The invention relates to a switched mode power supply with a transformer (1), which comprises at least one primary winding, which can be connected to a DC voltage via a switching element (4) and which comprises at least one secondary winding, which can be connected to a load via a rectifier circuit comprising at least one diode (2), wherein the switched mode power supply comprises at least one piezoelectric fan (8), which brings about an air flow at the transformer (1) and/or at the switching element (4) and/or at the diode (2). The air flow produced can be guided in a targeted manner onto the components to be cooled, with the air throughflow in total remaining low and therefore also no contamination by means of air particles arising.