Device and current sensor for providing information indicating a safe operation of the device of the current sensor

Patent metadata

Field	Value
Publication number	US-9507005-B2
Application number	US-201414197702-A
Country	US
Kind code	B2
Filing date	Mar 5, 2014
Priority date	Mar 5, 2014
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

An example of a device comprises a signal generator to generate a signal causing a magnetic self test field for a magneto-resistive sensing element. A signal input is configures to receive a first sensor signal at a first time instant before the magnetic self test field is applied and a second sensor signal at a second time instant after the magnetic self test field is applied. An evaluation circuit is configured to determine information indicating a safe operation based on an evaluation of the first sensor signal and the second sensor signal.

First claim

What is claimed is:

1. A device, comprising:
a signal generator to generate a signal causing a magnetic self test field for a magneto-resistive sensing element;
a signal input to receive a first sensor signal of the magneto-resistive sensing element at a first time instant before the magnetic self test field is applied and a second sensor signal of the magneto-resistive sensing element at a second time instant after the magnetic self test field is applied; and
an evaluation circuit to determine information indicating a safe operation based on an evaluation of the first sensor signal and the second sensor signal,
wherein the evaluation is configured to determine that the magneto-resistive sensing element is in a safe operation state if a difference between the first sensor signal and the second sensor signal corresponds to an expected response of the magneto-resistive sensing element to the magnetic self test field.

2. The device of claim 1 , wherein the signal is configured to cause a current through a compensation coil of the magneto-resistive sensing element.

3. The device of claim 1 , wherein the signal is configured to cause a current through a flipping coil of an anisotropic magneto-resistive sensing element.

4. The device of claim 3 , wherein the signal is configured to cause a current through the flipping coil which is smaller than a further current used to flip a direction of a magnetization of the anisotropic magneto-resistive sensing element.

5. The device of claim 3 , wherein the signal is configured to cause a flipping current through the flipping coil which generates a magnetic flipping field causing a flipping of a direction of a magnetization of the anisotropic magneto-resistive sensing element.

6. The device of claim 1 , wherein the signal generator is further configured to cause a further magnetic self test field after the second time instant.

7. A current sensor comprising:
at least one magneto-resistive sensing element to provide a sensor signal in response to a magnetic field;
a signal generator to cause a magnetic self test field at the magneto-resistive sensing element;
a readout circuit to receive a first sensor signal of the magneto-resistive sensing element at a first time instant before the magnetic self test field is applied and a second sensor signal of the magneto-resistive sensing element at a second time instant after the magnetic self test field is applied; and
an evaluation circuit to determine information indicating a safe operation of the current sensor based on an evaluation of the first sensor signal and the second sensor signal;
wherein the evaluation circuit is configured to determine that the magneto-resistive sensing element is in a safe operation state if a difference between the first sensor signal and the second sensor signal corresponds to an expected response of the magneto-resistive sensing element to the magnetic self test field.

8. The current sensor of claim 7 , further comprising:
at least one compensation coil to compensate an external magnetic field at the magneto-resistive sensing element at least partly if a current flows through the compensation coil, wherein the signal generator is configured to cause a current through the compensation coil.

9. The current sensor of claim 7 , comprising four magneto-resistive sensing elements, the magneto-resistive sensing elements being coupled as a Wheatstone bridge.

10. The current sensor of claim 7 , wherein the magneto-resistive sensing element is an anisotropic magneto-resistive sensing element.

11. The current sensor of claim 10 , further comprising:
at least one flipping coil to flip a direction of a magnetization of the anisotropic magneto-resistive sensing element.

12. The current sensor of claim 11 , wherein the signal generator is configured to cause a flipping current through the flipping coil, the flipping current generating a magnetic flipping field used to flip the magnetization of the anisotropic magneto-resistive sensing element.

13. The current sensor of claim 12 wherein the signal generator generates a current through the flipping coil which is smaller than the flipping current.

14. The current sensor of claim 12 , wherein the evaluation circuit is configured to determine that the magneto-resistive sensing element is in a safe operation state if a difference between the first sensor signal and the second sensor signal corresponds to an expected offset of the magneto-resistive sensing element.

Assignees

• Infineon Technologies Ag

Inventors

• Jost Franz
• Castro Serrato Carlos

Classifications

• G01R35/005 Primary

  Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence) · CPC title

• G01R33/091

  Constructional adaptation of the sensor to specific applications · CPC title

• G01R19/0092

  Measuring current only · CPC title

• G01R35/00

  Testing or calibrating of apparatus covered by the other groups of this subclass · CPC title

• G01R15/205

  using magneto-resistance devices, e.g. field plates · CPC title