Abstract: To control the color temperature of a sodium high-pressure discharge lamp, preferably having a sodium and xenon fill, which may also include mercury, without essentially affecting the color rendition index of the emitted light, or the light flux or intensity of light radiation emitted, the lamp is operated under pulsed conditions, in which the instantaneous pulse power of recurring power pulses, separated by a holding phase to prevent extinction of the lamp, is controlled. Preferably, the overall energy of any one of said power pulses and the intervening holding pulse is maintained essentially constant, for example by varying the frequency of sub-pulses or oscillations of which the sequential power pulses are constituted. A frequency and power controllable oscillator (1) is connected to the lamp (3) through a series LC network to effect such control, thereby permitting adjustment of color temperature and matching of the light output to selective color reflectivity of illuminated objects.

Abstract: To provide for optimum control of a sodium high-pressure discharge lamp operating under saturated operating conditions, such that the lamp will be operating stably and providing light output which is an optimum with respect to the color rendition index (Ra), light output or luminous flux, and color temperature, without regard to manufacturing tolerances or variations in power supply voltage, the energy supplied to the lamp is controlled with respect to a quotient formed of lamp voltage and lamp current (V.sub.L /I.sub.L), said quotient being determined with respect to optimum light values. The power supply for the lamp (3) either is a stabilized output voltage power supply (22) in which the output current is controlled, or an oscillator (32) providing bursts or power pulses (10, 10') formed of oscillations (11).

Abstract: A high-pressure sodium vapor lamp with elevated color temperature, high light yield and improved color rendering properties for general illumination purposes uses sodium or sodium amalgam with mole fractions x.sub.Na >0.9 as the arc media. The lamp power supply supplies pulses with a duty cycle .GAMMA.of 0.01>.GAMMA.>0.1 with alternating polarity, or with mole fractions x.sub.Na >0.95 even at uniform polarity, respectively.