A transformer includes a transformer core, and a primary winding and a secondary winding each wound about the transformer core. The primary winding includes a wire wound in multiple primary winding layers, and each primary winding layer includes multiple primary turns arranged in a spiral. The secondary winding includes one or more substantially flat conductors defining multiple secondary winding layers. Each secondary winding layer includes one secondary turn, every two adjacent secondary turns have a single different one of the primary winding layers positioned between the two adjacent secondary turns to interleave the secondary winding and the primary winding, and each secondary turn has a different diameter than an adjacent one of the secondary turns.