Patent ID: 8022803

Claim:
A transformer comprising: an inner bobbin including a primary winding unit and first secondary winding units positioned on at least one side of the primary winding unit; outer bobbins including second secondary winding units coupled to wrap outer circumferential surfaces of the first secondary winding units; a primary coil wound around the primary winding unit; first secondary coils wound around the first secondary winding units; second secondary coils wound around the second secondary winding units; and cores inserted through a body of the inner bobbin, wherein one of the first secondary winding units has a groove, and a corresponding one of the outer bobbins comprises a protrusion that is slidably received by the groove of the one of the first secondary winding units, wherein the corresponding one of the outer bobbins includes a plurality of sub-outer bobbins coupled with an outer circumferential surface of the one of the first secondary winding units, the sub-outer bobbins are spaced apart from each other at predetermined intervals, and wherein the sub-outer bobbins include coupling slots, and the one of the first secondary winding units includes coupling protrusions coupled with the coupling slots.