METHOD FOR DETECTING FOREIGN MATERIAL, AND APPARATUS AND SYSTEM THEREFOR

A wireless power transmitter that transmits power to a wireless power receiver, the wireless power transmitter including a wireless communication unit configured to communicate with the wireless power receiver; and a controller, wherein the wireless communication unit receives a foreign object detection (FOD) status packet, and 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 reception power packet, and a charging status packet to which a byte encoding technique is applied 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 wireless communication unit transmits, to the wireless power receiver, a foreign object detection indicator 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 FOD status packet includes information on a reference quality factor or a reference peak frequency, 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 8 bits.