A light generating device (1) is provided with at least a voltage input (21) adapted for receiving a variable voltage, at least three LED circuits (10), coupled with said voltage input (21), wherein each LED circuit (10) comprises a LED unit (14) and controllable current regulator (15) to control the current through said LED circuit (10). The light generating device (1) further comprises a controllable switch matrix (30) comprising a plurality of switches (25, 26, 27), said switch matrix (30) is configured to operate in at least three different switching modes and a controller (50), connected at least with said switch matrix (30), configured to determine said variable operating voltage and to control the switching mode of said switch matrix (30) in dependence of the determined operating voltage. To provide an efficient operation of such device (1) with a variable operating voltage, such as an AC voltage, in a first switching mode, said LED units (10) are connected parallel to each other, in a second switching mode, at least two of said LED units (10) are connected in series and in a third switching mode, said LED units 10 are connected in series with each other.