Abstract: A fluorescent lamp (2), in particular a backlight lamp of a display device, is supplied with an alternating voltage, a frequency and an amplitude of which being greater during ignition than during normal operation of the lamp. The voltage (V) across the lamp and the current (I) through the lamp are measured to provide a measured voltage value and a measured real lamp current value. From the alternating voltage there is derived a voltage (V2). The measured voltage value is multiplied by the sum of the measured real lamp current value and the derived voltage. The multiplication result (P=V*(I+V2)) is compared with a reference value (Ref), which results in a difference or error value. The error value is used to control the frequency and the amplitude of the alternating voltage (V), such that the error value is minimized.

Abstract: An emergency lighting device comprises an illumination lamp for illuminating an area and an energy storage unit for providing electrical energy for powering the lamp. According to the invention, the energy storage unit comprises an ultra-capacitor for storing the electrical energy. As the ultra-capacitor shows hardly any deterioration over time, extensive, e.g. periodical testing of the emergency lighting device during its lifetime can be omitted. A charging arrangement for charging the ultra-capacitor in the emergency lighting device is described.

Abstract: A system (100A, 100B, 200, 300) for operating three gas discharge lamps (1A, 1B, 1C) using a common power source comprises three branches (110, 120, 130) connected in parallel between a first input node (A) and a second input node (102), wherein each branch comprises a lamp. The system comprises current equalizing means for ensuring that the currents in all branches are mutually substantially equal. The current equalizing means comprise two equalizing transformers (151, 152), wherein an equalizing transformer (151; 152) has one winding (114; 125) connected in series with one lamp (1A; 1B) and has another winding (124; 135) connected in series with another lamp (1B; 1C).

Abstract: End of life of a lamp operated by a ballast circuit is detected by detecting whether the amplitude of a DC current through the lamp is outside of a range between two predetermined boundary values.