Wireless power transmitter

• US 9,190,850 B2
• Filed: 01/03/2012
• Issued: 11/17/2015
• Est. Priority Date: 09/18/2009
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Onizuka, Kohei, Ueno, Takeshi
• Primary Examiner(s): Amrany, Adi
• Application Number:
  US13/342,381
• Publication Number:
  US 20130002034A1
• Time in Patent Office: 1,414 Days
• Field of Search: 307/104
• US Class Current: 1/1
• 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 50/80 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: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems

Abstract

An example wireless power transmitter is configured for wirelessly transmitting a signal to a power receiving apparatus including a first resonance circuit and a load circuit. The first resonance circuit includes a power receiving coil and a first capacitor. The example wireless power transmitter includes a power supply that has a variable oscillation frequency and generates a signal having the oscillation frequency; a second resonance circuit that transmits the signal to the power receiving apparatus; a measuring unit that measures a signal reflection coefficient, the signal reflection coefficient being determined based on magnitude of the signal and magnitude of a signal reflected on the second resonance circuit to the power supply; and a controller that detects a value of the oscillation frequency making the signal reflection coefficient smaller than or equal to a threshold value, and calculates an electromagnetic coupling coefficient between the power transmission coil and the power receiving coil based on the detected value.

Claims

1. A wireless power transmitter for wirelessly transmitting a signal to a power receiving apparatus having a first resonance circuit and a load circuit, wherein the first resonance circuit includes a power receiving coil and a first capacitor, the wireless power transmitter comprising:

a power supply that has a variable oscillation frequency and generates signals;

a second resonance circuit that transmits the signals to the power receiving apparatus;

a measuring unit that measures signal reflection coefficients associated with respective ones of the generated signals; and

a controller that controls one or both of the oscillation frequency and a parameter of the second resonance circuit based on a calculated electromagnetic coupling coefficient between the power transmission coil and the power receiving coil, the electromagnetic coupling coefficient being calculated, before transmitting signals for powering the load circuit, by at least controlling the power supply to generate signals each having a respective oscillation frequency;

controlling the measuring unit to measure signal reflection coefficients, each signal reflection coefficient being determined based on magnitude of one of the signals and magnitude of a corresponding signal reflected on the second resonance circuit to the power supply;

detecting a value of the oscillation frequency making the signal reflection coefficient smaller than or equal to a threshold value; and

calculating the electromagnetic coupling coefficient based on the detected value.

2. The wireless power transmitter according to claim 1, further comprising:

a transmitter that transmits a first control signal to the power receiving apparatus so that the first control signal indicates change of a capacitance value for the first capacitor and/or a parameter for the load circuit, wherein the controller generates the first control signal based on the electromagnetic coupling coefficient.

3. The wireless power transmitter according to claim 2,

wherein the controller controls a capacitance value for the first capacitor so that a frequency range includes the oscillation frequency making the signal reflection coefficient smaller than or equal to the threshold value.

4. The wireless power transmitter according to claim 3,

wherein the controller controls a parameter for the load circuit so as to increase a difference between a maximum value and a minimum value for the signal reflection coefficient.

5. The wireless power transmitter according to claim 2,

wherein the controller controls resonance characteristics of a semiconductor device to be different from resonance characteristics of the wireless power transmitter and the power receiving apparatus, the semiconductor device having a third resonance circuit and a second load circuit, the third resonance circuit being provided with a coil and a capacitor.

6. The wireless power transmitter according to claim 5,

wherein the controller changes an inductance value for the coil of the third resonance circuit or a capacitance value for the capacitor of the third resonance circuit.

7. The wireless power transmitter according to claim 5,

wherein the controller short-circuits or opens a switch provided for the coil of the third resonance circuit.

8. The wireless power transmitter according to claim 1,

wherein the controller controls the oscillation frequency based on the electromagnetic coupling coefficient.

9. The wireless power transmitter according to claim 1,

wherein the second resonance circuit includes a power transmission coil and a second capacitor.

10. The wireless power transmitter according to claim 9,

wherein the controller controls a capacitance value of the second capacitor based on the electromagnetic coupling coefficient.

11. The wireless power transmitter according to claim 10,

wherein the controller controls a capacitance value for the second capacitor so that a frequency range includes the oscillation frequency making the signal reflection coefficient smaller than or equal to the threshold value.

12. The wireless power transmitter according to claim 11,

wherein the controller controls a parameter for the load circuit so as to increase a difference between a maximum value and a minimum value for the signal reflection coefficient.

13. The wireless power transmitter according to claim 1,

wherein the controller detects two values of the oscillation frequency making the signal reflection coefficient smaller than or equal to the threshold value, and calculates the electromagnetic coupling coefficient based on a difference between the two values.

14. The wireless power transmitter according to claim 13, further comprising:

storage that stores a previously calculated correspondence relation of the difference between the two values to the electromagnetic coupling coefficient,

wherein the controller references the correspondence relation stored in the storage based on the difference between the two values to calculate the electromagnetic coupling coefficient.

15. The wireless power transmitter according to claim 1,

wherein the controller detects the value of the oscillation frequency making the signal reflection coefficient be a peak value, and calculates the electromagnetic coupling coefficient based on the detected value.

16. The wireless power transmitter according to claim 1,

wherein the controller detects the value of the oscillation frequency making the signal reflection coefficient be a local minimal value, and calculates the electromagnetic coupling coefficient based on the detected value.

17. A wireless power transmission controlling method for a wireless power transmitter comprising a power supply having a variable oscillation frequency and a resonance circuit including a coil and a capacitor, the method comprising:

controlling either one or both of the oscillation frequency and a capacitance value of the capacitor based on a calculated electromagnetic coupling coefficient, the electromagnetic coupling coefficient being calculated before transmitting signals for powering a load circuit by at least

generating, by the power supply, signals each having a respective oscillation frequency;

measuring signal reflection coefficients, each signal reflection coefficient being determined based on magnitude of one of the signals and magnitude of a corresponding signal reflected on the resonance circuit to the power supply;

detecting a value of the oscillation frequency making the signal reflection coefficient smaller than or equal to a threshold value; and

calculating the electromagnetic coupling coefficient based on the detected value.

18. The method according to claim 17,

wherein two values of the oscillation frequency making the signal reflection coefficient smaller than or equal to the threshold value are detected, and the electromagnetic coupling coefficient of the coil is calculated based on a difference between the two values.

19. The method according to claim 18, further comprising:

referencing a previously calculated correspondence relation of the difference between the two values to the electromagnetic coupling coefficient to calculate the electromagnetic coupling coefficient.

20. The method according to claim 17,

wherein the value of the oscillation frequency making the signal reflection coefficient be a peak value is detected, and the electromagnetic coupling coefficient is calculated based on the detected value.

21. The method according to claim 17,

wherein the value of the oscillation frequency making the signal reflection coefficient be a local minimal value is detected, and the electromagnetic coupling coefficient is calculated based on the detected value.

22. A power receiving apparatus for wirelessly transmitting a signal to a wireless power transmitter having a first resonance circuit, wherein the first resonance circuit includes a power transmission coil and a first capacitor, the power receiving apparatus comprising:

a power supply that has a variable oscillation frequency and generates signals;

a second resonance circuit that includes a power receiving coil and a second capacitor and transmits the signals to the wireless power transmitter;

a measuring unit that measures signal reflection coefficients associated with respective ones of the generated signals; and

a controller that controls one or both of the oscillation frequency and a parameter of the second resonance circuit based on a calculated electromagnetic coupling coefficient between the power transmission coil and the power receiving coil, the electromagnetic coupling coefficient being calculated, before the wireless power transmitter transmits signals for powering a load circuit of the power receiving apparatus, by at least controlling the power supply to generate signals each having a respective oscillation frequency;

controlling the measuring unit to measure signal reflection coefficients, each signal reflection coefficient being determined based on magnitude of one of the signals and magnitude of a corresponding signal reflected on the second resonance circuit to the power supply;

detecting a value of the oscillation frequency making the signal reflection coefficient smaller than or equal to a threshold value;

calculating the electromagnetic coupling coefficient based on the detected value; and

controlling either one or both of an oscillation frequency and a capacitance value of the second capacitor based on the electromagnetic coupling coefficient.

23. The apparatus according to claim 22,

wherein the controller detects two values of the oscillation frequency making the signal reflection coefficient smaller than or equal to the threshold value, and calculates the electromagnetic coupling coefficient based on a difference between the two values.

24. The apparatus according to claim 23, further comprising:

storage that stores a previously calculated correspondence relation of the difference between the two values to the electromagnetic coupling coefficient,

wherein the controller references the correspondence relation stored in the storage based on the difference between the two values to calculate the electromagnetic coupling coefficient.

25. The apparatus according to claim 22,

wherein the controller detects the value of the oscillation frequency making the signal reflection coefficient be a peak value, and calculates the electromagnetic coupling coefficient based on the detected value.

26. The apparatus according to claim 22,

wherein the controller detects the value of the oscillation frequency making the signal reflection coefficient be a local minimal value, and calculates the electromagnetic coupling coefficient based on the detected value.