Wireless power transmitting device for detecting foreign object and method for operating the same

A wireless power transmitting device comprising:

• a transmission coil;
• a power providing circuit;
• at least one controller;
• and
• memory storing instructions,
• wherein the instructions, when executed by the at least one controller individually or collectively cause the wireless power transmitting device to:
• control the power providing circuit to apply first power to the transmission coil,
• identify a resonant frequency, based on a voltage measured at the transmission coil in response to the first power applied to the transmission coil,
• identify a reference frequency in the wireless power transmitting device,
• based on a difference between the identified resonant frequency and the reference frequency meeting a designated condition, identify that a foreign object is placed on a charging area of the wireless power transmitting device, and
• based on the difference between the identified resonant frequency and the reference frequency failing to meet the designated condition:
• control the power providing circuit to apply, to the transmission coil, at least one second power for performing communication with a wireless power receiving device,
• receive at least one response from the wireless power receiving device while applying the at least one second power,
• obtain another reference frequency included in the at least one response,
• based on a difference between the identified resonant frequency and the other reference frequency, determine whether the wireless power receiving device is placed on the charging area, or both the wireless power receiving device and the foreign object are placed on the charging area, and
• in case of receiving no response from the wireless power receiving device, control the power providing circuit to stop applying the at least one second power.