Abstract: A coil component includes a primary winding generating a magnetic field by current input from outside, and a secondary winding an induced current generated by the magnetic field passes. The primary winding includes ring-shaped primary first/second turns as viewed in first direction. The secondary winding includes ring-shaped secondary first/second turns as viewed in first direction. The primary and secondary first turns are alternately arranged in first direction to form a first tubular portion. The primary and secondary second turns are alternately arranged in first direction to form a second tubular portion. The second tubular portion is located inside the first tubular portion as viewed in first direction. The input current in each primary first turn and the input current in each primary second turn flow in the same direction.

Abstract: A driving circuit controls driving of a switching element by outputting a driving signal to the switching element. The driving circuit includes an air-core transformer having a plurality of primary windings and a secondary winding magnetically coupled to each of the plurality of primary windings. An AC signal is input to each of the plurality of primary windings of the air-core transformer. The plurality of primary windings includes a first primary winding and a second primary winding. There is a phase difference between an AC signal input to the first primary winding and an AC signal input the second primary winding.

Abstract: An example inductor comprises multiple coil parts and each formed by flatwise-winding layers of turns of a flat wire arranged in a radial direction with gaps between each of the layers, and the multiple coil parts are arranged in an axial direction with a clearance. There is provided a clearance between the multiple coil parts, through which air flows, achieving improvement in heat dissipation.