MAGNETIC FIELD SENSOR WITH SWITCHING NETWORK

• US 20190312579A1
• Filed: 04/06/2018
• Published: 10/10/2019
• Est. Priority Date: 04/06/2018
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Romero, Hernan D.
• Granted Patent: US 10,917,092 B2
• Time in Patent Office: Days
• CPC Class Codes: G01D 5/142 using Hall-effect devices measuring magnetic variables using Hall-effect or other galvanomagnetic devices G01R33/06
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01R 33/0017 Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields
• 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 33/0088 use of bistable or switching devices, e.g. Reed-switches
• CPC Class Codes: G01R 33/0094 Sensor arrays
• CPC Class Codes: G01R 33/077 Vertical Hall-effect devices
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: H03K 17/97 using a magnetic movable element

Abstract

A magnetic field sensor comprises a substrate, a first coil supported by the substrate and configured to carry a first current in a first direction to generate a first magnetic field, and a second coil supported by the substrate and nested within the first coil to form a gap between the first and second coils, the second coil configured to carry a second current in a second, opposite direction to generate a second magnetic field. A plurality of magnetic field sensing elements is configured to detect the first and second magnetic fields. A switching network is coupled to the plurality of magnetic field sensing elements and configured to connect the plurality of magnetic field sensing elements to form a first bridge circuit having a first arrangement of the magnetic field sensing elements and a second bridge circuit having a second arrangement of the magnetic field sensing elements.

Claims

1. A magnetic field sensor comprising:

a substrate;

a first coil supported by the substrate and configured to carry a first current in a first direction to generate a first magnetic field;

a second coil, supported by the substrate and nested within the first coil to form a gap between the first and second coils, the second coil configured to carry a second current in a second, opposite direction to generate a second magnetic field;

a plurality of magnetic field sensing elements configured to detect the first and second magnetic fields; and

a switching network coupled to the plurality of magnetic field sensing elements and configured to connect the plurality of magnetic field sensing elements to form a first bridge circuit having a first arrangement of the magnetic field sensing elements and a second bridge circuit having a second arrangement of the magnetic field sensing elements.

2. The magnetic field sensor of claim 1 wherein:

the plurality of magnetic field sensing elements comprises four magnetic field sensing elements;

the first bridge circuit comprises the four magnetic field sensing elements coupled in the first arrangement; and

the second bridge circuit comprises the four magnetic field sensing elements coupled in the second arrangement.

3. The magnetic field sensor of claim 1 wherein the switching network is configured to form the first bridge circuit during a first time period and form the second bridge circuit during a non-overlapping second time period.

4. The magnetic field sensor of claim 1 wherein:

the plurality of magnetic field sensing elements comprises eight magnetic field sensing elements;

the switching network is configured to form the first bridge circuit and the second bridge circuit simultaneously; and

the switching network is configured to decouple one or more first magnetic field sensing elements from the first bridge circuit and couple the one or more first magnetic field sensing elements to the second bridge circuit.

5. The magnetic field sensor of claim 4 wherein the switching network is further configured to decouple one or more second magnetic field sensing elements from the second bridge circuit and couple the one or more second magnetic field sensing elements to the first bridge circuit.

6. The magnetic field sensor of claim 4 wherein four of the eight magnetic field sensing elements are positioned on one side of the first and second coils, and another four of the eight magnetic field sensing elements are positioned on an opposite side of the first and second coils.

7. The magnetic field sensor of claim 6 wherein the first and second coils are configured to induce a reflected field from a conductive target.

8. The magnetic field sensor of claim 7 wherein the switching network is configured to form the first bridge circuit and the second bridge circuit so that they are sensitive to differentially sense the reflected field and insensitive to sense the first and second magnetic field.

9. The magnetic field sensor of claim 7 wherein the switching network is configured to form the first bridge circuit and the second bridge circuit so that they are insensitive to sense the reflected field and sensitive to sense the first and second magnetic fields.

10. The magnetic field sensor of claim 1 wherein the switching network is configured to form the first bridge circuit in parallel with the second bridge circuit.

11. The magnetic field sensor of claim 10 wherein the switching network comprises an averaging circuit to average a differential output of the first bridge circuit and a differential output of the second bridge circuit to provide an averaged output signal.

12. The magnetic field sensor of claim 1 further comprising a first signal processing path to process an output signal of the first bridge circuit and a second signal processing path to process an output of the second bridge circuit.

13. The magnetic field sensor of claim 1 wherein the plurality of magnetic field sensing elements comprises one or more of:

a Hall effect element, a magnetoresistance element, a giant-magnetoresistance element, and a tunneling magnetoresistance element.

14. The magnetic field sensor of claim 1 wherein the second coil is a counter-coil of the first coil.

15. A magnetic field sensor comprising:

a first coil configured to carry a first current in a first direction to generate a first magnetic field;

a second coil configured to carry a second current in a second, opposite direction to generate a second magnetic field;

a plurality of magnetic field sensing elements configured to detect the first and second magnetic fields; and

a switching network coupled to the plurality of magnetic field sensing elements and configured to connect the plurality of magnetic field sensing elements to form a bridge circuit.

16. The magnetic field sensor of claim 15 wherein:

first magnetic field sensing elements of the plurality of magnetic field sensing elements are positioned on one side of the first and second coils and second magnetic field sensing elements of the plurality of magnetic field sensing elements are positioned on an opposite side of the coil; and

the bridge circuit comprises one or more of the first magnetic field sensing elements and one or more of the second magnetic field sensing elements.

17. The magnetic field sensor of claim 15 wherein the first magnetic field induces a reflected magnetic field in a conductive target and the bridge circuit is configured to detect the reflected field and produce an output signal representing the reflected field, wherein a differential portion of the output signal is responsive to the reflected field.

18. The magnetic field sensor of claim 15 wherein the bridge circuit is configured to produce an output signal representing the second magnetic field, wherein a common mode portion of the output signal is responsive to the second magnetic field.

19. The magnetic field sensor of claim 15 further comprising a signal processing path to process an output signal of the bridge circuit.

20. The magnetic field sensor of claim 15 wherein the plurality of magnetic field sensing elements comprises one or more of:

a Hall effect element, a magnetoresistance element, a giant-magnetoresistance element, and a tunneling magnetoresistance element.

21. A magnetic field sensor comprising:

a first coil configured to carry a first current in a first direction to generate a first magnetic field, wherein the first magnetic field induces a reflected field in a conductive target;

a second coil configured to carry a second current in a second, opposite direction to generate a second magnetic field;

a plurality of magnetic field sensing elements configured to detect the first and second magnetic fields; and

means for connecting one or more of the plurality of magnetic field sensing elements to form a bridge circuit.

22. The magnetic field sensor of claim 21 wherein the bridge circuit generates a differential output signal responsive to the reflected field and not responsive to the first and second magnetic fields.

23. The magnetic field sensor of claim 21 wherein the bridge circuit generates a differential output signal that is responsive to the first and second magnetic fields and not responsive to the reflected field.