Wireless power transmission device and wireless power charging system including the same

1. A wireless power transmission device comprising:

a mounting member;

a first terminal and a second terminal mounted on the mounting member; and

a transmission coil mounted on the mounting member,

wherein the transmission coil includes:

an outer transmission coil connected to the first terminal; and

an inner transmission coil connected to the second terminal, and extending from the outer transmission coil and spaced apart from the outer transmission coil and being wound inside the outer transmission coil to correspond to the outer transmission coil, having a radius less than that of the outer transmission coil,

wherein the outer transmission coil and the inner transmission coil are symmetrical with respect to a center of each of the outer and inner transmission coils, and

wherein the inner transmission coil is wound 20 mm to 30 mm apart from the outer transmission coil.

2. The wireless power transmission device according to claim 1 , wherein the outer transmission coil and the inner transmission coil have one turn.

3. The wireless power transmission device according to claim 1 , wherein the outer transmission coil is a double coil.

4. A wireless power charging system comprising:

a wireless power transmission device including an outer transmission coil and an inner transmission coil; and

a wireless power reception device including a reception coil,

wherein a distance between the outer transmission coil and the inner transmission coil is half a width of the reception coil.

5. The wireless power charging system according to claim 4 , wherein a distance between the outer transmission coil and the inner transmission coil is in a range from 20 mm to 30 mm.

6. The wireless power charging system according to claim 4 , wherein the outer transmission coil and the inner transmission coil have one turn.

7. The wireless power charging system according to claim 4 , wherein the outer transmission coil is a double coil.

8. The wireless power charging system according to claim 7 , wherein change in coupling coefficient with the reception coil according to position when the outer transmission coil is the double coil is less than change in coupling coefficient with the reception coil according to position when the outer transmission coil is a single coil.

9. The wireless power charging system according to claim 7 , wherein a charging region when the outer transmission coil is the double coil is equal to a charging region when the outer transmission coil is a single coil.

10. The wireless power charging system according to claim 7 , wherein a coupling coefficient of a transmission coil including the outer transmission coil and the inner transmission coil and the reception coil is an average of a coupling coefficient of a transmission coil including only the outer transmission coil and the reception coil and a coupling coefficient of a transmission coil including the inner transmission coil and the reception coil.

11. The wireless power charging system according to claim 10 , wherein change in coupling coefficient of the transmission coil including the outer transmission coil and the inner transmission coil and the reception coil as being farther from a center of the inner transmission coil is small.

12. The wireless power charging system according to claim 10 , wherein change in coupling coefficient of the transmission coil including the outer transmission coil and the inner transmission coil and the reception coil is less than change in coupling coefficient of the transmission coil including only the outer transmission coil and the reception coil as being farther from a center of the inner transmission coil.

13. The wireless power charging system according to claim 10 , wherein change in coupling coefficient of the transmission coil including the outer transmission coil and the inner transmission coil and the reception coil is less than change in coupling coefficient of the transmission coil including only the inner transmission coil and the reception coil as being farther from a center of the inner transmission coil.

14. The wireless power charging system according to claim 10 ,

wherein the coupling coefficient of the transmission coil including the outer transmission coil and the inner transmission coil and the reception coil is 0.13 at the center of the inner transmission coil, and

wherein the coupling coefficient of the transmission coil including only the outer transmission coil and the reception coil is 0.2 at the center of the outer transmission coil and the coupling coefficient of the transmission coil including only the inner transmission coil and the reception coil is 0.05 at the center of the inner transmission coil.