Wireless power transfer system
View Patent ↗A wireless power transmission system according to an exemplary embodiment of the present invention includes: a source coil at a primary side; a load coil at a secondary side; and at least two intermediate coils coupled with each other in an insulated manner with a predetermined turn ratio with respect to the source coil. An effective inductance of the source coil is increased by the at least two intermediate coils and thus a coupling coefficient between the source coil and the load coil is increased.
1. A wireless power transmission system comprising:
a source coil at a primary side;
a load coil at a secondary side; and
at least two intermediate coils that are not wired together and are coupled with each other in an insulated manner, the at least two intermediate coils having a predetermined turn ratio with respect to the source coil, wherein an effective inductance of the source coil is increased by the two intermediate coils, and thus, a coupling coefficient between the source coil and the load coil is increased.
2. The wireless power transmission system of claim 1 , wherein the at least two intermediate coils are provided completely inside of the source coil.
3. The wireless power transmission system of claim 2 , wherein one of the at least two intermediate coils is provided inside of the other intermediate coil.
4. The wireless power transmission system of claim 2 , wherein one of the at least two intermediate coils is provided in parallel with the other intermediate coil.
5. The wireless power transmission system of claim 1 , further comprising at least two first resonance capacitors coupled to each of the at least two intermediate coils.
6. The wireless power transmission system of claim 5 , further comprising a circuitry for converting an input voltage to a square wave at the primary side, wherein an operation frequency of the converting the input voltage to the square wave is set to a frequency that is lower than a resonance frequency of one of the at least two intermediate coils.
7. The wireless power transmission system of claim 6 , wherein the resonance frequency is inversely proportional to a square root of a value that results from multiplying a leakage inductance of one of the at least two intermediate coils by a capacitance of a first resonance capacitor coupled to the one intermediate coil.
8. The wireless power transmission system of claim 5 , wherein a leakage inductance of each of the at least two intermediate coils reflected to the primary side is coupled to a leakage inductance and a magnetizing inductance of the source coil, and
wherein a value of the leakage inductance of each of the at least two intermediate coils reflected to the primary side is determined by multiplying the leakage inductance of each of the at least two intermediate coils by a square of a turn ratio between the source coil and each of the at least two intermediate coils.
9. The wireless power transmission system of claim 5 , wherein a capacitance of each of the at least two first resonance capacitors reflected to the primary side is coupled in series to a leakage inductance of each of the at least two intermediate coils reflected to the primary side, and a value of the capacitance of each of the at least two first resonance capacitors reflected to the primary side is determined by dividing the capacitance of each of the at least two first resonance capacitors by a square of a turn ratio between the source coil and each of the at least two intermediate coils.
10. The wireless power transmission system of claim 1 , wherein each of the at least two intermediate coils is reflected to the primary side, and an effective inductance of the source coil is boosted at least two times by an impedance of the at least two intermediate coils reflected to the primary side.
11. The wireless power transmission system of claim 10 , further comprising at least two first resonance capacitors coupled to each of the at least two intermediate coils.
12. The wireless power transmission system of claim 11 , wherein a boosting effect of the effective inductance of the source coil is generated from a resonance frequency that is based on each of the at least two intermediate coils and each of the at least two first resonance capacitors.
13. The wireless power transmission system of claim 12 , further comprising a second resonance capacitor coupled to the source coil.
14. The wireless power transmission system of claim 13 , further comprising a circuitry for supplying a square wave between the second resonance capacitor and the source coil by converting an input voltage.
15. The wireless power transmission system of claim 13 , further comprising a third resonance capacitor coupled to the load coil.
16. The wireless power transmission system of claim 15 , further comprising a rectification circuit coupled to the third resonance capacitor and the load coil.