Patent ID: 8098020

Claim:
A circuit arrangement for operating a discharge lamp (LA) with an inverter, which is designed to provide a signal (S D ) with a predeterminable frequency at its output; at least one terminal for the discharge lamp (LA), at least one lamp inductor (L D ), which is coupled between the output of the inverter and the at least one terminal for the discharge lamp (LA); at least one capacitor (C l ), which is coupled to the lamp inductor (L D ); a drive apparatus ( 18 ) for driving the inverter with the signal (S D ) with the predeterminable frequency; a control apparatus ( 10 , 12 , 14 , 16 ) for controlling a control parameter, which is dependent on the lamp current (I L ), to a predeterminable value as a result of a change in the predeterminable frequency, the control apparatus ( 10 , 12 , 14 , 16 ) having a first time constant; the discharge lamp (LA) having a second time constant, with which it reacts to a change in the predeterminable frequency with a change in a parameter which is dependent on the lamp current (I L ); the circuit arrangement, owing to the temperature-dependent UI characteristic of the discharge lamp (LA) and the frequency-dependent UI characteristic of a resonant circuit, which comprises at least the capacitor (C l ) and the lamp inductor (L D ), having at least one range with a first and a second stable working point and, between the first and the second stable working point, an unstable working range in the family of UI characteristics, characterized in that the first time constant is greater than or equal to the second time constant; and the drive apparatus ( 18 ) is designed to vary the predeterminable frequency during the operation of the discharge lamp (LA) in such a way that the circuit arrangement is operated in the unstable working range.