METHOD FOR DETECTING FOREIGN MATERIAL, AND APPARATUS AND SYSTEM THEREFOR

A power transmission method for a wireless power transmitter, the power transmission method including receiving, from a wireless power receiver, a foreign object detection (FOD) status packet including information on a reference quality factor or a reference peak frequency, 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; determining whether a foreign object is present in a charging area of the wireless power transmitter based on the FOD status packet; and generating a foreign object detection indicator indicating whether the foreign object is present in the charging area of the wireless power transmitter based on a result of the determination and transmitting the generated foreign object detection indicator to the wireless power receiver, 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.