Reduced-volume printed circuit board for inductive sensor for measuring angular position

Abstract

A printed circuit board for an inductive sensor intended to measure the angular position of a target, said printed circuit board comprising:-at least two secondary windings (22a), each consisting of at least one pair of poles (23), each extending along a circular arc equal to 360 DEG / Ntot, where Ntot is an integer greater than or equal to 2; and-a primary winding (21) surrounding the secondary winding. According to the invention: each secondary winding (22a) comprises a number N0 of pairs of poles, wherein 1 < = N0 < = (Ntot-1); and-the primary winding (21) delimits a surface of interest inscribed inside the disk, referred to as the active disk, wherein the ratio between the area of the surface of interest and the area of the active disk is between 70% and 99%. The invention finds applications, in particular in the automotive field, for measuring the angular position of the rotor of an electric motor. This allows optimal coupling between the winding and the target to be provided, while complying with the major constraints in terms of the available space for integrating the winding.

Description

Technical Field

[0001] The field of the invention is that of detecting the position of a moving mechanical structure, in particular a rotor of a rotating machine, by means of a target mounted integrally with said structure.

[0002] The invention more particularly relates to an inductive sensor configured to enable measurement of the position of a rotating component, particularly, but not exclusively, a rotating shaft or rotor of a rotating electrical machine. Background Art

[0003] In a manner known per se, angular inductive sensors have a structure similar to that of linear inductive sensors: they comprise: a fixed part, called a "transformer" and comprising a fixed primary winding and at least two fixed secondary windings; and a movable part consisting of a metal target rigidly connected to the mechanical part to be angularly controlled.

[0004] The stationary primary winding and the stationary secondary winding are typically implemented on a printed circuit board and both constitute conductive traces that are routed on the printed circuit board.

[0005] The operating principle of this sensor is based on the variation of the coupling between the primary winding and the secondary winding which together form a transformer operating at high frequency and without the use of magnetic circuits. In use, the current induced in the target will modify the voltage induced in the secondary winding by the primary winding. In other words, the coupling between the primary winding and the secondary winding varies depending on the position of the target. By adapting the configuration of the windings and, if necessary, by knowing the current injected into the primary winding, the measurement of the voltage induced in the secondary winding allows the position of the target to be determined.

[0006] In a more detailed manner, in use, a high frequency alternating current flows in the primary winding, generating a magnetic field at the same frequency.

[0007] Each secondary winding is surrounded by the primary winding and forms at least two loops. The consecutive loops all surround substantially the same surface. The consecutive loops intersect each other and therefore have opposite orientations from a trigonometric point of view. Each secondary winding is composed of one or more pairs of these loops, each pair of loops comprising two consecutive loops with opposite orientations. Paired loops are referred to as "paired poles", one of the loops forming a positive pole and the other of the loops forming a negative pole.

[0008] Due to the coupling between the primary winding and the loops of each secondary winding, the primary flux creates a magnetic flux of each secondary circuit that is seen to reverse from one loop to the other.

[0009] The primary and secondary windings are configured for use with a metal target as mentioned above, rigidly connected to the mechanical component to be angularly controlled. The movement of the target modifies the coupling between the primary winding and each loop of each secondary winding.

[0010] In particular, the successive positions of the target in front of the loops of each secondary winding generate in these loops a certain amount of magnetic flux, said amount varying with time according to the frequency of the current passing in the primary winding. A voltage is therefore present at the ends of these secondary windings. The sign of this voltage depends on the direction of the loops. The algebraic sum of these voltages varies according to the displacement of the target in front of these loops, following a curve that is quite close to a sine.

[0011] Measuring the voltage induced at the ends of the secondary winding thus allows the position of the mechanical component to be known.

[0012] When the inductive sensor is the sensor for measuring the angular position, it is known to arrange the primary winding and the secondary winding in a circle. An example of such a sensor is described, for example, in patent application US 2014 / 0167788 A1.

[0013] exist Figure 1A and Figure 1B , a winding of an inductive sensor for measuring angular position according to the prior art is illustrated. The winding here comprises a primary winding and two secondary windings. For ease of understanding, Figure 1A shows the primary winding and the first secondary winding, and Figure 1B A second secondary winding is shown.

[0014] The primary winding 11 is circular in shape and has ports for inputting and outputting current. It can be formed by a plurality of concentric circles superimposed on various layers and / or faces of a printed circuit board. It surrounds the secondary windings 12a and 12b.

[0015] Each of the secondary windings 12a and 12b surrounds a disk-shaped surface opened at the center and has a port for inputting and outputting current. The secondary windings 12a and 12b are arranged concentrically with the primary winding 11.

[0016] Each of the secondary windings 12a and 12b is formed by at least one pair of poles 120 (here two pairs of poles). Each pair of poles extends along a circular arc of an angle α, where α=360° / N, and N is an integer greater than or equal to the unit corresponding to the total number of pairs of poles in each secondary winding.

[0017] As mentioned above, each pair of poles 120 is formed by two loops 121 and 122 of equal size oriented in opposite directions. Each loop may be made up of a plurality of turns (not shown) angularly offset relative to each other to allow their implementation on the same printed circuit board.

[0018] The two secondary windings 12a, 12b are substantially identical and differ from each other only in rotation by an angle β, where β = 360° / (4*N).

[0019] The primary winding and the secondary winding are generally integrated on the same printed circuit board with electrical components having the function of supplying power to the primary winding and / or the function of measuring the voltage value at the ends of the secondary winding.

[0020] On a printed circuit board, the electrical components are generally arranged next to the windings.

[0021] The distance between the electrical component and the winding must be large enough to avoid electromagnetic coupling between the winding and the electrical component in use. In addition, manufacturing constraints dictate a minimum spacing in order to avoid damaging the electrical traces forming the winding when integrating the electrical component.

[0022] This constraint sometimes forces a reduction in the size of the winding, which then extends along a disk of reduced diameter, in order to ensure sufficient spacing relative to the electrical components. The disadvantage is therefore that the coupling coefficient between the winding and the target is reduced and may prove insufficient in view of possible other constraints in terms of the distance between the target and the winding (air gap).

[0023] The object of the present invention is to propose a solution for overcoming the aforementioned drawbacks.

[0024] In particular, the object of the invention is to propose a printed circuit board for an inductive sensor for measuring the angular position of an object, providing both optimal coupling to said object and optimal flexibility in terms of volume. Summary of the invention

[0025] This object is achieved with a printed circuit board for an inductive sensor intended for measuring the angular position of an object, the printed circuit board comprising:

[0026] - at least two secondary windings, each secondary winding consisting of at least one pair of poles, each pair of poles extending along a line equal to 360° / N tot The circular arc extends, where N tot is an integer greater than or equal to 2; and

[0027] - A primary winding which surrounds the secondary winding.

[0028] According to the present invention:

[0029] - Each secondary winding includes a number N 0 Pairs of poles, where 1≤N 0 ≤(N tot -1); and

[0030] The primary winding defines a surface of interest inscribed inside a disk called the active disk, wherein the ratio between the area of ​​the surface of interest and the area of ​​the active disk is between 70% and 99%.

[0031] As a variant, this ratio is greater than 80%, even greater than 90%, and even greater than 95%. In addition, this ratio can be less than 99%, even less than 98%, and even less than 96%.

[0032] In other words, starting from the winding of an inductive sensor according to the prior art, and as Figure 1A and Figure 1B As shown in the figure, one or even more pairs of poles are removed from the secondary winding, and the path followed by the secondary winding is adjusted so as to approximate the shape of the disk as much as possible while passing a certain distance from the determined obstacle.

[0033] The present invention thus simultaneously allows:

[0034] - the windings pass at a certain distance from possible obstacles on the printed circuit board; and

[0035] The winding extends in a shape close to a disk, wherein the diameter of the disk is large enough to ensure an optimal coupling with the target without having to reduce the distance between the target and the winding.

[0036] There is a compromise found between:

[0037] - the shape of the windings and the proximity between the disks, the shape of the disks providing a rotational symmetry that makes the inductive sensor less sensitive to misalignment of the target (the measurement of position is the average of the response of multiple pairs of poles in each of the windings); and

[0038] - The diameter of the disk, which determines the shape of the winding, the coupling coefficient with the target and therefore the accuracy of the sensor, the larger this diameter the higher the sensor accuracy.

[0039] The disk defining the shape of the winding is called the "active disk". According to the invention, the primary winding surrounds the secondary winding and defines a surface of interest inscribed inside the active disk, wherein the area ratio % between the area of ​​the surface of interest and the area of ​​the active disk is between 70% and 90%.

[0040] The invention thus provides an optimal coupling between the winding and the target, while allowing compliance with the constraints of the mechanical integration, such as the presence of the electrical components at defined locations on the printed circuit board.

[0041] The invention also provides strong robustness and low sensitivity to misalignment between the winding and the target by virtue of the shape of the winding being close to that of a disk. In this respect, it differs from alternative solutions in which the secondary windings each comprise only a single pair of poles, wherein the primary windings follow exactly the contour of the secondary windings.

[0042] In the introductory part the presence of electrical components on a printed circuit board was mentioned as an example of mechanical constraints for integrating windings on a printed circuit board. It is understood that the invention is not limited to this example and finds its application in many other situations where any ideal surface desired for the windings is not available.

[0043] The primary winding comprises: at least one portion in the shape of a circular arc, which can follow the outer contour of the secondary winding; and at least one connecting line, which connects the two ends of the at least one portion in the shape of a circular arc. Furthermore, according to the invention, the surface of interest defined by the primary winding passes through the center of the active disk. Thus, the primary winding follows the outer contour of the secondary winding, but passes at a distance from the inner contour of the secondary coil.

[0044] The diameter of the active disk is advantageously less than or equal to 30 mm.

[0045] In an advantageous manner, the primary winding comprises at least one portion in the shape of a circular arc, which follows the circumference of the secondary winding.

[0046] The primary winding may further include: at least one straight portion connecting two ends of the portion in the circular arc shape together.

[0047] Preferably, the secondary windings extend together along a circular arc of between 200° and 340°.

[0048] The number of pole pairs N 0 Advantageously greater than or equal to 2.

[0049] At least two pairs of poles can be arranged directly after each other. The primary winding can then be formed as follows:

[0050] The circular arc portion; and

[0051] A straight portion connects the ends of the circular arc-shaped portions together.

[0052] According to an advantageous variant, the number N of pole pairs 0 is a multiple of 2, and the paired poles are distributed into two groups spaced apart from each other. The two groups are advantageously arranged in rotational symmetry with a rotation angle of 180°. The primary winding can then be constructed as follows:

[0053] Two parts in the shape of circular arcs; and

[0054] Two straight portions connect the ends of the circular arc-shaped portions in pairs.

[0055] The printed circuit board according to the invention may further comprise an electronic device having the function of supplying power to the primary winding and / or measuring the voltage value at the end of the secondary winding, the electronic device being arranged outside the primary winding and at least partially inside the active disk. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Other features and advantages of the present invention will become more apparent when reading the following description. This description is purely illustrative and should be read with reference to the accompanying drawings, in which:

[0057] [ Figure 1A ];and

[0058] [ Figure 1B ] illustrates the windings of an inductive sensor for measuring angular position according to the prior art;

[0059] [ Figure 2A ];and

[0060] [ Figure 2B ] illustrates windings of a printed circuit board of an inductive sensor for measuring angular position according to a first embodiment of the present invention;

[0061] [ Figure 3 ] illustrates in a schematic manner a surface of interest according to the invention and an effective disk according to the invention;

[0062] [ Figure 4 ] illustrates in a schematic manner a winding of a printed circuit board according to the invention for use with a corresponding object;

[0063] [ Figure 5A ];and

[0064] [ Figure 5B ] illustrates the windings of a printed circuit board of an inductive sensor for measuring angular position according to a variation of the first embodiment of the present invention;

[0065] [ Figure 6 ] illustrates one of the secondary windings and the primary winding of a printed circuit board of an inductive sensor for measuring angular position according to a second embodiment of the present invention; and

[0066] [ Figure 7 ] illustrates a printed circuit board according to the invention, which also includes an electrical component occupying a portion of a disk defining the shape of a winding. DETAILED DESCRIPTION

[0067] To facilitate understanding of the present invention, Figures 1A to 6 Only windings consisting of metal traces formed on a printed circuit board are shown. The metal traces can extend along two opposite faces of the printed circuit board, wherein the through-holes partially penetrate the printed circuit board in the thickness direction. As a variant, the metal traces can also extend into the middle layer of a multilayer printed circuit board.

[0068] First refer to Figure 2A and Figure 2B A winding of a printed circuit board according to the invention is described. Figure 2A The primary winding 21 and the first secondary winding 22a are shown. Figure 2B The second secondary winding 22b is shown.

[0069] Figure 2A and Figure 2B will only target them relative to Figure 1A and Figure 1B The differences in windings are described.

[0070] exist Figure 2A and Figure 2B In the diagram, the winding is shown in a top view in a plane parallel to the plane of the printed circuit board.

[0071] Each secondary winding 22a, 22b is composed of at least one pair of poles 23, each pair of poles 23 having a length along α' equal to 360° / N. tot The circular arc extends, where N tot is an integer greater than or equal to 2. Here N tot =4.

[0072] exist Figure 2A and Figure 2B In the figures, pairs of poles 23 are represented in a schematic manner and each comprises a loop oriented in a first direction, indicated by a "+" sign, and a loop oriented in the opposite direction, indicated by a "-" sign. For reasons of readability of the figures, the details of the turns forming each of the loops are not represented, the turns being able to be distributed on one or more layers, this aspect being an element known from the prior art and not constituting the core of the present invention.

[0073] Each secondary winding 22a, 22b includes a number N 0 Pairs of poles 23, where 1≤N 0 ≤(N tot -1). Here we have N 0 =3.

[0074] The two secondary windings 22a and 22b are substantially identical and differ from each other only by a rotation by an angle β', where β'=360° / (4*N tot ).

[0075] The two secondary windings 22 a and 22 b are surrounded by the primary winding 21 .

[0076] The primary winding 21 has a portion 211 in the shape of a circular arc, and a connection line 212 which is located at a position where the at least one pair of poles does not exist and connects both ends 213 and 214 of the portion 211 in the shape of a circular arc.

[0077] The primary winding 21 may be made up of a plurality of concentric turns distributed over one or more layers. Again, for reasons of readability, each of these turns is not represented separately.

[0078] Here, the line 212 is a straight line. In a variant not shown, the two ends 213 and 214 are connected by a curve or any other non-straight track forming an open line. In any case, the line 212 is configured to bypass a predetermined obstacle.

[0079] The circular arc-shaped portion 211 here extends over an angle of between 270° and 330° following the outer contour of the secondary windings 22 a and 22 b .

[0080] In any case, the primary winding defines a surface of interest S1 (see Figure 3 , shaded area), which is inscribed inside a disk called effective disk D1. Here, the surface of interest S1 has the shape of a truncated disk, having the same diameter as the effective disk D1.

[0081] The ratio between the area of ​​the surface of interest S1 and the area of ​​the active disk D1 is between 70% and 99%, here of the order of 98%.

[0082] Furthermore, in an advantageous manner, the surface of interest S1 passes through the center of the active disk D1 . This therefore ensures that the shape of the surface of interest S1 does not deviate too much from the shape of the active disk D1 .

[0083] Figure 4 The winding of a printed circuit board according to the invention for use with a corresponding target 40 is illustrated in a schematic manner and according to a perspective view as a perspective view.

[0084] The target 40 is a metal target that is integrally arranged on a mechanical element that is rotationally movable and whose angular position is desired to be measured.

[0085] The target 40 comprises a plurality of blades arranged in a generally circular shape. In particular, the number of blades is equal to N as defined above. tot Here, there are therefore four blades. Each blade extends to the same extent over the angular sector, and the angular distribution of the blades is regular.

[0086] The target 40 is arranged concentrically with the active disc as defined above.

[0087] The object 40 is the same as the object intended to cooperate with a printed circuit board according to the prior art, including the number N tot Pairs of poles.

[0088] exist Figure 4 In an embodiment, the winding of the printed circuit board comprises:

[0089] a primary winding 41 , here formed by four turns: two concentric turns on a first face of the printed circuit board, superimposed on two other concentric turns on the opposite face of the printed circuit board; and

[0090] The three secondary windings 42a, 42b, 42c each consist of a plurality of turns, each turn extending on a first side and an opposite side of the printed circuit board, and each secondary winding comprises two pairs of poles, wherein each pair of poles extends at an angle of 120°.

[0091] Figure 5A and Figure 5B The windings of a printed circuit board of an inductive sensor for measuring angular position according to a variation of the first embodiment of the invention are shown. Fig. 5 shows a primary winding 51 and a first secondary winding 52a. Figure 5B The second secondary winding 52b is shown.

[0092] Here, in order to reduce the overall volume requirement of the secondary windings 52a and 52b, the second secondary winding 52b comprises two half loops 521 having the same orientation at its ends. Thus, the surface occupied by the first secondary winding 52a is exactly superimposed on the surface occupied by the second secondary winding 52b, despite the angular offset between their respective pairs of poles. At the second secondary winding, the pairs of poles 53 can be defined as a whole loop and two half loops located on one side and the other side of the whole loop.

[0093] In the variants described above, in each secondary winding, pairs of poles are arranged directly following one another.

[0094] Figure 6 One of the secondary windings 62a and the primary winding 61 of a printed circuit board of an inductive sensor for measuring angular position according to a second embodiment of the present invention is shown.

[0095] This embodiment will only focus on its relative Figure 2A and Figure 2B The differences between the embodiments are described below.

[0096] In this embodiment, the number of paired poles N in each of the secondary windings is 0is a multiple of 2. In each secondary winding, the paired poles are distributed into two groups 630c, 630d. Each group 630c, 630d includes the same number of paired poles. Here, but in a non-limiting manner, each group 630c, 630d includes a single paired pole.

[0097] In each of the secondary windings, the two groups 630c, 630d are arranged spaced apart from each other. Here, and in an advantageous manner, they are symmetrical to each other according to a rotational symmetry of an angle of 180°. This symmetry provides, by construction, at least partial compensation for possible mechanical offsets in the integration (especially between the winding and the target).

[0098] The respective groups 630c, 630d of the plurality of secondary windings are superimposed on each other to form two turn blocks.

[0099] The primary winding 61 surrounds a plurality of secondary windings. The primary winding 61 has:

[0100] A first portion 611c in the shape of a circular arc follows the contour of the first block in the turn blocks;

[0101] A second portion 611d in the shape of a circular arc, following the contour of another of the turn blocks;

[0102] A first connecting line 612c connecting two corresponding ends of the first arc-shaped portion 611c and the second arc-shaped portion 611d; and

[0103] The second connecting line 612d connects the other two corresponding ends of the first arc-shaped portion 611c and the second arc-shaped portion 611d.

[0104] Here, the first connecting line 612c and the second continuous line 612d are both straight. In variations not shown, a curve or any other non-straight track forming an open connecting line may be involved. The first connecting line and the second connecting line are not necessarily similar, one may be straight, and the other may not be straight.

[0105] In this embodiment, the secondary windings 62a extend together along a cumulative circular arc of between 200° and 340°.

[0106] at last, Figure 7 A printed circuit board 700 according to the present invention is shown.

[0107] The printed circuit board 700 includes:

[0108] A substrate 701 for accommodating the primary winding and the secondary winding, the substrate comprising at least one electrically insulating layer, two opposite faces of the at least one electrically insulating layer being covered with metal traces; and

[0109] The primary winding 71 and the secondary winding 72a of the windings described above (for reasons of readability of the figure) are shown in FIG. Figure 7 A single secondary winding 72a is shown in FIG.

[0110] exist Figure 7 In the embodiment of FIG. 7 , the printed circuit board 700 further includes an electrical component 770 having a function of supplying power to the primary winding 71 and a function of measuring a voltage value at an end of the secondary winding 72 a .

[0111] The electrical components 770 include, for example, at least one microcontroller.

[0112] The electrical component 770 extends outside the surface of interest defined by the primary winding 71, near the primary winding 71, and is partially located as shown in FIG. Figure 3 The defined effective disk D1 is extended.

[0113] Thanks to the invention, the primary winding 71 is kept at a sufficient distance from the electrical component 770, without having to move the electrical component 770 (which increases the overall volume of the printed circuit board) and without having to reduce the diameter of the disk defining the shape of the winding. As explained in the introduction, this large diameter allows maintaining a high coupling between these windings and the target.

[0114] The present invention is not limited to the examples and variations described above. Various examples and variations can be combined with each other. The number of secondary windings can be two, three or even more. The secondary windings can each include multiple paired poles, or even a single paired pole.

[0115] In an advantageous manner, the effective disk D1 ( Figure 3 ) has a diameter less than or equal to 50 mm, or even less than or equal to 30 mm. For these diameters, the inductive coupling is high between the primary winding and the secondary winding and between the winding and the target. It is thus possible to offset the primary winding locally relative to the secondary winding without constraining the performance of the sensor. It is also possible to offset the target relative to the winding to facilitate mechanical implementation.

[0116] In an advantageous manner, the invention finds application in the automotive field, in particular for measuring the angular position of an electric motor rotor. The printed circuit board according to the invention is advantageously configured to be placed at the end of a rotating shaft. In a less preferred variant, the printed circuit board according to the invention can be configured to be spanned by the rotating shaft. In any case, it differs from a printed circuit board intended to be placed around a rotating shaft at a distance from the axis of rotation of the shaft.

[0117] The invention is particularly advantageous for adapting an inductive sensor on a pre-existing printed circuit board on which available space for the winding is provided. The invention in particular allows providing an optimal coupling between target and winding as mentioned above, while complying with the main constraints in terms of available space for integrating the winding.

[0118] Preferably, each pair of poles is along a line equal to 360° / N tot The circular arc extends, and each secondary winding includes a number N 0 The paired poles of N 0 =N tot -1 or N 0 =N tot -2.

Claims

1. A printed circuit board (700) for an inductive sensor intended to measure the angular position of an object, the printed circuit board (700) comprising: - at least two secondary windings (22a, 22b; 42, 42b, 42c; 52a, 52b; 62a; 72a), each secondary winding is composed of at least one pair of loops, called pairs of poles (23; 53), which surround corresponding surfaces of the same size, are oriented in opposite directions and are each composed of one or more turns, and each pair of poles is along a line equal to 360° / N tot The circular arc extends, where N tot is an integer greater than or equal to 2; and - a primary winding (21; 41; 51; 61; 71) which surrounds the secondary winding; in: - Each secondary winding (22a; 22b; 42; 42b; 42c; 52a; 52b; 62a; 72a) comprises a number N0 of paired poles, where 1≤N0≤(N tot -1); It is characterized in that the primary winding (21; 41; 51; 61; 71): - having: at least one portion (211; 611c, 611d) in the shape of a circular arc; and at least one connecting line (212; 612c, 612d) connecting two ends (213, 214) of the at least one portion in the shape of a circular arc; and - defining a surface of interest (S1) inscribed inside a disk called effective disk (D1), wherein the ratio between the area of ​​the surface of interest and the area of ​​the effective disk is between 70% and 99%, the surface of interest (S1) passing through the center of the effective disk (D1).

2. The printed circuit board (700) according to claim 1, wherein the diameter of the effective disk (D1) is less than or equal to 30 mm.

3. The printed circuit board (700) according to any one of claims 1 or 2, wherein the at least one portion (211; 611c, 611d) in the shape of a circular arc follows the perimeter of the secondary winding.

4. A printed circuit board (700) as described in claim 3, wherein the at least one connecting line (212; 612c, 612d) connecting the two ends (213, 214) of the circular arc-shaped part is a straight part (212; 612c, 612d) of the primary winding (21; 41; 51; 61; 71).

5. A printed circuit board (700) as claimed in any one of claims 1 to 4, wherein the secondary windings (22a, 22b; 42, 42b, 42c; 52a, 52b; 62a; 72a) extend together along a circular arc between 200° and 340°.

6. The printed circuit board (700) according to any one of claims 1 to 5, wherein the number N0 of paired poles is greater than or equal to 2.

7. The printed circuit board (700) as claimed in claim 6, wherein at least two pairs of poles (23; 53) are arranged directly following one another.

8. The printed circuit board (700) according to claim 7, wherein the primary winding (21; 41; 51; 71) is composed as follows: a circular arc-shaped portion (211); and A straight portion (212) connects the ends (213, 214) of the circular arc-shaped portions together.

9. The printed circuit board of claim 6, wherein the number N0 of paired poles is a multiple of 2, and the paired poles are distributed into two groups (630c, 630d) spaced apart from each other.

10. The printed circuit board as claimed in claim 9, wherein the two groups (630c, 630d) are arranged rotationally symmetrically with a rotation angle of 180°.

11. A printed circuit board as claimed in claim 9 or 10, wherein the primary winding (61) is composed of: Two parts (611c, 611d) in the shape of circular arcs; and Two straight portions (612c, 612d) connect the ends of the circular arc-shaped portions in pairs.

12. The printed circuit board (700) as described in any one of claims 1 to 11, further comprising an electronic device (770), which has the function of supplying power to the primary winding (71) and / or measuring the voltage value at the end of the secondary winding (72a), and the electronic device (770) is arranged outside the primary winding (71) and at least partially inside the effective disk.

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