A method of controlling a wireless power transmitter can include receiving, during a first determination phase, a foreign object detection status packet; before entering a first power transfer mode for transmitting first power and before entering a second power transfer mode for transmitting second power, determining whether a foreign object is present based on the foreign object detection status packet to generate a determination result; in response to determining that the foreign object is present based on the determination result, transmitting the first power according to the first power transfer mode; in response to determining that the foreign object is not present based on the determination result, transmitting the second power according to the second power transfer mode; and determining, during a second determination phase, whether the foreign object is present while transmitting the first power in the first power transfer mode.