Power receiver, wireless power transfer system, and kQ-value calculation method

• US 10,305,333 B2
• Filed: 11/14/2016
• Issued: 05/28/2019
• Est. Priority Date: 05/22/2014
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Shimokawa, Satoshi, Uchida, Akiyoshi
• Primary Examiner(s): Fureman, Jared
• Assistant Examiner(s): Barnett, Joel
• Application Number:
  US15/350,243
• Publication Number:
  US 20170063166A1
• Time in Patent Office: 925 Days
• Field of Search: None
• 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 50/402 the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
• 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: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A power receiver which wirelessly receives power from at least one power source using one of magnetic field resonance and electric field resonance, including a power receiver coil, an internal circuit, a power detection resistor, a switch, a power reception control unit, and a communication circuit unit. The power receiver coil wirelessly receives the power from the power source, and the internal circuit uses the power obtained by the power receiver coil. The power detection resistor detects the power obtained by the power receiver coil, and the switch applies a received power voltage obtained by the power receiver coil by switching to the power detection resistor. The power reception control unit controls the power detection resistor and the switch, and the communication circuit unit performs communication with the power source, comprising detection information of a received power and power supply timing information.

Claims

1. A power receiver configured to wirelessly receive power from at least one power source using one of magnetic field resonance and electric field resonance, the power receiver comprising:

a power receiver coil configured to wirelessly receive the power from the power source;

an internal circuit configured to use the power obtained by the power receiver coil;

a power detection resistor configured to detect the power obtained by the power receiver coil;

a switch configured to apply a received power voltage obtained by the power receiver coil by switching to the power detection resistor;

a power reception control unit configured to control the power detection resistor and the switch; and

a communication circuit unit configured to perform communication with the power source, and the communication circuit unit comprising detection information of a received power and power supply timing information, wherein

the power reception control unit is configured to

control a resistance value of the power detection resistor to calculate the received power from a resistance ratio between a resistance value of the power receiver coil and a resistance value of the power detection resistor, and the received power voltage obtained by the power receiver coil, and

transfer the detection information of the calculated received power to the transmission circuit via the communication circuit unit.

2. The power receiver according to claim 1, wherein

the switch is configured to apply the received power voltage obtained by the power receiver coil by switching to the power detection resistor and the internal circuit.

3. The power receiver according to claim 2, wherein

the power detection resistor comprises a variable resistor, the resistance value of which is variably controlled by the power reception control unit, and

the switch connects the power receiver coil by switching to the power detection resistor and the internal circuit.

4. The power receiver according to claim 2, wherein

the power detection resistor comprises a plurality of resistor elements, and

the switch is configured to connect the power receiver coil by switching to one of the plurality of resistor elements and the internal circuit.

5. The power receiver according to claim 1, wherein

the power receiver coil comprises:

a power receiver resonance coil configured to wirelessly receive the power from the power source; and

a power extraction coil configured to receive the power from the power receiver resonance coil using electromagnetic induction, and

the switch comprises;

a first switch configured to apply a first received power voltage obtained by the power receiver resonance coil by switching to the power detection resistor; and

a second switch configured to apply a second received power voltage obtained by the power extraction coil by switching to the internal circuit.

6. The power receiver according to claim 1, wherein

the power reception control unit comprises a memory which stores a loss of the power receiver coil.

7. The power receiver according to claim 1, wherein

the internal circuit comprises a secondary battery, and

the secondary battery is charged using the power obtained by the power receiver coil.

8. A wireless power transfer system comprising at least one power source, and at least one power receiver which wirelessly receives power from the power source using one of magnetic field resonance and electric field resonance, wherein

the power receiver comprises:

a power receiver coil configured to wirelessly receive the power from the power source;

an internal circuit configured to use the power obtained by the power receiver coil;

a power detection resistor configured to detect the power obtained by the power receiver coil;

a switch configured to apply a received power voltage obtained by the power receiver coil by switching to the power detection resistor;

a power reception control unit configured to control the power detection resistor and the switch; and

a first communication circuit unit configured to perform communication with the power source, comprising detection information of a received power and power supply timing information, and

the power source comprises;

a power source coil configured to wirelessly transfer power to the power receiver;

a power transfer control unit configured to calculate a kQ value on the basis of a transferred power to the power receiver and the detection information from the power receiver; and

a second communication circuit unit configured to perform communication with the power receiver, comprising the detection information and the power supply timing information, wherein

the power reception control unit is configured to

control a resistance value of the power detection resistor to calculate the received power from a resistance ratio between a resistance value of the power receiver coil and a resistance value of the power detection resistor, and the received power voltage obtained by the power receiver coil, and

transfer the detection information of the calculated received power to the transmission circuit via the communication circuit unit.

9. The wireless power transfer system according to claim 8, wherein

the power transfer control unit comprises a memory which stores a loss of the power source coil.

10. A kQ-value calculation method for obtaining, a kQ value of a power receiver which wirelessly receives power from at least one power source using one of magnetic field resonance and electric field resonance, as a product of a k value indicating a degree of coupling of one of a magnetic field and an electric field between the power source and the power receiver and a Q value indicating a degree of loss of one of a magnetic field and an electric field, wherein

the power receiver comprises:

a power receiver coil which wirelessly receives the power from the power source;

an internal circuit which uses the power obtained by the power receiver coil; and

a power detection resistor which detects the power obtained by the power receiver coil, and

the kQ-value calculation method comprises;

controlling a resistance value of the power detection resistor to calculate a received power from a resistance ratio between a resistance value of the power receiver coil and a resistance value of the power detection resistor, and the received power voltage obtained by the power receiver coil;

calculating a measurement efficiency from a transferred power output from the power source, and the received power; and

calculating the kQ value of the power receiver from the resistance ratio and the measurement efficiency.

11. The kQ-value calculation method according to claim 10, further comprising:

calculating the Q value from a loss of the power receiver coil in the power receiver and a loss of the power source coil in the power source; and

calculating a k value from the calculated kQ value.

12. The kQ-value calculation method according to claim 10, wherein

the calculating the kQ value is performed in test power transfer in which low power is transferred from the power source.

13. The kQ-value calculation method according to claim 10, wherein

the calculating the kQ value is performed in the power source.