At this time, the attenuation factor of the waveform may vary according to the existence or non-existence of an external material within a specific distance based on the wireless power transmitter. Here, a specific distance set based on the wireless power transmitter may denote a distance capable of allowing the wireless power transmitter to transmit power in a wireless manner. Referring to the graphs of FIGS. 35, 36 and 37, it is seen that the attenuation factor varies within a period according to the existence or non-existence of an external material.
More specifically, the graph of FIG. 35 illustrates a waveform of a coil for power transmission provided in the wireless power transmitter when there exists no external material within a specific distance of the wireless power transmitter. Furthermore, the graph of FIG. 36 illustrates a waveform of a coil for power transmission provided in the wireless power transmitter when there exists an external material within a specific distance of the wireless power transmitter. When the graphs of FIGS. 35 and 36 are compared, it is seen that the attenuation factor varies when there exists an external material.
Moreover, the graph of FIG. 37 illustrates a waveform of a coil for power transmission provided in the wireless power transmitter when there exists a receiver capable or receiving wireless power within a specific distance of the wireless power transmitter. When FIGS. 35, 36 and 37 are compared, it is seen that the attenuation factor varies. Furthermore, due to the existence of the receiver in FIG. 37, it is seen that there is a waveform having an additional frequency.
