Load impedance detection for static or dynamic adjustment of passive loads

• US 9,071,284 B2
• Filed: 10/05/2012
• Issued: 06/30/2015
• Est. Priority Date: 10/21/2011
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wheeland, Cody B., Tseng, Ryan, Von Novak, William H
• Primary Examiner(s): Hollington, Jermele M
• Application Number:
  US13/646,553
• Publication Number:
  US 20130099807A1
• Time in Patent Office: 998 Days
• US Class Current: 1/1
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• 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: H03F 1/565 using inductive elements
• CPC Class Codes: H03F 3/2176 Class E amplifiers
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

This disclosure provides systems, methods and apparatus for detecting an impedance of a wireless power transmitter load. In one aspect, a method of determining a reactive condition of a wireless power transmitter apparatus is provided. The method comprises determining a value correlated to a voltage of a drain of a switching element of a driver circuit of the wireless power transmitter. The method further comprises determining a reactance load change based on the determined voltage.

Claims

1. A method of operating a wireless power transmitter, the method comprising:

determining a characteristic correlated to a voltage of a terminal of a switching element of a driver circuit of the wireless power transmitter; and

determining a reactance of a load based on the determined characteristic.

2. The method of claim 1, further comprising adjusting an impedance of the load based on the determined reactance of the load.

3. The method of claim 1, wherein determining the characteristic comprises sampling the characteristic at substantially the same time as a switching element transition.

4. The method of claim 1, wherein determining the characteristic comprises comparing the voltage to a threshold voltage.

5. The method of claim 1, wherein determining the characteristic comprises comparing the characteristic to a threshold characteristic.

6. The method of claim 5, wherein the threshold characteristic comprises a rectified voltage envelope.

7. The method of claim 5, wherein the threshold characteristic is proportional to an input voltage.

8. The method of claim 5, further comprising averaging a comparator output signal indicative of whether the characteristic exceeds a threshold.

9. The method of claim 1, wherein the characteristic comprises a digital characteristic indicating a voltage level above or below a limit, based on the reactance of the load.

10. The method of claim 9, further comprising sampling the digital characteristic using a flip-flop clocked at substantially the same time as a switching element transition.

11. The method of claim 1, wherein the characteristic comprises an analog characteristic indicating the reactance of the load.

12. The method of claim 11, further comprising sampling and holding the analog characteristic for a period of time.

13. The method of claim 1, wherein the load comprises a transmit circuit and/or resonator.

14. The method of claim 1, wherein the terminal comprises a source terminal.

15. The method of claim 1, wherein the terminal comprises a drain terminal.

16. An apparatus configured to determine a reactive condition of a wireless power transmitter, the apparatus comprising:

a first circuit configured to determine a characteristic correlated to a voltage of a terminal of a switching element of a driver circuit of the wireless power transmitter; and

a second circuit configured to determine a reactance of a load based on the determined characteristic.

17. The apparatus of claim 16, further comprising a circuit configured to adjust an impedance of the load based on the determined reactance of the load.

18. The apparatus of claim 16, wherein the first circuit comprises a sample-and-hold circuit configured to sample the characteristic at substantially the same time as a switching element transition.

19. The apparatus of claim 16, wherein the first circuit comprises a comparator configured to compare the voltage to a threshold voltage.

20. The apparatus of claim 16, wherein the first circuit comprises a comparator configured to compare the characteristic to a threshold characteristic.

21. The apparatus of claim 20, wherein the threshold characteristic comprises a rectified voltage envelope.

22. The apparatus of claim 20, wherein the threshold characteristic is proportional to an input voltage.

23. The apparatus of claim 19, further comprising a circuit configured to average a comparator output signal indicative of whether the characteristic exceeds a threshold.

24. The apparatus of claim 16, wherein the characteristic comprises a digital characteristic indicating a voltage level above or below a limit, based on the reactance of the load.

25. The apparatus of claim 24, further comprising a flip-flop configured to sample the digital characteristic using a flip-flop clocked at substantially the same time as a switching element transition.

26. The apparatus of claim 16, wherein the characteristic comprises an analog characteristic indicating the reactance of the load.

27. The apparatus of claim 26, further comprising a sample-and-hold circuit configured to sample the analog characteristic for a period of time.

28. The apparatus of claim 16, wherein the load comprises a transmit circuit and/or resonator.

29. The apparatus of claim 16, wherein the terminal comprises a source terminal.

30. The apparatus of claim 16, wherein the terminal comprises a drain terminal.

31. The apparatus of claim 16, wherein the first circuit comprises:

a drain voltage input;

a threshold voltage input;

a gate drive voltage input;

an output;

a comparator configured to compare the drain voltage input and the threshold voltage input, and to output a digital signal indicative of whether the drain voltage input is greater than the threshold voltage input; and

a flip-flop configured to receive the digital signal at a data input, to receive the gate drive voltage input at a clock input, to sample the digital signal on a rising or falling edge of the synchronized gate drive signal, and to output an inverted or non-inverted version of the sampled voltage at the output.

32. The apparatus of claim 31, wherein the first circuit further comprises a filter circuit configured to voltage divide and/or filter the drain voltage input.

33. The apparatus of claim 31, wherein the first circuit further comprises a voltage divider configured to voltage divide the threshold voltage.

34. The apparatus of claim 31, wherein the first circuit further comprises a delay circuit configured to receive the gate drive voltage input, to delay the gate drive voltage input, and to output a synchronized gate drive signal, and wherein the flip-flop is configured to receive synchronized gate drive signal at the clock input.

35. An apparatus for operating a wireless power transmitter, comprising:

means for determining a characteristic correlated to a voltage of a terminal of a switching element of a driver circuit of the wireless power transmitter; and

means for determining a reactance of a load based on the determined characteristic.

36. The apparatus of claim 35, further comprising means for adjusting an impedance of the load based on the determined reactance of the load.

37. The apparatus of claim 35, wherein the means for determining the characteristic comprises means for sampling the characteristic at substantially the same time as a switching element transition.

38. The apparatus of claim 35, wherein the means for determining the characteristic comprises means for comparing the voltage to a threshold voltage.

39. The apparatus of claim 35, wherein the means for determining the characteristic comprises means for comparing the characteristic to a threshold characteristic.

40. The apparatus of claim 39, wherein the threshold characteristic comprises a rectified voltage envelope.

41. The apparatus of claim 39, wherein the threshold characteristic is proportional to an input voltage.

42. The apparatus of claim 39, further comprising means for averaging a comparing means output signal indicative of whether the characteristic exceeds a threshold.

43. The apparatus of claim 35, wherein the characteristic comprises a digital characteristic indicating a voltage level above or below a limit, based on the reactance of the load.

44. The apparatus of claim 43, further comprising means for sampling the digital characteristic using a flip-flop clocked at substantially the same time as a switching element transition.

45. The apparatus of claim 35, wherein the characteristic comprises an analog characteristic indicating the reactance of the load.

46. The apparatus of claim 45, further comprising means for sampling and holding the analog characteristic for a period of time.

47. The apparatus of claim 35, wherein the load comprises a transmit circuit and/or resonator.

48. The apparatus of claim 35, wherein the terminal comprises a source terminal.

49. The apparatus of claim 35, wherein the terminal comprises a drain terminal.

50. A non-transitory computer-readable medium comprising code that, when executed, causes an apparatus to:

determine a characteristic correlated to a voltage of a terminal of a switching element of a driver circuit of a wireless power transmitter; and

determine a reactance of a load based on the determined characteristic.

51. The medium of claim 50, further comprising code that, when executed, causes the apparatus to adjust an impedance of the load based on the determined reactance of the load.

52. The medium of claim 50, further comprising code that, when executed, causes the apparatus to sample the characteristic at substantially the same time as a switching element transition.

53. The medium of claim 50, further comprising code that, when executed, causes the apparatus to compare the voltage to a threshold voltage.

54. The medium of claim 50, further comprising code that, when executed, causes the apparatus to compare the characteristic to a threshold characteristic.

55. The medium of claim 54, wherein the threshold characteristic comprises a rectified voltage envelope.

56. The medium of claim 54, wherein the threshold characteristic is proportional to an input voltage.

57. The medium of claim 54, further comprising code that, when executed, causes the apparatus to average a comparator output signal indicative of whether the characteristic exceeds a threshold.

58. The medium of claim 50, wherein the characteristic comprises a digital characteristic indicating a voltage level above or below a limit, based on the reactance of the load.

59. The medium of claim 58, further comprising code that, when executed, causes the apparatus to sample the digital characteristic using a flip-flop clocked at substantially the same time as a switching element transition.

60. The medium of claim 50, wherein the characteristic comprises an analog characteristic indicating the reactance of the load.

61. The medium of claim 60, further comprising code that, when executed, causes the apparatus to sample and hold the analog characteristic for a period of time.

62. The medium of claim 50, wherein the load comprises a transmit circuit and/or resonator.

63. The medium of claim 50, wherein the terminal comprises a source terminal.

64. The medium of claim 50, wherein the terminal comprises a drain terminal.