Apparatus and method for detecting foreign object in wireless power transmission system
Disclosed in the present specification is a wireless power reception device comprising: a power pickup unit for receiving wireless power from a wireless power transmission device by means of magnetic coupling with the wireless power transmission device and transforming, into a direct current signal, an alternating current signal generated by wireless power; a communication/control unit for receiving the direct current signal from the power pickup unit, transmitting, to the wireless power transmission device, a first power transmission suspension packet for temporarily suspending transmission of the wireless power in order to detect a foreign object, and performing a foreign object detection procedure within a predetermined time window when the transmission of the wireless power is temporarily suspended; and a load for receiving the direct current signal from the power pickup unit.
1. A wireless power receiver for receiving wireless power from a wireless power transmitter based on a foreign object detection (FOD) in a wireless power transmission system, the wireless power receiver comprising:
a power pick-up configured to:
receive the wireless power from the wireless power transmitter through magnetic coupling with the wireless power transmitter, and
convert an alternating current (AC) signal generated by the wireless power to a direct current (DC) signal;
a communicator/controller configured to:
receive the DC signal from the power pick-up, and
control the wireless power; and
a load configured to receive the DC signal from the power pick up,
wherein the communicator/controller is further configured to:
transmit, to the wireless power transmitter, a first End Power Transfer (EPT) packet that temporarily ends transmission of the wireless power,
wherein the first EPT packet is related to initiating a procedure of the FOD;
measuring parameter information, which includes both a resonant frequency and a quality factor, of the wireless power receiver based on transmitting the first EPT;
comparing a measurement value of the parameter information with a reference parameter value; and
determining the FOD based on a result of the comparing,
wherein the procedure of the FOD includes the measuring, the comparing and the determining, and is performed within a predetermined time window, and
wherein the reference parameter value is defined as a minimum value of the measurement value of the parameter information based on the wireless power receiver being located at a center point of a reference wireless power transmitter and measurement values of the parameter information based on the wireless power receiver being located at positions separated by a predetermined distance from the center point of the reference wireless power transmitter in east, west, south, and north directions.
2. The wireless power receiver of claim 1 , wherein the predetermined time window is determined based on a reping time.
3. The wireless power receiver of claim 2 , wherein the communicator/controller transmits a packet including the reping time to the wireless power transmitter.
4. The wireless power receiver of claim 1 , wherein, based on the procedure of the FOD being completed, the communicator/controller transmits, to the wireless power transmitter, a packet that reports the result of the comparing after the predetermined time window expires.