Method for controlling power transmitting device, method for detecting foreign object, and power transmitting device in wireless power transmission system

A power transmitting device comprising:

• a power transmitting coil for providing output power to a power receiving coil;
• a thermal sensor that detects a temperature around the power transmitting coil;
• and
• a power transmission control circuit that controls the power transmitting device,
• wherein the power transmission control circuit performs operations including
• causing the power transmitting coil to provide first output power,
• causing the power transmitting coil to provide second output power to the power receiving coil for charging a battery connected to the power receiving coil,
• causing the thermal sensor to detect the temperature around the power transmitting coil, and
• causing, if the detected temperature is equal to or higher than a threshold because of existing a metal foreign object, the power transmitting coil to reduce a level of the output power or stop the output power, and
• wherein the level of the first output power is lower than the level of the second output power.