Abstract
The present invention teaches the use of a plurality of high magnetic permeability material flux-guides to improve the amount of phase shift between signals generated by distinct magnetic field sensors, allowing improved rotation sensing of a rotating magnet. The plurality of flux-guides is at least equal in number to the number of distinct magnetic field sensors. In a preferred implementation, Hall plates in an integrated circuit are used as magnetic field sensors.
Claims
1. A combination of an electronic circuit and a magnetic circuit for measuring movement between a magnet and an integrated circuit, wherein the combination comprises the integrated circuit with at least two on-chip magnetic field sensors, the magnet and at least one flux-guide(s) that guide magnetic flux between the magnet and at least one of the magnetic field sensors, wherein the magnet is positioned a distance away from said integrated circuit, and wherein use of the flux guide(s) increases a phase angle present between the magnetic field strength signals generated by each of said on-chip sensors.
2. The combination of claim 1, with said flux-guide(s) being at least equal in number to the number of on-chip magnetic field sensors with each flux-guide aligned with a respective one of said on-chip magnetic field sensors.
3. The combination of claim 1, wherein the movement measured is due to rotational movement of said magnet.
4. The combination of claim 1, wherein the movement measured is the result of spatial movement of the integrated circuit around said magnet.
5. The combination of claim 1, wherein the flux-guide(s) increase the magnetic field strength measured by the magnetic field sensors.
6. The combination of claim 1, where the magnetic field sensors are Hall plates.
7. The combination of claim 1, wherein said magnet is located in a base of a laptop computer and said integrated circuit is located in a lid of the laptop computer, and wherein said measured movement comprises rotation of said integrated circuit about said magnet, with said rotation used to discern a lid position between open and closed.
8. The combination of claim 1, wherein said magnet is located in a lid of a laptop computer and said integrated circuit is located in a base of the laptop computer, and wherein said measured movement comprises rotation of said magnet about said integrated circuit, with said rotation used to discern a lid position between open and closed.
9. The combination of claim 1, wherein said flux-guide(s) cause magnetic fields between the magnet and integrated circuit to transition from a first plane to a second plane, wherein the first plane is orthogonal to said second plane.
10. The combination of claim 1, wherein an additional flux-guide is located on the non-magnet side of said integrated circuit.
11. The combination of claim 1, wherein said flux-guide(s) partially or fully comprises magnetic material with high relative magnetic permeability deposited onto a printed circuit board to form tracks of magnetic material for guiding or routing magnetic flux between its origin and said magnetic field sensors.
12. The combination of claim 1, comprising at least three magnetic field sensors to determine the orientation of the magnet, wherein said magnet is movable in a spatial orbit or track around the sensors, wherein at least two sensors are selected and used per segment of said orbit or track and wherein flux-guides are used to guide magnetic flux between the magnet and the sensors.
13. A method for measuring movement between a magnet and an integrated circuit, wherein the integrated circuit comprises at least two on-chip magnetic field sensors and said magnet is positioned a distance away from the integrated circuit, and wherein the method comprises the steps of using at least one flux-guide(s) to guide magnetic flux between said magnet and at least one of said sensors in such a manner as to increase a phase angle present between magnetic field strength signals generated by each of said on-chip sensors, and of using the increase in phase angle(s) during movement measurement.
14. The method of claim 13, wherein the flux-guide(s) are at least equal in number to the number of on-chip magnetic field sensors, and comprising the additional step of aligning each flux-guide with a respective one of said on-chip magnetic field sensors.
15. The method of claim 13, wherein the movement measured is due to rotational movement of said magnet.
16. The method of claim 13, wherein the movement measured is the result of spatial movement of the integrated circuit around said magnet.
17. The method of claim 13, wherein the flux-guide(s) increase the magnetic field strength measured by the magnetic field sensors.
18. The method of claim 13, wherein said magnet is located in a base of a laptop computer and said integrated circuit is located in a lid of the laptop computer, and wherein the measured movement is due to rotation of said integrated circuit about said magnet, and wherein the method comprises the additional step of using the measured movement to discern a lid position between open and closed.
19. The method of claim 13, wherein said magnet is located in a lid of a laptop computer and said integrated circuit is located in a base of the laptop computer, and wherein the measured movement is due to rotation of said magnet about said integrated circuit, and wherein the method comprises the additional step of using the measured movement to discern a lid position between open and closed.
20. The method of claim 13, wherein each of said flux-guide(s) partially or fully comprises magnetic material with high relative magnetic permeability deposited onto a printed circuit board to form tracks of magnetic material for guiding or routing magnetic flux between its origin and said magnetic field sensors.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The invention is further described by way of example with reference to various embodiments depicted in the accompanying drawings and graphs:
[0034] FIG. 1 shows an IC (5) that comprises two Hall plates (6) on-chip and mounted on a printed circuit board (PCB) (4).
[0035] FIG. 2 shows a diametrically magnetized magnet with a hole in the middle position above an IC with two Hall plates, and the plane of rotation of the magnet corresponding to the line between the two Hall plates.
[0036] FIG. 3 shows an exemplary embodiment setup with two high magnetic permeability members (flux-guides) positioned above respective Hall plates.
[0037] FIGS. 4A to 4E show exemplary embodiments where a magnet is positioned above an IC with various shapes of flux-guides collecting magnetic fields at specific locations proximate to the magnet and guiding it to respective Hall plates.
[0038] FIG. 5 shows an exemplary embodiment where a diametrically magnetized rod is positioned above an IC with four Hall plates positioned on the IC.
[0039] FIG. 6 shows an exemplary construction of flux-guides positioned in relation to Hall plates on an IC that may help improve magnetic field strength and angular resolution for a diametrically magnetized rod positioned above an IC with four Hall plates positioned on the IC.
[0040] FIGS. 7A and 7B show the exemplary use of more than two flux-guides to allow a bigger magnet, better magnetic field strength at the Hall plates and to translate the magnetic fields through 90 degrees.
[0041] FIGS. 8A and 8B show the exemplary use of flux-guides in an embodiment where the rotation of a ball such as a track ball can be resolved under certain conditions.
[0042] FIGS. 9A and 9B show exemplary measurements for the same construction with and without flux-guides.
[0043] FIGS. 10A and 10B show an exemplary embodiment in a laptop computer base and lid.
[0044] FIGS. 11 A and 11B show an alternative exemplary embodiment in a laptop computer base and lid.
[0045] FIG. 12 shows an exemplary embodiment wherein flux-guides are used to guide flux to two Hall plates which are orthogonal to each other.
[0046] FIG. 13 shows the use of a third flux-guide on the non-magnet side of two Hall plates in an exemplary manner.
[0047] FIG. 14 shows an exemplary embodiment of a single flux-guide used with an integrated circuit containing a vertical and a horizontal magnetic field sensor.
DETAILED DESCRIPTION OF EMBODIMENTS
[0048] To further clarify the disclosure of the present invention, the following descriptions relating to the appended drawings are presented. These should not be construed as limiting to the claims of the invention and are merely used to support clarity of disclosure. A large number of other equivalent embodiments may be possible that still fall within the spirit and scope of the present invention, as may be recognised by one skilled in the relevant art.
[0049] In FIG. 1 a typical prior art IC 5 is shown on a printed circuit board (PCB) 4 and the IC comprises two Hall plates 6.1 and 6.2 with a specific distance separating the two Hall plates.
[0050] In FIG. 2 that is part of what is regarded as prior art and to be improved upon is the parts of FIG. 1 mounted below a magnet 1 with a North pole 2.2 and a South pole 2.1. As can clearly be seen, the further the IC 5 is from the magnet the smaller the difference is in the field measured by the two Hall plates 6 on the IC. The phase angle 12 is a good metric for this.
[0051] FIG. 3 shows an exemplary embodiment wherein two high magnetic permeability material members 7.1 and 7.2 are positioned respectively over the two Hall plates 6.1 and 6.2 to form flux-guides. In FIG. 4A the desired angle between the flux-guide members 7.1 and 7.2 is determined by the distance from the IC 5 to the magnet (FIG. 4 member 1), the diameter of the magnet and the desired phase difference to be measured between the two Hall plates.
[0052] The length and shape of the flux-guides can be adjusted according to the application and implementation. The length and/or shape may have an effect on the measurements. For example, if the extra length (members 8.1 and 8.2 in FIG. 3) is added to the parts 7.1 and 7.2, the signal strength and the phase angle may be affected. FIGS. 4A to 4D illustrates examples of different shapes of flux collector areas that each may have different advantages and disadvantages.
[0053] In FIG. 4E exemplary circular collector surfaces 9.1 and 9.2 are shown. The shape may also be more conical.
[0054] FIG. 5 shows how an exemplary magnet rod 1 is magnetized diametrically, with the end of the rod 1 positioned above an IC with multiple Hall sensors (at least two) 6.1, 6.2, 6.3 and 6.4. As is evident from FIG. 5, one end face of said rod may face an upper face of said IC. An advantage of four sensors is that a wobble in the rod rotation can potentially be negated mathematically using all of the sensors' measurement information. Such a wobble in the rod rotation measurements may be caused by a rod which is not perfectly straight, as one example. Or it may be caused by misalignment between an axis of said rod and a centre point between said four sensors. Being able to mathematically, that is by digital processing, remove wobbling from the rod rotation measurements may greatly ease manufacturing tolerances and constraints.
[0055] In FIG. 6 flux-guides 11.1, 11.2, 11.3 and 11.4 are positioned in an exemplary manner above the various sensor plates 6.1 to 6.4.
[0056] In FIG. 7A flux-guides 11.1 to 11.4 may help to improve magnetic field signal strength when the magnet is far away from the Hall plates and also to handle bigger magnets which may be positioned to rotate around an axis.
[0057] In FIG. 7B the magnet rotation is translated through ninety-degrees by the flux-guides 11.1 to 11.4 and this may allow for the IC containing Hall sensors 6.1, 6.2, 6.3 and 6.4 to be positioned on a PCB 4 that is parallel to the plane of the magnet rotation. In the configurations shown in FIG. 7B the Hall plates may measure flux in the Z-axis direction, with PCB 4 lying in the XY-plane.
[0058] The exemplary embodiment shown in FIG. 8A may be used to measure a spherical magnet 1 that is rotated in any direction. The position can typically not be resolved when the North-South axis is parallel to the IC. The North-South axis is defined as an axis which cuts through the centre of the North pole and the South pole, similar to that conventionally used in the art. So, if the S pole is at the bottom when starting, as depicted in FIG. 8A, the rotation may be accurately measured and the orientation uniquely resolved as long as the S pole does not rotate 90 degrees to the top. In the embodiment shown by FIG. 8A, circular flux collector plates 9.1 to 9.4 may be used to collect magnetic flux from said magnet.
[0059] In FIG. 8B a disc magnet is used that can be positioned inside a sphere to allow more rotations to be resolved.
[0060] The results are excellent as can be seen in the difference in the phase angles of FIGS. 9A and 9B. FIG. 9A shows measurements from a setup shown in FIG. 2, whilst 9B shows measurements from FIG. 4A. The real-world measurements from the two Hall plates are shown with the magnet rotated through 360 degrees. In FIG. 9A using a 10 mm diameter ring magnet, 15 mm away from the IC (centre of magnet) with no flux-guides, the phase difference between the two plates was measured at approximately 8 degrees. In FIG. 9B the signals measured in an embodiment using the same setup but with flux-guides, according to FIG. 4A, show a phase angle difference of approximately 60 degrees.
[0061] Please note the flat sections in the FIG. 9 signals are the result of the stepper motor steps.
[0062] This better phase angle of FIG. 9B translates into a much improved SNR resulting in improvements in e.g., jitter and linearity error. In this practical setup using an Azoteq ProxFusion™ IC this gives an improvement from ±15 degrees accuracy to a ±1 degree accuracy by only adding the flux-guides.
[0063] The flux-guides can be made with ferromagnetic metal such as iron rods or ferromagnetic material/compounds such as ferrite, all with high magnetic permeability compared to the surrounding air. The present invention is not limited only to these materials for the construction of flux-guides, but may use any suitable magnetic material which has a sufficiently high relative magnetic permeability. In addition, the teachings of the present invention may also be practised with flux-guides which differ in configuration, number and structure from those depicted in exemplary manner in the appended drawings or described herein.
[0064] FIGS. 10A and B depict an exemplary embodiment of the present invention in a laptop computer. It should be appreciated that a laptop is merely used as an example of an electronic device, and does not limit the present invention. As shown at 10.1, a laptop base 10.3 and lid 10.2 may move relative to each other, with a hinge 10.4 which may facilitate rotation of the lid 10.2 about an axis 10.5. A disk magnet 10.7, for example a diametrically polarized magnet with one North pole and one South pole, may be located in said base 10.3 as shown. A magnetic field sensor 10.6, for example a Hall-effect sensor, may be located in the lid 10.2, and may have two Hall plates used to measure the magnetic field strength and direction of magnet 10.7. According to the present invention, a first flux-guide 10.9 and a second flux-guide 10.10 may also be positioned in the lid 10.2 as shown in order to increase or improve the phase angle between the signals from the respective Hall plates of sensor 10.6. Although flux-guides 10.9 and 10.10 are drawn at an angle to each other, and with a certain shape and qualitative length, this is merely exemplary, and the present invention should not be limited in this regard. For example, the two flux-guides may be oriented parallel to each other, or at an angle of hundred-and-eighty degrees. They may be significantly shorter or longer, or one may be short and one long, relatively speaking. They may also be fashioned in any form or format and/or orientation needed to increase or improve said phase angle.
[0065] Cross-sectional views along line 10.8 for the laptop lid in an open and closed position is shown at 10.11 and 10.13 respectively in FIG. 10B. As depicted, the two flux-guides 10.9 and 10.10 may follow a path 10.12 about the static magnet 10.7 located in laptop base 10.3.
[0066] FIGS. 11A and B show an exemplary embodiment related to that of FIG. 10, but wherein the locations of the magnet and magnetic field sensor are interchanged. A bar magnet 11.14 with magnetic poles 11.12 and 11.13 may be located in lid 11.6 of a laptop, as an exemplary electronic device. The invention need not be limited to the use of bar magnets, or to that depicted. The lid 11.6 may rotate towards or away from the base 11.7 using a hinge 11.9. A magnetic sensor, for example a two plate Hall sensor, 11.8 may be located in the base 11.7 as depicted. According to the present invention two flux-guides 11.10 and 11.11 may be used to guide flux from the magnet 11.14 in such a manner as to increase or improve the phase angle between signals from respective Hall plates in the sensor 11.8, and/or to improve the measurement of magnetic field strength and direction by said plates in another manner.
[0067] An open and closed lid are shown in cross-sectional views at 11.15 and 11.17 in FIG. 11B respectively. The lid 11.6 may move along a path 11.16 towards and from the base 11.7, as depicted. In light of the foregoing, FIG. 11B is fairly self-explanatory and will not be elaborated on further.
[0068] According to the present invention, flux-guides may also be used with magnetic sensors which are orthogonal to each other within an IC. An exemplary embodiment is shown in a cross-sectional view at 12.1 in FIG. 12, wherein a magnetic sensor IC 12.4, for example a Hall-effect IC, is located on a substrate 12.7, with electrical connections provided via legs or contacts 12.10, as is known in the art. First and second Hall plates 12.8 and 12.9 respectively may be located within IC 12.4, and may be orthogonal to each other, as shown. For example, the plate 12.8 may be located within an XZ-plane and the plate 12.9 may be located within an XY-plane. Flux-guides 12.5 and 12.6 may be used to guide magnetic fields between a magnet 12.2 and said plates, with the magnet 12.2 rotating in either of the directions depicted by 12.3. The present invention teaches that correct location, orientation, geometry and material choice for said flux-guides 12.5 and 12.6 may be used to improve measurement of the magnetic fields of the magnet 12.2. For example, flux-guides 12.5 and 12.6 may be used to increase or change the phase angle between signals from the Hall plates 12.8 and 12.9, thereby facilitating greater ease and/or accuracy of rotation measurement.
[0069] Yet another exemplary embodiment of the present invention is shown at 13.1 in FIG. 13. An IC 13.7 is located on a substrate 13.10 below a magnet 13.2 that rotates in a direction 13.3. The IC may be a magnetic field sensor, for example a Hall-effect IC, and may comprise first and second Hall plates 13.8 and 13.9, Two flux-guides 13.4 and 13.5 may be located above and in close proximity to the IC 13.7, and may guide magnetic fields between the magnet 13.2 and the Hall plates 13.8 and 13.9. The Figure depicts magnetic field lines 13.6 in an exemplary manner, bounded by a box 13.12 for clarity, illustrating said guiding to some extent. According to the present invention, the flux-guides may be used to increase or change the phase angle between the two signals respectively obtained from the Hall plates 13.8 and 13.9. The flux-guides may be used to change the concentration or level of magnetic fields incident on said Hall plates, leading to an increase in the amplitude of signals obtained from said Hall plates. In addition, the present invention teaches that another flux-guide 13.11 may be used on the non-magnet side of the sensor IC 13.7, as shown. This may further reduce the reluctance of the magnetic field path in the magnetic circuit, leading to an increase in field strength measured. It may also increase or change the concentration of magnetic field incident on a particular plate on sensor, and may also be used to affect changes to the phase angle between signals from respective Hall plates or sensors.
[0070] It may also be possible to improve rotation measurement accuracy and cost-effectiveness using a single flux-guide together with an IC containing at least one vertical and at least one horizontal magnetic field sensor. Such an embodiment is depicted in an exemplary manner at 14.1 in FIG. 14. A magnet 14.2, for example a disk magnet or a diametrically magnetized ring magnet, may be located above an IC 14.5, with the latter supported by and located on a PCB 14.9. The magnet 14.2 may rotate in either of the directions shown by the arrows 14.3. IC 14.5 may contain a vertical magnetic field sensor 14.6, for example a vertical Hall sensor or Hall plate, and a horizontal magnetic field sensor 14.7, for example a horizontal Hall sensor or Hall plate. A magnetic flux-guide or flux-conductor 14.4 may be situated between the magnet 14.2 and the IC 14.5, with one end or face of the flux-guide in close proximity to the IC, as depicted. The flux-guide 14.4 may be oriented at an angle 14.8 with the PCB 14.9. According to the present invention, a phase-angle between signals from the vertical and horizontal magnetic field sensors may be increased or improved by the use of the flux-guide 14.4, which may facilitate improved rotation measurement of the magnet 14.2, or of a structure or device attached to said magnet. For example, by setting the flux-guide 14.4 at a specific angle 14.8 for a certain set of parameters, which may include flux-guide material properties and dimensions, magnet field strength, distance between the magnet and IC, flux-guide location and sensor parameters, amongst others, it may be possible to significantly increase said phase-angle and improve rotation measurement. Alternatively, or additionally, other parameters measured by, or associated with, the vertical and horizontal magnetic field sensors may be changed, adjusted or improved through the use of the flux-guide 14.4.
[0071] An exemplary embodiment as depicted in FIG. 14 may enable a cost-reduction by allowing a smaller IC to be used for rotation measurements than what would be the case for two horizontal magnetic field sensors, given the typical minimum distance required between horizontal sensors.
[0072] Herein, “or” is used to convey inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” may mean “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. In addition, “and” is used to convey both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, “A and B” may mean “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context.
