There have been an increasing number of machines activated by cordless power supply utilizing electromagnetic inductance, such as electric toothbrushes, cordless telephones, and portable devices (e.g., PTL 1). There have also been developments of machines activated by cordless power supply utilizing magnetic resonance, in relation to wall-hang television sets and personal computers (e.g., PTL 2). To add this, there have been many developments and suggestions for magnetic elements for wireless power transmission capable of feeding high power with high power transmission efficiency, in the field of wireless power transmission.
However, feeding high power with high power transmission efficiency in such a magnetic element for wireless power transmission causes an excessive heat generation. This generated heat in the magnetic element for wireless power transmission may cause a problem to the magnetic element itself or to the functional parts of the element.
To address this problem of heat generation, for example, one approach is to adopt a structure of substrate having an in-built coil such as the one disclosed in PTL 3, in which a planar coil conductor to serve as the heat source is covered with a magnetic layer so as to radiate the heat outside through a conductor layer for heat transfer which is provided to the magnetic layer. This, without a doubt, enables radiation of heat generated by the planar coil to the outside.