Abstract: A circuit arrangement comprises four controllable switches (S1, S4) interconnected to form a full bridge. A warm-up operation is carried out in which there is a switch over between the two bridge diagonals (S1, S4; S2, S3) respectively. The gas discharge lamp (EL) is ignited by way of a series resonant circuit (L1, C1) which is coupled to the bridge branch. The actual normal operation is effected by switching over at a low frequency between the switches of the two bridge diagonals (S1, S4; S2, S3), with, moreover, one switch (S1, S2) of the respectively activated bridge diagonal being switched on and off alternately at a high frequency, with this switch (S1, S2) being switched on at the high frequency whenever the current (iL2) flowing by way of the bridge branch has reached a minimum value.

Abstract: Circuit arrangement for igniting and operating gas discharge lamps, in particular high-pressure gas discharge lamps. The circuit arrangement comprises four controllable switches (S1, S4) which are interconnected to form a full bridge, in which a gas discharge lamp (EL) is to be arranged in the bridge branch of the full bridge. After the ignition and operation of the gas discharge lamp (EL), a warm-up operation is carried out in which there is a switch-over between the two bridge diagonals (S1, S4; S2, S3) respectively. The gas discharge lamp (EL) is ignited by way of a series resonant circuit (L1, C1) which is coupled to the bridge branch, with two series-connected switches (S1, S2) of the full bridge being permanently open and the other two switches (S3, S4) being switched on and off alternately at a high frequency.