METHODS FOR DETECTING AND IDENTIFYING A RECEIVER IN AN INDUCTIVE POWER TRANSFER SYSTEM

• US 20170229927A1
• Filed: 04/21/2017
• Published: 08/10/2017
• Est. Priority Date: 05/02/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: PowerbyProxi Limited (Apple Inc.)
• Inventors: ROBERTSON, Daniel James
• Granted Patent: US 10,601,264 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 19/04 Measuring peak values or amplitude or envelope of ac or of pulses
• CPC Class Codes: G01R 19/15 Indicating the presence of current
• CPC Class Codes: G01R 27/2611 Measuring inductance
• CPC Class Codes: H02J 50/10 using inductive coupling
• 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 50/90 involving detection or optimisation of position, e.g. alignment

Abstract

A method for detecting the presence of a receiver in an inductively coupled power transfer system having a transmitter and receiver. The method includes switching on a transmitter converter at a first frequency, measuring the inrush current and determining whether there is a receiver present. In another method, the inrush current is measured for a range of transmitter frequencies, and the variation in current is used to determine where there is a receiver present. In another method, the inrush current is measured when there is a change in voltage in the transmitter, and the variation in current is used to determine where there is a receiver present. In another method, the current supplied to the transmitter converter is measured over two transmitter frequencies, and the variation in current is used to determine where there is a receiver present. In another method, the current supplied to the transmitter converter is measured over two transmitter voltages, and the variation in current is used to determine where there is a receiver present.

Claims

1. A method for detecting the presence of a receiver in an inductively coupled power transfer system, the system including a transmitter comprising:

a. an inductor for generating an alternating magnetic field;

b. a converter for supplying an alternating current to the inductor; and

c. a sensor for measuring the current supplied to the converter, including the steps of;

i. switching on the converter at a first frequency;

ii. measuring the amplitude of the current during the inrush period; and

iii. determining whether the amplitude indicates that there is a receiver.

2. The method as claimed in claim 1, wherein the inductor is a coil.

3. The method as claimed in claim 1, wherein the converter is connected to a controller.

4. The method as claimed in claim 3, wherein the controller controls the converter to supply an alternating current of a desired frequency.

5. The method as claimed in claim 1, wherein the converter is a non-resonant half bridge converter.

6. The method as claimed in claim 1, wherein the method includes the step of initially controlling the converter to supply an alternating current, with a non-resonant frequency, higher than the first frequency, so as to remove biases in capacitors present in the inductively coupled power transfer system.

7. The method as claimed in claim 6, wherein the non-resonant frequency is between 1 and 10 MHz.

8. The method as claimed in claim 1, wherein the first frequency is between 100 and 1,000 kHz.

9. The method as claimed in claim 1, wherein the sensor measures one or more peak amplitudes during the inrush period.

10. The method as claimed in claim 1, wherein the sensor is connected to a controller.

11. The method as claimed in claim 10, wherein the controller determines whether there is a potential receiver present if the magnitude of one of the peak amplitudes exceeds a magnitude threshold.

12. The method as claimed in claim 10, wherein the controller is configured to disregard peak amplitudes that are characteristic of the transient currents in the transmitter.

13. The method as claimed in claim 1, wherein the method includes proceeding with the further step, on the basis of the result of step (iii) of claim 1, of one or more of:

i. controlling the converter so that power is transmitted to the receiver;

ii. conducting further tests to verify the presence of a receiver;

iii. conducting further tests to identify whether the receiver is a receiver that is compatible with the inductively coupled power transfer system,

iv. switching the transmitter to a standby mode;

or

v. switching the transmitter off.

14. A method for detecting a receiver in an inductively coupled power transfer system, the system comprising:

a. an inductor for generating an alternating magnetic field;

b. a converter for supplying an alternating current to the inductor; and

c. a sensor for measuring the current supplied to the converter, including the steps of;

i. switching on the converter at a plurality of frequencies within a frequency range;

ii. measuring a peak amplitude of the current during the inrush period for each frequency within the frequency range;

iii. analysing the measured peak amplitudes over the frequency range to establish whether there is a maximum; and

iv. detecting a receiver on the basis of the maximum satisfying a predetermined parameter.

15. The method as claimed in claim 14, wherein the inductor is a coil.

16. The method as claimed in claim 14, wherein the converter is connected to a controller.

17. The method as claimed in claim 16, wherein the controller controls the converter to supply an alternating current of a desired frequency to the inductor.

18. The method as claimed in claim 14, wherein the converter is a non-resonant half bridge converter.

19. The method as claimed in claim 14, wherein the method includes the step of, before switching the converter on to each of the plurality of frequencies, controlling the converter to supply an alternating current, with a non-resonant frequency, higher than the frequency range, so as to remove biases in capacitors present in the inductively coupled power transfer system.

20. The method as claimed in claim 19, wherein the non-resonant frequency is between 1 and 10 MHz.

21. The method as claimed in claim 14, wherein the sensor measures one or more peak amplitudes during the inrush period for each of the plurality of frequencies.

22. The method as claimed in claim 14, wherein the sensor is connected to a controller.

23. The method as claimed in claim 22, wherein the controller is configured to disregard peak amplitudes that are characteristic of the transient currents in the transmitter.

24. The method as claimed in claim 22, wherein the measured peak amplitudes are analysed by the controller.

25. The method as claimed in claim 14, wherein the frequency range is 100 to 1,000 kHz.

26. The method as claimed in claim 14, wherein the method includes the step of determining properties of any maxima, including the width of the maximum, the magnitude of the peak of the maximum and the frequency at which the maximum occurs.

27. The method as claimed in claim 14, wherein the predetermined parameter is the frequency at which the maximum occurs

28. The method as claimed in claim 27, a receiver is identified if the frequency at which the maximum occurs is about 140 kHz.

29. The method as claimed in claim 14, wherein the predetermined parameter is the width of the maximum.

30. The method as claimed in claim 29, the width of the maximum occurs is more than 50 kHz.

31. The method as claimed in claim 14, wherein the predetermined parameter is the magnitude of the peak of the maximum.

32. The method as claimed in claim 14, wherein the method includes proceeding with the further step, on the basis of the result of detecting a receiver on the basis of the maximum satisfying a predetermined parameter, of one or more of:

i. controlling the converter so that power is transmitted to the receiver;

ii. conducting further tests to verify the presence of a receiver;

iii. conducting further tests to identify whether the receiver is a receiver that is compatible with the inductively coupled power transfer system,

iv. switching the transmitter to a standby mode;

or

v. switching the transmitter off.

33. A method for detecting the absence of a receiver in an inductively coupled power transfer system, the system including a transmitter comprising:

a. an inductor for generating an alternating magnetic field;

b. a converter for supplying an alternating current to the inductor; and

c. a sensor for measuring the current supplied to the converter, including the steps of;

i. controlling the transmitter to transmit power at a first voltage;

ii. increasing the voltage to a second voltage;

iii. measuring the amplitude of the current during the inrush period; and

iv. determining whether the amplitude indicates that there is a receiver.

34. The method as claimed in claim 33, wherein the inductor is a coil.

35. The method as claimed in claim 33, wherein the converter is connected to a controller.

36. The method as claimed in claim 35, wherein the controller controls the converter to supply an alternating current of a desired voltage.

37. The method as claimed in claim 33, wherein the converter is a push-pull converter.

38. The method as claimed in claim 33, wherein the first voltage is between 20 and 30 volts.

39. The method as claimed in claim 33, wherein the second voltage is less than 4% larger than the first voltage.

40. The method as claimed in claim 33, wherein the method includes the step of decreasing the voltage to a third voltage before increasing the voltage to the second voltage.

41. The method as claimed in claim 40, wherein the third voltage is less than 4% smaller than the first voltage.

42. The method as claimed in claim 40, wherein the second voltage is larger than the third voltage and smaller than 4% larger than the first voltage.

43. The method as claimed in claim 33, wherein the sensor measures one or more peak amplitudes during the inrush period.

44. The method as claimed in claim 33, wherein the sensor is connected to a controller.

45. The method as claimed in claim 44, wherein the controller determines whether there is a potential receiver present if the magnitude of one of the peak amplitudes exceeds a magnitude threshold.

46. The method as claimed in claim 44, wherein the controller is configured to disregard peak amplitudes that are characteristic of the transient currents in the transmitter.

47. The method as claimed in claim 33, wherein the method includes proceeding with the further step, on the basis of the result of determining whether the amplitude indicates that there is a receiver, of one or more of:

i. continuing to control the converter so that power is transmitted to the receiver;

ii. conducting further tests to verify the presence of a receiver;

iii. conducting further tests to identify whether the receiver is a receiver that is compatible with the inductively coupled power transfer system,

iv. switching the transmitter to a standby mode;

or

v. switching the transmitter off.

48. The method as claimed in claim 40, wherein the third voltage is zero, and the voltage of the converter is maintained at the third voltage for a test period and then increased to the second voltage, and wherein the following steps are repeated for a plurality of test periods that increase in length, ranging from a first test period to a second test period:

i. controlling the transmitter to transmit power at a first voltage;

ii. increasing the voltage to a second voltage;

iii. measuring the amplitude of the current during the inrush period; and

iv. determining whether the amplitude indicates that there is a receiver.

49. The method as claimed in claim 48, wherein the first test period is sufficiently short so as to have negligible effect on power transfer when the voltage of the converter is at the first voltage or the second voltage.

50. The method as claimed in claim 48, wherein the second test period is sufficiently long so that a suitable inrush current is observed when measuring the amplitude of the current during the inrush period.