DC/AC converter for the ignition and the supply with alternating current of a gas and/or vapour discharge lamp

Claim 1

A DC/AC converter for the ignition and the supply with alternating current of a gas- and/or vapour discharge lamp, which converter has two input terminals which are to be connected to a direct voltage source, the two input terminals being connected to each other through a first series arrangement which comprises at least a first transistor, a load circuit which - in the operating condition - comprises the lamp, and a capacitor, the load circuit together with at least the capacitor being shunted by a second transistor, and whereby the load circuit is provided with a circuit element shunting the lamp as well as with a reactive circuit element in series with the lamp, whilst a control device is present by means of which the two transistors are alternately rendered conductive and which is provided withatiming circuit having a variable time constant in order to ensure that the frequency at which the two transistors are alternately rendered conductive, when the converter is switched on but with the lamp not yet ignited, is different from that in the operating condition of the lamp so that the starting current is limited, characterized in that the load circuit includes in series with the lamp a primary winding of a transformer, and in that the timing circuit is connected between two terminals of a secondary winding of the transformer and the time constant of this timing circuit is voltage-dependent.