Current sensor and circuit arrangement with a converter and a current sensor

Abstract

Sensor (1), comprising: a power line (2), wherein the sensor (1) is designed to measure a current intensity of a current flowing through the power line (2), a first magnetically sensitive element (8), and a magnetic core (3) which at least partially encloses the power line (2) and which has a first gap (5), wherein the first magnetically sensitive element (8) is arranged in the first gap (5) of the magnetic core (3), and wherein the power line (2) and the magnetic core (3) form an inductance and are connected to a capacitor (11) to form a filter circuit.

Description

[0001] The present invention relates to a sensor. In particular, it can be a sensor for measuring the current intensity of a current flowing through a power line.

[0002] Measuring current is necessary in a wide variety of applications. For example, in an electric vehicle, a high voltage supplied by a battery is converted to a lower voltage, such as 12 V, in a corresponding DC-DC converter. The sensor can be used to measure the current output by the DC-DC converter.

[0003] A sensor for measuring current is described, for example, in US 8,080,994 B2.

[0004] Furthermore, filter elements are known that can be connected to a power line to increase electromagnetic compatibility (EMC). Such filter circuits are known, for example, from US 2013 / 0154766 A1.

[0005] An object of the present invention is to provide an improved sensor which, for example, in addition to measuring a current, fulfills an additional function.

[0006] This object is achieved by a sensor according to the present claim 1.

[0007] A sensor is proposed that comprises a power line, a first magnetically sensitive element, and a magnetic core. The sensor is designed to measure the current intensity of a current flowing through the power line. The magnetic core at least partially surrounds the power line and has a first gap. The first magnetically sensitive element is arranged in the first gap of the magnetic core. The power line and the magnetic core further form an inductance and are connected to a capacitor to form a filter circuit.

[0008] In addition to its primary function of measuring the current flowing through the power line, the sensor also fulfills a second function: forming the filter circuit. This filter circuit can, for example, contribute to increasing electromagnetic compatibility. It is therefore not necessary to implement the filter circuit using completely separate elements. Integrating the filter circuit and sensor instead makes it possible to implement them as a single functional unit, thus reducing the space required for the sensor and filter circuit. For example, when using the sensor in an electric vehicle, space requirements are of great importance, and reducing the required space represents a significant advantage.

[0009] The magnetically sensitive element can be one that is sensitive to the existing magnetic field strength. Accordingly, the magnetically sensitive element can be suitable for measuring the magnetic field strength. If a current flows through the power line, a magnetic field is induced that surrounds the power line. The sensor can determine the current strength by measuring this magnetic field.

[0010] The magnetic core can be made of a ferromagnetic material. In particular, the magnetic core can be designed to influence the course of the magnetic field forming around the power line in such a way that a particularly high magnetic field strength is present at the location of the magnetically sensitive element. In this way, the magnetic core contributes to significantly increasing measurement accuracy.

[0011] The magnetic core can further contribute to electromagnetic shielding of the first magnetically sensitive element against interfering electromagnetic fields. In particular, the magnetic core can prevent the measurement of the first magnetically sensitive element from being distorted by interfering electromagnetic fields.

[0012] The filter circuit can, for example, comprise an LC filter, with the L element being formed by the inductance created by the power line and the magnetic core, and the C element being formed by the capacitor. The LC filter can be designed to filter out harmonic components of a direct current flowing through the power line.

[0013] Furthermore, the filter circuit can be suitable for suppressing alternating current components of a current flowing through the power line. These alternating current components can, in particular, be harmonics, which arise, for example, from the transformation of a high voltage into a lower voltage in a corresponding converter. Thus, by connecting the sensor to the converter, electromagnetic compatibility can be increased because the alternating current components are filtered out.

[0014] The filter circuit can be designed to filter out both low frequency AC components and high frequency AC components.

[0015] Furthermore, the filter circuit can comprise additional inductors and / or additional capacitors. Accordingly, the filter circuit can comprise, for example, an LCL or LCLCL filter. The additional inductors can also be formed by the power line and additional magnetic cores that enclose the power line in such a way that an air gap remains between the respective magnetic core and the power line.

[0016] Furthermore, the magnetic core can have a second gap, and a second magnetically sensitive element can be arranged in the second gap. The second magnetically sensitive element can also be suitable for measuring the magnetic field strength of a magnetic field induced by a current flowing through the power line. The use of the first and second magnetically sensitive elements can increase measurement accuracy. In particular, the second magnetically sensitive element enables differential measurements to be performed.

[0017] The second gap of the magnetic core is an optional feature that is not required for the sensor's functionality. However, measurement accuracy can be increased by placing a second magnetically sensitive element in the second gap.

[0018] The first magnetically sensitive element can comprise a Hall sensor. The second magnetically sensitive element can also comprise a Hall sensor. Hall sensors provide a simple and reliable way to measure magnetic field strengths.

[0019] The first magnetically sensitive element can be connected to an evaluation unit configured to calculate the current strength of the current flowing through the power line from a magnetic field strength measured by the first magnetically sensitive element. Similarly, the second magnetically sensitive element can also be connected to an evaluation unit configured to calculate the current strength from the magnetic field strength measured by the second magnetically sensitive element. In particular, the respective magnetically sensitive elements and the respective evaluation unit can be arranged on a common chip. This allows the space requirement to be reduced.

[0020] The first magnetically sensitive element can output its measurement data in analog or digital format. If the first magnetically sensitive element is connected to the first evaluation unit, the first evaluation unit can have an output connection to which the measurement data determined by the first evaluation unit can be output either digitally or analogically. The same applies to the second magnetically sensitive element and the second evaluation unit.

[0021] The power line can be arranged in the magnetic core such that an air layer is located between the power line and the magnetic core. Accordingly, the power line and the magnetic core cannot touch each other. In particular, the air layer can separate the power line from the magnetic core on either side of the power line.

[0022] The precise design of the power line and the magnetic core allows the thickness of the air layer to be determined. The inductance created by the magnetic core and the power line depends on the thickness of the air layer. The thickness of the air layer can then be selected to achieve the desired inductance.

[0023] The sensor can have at least one additional magnetic core that at least partially encloses the power line. This additional magnetic core and the power line can form a second inductance, which also forms part of the filter circuit. The second inductance can be an L-element of the filter circuit.

[0024] According to a further aspect of the present invention, it relates to a circuit arrangement comprising a converter for converting electrical voltages and the sensor described above.

[0025] The converter can, in particular, be a converter designed to convert a high voltage into a low voltage. Such converters are used, for example, in electric vehicles to convert a high voltage supplied by a battery. The sensor described above can be used both to measure the current voltage output by the converter and to suppress harmonics that arise during voltage conversion.

[0026] In particular, the sensor can be connected to an output of the converter. The sensor makes it possible to measure the current output by the converter and, using the filter circuit, to filter out alternating current components in the current output by the converter.

[0027] The converter can in particular be a DC-DC converter.

[0028] In the following, the invention is explained in more detail with reference to figures and exemplary embodiments. Fig. 1 shows a cross section through a sensor according to a first embodiment. Fig. 2 shows a sensor in a perspective side view. Fig. 3 shows a cross section through a sensor according to a second embodiment.

[0029] Fig. Figure 1 shows a cross-section through a sensor 1. The sensor 1 is designed to measure the current intensity of a current flowing through a power line 2. The power line 2 is a component of the sensor.

[0030] The sensor 1 further comprises a magnetic core 3. The magnetic core 3 comprises a magnetic material, in particular a ferromagnetic material. In particular, the magnetic core 3 can be made of the magnetic material or the ferromagnetic material. The magnetic core 3 at least partially encloses the power line 2.

[0031] The magnetic core 3 has two C-shaped parts which enclose the power line 2 in such a way that they do not touch each other, but a first gap 5 and a second gap 9 are formed between them.

[0032] In the Fig. In the embodiment shown in Figure 1, the power line 2 has a rectangular cross-section. The magnetic core 3 has a substantially quadrangular cross-section, with an inner, also quadrangular, region of the magnetic core 3 being cut out. The power line 2 is arranged in this cut-out region. Furthermore, two thin strips are cut out, forming the first gap 5 and the second gap 9.

[0033] Alternatively, the power line 2 and the magnetic core 3 can have any other cross-section shape. For example, the power line 2 could have a round cross-section and the magnetic core 3 could have an O-shaped cross-section.

[0034] In particular, the power line 2 is arranged such that an air layer 4 remains between the power line 2 and the magnetic core 3. In particular, the air layer 4 is arranged on each side of the power line 2 so that the air layer 4 separates the power line 2 from the respective inner side 7 of the magnetic core 3. Accordingly, the magnetic core 3 and the power line 2 do not directly touch each other.

[0035] Furthermore, the magnetic core 3 has the first gap 5. The first gap 5 extends through the magnetic core 3. In particular, the first gap 5 connects an outer side 6 of the magnetic core 3 to an inner side 7 of the magnetic core 3. A first magnetically sensitive element 8 is arranged in the first gap 5.

[0036] Furthermore, the magnetic core 3 in the Fig. 1, the second gap 9 is arranged at a different location than the first gap 8.

[0037] If a direct current flowing through the power line 2 changes, or if a direct current flowing through the power line 2 contains alternating current components, a magnetic field is induced in both cases, which surrounds the power line 2. The magnetic field is captured and shaped by the magnetic core 3. In particular, the magnetic core 3 is designed to conduct the magnetic field to the first magnetically sensitive element 8. Accordingly, the magnetic core 3 ensures that a particularly high field strength is present at the location of the first magnetically sensitive element 8.

[0038] The first magnetically sensitive element 8 is configured to measure the magnetic flux density at its location. For example, the first magnetically sensitive element 8 can comprise a Hall sensor. Furthermore, the first magnetically sensitive element 8 is connected to a first evaluation unit 10. In particular, the first magnetically sensitive element 8 and the first evaluation unit 10 can be arranged on a common chip. The first evaluation unit 10 is configured to calculate the current strength present in the power line 2 based on the magnetic field strength measured by the first magnetically sensitive element 8.

[0039] Fig. 2 shows a side view of the Fig. 1 sensor shown in cross section 1. In Fig. 2 shows that the power line 2 is further connected to a capacitor 11. A first terminal 12 of the capacitor 11 is electrically connected to the power line 2. Furthermore, the capacitor 11 has a second terminal 13. The second terminal 13 of the capacitor 11 can be connected, for example, to a reference potential (not shown). The reference potential can be, for example, a housing at which a ground potential is present. Alternatively, the capacitor 11 can be connected to another power line or to another capacitor.

[0040] The magnetic core 3 and the power line 2 form an inductance. The inductance is formed by the air layer 4 arranged between the magnetic core 3 and the power line 2. Together with the capacitance of the capacitor 11, this inductance forms an LC filter. The LC filter here forms a filter circuit for electromagnetic compatibility. In particular, the filter can suppress alternating current components of a current flowing through the power line 2. For example, a substantially direct current can flow through the power line 2, but which has harmonics with an alternating current component. The LC filter is designed to filter out these harmonics.

[0041] In Fig. 2 also shows a second optional magnetic core 14. The second magnetic core 14 is structurally identical to the first magnetic core 3 and also at least partially encloses the power line 2. However, no magnetically sensitive element is arranged in the second magnetic core 14.

[0042] An air layer is also arranged between the second magnetic core 14 and the power line 2, which ensures that the second magnetic core 14 and the power line 2 also form an inductance. The two inductances and the capacitance of the capacitor 11 form Fig. 2, an LCL filter is used, which contributes to electromagnetic compatibility. Furthermore, additional inductors and / or additional capacitors can be provided, forming additional L or C elements of a filter circuit.

[0043] Fig. 3 shows a second embodiment of the sensor 1. The Fig. Sensor 1 shown in Figure 3 differs from the one shown in Fig. 1 only in that a second magnetically sensitive element 15 is arranged in the second gap 9 of the magnetic core 3. The second magnetically sensitive element 15 is also designed to measure the magnetic field strength of a current flowing through the power line 2. The second magnetically sensitive element 15 is arranged on a chip on which a second evaluation unit 16 is arranged. The second evaluation unit 16, in turn, calculates the current strength of the current flowing through the power line 2 from the measurement data of the second magnetically sensitive element 15.

[0044] The measurement accuracy can be increased by using two magnetically sensitive elements 8, 15. Furthermore, the use of two magnetically sensitive elements 8, 15 allows for differential measurements. List of reference symbols 1 sensor 2 power lines 3 magnetic core 4 air layer 5 first gap 6 Outside of the magnetic core 7 Inside of the magnetic core 8 first magnetically sensitive element 9 second gap 10 first evaluation unit 11 Capacitor 12 first connection 13 second connection 14 second magnetic core 15 second magnetically sensitive element 16 second evaluation unit

Claims

[1] Sensor (1), comprising: a power line (2), wherein the sensor (1) is designed to measure a current intensity of a current flowing through the power line (2), a first magnetically sensitive element (8), and a magnetic core (3) which at least partially encloses the power line (2) and which has a first gap (5), wherein the first magnetically sensitive element (8) is arranged in the first gap (5) of the magnetic core (3), and wherein the power line (2) and the magnetic core (3) form an inductance and are connected to a capacitor (11) to form a filter circuit. [2] Sensor (1) according to claim 1, wherein the filter circuit is suitable for suppressing alternating current components of a current flowing through the power line (2). [3] Sensor (1) according to one of the preceding claims, wherein the filter circuit comprises further inductors and / or further capacitors. [4] Sensor (1) according to one of the preceding claims, wherein the magnetic core (3) has a second gap (9) and a second magnetically sensitive element (15) is arranged in the second gap (9). [5] Sensor (1) according to one of the preceding claims, wherein the first magnetically sensitive element (8) comprises a Hall sensor. [6] Sensor (1) according to one of the preceding claims, wherein the first magnetically sensitive element (8) is connected to an evaluation unit (10) which is designed to calculate the current intensity of the current flowing through the power line (2) from a magnetic field intensity measured by the first magnetically sensitive element (8). [7] Sensor (1) according to claim 6, wherein the first magnetically sensitive element (8) and the evaluation unit (10) are arranged on a common chip. [8] Sensor (1) according to one of the preceding claims, wherein the power line (2) is arranged in the magnetic core (3) such that an air layer (4) is arranged between the power line (2) and the magnetic core (3). [9] Sensor (1) according to one of the preceding claims, wherein the sensor (1) has a further magnetic core (3) which at least partially encloses the power line (2). [10] Circuit arrangement comprising a converter for converting electrical voltages and a sensor (1) according to one of the preceding claims.

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