Methods for detecting and identifying a receiver in an inductive power transfer system

• US 10,601,264 B2
• Filed: 04/21/2017
• Issued: 03/24/2020
• Est. Priority Date: 05/02/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Robertson, Daniel James
• Primary Examiner(s): Barnie, Rexford N
• Assistant Examiner(s): Parries, Dru
• Application Number:
  US15/493,857
• Publication Number:
  US 20170229927A1
• Time in Patent Office: 1,068 Days
• Field of Search: 307104
• 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 a receiver in an inductively coupled power transfer system having:

a coil for generating an alternating magnetic field;

a converter for supplying an alternating current to the coil; and

a sensor for measuring the current supplied to the converter;

the method comprising;

operating the converter at a plurality of frequencies within a frequency range;

determining a peak amplitude of the current, measured using the sensor, during an inrush period for each of the plurality of frequencies;

analyzing a characteristic of the determined peak amplitudes within the frequency range; and

detecting a receiver on the basis of the characteristic satisfying a predetermined parameter.

2. The method as claimed in claim 1, further comprising:

before operating the converter at each of the plurality of frequencies, operating the converter to supply an alternating current, with a non-resonant frequency, higher than the frequency range, to remove biases in capacitors present in the inductively coupled power transfer system.

3. The method as claimed in claim 2, wherein the non-resonant frequency is between 1 and 10 MHz.

4. The method as claimed in claim 1, comprising:

while determining a peak amplitude of the current during the inrush period for each of the plurality of frequencies, disregarding peak amplitudes that are below a threshold.

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

6. The method as claimed in claim 1,

wherein analyzing a characteristic of the determined peak amplitudes within the frequency range comprises:

identifying a maximum;

determining properties of the identified maximum, including the width of the identified maximum, the magnitude of the peak of the identified maximum, or the frequency at which the maximum occurs.

7. The method as claimed in claim 6, wherein the predetermined parameter comprises the frequency at which the identified maximum occurs.

8. The method as claimed in claim 6, wherein the maximum has a width and the predetermined parameter comprises the width of the maximum.

9. The method as claimed in claim 8, wherein detecting a receiver on the basis of the characteristic satisfying a predetermined parameter comprises detecting the receiver based on a determination of whether the width of the identified maximum spans more than 50 kHz.

10. The method as claimed in claim 6, wherein the predetermined parameter comprises the magnitude of the peak of the identified maximum.

11. The method as claimed in claim 1, further comprising:

in accordance with the result of detecting a receiver on the basis of the characteristic satisfying a predetermined parameter, performing one or more of the following;

transmitting wireless power to the receiver;

identifying whether the receiver is a receiver that is compatible with the inductively coupled power transfer system,

switching a transmitter of the system to a standby mode;

or

switching a transmitter of the system off.

12. An inductive power transmitter comprising:

a coil for generating an alternating magnetic field;

a converter for supplying an alternating current to the coil;

a sensor for measuring the current supplied to the converter; and

a controller configured to;

operate the converter at a plurality of frequencies within a frequency range;

determine a peak amplitude of the current measured using the sensor during an inrush period for each of the plurality of frequencies;

analyze a characteristic of the determined peak amplitudes within the frequency range; and

detect a receiver on the basis of the characteristic satisfying a predetermined parameter.

13. The inductive power transmitter as claimed in claim 12, wherein the controller is further configured to, before operating the converter at each of the plurality of frequencies, operate the converter to supply an alternating current, with a non-resonant frequency higher than the frequency range, to remove biases in capacitors present in an inductively coupled power transfer system.

14. The inductive power transmitter as claimed in claim 13, wherein the non-resonant frequency is between 1 and 10 MHz.

15. The inductive power transmitter as claimed in claim 12, wherein the controller is configured to, while determining a peak amplitude of the current during the inrush period for each of the plurality of frequencies, disregard peak amplitudes that are below a threshold.

16. The inductive power transmitter as claimed in claim 12, wherein the frequency range is 100 to 1,000 kHz.

17. The inductive power transmitter as claimed in claim 12, wherein analyzing a characteristic of the determined peak amplitudes within the frequency range comprises:

identifying a maximum;

determining properties of the identified maximum, including the width of the identified maximum, the magnitude of the peak of the identified maximum, or the frequency at which the maximum occurs.

18. The inductive power transmitter as claimed in claim 17, wherein the predetermined parameter is the frequency at which the identified maximum occurs.

19. The inductive power transmitter as claimed in claim 17, wherein the maximum has a width and the predetermined parameter comprises the width of the maximum.

20. The inductive power transmitter as claimed in claim 19, wherein detecting a receiver on the basis of the characteristic satisfying a predetermined parameter comprises detecting the receiver based on a determination of whether the width of the identified maximum spans more than 50 kHz.

21. The inductive power transmitter as claimed in claim 17, wherein the predetermined parameter comprises the magnitude of the peak of the identified maximum.

22. The inductive power transmitter as claimed in claim 12, wherein the controller is further configured to:

in accordance with the result of detecting the receiver on the basis of the characteristic satisfying a predetermined parameter, perform one or more of the following;

transmit wireless power to the receiver;

identify whether the receiver is a receiver that is compatible with the inductively coupled power transfer system;

switch the transmitter to a standby mode;

or

switch the transmitter off.