First, in case where power is transmitted according to the inductive coupling method, the wireless power transmitter 100 in the selection state 610 can monitor an interface surface (not shown) to detect the alignment and removal of objects.
Furthermore, the wireless power transmitter 100 may detect the location of the wireless power receiver 200 placed on an upper portion of the interface surface. As described above, the wireless power transmitter 100 formed to include one or more transmitting coils may perform the process of entering the ping state 620 in the selection state 610, and checking whether or not a response to the detection signal is transmitted from the object using each coil in the ping state 620 or subsequently entering the identification state 630 to check whether identification information is transmitted from the object. The wireless power transmitter 100 may determine a coil to be used for contactless power transfer based on the detected location of the wireless power receiver 200 acquired through the foregoing process.
Furthermore, when power is transmitted according to the resonance coupling method, the wireless power transmitter 100 in the selection state 610 can detect an object by detecting that any one of a frequency, a current and a voltage of the power conversion unit is changed due to an object located within the detection area.