

9. The method according to any of the preceding claims, wherein during the second operation mode, the electrical power (P) being provided to the gas discharge lamp (1) is reduced to a level leading to a temperature and/or a pressure inside the arc tube (3) of the gas discharge lamp (1) which allows to turn off the gas discharge lamp (1) completely, while maintaining the ability to re-ignite the gas discharge lamp (1) essentially immediately.

10. A driving unit (4) for driving a gas discharge lamp (1) comprising:
a commutation unit (25) for applying an alternating voltage (U) to the gas discharge lamp (1), the alternating voltage (U) having a first polarity during a first time interval (tfl, tsl) and a second polarity opposite to the first polarity during a second time interval (tf2, ts2), a control unit (10) for controlling the commutation unit (25) such that during a first operation mode, the first time interval (tfl) and the second time interval (tf2) are repeated alternately, and such that during a second operation mode the electrical power (P) being provided to the gas discharge lamp (1) is smaller compared to the first operation mode, and the first time interval (tsl) and the second time interval (ts2) are repeated alternately, whereby, in this second operation mode, the duration of the first time interval (tsl) is at least a multiple of the duration of the second time interval (ts2).

11. An image rendering system, particularly a projector system, comprising a gas discharge lamp (1) and a driving unit (4) according to claim 10.

12. An image rendering system according to claim 11, comprising a user interface unit for providing a user request (UR) to the control unit (10) of the driving unit (4), whereby the control unit (10) comprises a signal input (18) for receiving the user request (UR) and which is built up so that it is capable to switch from the first operation mode to the second operation mode and/or from the second operation mode to the first operation mode upon reception of the user request (UR).

13. An image rendering system according to claim 11, which is built up such that it is capable of obtaining a brightness criterion (BC) of an image, and wherein the control unit (10) of the driving unit (4) comprises a signal input (36) for receiving the brightness criterion (BC), and which control unit (10) is built up such that it is capable to switch from the first operation mode to the second operation mode and/or to switch from the second operation mode to the first operation mode according to the brightness criterion (BC).