WIRELESS POWER TRANSMITTING DEVICE AND METHOD OF DETECTING FOREIGN SUBSTANCES BY WIRELESS POWER TRANSMITTING DEVICE

A wireless power transmitting device according to an embodiment of the present specification transmits wireless power to a wireless power receiving device, and includes a power conversion circuit including a primary coil for transmitting the wireless power to the wireless power receiving device and a communication/control circuit for communicating with the wireless power receiving device and controlling the power conversion circuit, wherein, to detect foreign substances between the wireless power receiving device and the wireless power transmitting device, the communication/control circuit stops the transmission of the wireless power for a slot time, detects the foreign substances on the basis of a change in the voltage or current of the primary coil within the slot time, and sets the slot time to start from a point in time when the current of the primary coil is 0.