Patent ID: 7733036

Claim:
Method for driving one or more gas discharge lamps ( 2 ), comprising generating a substantial rectangular high voltage from an input high DC voltage (V+-V−), generating an alternating voltage with respect to a reference voltage (V−) from the rectangular voltage, supplying the alternating voltage to first electrodes ( 4 ) of the lamps, and selectively connecting second electrodes ( 6 ) of the lamps to the reference voltage (V−), characterized in that, for each lamp a current flowing through the lamp is stabilized ( 26 ), the alternating voltage is filtered to provide a filtered voltage, a property of the filtered voltage is measured to provide a control signal, the control signal is used to control the frequency of the rectangular voltage during its generation, and the filtering has a response characteristic which is substantially identical to a response characteristic provided by a lamp when conducting and means for said stabilizing of current flowing through the lamp.