A space efficient planar transformer can include a coupled inductor circuit that can include a metallic core, a first planar winding comprising a conductive coil having an electrical path encircling a first post of the metallic core, and a second planar winding configured to magnetically couple with the first winding via the metallic core. The second planar winding can have multiple portions. A portion of the second winding can include a first sub-portion comprising a single U-shaped planar conductive trace wrapped about the first post and a second sub-portion comprising a single U-shaped planar conductive trace wrapped about the first post. A layout of the first sub-portion can be oriented opposite a layout of the second sub-portion.