Patent ID: 6927539

Claim:
Lamp Device for operating a high pressure discharge lamp, comprising: an ultra-high pressure discharge lamp having a silica glass discharge vessel in which there is a pair of opposed electrodes at a distance from each other of at most 1.5 mm, at least 0.15 mg/mm 3 of mercury and bromine in a range of 10 −6 μmol/mm −2 to 10 −2 μmol/mm 3 ; and a feed device which supplies an alternating current with rectangular waves to the discharge lamp and thus operates the discharge lamp, wherein the feed device is operative for controlling the discharge lamp such that the operating voltage is increased by reducing the operating frequency of the discharge lamp by a given amount when the operating voltage of the above described discharge lamp falls below a set lower boundary value, and wherein the feed device is also operative for controlling the discharge lamp such that the operating voltage is reduced by increasing the operating frequency of the discharge lamp by a given amount when the operating voltage of the above described discharge lamp exceeds a set upper boundary value.