Planar Coil and Planar Transformer

A planar type coil used for a secondary-side coil of a transformer, comprising:

• a substrate on which wiring layers are superimposedly disposed;
• secondary-coils on the substrate, wherein a coil pattern corresponding to a part of one coil circumference of a respective secondary-side coil is respectively formed on each of the wiring layers;
• the one coil circumference of each of the secondary-side coils is formed across the wiring layers by connecting coil patterns provided on the wiring layers to each other via a conduction point in a superimposition direction of the wiring layers;
• the secondary-side coils are a center tap type coil pair;
• in the secondary-side coils that configure the coil pair, diodes for rectification and a leader line of a center tap are respectively provided at both end portions of the one coil circumference, the center tap is shared between coils in the coil pair, and
• the coil patterns are formed so that lengths to the diodes from the leader line of the center tap are equal lengths in all of the secondary-side coils.