METHOD OF AND APPARATUS FOR DETECTING COIL ALIGNMENT ERROR IN WIRELESS INDUCTIVE POWER TRANSMISSION

• US 20160181875A1
• Filed: 08/06/2014
• Published: 06/23/2016
• Est. Priority Date: 08/06/2013
• Status: Active Grant

• Current Assignee: InductEV Inc.
• Original Assignee: Momentum Dynamics Corporation
• Inventors: LONG, Bruce Richard, DAGA, Andrew William
• Granted Patent: US 10,193,400 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment

Abstract

A method for detecting induction coil alignment error in resonant induction wireless power apparatus includes an eddy current coil array superimposed upon the primary induction coil, a switching device for each eddy current coil, a voltage detector such as a low power rectifier connected to the secondary induction coil, an analog-to-digital converter, primary and secondary side micro-controllers, and, in a vehicle charging embodiment, a vehicle operator interface. During coil alignment, the primary side induction coil operates at low power. Eddy current flows in an eddy current coil only if the associated switching device is switched on.

Claims

1. An apparatus for detecting coil alignment error in a wireless resonant inductive power transmission system comprising a primary inductive coil and a secondary inductive coil arranged to constitute a loosely coupled air core transformer whereby power in the primary inductive coil is transferred to the secondary inductive coil when the primary inductive coil is activated, comprising:

at least two arc segment eddy current coils superimposed on the primary inductive coil, said at least two arc segment eddy current coils arranged to correspond with respective sectors of the primary inductive coil whereby an active eddy current coil has the effect of reducing a magnetic flux intercepted by the secondary inductive coil;

a switch connected to each arc segment eddy current coil;

a sequencer arranged to selectively activate said switches singularly or in unison in a switching sequence; and

a voltage detector that detects voltage variations in the secondary inductive coil during said switching sequence, whereby alignment of said primary inductive coil and said secondary inductive coil is detected by activating the eddy current coils sequentially and measuring detected voltage variations of the secondary inductive coil during the eddy current coil switching sequence, and whereby correspondence between the eddy current coil switching sequence and a largest magnetic flux variation of said secondary inductive coil indicates an error vector direction and a magnitude of magnetic flux variations of the secondary inductive coil indicate an error vector magnitude.

2. The apparatus of claim 1, further comprising a bridge rectifier connected to each arc segment eddy current coil to control an alternating current present in an arc segment eddy current coil that is sequentially activated according to said switching sequence.

3. The apparatus of claim 1, wherein each of said switches comprises a unidirectional, alternating current semiconductor switch comprising two field effect transistors connected source-to-source and gate-to-gate.

4. The apparatus of claim 1, further comprising a wireless data link between said sequencer and said voltage detector, said data link communicating an indication of which eddy current coil is active at all times during an alignment error detection process from said sequencer to said voltage detector.

5. The apparatus of claim 1, wherein said voltage detector comprises a low power rectifier and an analog-to-digital converter that converts an output of said low power rectifier to digital data that is processed by a microcontroller to detect said correspondence between the eddy current coil switching sequence and a largest magnetic flux variation of said secondary inductive coil and a magnitude of said magnetic flux variations of the secondary inductive coil.

6. The apparatus of claim 5, further comprising a user interface connected to said microcontroller for display of said error vector direction and said error vector magnitude to a user of said apparatus for use in adjustment of alignment of said primary inductive coil and said secondary inductive coil using said error vector direction and said error vector magnitude.

7. The apparatus of claim 6, wherein said primary inductive coil is interfaced to a charger, said secondary inductive coil is interfaced to a vehicle, and said user interface provides said error vector direction and said error vector magnitude to an operator of said vehicle.

8. The apparatus of claim 1, wherein the sequencer drives each arc segment eddy current coil simultaneously at different clock frequencies.

9. The apparatus of claim 8, wherein said sequencer drives each arc segment eddy current coil with a square wave, a rectangular wave, or a sinusoidal waveform at different clock frequencies.

10. The apparatus of claim 8, wherein said voltage detector comprises a low power rectifier and an analog-to-digital converter that converts an output of said low power rectifier to digital data that is processed by a microcontroller to detect said correspondence between the eddy current coil switching sequence and a largest magnetic flux variation of said secondary inductive coil and a magnitude of said magnetic flux variations of the secondary inductive coil.

11. The apparatus of claim 10, wherein said microcontroller processes a digital data time series output by said analog-to-digital converter by performing a time domain to frequency domain conversion of the digital data time series and selecting time domain to frequency domain conversion parameters such that each clock tone of said sequencer falls uniquely into a single frequency domain slot, whereby said microcontroller determines relative contribution of said arc segment eddy current coils from clock tone amplitudes and clock tone amplitude ratios so as to determine a magnitude and direction of in said single frequency domain slots corresponding to each of said each arc segment eddy current coils.

12. The apparatus of claim 1, further comprising four overlapping “

D”

shaped eddy current coils, each covering a 180 degree arc width segment of said primary inductive coil, wherein two of said “

D”

shaped eddy current coils provide front-back error determination and another two of said “

D”

shaped eddy current coils provide left-right error determination.

13. The apparatus of claim 1, further comprising three non-overlapping eddy current coils, each of said non-overlapping eddy current coils covering a 120 degree arc width segment of said primary inductive coil.

14. The apparatus of claim 1, wherein said primary inductive coil is part of a portable consumer electronic device charger and said secondary inductive coil is part of a portable consumer electronic device.

15. The apparatus of claim 14, further comprising notifying means for notifying a user when the portable consumer electronic device is properly aligned with the portable consumer electronic device charger during a charging operation.

16. A method of detecting of coil alignment error in a wireless resonant inductive power transmission system comprising a primary inductive coil and a secondary inductive coil arranged to constitute a loosely coupled air core transformer whereby power in the primary inductive coil is transferred to the secondary inductive coil when the primary inductive coil is activated, comprising the steps of:

arranging at least two arc segment eddy current coils so as to be superimposed on the primary inductive coil and to correspond with respective sectors of the primary inductive coil;

selectively activating said arc segment eddy current coils singularly or in unison in a switching sequence, whereby an active eddy current coil has the effect of reducing a magnetic flux intercepted by the secondary inductive coil;

detecting variations of a detected voltage of the secondary inductive coil during said switching sequence; and

detecting alignment of said primary inductive coil and said secondary inductive coil by activating the eddy current coils sequentially and measuring detected voltage variations of the secondary inductive coil during the eddy current coil switching sequence, whereby correspondence between the eddy current coil switching sequence and a largest magnetic flux variation of said secondary inductive coil indicates an error vector direction and a magnitude of magnetic flux variations of the secondary inductive coil indicate an error vector magnitude.

17. The method of claim 16, wherein each arc segment eddy current coil is sequentially activated according to said switching sequence.

18. The method of claim 17, further comprising communicating an indication of which eddy current coil is active at all times during an alignment error detection process from a sequencer that generates said switching sequence to a processor that determines whether said primary inductive coil and said secondary inductive coil are aligned.

19. The method of claim 16, further comprising displaying said error vector direction said error vector magnitude to a user of said wireless resonant inductive power transmission system to enable the user to adjust alignment of said primary inductive coil and said secondary inductive coil using said error vector direction and said error vector magnitude.

20. The method of claim 16, wherein selectively activating said arc segment eddy current coils comprises activating each arc segment eddy current coil simultaneously at different clock frequencies.

21. The method of claim 20, wherein selectively activating said arc segment eddy current coils comprises activating each arc segment eddy current coil simultaneously with a square wave, a rectangular wave, or a sinusoidal waveform at different clock frequencies.

22. The method of claim 16, wherein detecting variations of a detected voltage of the secondary inductive coil during said switching sequence comprises converting an output of a voltage detector on a secondary side of said wireless resonant inductive power transmission system to digital data that is processed by a microcontroller to detect said correspondence between the eddy current coil switching sequence and a largest magnetic flux variation of said secondary inductive coil and a magnitude of said magnetic flux variations of the secondary inductive coil.

23. The method of claim 20, wherein measuring detected voltage variations of the secondary inductive coil during the eddy current coil switching sequence comprises said microcontroller processing a digital data time series of said digital data by performing a time domain to frequency domain conversion of the digital data time series and selecting time domain to frequency domain conversion parameters such that each clock tone of said switching sequence falls uniquely into a single frequency domain slot, and said microcontroller determining relative contribution of said arc segment eddy current coils from clock tone amplitudes and clock tone amplitude ratios so as to determine a magnitude and direction of in said single frequency domain slots corresponding to each of said each arc segment eddy current coils.

24. The method of claim 16, further comprising displaying said error vector direction and said error vector magnitude to a user of said wireless resonant inductive power transmission system for use in adjustment of alignment of said primary inductive coil and said secondary inductive coil using said error vector direction and said error vector magnitude.

25. The method of claim 24, wherein said primary inductive coil is interfaced to a charger and said secondary inductive coil is interfaced to a vehicle, further comprising providing said error vector direction and said error vector magnitude to an operator of said vehicle.

26. The method of claim 16, wherein said primary inductive coil is part of a portable consumer electronic device charger and said secondary inductive coil is part of a portable consumer electronic device, further comprising the step of notifying a user when the portable consumer electronic device is properly aligned with the portable consumer electronic device charger during a charging operation.