Patent ID: 7663324

Claim:
A control circuit for driving a gas discharge lamp, in particular a fluorescent lamp (FL), including a controllable converter ( 2 ) for converting a DC voltage to an AC voltage and having two feed lines ( 3 , 4 ) which are connected on the AC-voltage side to the converter ( 2 ), and between which feed lines the gas discharge lamp is connectable, an inductor (L 1 ), a first capacitance (C 1 ) and a first controllable switching element (T 1 ) being connected in series in the feed lines ( 3 , 4 ), wherein the feed lines between the inductor (L 1 ) and the first capacitance (C 1 ) are electrically connected via a second controllable switching element (T 2 ), the inductor (L 1 ) and the first capacitance (C 1 ) being bridged via a first diode (D 1 ), and including a control unit (ST 2 ) which is connected to the first switching element (T 1 ), to the second switching element (T 2 ) and to the converter ( 2 ), and which is provided for driving the switching elements (T 1 , T 2 ) in synchronism with the AC voltage of the converter ( 2 ) and is designed such that the second switching element (T 2 ) is opened after a closed phase for starting the gas discharge lamp at such a point in time that the AC voltage at the inductor (L 1 ), which is set in the resonant circuit comprising the inductor (L 1 ) and the parasitic capacitance (C 4 ) of the second switching element (T 2 ), and the AC voltage of the converter ( 2 ), approximately in phase in terms of their extrema, are added to provide a starting voltage.