POWER TRANSMISSION SYSTEM AND POWER TRANSMISSION APPARATUS

• US 20120001493A1
• Filed: 03/11/2011
• Published: 01/05/2012
• Est. Priority Date: 06/30/2010
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Oodachi, Noriaki, Kudo, Hiroki, Ogawa, Kenichirou
• Granted Patent: US 9,124,307 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: G01V 3/101 by measuring the impedance of the search coil; by measuring features of a resonant circuit comprising the search coil measuring impedance or characteristics derived therefrom G01R27/00, e.g. quality factor G01R27/26
• 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 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A power transmission system includes a power transmission apparatus, a power receiving apparatus, and a foreign-substance detecting unit. The power transmission apparatus has a power transmission coil to wirelessly transmit electric power. The power receiving apparatus has a power receiving coil to wirelessly receive electric power from the power transmission apparatus. The foreign-substance detecting unit detects a foreign substance which is present between the power transmission coil and the power receiving coil. In addition, the power transmission apparatus includes a voltage supply, a power supply controller, the power transmission coil, and a first measurement unit. The power receiving apparatus includes the power receiving coil and a second measurement unit.

Claims

1. A power transmission system comprising:

a power transmission apparatus having a power transmission coil to wirelessly transmit electric power;

a power receiving apparatus having a power receiving coil to wirelessly receive electric power from the power transmission apparatus; and

a foreign-substance detecting unit to detect a foreign substance which is present between the power transmission coil and the power receiving coil,

wherein

the power transmission apparatus includes;

a voltage supply to be frequency-variable and capable of outputting a first AC signal;

a power supply controller to vary a frequency of the first AC signal in a frequency range from a first frequency to a second frequency;

the power transmission coil to resonate at a first resonance frequency and to generate a magnetic field by receiving the first AC signal; and

a first measurement unit to measure a first reflectance in the frequency range two or more times, the first reflectance being at least one of a voltage reflectance of the first AC signal, an AC reflectance of the first AC signal, and a power reflectance of the first AC signal;

wherein

the power receiving apparatus includes;

the power receiving coil to resonate at a second resonance frequency and to generate a second AC signal by receiving the magnetic field, the second AC signal being passed through a load; and

a second measurement unit to measure a second reflectance in the frequency range two or more times, the second reflectance being at least one of a voltage reflectance of the second AC signal, an AC reflectance of the second AC signal, and a power reflectance of the second AC signal; and

wherein

the foreign-substance detecting unit uses a first peaking frequency and a second peaking frequency to detect the foreign substance, the first peaking frequency being a frequency at which the first reflectance reaches a local minimum, the second peaking frequency being a frequency at which the second reflectance reaches a local minimum.

4. The system according to claim 1, wherein

the power receiving apparatus further includes a load controller to control the resistance value of the load to be constant during measurement periods of time for the first measurement unit and the second measurement unit.

6. The system according to claim 1, wherein

the foreign-substance detecting unit judges that the foreign substance is present if the first peaking frequency is higher than the first resonance frequency.

8. The system according to claim 1, wherein

the foreign-substance detecting unit judges that the foreign substance is present if the second peaking frequency is higher than the second resonance frequency.

10. The system according to claim 1, wherein

the foreign-substance detecting unit further uses the number of local minimums of the first reflectance in the frequency range to detect the foreign substance.

12. The system according to claim 1, wherein

the power transmission apparatus further includes a first matching circuit to perform impedance matching between the voltage supply and the power transmission coil;

the power receiving apparatus further includes a second matching circuit to perform impedance matching between the power receiving coil and the load; and

the first measurement unit and the second measurement unit measure after the first matching circuit and the second matching circuit perform the respective impedance matching.

2. A power transmission system comprising:

a power transmission apparatus having a power transmission coil to wirelessly transmit electric power;

a power receiving apparatus having a power receiving coil to wirelessly receive electric power from the power transmission apparatus; and

a foreign-substance detecting unit to detect a foreign substance which is present between the power transmission coil and the power receiving coil,

wherein

the power transmission apparatus includes;

a voltage supply to be frequency-variable and capable of outputting a first AC signal;

a power supply controller to vary a frequency of the first AC signal in a frequency range from a first frequency to a second frequency;

the power transmission coil to resonate at a first resonance frequency and to generate a magnetic field by receiving the first AC signal;

a first measurement unit to measure a first reflectance and first power in the frequency range two or more times, the first reflectance being at least one of a voltage reflectance of the first AC signal, an AC reflectance of the first AC signal, and a power reflectance of the first AC signal, the first power being transmitted by the power transmission coil;

wherein

the power receiving apparatus includes;

the power receiving coil to resonate at a second resonance frequency and to generate a second AC signal in response to the magnetic field;

a second measurement unit to measure second power in the frequency range two or more times, the second power being supplied to a load; and

wherein

the foreign-substance detecting unit uses a first peaking frequency and a third peaking frequency to detect the foreign substance, the first peaking frequency being a frequency at which the first reflectance reaches a local minimum, the third peaking frequency being a frequency at which a power transmission efficiency reaches a local maximum, the power transmission efficiency being determined by the first electric power and the second electric power.

3. The system according to claim 2, wherein

the power receiving apparatus further includes a load controller to control a resistance value of the load through which the second AC signal passes;

and

the foreign-substance detecting unit further uses the resistance value of the load controlled by the load controller to detect the foreign substance.

5. The system according to claim 2, wherein

the power receiving apparatus further includes a load controller to control the resistance value of the load to be constant during measurement periods of time for the first measurement unit and the second measurement unit.

7. The system according to claim 2, wherein

the foreign-substance detecting unit judges that the foreign substance is present if the first peaking frequency is higher than the first resonance frequency.

9. The system according to claim 2, wherein

the foreign-substance detecting unit judges that the foreign substance is present if the third peaking frequency is higher than the third resonance frequency.

11. The system according to claim 2, wherein

the foreign-substance detecting unit further uses the number of local minimums of the first reflectance in the frequency range to detect the foreign substance.

13. The system according to claim 2, wherein

the power transmission apparatus further includes a first matching circuit to perform impedance matching between the voltage supply and the power transmission coil;

the power receiving apparatus further includes a second matching circuit to perform impedance matching between the power receiving coil and the load; and

the first measurement unit and the second measurement unit measure after the first matching circuit and the second matching circuit perform the respective impedance matching.

14. A power transmission apparatus using a transmission coil to wirelessly transmit electric power to a power receiving apparatus having a power receiving coil, comprising:

a voltage supply to be frequency-variable and capable of outputting a first AC signal;

a power supply controller to vary a frequency of the first AC signal in a frequency range from a first frequency to a second frequency;

a power transmission coil to resonate at a first resonance frequency and to generate a magnetic field by receiving the first AC signal;

a first measurement unit to measure a first reflectance in the frequency range two or more times, the first reflectance being at least one of a voltage reflectance of the first AC signal, an AC reflectance of the first AC signal, and a power reflectance of the first AC signal;

a receiving unit to receive a piece of information of a second peaking frequency at which at least one of a voltage reflectance of a second AC signal, a current reflectance of the second AC signal, and a power reflectance of the second AC signal reaches a local minimum, the second AC signal being generated by the magnetic field via the power receiving coil,

wherein

a foreign substance between the power transmission coil and the power receiving coil is detected by the use of a first peaking frequency at which the first reflectance reaches a local minimum and the second peaking frequency.

15. A power transmission apparatus using a transmission coil to wirelessly transmit electric power to a power receiving apparatus having a power receiving coil, comprising:

a voltage supply to be frequency-variable and capable of outputting a first AC signal;

a power supply controller to vary a frequency of the first AC signal in a frequency range from a first frequency to a second frequency;

a power transmission coil to resonate at a first resonance frequency and to generate a magnetic field by receiving the first AC signal;

a first measurement unit to measure a first reflectance and first electric power in the frequency range two or more times, the first reflectance being at least one of a voltage reflectance of the first AC signal, an AC reflectance of the first AC signal, and a power reflectance of the first AC signal, the first electric power being transmitted by the power transmission coil;

a receiving unit to receive a piece of information of second electric power of a second AC signal to be generated by the magnetic field via the power receiving coil,

wherein

a foreign substance between the power transmission coil and the power receiving coil is detected by the use of a first peaking frequency at which the first reflectance reaches a local minimum and a third peaking frequency at which a power transmission efficiency reaches a local maximum, the power transmission efficiency being determined by the first electric power and the second electric power.