Patent ID: 7345565

Claim:
A transformer comprising: two bobbin assemblies, said bobbin assemblies each comprising an electrically insulative bobbin, a primary winding and a secondary winding, said electrically insulative bobbin having an axially extending center through hole, a primary side and a secondary side extending around said axially extending center through hole around the periphery for supporting said primary winding and said secondary winding, and a partition space extending around the periphery between said primary side and said secondary side; and an ferrite core set installed in said bobbin assemblies, said ferrite core set comprising two first ferrite cores respectively fitted into said axially extending center through holes of said electrically insulative bobbins, and at least one second ferrite core disposed outside said electrically insulative bobbin and abutted against said first ferrite cores; wherein said electrically insulative bobbin of each of said two bobbin assemblies each comprises a plurality of partition flanges extending around the periphery in said secondary side of said respective electrically insulative bobbin, a side through hole cut through the periphery in communication between said partition space and said center through hole of said respective electrically insulative bobbin, a plurality of winding spaces extending around the periphery of said respective electrically insulative bobbin and separated by said partition flanges, a plurality of vacant spaces defined between each two adjacent partition flanges around said periphery of the respective electrically insulative bobbin and separated by said winding spaces, a plurality of top bridging notches and bottom bridging notches respectively formed on said partition flanges such that said vacant spaces each have one side in communication with one of said top bridging notches and an opposite side in communication with one of said bottom bridging notches; said at least one second ferrite core of said ferrite core set comprises two protruding portions respectively inserted through said side through holes of said electrically insulative bobbins of said bobbin assemblies to form with said first ferrite cores two separated magnetic loops.