In various embodiments a method is provided for determining a demagnetization zero current time for a switched mode power supply having a transformer, a first side and a second side being galvanically separated from each other and a switched mode power supply controller, the method including: determining a first voltage being applied to one side of the transformer; determining a second voltage provided at the other side of the transformer; determining a time the first voltage is provided to a winding of the transformer; and determining, by a circuit located on the same side of the transformer as the switched mode power supply controller, the demagnetization zero current time using the determined first voltage, the determined second voltage and the determined time.