CONTACTLESS POWER TRANSMISSION SYSTEM

• US 20100187912A1
• Filed: 01/20/2010
• Published: 07/29/2010
• Est. Priority Date: 01/27/2009
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Electric Works Company Limited (Panasonic Holdings Corporation)
• Inventors: KITAMURA, Hiroyasu, IWAO, Seiichi, OTA, Tomohiro
• Granted Patent: US 8,258,653 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• 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 7/00714 in response to battery charging or discharging current

Abstract

Power saving is promoted by oscillating only power transmission coil contributing to contactless charging without using any communication means.

Claims

1. A contactless power transmission system, comprising a power transmitting device including power transmission coils for transmitting power, and a power receiving device including a power receiving coil to be magnetically coupled to the power transmission coils,

wherein

the power transmitting device includes:

a placing portion, on which the power receiving device is to be placed,

a plurality of power transmission coils arranged below the placing portion,

an oscillator for oscillating the respective power transmission coils while separately exciting them,

a detector for detecting the inductances of the respective power transmission coils, and

a determiner for determining the placed position of the power receiving device on the placing portion based on the inductances of the respective power transmission coils detected by the detector; and

the oscillator specifies a plurality of power transmission coils to be oscillated based on the placed position determined by the determiner and sets parameters of currents to flow into the respective power transmission coils so as to mutually shift the waveforms of currents to flow into the plurality of specified power transmission coils.

2. A contactless power transmission system according to claim 1, wherein the oscillator specifies the plurality of power transmission coils to be oscillated based on the placed position determined by the determiner and mutually shifts the phases of the currents to flow into the plurality of specified power transmission coils.

3. A contactless power transmission system according to claim 1, wherein the oscillator specifies the plurality of power transmission coils to be oscillated based on the placed position determined by the determiner and changes the frequencies of the currents to flow into the plurality of specified power transmission coils.

4. A contactless power transmission system according to claim 1, wherein the oscillator preferably specifies the plurality of power transmission coils to be oscillated based on the placed position determined by the determiner and changes the magnitudes of the currents to flow into the plurality of specified power transmission coils.

5. A contactless power transmission system according to claim 2, wherein:

the plurality of power transmission coils are arranged in a reticular pattern; and

the oscillator causes currents of two phases shifted from each other by 90°

to flow into adjacent ones of the plurality of power transmission coils to be oscillated.

6. A contactless power transmission system according to claim 3, wherein:

the plurality of power transmission coils are arranged in a reticular pattern; and

the oscillator causes different currents whose frequencies are at a ratio of 1;

m (m>

0) to flow into adjacent ones of the plurality of power transmission coils to be oscillated.

7. A contactless power transmission system according to claim 4, wherein:

the plurality of power transmission coils are arranged in a reticular pattern; and

the oscillator causes different currents whose magnitudes are at a ratio of 1;

m (m>

0) to flow into adjacent ones of the plurality of power transmission coils to be oscillated.

8. A contactless power transmission system according to claim 2, wherein:

the respective power transmission coils are of the same size and the centers thereof are arranged at vertices of a right triangular mesh; and

the oscillator causes currents of three phases shifted from each other by 120°

to flow into three power transmission coils arranged at the respective vertices of a right triangle to which the power transmission coil arranged below the placed position determined by the determiner belongs.

9. A contactless power transmission system according to claim 3, wherein:

the respective power transmission coils are of the same size and the centers thereof are arranged at vertices of a right triangular mesh; and

the oscillator causes currents whose frequencies are at a ratio of 1;

m;

n (m, n>

0) to flow into three power transmission coils arranged at the respective vertices of a right triangle to which the power transmission coil arranged below the placed position determined by the determiner belongs.

10. A contactless power transmission system according to claim 4, wherein:

the respective power transmission coils are of the same size and the centers thereof are arranged at vertices of a right triangular mesh; and

the oscillator causes currents whose magnitudes are at a ratio of 1;

m;

n (m, n>

0) to flow into three power transmission coils arranged at the respective vertices of a right triangle to which the power transmission coil arranged below the placed position determined by the determiner belongs.

11. A contactless power transmission system according to claim 1, wherein the oscillator intermittently oscillates the power transmission coils other than those to be oscillated.

12. A contactless power transmission system according to claim 1, wherein the detector detects the inductances of the respective power transmission coils based on the voltages of the respective power transmission coils.

13. A contactless power transmission system according to claim 1, wherein the detector is constructed by a plurality of feedback coils corresponding to the respective power transmission coils and magnetically coupled to the respective power transmission coils and detects the inductances of the respective power transmission coils based on the voltages of the respective feedback coils.

14. A contactless power transmission system according to claim 1, wherein the determiner sets weighting values for the respective power transmission coils such that the weighting values for the respective power transmission coils increase as the voltages of the respective power transmission coils decrease and determines the placed position based on the set weighting values.

15. A contactless power transmission system according to claim 1, wherein the respective power transmission coils are preferably so arranged in a layered manner as to displace the centers thereof from each other.

16. A contactless power transmission system according to claim 1, wherein the oscillator intermittently oscillates all the power transmission coils when the determiner determines that no power receiving device is placed on the placing portion.

17. A contactless power transmission system according to claim 1, wherein the power transmission coils are larger in size than the power receiving coil.

18. A contactless power transmission system according to claim 1, wherein the power receiving device includes:

a secondary battery to be charged by power received by the power receiving coil,

a rectifying circuit for rectifying and smoothing a current received by the power receiving coil,

a switching element for turning on and off a connection between the rectifying circuit and the secondary battery, and

a controller for controlling the switching element so that a current supplied to the secondary battery becomes constant.

19. A contactless power transmission system according to claim 14, wherein:

the determiner determines the size of the power receiving device placed on the placing portion according to the weighting values set for the respective power transmission coils; and

the oscillator changes power to be transmitted to the power receiving device according to the size of the power receiving device determined by the determiner.

20. A contactless power transmission system according to claim 19, wherein the determiner determines the sizes of respective power receiving devices based on the weighting values when a plurality of power receiving devices are placed on the placing portion.