WO2021112457A1

WO2021112457A1 - Current-measuring assembly

Info

Publication number: WO2021112457A1
Application number: PCT/KR2020/016340
Authority: WO
Inventors: René SANDER; Stephan Werker; Magnus Böh
Original assignee: Hanon Systems
Priority date: 2019-12-04
Filing date: 2020-11-19
Publication date: 2021-06-10
Also published as: DE102019132963A1; DE102019132963B4

Abstract

It is the object of the invention, which relates to a current-measuring assembly, to specify a solution for a current-measuring arrangement, enabling a simple and accurate measurement of a current I in a first conductor (3) or conductor track arranged on a circuit board (1) with little technical effort. To solve this problem, provision is made that a first helical coil (6) and a second helical coil (7) are arranged level on a plane of a circuit board (1) and that the current-carrying first conductor (3) is arranged between the two helical coils (6, 7).

Description

CURRENT-MEASURING ASSEMBLY

The invention relates to a current-measuring assembly, having a current-carrying conductor, a coil and a measuring and evaluation circuit connected to the coil.

One method known from the prior art for non-contact current measurement in a conductor is an inductive measurement. In this case, the effect is used that a current I in a conductor, such as a wire, which changes in amplitude over time, generates a magnetic field around this conductor that also changes over time. This magnetic field can, for example, penetrate a measuring coil arranged around the conductor or next to the conductor and thus induce a current in this measuring coil. This induced current can be measured using a suitable measuring and evaluation circuit. At a known ratio between the current I flowing in the conductor and the current induced in the measuring coil, the current I in the conductor can be determined in this way.

This allows a non-contact measuring data acquisition without a galvanic coupling, which is technically necessary in many cases. In addition, the use of a line-breaking element for current measurement, such as a shunt resistor or a current measuring resistor, is avoided.

With such a current measurement with measuring elements on a circuit board, according to the prior art, the conductor in which the current I is to be determined is guided at an angle such as, for example, a right angle or at least approximately at such an angle, through the plane of the circuit board. Deviations from such a right angle of up to 45 degrees are possible and can be taken into account during calibration or during the measurement itself.

A ring core made of a magnetically conductive material is arranged around this conductor, which penetrates the circuit board. The magnetic field forming around the current-carrying conductor is concentrated by this ring core. If a measuring coil is arranged around this ring core and its current is evaluated by means of a measuring and evaluation circuit, the current I flowing in the conductor can be determined in such a way. The signal generated in this measuring coil is amplified and evaluated using conventional methods known from the prior art.

An example of such a current measurement from the prior art is shown in “Elektrotechnik fur Gebaudetechnik und Maschinenbau [English: Electrical engineering for building technology and mechanical engineering]” by Boker, Andreas; Paerschke, Hartmuth and Boggasch, Ekkehard; ISBN 978-3-658-20971-1; pp. 374 (including Figure 5.12).

A disadvantage of this prior art is that such a current measurement can be done only at a conductor running through the circuit board, for example, nearly vertically. A measurement of a current in a conductor or a conducting path which runs in a plane on the circuit board cannot be done in this way. For a measurement of a current I in a conductor arranged on the circuit board, said conductor would have to be interrupted according to the prior art and the interruption would have to be closed with a conductor, such as a wire, running through the circuit board nearly vertically at least in one section.

Thus, there is a need to improve the solutions known from the prior art for the non-contact and uninterrupted measurement of a current in a conductor by means of a current-measuring assembly.

The object of the invention is to provide a current-measuring assembly enabling a simple and accurate measurement of a current I in a conductor or a conductor track arranged on a circuit board with little technical effort. In addition, the solution should be inexpensive and easy to manufacture.

The object is achieved by an arrangement with the features according to Claim 1 of the independent claims. Further developments are specified in the dependent claims.

For measuring a current I in a current-carrying conductor or conductor track provision is made to arrange one or several helical coils directly next to the current-carrying conductor or conductor track running on the circuit board. In this case, it is possible that the current-carrying conductor or conductor track is arranged in the same plane or layer, or in a different plane or layer on the circuit board.

Such helical coils are arranged level in one plane or layer of the circuit board, wherein usual methods for generating conductor tracks or conducting paths are used for their generation.

Provision is made to arrange one, two or more helical coils level in such a way and, for example, in the same plane of a circuit board that a first helical coil on a first side is arranged next to the current-carrying conductor or conductor track and a second helical coil is arranged on a second side, which is opposite to the first side, next to the current-carrying conductor or conductor track. In this case, the distance between the current-carrying conductor or conductor track and the first helical coil, and the current-carrying conductor or conductor track and the second helical coil is preferably the same.

With such an arrangement of two helical coils on both sides of the current-carrying conductor or conductor track, the coils are connected to each other in series and to a measuring and evaluation circuit. Such a measuring and evaluation circuit can include an amplifier for amplifying the measurement signal which is generated by the two helical coils. Such a measurement signal is generated by the magnetic field surrounding the current-carrying conductor or conductor track, with said magnetic field penetrating the two helical coils and inducing a current in these coils. This current is amplified and measured, for example, in the measuring and evaluation circuit, it being possible for a digital measurement result to be generated and output.

With such an arrangement of two helical coils on both sides of the current-carrying conductor or conductor track the sense of winding of the two helical coils is oriented in such a way that the measurement signals of both coils are summed.

Provision is also made to arrange several helical coils in several planes or layers of the circuit board. Also in this case, said several helical coils are connected to each other in such a way on both sides of the current-carrying conductor or conductor track taking into account the sense of winding so that the measurement signals of said coils are summed.

Provision is made to produce the helical coils on the circuit board with conventional techniques for arranging conductors or conductor tracks on a circuit board, and in the same process step with the generation of the conductor tracks. This also applies to circuit boards with several planes or layers.

Provision is also made, but not absolutely necessary, that a core made of a magnetically conductive material is used. In doing so, portions of the magnetic field surrounding the current-carrying conductor or conductor track are focused and oriented, and guided in such a way by, for example, two helical coils. Such a core can be, for example, a core made of a ferromagnetic material and composed of two pressed parts assembled in a U-shape.

Such a core can also be a core consisting of a flexible material such as a plastic tube or a round solid material, the material of the core or the plastic having magnetic properties, for example, by introducing a ferrite powder during its production.

The invention thus enables the measurement of currents in a conductor arranged on a circuit board without additional coil material or jumpers which must run through the circuit board in a level arrangement of the helical coils.

Thanks to the arrangement according to the invention of two helical coils on both sides of the current-carrying conductor or conductor track, the impact of interferences from magnetic fields of other current-carrying conductors is substantially reduced and the measurement is thus carried out more accurately and more robust.

The electromagnetic compatibility (EMC) is improved or the impact of unwanted electrical or electromagnetic interferences, which are caused by neighboring assemblies or devices, with the current measurement is reduced.

The solution according to the invention is thus a space-saving solution that is provided also for use in vehicle engineering. Thus, requirements for high measurement accuracy or small measurement errors, for example in the area of controlling an electric refrigerant compressor in a vehicle, can be met.

Due to the robust and accurate current measurement, an improved accuracy in the determination of the range is obtained, for example, when the invention is used in electric vehicles, in which an electricity consumption estimation is carried out.

Further details, features and advantages of configurations of the invention result from the following description of exemplary embodiments with reference to the accompanying drawings.

Fig. 1 shows a current-measuring assembly in accordance with the prior art,

Fig. 2 shows a current-measuring assembly according to the invention in a plan view on a circuit board,

Fig. 3 shows the current-measuring assembly according to the invention from Figure 2 in a side view and sectional view, respectively,

Fig. 4 shows a further current-measuring assembly according to the invention with a flexible core,

Fig. 5 shows an illustration of the mode of operation of the current-measuring assembly according to the invention,

Fig. 6 shows a further development of the current-measuring assembly according to the invention in which several helical coils are arranged in several planes or layers of a circuit board, and

Fig. 7 shows a further illustration of the mode of operation of the current-measuring assembly according to the invention and its robustness with respect to interferences.

A current-measuring assembly according to the prior art is illustrated in Figure 1. The left part of Figure 1 shows a side view and a sectional view along the section line AA, respectively, and the right part of Figure 1 shows a plan view of the same area of the circuit board 1 for better understanding.

On a circuit board 1 on which, for example, components of an inverter for controlling a motor in an electric refrigerant compressor may be arranged, a core 2 or a ring core made of a solid magnetic material is arranged. In the inner section of the core 2, a first conductor 3 is guided through the circuit board 1, wherein the first conductor 3 is guided through the circuit board 1 at a right angle or at an angle different from this angle. For measuring the current I flowing through the first conductor 3, a measuring winding 4 is arranged, which is connected to a corresponding measuring and evaluation circuit 8, not illustrated in Figure 1. This measuring and evaluation circuit 8 can also be arranged on the circuit board 1, for example.

The measuring and evaluation circuit 8 amplifies, for example, the measurement signal provided by the measuring winding 4, such as a current I, and generates a measurement value from this measurement signal, which measurement value is output by the measuring and evaluation circuit 8, for example, in a digital form as measurement values. This measuring process can take place continuously, so that measurement values are continuously generated which are in a known ratio to the current I in the first conductor 3. The current I in the first conductor 3 can thus be determined by means of this known ratio.

Figure 2 illustrates a current-measuring assembly 5 according to the invention in a plan view on a circuit board 1. Figure 2 shows a small section of the circuit board 1, which can have one or more planes or layers. A first conductor 3 or conductor track, illustrated in Figure 2 only as a section, is arranged on the surface of the circuit board 1 or in a plane or layer of the circuit board 1.

A current I flows through this conductor 3, which current is to be measured by means of the current-measuring assembly 5 according to the invention. For this purpose, a first helical coil 6 is arranged on the surface of the circuit board 1 on a first side next to the conductor 3. Furthermore, a second helical coil 7 is arranged on the surface of the circuit board 1 on a second side next to the conductor 3, the second side being opposite the first side. The

helical coils

6 and 7 are designed level or flat on the surface or within a plane or layer of the circuit board 1, wherein terminals for electrically connecting the

helical coils

6 and 7 to each other as well as to a measuring and evaluation circuit 8 can be designed in a different plane. The

helical coils

6 and 7 can be arranged in any plane or layer of the circuit board 1.

The

helical coils

6 and 7 are designed with a specific winding sense so that the currents induced by the action of the magnetic field of the first conductor 3 do not cancel each other, but are generated in the same direction of current flow. The

helical coils

6 and 7 are connected to each other in series. In addition, one end of each of the

helical coils

6 and 7 is electrically connected to a measuring and evaluation circuit 8.

For this purpose, corresponding through-connections 9 are provided in order to relocate the current path for the measurement signal generated by means of the

helical coils

6 and 7, for example at least in sections, to an adjacent plane or layer of the circuit board 1. An exemplary design of this type of the current path for the measurement signal along two planes of the circuit board 1 is illustrated in Figure 2.

Relocating the current path takes place in particular in sections on the circuit board 1 in which the lines would cross.

A core 2 or ring core made of a magnetic material is arranged to bundle or concentrate the magnetic field that changes over time. The ring-shaped core 2 penetrates the circuit board 1, the first helical coil 6 and also the second helical coil 7 in their respective inner sections or center. In other words, the

helical coils

6 and 7 surround the core 2 at two different and spaced apart locations.

The core 2 may, for example, consist of two fixed halves and have an oval, a circular or a rectangular shape in the assembled state.

Figure 3 depicts the current-measuring assembly 5 according to the invention from Figure 2 in a side view or sectional illustration on a circuit board 1. The illustration in Figure 3 corresponds to a section along the section line BB in Figure 2.

Figure 3 likewise shows only a section of the circuit board 1, which can have one or more planes or layers. The first conductor 3 or conductor track, as well illustrated only as a section in Figure 3, is arranged on the bottom of the circuit board 1.

In the example of Figure 3, a first helical coil 6 is arranged on the surface of the circuit board 1 offset on a first side next to the first conductor 3. Furthermore, a second helical coil 7 is arranged on the surface of the circuit board 1 on a second side offset next to the first conductor 3, the second side being opposite the first side. The

helical coils

6 and 7 can also be arranged in a different plane or layer of the circuit board, for example on the bottom of the circuit board 1 in the plane in which also the first conductor 3 is arranged.

Alternatively, the first conductor 3 carrying the current I to be measured can also be arranged in the same plane, that is to say on the surface of the circuit board 1, as the first helical coil 6 and the second helical coil 7.

In the example of Figure 3, a fixed core 2 made of a magnetically conductive material (μr ≤ 10,000) is also provided, by means of which the quality of the measured signal is improved. In the example of Figure 3, the core 2 consists of two U-shaped halves assembled to form a rectangular shape.

The interconnection of the

helical coils

6 and 7 corresponds to the manner already explained in the context of Figure 2. Figure 3 is only intended to be a schematic illustration and shows neither the through-connections 9 nor the measuring and evaluation circuit 8 or its connection to the

helical coils

6 and 7.

Figure 4 shows another current-measuring assembly 5 according to the invention with a flexible core 2. The illustration of Figure 4 shows the elements of the current-measuring assembly 5 already described in the context of Figure 3.

In contrast to Figure 3, the core 2 in Figure 4 is designed of a flexible material such as a plastic, which is provided in a magnetically conductive form, for example by introducing a ferrite powder during its production. This flexible core 2 can be formed, for example, from a deformable or bendable plastic tube or a round solid material. The core 2 is guided through the

helical coils

6 and 7 through corresponding openings (not illustrated) in the circuit board 1 and glued or welded at a seam 10.

Thus, the core 2 forms a circular or oval shape. One advantage of such a flexible core 2 made of a magnetic plastic consists in its lower weight and its robustness, for example when vibrations occur in a vehicle and especially in an electric refrigerant compressor in a vehicle.

Figure 5 shows an illustration of the mode of operation of the current-measuring assembly 5 according to the invention which is arranged on a circuit board 1. As is known from the prior art, the first conductor 3 carrying a changing current I generates a first magnetic field 11 which surrounds the first conductor 3. This time-varying first magnetic field 11 is illustrated in Figure 5 as a snapshot. As can be seen, the field lines of the magnetic field 11 penetrate both the first helical coil 6 and the second helical coil 7 and thus induce the measurement signal in the form of a current in the

helical coils

6 and 7.

Figure 5 shows the first magnetic field 11 without the impact of a core 2 resulting in a lower magnetic coupling for the

helical coils

6 and 7. If, for example, a flexible core 2 is used, an improved magnetic coupling for the

helical coils

6 and 7 is achieved. This improved magnetic coupling results in a measurement signal of a larger amplitude and a better evaluability of the measurement signal, through an improved signal-to-noise ratio. In addition, the current measurement is therefore more robust to interferences.

Figure 6 shows a further development of the current-measuring assembly 5 according to the invention, in which several first helical coils 6 and several second helical coils 7 are arranged in several planes or layers of a circuit board 1. Here again a snapshot of the first magnetic field 11 is shown, which is generated by a first conductor 3 carrying a changing current.

By using several first helical coils 6 and several second helical coils 7 in different layers of the circuit board 1, wherein the

helical coils

6 and 7, taking into account the corresponding winding sense, are connected together in such a way that the measurement signals of the individual

helical coils

6 and 7 are summed, an improved sum measurement signal with a larger amplitude and a further improved robustness to interferences is generated. Such an interconnection of the first helical coils 6 with each other corresponds to an increase in the number of windings of the resulting first helical coil 6. The same also applies to the second helical coils 7.

In this example also no core 2 is illustrated, which of course can be used also in this design and improves the quality of the current measurement further.

Figure 7 shows a further illustration of the mode of operation of the current-measuring assembly 5 according to the invention and its robustness to interferences.

In the left-hand part of the circuit board 1 shown in part, a current-measuring assembly 5 according to the invention already known from the preceding Figures 3 to 5 is illustrated with a first conductor 3 or conductor track. In the right-hand section of the circuit board 1, a second conductor 13 or conductor track is arranged. A time-varying current I2 flows through this second conductor 13 also, wherein an also time-varying second magnetic field 12 is formed around the second conductor 13. This second magnetic field 12 penetrates the first helical coil 6 and the second helical coil 7 and represents an interference for the current-measuring assembly according to the invention, which affects the measurement signal to be generated and thus the current measurement. The time-varying

magnetic fields

11 and 12 are illustrated in Figure 7 at specific time in a snapshot.

As can be seen, the first magnetic field 11 penetrates the first helical coil 6 from bottom to top, while the first magnetic field 11 penetrates the second helical coil 7 from top to bottom. Thus, the directions of penetration of the

helical coils

6 and 7 are different. By connecting the

helical coils

6 and 7 in series, taking into account the winding sense or the winding direction of the

helical coils

6 and 7, a measurement signal is formed as the sum of the individual currents induced in the

helical coils

6 and 7.

In the example of Figure 7, the second magnetic field 12 generated by the second conductor 13 penetrates the

helical coils

6 and 7 from top to bottom in each case. Thus, the directions of penetration of the

helical coils

6 and 7 are equal. As a result of this equality, the interference signal, caused by the second magnetic field 12, is not formed as a sum of two individual currents induced in the

helical coils

6 and 7. In this case, a subtraction of the currents induced in the

helical coils

6 and 7 occurs, wherein this interference signal is drastically reduced.

Thus, the current measurement according to the invention is very robust to interferences from magnetic fields of adjacent, other current-carrying conductors such as the second conductor 13, which form a magnetic field.

This solution according to the invention can also be used in particular in multilayer circuit boards 1. In most cases, the inner layers of a multilayer circuit board 1 are provided with line structures which do not achieve the fineness of the external structures of the multilayer circuit board 1.

For example, a circuit board 1 is designed with structures in a range up to about 100 μm in the inner layers while structures in the range up to about 30 μm can be designed on the outer surfaces of the circuit board 1.

Therefore, these inner layers with the coarser structures are often utilized for current-carrying first conductors 3 or conductor tracks, which have correspondingly large dimensions due to correspondingly large currents. In accordance with the prior art, it is correspondingly complex to interrupt said first conductors 3 or conductor tracks located in the interior of the circuit board 1 for a current measurement.

In this case, the present invention provides a solution for interruption-free, non-contact current measurement, as the current-carrying first conductor 3 can be arranged in any plane or layer of the multilayer circuit board 1, and the

helical coils

6 and 7 required for current measurement can be arranged in any other plane or layer.

In principle, the

helical coils

6 and 7 required for current measurement can also be arranged in different planes or layers of the multilayer circuit board 1. Necessary is only a corresponding interconnection of the

helical coils

6 and 7 with each other and with a measuring and evaluation circuit 8, as already described above.

Claims

Current-measuring assembly (5), having a current-carrying, first conductor (3), a coil and a measuring and evaluation circuit (8) connected to the coil, characterised in that a first helical coil (6) and a second helical coil (7) are arranged level in one plane of a circuit board (1) and that the current-carrying, first conductor (3) is arranged between both helical coils (6, 7).
Current-measuring assembly (5) in accordance with Claim 1, characterised in that the helical coils (6, 7) and the conductor (3) are arranged in different planes of the circuit board (1).
Current-measuring assembly (5) in accordance with Claim 1 or 2, characterised in that the helical coils (6, 7) are arranged connected to each other in series and connected to a measuring and evaluation circuit (8).
Current-measuring assembly (5) in accordance with one of Claims 1 to 3, characterised in that several first helical coils (6) and several second helical coils (7) are arranged in different layers of the circuit board (1).
Current-measuring assembly (5) in accordance with one of Claims 1 to 4, characterised in that a ring-shaped core (2) made from a magnetic material is arranged on the circuit board (1) in such a way that this (core) penetrates both the first helical coil (6) and the second helical coil (7) in each of their inner sections and also the circuit board (1) itself.
Current-measuring assembly (5) in accordance with one of Claims 1 to 5, characterised in that the core (2) is fixed and has at least two parts (2) and consists of a ferromagnetic material.
Current-measuring assembly (5) in accordance with one of Claims 1 to 5, characterised in that the core (2) is a one-part core (2), that the core (2) consists of a flexible magnetic material and has a connection on one seam (10).
Current-measuring assembly (5) in accordance with one of Claims 1 to 7, characterised in that the core (2) has an adhesive bond or a weld on one seam (10).
Current-measuring assembly (5) in accordance with one of Claims 1 to 8, characterised in that through-connections (9) are arranged in the series circuit of the helical coils (6, 7).
Current-measuring assembly (5) in accordance with one of Claims 1 to 9, characterised in that the current-measuring assembly (5) is arranged in an electric refrigerant compressor in a vehicle.