Abstract: A projection system for image reproduction by means of at least one lamp (10) as well as a sensor (30) for generating a sensor signal for monitoring changes in the luminous flux generated by said at least one lamp (10) and for compensating these changes through a suitable control of the image reproduction is described. The projection system comprises a device (31; 32; 36, 37) for eliminating substantially periodic interference components from the sensor signal generated by the at least one sensor (30; 301, 302, 303). These interference components may be generated by an optical component such as in particular a color modulator (12) of the projection system. The invention thus renders possible an at least substantially interference-free compensation of fluctuations in the luminous flux generated by the lamp (10), for example owing to an unstable arc discharge, also in those color systems in which the positioning of the sensor (30) in the projection system is non-critical.

Abstract: A method for driving a gas discharge lamp (1) is described, wherein electric first DC power is provided at a relatively high voltage and a relatively low current. Said first power is converted down to second DC power at a relatively low voltage and a relatively high current. Said second power is fed to a gas discharge lamp, preferably via a commutator. The conversion of said first power to said second power is performed in at least two steps, a first one of such steps including the step of converting down said first power to an intermediate DC power at an intermediate DC voltage lower (VM) than said first DC voltage but higher than said second DC voltage. A downconverter device (30) for use in a driving apparatus (10) for a gas discharge lamp (1) is described. The downconverter device comprises at least two downconverter units (31, 32) connected in series, for converting down said intermediate DC power to said second power.

Abstract: A circuit arrangement for igniting and operating a high-pressure discharge lamp includes input terminals for the connection of a supply source and output terminals for the connection of the lamp. A switching circuit operates the lamp at a nominal lamp voltage Vla during stable lamp operation and generates an open circuit voltage Vo at the output terminals before the lamp is ignited. A control circuit for controlling the switching circuit is provided with a device BM for limiting the voltage at the output terminals. A transition detection circuit M detects the transition from a glow discharge to an arc discharge.