Wireless power transmitter and method for controlling resonance frequency using the same

1. A wireless power transmitter, comprising:

resonators electrically connected to each other; and

a resonance frequency varying unit configured to vary resonance frequencies of the resonators based on a change in an amount of power to be sent to a wireless power receiver from the wireless power transmitter,

wherein upon the amount of power to be sent to the wireless power receiver being an amount greater than or equal to a first threshold value, the resonance frequency varying unit is configured to increase the resonance frequencies of the resonators, and upon the amount of power to be sent to the wireless power receiver being an amount less than or equal to a second threshold value which is smaller than the first threshold value, the resonance frequency varying unit is configured to decrease the resonance frequencies of the resonators.

2. The wireless power transmitter of claim 1 , wherein the resonance frequency varying unit varies the resonance frequencies of the resonators by varying capacitance levels of the resonators.

3. The wireless power transmitter of claim 1 , further comprising an inverter unit configured to operate the resonators by performing a switching operation,

wherein the resonance frequency varying unit is configured to vary the resonance frequencies of the resonators based on a change in a received voltage from the inverter unit.

4. The wireless power transmitter of claim 1 , further comprising:

a power supply unit configured to transform a received voltage and output the transformed input voltage; and

an inverter unit configured to receive an output of the power supply unit and operate the resonators by performing a switching operation.

5. The wireless power transmitter of claim 4 , wherein the resonance frequency varying unit is configured to vary the resonance frequencies of the resonators based on a change in a received current from the power supply unit.

6. The wireless power transmitter of claim 4 , further comprising a control unit configured to identify the amount of power to be sent to the wireless power receiver and control the output of the power supply unit based on the identified amount of power to be sent to the wireless power receiver.

7. The wireless power transmitter of claim 3 , wherein the resonance frequency varying unit comprises:

a variable capacitor having a first terminal electrically connected to the resonators; and

a capacitance controller configured to adjust a capacitance of the variable capacitor depending on a comparison result between a received voltage from the inverter unit and a set threshold voltage.

8. The wireless power transmitter of claim 7 , wherein the variable capacitor has a second terminal electrically connected to an output terminal of the inverter unit.

9. The wireless power transmitter of claim 7 , wherein the resonators are electrically connected in parallel.

10. A method for controlling a resonance frequency, the method comprising:

identifying an amount of power to be sent from a wireless power transmitter to a wireless power receiver; and

varying a resonance frequency of the wireless power transmitter in response to a change in the amount of power to be sent to the wireless power receiver,

wherein the varying of the resonance frequencies of the resonators comprises increasing the resonance frequencies when amount of power to be sent to the wireless power receiver is greater than or equal to a first threshold amount and decreasing the resonance frequencies when the amount of power to be sent to the wireless power receiver is less than or equal to a second threshold amount which is smaller than the first threshold amount.

11. The method of claim 10 , wherein the wireless power transmitter comprises:

resonators, and a one variable capacitor configured to vary capacitance levels of the resonators, and

the varying of the resonance frequency of the wireless power transmitter comprises varying resonance frequencies of the resonators by varying the capacitance levels of the resonators.

12. The method of claim 10 , wherein the varying of the resonance frequencies of the resonators comprises:

increasing an input voltage of an inverter when the amount of power to be sent to the wireless power receiver is increased; and

increasing the resonance frequencies of the resonators upon the input voltage of the inverter being greater than or equal to a threshold voltage.

13. The method of claim 10 , wherein the varying of the resonance frequencies of the resonators comprises:

decreasing an input voltage of an inverter when the amount of power to be sent to the wireless power receiver is decreased; and

increasing the resonance frequencies of the resonators upon the input voltage of the inverter being greater than or equal to a threshold voltage.

14. The method of claim 10 , wherein the resonators are electrically connected in parallel.