Output switching systems and methods for magnetic field sensors

Patent metadata

Field	Value
Publication number	US-9638548-B2
Application number	US-201213532152-A
Country	US
Kind code	B2
Filing date	Jun 25, 2012
Priority date	May 7, 2012
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

Embodiments relate to predictive output switching threshold determination systems and methods for sensors, for example magnetic field sensors. In embodiments, at least one individual switching threshold is determined predictively, rather than reactively, for each tooth or pole of a ferromagnetic tooth or pole wheel, respectively. For example, in one embodiment, the number of teeth or poles is programmed, and an optimal threshold for each tooth or pole is determined during a rotation of the wheel. The determined optimal threshold for each tooth is then used for that tooth in at least one subsequent rotation of the wheel, with calibration optionally taking place in future subsequent rotations. Thus, in embodiments, thresholds are predictive for each individual tooth or pole rather than reactive to an adjacent tooth or pole.

First claim

What is claimed is:

1. A sensor system comprising:
a target wheel comprising a plurality of target elements; and
a sensor comprising a magnetic field sensor element coupled to sensor circuitry, the magnetic field sensor element configured to sense rotation of the target wheel based on a varying magnetic field and provide a corresponding output signal comprising a maximum and a minimum for each of the plurality of target elements indicating any differences between the plurality of target elements, the sensor circuitry configured to, for each one of the plurality of target elements, use at least one maximum and at least one minimum related to the one of the plurality of target elements to predict an individual switching threshold for a subsequent instance of that one of the plurality of target elements,
wherein the sensor circuitry is configured to use the maximum for the one of the plurality of target elements and a value determined from the minima for the plurality of target elements in at least one rotation to predict the individual switching threshold for at least the next instance of that one of the plurality of target elements.

2. The sensor system of claim 1 , wherein the target wheel comprises one of a pole wheel or a tooth wheel and the target elements comprise one of poles or teeth, respectively.

3. The sensor system of claim 1 , wherein the magnetic field sensor element comprises a Hall element.

4. The sensor system of claim 1 , further comprising a back bias magnet.

5. The sensor system of claim 1 , wherein the sensor circuitry is configured to, for each one of the plurality of target elements, predict a rising edge individual threshold and a falling edge individual threshold for a subsequent instance of that one of the plurality of target dements.

6. The sensor system of claim 1 , wherein the sensor circuitry is further configured to, for each one of the plurality of target elements, use the maximum for the one of the plurality of target elements, a minimum immediately preceding the maximum and a minimum immediately following the maximum to predict the individual switching threshold for at least the next instance of that one of the plurality of target elements.

7. The sensor system of claim 1 , wherein the sensor circuitry is further configured to, for each one of the plurality of target elements, use the minimum for the one of the plurality of target elements and an average of the maxima for the plurality of target elements in one rotation to predict the individual switching threshold for at least the next instance of that one of the plurality of target elements.

8. The sensor system of claim 1 , wherein the sensor circuitry is further configured to, for each one of the plurality of target elements, use the minimum for the one of the plurality of target elements, a maximum immediately preceding the minimum and a maximum immediately following the minimum to predict the individual switching threshold for at least the next instance of that one of the plurality of target elements.

9. The sensor system of claim 1 , wherein the sensor circuitry is further configured to determine a safety zone for each individual threshold, the safety zone defining a point at which the sensor circuitry can transition from comparing the output signal with a current individual threshold to comparing the output signal with a subsequent individual threshold.

10. The sensor system of claim 9 , wherein the safety zone comprises a hysteresis compensation component.

11. The sensor system of claim 10 , wherein the hysteresis compensation component is preprogrammed.

12. The sensor system of claim 10 , wherein the hysteresis compensation component is determined by the sensor circuitry from a signal amplitude.

13. The sensor system of claim 1 , wherein the sensor circuitry comprises analog signal processing circuitry, a comparator, a digital-to-analog converter and an analog-to-digital converter.

14. The sensor system of claim 13 , wherein the comparator is configured to compare the output signal from the magnetic field sensor element with an individual switching threshold.

15. The sensor system of claim 1 , wherein the sensor circuitry comprises, for each one of the plurality of target elements, a plurality of shift registers, a first subset of the plurality of shift registers each configured to store a maximum for one of the target elements, and a second subset of the plurality of shift registers each configured to store a minimum for one of the target elements, the plurality of shift registers configured to buffer the maxima and minima until a next instance of the target element associated with a particular set of a maximum and a minimum.

16. The sensor system of claim 1 , wherein the sensor circuitry is configured to detect a total number of the plurality of target elements.

17. The sensor system of claim 1 , wherein the sensor circuitry is preprogrammed with a total number of the plurality of target elements.

18. A method comprising:
detecting, by a magnetic field sensor element, a maximum and a minimum for each target element, indicating any differences between each target element, during a first rotation of a target wheel;
using, for each of the plurality of target elements, at least one maximum and at least one minimum related to the particular target element to predict an individual switching threshold for the particular target element in at least one subsequent rotation of the target wheel; and
using the maximum for the one of the plurality of target elements and a value determined from the minima for the plurality of target elements in at least one rotation to predict the individual switching threshold for at least the next instance of that one of the plurality of target elements.

19. The method of claim 18 , comprising calibrating the individual switching threshold by repeating the detecting and using in each rotation of the target wheel.

20. The method of claim 18 , further comprising using comprises using a maximum for the particular target element, a minimum immediately preceding the maximum and minimum immediately following the maximum to predict the individual switching threshold for at least the next instance of the particular target element.

21. The method of claim 18 , further comprising using comprises using a minimum for the particular target element, a maximum immediately preceding the minimum and a maximum immediately following the minimum to predict the individual switching threshold for at least the next instance of the particular target element.

22. The method of claim 18 , further comprising using comprises using a maximum for the particular target element and an average of the minima from at least one of the first rotation, a preceding rotation or a current rotation to predict the individual switching threshold for at least the next instance of the particular target element.

23. The method of claim 18 , further comprising using comprises using a minimum for the particular target element and an average of the maxima from at least one of the first rotation, a preceding rotation or a current rotation to predict the individual switching threshold for at least the next instance of the particular target element.

24. The method of claim 18 , further comprising determining a safety zone for the individual switching threshold, the safety zone defining a point to switch from an individual switching threshold for a first target element to an individual s

Assignees

• Mialtu Razvan-Catalin
• Stoica Dan-Ioan-Dumitru
• Untersteiner Heinz
• Juglan Catalina-Petruta
• Infineon Technologies Ag

Inventors

• Mialtu Razvan-Catalin
• Stoica Dan-Ioan-Dumitru
• Untersteiner Heinz
• Juglan Catalina-Petruta

Classifications

• G01D5/147 Primary

  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 title