An illumination system (1) comprises a plurality of light sources (11, 12, 13), each provided with a driver (21, 22, 23); a controller (30) for generating control signals (Sc1, Sc2>Sc3) for controlling the respective drivers; temperature feed forward means (60, 61, 62, 63, 81) for establishing a temperature feed forward (TFF) correction mechanism; flux feedback means (71, 82, 83, 84) for establishing a flux feedback (FFB) correction mechanism. The controller is capable of operating in a first mode of operation wherein both the temperature feed forward correction mechanism and the flux feedback correction mechanism are active, and is capable of operating in a second mode of operation wherein the temperature feed forward correction mechanism is active and the flux feedback correction mechanism is inactive. The controller is designed to monitor the duty cycles of the control signals and to select its mode of operation based on said duty cycles.