POWER TRANSMITTING DEVICE, ELECTRONIC EQUIPMENT AND WIRELESS POWER TRANSMISSION SYSTEM

• US 20150054351A1
• Filed: 03/29/2013
• Published: 02/26/2015
• Est. Priority Date: 03/30/2012
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Deguchi, Futoshi, Yuasa, Yasuhito
• Granted Patent: US 9,431,989 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/0042 characterised by the mechanical construction
• CPC Class Codes: H03H 7/38 Impedance-matching networks

Abstract

Reduction in the power transmission efficiency due to imprecise positioning between a primary power transmission coil and a secondary power reception coil is avoided. For transmitting electric power in a wireless manner to an electronic device including a secondary power reception coil and configured to receive electric power via the secondary power reception coil, a power transmission device includes a primary power transmission coil and a power transmission circuit unit for supplying electric power to the primary power transmission coil, and a transmission circuit unit is formed by the primary power transmission coil and the secondary power reception coil. A first impedance of an input end of the transmission circuit unit is matched with a second impedance of an output end of the transmission circuit unit by using a coupling coefficient between the primary power transmission coil and the secondary power reception coil.

Claims

1. A power transmission device for transmitting electric power in a wireless manner to an electronic device, the electronic device including a secondary power reception coil and being configured to receive electric power via the secondary power reception coil, the power transmission device comprising:

a primary power transmission coil; and

a power transmission circuit that supplies electric power to the primary power transmission coil;

a transmission circuit that comprises the primary power transmission coil and the secondary power reception coil,

wherein a first impedance of an input end of the transmission circuit is matched with a second impedance of an output end of the transmission circuit by using a coupling coefficient between the primary power transmission coil and the secondary power reception coil.

2. The power transmission device according to claim 1, wherein a first inductance of the primary power transmission coil has a value based on the coupling coefficient between the primary power transmission coil and the secondary power reception coil.

3. The power transmission device according to claim 2, wherein the value of the first inductance is determined based on a second inductance of the secondary power reception coil.

4. The power transmission device according to claim 3, wherein the value of the first inductance is determined based on the first impedance.

5. The power transmission device according to claim 4, wherein, when the power transmission circuit supplies AC electric power at angular frequency ω

to the primary power transmission coil,

ω

L₁=Z₁/K

ω

L₂=Z₂/K,

where L₁ is the first inductance, L₂ is the second inductance, Z₁ is the first impedance, and Z₂ is the second impedance, and K is the coupling coefficient.

6. The power transmission device according to claim 5, further comprising a primary capacitor that forms a series resonance circuit in cooperation with the primary power transmission coil.

7. The power transmission device according to claim 1, wherein the primary power transmission coil comprises a helical coil.

8. The power transmission device according to claim 7, wherein the primary power transmission coil comprises a linear conductor helically wound around a central axial line of the primary power transmission coil.

9. The power transmission device according to claim 7, wherein an open end of the primary power transmission coil has an area at least twice as large as an area of the secondary power reception coil.

10. An electronic device configured to receive electric power from a power transmission device, the power transmission device including a primary power transmission coil and transmitting electric power via the primary power transmission coil, the electronic device comprising:

a secondary power reception coil; and

a power reception circuit that receives electric power via the secondary power reception coil;

a transmission circuit that comprises the primary power transmission coil and the secondary power reception coil,

wherein a second impedance of an output end of the transmission circuit is matched with a first impedance of an input end of the transmission circuit by using a coupling coefficient between the primary power transmission coil and the secondary power reception coil.

11. A wireless power transmission system, comprising:

a transmission circuit including a primary power transmission coil and a secondary power reception coil;

a power transmission circuit that transmits power via the primary power transmission coil; and

a power reception circuit that receives power via the secondary power reception coil,

wherein a first impedance of an input end of the transmission circuit is matched with a second impedance of an output end of the transmission circuit by using a coupling coefficient between the primary power transmission coil and the secondary power reception coil.

12. The wireless power transmission system according to claim 11, wherein the primary power transmission coil comprises a helical coil.

13. The wireless power transmission system according to claim 12, wherein the primary power transmission coil comprises a linear conductor helically wound around a central axial line of the primary power transmission coil.

14. The wireless power transmission system according to claim 12, wherein an open end of the primary power transmission coil has a rectangular shape, the rectangular shape having a short side length less than four times the diameter of the secondary power reception coil and a long side length less than six times the diameter of the secondary power reception coil.