Abstract: A method is described for driving a gas discharge lamp (1), specifically a HID lamp, more specifically a metal halide lamp, most specifically a metal halide lamp with an aspect ratio larger than 3 or even 4. The lamp is supplied with a commutating DC current having a duty cycle (D) and an average current intensity (IAV) at a certain electrical output power. The method comprises the step of varying the average current intensity (IAV) and the electrical output power in order to vary the color temperature of the lamp. Preferably, the average current intensity (IAV) is changed by changing the duty cycle (D), and the electrical output power is varied in relation to the average current intensity (IAV).

Abstract: A method for driving a metal halide lamp (1) is described, the method comprising the step of generating a light controlling DC electric field E with a desired direction and a desired strength inside the lamp such as to obtain a desirable ion distribution inside the lamp. The lamp is supplied with a commutating current with a DC component, preferably having a constant current intensity and a duty cycle differing from 50%. By setting the duty cycle, it is possible to set a certain average value of the lamp current, allowing the efficacy and/or color temperature of the lamp to be influenced.