A transformer includes a magnetic structure and a set of coils. The magnetic structure includes a top member, a bottom member, and a plurality of legs extending between the top member and the bottom member. The plurality of legs include two outer legs. The set of coils is wound about the two outer legs of the magnetic structure and electrically coupled in series. In other examples, the magnetic structure includes a middle member positioned between the top member and the bottom and extending between the two outer legs. In such examples, a second set of coils is wound about the two outer legs of the magnetic structure and electrically coupled in series. Other example transformers and power converters such as multiphase interleaved power converters having transformers are also disclosed.