Abstract: An electronic ballast for lamps, which has an input stage that is designed as a SEPIC converter. By operating the SEPIC converter in the mode with a discontinuous current profile, a slow microcontroller can be used for the control.

Abstract: To reduce the noise level of operation of a high-pressure metal halide diarge lamp, the lamp has a rotation-symmetrical discharge vessel (2) which has an inner surface which has a central region which is circular cylindrical and two facing transition regions (12, 13) which are straight-sided right-circular-conical and connect the central circular cylindrical region to extending shaft portions (3, 4) into which the electrodes and connecting foils are sealed. A lamp of this type, when operated from a square-wave power supply has a reduced noise level, particularly in the audio frequency range of between 6 to 20 kHz. A suitable angle between the circular cylindrical portion and the right-conical portion is between 120.degree. and 160.degree., for example about 145.degree..