Wireless power transmitter, wireless power receiver, and control methods thereof

A wireless power transmitter, comprising:

• a resonator;
• a wireless communication circuit;
• and
• a controller configured to:
• control the wireless power transmitter to output a first power for detecting a change in a load impedance of the wireless power transmitter through the resonator,
• detect the change in the load impedance of the wireless power transmitter,
• in response to detecting the change in the load impedance, control the wireless power transmitter to output a second power for communicating with an external device through the resonator,
• receive, from a wireless power receiver, through the wireless communication circuit, a first signal within a preset time period after detecting the change in the load impedance,
• determine whether a reception intensity of the first signal is less than or equal to a threshold, and
• based on determining that the reception intensity of the first signal is less than or equal to the threshold, terminate a communication in connection with the first signal from the wireless power receiver, the wireless power receiver being outside of a charging range of the wireless power transmitter.