METHOD FOR DETECTING FOREIGN MATERIAL, AND DEVICE AND SYSTEM THEREFOR

A wireless power transmitter that transmits power to a wireless power receiver, the wireless power transmitter including a communication unit configured to communicate with the wireless power receiver; and a controller, wherein the communication unit receives a plurality of packets including a foreign object detection (FOD) status packet from the wireless power receiver, wherein the controller determines whether a foreign object is present in a charging area of the wireless power transmitter on the basis of the FOD status packet, wherein the communication unit transmits, to the wireless power receiver, a response signal indicating whether the foreign object is present in the charging area of the wireless power transmitter on the basis of a result of the determination, wherein the response signal is determined using a measured peak frequency of a power signal transmitted by the wireless power transmitter and a reference peak frequency included in the FOD status packet received from the wireless power receiver, wherein each of the plurality of packets includes a preamble, a header, a message, and a checksum for identifying whether an error occurs in each packet, and wherein a size of the message included in the each packet is identified on the basis of a value of the header.