Abstract: The invention relates to a dimming circuit arrangement for operating a high-pressure sodium lamp L with controllable color temperature. The lamp is supplied with current pulses having a controllable duty cycle D. A change in the color temperature can be achieved through a change .DELTA.D in the duty cycle D and a simultaneous change .DELTA.P in the power supplied to the lamp, while the relation .DELTA.D/.DELTA.P>0 is satisfied.

Abstract: A circuit arrangement for starting and operating gas discharge lamps with current of higher frequency comprises an electronic ballast unit connected to a direct voltage input source (2). An electronic switching element (3), which is controlled by a control device (8), is connected in series with an inductive element (4), and the discharge lamp (5). The lamp current flows through the inductive element from which a voltage is derived which is supplied to the control device as a supply direct voltage supply via a rectifier (14) and a smoothing capacitor (16). A first connection terminal of the smoothing capacitor is connected through a first ohmic resistor (18) to a first terminal of the direct voltage input source and a second connection of the capacitor is connected through the lamp (5) to a second terminal of the direct voltage input source.

Abstract: In a circuit arrangement for starting and operating a high-pressure gas discharge lamp (8) by means of a voltage converter comprising at least one semiconductor switch (5, 6), which can be switched periodically to the conductive and to the non-conductive state by a control unit (32, 33, 34) in such a manner that the lamp receives a pulsatory supply current having an operating duty cycle between 0.1 and 0.7, the control unit (32, 33, 34) switches the semiconductor switch (5, 6) upon starting of the lamp (8) in such a manner that the duty cycle upon starting (starting duty cycle) is increased with respect to the operating duty cycle.

Abstract: A circuit arrangement for operating at least one gas discharge lamp (5) with a periodically varying lamp current and adapted for connection to an alternating voltage source with a period N. The circuit is provided with a controlled semiconductor switch (3) and a control circuit for switching the controlled semiconductor switch with a switching period S in dependence upon a comparison between an actual signal proportional to the lamp current and a nominal signal derived from a voltage across the switching transistor (3).

Abstract: A circuit arrangement for A.C. operation of gas discharge lamps comprises a full-wave rectifier (1) connected to an alternating voltage source. The direct voltage is supplied to a combinatorial circuit part (3 to 8) in the form of a direct voltage converter, to which is connected a bridge circuit (9) which comprises four thyristors. The transverse branch of the bridge circuit includes the lamp (5). The full-wave rectifier (1) is followed by a smoothing capacitor (2) and an electronic switching element (14) is connected parallel to the bridge circuit (9). The switching element is switched to the conducting state in the vicinity of the zero passages of the input alternating voltage. As a result shortcircuits in the bridge circuit are avoided.

Abstract: A circuit arrangement for igniting and operating gas discharge lamps comprises a choke coil (1) connected between a lamp (2) and an a.c. supply source. The choke coil has an inductance L and an ignition device (3) is connected to the lamp. A capacitor (9) having a capacitance C is connected in parallel with at least a part of the choke coil in order to pass an ignition current to the lamp that is higher than the normal lamp operating current. The relationship betweeen the capacitive reactance of the capacitor and the inductive reactance of the choke coil is 1/.omega.C>3.omega.L.