Abstract: An embedded transformer device includes first, second, and auxiliary windings, defined in an insulating substrate by conductive vias joined together by conductive traces. The positions of the conductive vias are arranged to optimize the isolation properties of the transformer and to reduce the coupling of the transformer by increasing the leakage inductance. The embedded transformer device provides better isolation between input side and output side windings, and allows an oscillating LC circuit to be set up in the case of a short circuit, preventing high power from extending between the input and output terminals and thereby avoiding damage to the connected electrical components.