Patent ID: 6433490
Filing Date: 2002-08-13
Classification: H05B

Abstract:
In an electronic ballast for at least one low-pressure discharge lamp,an inverter which is connectable to a direct-voltage source, a load circuit which is connected to the inverter and which is configured to contain a lamp and which includes a series resonant circuit, an evaluating circuit arrangement constructed and connected to react to different operating states of such lamp and, in the case of a defect or removal of the lamp, to generate corresponding signals which are used to switch off the inverter, a heating transformer connectable to coils of such lamp, a primary winding of said transformer being connected in series with a switch to an output of said inverter and being connectable to a direct-voltage source if said inverter is switched off on account of a heating-coil defect or removal of the lamp, said switch being clocked in the switched-off condition of said inverter, said evaluating circuit being arranged to evaluate current that flows through at least one of said primary winding and said secondary winding of said heating transformer.