Abstract: A transformer includes a core and a metal shield. The core includes a bottom plate, a middle leg protruding from the bottom plate, and a first outer leg and a second outer leg located opposite to each other along a first axis and protruding from the bottom plate on both sides of the middle leg. A width of a first opening, formed between the first outer end surface and the third outer end surface, along the first axis is smaller than a width of a second opening, formed between the second outer end surface and the fourth outer end surface, along the first axis.

Abstract: A coil device includes a first coil a first coil formed by a first wire wound in a coil shape and a second coil formed by a second wire wound in a coil shape. The first coil includes a first portion provided inside the second coil and a second portion next to the first portion and the second coil along a winding axis of the first portion. A layer number of the first portion in its radial direction is one. A layer number of the second portion in its radial direction is plural.

Abstract: A coil device includes a bobbin, a main core, and wires. A connection portion located between a first bobbin flange portion and a second bobbin flange portion includes a raised portion protruding along a direction perpendicular to a first axis more than the connection portion located between a first terminal block and a first bobbin flange portion. Communication wire portions connecting first wires of a proximal first coil and first wires of a distal first coil are arranged in a wiring space formed between second wires wound in contact with an upper end of the raised portion and an outer surface of the winding core portion or the bobbin.