Wireless power transmitter, wireless power receiver, and control methods thereof

A wireless power transmitter for transmitting charging power to a wireless power receiver, the wireless power transmitter comprising:

• a communication unit configured to transmit a control signal including first time information and load change information to the wireless power receiver;
• a controller configured to detect a load change of the wireless power receiver during a period of time corresponding to the first time information, and to determine that the wireless power receiver is authorized for charging, if the detected load change of the wireless power receiver corresponds to the load change information included in the control signal;
• and
• a power transmitting unit configured to apply the charging power to the wireless power receiver authorized for charging.

A method for controlling a wireless power receiver to receive charging power from a wireless power transmitter, the method comprising:

• receiving, from the wireless power transmitter, a control signal including first time information and load change information;
• changing a load state according to the load change information, during a period of time corresponding to the first time information;
• and
• returning the load state back to a previous state before the changing, after a lapse of the period of time corresponding to the first time information.

A wireless power receiver for receiving charging power from a wireless power receiver, the wireless power receiver comprising:

• a communication unit configured to receive a control signal including first time information and load change information from the wireless power transmitter;
• a charging unit configured to charge the wireless power receiver at the charging power received from the wireless power transmitter;
• a load switch configured to switch a connection state of the charging unit to be in an on or off state;
• and
• a controller configured to controlling the load switch to be changed into the on state during a period of time corresponding to the first time information, based on the load change information.