WIRELESS POWER SYSTEM COMPRISING POWER TRANSMITTER AND POWER RECEIVER AND METHOD FOR RECEIVING AND TRANSMITTING POWER OF THE APPARATUSES

Provided is a method of a wireless power transmitter, including transmitting a detection power, detecting a variation of a load impedance, the variation being greater than a predetermined value, receiving a first signal including an identifier and a load characteristic of the wireless power receiver, the load characteristic including load information indicating the variation of the load impedance, transmitting a first response to form a communication connection with a wireless power receiver in response to the first signal, receiving a second signal including required power information of the wireless power receiver, determining whether power is available to the wireless power receiver based on the required power information, and transmitting a second response including permission information indicating a standby mode or a charging mode based on a result of the determining.