METHOD FOR DETECTING FOREIGN MATERIAL, AND DEVICE AND SYSTEM THEREFOR

A method of transmitting power by a wireless power transmitter, the method including receiving a plurality of packets including a foreign object detection (FOD) status packet from a wireless power receiver; determining whether a foreign object is present in a charging area of the wireless power transmitter on the basis of the FOD status packet; and transmitting, 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 the plurality of packets further include at least one of a signal strength packet, an end power transfer packet, a power control hold-off packet, a control error packet, a renegotiation packet, an eight-bit received power packet, and a charging status packet, to which a byte encoding technique is applied, and wherein the byte encoding technique is a technique of inserting a start bit, a stop bit, and a parity bit into an encoded binary bit stream of a packet having a length of eight bits.