FIG. 23 illustrates an attenuation curve of resonant energy when the operation of an LC resonant circuit of the wireless power transmitter in a state that only there exists the wireless power transmitter without the wireless power receiver 200 and external metal material;
FIG. 24 is an exemplary view illustrating a circuit for setting PT=0;
FIG. 25 is an exemplary view illustrating another circuit for setting PT=0;
FIG. 26 illustrates an attenuation curve of resonant energy when the operation of an LC resonant circuit of the wireless power transmitter suspends in a state that there exist only the wireless power receiver and the wireless power transmitter without an external metal material;
FIG. 27 is a view illustrating a waveform in which a current waveform of FIG. 23 and a current waveform of FIG. 26 overlap;
FIG. 28 is an exemplary view illustrating an attenuation curve (attenuation factor) of resonant energy;
FIG. 29 is another exemplary view illustrating an attenuation curve (attenuation factor) of resonant energy;
FIG. 30 is a flow chart illustrating a method of determining the existence or non-existence of the external metal material according to an embodiment of the present disclosure;
