Patent ID: 7170237

Claim:
Device for operation of a high pressure discharge lamp, comprising: a high pressure discharge lamp having a discharge vessel made of silica glass in which there is a pair of opposed electrodes arranged at a distance of at most 2.0 mm from each other and containing at least 0.20 mg/mm 3 of mercury and 10 −6 μmole/mm 3 to 10 −2 μmole/mm 3 of a halogen; and a feed device which supplies an alternating current to the discharge lamp, wherein the feed device supplies the alternating current with a frequency in the range from 60 Hz to 1000 Hz as a stationary operating frequency and inserts a low frequency into the alternating current of said stationary operating frequency, said low frequency being lower than the stationary frequency and in a frequency range from 5 Hz to 200 Hz, having an inserted length of from one half period to five periods, and an inserting period of from 0.01 seconds to 120 seconds, and wherein the feed device is adapted to change the parameters of the low frequency according to changes of the operating voltage of the discharge lamp.