Method and system for determining the orientation of magnetic fields by means of gmr sensors

• US 20040012389A1
• Filed: 01/06/2003
• Published: 01/22/2004
• Est. Priority Date: 07/05/2000
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Maiwald, Hubert
• Granted Patent: US 6,882,146 B2
• Time in Patent Office: Days
• US Class Current: 324/252
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00

Abstract

The invention relates to a method and a system for determining the orientation of an external magnetic field by means of GMR sensors. The inventive method enables signals from the GRM sensors to be reprocessed easily in order to compensate the temperature dependence of the signals.

Claims

1. Method for determining the orientation of an external magnetic field with GMR sensors, comprising the following steps:

a) a sensor circuit having at least a first and a second sensor sub-circuit that are connected parallel to one another is offered, whereby the first and the second sensor sub-circuit each respectively comprise at least a first and a second GMR sensor that are connected in series and that are respectively arranged in opposite internal magnetic orientation, whereby the internal magnetic orientation of the GMR sensors of the first sensor sub-circuit is essentially perpendicular to the internal magnetic orientation of the GMR sensors of the second sensor sub-circuit;

b) respectively three sensor voltages V(P1), V(P2), V(P3) are taken at the points P1, P2 and P3 in the first and the second sensor sub-circuit, whereby P1 lies on the connecting line from the current sink to the second GMR sensor, P2 lies on the connecting line from the second GMR sensor to the first GMR sensor and P3 lies on the connecting line from the first GMR sensor to the current supply;

c) a first difference circuit generates a difference voltage V1 from the three sensor voltages of the first sensor sub-circuit, and a second difference circuit generates a difference voltage V2 from the three sensor voltages of the second sensor sub-circuit;

d) a scaling factor is calculated with the assistance of V1 and V2;

e) V1 and V2 are scaled such with the scaling factor that the orientation of the external magnetic field can be determined from them.

2. Method according to claim 1, characterized in that the current through the first sensor sub-circuit and the current through the second sensor sub-circuit are essentially the same.

3. Method according to one of the preceding claims, characterized in that the first difference circuit and the second difference circuit are identical.

4. Method according to one of the preceding claims, characterized in that the scaling factor is the root of the square sums of V1 and V2 or an approximation thereto.

5. Method according to one of the preceding claims, characterized in that the calculation of the squares of V1 and/or V2 is implemented with an analog circuit.

6. Method according to one of the preceding claims, characterized in that the calculation of the square sum of V1 and V2 is implemented with an analog circuit.

7. Method according to one of the preceding claims, characterized in that the calculation of the root of the square sum of V1 and V2 is approximated with an analog circuit.

8. Method according to one of the preceding claims, characterized in that the scaling of the V1 and/or V2 values ensues by division of the V1 and V2 values by the scaling factor.

9. Method according to one of the preceding claims, characterized in that the scale V1 and/or V2 values have orientation angles of the external magnetic field allocated to them.

10. System with GMR sensors for determining the orientation of an external magnetic field, characterized in that

the system comprises a sensor circuit having a first and a second sensor sub-circuit, whereby the first sensor sub-circuit is connected parallel to the second sensor sub-circuit and the first and the second sensor sub-circuit each respectively comprise at least a first and a second GMR sensor that are connected in series and that are respectively arranged in opposite internal magnetic orientation relative to one another, whereby the internal magnetic orientation of the GMR sensors of the first sensor sub-circuit is essentially perpendicular to the internal magnetic orientation of the GMR sensors of the second sensor sub-circuit;

the first and the second sensor sub-circuit respectively comprise three measuring points P1, P2 and P3, whereby P1 lies on the connecting line from the current sink to the second GMR sensor, P2 lies on the connecting line from the second GMR sensor to the first GMR sensor and P3 lies on the connecting line from the first GMR sensor to the current supply, so that the three sensor voltages V(P1), V(P2), V(P3) can be taken at the measuring points P1, P2 and P3;

the system comprises a first and a second difference circuit, whereby the first difference circuit generates a difference voltage V1 from the three sensor voltages of the first sensor sub-circuit, and a second difference circuit generates a difference voltage V2 from the three sensor voltages of the second sensor sub-circuit;

the system comprises a scaling circuit that reads out the difference voltage V1 and the difference voltage V2 and scales them such that the orientation of the external magnetic field can be determined from the scaled values.

11. System according to claim 11 [sic], characterized in that the current through the first sensor sub-circuit and the current through the second sensor sub-circuit are essentially the same.

12. System according to claim 11 through 12 [sic], characterized in that the first and the second differential circuit are essentially identical.

13. System g [sic] according to claim 11 through 13 [sic], characterized in that the scaling circuit comprises a circuit for calculating the scaling factor.

15. System according to claim 11 through 15 [sic], characterized in that the scaling circuit comprises a circuit for scaling the V1 and V2 values.

17. System according to claim 11 through 17 [sic], characterized in that the electronic circuit comprises an algorithm and/or data that allocates an angle for the determination of the orientation of the external magnetic field to the scaled V1 and/or V2 values.

18. System according to claim 11 through 18 [sic], characterized in that the scaling circuit comprises a circuit that implements the allocation of a scaled V1, V2 value pair to an orientation angle of the external magnetic field.

19. System according to claim 11 through 19 [sic], characterized in that at least one of the circuits of the scaling circuit is integrated in an ASIC.

20. System according to claim 11 through 20 [sic], characterized in that the voltages V1 and/or V2 are electronically amplified before. [sic]

14. System according to claim 14 [sic], characterized in that the circuit for calculating the scaling factor comprises a circuit for calculating the root of the square sum of the V1 and V2 values or an approximation thereof.

16. System according to claim 16 [sic], characterized in that the circuit for scaling the V1 and V2 values comprises a circuit that divides the V1 and V2 values by the scaling factor.