Magnetic field sensors having virtual signals

• US 10,578,679 B2
• Filed: 06/18/2018
• Issued: 03/03/2020
• Est. Priority Date: 06/18/2018
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Sitorus, Timothy, Shoemaker, Eric G.
• Primary Examiner(s): Astacio-Oquendo, Giovanni
• Application Number:
  US16/010,969
• Publication Number:
  US 20190383885A1
• Time in Patent Office: 624 Days
• Field of Search: 324 97, 32475023, 32475027, 32475421-75431
• CPC Class Codes: G01D 5/24404 Interpolation using high frequency signals
• CPC Class Codes: G01D 5/245 using a variable number of pulses in a train
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01R 33/0023 Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration G01R33/0017 takes precedence
• CPC Class Codes: G01R 33/0094 Sensor arrays
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: G01R 33/072 Constructional adaptation of the sensor to specific applications
• CPC Class Codes: G01R 33/09 Magnetoresistive devices
• CPC Class Codes: G01R 33/091 Constructional adaptation of the sensor to specific applications

Abstract

A magnetic field sensor includes a plurality of magnetic field sensing elements configured to generate at least two measured magnetic field signals indicative of a magnetic field affected by an object and having a first predetermined phase difference with respect to each other and a controller responsive to the at least two measured magnetic field signals. The controller is configured to generate at least one virtual magnetic field signal having a second predetermined phase difference with respect to at least one of the measured magnetic field signals. In embodiments, the virtual magnetic field signal has the second predetermined phase difference with respect to each of the at least two measured magnetic field signals.

Claims

1. A magnetic field sensor, comprising:

a plurality of magnetic field sensing elements configured to generate at least two measured magnetic field signals indicative of a magnetic field affected by an object and having a first predetermined phase difference with respect to each other; and

a controller responsive to the at least two measured magnetic field signals and configured to generate at least one virtual magnetic field signal having a second predetermined phase difference with respect to at least one of the measured magnetic field signals.

2. The magnetic field sensor of claim 1, wherein the at least one virtual magnetic field signal has the second predetermined phase difference with respect to each of the at least two measured magnetic field signals.

3. The magnetic field sensor of claim 1, wherein the controller is configured to generate the at least one virtual magnetic field signal according to a mathematical function that characterizes a relationship between the second predetermined phase difference and each of the at least two measured magnetic field signals.

4. The magnetic field sensor of claim 3, wherein the mathematical function is used to generate the at least one virtual magnetic field signal based on a cosine of the second predetermined phase difference and a sine of the second predetermined phase difference.

5. The magnetic field sensor of claim 4, wherein the controller comprises a look-up table containing cosine values of the second predetermined phase difference and sine values of the second predetermined phase difference.

6. The magnetic field sensor of claim 1, wherein the first predetermined phase difference between the at least two measured magnetic field signals is approximately ninety degrees.

7. The magnetic field sensor of claim 1, wherein the controller is responsive to the at least two measured magnetic field signals to generate a plurality of virtual magnetic field signals, each having a respective, different predetermined phase difference with respect to each of the at least two measured magnetic field signals.

8. The magnetic field sensor of claim 1, wherein the controller is programmable to select the second predetermined phase difference of the at least one virtual magnetic field signal.

9. The magnetic field sensor of claim 1, wherein the controller is configured to compare each of the at least two measured magnetic field signals to a threshold to generate respective channel output signals and is further configured to compare the at least one virtual magnetic field signal to the threshold to generate a virtual channel output signal.

10. The magnetic field sensor of claim 1, wherein the plurality of magnetic field sensing elements comprises one or more Hall effect elements and/or magnetoresistance elements.

11. The magnetic field sensor of claim 1, wherein the plurality of magnetic field sensing elements comprises at least one first element having an axis of maximum sensitivity in a first plane and at least one second element having an axis of sensitivity in a second plane orthogonal to the first plane.

12. The magnetic field sensor of claim 1, further comprising a back bias magnet to generate the magnetic field and wherein the object comprises a ferromagnetic object.

13. A method comprising:

generating at least two measured magnetic field signals indicative of a magnetic field affected by an object, wherein the at least two measured magnetic field signals have a first predetermined phase difference with respect to each other; and

processing the at least two measured magnetic field signals to generate at least one virtual magnetic field signal having a second predetermined phase difference with respect to at least one of the measured magnetic field signals.

14. The method of claim 13, wherein processing the at least two measured magnetic field signals comprises generating the at least one virtual magnetic field signal having the second predetermined phase difference with respect to each of the at least two measured magnetic field signals.

15. The method of claim 13, wherein processing the at least two measured magnetic field signals comprises computing values of the at least one virtual magnetic field signal according to a mathematical function that characterizes a relationship between the second predetermined phase difference and each of the at least two measured magnetic field signals.

16. The method of claim 13, wherein computing values of the at least one virtual magnetic field signal according to the mathematical function comprises computing a cosine of the second predetermined phase difference and a sine of the second predetermined phase difference.

17. The method of claim 13, wherein processing the at least two measured magnetic field signals comprises processing the at least two measured magnetic field signals to generate a plurality of virtual magnetic field signals, each having a respective, different predetermined phase difference with respect to each of the at least two measured magnetic field signals.

18. The method of claim 13, wherein processing the at least two measured magnetic field signals comprises responding to a programmable selection of the second predetermined phase difference.

19. The method of claim 13, further comprising generating at least two channel output signals by comparing the at least two measured magnetic field signals to a threshold and generating a virtual channel output signal by comparing the at least one virtual magnetic field signal to the threshold.

20. The method of claim 13, wherein generating at least two measured magnetic field signals comprises using one or more Hall effect elements and/or magnetoresistance elements.

21. The method of claim 20, wherein generating at least two measured magnetic field signals comprises using differential signals from three spaced Hall effect elements.

22. The method of claim 20, wherein generating at least two measured magnetic field signals comprises using at least one first element having an axis of maximum sensitivity in a first plane and at least one second element having an axis of sensitivity in a second plane orthogonal to the first plane.

23. Apparatus comprising:

means for generating at least two measured magnetic field signals indicative of a magnetic field affected by an object and having a first predetermined phase difference with respect to each other; and

means for generating at least one virtual magnetic field signal based on the at least two measured magnetic field signals, the at least one virtual magnetic field signal having a second predetermined phase difference with respect to at least one of the measured magnetic field signals.