Patent ID: 7248000

Claim:
An operating device for operating high-pressure gas discharge lamps, the operating device comprising: an apparatus which is suitable for triggering starting of a connected high-pressure gas discharge lamp, and a setting device which is suitable for limiting a lamp current of connected high-pressure gas discharge lamps to a limit current value, characterized in that the operating device further comprises: a lamp state detector which is designed such that, in a time window which follows on from starting and is shorter than a start-up phase, it evaluates a running voltage of a connected high-pressure gas discharge lamp or a value proportional thereto and from this derives a state variable which is suitable for distinguishing between a cold and a hot high-pressure gas discharge lamp, and a control device which inputs the limit current value to the setting device as a function of the state variable, and further characterized in that the lamp state detector contains a subtracter having two inputs and one output, the value of the running voltage at a time in the time window being applied to one input, a predetermined rated value being applied to the other input, and a difference being provided at the output of the subtracter, from which difference the lamp state detector forms the state variable.