US Patent 7443278 Coil device, composite coil device, and transformer device

A transformer-type compact and thin coil device having a high coupling degree between a primary coil and a secondary coil, and a transformer device in which a plurality of sets of the transformer-type coil devices are incorporated. A coil device includes a first winding portion in which a primary and secondary coil wires are wound in bifilar form so as to arrange them alternately in a plane, a second winding portion in which a secondary coil wire is wound to arrange it in a plane parallel to the plane of the first winding portion, and a secondary coil connecting portion which connects an inner diameter portions of the secondary coil wires of the first and second winding portions. A transformer device is formed by incorporating a plurality of sets of the transformer-type coil devices each formed in above manner.