Abstract: A driver (10) for driving a gas discharge lamp (L) comprises a current generator (1; 2) for generating a lamp current with a main lamp current component and, for arc-straightening purposes, a ripple current component. A controller (3) controls the current generator such as to set the ripple frequency (fR) and ripple amplitude (M). A memory (5) contains data defining a set point (SP) for the ripple frequency and ripple amplitude. A measuring device (4) provides at least one measuring signal indicative of arc curvature and arc stability. The controller is capable of operating in a ripple optimization mode in which the controller makes small adjustments to the ripple frequency and ripple amplitude to find improved arc-straightening, and, if such improvement is found, controls the current generator on the basis of the adjusted set point or otherwise resumes operation on the basis of the original set point (SP) in the memory (5).

Abstract: Method of driving a high-pressure gas discharge lamp during its steady-state operation, wherein a steady-state current signal is sent through the lamp for maintaining a discharge arc in the lamp, comprising the step of comparing the lamp conductivity response to a current step in said current signal with reference parameters; and in response to said comparison at least one of the following steps: stopping the current supply to the lamp, generating a signal indicating the end-of-life status of the lamp, changing the steady-state current through the lamp, changing the steady-state waveform of the current signal through the lamp, and generating a signal indicating the lamp type, wherein said current step is obtained by sending a current pulse which is superimposed on said steady-state current signal through the lamp.