Wireless charging device, a receiver device, and a method of operating the same

1. A wireless charging device comprising:

a driver unit configured to generate one of a first alternating current (AC) voltage signal having a first frequency and a second alternating current (AC) voltage signal having a second frequency;

a transmitting unit coupled to the driver unit, wherein the transmitting unit comprises:

a first coil and a first capacitor coupled to each other and configured to transmit the first AC voltage signal having the first frequency; and

a second coil and a second capacitor coupled to each other and configured to transmit the second AC voltage signal having the second frequency; and

a control unit coupled to the transmitting unit and the driver unit, the control unit configured to:

detect a first receiver device operating at the first frequency based on a change in a first voltage measured at a first junction between the first coil and the first capacitor, wherein the change in the first voltage is compared with a first threshold value; and

detect a second receiver device operating at the second frequency based on a change in a second voltage measured at a second junction between the second coil and the second capacitor, wherein the change in the second voltage is compared with a second threshold value.

2. The wireless charging device of claim 1 , wherein the control unit is configured to:

generate a first control signal and transmit the first control signal to the driver unit when the first receiver device is detected; and

generate a second control signal when the second receiver device is detected and transmit the second control signal to the driver unit.

3. The wireless charging device of claim 2 , wherein the driver unit is configured to:

generate the first AC voltage signal having the first frequency based on the first control signal received from the control unit; and

generate the second AC voltage signal having the second frequency based on the second control signal received from the control unit.

4. The wireless charging device of claim 2 , wherein the control unit is configured to:

detect the first receiver device operating at the first frequency if the change in the first voltage at the first junction is greater than the first threshold value; and

detect the second receiver device operating at the second frequency if the change in the second voltage at the second junction is greater than the second threshold value.

5. The wireless charging device of claim 4 , wherein the control unit is configured to:

monitor the change in the first voltage measured at the first junction after detecting the first receiver device; and

confirm a presence of the first receiver device until the change in the first voltage is greater than the first threshold value for at least a first predetermined time interval.

6. The wireless charging device of claim 5 , wherein the control unit is configured to detect a foreign object if the change in the first voltage is greater than the first threshold value for more than the first predetermined time interval, wherein the control unit is further configured to control the driver unit to stop transmitting the first AC voltage signal if the foreign object is detected.

7. The wireless charging device of claim 5 , wherein the driver unit is configured to continuously transmit the first AC voltage signal having the first frequency to the first receiver device until the presence of the first receiver device is confirmed.

8. The wireless charging device of claim 5 , wherein the control unit is configured to:

monitor the change in the second voltage measured at the second junction after detecting the second receiver device; and

confirm a presence of the second receiver device until the change in the second voltage is greater than the second threshold value for at least a second predetermined time interval.

9. The wireless charging device of claim 8 , wherein the control unit is configured to detect a foreign object if the change in the second voltage is greater than the second threshold value for more than the second predetermined time interval, wherein the control unit is further configured to control the driver unit to stop transmitting the second AC voltage signal if the foreign object is detected.

10. The wireless charging device of claim 8 , wherein the driver unit is configured to continuously transmit the second AC voltage signal having the second frequency to the second receiver device until the presence of the second receiver device is confirmed.

11. The wireless charging device of claim 8 , wherein the driver unit is configured to generate the first AC voltage signal having the first frequency for a first time period for detecting the first receiver device.

12. The wireless charging device of claim 11 , wherein the driver unit is configured to generate the second AC voltage signal having the second frequency for a second time period for detecting the second receiver device.

13. The wireless charging device of claim 12 , wherein the second time period is after a third predetermined time interval from the first time period.

14. A method comprising:

generating, by a driver unit, one of a first alternating current (AC) voltage signal having a first frequency and a second alternating current (AC) voltage signal having a second frequency;

transmitting, by a first coil and a first capacitor in a transmitting unit, the first AC voltage signal having the first frequency, if the first AC voltage signal is generated;

transmitting, by a second coil and a second capacitor in the transmitting unit, the second AC voltage signal having the second frequency, if the second AC voltage signal is generated;

detecting, by a control unit, a first receiver device based on a change in a first voltage measured at a first junction between the first coil and the first capacitor; and

detecting, by the control unit, a second receiver device based on a change in a second voltage measured at a second junction between the second coil and the second capacitor.

15. The method of claim 14 , further comprising:

generating, by the control unit, a first control signal if the first receiver device is detected and transmitting the first control signal to the driver unit;

generating, by the control unit, a second control signal if the second receiver device is detected and transmitting the second control signal to the driver unit;

generating, by the driver unit, the first AC voltage signal having the first frequency based on the first control signal received from the control unit; and

generating, by the driver unit, the second AC voltage signal having the second frequency based on the second control signal received from the control unit.

16. The wireless charging unit according to claim 1 , wherein the control unit includes:

a first peak detecting unit coupled with the first junction between the first coil and the first capacitor, the first peak detecting unit configured to measure the change in the first voltage at the first junction and a first comparator coupled with first peak detecting unit and configured to compare the change in the first voltage with the first threshold value; and

a second peak detecting unit coupled with the second junction between the second coil and the second capacitor, the second peak detecting unit configured to measure the change in the second voltage at the second junction and a second comparator coupled with second peak detecting unit and configured to compare the change in the second voltage with the second threshold value.

17. The wireless charging unit according to claim 16 , wherein the control unit includes a detector electrically coupled to the first comparator and the second comparator, wherein the detector is configured to generate the first control signal when the change in the first voltage level is greater than the first threshold level.

18. The wireless charging unit according to claim 16 , wherein the control unit includes a detector electrically coupled to the first comparator and the second comparator, wherein the detector is configured to generate the second control signal when the change in the second voltage level is greater than the second threshold level.

19. A wireless charging device comprising:

a driver unit configured to generate at least a first and second alternating current (AC) voltage signal, wherein the first AC voltage signal has a first frequency and the second AC voltage signal has a second frequency;

a transmitting unit coupled to the driver unit, the transmitting unit including at least a first coil and a first capacitor coupled in series and configured to transmit the first AC voltage signal, and a second coil and a second capacitor coupled in series and configured to transmit the second AC voltage signal; and

a control unit coupled to the transmitting unit and the driver unit, the control unit configured to measure at least a first voltage change at a first junction between the first coil and the first capacitor, and measure a second voltage change at a second junction between the second coil and the second capacitor;

wherein the control unit detects a first receiver device when the first voltage change is greater than a first threshold value and detects a second receiver when the second voltage change is greater than a second threshold value.

20. The wireless charging device according to claim 19 , wherein the control unit generates a first control signal and sends the first control signal to the driver unit when the control unit detects the first receiver device.

21. The wireless charging device according to claim 20 , wherein the control unit generates a second control signal and send the second control signal to the driver unit when the control unit detects the second receiver device.