Method of driving an arc-discharge lamp

1. A method of driving an arc-discharge lamp ( 1 ), which method comprises the steps of:

detecting a mechanically induced fluctuation in luminous flux of the lamp ( 1 ) occurring as a result of a physical displacement of the discharge arc ( 2 );

determining a characteristic ( 43 , 51 , 63 ) of the mechanically induced fluctuation in luminous flux of the lamp ( 1 ); and

adjusting the lamp power on the basis of the determined characteristic ( 43 , 51 , 63 ) to suppress the mechanically induced fluctuation in luminous flux of the lamp ( 1 ).

2. A method according to claim 1 , wherein the step of detecting a mechanically induced fluctuation in luminous flux of the lamp ( 1 ) comprises detecting fluctuations in a frequency range between 5 Hz and 30 Hz.

3. A method according to claim 1 , wherein the mechanically induced fluctuation in luminous flux of the lamp ( 1 ) is detected by monitoring the lamp voltage to obtain a lamp voltage value ( 41 ).

4. A method according to claim 3 , wherein the characteristic ( 43 ) of the mechanically induced fluctuation in luminous flux of the lamp ( 1 ) comprises a lamp voltage modulation envelope ( 43 ), which lamp voltage modulation envelope ( 43 ) is derived from a sequence of lamp voltage values ( 41 ).

5. A method according to claim 1 , wherein a mechanically induced fluctuation in luminous flux of the lamp ( 1 ) is detected by monitoring an acceleration of the lamp ( 1 ) to obtain a lamp acceleration value ( 61 ).

6. A method according to claim 5 , wherein the characteristic ( 63 ) of the mechanically induced fluctuation in luminous flux of the lamp ( 1 ) comprises a lamp vibration value ( 63 ), which lamp vibration value ( 63 ) is derived from a sequence of lamp acceleration values ( 61 ).

7. A method according to claim 1 , wherein the step of adjusting the lamp power comprises applying a phase-shift (φ) to the lamp power, which phase-shift (φ) is determined on the basis of the determined characteristic ( 43 , 63 ).

8. A method according to claim 1 , wherein the characteristic ( 51 ) of the mechanically induced fluctuation in luminous flux of the lamp ( 1 ) comprises a measured light output value ( 51 ) of the lamp ( 1 ).

9. A method according to claim 1 , wherein the step of adjusting the lamp power comprises adjusting the amplitude of the lamp voltage and/or the lamp current on the basis of the determined characteristic ( 43 , 51 , 63 ).

10. A driver ( 3 ) for an arc-discharge lamp ( 1 ), which driver comprises:

a detecting means ( 40 , 50 , 60 ) for detecting a mechanically induced fluctuation in luminous flux of the lamp ( 1 ) occurring as a result of a physical displacement of the discharge arc ( 2 );

a determination unit ( 42 , 50 , 62 ) for determining a characteristic ( 43 , 51 , 63 ) of the mechanically induced fluctuation in luminous flux of the lamp ( 1 ); and

an adjustment unit ( 8 ) for adjusting a lamp power (P C ) on the basis of the determined characteristic ( 43 , 51 , 63 ) to suppress the mechanically induced fluctuation in luminous flux of the lamp ( 1 ).

11. A driver according to claim 10 , wherein the detecting means ( 40 ) comprises a voltage measurement means ( 40 ) for obtaining a lamp voltage value ( 41 ) and/or a light sensor ( 50 ) for obtaining a lamp light output value ( 51 ) and/or a lamp acceleration sensor ( 60 ) for obtaining a lamp acceleration value ( 61 ).

12. A driver according to claim 10 , wherein the determination unit ( 42 , 50 , 62 ) comprises a lamp voltage modulation detector ( 42 ) and/or a light sensor ( 50 ) and/or a lamp vibration determination module ( 62 ).

13. A driver according to claim 12 , wherein the light sensor ( 50 ) is positioned in a base unit of the lamp ( 1 ).

14. A lighting assembly ( 9 ) comprising a high-intensity gas-discharge lamp ( 1 ) and a driver ( 3 ) according to claim 10 for driving the lamp ( 1 ).