DRIVER FOR OPERATING A GAS DISCHARGE LAMP

摘要

A driver (1) for driving a gas discharge lamp (2) comprises: a controllable current source (3); a controller (4) for controlling the current source (3); measuring means (5) for measuring the distance between the lamp electrodes (21, 22). The controller controls the current source (3) such as to generate a commutating lamp current with a predefined current frequency (f) and a duty cycle (?). The controller is capable of operating in a modulated duty cycle mode in which the duty cycle has a first value (?1) during a first phase (P1) alternated with a second value (?2) equal to one minus the first value (?2 = 1 - ?1) during a second phase (P2), wherein the second phase (P2) and first phase (P1) have mutually equal duration, and wherein switching between the second phase and first phase and vice versa occurs at a predefined duty cycle switching frequency (f<SUB>?</SUB>).