Load impedance detection for static or dynamic adjustment of passive loads
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.
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.