FILTER FOR IMPROVED DRIVER CIRCUIT EFFICIENCY AND METHOD OF OPERATION

• US 20120242284A1
• Filed: 03/20/2012
• Published: 09/27/2012
• Est. Priority Date: 03/25/2011
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wheatley, Charles Edward III, Low, Zhen Ning, Toncich, Stanley Slavko, Nguyen, Ngo Van, Wheeland, Cody B.
• Granted Patent: US 10,381,874 B2
• Time in Patent Office: Days
• US Class Current: 320/108
• 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 50/60 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

Abstract

This disclosure provides systems, methods and apparatus for increasing the efficiency of an amplifier when driven by a variable load. In one aspect a transmitter device is provided. The transmitter device includes a driver circuit characterized by an efficiency. The driver circuit is electrically connected to a transmit circuit characterized by an impedance. The transmitter device further includes a filter circuit electrically connected to the driver circuit and configured to modify the impedance to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit. The impedance is characterized by a complex impedance value that is within a range defined by a real first impedance value and a second real impedance value. A ratio of the first real impedance value to the second real impedance value is at least two to one.

Claims

1. A transmitter device, comprising:

a driver circuit characterized by an efficiency, the driver circuit being electrically connected to a transmit circuit characterized by an impedance; and

a filter circuit electrically connected to the driver circuit and configured to modify the impedance to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit, the impedance being characterized by a complex impedance value, the complex impedance value being within a range defined by a first real impedance value and a second real impedance value, a ratio of the first real impedance value to the second real impedance value being at least two to one.

2. The transmitter device of claim 1, wherein the ratio is one of at least five to one and at least ten to one.

3. The transmitter device of claim 2, wherein the first real impedance value comprises substantially 8 ohms and the second real impedance value comprises substantially 80 ohms.

4. The transmitter device of claim 1, wherein the ratio is a first ratio, wherein the range is further defined by a first imaginary impedance value and a second imaginary impedance value, wherein a second ratio of a first magnitude of a difference between the first imaginary impedance and the second imaginary impedance value to a second magnitude of a difference between the first real impedance value and the second real impedance value is substantially equal to at least one of one to two, two to three, one to one, three to two, and two to one.

5. The transmitter device of claim 4, wherein the first real impedance value is substantially four ohms, wherein the second real impedance value is substantially forty ohms, wherein the first imaginary impedance value is substantially negative four ohms, and wherein the second imaginary impedance value is substantially 50 ohms.

6. The transmitter device of claim 1, wherein the transmit circuit comprises a transmit coil electrically connected to the output of the filter circuit, the transmit coil configured to wirelessly transmit power to charge or power a receiver device.

7. The transmitter device of claim 1, wherein the transmit circuit is configured to wirelessly transmit power to charge or power a plurality of receiver devices, wherein each of the plurality of receiver devices is configured to cause a change in the impedance when positioned to wirelessly receive power from the transmit circuit.

8. The transmitter device of claim 1, wherein the driver circuit comprises a switching amplifier circuit.

9. The transmitter device of claim 1, wherein the driver circuit comprises a class E amplifier circuit.

10. The transmitter device of claim 1, wherein the impedance of the transmit circuit comprises a reactance that is substantially zero before the impedance is modified.

11. The transmitter device of claim 1, wherein a value of the modified impedance comprises a complex value comprising a real part corresponding to a resistance value and an imaginary part corresponding to a non-zero reactance value.

12. The transmitter device of claim 1, wherein the filter circuit comprises at least one of a low pass filter, a high pass filter, or any combination thereof.

13. The transmitter device of claim 12, wherein the low pass filter comprises a 3-pole Butterworth filter with a 3 dB bandwidth of an operating frequency of the driver circuit.

14. The transmitter device of claim 1, wherein a cutoff frequency of the filter circuit is higher or lower than an operating frequency of the driver circuit.

15. The transmitter device of claim 1, wherein the filter circuit is further configured to substantially remove harmonic components of a signal generated by the driver circuit operating at an operating frequency.

16. The transmitter device of claim 1, wherein an amount of power provided to the transmit circuit increases as an amount of a resistive portion of the impedance increases.

17. The transmitter device of claim 1, wherein a first magnitude of the impedance at which a maximum power amount is output by the driver circuit is higher than a second magnitude of the impedance at which maximum efficiency of the driver circuit is provided.

18. The transmitter device of claim 1, wherein the filter circuit comprises a ladder network of reactive circuits, each of the reactive circuits comprising a combination of reactive components.

19. The transmitter device of claim 1, further comprising an impedance adjustment element configured to cause a reactive shift between the driver circuit and the filter circuit.

20. A method for filtering a transmit signal, comprising:

driving a signal using a driver circuit characterized by an efficiency;

providing the signal to a transmit circuit characterized by an impedance; and

modifying the impedance to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit, the impedance being characterized by a complex impedance value, the complex impedance value being within a range defined by a first real impedance value and a second real impedance value, a ratio of the first real impedance value to the second real impedance value being at least two to one.

21. The method of claim 20, wherein the ratio is one of at least five to one and at least ten to one.

22. The method of claim 21, wherein the first real impedance value comprises substantially 8 ohms and the second real impedance value comprises substantially 80 ohms.

23. The method of claim 20, wherein the ratio is a first ratio, wherein the range is further defined by a first imaginary impedance value and a second imaginary impedance value, wherein a second ratio of a first magnitude of a difference between the first imaginary impedance and the second imaginary impedance value to a second magnitude of a difference between the first real impedance value and the second real impedance value is substantially equal to at least one of one to two, two to three, one to one, three to two, and two to one.

24. The method of claim 23, wherein the first real impedance value is substantially four ohms, wherein the second real impedance value is substantially forty ohms, wherein the first imaginary impedance value is substantially negative four ohms, and wherein the second imaginary impedance value is substantially 50 ohms.

25. The method of claim 20, further comprising wirelessly transmitting power to charge or power a receiver device using the transmit circuit.

26. The method of claim 20, further comprising wirelessly transmitting power to charge or power a plurality of receiver devices using the transmit circuit, wherein each of the plurality of receiver devices is configured to cause a change in the impedance when positioned to wirelessly receive power from the transmit circuit.

27. The method of claim 20, wherein the driver circuit comprises a class E amplifier.

28. The method of claim 20, wherein the driver circuit comprises a switching amplifier.

29. The method of claim 20, wherein the impedance of the transmit circuit comprises a reactance that is substantially zero before modifying the impedance.

30. The method of claim 20, wherein a value of the modified impedance comprises a complex value comprising a real part corresponding to a resistance value and an imaginary part corresponding to a non-zero reactance value.

31. The method of claim 20, wherein modifying comprises modifying using a filter circuit comprising at least one of a low pass filter, a high pass filter, or any combination thereof.

32. The method of claim 31, wherein the low pass filter comprises a 3-pole Butterworth filter with a 3 dB bandwidth of an operating frequency of the driver circuit.

33. The method of claim 31, wherein a cutoff frequency of the filter circuit is higher or lower than an operating frequency of the driver circuit.

34. The method of claim 20, further comprising substantially removing harmonic components of the signal generated by the driver circuit operating at an operating frequency.

35. The method of claim 20, wherein an amount of power provided to the transmit circuit increases as an amount of a resistive portion of the impedance increases.

36. The method of claim 20, wherein a first magnitude of the impedance at which a maximum power amount is output by the driver circuit is higher than a second magnitude of the impedance at which maximum efficiency of the driver circuit is provided.

37. The method of claim 20, wherein modifying the impedance comprises modifying using a filter circuit comprising a ladder network of reactive circuits, each of the reactive circuits comprising a combination of reactive components.

38. The transmitter device of claim 20, wherein modifying comprises modifying using a filter circuit and an impedance adjustment element configured to cause a reactive shift of a transformed impedance produced by the filter circuit.

39. A transmitter device, comprising:

means for transmitting being characterized by an impedance;

means for driving characterized by an efficiency, the means for driving being electrically connected to the means for transmitting; and

means for filtering electrically connected to the means for driving and configured to modify the impedance to maintain the efficiency of the means for driving at a level that is within 20% of a maximum efficiency of the means for driving, the impedance being characterized by a complex impedance value, the complex impedance value being within a range defined by a first real impedance value and a second real impedance value, a ratio of the first real impedance value to the second real impedance value being at least two to one.

40. The transmitter device of claim 39, wherein the ratio is one of at least five to one and at least ten to one.

41. The transmitter device of claim 40, wherein the first real impedance value comprises substantially 8 ohms and the second real impedance value comprises substantially 80 ohms.

42. The transmitter device of claim 39, wherein the ratio is a first ratio, wherein the range is further defined by a first imaginary impedance value and a second imaginary impedance value, wherein a second ratio of a first magnitude of a difference between the first imaginary impedance and the second imaginary impedance value to a second magnitude of a difference between the first real impedance value and the second real impedance value is substantially equal to at least one of one to two, two to three, one to one, three to two, and two to one.

43. The transmitter device of claim 42, wherein the first real impedance value is substantially four ohms, wherein the second real impedance value is substantially forty ohms, wherein the first imaginary impedance value is substantially negative four ohms, and wherein the second imaginary impedance value is substantially 50 ohms.

44. The transmitter device of claim 39, wherein the means for transmitting comprises a transmit circuit comprising a transmit coil electrically connected to the output of the means for filtering, the transmit coil configured to wirelessly transmit power to charge or power a receiver device.

45. The transmitter device of claim 39, wherein the means for transmitting is configured to wirelessly transmit power to charge or power a plurality of receiver devices, wherein each of the plurality of receiver devices is configured to cause a change in the impedance when positioned to wirelessly receive power from the means for transmitting.

46. The transmitter device of claim 39, wherein the means for driving comprises a switching amplifier.

47. The transmitter device of claim 39, wherein the means for driving comprises a class E amplifier.

48. The transmitter device of claim 39, wherein the impedance of the means for transmitting comprises a reactance that is substantially zero before the impedance is modified.

49. The transmitter device of claim 39, wherein a value of the modified impedance comprises a complex value comprising a real part corresponding to a resistance value and an imaginary part corresponding to a non-zero reactance.

50. The transmitter device of claim 39, wherein the means for filtering comprises at least one of a low pass filter, a high pass filter, or any combination thereof.

51. The transmitter device of claim 39, wherein the means for filtering comprises a 3-pole Butterworth filter with a 3 dB bandwidth of an operating frequency of the means for driving.

52. The transmitter device of claim 39, wherein a cutoff frequency of the means for filtering is higher or lower than an operating frequency of the means for driving.

53. The transmitter device of claim 39, wherein the means for filtering is further configured to substantially remove harmonic components of a signal generated by the driver circuit operating at an operating frequency.

54. The transmitter device of claim 39, wherein an amount of power provided to the means for transmitting increases as an amount of a resistive portion of the impedance increases.

55. The transmitter device of claim 39, wherein a first magnitude of the impedance at which a maximum power amount is output by the means for driving is higher than a second magnitude of the impedance at which maximum efficiency of the means for driving is provided.

56. The transmitter device of claim 39, wherein the means for filtering comprises a ladder network of reactive circuits, each of the reactive circuits comprising a combination of reactive components.

57. The transmitter device of claim 39, further comprising means for shifting an impedance configured to cause a reactive shift between the means for driving and the means for filtering.

58. A method for designing a power transmitter apparatus, the method comprising:

selecting characteristics of at least two elements of a group of elements including a driver circuit, a filter circuit, and an impedance shifting element; and

determining, based on the selected characteristics of the at least two elements, a characteristic of a non-selected element such that the driver circuit operates at a level that is within 20% of a maximum efficiency over a range of complex impedance values, the range being defined by a first real impedance value and a second real impedance value, a ratio of the first real impedance value to the second impedance value being at least two to one.

59. The method of claim 58, wherein the filter circuit comprises a ladder network circuit comprising a variable number of poles.

60. The method of claim 58, wherein the driver is electrically connected to the impedance shifting element and the filter circuit.

61. The method of claim 58, wherein characteristics of the driver circuit comprise at least one of a driver circuit frequency and a driver circuit impedance.

62. The method of claim 58, wherein characteristics of the filter circuit comprises at least one of a number of poles, a type of filter circuit selected from a low pass filter, a high pass filter, or a combination thereof, a characteristic impedance, and a cutoff frequency.

63. The method of claim 58, wherein characteristics of the impedance shifting element comprises an amount of impedance shift.

64. The method of claim 58, wherein the driver circuit comprises a switching amplifier circuit of a type including at least a class E amplifier circuit.

65. The method of claim 58, wherein the impedance shifting element comprises at least on of an inductor, a capacitor, or any combination thereof.

66. The method of claim 58, wherein the driver circuit comprises a switching amplifier circuit of a type including at least a class E amplifier circuit, wherein a filter circuit is electrically connected between a series inductor of the switching amplifier and a series capacitor of the switching amplifier circuit.

67. The method of claim 58, wherein the impedance shifting element comprises one of a series element inherent in the driver circuit.

68. The method of claim 58, wherein the ratio is one of at least five to one and at least ten to one.

69. The method of claim 68, wherein the first real impedance value comprises substantially 8 ohms and the second real impedance value comprises substantially 80 ohms.

70. The method of claim 58, wherein the ratio is a first ratio, wherein the range is further defined by a first imaginary impedance value and a second imaginary impedance value, wherein a second ratio of a first magnitude of a difference between the first imaginary impedance and the second imaginary impedance value to a second magnitude of a difference between the first real impedance value and the second real impedance value is substantially equal to at least one of one to two, two to three, one to one, three to two, and two to one.

71. The method of claim 70, wherein the first real impedance value is substantially four ohms, wherein the second real impedance value is substantially forty ohms, wherein the first imaginary impedance value is substantially negative four ohms, and wherein the second imaginary impedance value is substantially 50 ohms.