A device for reducing high-frequency interferences between first and second windings of a transformer that includes a first winding (W1) and a second winding (W2), which are wound around a common core, wherein the first winding (W1) is an interference-emitting winding and a shielding winding (WS) or a shielding film (WS) is arranged between the first winding (W1) and the second winding (W2), wherein the shielding winding (WS) and the core are connected to the reference potential (B) of the first winding (W1).