Patent ID: 8228000

Claim:
A circuit arrangement for operating at least one low-pressure gas discharge lamp, the circuit arrangement comprising: an input comprising a first input connection and a second input connection configured to apply a DC supply voltage; an output comprising a first output connection pair and a second output connection pair configured to connect the at least one low-pressure gas discharge lamp; an inverter, which is coupled to the first input connection and the second input connection, configured to provide an AC supply voltage from the DC supply voltage; a control device configured to drive the inverter and thereby to control the frequency of the AC supply voltage, the control device being configured to initiate a preheating phase once a predetermined preheating criterion has been met, in which preheating phase the inverter is operated at a preheating frequency, and to set the frequency of the AC supply voltage to a starting frequency once a predetermined starting criterion has been met; a resonant circuit comprising a resonant inductor, whose first connection is coupled to the inverter, and whose second connection is coupled to a resonant pole, and comprising a resonant capacitor, which is coupled between the resonant pole and the reference potential of the control device; and a transformer configured to preheat electrodes of the low-pressure gas discharge lamp, which transformer comprises a primary winding, a first secondary winding, which is coupled to the first output connection pair, and a second secondary winding, which is coupled to the second output connection pair; wherein the primary winding of the transformer is connected in series with the resonant capacitor and is connected directly to the reference potential of the control device, and an electrical switch is coupled in parallel with the primary winding of the transformer, which switch has a control connection, which is coupled to the control device, the control device further being configured to transfer the electrical switch into its electrically conducting switching state once the starting criterion has been met.