Method for transmitting a signal of wireless power transmitting unit in wireless charge system, the wireless power transmitting unit, the wireless power receiving unit

The method comprising a signal transmission method of a wireless power transmitter in a wireless charging system in accordance with various embodiments of the present invention, transmitting the first signal; The step of transmitting a second signal; Sensing a load change of the first period in which the second signal is transmitted; It may comprise; and step on the basis of the load change of the sense of extending the transmission period of the second signal.