To prevent reduction in inductance due to saturation of a core by providing a through hole at the core of a drum core, inserting a material of higher saturation magnetic flux density than a magnetic body into the through hole, and winding around a core part of drum core.
On a base 15 of resin, a drum core 11 molded from ferrite and wound with a coil 12 is mounted, and a ring core 13 is allocated around the drum core 11. Then, a magnetic path is formed with the drum core 11 and ring core 13. In the drum core 11, a through hole 11A is formed at the core, and a magnetic body 14 is inserted in the through hole 11A. As a material of the magnetic body 14, such a material as iron, permalloy, etc., whose saturation magnetic flux density is larger than the ferrite forming the drum core 11 are used.
MURAKAMI HIROMI
SASAMORI KUNIO
