Patent ID: 7193375

Claim:
An electronic ballast for at least one discharge lamp having preheatable electrodes, the ballast comprising: an ac voltage supply terminal, a rectifier connected to the supply terminal, a converter for generating a higher-frequency supply power for the discharge lamp from the supply power, rectified by the rectifier, of the supply terminal, at least one pump circuit for improving the power factor of the ballast by drawing energy from the ac voltage supply terminal, and characterized in that: the ballast further comprises a preheating transformer having a primary side and a secondary side, wherein the ballast and the preheating transformer are designed to supply a preheating power to the preheatable electrodes of the lamp during a preheating phase before the lamp is ignited, wherein the preheatable electrodes are connected on the secondary side of the preheating transformer, the ballast is designed to operate the converter during preheating with a frequency that is raised by comparison with an open circuit resonant frequency of the ballast, in order to supply the primary side of the preheating transformer, and wherein the ballast further comprises a sequential control system for controlling the operation of the converter, wherein the sequential control system is designed so that the transition from the preheating phases, with the converter frequency raised by comparison with a continuous-operation frequency, to the ignition of the discharge lamp (LA 1 , LA 2 ) takes at most 10 ms.