Method and apparatus for generating slot in wireless power transmission system

A wireless power transmitter, comprising:

• a converter related to transferring wireless power to a wireless power receiver;
• and
• a communicator/controller related to controlling the transfer of the wireless power,
• wherein the wireless power transmitter:
• enters a power transfer phase related to transferring the wireless power to the wireless power receiver;
• generates a slot in the power transfer phase;
• and
• performs a foreign object detection on the slot,
• wherein the wireless power transmitter increases an operating frequency from a first operating frequency to a second operating frequency before generating the slot, and
• wherein the wireless power transmitter decreases the operating frequency from the second operating frequency to the first operating frequency after end of the slot.

A method for receiving a wireless power in a wireless power transfer system, the method performed by a wireless power receiver and comprising:

• entering a power transfer phase related to receiving the wireless power from a wireless power transmitter,
• wherein a slot is generated in the power transfer phase,
• wherein the wireless power receiver receives the wireless power based on a first operating frequency before generating the slot, and then receives the wireless power based on a second operating frequency,
• wherein the wireless power receiver receives the wireless power based on the second operating frequency after end of the slot and then receives the wireless power based on the first operating frequency, and
• wherein the first operating frequency is a lower operating frequency than the second operating frequency.