Stray field robust magnetic position sensor array

Abstract

A magnetic field position sensor comprising: a backbias magnet (5) configured to produce at least part of a magnetic field, a sensor arrangement (4) comprising exactly three magnetic field sensor elements (7L; 7C; 7R) which are designed to generate sensor signals in response to the magnetic field, wherein the three magnetic field sensor elements (7L; 7C; 7R) are sensitive to an identical magnetic field component of the magnetic field; and a sensor circuit (8) configured to generate a differential measurement signal based on the sensor signals, wherein a characteristic of the magnetic field changes in response to a position of a target object and the differential measurement signal is representative of the position of the target object with respect to the three magnetic field sensor elements (7L; 7C; 7R), wherein the target object is configured to move laterally across the magnetic field position sensor in a linear path, and wherein the three magnetic field sensor elements (7L; 7C; 7R) share a sensitivity axis and the linear path is parallel to the sensitivity axis, wherein the sensor arrangement (4) is arranged along one side of the backbias magnet (5), wherein the sensor circuit (8) generates the differential measurement signal by means of the formula SE Δ = ( SEC − SEL ) − ( SEC − SER ) where SER corresponds to a resistance value or a voltage value generated by the magnetic field sensor element (7R), SEL corresponds to a resistance value or a voltage value generated by the magnetic field sensor element (7L), SEC corresponds to a resistance value or a voltage value generated by the magnetic field sensor element (7C), and SEΔ corresponds to a delta measurement value and represents a value of the differential measurement signal.

Description

AREA

[0001] The present disclosure relates generally to magnetic position sensing and, more particularly, to stray field robust magnetic position sensors. BACKGROUND

[0002] Magnetic sensors include, for example, magnetoresistive sensors and Hall-effect sensors (Hall sensors). Magnetoresistance is the property of a material to change its electrical resistance when an external magnetic field is applied to it.Some examples of magnetoresistive effects are giant magnetoresistance (GMR), which is a quantum mechanical magnetoresistance effect observed in thin-film structures composed of alternating ferromagnetic and non-magnetic conductive layers, tunnel magnetoresistance (TMR), which is a magnetoresistive effect occurring at a magnetic tunnel junction (MTJ), which is a component consisting of two ferromagnets separated by a thin insulator, or anisotropic magnetoresistance (AMR), which is a property of a material in which a dependence of the electrical resistance on the angle between the direction of the electric current and the direction of the magnetization is observed.The majority of different magnetoresistive effects are commonly abbreviated as xMR, where the "x" stands for the various magnetoresistive effects. xMR sensors can detect the orientation of an applied magnetic field by measuring sine and cosine angular components with monolithically integrated magnetoresistive sensor elements.

[0003] A Hall-effect sensor is a transducer that varies its output voltage (Hall voltage) in response to a magnetic field. It is based on the Hall effect, which utilizes the Lorentz force. The Lorentz force deflects moving charges in the presence of a magnetic field perpendicular to the current flowing through the sensor or the Hall plate. The Hall plate can be a thin piece of semiconductor or metal. This deflection causes charge separation, which creates an electric Hall field. This electric field acts on the charge in the opposite direction to the Lorentz force. Both forces balance each other, creating a potential difference perpendicular to the direction of current flow. The potential difference can be measured as a Hall voltage and varies in a linear relationship with the magnetic field for small values.Hall effect sensors can be used for proximity switching, positioning, speed detection and current sensing applications.

[0004] Currently, a Hall monocell configuration can be used in proximity switching, motion detection, and position sensing applications. For example, a magnetized backbias magnet combined with a Hall monocell sensor generates a signal when a ferrous target (i.e., the detected object) moves in front of the sensor.

[0005] On the downside, Hall monocell sensors have a disadvantage in terms of stray field robustness. Stray fields are magnetic fields introduced by magnetically harsh environments or other external means located in the immediate vicinity of the sensor. A magnetically harsh environment can be caused by large current densities near the sensor (hybridization of vehicles) or electric motors adjacent to the sensing location. For example, components within the vehicle (e.g., for hybrid cars, due to power rails driving high electrical currents close to the sensing device or due to inductive battery charging) can create a magnetically harsh environment. In addition, currents flowing through a rail of a train system that generate a magnetic field can cause stray field disturbance that is detectable when a vehicle is near the rail.Stray field interference can contribute to the measured detection signal. This can cause inaccuracies in the signals generated by the sensor and can affect the overall performance of the sensor system.

[0006] US 2013 / 0 335 069 A1 discloses a magnetic field sensor comprising a plurality of magnetic field sensor elements coupled to an electronic circuit. The magnetic field sensor elements are arranged parallel to a gear. The gear includes gear teeth. The electronic circuit can then determine an output signal from the signals of the magnetic field sensor elements.

[0007] US 2012 / 0 249 133 A1 discloses a sensor arrangement in which a magnetic field sensor is arranged. The magnetic field sensor is arranged in a position such that it can perform a radial scan relative to a target profile. Any movement of the target profile is solely a rotational movement.

[0008] US 2016 123 774 A1 discloses a magnetic field sensor for detecting the movement of a ferromagnetic target object.

[0009] US 5 596 272A discloses a magnetic sensor with a beveled permanent magnet.

[0010] DE 11 2015 001 935 T5 discloses a rotation detection device comprising a signal detector and a determination circuit. The signal detector generates a first signal and a second signal based on changes in the resistance values ​​of magnetoresistive element pairs.

[0011] Therefore, an improved device with a higher tolerance for stray fields may be desirable. SUMMARY

[0012] There may be a need to provide an improved concept for a magnetic field position sensor and a magnetic field sensing method.

[0013] Such a need may be satisfied by the subject matter of one of the claims.

[0014] Some embodiments relate to a magnetic field position sensor comprising at least two magnetic field sensor elements configured to generate sensor signals in response to a magnetic field, wherein the at least two magnetic field sensor elements are sensitive to a same magnetic field component of the magnetic field, and a sensor circuit configured to generate a differential measurement signal based on the sensor signals.

[0015] Optionally, the same magnetic field component is an in-plane magnetic field component.

[0016] Again optionally, the at least two magnetic field sensor elements use a sensitivity axis jointly.

[0017] Optionally, the at least two magnetic field sensor elements comprise a first magnetic field sensor element arranged at a first sensor position and a second magnetic field sensor element arranged at a second sensor position, wherein the differential measurement signal represents a difference between the magnetic field at the first sensor position and the second sensor position.

[0018] Again optionally, the at least two magnetic field sensor elements comprise a first magnetic field sensor element, a second magnetic field sensor element and a third magnetic field sensor element grouped into a first differential pair and a second differential pair, and the sensor circuit is configured to generate a first difference between the sensor signals generated by the first differential pair, generate a first difference between the sensor signals generated by the second differential pair, and generate the differential measurement signal based on a difference between the first difference and the second difference.

[0019] Optionally, a characteristic of the magnetic field changes in response to a position of a target object and the differential measurement signal is representative of the position of the target object with respect to the at least two magnetic field sensor elements.

[0020] Again optionally, the sensor circuit is further configured to generate an output signal as a function of a linear position of the ferromagnetic target relative to the magnetic field position sensor based on the differential measurement signal.

[0021] Optionally, the sensor circuit is configured to generate an output signal based on a linear movement of the ferromagnetic target relative to the at least two magnetic field sensor elements, wherein the sensor circuit is configured to monitor the differential measurement signal and change a logical state of the output signal in response to a trigger event.

[0022] Again optionally, the triggering event is a crossing of a threshold by the differential measurement signal, wherein the threshold corresponds to a predetermined distance of the ferromagnetic target from the at least two magnetic field sensor elements.

[0023] Optionally, the target object is configured to move laterally across the magnetic field position sensor in a linear path, and wherein the at least two magnetic field sensor elements share a sensitivity axis and the linear path is orthogonal or parallel to the sensitivity axis.

[0024] Again optionally, the magnetic field position sensor further comprises a backbias magnet configured to produce at least a portion of the magnetic field, wherein the at least two magnetic field sensor elements and the sensor circuit are integrated on a semiconductor chip, and the semiconductor chip and the backbias magnet are incorporated into a semiconductor package.

[0025] Optionally, the sensor circuit is configured to generate the differential measurement signal by canceling a first, external magnetic stray field component measured by a first magnetic field sensor element and a second, external magnetic stray field component measured by a second magnetic field sensor element.

[0026] Some embodiments relate to a magnetic field sensing method comprising measuring a same magnetic field component of a magnetic field at at least two sensing locations, generating sensor signals comprising a sensor signal for each sensing location based on measuring the same magnetic field component of the magnetic field at the at least two sensing locations, and generating a differential measurement signal based on the sensor signals.

[0027] Optionally, the same magnetic field component is an in-plane magnetic field component.

[0028] Again optionally, the at least two magnetic field sensor elements use a sensitivity axis jointly.

[0029] Optionally, the differential measurement signal represents a difference between the magnetic field at a first detection location and the magnetic field at a second detection location.

[0030] Again optionally, the magnetic field sensing method further comprises grouping a first magnetic field sensor element, a second magnetic field sensor element, and a third magnetic field sensor element into a first differential pair and a second differential pair, and generating the differential measurement signal comprises generating a first difference between the sensor signals generated by the first differential pair, generating a second difference between the sensor signals generated by the second differential pair, and generating the differential measurement signal based on a difference between the first difference and the second difference.

[0031] Optionally, a characteristic of the magnetic field changes in response to a position of a target object and the differential measurement signal is representative of the position of the target object with respect to the at least two detection locations.

[0032] Again optionally, the magnetic field sensing method further comprises generating an output signal as a function of a linear position of the ferromagnetic target relative to the at least two sensing locations based on the differential measurement signal.

[0033] Optionally, the magnetic field sensing method further comprises generating an output signal based on a linear movement of the ferromagnetic target relative to the at least two sensing locations, comprising monitoring the differential measurement signal and changing a logical state of the output signal in response to a trigger event.

[0034] Again optionally, the triggering event is a crossing of a threshold by the differential measurement signal, wherein the threshold corresponds to a predetermined distance of the ferromagnetic target from the at least two detection locations.

[0035] Optionally, generating the differential measurement signal comprises canceling a first, external magnetic stray field component measured at a first detection location and a second, external magnetic stray field component measured at a second detection location.

[0036] Magnetic field position sensors and detection methods are provided.

[0037] In one embodiment, a magnetic field position sensor comprises at least two magnetic field sensor elements configured to generate sensor signals in response to a magnetic field, wherein the at least two magnetic field sensor elements are sensitive to a same magnetic field component of the magnetic field, and a sensor circuit configured to generate a differential measurement signal based on the sensor signals, substantially independently of homogeneous external magnetic stray fields.

[0038] In another embodiment, a magnetic field sensing method comprises measuring a magnetic field using at least two magnetic field sensor elements configured to generate sensor signals in response to the magnetic field, wherein the at least two magnetic field sensor elements are sensitive to a same magnetic field component of the magnetic field, and generating a differential measurement signal substantially independent of homogeneous external stray magnetic fields based on the sensor signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Embodiments are described herein with reference to the accompanying drawings. Fig. 1A-C illustrate schematic diagrams of a magnetic field sensing principle from one or more ferromagnetic targets according to one or more embodiments; Fig. 1D illustrates a graphical diagram of an output signal according to one or more embodiments; Fig. 2 shows a schematic diagram of a sensor system not part of the invention according to claim 1; Fig. 3 shows a schematic diagram of a sensor circuit implemented according to one or more embodiments; Fig. 4 shows a schematic diagram of a sensor system not part of the invention according to claim 1; Fig. 5 shows a schematic diagram of another sensor system according to one or more embodiments; Fig. 6 shows a schematic diagram of another sensor system according to one or more embodiments; and Fig. 7 shows a flowchart of a magnetic field detection method according to one or more embodiments. DETAILED DESCRIPTION

[0040] Details are set forth below to provide a more complete explanation of the exemplary embodiments. However, it will be apparent to those skilled in the art that embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form or in a schematic view rather than in detail to avoid obscuring the embodiments. Additionally, features of the various embodiments described herein may be combined with one another below, unless specifically noted otherwise.

[0041] Furthermore, corresponding or identical elements, or elements with corresponding or identical functionality, are designated by corresponding or identical reference numerals in the following description. Since the corresponding or identical elements in the figures are given the same reference numerals, a repeated description for elements bearing the same reference numerals can be omitted. Thus, descriptions for elements with the same or similar reference numerals are interchangeable.

[0042] It should be noted that when an element is described as being "connected" or "coupled" to another element, the element may be directly connected or coupled to the other element, or intermediate elements may be present. Conversely, when an element is described as being "directly connected" or "coupled" to another element, no intermediate elements are present. Other terms used to describe the relationship between elements should be interpreted similarly (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0043] In embodiments described herein or shown in the drawings, any direct electrical connection or coupling, i.e., any connection or coupling without additional intervening elements, may also be through an indirect connection or coupling, i.e., a connection or coupling with one or more intervening elements, or vice versa, as long as the general purpose of the connection or coupling, for example, transmitting a certain type of signal or transmitting a certain type of information, is substantially retained. Features of different embodiments may be combined to form further embodiments. For example, variations or modifications described with respect to one of the embodiments may also be applicable to other embodiments, unless otherwise stated.

[0044] Embodiments relate to sensors and sensor systems, and obtaining information via sensors and sensor systems. A sensor may refer to a component that converts a physical quantity to be measured into an electrical signal, for example, a current signal or a voltage signal. The physical quantity may include, for example, but is not limited to, a magnetic field, an electric field, a pressure, a force, a current, or a voltage.

[0045] A magnetic field sensor, for example, includes one or more magnetic field sensor elements that measure one or more characteristics of a magnetic field (e.g., a magnitude of a magnetic field flux density, a field strength, a field angle, a field direction, a field orientation, etc.) according to detecting and / or measuring the magnetic field pattern of an element that generates the magnetic field (e.g., a magnet, a current-carrying conductor (e.g., a wire), the ground, or another magnetic field source). Each magnetic field sensor element is configured to generate a sensor signal in response to one or more magnetic fields.

[0046] For example, a sensor signal (e.g., a voltage signal) generated by each magnetic field sensing element may be proportional to the magnitude of the magnetic field. Furthermore, it should be noted that the terms "sensor" and "sensing element" may be used interchangeably throughout this specification, and the terms "sensor signal" and "measured value" may be used interchangeably throughout this specification.

[0047] Magnetic field sensor elements include, but are not limited to, Hall effect sensors (Hall sensors) or magnetoresistive xMR sensors, such as AMR, GMR or TMR sensor elements.

[0048] In some examples, Hall sensor elements may be implemented as vertical Hall sensor elements. A vertical Hall sensor is a magnetic field sensor that is sensitive to a magnetic field component extending parallel to its surface. This means they are sensitive to magnetic fields parallel to or in the plane with the IC surface. The plane of sensitivity may be referred to herein as the "sensitivity axis" or "sensing axis," and each sensing axis has a reference direction. For Hall sensor elements, voltage values ​​output by the sensor elements change according to the magnetic field strength in the direction of the sensing axis.

[0049] In other examples, Hall sensor elements may be implemented as lateral Hall sensor elements. A lateral Hall sensor is sensitive to a magnetic field component perpendicular to its surface. This means they are sensitive to magnetic fields vertical to or outside the plane of the IC (integrated circuit) surface. The plane of sensitivity may be referred to herein as the "sensitivity axis" or "sensing axis," and each sensing axis has a reference direction. For Hall sensor elements, voltage values ​​output by the sensor elements change according to the magnetic field strength in the direction of the sensing axis.

[0050] In other examples, xMR sensor elements may be used. Each xMR sensor element may, for example, be a single-axis or a multi-axis xMR sensor element having a sensing axis used to measure a magnetic field. This sensing axis may, for example, be aligned with one of the magnetic field components within the plane for measuring that field component. Each xMR sensor element may have a reference layer with a reference direction that provides a sensing direction corresponding to the sensing axis. Accordingly, when a magnetic field component points in exactly the same direction as the reference direction, a resistance value of the xMR sensor element is at a maximum, and when a magnetic field component points in exactly the opposite direction to the reference direction, the resistance value of the xMR sensor element is at a minimum.

[0051] According to one or more embodiments, a magnetic field sensor and a sensor circuit may both be housed (i.e., integrated) in the same chip package (e.g., an encapsulated plastic package, such as a lead-in package or leadless package, or a surface-mounted device (SMD) package). This chip package may also be referred to as a sensor package. The sensor package may be combined with a back-bias magnet to form a sensor module, sensor device, or the like.

[0052] The sensor circuit may be referred to as a signal processing circuit and / or a signal conditioning circuit that receives one or more signals (i.e., sensor signals) from the one or more magnetic field sensor elements in the form of raw measurement data and derives a measurement signal representing the magnetic field from the sensor signal. Signal conditioning, as used herein, refers to manipulating an analog signal in such a way that the signal meets the requirements of a next stage for further processing. Signal conditioning may include converting from analog to digital (e.g., via an analog-to-digital converter), amplification, filtering, converting, biasing, ranging, isolation, and many other processes required to make a sensor output suitable for processing after conditioning.

[0053] Thus, the sensor circuit may include a digital converter (ADC) that converts the analog signal from the one or more sensor elements into a digital signal. The sensor circuit may also include a digital signal processor (DSP) that performs processing on the digital signal, as discussed below. Therefore, the sensor housing includes a circuit that conditions and amplifies the small-signal magnetic field sensor element via signal processing and / or conditioning.

[0054] A sensor device, as used herein, may refer to a device comprising a sensor and a sensor circuit, as described above. A sensor device may be integrated on a single semiconductor chip (e.g., a silicon chip or die), although in other embodiments, a plurality of chips may be used to implement a sensor device. Thus, the sensor and the sensor circuit are arranged either on the same semiconductor chip or on multiple chips in the same package. For example, the sensor may be on one chip and the sensor circuit on another chip, such that they are electrically connected within the package. In this case, the chips may be made of the same or different semiconductor materials, such as GaAs and Si, or the sensor could be sputtered onto a non-semiconductor ceramic or glass die.

[0055] Fig. 1A-D illustrate a magnetic field sensing principle of one or more ferromagnetic targets 1 according to one or more embodiments. More specifically, the one or more ferromagnetic targets are made of a ferromagnetic material (e.g., iron) that attracts magnetic fields. Additionally, a sensor assembly 4 is configured to sense a magnetic field generated by a backbias magnet 5, wherein the sensor assembly 4 and the backbias magnet 5 comprise a sensor module 6. The sensor assembly 4 may be generally referred to herein as a sensor or a sensor integrated circuit (IC) and may comprise two or more magnetic field sensor elements and a sensor circuit. Furthermore, the sensor assembly 4 may be arranged in a sensor housing.

[0056] Sensors 4, shown in Fig. 1A-C, are designed to convert magnetic or magnetically encoded information into electrical signals for processing by sensor circuits and can be used in various types of applications, such as detecting position, proximity, speed, velocity, or directional movement. More specifically, magnetic field lines of the bias magnetic field generated by the backbias magnet 5 are pulled more strongly toward the ferromagnetic target 1 as the position of the ferromagnetic target 1 moves closer to the backbias magnet 5. Conversely, the magnetic field lines of the bias magnetic field relax more (i.e., less pull) as the position of the ferromagnetic target 1 moves farther from the backbias magnet or when no backbias magnet 5 is present.

[0057] Thus, directional field components of the bias magnetic field change depending on the position and / or movement of the ferromagnetic target 1. Since the sensor 4 is placed adjacent or near the backbias magnet 5, the sensor 4 is able to detect a change, concerning orientation and / or strength, in one or more directional field components of the bias magnetic field.

[0058] The directional field components may include a magnetic field component Bx (i.e., the magnetic field in the x-plane), a magnetic field component By (i.e., the magnetic field in the y-plane), or a magnetic field component Bz (i.e., the magnetic field in the z-plane). The magnetic field components Bx and By may be referred to as in-plane field components because they are in-plane with the main surface of the sensor assembly 4 (i.e., the sensor IC). Conversely, the magnetic field component Bz may be referred to as an out-of-plane field component because it is out-of-plane with the main surface of the sensor assembly 4 (i.e., the sensor IC).

[0059] It should also be noted that in some embodiments, the target 1 itself may be magnetized. In this case, a backbias magnet may or may not be used, as the sensor 4 may be configured to detect the magnetic field generated by the target 1. In other cases, a ferromagnetic material may be used to replace the backbias magnet to assist in detecting a magnetic field of a magnetized target.

[0060] Fig. Figure 1A shows an example of a linear motion between the sensor module 6 (i.e., the sensor assembly 4 in combination with the backbias magnet 5) and the ferromagnetic target 1. More specifically, the ferromagnetic target 1 moves on a back-and-forth or oscillating path between two extreme positions in the z-direction. As the ferromagnetic target 1 moves along its path in the z-direction, an air gap between the sensor module 6 and the ferromagnetic target 1 changes (i.e., the air gap becomes smaller or larger) and changes at least one directional field component of the bias magnetic field based on its position.

[0061] For example, as the ferromagnetic target 1 moves closer to the sensor module 6 and the air gap decreases, the magnetic field lines of the magnetic field generated by the backbias magnet 5 are pulled in the z-direction toward the ferromagnetic target 1. Thus, the magnetic field lines are pulled away from the x- and y-axes (i.e., the x- and y-sensor planes), and the magnetic field strength in the x- and y-directions is reduced. Meanwhile, the magnetic field strength in the z-direction is increased. The opposite phenomenon occurs when the ferromagnetic target 1 moves farther away from the sensor module 6. Thus, a mechanical motion parameter output protocol of the sensor array 4 can be encoded in a linear manner such that the output (i.e., a measurement signal) of the sensor circuit of the sensor array 4 is linear with respect to the position and motion of the ferromagnetic target 1.

[0062] Fig. 1B shows another example of linear motion of a ferromagnetic target 1. More specifically, the ferromagnetic target 1 moves on a back-and-forth or oscillating path between two extreme positions in the x-direction, parallel to the main surface of the sensor array 4. Again, the orientation and / or strength of one or more of the directional field components changes according to the position of the ferromagnetic target 1 relative to the sensor array 4. Thus, a mechanical motion parameter output protocol of the sensor array 4 can be encoded in a linear manner such that the output (i.e., a measurement signal) of the sensor circuitry of the sensor array 4 is linear with respect to the position and motion of the ferromagnetic target 1.

[0063] Fig. 1C shows another example of a rotational movement of multiple ferromagnetic targets 1a-d (generally referred to as ferromagnetic target 1). The ferromagnetic targets 1a-d may be separate objects or part of a single, integral member, such as teeth on a gear or a shaft. As the ferromagnetic targets 1a-d rotate, they alternate past the sensor module 6, causing one or more directional field components to oscillate between two extremes. For example, the magnetic field sensor elements within the sensor array 4 may detect a change in the x-axis and y-axis magnetic field strength and / or orientation that varies as a sinusoidal waveform (i.e., as a signal modulation) whose frequency corresponds to a rotational speed of the ferromagnetic targets 1a-d and which may further correspond to a rotational speed of the drive shaft (e.g.,camshaft) that drives the rotation of the wheel (in the case where the ferromagnetic targets 1a-d are teeth of a gear). Thus, the sensor circuit of the sensor arrangement 4 can be configured to receive signals (i.e., sensor signals) from the magnetic field sensor elements and to derive a measurement signal representing the magnetic field from the sensor signals as a signal modulation.

[0064] In each example provided herein, the sensor circuit may further convert this measurement signal into an output signal that is a function of the position of the ferromagnetic target 1. Thus, the output signal may represent the linear position of each ferromagnetic target 1 with respect to the sensor module 6. The output signal may also be output to an external controller, control unit, or processor (e.g., an electronic control unit (ECU)).

[0065] Fig. 1D shows an example of an output signal as a linear function of a position of the ferromagnetic target 1 relative to the sensor assembly 4.

[0066] Fig. Figure 2 shows a schematic diagram of a sensor system 200 not part of the invention according to claim 1. More specifically, Fig. 2 shows a sensor system 200 comprising a sensor assembly 4 and a back-bias magnet 5 in the presence of a homogeneous, external stray magnetic field, designed to track the (linear) movement of the ferromagnetic target 1. Note that an enlarged cross-sectional view of the sensor assembly 4 is drawn on the right, connected by dashed extension lines to the sensor element 4, which is drawn in the magnetic field lines between the back-bias magnet 5 and the target 1.

[0067] The sensor assembly 4 comprises two spaced-apart magnetic field sensor elements 7L and 7R that share the same sensitivity axis (e.g., x-axis) but are oriented in opposite sensing directions. More specifically, the magnetic field sensor element 7L has a sensing direction in the -Bx direction, while the magnetic field sensor element 7R has a sensing direction in the +Bx direction. Thus, both magnetic field sensor elements 7L and 7R are sensitive to magnetic fields in the x-plane, but generate signals of opposite signs relative to the in-plane magnetic field component Bx.

[0068] The sensor arrangement 4 further comprises a sensor circuit 8 configured to receive the sensor signals from the magnetic field sensor elements 7L and 7R and generate an analog signal referred to as a differential measurement signal, from which a differential calculation is used. The differential measurement signal may, for example, represent a difference (i.e., a Delta Bx value) between the sensor values ​​(sensor signals) generated by the magnetic field sensor elements 7L and 7R due to the fact that the magnetic field component Bx impinges on each sensor element location.

[0069] The differential equation for the Fig. The example shown in Figure 2 can be a first-order differential equation, such as: SEΔ=SER−SEL where SER corresponds to a resistance value (e.g. for an xMR sensor element) or a voltage value (e.g. for a Hall effect sensor element) generated by the magnetic field sensor element 7R, SEL corresponds to a resistance value or a voltage value generated by the magnetic field sensor element 7L and SEΔ corresponds to a delta measurement value and represents a value of the differential measurement signal.

[0070] It is noted that while the magnetic field sensor elements 7L and 7R in Fig. 2 are configured to detect a magnetic field component Bx within the plane in opposite detection directions, the embodiments are not limited thereto. A differential measurement signal can be generated as long as the magnetic field sensor elements 7L and 7R are configured to detect magnetic field components in the same plane (e.g., field components in the x- or y-plane or field components outside the z-plane). Furthermore, the magnetic field sensor elements 7L and 7R can be configured to have opposite detection directions, as in Fig. 2, or the same detection direction. Accordingly, the differential equation can be adjusted to account for parallel or antiparallel detection directions, as long as a delta value is generated.

[0071] The sensor circuit 8 may further convert the differential measurement signal into an output signal based on a function of the position of the ferromagnetic target 1 (e.g., based on the linear position of the ferromagnetic target 1 relative to the sensor, as best seen from Fig. 1D). For example, the sensor circuit 8 may include a switching mechanism that switches a logical state (e.g., from low to high or from high to low) of the output signal according to the delta Bx value of the differential measurement signal that satisfies a trigger condition.

[0072] Alternatively, the switching mechanism may be a pulse mechanism, such that a signal pulse is generated upon a trigger event, causing the output signal of the sensor array 4 to be modulated, as opposed to a single, logical state transition. In this case, the sensor circuit 8 may provide a pulse of a known length when a trigger event is detected. In some systems, the pulse length may be varied via pulse width modulation, for example, to provide additional information such as an indication of sufficient magnetic field strength, direction of movement, or error flags.

[0073] Still further, the sensor circuit 8 may output the differential measurement signal as the output signal or may convert the differential measurement signal into another type of modulated signal (e.g., linear signal) based on a function of a delta Bx value and the position of the ferromagnetic target.

[0074] A trigger event may refer to the crossing of a threshold. For example, the delta Bx value generated by sensor circuit 8 may decrease as the ferromagnetic target 1 moves closer to the sensor elements 7L and 7R (e.g., the air gap decreases), and the delta Bx value may increase as the ferromagnetic target 1 moves farther away from the sensor elements 7L and 7R (e.g., the air gap increases).

[0075] Thus, a threshold or switching point can be set such that the output signal is modulated based on the delta Bx value. The threshold can be configured to correspond to a specific distance or a specific position of the ferromagnetic target 1 with respect to the sensor array 4 (e.g., from a midpoint between sensor elements). Furthermore, the switching point can be direction-dependent, such that the triggering event only occurs while the ferromagnetic target 1 is moving in a specific direction (e.g., when it is moving closer to or farther away from the sensor array 4).

[0076] The sensor circuit 8 may be further configured to monitor multiple trigger events, such as threshold crossings of two or more thresholds (e.g., a minimum threshold or a maximum threshold), and generate the output signal based on each trigger event or selected trigger events.

[0077] In view of the above, it can be noted that, due to the geometry of the backbias magnet 5, a differential magnetic field is generated at the two positions of the sensor elements 7L and 7R due to the in-plane component Bx of the magnetic field incident at these two positions. A differential measurement signal can be generated by the sensor circuit 8 using differential calculus on the two sensor signals, and an output signal can be generated based on a position or a function of the position of the ferromagnetic target 1.An external device may use the output signal to calculate a position of the ferromagnetic target 1 with respect to the sensor module 6, to determine whether the ferromagnetic target 1 is within or outside a desired proximate range of the sensor module 6, and / or to determine a speed of the ferromagnetic target 1, for example, by counting a number of pulses of the modulated output signal.

[0078] Consider the presence of an external stray magnetic field. When an external stray magnetic field is present, the external stray magnetic field adds a cumulative effect to the already generated backbias field, generating a total magnetic field (target magnetic field + stray magnetic field) detectable by the magnetic field sensor elements 7L and 7R. That is, each magnetic field sensor element 7L and 7R can detect the Bx component of the external stray magnetic field, in addition to the Bx component of the backbias magnetic field. However, it should be noted that the external stray magnetic field affects each magnetic field sensor element 7L and 7R in a similar manner.

[0079] More specifically, the stray magnetic field can cause a shift in the sensed total magnetic field of each magnetic field sensor element 7L and 7R by the same or a similar amount (i.e., within an acceptable tolerance). Thus, the sensor value generated by each magnetic field sensor element 7L and 7R changes by the same or a similar positive or negative amount depending on the orientation and / or strength of the Bx component of the stray magnetic field. Consequently, the difference (i.e., Delta Bx) between the sensor values ​​remains essentially the same compared to the difference that would be realized in the absence of the stray magnetic field. Since Delta Bx remains essentially the same, the stray field in the x-direction can be canceled using the differential calculus described above.

[0080] Accordingly, the sensor circuit 8 is configured to receive sensor signals from the magnetic field sensor elements 7L and 7R and generate a differential measurement signal therefrom using a differential calculation that cancels the homogeneous stray fields in the x-direction. The calculation focuses on the x-component of the stray fields, since the detection axis used to detect the position of the ferromagnetic target 1 is the x-axis, while the y- and z-components do not affect the position detection in this example.

[0081] Fig. 3 illustrates a schematic diagram of a sensor circuit 8 implemented according to one or more embodiments. The sensor circuit comprises spatially distributed magnetic field sensor elements 7 configured to generate a sensor signal in response to a magnetic field impinging thereon. At least two of the magnetic field sensor elements 7 are connected to a differential signal amplifier 11 configured to generate a differential measurement signal from the sensor signals received from the magnetic field sensor elements 7. For example, two of the magnetic field sensor elements 7 may correspond to the sensor elements 7L and 7R shown in Fig. 2 are shown.

[0082] The sensor circuit 8 further includes an ADC and digital core logic 12 configured to perform signal conditioning on the differential measurement signal. More specifically, the ADC and digital core logic 12 may be configured to convert the differential measurement signal into a digital output signal based on one or more signal generation techniques. For example, the ADC and digital core logic 12 may include one or more processors and / or digital logic to generate the output signal based on a trigger event or based on a linear function of the differential measurement signal and the position of the ferromagnetic target 1.

[0083] The sensor circuit 8 further includes an output stage 13 configured to receive the output signal from the ADC and the digital core logic 12 and provide the output signal to one or more output pins 14 of the sensor circuit 8 (i.e., output pins of the sensor chip). Thus, the output signal can be provided to an external component for further use.

[0084] The sensor circuit 8 further includes a voltage regulator 15 configured to regulate and stabilize a voltage provided to one or more circuit components (e.g., magnetic field sensor elements 7, differential signal amplifier 11, ADC and digital core logic 12, and output stage 13). The voltage regulator 15 may receive power from a voltage source, such as a battery, via input pin 16 and may have one or more connections to ground GND.

[0085] Fig. 4 shows a schematic diagram of a sensor system 400 not part of the invention according to claim 1. It is noted that an enlarged cross-sectional view of the sensor arrangement 4 is drawn on the right, connected by dashed extension lines to the sensor element 4 which is drawn in the magnetic field lines.

[0086] More specifically, similar to the sensor system 200 shown in Fig. 2, the sensor system 400 comprises a sensor array 4, a backbias magnet 5, and two spaced-apart magnetic field sensor elements 7L and 7R that have the same sensitivity axis (e.g., x-axis) but are oriented in opposite sensing directions.

[0087] However, instead of the ferromagnetic target 1 moving linearly in front of the sensor module (i.e., the sensor assembly 4 and the backbias magnet 5), the ferromagnetic target 1 moves linearly along a path that traverses one side of the sensor module. Despite the displacement in the placement of the ferromagnetic target 1 relative to the sensor module, however, equation (1) can be used to calculate the differential measurement signal based on the sensor signals generated by the magnetic field sensor elements 7L and 7R.

[0088] Fig. Figure 5 shows a schematic diagram of a sensor system 500 according to one or more embodiments. Note that an enlarged cross-sectional view of the sensor assembly 4 is drawn on the right, connected by dashed extension lines to the sensor element 4, which is drawn adjacent to the magnetic field lines.

[0089] More specifically, similar to the sensor system 200 shown in Fig. 2, the sensor system 500 comprises a sensor array 4 and a backbias magnet 5. However, the sensor array 4 is arranged along one side of the backbias magnet 5 and can be stretched laterally across both magnetic poles of the backbias magnet 5.

[0090] In addition, the sensor system includes three spaced-apart magnetic field sensor elements 7L, 7C, and 7R that have the same sensitivity axis (e.g., x-axis) aligned along the same sensing direction (e.g., the -Bx direction). Thus, a second-order differential equation can be used to generate the differential measurement signal from the sensor signals generated by the magnetic field sensor elements 7L, 7C, and 7R. For example, the sensor circuit 8 can use equation (2) to generate the differential measurement signal: SEΔ=(SEC−SEL)−(SEC−SER) where SER corresponds to a resistance value (e.g. for an xMR sensor element) or a voltage value (e.g. for a Hall effect sensor element) generated by the magnetic field sensor element 7R, SEL corresponds to a resistance value or a voltage value generated by the magnetic field sensor element 7L, SEC corresponds to a resistance value or a voltage value generated by the magnetic field sensor element 7C and SEΔ corresponds to a delta measurement value and represents a value of the differential measurement signal.

[0091] Fig. Figure 6 shows a schematic diagram of a sensor system 600 according to one or more embodiments. Note that an enlarged cross-sectional view of the sensor assembly 4 is drawn on the right, connected by dashed extension lines to the sensor element 4, which is drawn adjacent to the magnetic field lines.

[0092] More specifically, similar to the sensor system 500 shown in Fig. As shown in Figure 5, the sensor system 600 includes a sensor array 4 and a backbias magnet 5. In addition, the sensor system includes three spaced-apart magnetic field sensor elements 7L, 7C, and 7R that share the same sensitivity axis (e.g., x-axis) aligned along the same sensing direction (e.g., the -Bx direction). Thus, equation (2) can be used by the sensor circuit 8 to generate the differential measurement signal.

[0093] While the above examples include the use of two or three magnetic field sensor elements, it should be noted that more than three magnetic field sensor elements may be used as long as they are configured to detect the same magnetic field component for position detection.

[0094] Fig.Figure 7 shows a flowchart of a magnetic field sensing method 700 according to one or more embodiments. Specifically, the sensing method 700 includes generating sensor signals using two or more sensor elements (step 705), generating a differential measurement signal using the sensor signals (step 710), and generating an output signal based on the differential measurement signal and a position of a ferromagnetic target (step 715).

[0095] With regard to the above embodiments, xMR sensor elements or the Hall sensor element are sensitive to the same magnetic field components, e.g., in-plane magnetic field components (parallel to a main surface of the sensor elements) or out-of-plane magnetic field components (perpendicular to the main surface of the sensor elements), and are used to generate a differential measurement signal that is substantially independent (i.e., within an acceptable tolerance) of homogeneous external stray fields, but represents a position of a ferromagnetic target with respect to the sensor elements.

[0096] Additional signal processing and conditioning may be performed to generate a digital output signal. The digital output signal may indicate a position of the ferromagnetic target or may indicate that the ferromagnetic target is within or outside a target proximity of the sensor elements (e.g., a preset distance from the sensor elements). The digital output signal may further be linearized with respect to movement of the ferromagnetic target.

[0097] While the above embodiments are described in the context of detecting a wheel or camshaft speed, the sensor can be used to detect the rotational speed of any rotating member or object that generates sinusoidal fluctuations in a magnetic field as it rotates and that can be sensed by a sensor. For example, a combination of an iron wheel and a back-bias magnet can be used to generate a time-varying magnetic field. Alternatively, an active encoder wheel (without a back-bias magnet) can be used to generate a time-varying magnetic field.

[0098] Furthermore, while various embodiments have been described, it will be apparent to those of ordinary skill in the art that many other embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not intended to be limited except in terms of the appended claims and their equivalents. With regard to the various functions performed by the above-described components or structures (assemblies, devices, circuits, systems, etc.), the terms (including a reference to a "means") used to describe such components are intended, unless otherwise indicated, to correspond to any component or structure that performs the specified function of the described component (e.g.,which is functionally equivalent), although it is not structurally equivalent to the disclosed structure that performs the function in the exemplary implementations of the invention presented herein.

[0099] Furthermore, the following claims are hereby incorporated into the Detailed Description, where each claim may stand on its own as a separate example. While each claim may stand on its own as a separate example, it should be noted that although a dependent claim may refer to a particular combination with one or more other claims in the claims, other examples may include a combination of the dependent claim with the subject matter of any other dependent or independent claim. Such combinations are suggested herein unless it is stated that a particular combination is not intended. Furthermore, features of a claim for any other independent claim are also intended to be included, even if that claim is not made directly dependent on the independent claim.

[0100] It should further be noted that methods disclosed in the description or in the claims may be implemented by an apparatus having means for performing each of the respective steps of those methods.

[0101] Furthermore, it should be understood that the disclosure of multiple steps or functions disclosed in the description or claims should not be construed as being in a particular order. Therefore, the disclosure of multiple steps or functions does not limit them to a particular order, unless these steps or functions are not interchangeable for technical reasons. Furthermore, in some examples, a single step may comprise multiple substeps or be divided into multiple substeps. Such substeps may be included and be part of the disclosure of that single step unless explicitly excluded.

Claims

[1] A magnetic field position sensor comprising: a back-biased magnet (5) configured to produce at least part of a magnetic field, a sensor arrangement (4) comprising exactly three magnetic field sensor elements (7L; 7C; 7R) configured to generate sensor signals responding to the magnetic field, wherein the three magnetic field sensor elements (7L; 7C; 7R) are sensitive to an equal magnetic field component of the magnetic field; and a sensor circuit (8) configured to generate a differential measurement signal based on the sensor signals, wherein a characteristic of the magnetic field changes in response to the position of a target object and the differential measurement signal is representative of the position of the target object with respect to the three magnetic field sensor elements (7L; 7C; 7R), wherein the target object is designed to move laterally across the magnetic field position sensor in a linear path, and wherein the three magnetic field sensor elements (7L; 7C; 7R) share a sensitivity axis and the linear path is parallel to the sensitivity axis, wherein the sensor arrangement (4) is arranged along one side of the backbias magnet (5), wherein the sensor circuit (8) generates the differential measurement signal by means of the formula SEΔ=(SEC−SEL)−(SEC−SER) where SER corresponds to a resistance value or a voltage value generated by the magnetic field sensor element (7R), SEL corresponds to a resistance value or a voltage value generated by the magnetic field sensor element (7L), SEC corresponds to a resistance value or a voltage value generated by the magnetic field sensor element (7C), and SEΔ corresponds to a delta measurement value and represents a value of the differential measurement signal. [2] The magnetic field position sensor according to claim 1, wherein the target object is a ferromagnetic target (1), wherein the sensor circuit (8) is further configured to generate an output signal as a function of a linear position of the ferromagnetic target (1) relative to the magnetic field position sensor based on the differential measurement signal. [3] The magnetic field position sensor according to one of the preceding claims, wherein the target object is a ferromagnetic target (1), wherein the sensor circuit (8) is further configured to generate an output signal based on a linear movement of the ferromagnetic target (1) relative to the three magnetic field sensor elements (7L; 7C; 7R), wherein the sensor circuit (8) is configured to monitor the differential measurement signal and to change a logical state of the output signal in response to a trigger event. [4] The magnetic field position sensor according to claim 3, wherein the triggering event is a crossing of a threshold by the differential measurement signal, the threshold corresponding to a predetermined distance of the ferromagnetic target (1) from the three magnetic field sensor elements (7L; 7C; 7R). [5] The magnetic field position sensor according to any one of the preceding claims, further comprising: wherein the three magnetic field sensor elements (7L; 7C; 7R) and the sensor circuit (8) are integrated on a semiconductor chip, and the semiconductor chip and the back bias magnet (5) are placed in a semiconductor package. [6] The magnetic field position sensor according to one of the preceding claims, wherein the sensor circuit (8) is configured to generate the differential measurement signal by eliminating a first, external magnetic stray field component, measured by a first magnetic field sensor element, and a second, external magnetic stray field component, measured by a second magnetic field sensor element. [7] A magnetic field detection method comprising: Measuring an identical magnetic field component of a magnetic field at exactly three detection locations using a sensor arrangement (4) comprising three magnetic field sensor elements (7L; 7C; 7R); Generating sensor signals, comprising one sensor signal for each detection location, based on measuring the same magnetic field component of the magnetic field at the three detection locations; and Generating a differential measurement signal based on the sensor signals, wherein a characteristic of the magnetic field changes responsively to a position of a target object, and the differential measurement signal is representative of the position of the target object with respect to the three detection locations, wherein the target object is configured to move laterally across the magnetic field position sensor in a linear path, and wherein the three magnetic field sensor elements (7L; 7C; 7R) share a sensitivity axis and the linear path is parallel to the sensitivity axis, wherein the sensor arrangement (4) is arranged along one side of a backbias magnet (5), wherein the sensor circuit (8) generates the differential measurement signal by means of the formula SEΔ=(SEC-SEL)−(SEC−SER) where SER corresponds to a resistance value or a voltage value generated by the magnetic field sensor element (7R), SEL corresponds to a resistance value or a voltage value generated by the magnetic field sensor element (7L), SEC corresponds to a resistance value or a voltage value generated by the magnetic field sensor element (7C), and SEΔ corresponds to a delta measurement value and represents a value of the differential measurement signal. [8] The magnetic field detection method according to claim 7, further comprising: Generating an output signal as a function of a linear position of the ferromagnetic target (1) relative to the three detection locations based on the differential measurement signal. [9] The magnetic field detection method according to one of claims 7-8, further comprising: Generating an output signal based on a linear movement of the ferromagnetic target (1) relative to the three detection locations, comprising monitoring the differential measurement signal and changing a logical state of the output signal in response to a trigger event. [10] The magnetic field detection method according to claim 9, wherein the triggering event is a crossing of a threshold by the differential measurement signal, the threshold corresponding to a predetermined distance of the ferromagnetic target (1) from the three detection locations. [11] The magnetic field detection method according to any one of claims 7 to 10, wherein: The generation of the differential measurement signal includes the deletion of a first, external magnetic stray field component, measured at a first detection location, and a second, external magnetic stray field component, measured at a second detection location.

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