Impedance change detection in wireless power transmission

• US 9,136,914 B2
• Filed: 12/17/2009
• Issued: 09/15/2015
• Est. Priority Date: 01/22/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Von Novak, William H, Toncich, Stanley S, Rimini, Roberto, Lee, Kevin D
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): Mourad, Rasem
• Application Number:
  US12/641,219
• Publication Number:
  US 20100217553A1
• Time in Patent Office: 2,098 Days
• Field of Search: 307/104, 455/91, 455/107, 455/108
• US Class Current: 1/1
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• 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: H04B 5/77 for interrogation

Abstract

Exemplary embodiments are directed to wireless power transfer. Energy from a transmit antenna is coupled to internal signals on a transmitter. An impedance measurement circuit generates an impedance indication signal for indicating an impedance difference between the coupled internal signals by comparing them. A controller samples the impedance indication signal and determines digital signaling values responsive to changes in the impedance indication signal. The impedance measurement circuit measures one or more of magnitude difference of the internal signals, phase difference of the internal signals, and changes in power consumed by an amplifier coupled between the RF signal and the transmit antenna. A transmitter generates the electromagnetic field with a transmit antenna responsive to a Radio Frequency (RF) signal to create a coupling-mode region within a near field of the transmit antenna.

Claims

1. A wireless power transmitter, comprising:

a transmit antenna comprising a coil configured to transmit power via a magnetic field, the transmit antenna having an impedance that changes in response to a modulation of a load of a receiver;

a coupler, connected to the transmit antenna, the coupler configured to;

receive an amplified input signal,

provide a transmit signal based on the input signal to the transmit antenna, and

output a first signal comprising at least a portion of the transmit signal, the first signal being isolated from the input signal and the transmit signal;

a measurement circuit comprising;

a phase comparator circuit configured to receive the first signal and a second signal and to generate a phase difference signal indicating a phase difference between the first signal and the second signal, the second signal comprising at least a portion of the input signal, the phase difference signal indicative of reverse-link signaling values from the receiver based on changes in the impedance at the transmit antenna caused by the modulation of the load of the receiver, and

a magnitude measurement circuit configured to receive the first signal and the second signal and to output a magnitude difference signal indicating a magnitude difference between the first signal and the second signal, the magnitude difference further indicative of the reverse-link signaling values; and

a controller configured to sample the phase difference signal and the magnitude difference signal over a period of time, and to compare at least the phase difference signal with the magnitude difference signal and select the signal with a highest energy level, wherein the controller is configured to determine the reverse-link signaling values based on at least the selected signal.

2. The wireless power transmitter of claim 1, wherein the controller is further configured to determine a distance value comprising a square root of a sum of a square of the phase difference signal and a square of the magnitude difference signal.

3. The wireless power transmitter of claim 1, further comprising:

an amplifier electrically connected between a signal generator and the coupler; and

a load sensing circuit electrically connected to the amplifier and configured to detect a change in an amount of power used by the amplifier and to output a power change signal based on the change in the amount of power,

wherein the controller is further configured to determine signaling values based on changes of the power change signal.

4. The wireless power transmitter of claim 3, wherein the controller is further configured to:

determine an energy estimate value for each of a derivative of the phase difference signal, a derivative of the magnitude difference signal, and a derivative of the power change signal over the period of time;

select one of the phase difference signal, the magnitude difference signal and the power change signal with a highest energy estimate value;

determine a threshold for detecting signaling transitions based on the selected signal; and

determine the signaling values by comparing subsequent values of the selected signal to the threshold.

5. The wireless power transmitter of claim 4, wherein the controller is further configured to:

sum values of a plurality of peaks of the selected signal;

determine an average tail value corresponding to an average of amplitudes of the selected signal at an offset from the plurality of peak values of the selected signal; and

average the sum of the plurality of peaks with the average tail value.

6. The wireless power transmitter of claim 1, wherein an amount of power of the first signal is less than an amount of power of the transmit signal.

7. The wireless power transmitter of claim 1, wherein the coupler comprises a directional coupler configured to output the second signal, wherein the second signal comprises the at least a portion of the input signal, the second signal being isolated from the transmit signal and the first signal.

8. The wireless power transmitter of claim 7, wherein an amount of power of the second signal is less than an amount of power of the input signal.

9. The wireless power transmitter of claim 1, wherein the coupler comprises a non-directional coupler, and wherein the second signal is received from an oscillator used to generate the input signal.

10. The wireless power transmitter of claim 1, wherein the transmit antenna is configured to output the transmit signal to generate a coupling-mode region.

11. The wireless power transmitter of claim 1, further comprising a signal generator for generating the input signal at a coupling frequency.

12. The wireless power transmitter of claim 1, wherein the signaling values correspond to an information message from a wireless power receiver.

13. The wireless power transmitter of claim 1, wherein the controller is further configured to sample the difference signal over a period of time.

14. A method comprising:

transmitting power via a magnetic field to a receiver, an impedance of a transmit antenna changing in response to a modulation of a load of a receiver;

providing a transmit signal based on an amplified input signal to a transmit antenna;

generating a first signal comprising a portion of the transmit signal, the first signal being isolated from the input signal and the transmit signal;

generating a phase difference signal indicating a phase difference between the first signal and a second signal, the second signal comprising at least a portion of the input signal, the phase difference signal indicative of reverse-link signaling values from the receiver based on changes in the impedance at the transmit antenna caused by modulation of the load of the receiver;

generating a magnitude difference signal indicating a magnitude difference between the first signal and the second signal, the magnitude difference further indicative of the reverse-link signaling values;

sampling the phase difference signal and the magnitude difference signal over a period of time;

comparing at least the phase difference signal with the magnitude difference signal;

selecting the signal with a highest energy level; and

determining the reverse-link signaling values based on at least the selected signal.

15. The method of claim 14, further comprising determining a distance value comprising a square root of a sum of a square of a first value of the phase difference signal and a second value of the square of the magnitude difference signal.

16. The method of claim 14, further comprising:

generating a power change signal indicating a change in an amount of power used by an amplifier corresponding to a change in a load of the wireless power transmitter; and

generating signaling values based on changes in the power change signal.

17. The method of claim 16, further comprising:

determining an energy estimate value for each of a derivative of the phase difference signal over the period of time, a derivative of the magnitude difference signal over the period of time, and a derivative of the power change signal over the period of time;

selecting one of the phase difference signal, the magnitude difference signal, and the power change signal with the highest energy estimate;

determining a threshold for detecting signaling transitions based on the selected signal; and

determining the signaling values by comparing subsequent values of the selected signal to the threshold.

18. The method of claim 17, wherein determining the threshold comprises:

summing values of a plurality of peaks of the selected signal;

determining an average tail value corresponding to an average of amplitudes of the selected value at an offset from the plurality of peak values of the selected signal; and

averaging the sum of the plurality of peaks with the average tail value.

19. The method of claim 14, wherein an amount of power of the first signal is less than an amount of power of the transmit signal.

20. The method of claim 14, further comprising generating the second signal from a portion of the input signal, the second signal being isolated from the transmit signal and the first signal.

21. The method of claim 20, wherein an amount of power of the second signal is less than an amount of power of the input signal.

22. The method of claim 14, wherein the second signal is received from an oscillator used to generate the input signal.

23. The method of claim 14, further comprising outputting the transmit signal to generate a coupling-mode region.

24. The method of claim 14, further comprising generating the input signal at a coupling frequency.

25. The method of claim 14, wherein the signaling values correspond to an information message from a wireless power receiver.

26. The method of claim 14, further comprising sampling the difference signal over the period of time.

27. A wireless power transmitter comprising:

means for transmitting power via a magnetic field to a receiver, an impedance of the transmitting power means changing in response to a modulation of a load of the receiver;

means for providing a transmit signal based on an amplified input signal to the transmitting power means;

means for generating a first signal comprising a portion of the transmit signal, the first signal being isolated from the transmit signal and the input signal used to generate the transmit signal;

means for generating a phase difference signal indicating a phase difference between the first signal and a second signal, the second signal comprising at least a portion of the input signal, the phase difference signal indicative of reverse-link signaling values from the receiver based on changes in the impedance at the transmitting power means caused by the modulation of the load of the receiver;

means for generating a magnitude difference signal indicating a magnitude difference between the first signal and the second signal, the magnitude difference further indicative of the reverse-link signaling values;

means for sampling the phase difference signal and the magnitude difference signal over a period of time;

means for comparing at least the phase difference signal with the magnitude difference signal;

means for selecting the signal with a highest energy level; and

means for determining the reverse-link signaling values based on at least the selected signal.

28. The wireless power transmitter of claim 27, further comprising means for determining a distance value comprising a square root of a sum of a square of a first value of the phase difference signal and a second value of the square of the magnitude difference signal.

29. The wireless power transmitter of claim 27, further comprising:

means for generating a power change signal indicating a change in an amount of power used by an amplifier corresponding to a change in a load of the wireless power transmitter; and

means for determining signaling values based on changes in the power change signal.

30. The wireless power transmitter of claim 29, further comprising:

means for determining an energy estimate value for each of a derivative of the phase difference signal over the period of time, and a derivative of the magnitude difference signal over the period of time, and a derivative of the power change signal over the period of time;

means for selecting one of the phase difference signal, the magnitude difference signal, and the power change signal with the highest energy estimate;

means for determining a threshold for detecting signaling transitions based on the selected signal; and

means for determining the signaling values by comparing subsequent values of the selected signal to the threshold.

31. The wireless power transmitter of claim 30, wherein the means for determining the threshold comprises:

means for summing values of a plurality of peaks of the selected signal;

means for determining an average tail value corresponding to an average of amplitudes of the selected value at an offset from the plurality of peak values of the selected signal; and

means for averaging the sum of the plurality of peaks with the average tail value.

32. The wireless power transmitter of claim 27, wherein an amount of power of the first signal is less than an amount of power of the transmit signal.

33. The wireless power transmitter of claim 27, further comprising means for generating the second signal comprising a portion of the input signal, the second signal being isolated from the transmit signal and the first signal.

34. The wireless power transmitter of claim 33, wherein an amount of power of the second signal is less than an amount of power of the input signal.

35. The wireless power transmitter of claim 33, wherein the means for generating a first signal comprising a portion of the transmit signal and the means for generating the second signal comprising a portion of the input signal comprise a directional coupler.

36. The wireless power transmitter of claim 27, wherein the means for generating a first signal comprising a portion of the transmit signal comprises a non-directional coupler.

37. The wireless power transmitter of claim 27, wherein the second signal is received from an oscillator used to generate the input signal.

38. The wireless power transmitter of claim 27, further comprising means for outputting the transmit signal to generate a coupling-mode region.

39. The wireless power transmitter of claim 27, further comprising means for generating the input signal at a coupling frequency.

40. The wireless power transmitter of claim 27, wherein the signaling values correspond to a data message from a wireless power receiver.

41. The wireless power transmitter of claim 27, wherein the means for generating a difference signal indicating a difference between a characteristic of the first signal and a corresponding characteristic of the second signal comprises a measurement circuit.

42. The wireless power transmitter of claim 27, the means for determining signaling values based on changes in the difference signal comprises a controller.

43. A wireless power transmitter, comprising:

a transmit antenna configured to transmit a transmit signal via a magnetic field to transmit power at a level sufficient to power a receiver;

a transmit circuit configured to generate an input signal to drive the transmit antenna;

a phase comparator circuit configured to determine a phase difference between at least a portion of the transmit signal and at least a portion of the input signal, the phase difference changing in response to modulation of a load of the receiver according to signaling values;

a magnitude measurement circuit configured to determine a magnitude difference between the at least a portion of the transmit signal and the at least a portion of the input signal, the magnitude difference changing in response to modulation of the load of the receiver; and

a controller configured to compare at least the phase difference signal with the magnitude difference signal and select the signal with a highest energy level, and to determine a plurality of communication signaling values from the receiver based at least in part on the selected signal.