Method of generating load variation for detecting wireless power receiving unit in wireless charging, and wireless power receiving unit

A wireless power receiver, comprising:

• a power receiver configured to receive power from a wireless power transmitter;
• a communication module configured to receive, from the wireless power transmitter, a time set value that is set for checking cross connection;
• and
• a controller configured to:
• generate a power variation in the wireless power receiver by converting a load status from a first load status to a second load status, and
• maintain the second load status for time corresponding to the received time set value.

A method for controlling a wireless power transmitter, the method comprising:

• transmitting a time set value that is set for checking cross connection to the wireless power receiver;
• detecting a load variation of the wireless power receiver;
• comparing the time set value with a load variation period;
• determining whether the wireless power receiver is cross-connected, based on the comparison result;
• and
• in response to determining that the wireless power receiver is cross-connected, transmitting a power receiving unit (PRU) control signal with a permission field indicating that the wireless power receiver is not permitted due to the cross connection.

A wireless power transmitter, comprising:

• a communication module configured to transmit a time set value that is set for checking cross connection to a wireless power receiver;
• and
• a controller configured to:
• detect a load variation of the wireless power receiver,
• compare the time set value with a load variation period,
• determine whether the wireless power receiver is cross-connected, based on the comparison result, and
• in response to determining that the wireless power receiver is cross-connected, transmit, through the communication module, a power receiving unit (PRU) control signal with a permission field indicating that the wireless power receiver is not permitted due to the cross connection.