Patent ID: 7872561

Claim:
A composite transformer comprising: a core having a middle leg and at least one pair of outer legs on opposite sides with respect to the middle leg, the core forming a closed magnetic path; two outer leg portions being defined by at least one of the outer legs being divided with a space therebetween allowing coil wiring therebetween; a first pair of coils including at least two coils wound around the middle leg of the core; and a second pair of coils including at least two coils respectively wound around said two outer leg portions such that a winding direction of a portion of each of the at least two coils that is wound around one of the two leg portions is opposite to a winding direction of a portion of each of the at least two coils that is wound around another of the two leg portions; wherein the first pair of coils and the second pair of coils are arranged such that magnetic interference does not substantially occur between the first pair of coils and the second pair of coils.