In recent years, wireless power transfer techniques have been gaining attention in order to provide power supply or perform charging. Research and development are being conducted regarding a wireless power transfer system wirelessly performing power transfer to various electronic apparatuses such as mobile terminals and notebook computers and household electrical appliances or to power infrastructure equipment.
In order to use wireless power transfer, it is preferable to standardize so that no problem occurs in the use of a power source of a power source and a power receiver of a power receiver that are of different manufactures.
Among conventional wireless power transfer techniques, a technique using electromagnetic induction and a technique using radio waves have generally been known. On the other hand, expectations for power transfer techniques using magnetic field resonance (magnetic resonance) or electric field resonance have been increasing recently, as techniques allowing for power transfer to a plurality of power receivers and power transfer to various three-dimensional postures while maintaining some distance between power sources and the power receivers. Electric field resonance may also be called electric resonance.
As described above, attention has conventionally been paid to wireless power transfer techniques for wirelessly transferring power for the purposes of power supply or charging. Nevertheless, standardization of power transfer techniques, for example, using magnetic field resonance or electric field resonance has not been made so far.
There has thus been a concern over stagnation of practical application of a power transfer system using magnetic field resonance or electric filed resonance or of a power source and a power receiver.
A variety of wireless power transfer techniques have conventionally been proposed.    Patent document 1: Japanese Laid-open Patent Publication No. 2010-239769    Patent document 2: U.S. Pat. No. 7,825,543    Non-Patent document 1: SHOKI Hiroki, et al., “Standardization Trends on Wireless Power transfer”, Technical Report of The Institute of Electronics Information, and Communication Engineers (IEICE technical report), WPT 2011-19, December 2011.