Patent ID: 7932799

Claim:
A transformer comprising: at least one first printed circuit board with a planar primary winding on a substrate; at least one second printed circuit board with a planar secondary winding on a substrate; and a core with at least one core leg around which said printed circuit boards are arranged, wherein said at least one second printed circuit board includes a plurality of layers and a multi-layer secondary winding, wherein each layer of the plurality of layers contains one or more winding turns of the multi-layer secondary winding, wherein the multi-layer secondary winding of the plurality of layers comprises (i) a first portion of the multi-layer secondary winding for being coupled with a higher voltage potential during operation, (ii) a second portion of the multi-layer secondary winding for being coupled with a smaller voltage potential during operation, (iii) wherein the number of winding turns increases from a smallest number of turns in the first portion of the multilayer secondary winding to a highest number of turns in the second portion of the multilayer secondary winding, further wherein turns of each layer of the multilayer secondary winding are arranged symmetrically around a vertical line through a middle of a core window of the core, and (iv) wherein said first portion of the multi-layer secondary winding is arranged within a corresponding layer of the plurality of layers of the at least one second printed circuit board, and said second portion of the multi-layer secondary winding is arranged within a respective corresponding layer of the plurality of layers of said at least one second printed circuit board such that a closest distance between a respective winding of the second portion and the core leg is smaller than a closest distance between a respective winding of the first portion and the core leg, wherein said at least one first printed circuit board and said at least one second printed circuit board are separated from each other by a non-ferromagnetic and electrically insulating material, which material transfers heat better than said substrates.