Voltage transformer (A) and rectifier (B1), (B2) meant for power supply for LED lamps wherein the mentioned transformer (A) comprises a three-phase primary winding and at least two three-phase secondary windings wherein the outputs (1u, 1 v, 1 w) and (2u, 2v, 2w) of the mentioned secondary windings are connected to the rectifiers (B1) and (B2). The secondary windings are divided for several primary windings with various phases and are connected with various connections between outputs of the secondary windings in order to create the desired phase differences or the secondary windings have each their own primary winding wherein the connections between the outputs of the secondary windings have a characteristic, desired phase difference.