Patent ID: 7978041

Claim:
A printed circuit board transformer comprising at least one primary winding ( 3 , 5 ) and one secondary winding ( 11 ), each in the form of at least one layer of turns inside or at the surface of a printed circuit board ( 9 ), said transformer having a turn ratio of said primary winding to said secondary winding differing from 1:1 to achieve a step-up/down-operation, wherein each of said two layers has an elongated winding element ( 12 , 13 , 13 ′, 13 ″, 13 ′″) substantially following an elongated winding element of the other layer while being in an overlapping relationship therewith as seen perpendicularly to said printed circuit board ( 9 ) over substantially the entire extension of said winding elements, a second ( 11 ) of said layers belonging to said secondary winding has a fewer number of turns than the number of turns of a first ( 10 ) of said layers belonging to said primary winding, and said second winding layer ( 11 ) comprises a segment ( 16 , 16 ′) of a plurality of said elongated winding elements ( 13 , 13 ′, 13 ″, 13 ′″) connected in parallel with each other within said layer ( 11 ) and configured to extend within said layer ( 11 ) such that each said elongated winding element is in said overlapping relationship with an elongated winding element ( 12 ) in said first winding layer ( 10 ).