Method and apparatus for measuring quality factor in wireless power transmission system

A wireless power transmitter comprising:

• a power converter related to transferring wireless power to a wireless power receiver;
• and
• a communicator/controller related to communicating with the wireless power receiver and controlling transfer of the wireless power,
• wherein the communicator/controller is configured to:
• receive, from the wireless power receiver, information for detecting whether a foreign object (FO) exists;
• detect whether the FO exists before transferring the wireless power based on the information;
• transfer, to the wireless power receiver, the wireless power based on detecting that the FO is not exist;
• and
• perform calculation of a slot quality factor on a slot while transferring the wireless power,
• wherein the slot quality factor is a quality factor used to determine whether an FO is inserted while transferring the wireless power, and
• wherein a starting point of the slot is a point at which a voltage value of a coil in the wireless power transmitter is a maximum and a current value of the coil is 0.

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

• transmitting, to a wireless power transmitter, information for detecting whether a foreign object (FO) exists;
• and
• receiving, from the wireless power transmitter, the wireless power based on detecting that the FO is not exist;
• and
• wherein calculation of a slot quality factor is performed on a slot while the wireless power is received,
• wherein the slot quality factor is a quality factor used to determine whether an FO is inserted while transferring the wireless power, and
• wherein a starting point of the slot is a point at which a voltage value of a coil in the wireless power transmitter is a maximum and a current value of the coil is 0.