Method for reducing electromagnetic interference radiated from a power supply arrangement comprising two switching mode power supply units (1, 2) connected to an external device, wherein each switching mode power supply unit (1, 2) comprises a ground point (A, B), the method comprising synchronizing a switching frequency of each switching mode power supply unit (1, 2), such that all of said synchronized switching mode power supply units (1, 2) have an identical switching frequency, characterized by connecting each switching mode power supply unit (1, 2) to said external device by means of conductors (4, 7), and a ground conductor (6, 9) associated with said conductors (4, 7), such that a first ground conductor is connected to a first ground point of a first switching mode power supply unit, and a second ground conductor is connected to a second ground point of a second switching mode power supply unit; mutually connecting said first and second ground conductors (6, 9) by means of a first common ground connection associated with the external device, as well as by means of a second common ground connection associated with the switching mode power supply units (1, 2), thereby providing a ground-loop, comprising first ground conductor, first common ground connection, second ground conductor and second common ground connection; and whereby said synchronizing is performed such that a common-mode current (I cm) generated by each switching mode power supply unit (1, 2) is controlled to return mainly in the ground conductor (6, 9) associated with said switching mode power supply unit (1, 2) that generated said common-mode current (I cm), thereby reducing the difference in electric potential between said ground points (A, B). synchronizing a switching frequency of each switching mode power supply unit (1, 2), such that all of said synchronized switching mode power supply units (1, 2) have an identical switching frequency, characterized by connecting each switching mode power supply unit (1, 2) to said external device by means of conductors (4, 7), and a ground conductor (6, 9) associated with said conductors (4, 7), such that a first ground conductor is connected to a first ground point of a first switching mode power supply unit, and a second ground conductor is connected to a second ground point of a second switching mode power supply unit; mutually connecting said first and second ground conductors (6, 9) by means of a first common ground connection associated with the external device, as well as by means of a second common ground connection associated with the switching mode power supply units (1, 2), thereby providing a ground-loop, comprising first ground conductor, first common ground connection, second ground conductor and second common ground connection; and whereby said synchronizing is performed such that a common-mode current (I cm) generated by each switching mode power supply unit (1, 2) is controlled to return mainly in the ground conductor (6, 9) associated with said switching mode power supply unit (1, 2) that generated said common-mode current (I cm), thereby reducing the difference in electric potential between said ground points (A, B).