Untitled record

(54) Title: SENSOR FOR DETECTING THE DIRECTION OF A MAGNETIC FIELD AND ANGULAR SENSOR (73) Holder: MELEXIS TESSENDERLO NV, Belgian Company. Address: Transportstraat 1, BE-3980, Tessenderlo, Belgium (BE).

(72) Inventor: RADIVOJE POPOVIC; ROBERT RACZ; CHRISTIAN SCHOTT

Validity Period: 10 (ten) years from 01/21/2015, subject to legal conditions.

Issued: January 21, 2015.

Digitally signed by:

Liane Elizabeth Caldeira Lage

Deputy Patent Director

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SENSOR FOR DETECTING THE DIRECTION OF A MAGNETIC FIELD AND ANGULAR SENSOR

The invention relates to a sensor for detecting the direction of a magnetic field of the type cited in the generic concept of claim 1.

Such a sensor is suitable, for example, for use as an angular sensor in controlling brushless electric motors with a multi-coil stator. The electric motor's rotor has a permanent magnet that interacts with the sensor to generate a signal to control the coils according to the phases and the rotation angle. This type of arrangement is described in European patent application EP 954 085. A vertical Hall element with multiple arms is used as the sensor, with a Hall voltage generated in each arm depending on the position of the permanent magnet. Hall voltages are used to control the motor coils.

<td>electric. 0</td><td>Hall element</td><td>vertical</td><td>and</td><td>sensitive to</td>

<td>components</td><td colspan="2">of the magnetic field created by the</td><td>magnet</td><td>permanent and</td>

<td colspan="2">that are parallel to the surface</td><td>of the chip.</td><td>He</td><td>presents the</td>

<td>disadvantage</td><td>of not being able to be</td><td>carried out</td><td>node</td><td>same chip,</td>

together with the electronic processing circuit, as it is based on a special semiconductor technology.

The use of horizontal Hall elements, sensitive to the components of the magnetic field created by the permanent magnet, which manifest vertically on the chip surface, is also known. These Hall elements can be integrated into the same chip as the electronic processing circuit. However, this solution has the disadvantage that the Hall elements must be

2/15 are located in the marginal area of the permanent magnet, where the vertical components of the magnetic field are most intense. In the area of the rotating shaft, the vertical components are therefore of low intensity. The positioning of the Hall elements depends on the dimensions of the permanent magnet. For larger permanent magnets, it is not cost-effective to integrate the Hall elements on a single chip.

An angular sensor with a magnetic field sensing element based on the magnetoresistance effect is known from European patent application EP 893 668. It also includes a horizontal Hall element, which allows the measurable angular range to be increased to more than 180°. The Hall element, however, must be positioned differently from the magnetic field sensing element because, while the magnetic field sensing element must measure the horizontal components of the rotating permanent magnet's magnetic field, the Hall element must measure its vertical components. Sensors based on the magnetoresistance effect also exhibit hysteresis effects, which, in turn, limit dispersion capability.

European patent application EP 772 046 discloses a magnetic field sensor that is sensitive to magnetic fields arranged parallel to the chip surface and can be implemented on a semiconductor chip, along with the electronic circuit. This type of magnetic field sensor can measure only a single component of the magnetic field.

The invention aims to suggest a sensor that does not present the disadvantages mentioned above.

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The invention has the features cited in claim 1. An advantageous design is the result of the subordinate claims.

According to the first aspect of the invention, the sensor comprises for detecting the direction of a magnetic field only a single flat-shaped field concentrator and at least one first and one second Hall element or at least one first and one second group of Hall elements, the Hall elements being arranged in the marginal area of the magnetic field concentrator.

The flat magnetic field concentrator has the task of influencing an external magnetic field in such a way that it passes through the Hall elements optimally.

Hall elements can be horizontal or vertical. Horizontal Hall elements are sensitive to components of the magnetic field that arise vertically to their surface, while vertical Hall elements react to a component of the magnetic field parallel to their surface. For this reason, horizontal Hall elements should be arranged below the magnetic field concentrator and vertical Hall elements in the area near the edge, outside the magnetic field concentrator.

According to another aspect of the invention, the sensor for detecting the direction of a magnetic field comprises at least three magnetic field concentrators arranged symmetrically in a plane in relation to a point of symmetry, which have, in the area of the point of symmetry, ends facing each other, in parallel, in addition to a Hall element or a group of Hall elements per magnetic field concentrator, the elements being

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Hall are ordered in the area of the parallel ends of the respective magnetic field concentrator.

Below, the invention will be explained in more detail, with the help of drawings.

The following is shown:

Fig. 1 - a first example of a sensor with horizontal Hall elements consistent with the invention.

Fig. 2 - sensor with a cut along line II in Fig. 1.

Fig. 3 - a second example of a sensor consistent with the invention.

Fig. 4 - Sensor details.

Fig. 5, 6 - an example of a sensor with elements of

Vertical halls consistent with the invention.

Fig. 7a, b - sensors consistent with the invention, through which the direction of the external magnetic field can be determined in three dimensions, and

Fig. 8-11 - other sensors consistent with the invention.

Fig. 1 shows a top view of a sensor consistent with the invention, suitable, for example, as an angular sensor for controlling a brushless electric motor with three coils. The sensor comprises a semiconductor chip (1) with six horizontal Hall elements (2.1 to 2.6) and a single magnetic field concentrator (3). In this first example, the magnetic field concentrator (3) is disk-shaped and the six Hall elements 2 are spread at uniform distances along the edge (4) of the magnetic field concentrator (3).

Hall elements (2.1 to 2.6) are realized with

5/15 generally known technology, preferably with CMOS technology as n-doped well (6) (Fig. 2) on a p-doped substrate (Fig. 2) . The horizontal Hall elements are sensitive to the components of the magnetic field that arise vertically on the surface (8) of the semiconductor chip (1) . In the example, the Hall elements (2.1 to 2.6) have a cross-shaped structure, the alignment of which is preferably parallel to the crystal axis, so that the influence of varying mechanical stresses on the Hall signal is kept as low as possible.

The magnetic field concentrator (3) is composed of a ferromagnetic material, preferably Permalloy or Mumetall, or a metallic glass, which, for example, can be purchased in a thickness of approximately 15 pm to 30 pm. Preferably, a metallic glass with a relatively low coercive field is used to prevent hysteresis effects. Furthermore, its magnetization is completely isotropic.

The magnetic field concentrator (3) extends in a plane (9) and has a planar shape, i.e. its thickness is considerably less than its extension in the plane. The magnetic field concentrator (3) preferably has a uniform thickness. However, it may be thicker in the center than at the edge. The magnetic field concentrator (3) therefore acts as a concentrator for the magnetic field components that lie in the plane (9). The operation of the magnetic field concentrator (3) is explained in more detail in Fig. 2. In this example, the magnetic field concentrator

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<td> (3)</td><td>presents a center</td><td>of</td><td>symmetry</td><td> (5)</td><td>what</td><td>and</td>

<td colspan="2">rotationally symmetric.</td><td></td><td></td><td></td><td></td><td></td>

<td></td><td>Fig. 2 shows the sensor</td><td>in a</td><td>cut to</td><td>far away</td><td colspan="2">of the line</td>

<td>II</td><td>of fig. 1, in addition to a</td><td>magnet</td><td>permanent</td><td> (10)</td><td>what</td><td>if</td>

is mounted on the shaft (11) of a brushless electric motor (12) with three coils and which generates a magnetic field. The magnetic field concentrator (3) alters the course of the field lines (13) of the magnetic field, causing, in particular, the field lines, which in the absence of a magnetic field concentrator (3) would run parallel to the surface (8) of the semiconductor chip (1), to pass through the Hall element (2.1)

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<img file="BRPI0103428B1_D0002.tif" />

permeability almost vertically

<img file="BRPI0103428B1_D0003.tif" />

(<img file="BRPI0103428B1_D0004.tif" />) concentrator

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the magnetic

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bigger

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while air permeability

<img file="BRPI0103428B1_D0008.tif" />

<img file="BRPI0103428B1_D0009.tif" />

<img file="BRPI0103428B1_D0010.tif" />

approximately and

of the substrate

<img file="BRPI0103428B1_D0011.tif" />

semiconductor verticals

<img file="BRPI0103428B1_D0012.tif" />

surface practically

<img file="BRPI0103428B1_D0013.tif" />

<img file="BRPI0103428B1_D0014.tif" />

<img file="BRPI0103428B1_D0015.tif" />

concentrator

<img file="BRPI0103428B1_D0016.tif" />

magnetic

<img file="BRPI0103428B1_D0017.tif" />

<img file="BRPI0103428B1_D0018.tif" />

<img file="BRPI0103428B1_D0019.tif" />

area

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lateral edge (4) of the magnetic field concentrator (3), since in this position the vertical component of the magnetic field has the largest dimension.

Hall elements positioned opposite each other, diametrically relative to the center of symmetry (5) (fig. 1) form pairs for generating the output signal, with the Hall voltage of one of the Hall elements being subtracted from the Hall voltage of the other element. Because the field lines penetrate both Hall elements of a pair in opposite vertical directions, the voltages arising from the deviation of the magnetic field are

<img file="BRPI0103428B1_D0021.tif" />

7/15 are added together, while Hall voltages, arising, for example, due to an external stray field penetrating the Hall elements, cancel each other out. In addition, technology-driven offset voltages are at least partially compensated. The Hall elements (2.1) and (2.4) therefore jointly generate the output signal S_lzHall elements (2.2) and (2.5) generate the output signal S₂ and the Hall elements (2.3) and (2.6) generate the output signal S3. The intensity of the output signals Si, S₂ and S3 depends on the direction of the magnetic field in plane (9).

If the permanent magnet (10) rotates around the axis (11), the magnetic field rotates along with it, generating, for example, the sinusoidal output signals Si, S₂ and S3, which have a phase shift of 120°. The output signal Si assumes the maximum value whenever the direction of the magnetic field of the permanent magnet (10) is parallel to the axis that joins the Hall elements (2.1) and (2.4), the output signal S₂ assumes the maximum value whenever the direction of the magnetic field of the permanent magnet (10) is parallel to the axis that joins the elements (2.3) and (2.5), etc. The output signals Si, S₂ and S₃, as described in European patent application EP 954085, can be used to control the three coils of the electric motor (12).

However, the output signals Si, S₂ and S3 can also be used to determine the rotation angle φ of the shaft (11), if the electric motor (12) is stopped. At this point, it is important that, as far as possible, no signal is superimposed on the output signals Si, S₂ and S₃which do not originate from the magnetic field of the permanent magnet (10). The suggested example with the elements of

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Hall elements combined in pairs are particularly suitable for this purpose, since interference from external fields is completely eliminated and technology-driven offset voltages are fully compensated. Technology-driven offset voltages can be further reduced when, instead of isolated Hall elements (2.1 to 2.6), groups of two or more Hall elements are used, with the current direction varying across the various elements within a group.

An example of this type is illustrated in Fig. 3, in which there are four groups (14 to 17), each with two Hall elements (2.1 to 2.8). The groups of Hall elements, positioned diametrically opposite each other, are combined in pairs, so that the sensor provides two output signals Si and S₂. This means, therefore, that the output signal Si is formed from the Hall voltages of the Hall elements (2.1), (2.2), (2.5) and (2.6) and the output signal S is formed from the Hall voltages of the elements (2.3), (2.4), (2.7) and (2.8).₂. In Fig. 3, the Hall elements are cross-shaped, and each Hall element is assigned an arrow indicating the direction of flux within the element. In this example, the magnetic field concentrator (3) also has a cross-shaped structure, which causes the magnetic field concentration at the location of the Hall elements to be greater than in the previous example with the circular structure. This sensor is suitable, for example, for controlling an electric motor (12) with two coils. If necessary, it is possible to memorize the value of the output signals Si and S₂ as a function of the rotation angle φ. Because the output signals Si and S₂ be out of phase, the angle of

9/15 rotation φ can be easily and uniquely determined through the output signals S_x and S₂.

Fig. 4 illustrates schematically and not true to scale, referring to the sensor of the first example, the semiconductor chip (1) with both Hall elements (2.1) and (2.4) integrated, which are positioned diametrically opposite each other, in a plane relative to the axis (11) (see also fig. 1), in addition to the circular magnetic field concentrator (3). The vertical arrows indicate the intensity and direction of the field created by the permanent magnet (10) (fig. 2) in the area of the two Hall elements (2.1) and (2.4). A displacement of the magnetic field concentrator (3) from the ideal position in the positive x direction causes a reduction in the Hall voltage in element (2.1) and an increase in the Hall voltage in element (2.4). An advantage is that the diameter of the magnetic field concentrator (3) has been adapted in such a way to the two Hall elements (2.1) and (2.4) that both elements (2.1) and (2.4), with the magnetic field concentrator (3) in the optimal position with reference to the two Hall elements (2.1) and (2.4), are not in the zone, in which the magnetic field intensity reaches its maximum value: The Hall elements (2.1) and (2.4) are positioned close to the center, as shown in fig. 4, or away from the center. The influence of variations in the positioning of the magnetic field concentrator (3) in relation to the two Hall elements (2.1) and (2.4) is thus minimized.

If the sensor is used only to control an electric motor, and the rotation angle when the motor stops is not important, it is sufficient that it is available

10/15 only one of the Hall elements joined as a pair. In the first example of realization, these Hall elements are (2.1), (2.2) and (2.3).

Instead of a circular magnetic field concentrator, a concentrator with another shape, such as a polygon, can also be used. Especially for photolithographic reasons, it may be convenient to approximate the circular shape with a polygon. Similarly, the number of Hall elements can be increased.

Fig. 5 shows an example of an embodiment with vertical Hall elements (2). Vertical Hall elements are sensitive to the components of the magnetic field that penetrate the Hall element parallel to the surface (8) of the semiconductor chip (1). An example of a Hall element that can be integrated into the electronic circuit is described in the American patent US 5,572,058. The vertical Hall elements (2) are aligned tangentially to the edge (4) of the magnetic field concentrator (3). They are located in the area of the edge (4) of the magnetic field concentrator (3), but not below the magnetic field concentrator (3), where the field lines (13) of the magnetic field (fig. 2) parallel to the surface (8) of the semiconductor chip (1) are largest.

Fig. 6 indicates by means of arrows the intensity of the horizontal lines (13) (fig. 2) of the magnetic field in the area of the vertical Hall elements (2), with the length of the arrow being proportional to the intensity of the magnetic field.

The advantages of these solutions over known solutions in the current technical standard are as follows:

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a) The position of the Hall elements relative to the permanent magnet is not critical, since the Hall elements do not have to be positioned at the edge of the permanent magnet, where the vertical component of the magnetic field is largest, but rather in the area of the rotating shaft, where the horizontal components are largest, so that the positioning of the semiconductor chip, in which the Hall elements are integrated, can occur independently of the position of the edge of the permanent magnet.

b) The magnetic field concentrator further strengthens the magnetic field in the area of the Hall elements.

c) The Hall elements and the electronic processing circuit are integrable on the same semiconductor chip.

d) A deviation of the actual position of the magnetic field concentrator in relation to its theoretical position, within common manufacturing tolerances, has no influence on the generated signals.

The sensors described are also suitable as an angular sensor for the applications described in the above-mentioned European patent application EP 893 668.

Fig. 7a shows a third example of a sensor corresponding to the invention, in which the magnetic field concentrator (3) has the form of a ring. This allows the arrangement of a further horizontal Hall element (2'), for example in the center of the ring, through which it is possible to measure the components of the magnetic field that run parallel to the Hall element (2'). This type of sensor is suitable, for example, for application in a joystick, as this way the direction of the field

12/15 external magnetic can be determined three-dimensionally.

Because the magnetic field concentrator (3) is very thin, it has virtually no influence on the component of the magnetic field that strikes the Hall element (2') vertically. The sensor illustrated in Fig. 7b can also be used to determine the direction of the external magnetic field in three dimensions. However, there is a danger here that horizontal components will overpower the vertical component, since, firstly, the magnetic field concentrator (3) reinforces the horizontal components and, secondly, in the event of changes in the theoretical position of the magnetic field concentrator, horizontal components of the magnetic field can penetrate the Hall element (2') in the vertical direction.

It should be noted that in the example illustrated by Fig. 7a, the magnetic field concentrator (3) can also act as a concentrator for the vertical component of the magnetic field, exactly then when the width of the ferromagnetic ring is comparable to its thickness. From the sum of the signals of the two Hall elements (2.1) and (2.3) or from the sum of the signals of the two Hall elements (2.2) and (2.4), a signal can be obtained that is proportional to the vertical component of the magnetic field, while the difference, as shown above, allows the determination of the horizontal components. The Hall element (2') can even be suppressed.

A single Hall element requires a relatively small area of a few tens of micrometers. The diameter of the magnetic field concentrator

13/15 circular is approximately 0.2 to 0.5 mm. In the ideal case, the diameter of the magnetic field concentrator is smaller than the diameter of the permanent magnet, which is typically 1.3 mm or larger.

Typically, an external field above 20 mT causes a saturation effect in the magnetic field concentrator. If the theoretical distance between the permanent magnet and the sensor is selected such that the magnetic field concentrator is at least partially saturated, the advantage is that the output signals Si and S₂, etc. do not depend or depend little on variations in distance from the sensor's permanent magnet.

It is also possible to apply Hall elements as pulse emitters, in which case the rotating permanent magnet generates as many pulses as the number of Hall elements present.

Fig. 8 shows an angle sensor with three magnetic field concentrators (18.1), (18.2) and (18.3), which, like the sensor of the first example, together with a permanent magnet with angle emitter effect, is suitable as an angle sensor for controlling a three-coil electric motor. The magnetic field concentrators (18.1), (18.2) and (18.3) are arranged symmetrically with respect to a symmetry point (19), more precisely with a rotational symmetry of 120°. In the edge area (4) of each magnetic field concentrator facing the symmetry point (19) there is a horizontal Hall element (2.1), (2.2) or (2.3). The edge (4) of the magnetic field concentrators is subdivided into two areas, more precisely an internal area, in which edges

14/15 (20) of the concentrators (18.1), (18.2) and (18.3) arranged opposite each other assume a parallel position, so that the density of the magnetic field lines is as homogeneous as possible in the gap between both edges (20) and a saturation of the tips is avoided, and an external area, in which the distance between neighboring magnetic field concentrators is too great, in order to prevent the magnetic field from being short-circuited here. The outer edge (21) of the magnetic field concentrators (18.1), (18.2) and (18.3) is spread over an area of as large an angle as possible in order to concentrate the external magnetic field as efficiently as possible in the area of the Hall elements (2.1), (2.2) or (2.3) and to avoid saturation peaks, which could influence the angular dependence of the signals. In this example, each Hall element (2.1), (2.2) or (2.3) outputs a signal S_lz S₂ or S₃.

Instead of isolated Hall elements (2.1), (2.2) or (2.3), groups of Hall elements that have already undergone an offset correction between them can be envisaged.

Figs. 9 and 10 show two other sensors with four magnetic field concentrators (18.1) to (18.4), with which the direction of a magnetic field can be determined in two spatial dimensions. Here, two Hall elements positioned oppositely and diametrically relative to the symmetry point (19) are connected as a pair: Hall elements (2.1) and (2.3) together generate the output signal Si; elements (2.2) and (2.4) together generate the output signal S₂. Through the output signals S_x and S₂ it is possible to determine the direction of the magnetic field in the plane (9) of the sensor.

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In the sensors shown in Figs. 8 to 10, the magnetic field concentrators do not have to be flat. They can have a thicker edge or be coupled to additional external magnetic field concentrators 5 to concentrate the magnetic field in the area of the Hall elements as efficiently as possible.

Fig. 11 shows an example of an embodiment with three magnetic field concentrators (18.1), (18.2), (18.3) and three vertical Hall elements (2.1), (2.2), (2.3) which are respectively arranged in the center, between the parallel edges (20) of the concentrators (18.1), (18.2), (18.3).

While the embodiments and applications of this invention have been shown and described, it is clear to those skilled in the art that these models offer further possibilities for modification than could be explained above, without abandoning the concept of the invention. Therefore, the invention should not be restricted except with respect to the claims.

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