Abstract: A planar transformer includes a primary winding surrounding a portion of a magnetic core. The primary winding is made up of a bundle of individually insulated conductors (wires) in a bundle, and the bundle is itself separately insulated as a whole. A secondary winding of insulated conductor makes at least one turn around the portion of the core. In one embodiment, the secondary winding is a planar concentric spiral structure with an out-of-plane bridging conductor. Electrical connection tabs may be located adjacent the “ends” of the secondary winding for connection of rectifiers. Series inductors may be connected to each of the tabs and to the direct-current output port of the transformer/rectifier combination, and the conductors of the series inductors may be monolithic with the secondary winding.