EMC filter to suppress interference signals

Abstract

EMC filter (1) for suppressing interference signals, which has at least one choke (4, 5), at least one core (11) and several capacitors (6, 7, 8, 9), characterized in that in an EMC filter module (10) at least one core (11) of a choke (4, 5) with a winding (16) is arranged on a first carrier board (14), that at least one of the capacitors (6, 8, 9) is arranged on the first carrier board (14), that the first carrier board (14) has at least two contact means (17), that the first carrier board (14) of the EMC filter module (10) is arranged with its contact means (17) on a main board (12) of a converter (2) and is electrically connected thereto, that a second carrier board (15) is arranged in the EMC filter module (10), and that the core (11) is arranged between the first carrier board (14) and the second carrier board (15), wherein a part of the capacitors (6, 8,9) are arranged on the first carrier board (14) and at least one capacitor (7) is arranged on the second carrier board (15).,

Description

[0001] The invention relates to an EMC filter for suppressing interference signals, which has at least one choke, at least one core and several capacitors.

[0002] In electronic assemblies in which switching operations are performed with electrical voltages or currents, these switching operations generate interference due to the resulting electrical pulses, coupled with the emission of noise signals. This interference can propagate both via wires and through free space, i.e., wirelessly as an electromagnetic wave.

[0003] The ability of a technical device not to interfere with other devices through unwanted electrical or electromagnetic effects or to be interfered with by other devices is called electromagnetic compatibility (EMC).

[0004] To prevent or minimize the spread of such interference, it is known from the state of the art to equip these modules with a filter unit, a so-called EMC filter, EMC filter, or line filter. It is also known to take measures to shield or shield the electronic modules to prevent excessively high amplitudes of the interference signals from affecting the proper functioning of other electronic modules or devices.

[0005] The magnitudes of such interference signals, which must be complied with by a device placed on the market, are specified in the EMC standards applicable to that device and are described in terms of limit values and minimum requirements to be complied with.

[0006] Well-known examples include the so-called ECE regulations, which comprise a catalog of international agreements for uniform technical specifications for motor vehicles and for parts and equipment of motor vehicles. ECE R10, for example, deals with the area of radio interference suppression, which must be observed for future developments and will result in a further reduction in permissible interference emissions.

[0007] Electromagnetic interference is also generated when electrical converters (inverters) drive electric motors and thus switch large currents. Such converters are used, for example, to drive a motor in a vehicle's air conditioning compressor.

[0008] Due to the increasing EMC requirements for vehicles such as hybrid and electric vehicles, there is a need to equip electrical consumers in these vehicles with an EMC filter in order to ensure compliance with the specified electromagnetic limits even in assemblies such as an electric air conditioning compressor.

[0009] A well-known solution for suppressing interference from electrical or electronic components is the use of a passive EMC filter. Such passive EMC filters are typically implemented using passive components such as capacitors, coils, and resistors, which are interconnected in a known, suitable manner to create the desired filtering effect.

[0010] When it comes to the type of interference to be filtered by an EMC filter, a distinction is made between so-called common-mode and differential-mode interference. In practice, the interference spectrum to be filtered by the EMC filter consists of the sum of both overlapping interference components.

[0011] The type, structure and especially the voltage level of, for example, an inverter for an electric refrigerant compressor determine which of the two interference components predominates and which interference component therefore needs to be filtered more intensively.

[0012] In high-voltage inverters, which operate with voltages between 300 V and 800 V, common-mode interference is the main interference component.

[0013] The field of application of the present invention is not limited to the prevention or minimization of common-mode interference or differential-mode interference. Thus, the following exemplary embodiment relating to only one type of interference should not be viewed as a limitation, as it is always possible for a person skilled in the art to adapt the embodiment to the other type of interference by making appropriate, professional modifications. This can be achieved, for example, by replacing a common-mode choke with a differential-mode choke.

[0014] It is known from the prior art to filter, for example, differential mode interference by using so-called chokes in combination with capacitors in a passive EMC filter. For this purpose, a choke L1 and L2 are inserted in each supply line of the converter HV+ and HV-, and corresponding capacitors C1 and C2 are arranged between the supply lines HV+ and HV-, before and after the chokes L1 and L2. In addition, a third capacitor C3, facing the converter, is arranged after the choke L2 between the HV- line and a ground potential, and a fourth capacitor C4, facing the converter, is arranged after the choke L1 between the HV+ line and the ground potential in the passive EMC filter. In a practical implementation, each capacitor C1 to C4 can be composed of several sub-capacitors, i.e. several capacitor components.

[0015] Chokes are coils or inductors used to limit currents in electrical lines, temporarily store energy in the form of their magnetic field, for impedance conversion, or for filtering. Such chokes are often inserted into a line of an electrical assembly. To increase their inductive resistance, also known as reactance, chokes often contain a soft magnetic core. Ferromagnetic materials, which are easily magnetized in a magnetic field, are known to be used as soft magnetic materials.

[0016] The chokes L1 and L2 arranged in the supply lines HV+ and HV- of the inverter are passed through by the maximum possible input current of the inverter and must therefore be dimensioned accordingly for this current load.

[0017] This interference-superimposed input current creates a magnetic field in the chokes L1 and L2. When using so-called common-mode chokes, the magnetic fields of the input currents cancel each other out in the common core due to the opposing winding sense of the two choke windings, which are arranged on a common core.

[0018] US 2016 / 0 336 846 A1 discloses an inductive component mounted on a printed circuit board and comprising a substantially flat carrier and a choke, wherein the choke is mounted on an upper side of the carrier and comprises a core and at least two coils wound around the core. The wires of the at least two coils have end segments that are guided through the carrier and terminate on a lower side of the carrier opposite the upper side of the carrier. The carrier comprises recesses for guiding the end segments through the carrier and closures for fastening the end segments of the wires in the recesses. This solution provides a compact unit comprising a carrier and a choke, which can be arranged on an inverter board in the manner customary in the prior art.

[0019] JP 2010 - 284 027 A discloses a power supply arrangement that provides multiple partial voltages. The arrangement comprises several ring-shaped transformer cores arranged adjacent to one another on a common circuit board. The transformer cores have a common primary winding connected to a control circuit. The transformers each have their own secondary winding, each connected to an output driver circuit for providing an output voltage. This prior art solution is also suitable for arrangement on an inverter circuit board.

[0020] DE 10 2014 101 403 A1 discloses a lighting device comprising at least one semiconductor illuminant and a housing in which the at least one semiconductor illuminant is arranged. The semiconductor illuminant is connected to the housing via a form-fit connection.

[0021] EP 3 229 564 A1 discloses a printed circuit board assembly with at least two printed circuit boards aligned perpendicular to one another. A first printed circuit board has first contact surfaces on one side at a printed circuit board edge, while a second printed circuit board has second contact surfaces on one side. The second contact surfaces of the second printed circuit board are arranged perpendicularly to the first contact surfaces of the first printed circuit board. The first contact surfaces are electrically connected to the second contact surfaces by means of solder.

[0022] DE 100 48 290 A1 describes an inductive sensor. A carrier board carrying a sensor coil is rigidly mechanically and electrically connected to the board via at least two solder joints.

[0023] A disadvantage of such passive EMC filters is that they require a large amount of space, for example, on a main board, to filter high interference amplitudes or to maintain correspondingly low limit values. Such a main board, also known as a converter board or inverter board, is required to accommodate the components necessary to control the operation of the converter.

[0024] In addition, different customers request inverter boards that must meet different EMC specifications and different installation space requirements. Therefore, it is often necessary to adapt the layout of the inverter boards to the given specifications, which is time-consuming and costly.

[0025] Due to these described disadvantages, there is a need for a suitable solution that limits the variety of necessary variations of the inverter boards.

[0026] The object of the invention is to provide an EMC filter which helps to reduce the reworking effort of the inverter boards, enables a limitation of the installation space and contributes to the reduction of the development and manufacturing costs.

[0027] The problem is solved by an object having the features according to claim 1 of the independent patent claims. Further developments are specified in the dependent patent claims 2 to 10.

[0028] In a typical circuit arrangement of a passive EMC filter, chokes are arranged in the HV+ and HV- supply lines of a converter. Additionally, capacitors or capacitances are provided between the HV+ and HV- supply lines, before and after the chokes, and between a ground potential and the HV+ and HV- supply lines.

[0029] Depending on whether the passive EMC filter is primarily intended to suppress common-mode interference or differential-mode interference, the coil windings are either mounted on a common core (common-mode choke) or mounted separately on different cores (differential-mode choke).

[0030] The invention provides for accommodating a common-mode choke or a differential-mode choke on one or between two separate carrier boards. Separate in this case means that the carrier board is not part of the mainboard or inverter board, but can be connected to it. In a design with two carrier boards, the common-mode choke or the differential-mode choke is arranged between the two parallel carrier boards.

[0031] Single-layer or multi-layer printed circuit boards are used as such carrier boards.

[0032] It is also intended to arrange additional components on the first or second carrier board. Such components are typically the capacitors required for an EMC filter circuit.

[0033] Furthermore, it is provided that the first and / or second carrier board is / are equipped with contact means via which at least one of the carrier boards can be electrically connected to the main board or inverter board of an inverter. This is necessary to electrically connect the corresponding input and output terminals of the EMC filter to the inverter circuit on the inverter board.

[0034] In addition, the contact elements can be used to mechanically attach the carrier boards to the mainboard. This eliminates the need for additional mechanical fastening of the carrier boards.

[0035] As contact means, lugs or tabs can be provided on the first and / or second carrier board, which are inserted into recesses in the main board suitable for receiving these lugs or tabs. In this case, a connection that is both electrically conductive and mechanically stable can be achieved, for example, by a solder joint at the points where the lugs or tabs are inserted into the recesses. For this purpose, the lugs or tabs of the carrier boards have, for example, at least one copper coating on one side. In addition, corresponding conductor tracks are provided next to or around the recesses in the main board.

[0036] Such a solder connection between the contact means designed as noses or tabs and the conductor tracks on the main board can be created, for example, by means of wave soldering or flow soldering.

[0037] Alternatively, an electrically conductive connection between the contact means of the carrier boards and the main board can also be established via solder lugs, plug contacts, clamp contacts or screw contacts.

[0038] In order to achieve a compact, space-saving design of the main board, it is intended to connect the first or the first and second carrier boards to the main board at right angles to the main board.

[0039] The invention therefore provides for the EMC filter to be implemented as a separate EMC filter module, which is electrically and mechanically connected to the mainboard. This EMC filter module comprises, for example, a common-mode choke arranged between the first and second carrier boards, as well as the additional capacitors required for wiring the EMC filter module. In an alternative embodiment of the EMC filter module, two differential-mode chokes are provided between the first and second carrier boards, as well as the additional capacitors required for wiring this EMC filter module.

[0040] This modular design of the EMC filter in the form of an EMC filter module allows for the combination of a pre-developed EMC filter module with a newly developed motherboard. This allows for the use of an existing range of pre-developed EMC filter modules for the diverse requirements of different customers when developing new motherboards. The EMC filter modules are designed to have different parameters for attenuating EMC interference.

[0041] An EMC filter module can be adapted to meet changing customer requirements without changing the main board.

[0042] It is also intended to arrange a connecting means between the first and second carrier boards. The purpose of this connecting means is, on the one hand, to mechanically connect the first carrier board to the second carrier board and to fix the carrier boards in a position parallel to one another. On the other hand, the purpose of the connecting means is to mechanically fix the core of the common-mode choke between the carrier boards. A third purpose of the connecting means, when using a common-mode choke, is to separate the two windings applied to a common core. This separation is intended to electrically insulate both windings from one another. This prevents both an electrical short circuit between the two windings and the jumping of a spark between the two windings.

[0043] The intended connecting means is a web or plate made of a non-conductive material, such as a plastic or a printed circuit board material without a copper coating.

[0044] In the case of the arrangement of a common-mode choke between the carrier boards, one connecting means is provided and in the case of the arrangement of two differential-mode chokes, two connecting means are provided, since each core must be fixed by means of a connecting means.

[0045] Further details, features, and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. They show: Fig. 1: an exemplary circuit arrangement of a passive EMC filter according to the state of the art using the example of an EMC filter circuit with a common mode choke, Fig. 2: a schematic diagram of a structural unit for controlling an inverter consisting of a main board and an EMC filter module according to the invention and Fig. 3: a perspective view of an exemplary embodiment of an EMC filter module according to the invention with two carrier boards and a common mode choke.

[0046] The Fig. 1 shows an exemplary circuit arrangement of a passive EMC filter 1 according to the prior art, which is connected to a converter 2. The EMC filter circuit 1, designed as a passive filter, has an input 3, to which a voltage of 400 V can be applied, for example, and comprises the chokes L1 4 and L2 5 arranged in the supply lines HV+ and HV-, which, in the case of a common-mode choke, are implemented by the windings L1 4 and L2 5 arranged on a common core.

[0047] While the first capacitor 6, designated C1, is located between the lines HV+ and HV- directly at the input of the passive EMC filter circuit 1 and in front of the chokes L1 4 and L2 5, the second capacitor 7, designated C2, is located behind the chokes L1 4 and L2 5 at the output of the EMC filter circuit 1 and thus at the input of the converter 2.

[0048] A third capacitor 8, labeled C3, is arranged between the HV- line and a ground potential. A fourth capacitor 9, labeled C4, is arranged between the HV+ line and the ground potential.

[0049] As is usual in the prior art, it is provided that the converter 2 generates the electrical control signals required to operate an electric motor (not shown), which drives, for example, a refrigerant compressor.

[0050] This known circuit arrangement is also used by the EMC filter module 10 according to the invention, which is designed in a modular design according to Fig. 2. In an alternative, two cores 11 of two differential mode chokes can be arranged in place of a common core 11 or choke core of a common mode choke.

[0051] In the Fig. 2 shows a schematic diagram of a structural unit for controlling an electric drive motor (not shown) by the converter 2, which consists of a main board 12 for the converter 2 and an EMC filter module 10 according to the invention. The components of the converter 2, which are necessary, for example, for controlling the operation of a motor in an air conditioning compressor, are mounted on the main board 12, which components are shown in the Fig. 2 are not explicitly shown.

[0052] The main board 12 can be designed as a single-layer or multi-layer printed circuit board in the usual way. In the example, the main board 12 has several copper layers 13, which provide the necessary electrical connections for the components of the converter 2 in the form of conductor tracks.

[0053] In contrast to the usual state of the art, the components required for the EMC filter 1 are not arranged on the main board 12, but on an EMC filter module 10 according to the invention.

[0054] The EMC filter module 10 comprises at least a first carrier board 14, which can be designed, for example, as a single-layer or multi-layer printed circuit board. A core 11, for example, for a common-mode choke, is arranged on this first carrier board 14. The windings 16a of the first choke L1 4 and the windings 16b of the second choke L2 5 are arranged on this core 11. Fig. In Figure 2, this arrangement consisting of a core 11 and a winding 16 is shown only as an example with a single winding 16, instead of both windings 16a and 16b. This illustration does not limit the invention to this embodiment.

[0055] Furthermore, it is provided that the capacitors C1 6 to C4 9 required for the EMC filter circuit 1 are arranged on the first carrier board 14. Alternatively, only some of these capacitors C1 6 to C4 9 may be required and / or arranged on the first carrier board 14.

[0056] It is provided that the first carrier board 14 has contact means 17, with which an electrical connection to the conductor tracks 13 of the main board 12 is established. In one embodiment, these contact means 17 can be designed in the form of a nose or tab that protrudes from the carrier board 14.

[0057] To accommodate and electrically contact the EMC filter module 10 in or with the main board 12, the main board 12 is provided with corresponding recesses into which the nose-shaped or flag-shaped contact means 17 can be inserted. A soldered connection 18 can be provided to establish an electrical connection between a conductor track 13 of the first carrier board 14 and a conductor track 13 of the main board 12. This provides an electrically conductive and mechanically stable connection between the first carrier board 14 of the EMC filter module 10 and the main board 12.

[0058] Alternatively, the contact means 17 can be designed by a person skilled in the art such that an electrically conductive connection is established between the first carrier board 14 and the main board 12 via solder lugs, plug contacts, clamp contacts, or screw contacts. A mechanically stable connection can also be achieved in these cases. Alternatively, additional means for securely attaching the EMC filter module 10 to the main board 12 can be provided in all cases.

[0059] In one embodiment of the EMC filter module 10, two cores 11 can be arranged on the first carrier board 14. This can be the case, for example, with an embodiment of the EMC filter module 10 with two push-pull chokes L1 4 and L2 5.

[0060] In a further embodiment, it is provided to arrange a second carrier board 15, for example, parallel to the first carrier board 14. In this case, for example, the core 11 of a common-mode choke is arranged between the carrier boards 14 and 15.

[0061] The second carrier board 15 also has contact means 17, with which it can be electrically and mechanically contacted or connected to the main board 12, as already known from the above description of the first carrier board 14. Furthermore, capacitors C1 6 to C4 9 of the EMC filter module 10 can also be arranged on the second carrier board 15.

[0062] A connecting means 19 is provided for mechanically connecting the first and second carrier boards 14 and 15. This connecting means 19, which is Fig. 2 by a dash-dash line, is designed, for example, as a web or a plate made of a non-conductive material such as a plastic. The connecting means 19 can be glued, screwed, pressed, clamped, or welded (plastic welding) to the first and second carrier boards 14 and 15, for example, and thus mechanically stabilize the EMC filter module 10.

[0063] In addition to this task of mechanically stabilizing and fixing the first and second carrier plates 14 and 15, the connecting means 19 is provided for receiving and mechanically fixing the core 11 between the carrier plates 14 and 15. For this purpose, the connecting means 19 is designed such that it can be inserted, for example, into the inner diameter of an annular core 11 in a form-fitting manner and then firmly connected to the first and second carrier plates 14 and 15.

[0064] A third function of the connecting means 19, when using a common-mode choke, is to separate the two windings 16a and 16b applied to the common core 11. This separation both prevents an electrical short circuit between the two windings 16a and 16b and prevents a spark from jumping between the two windings 16a and 16b.

[0065] In the event that the EMC filter module 10 is equipped with two cores 11 for two push-pull chokes, one connecting means 19 is used per core 11 in the manner described above. Such an embodiment is not shown in the figures.

[0066] In the Fig. Figure 3 shows a perspective view of an exemplary embodiment of the EMC filter module 10 according to the invention. The EMC filter module 10 is designed with a first and a second carrier board 14 and 15, between which the core 11 of a common-mode choke with a first winding 16a and a second winding 16b is arranged.

[0067] Between the two carrier plates 14 and 15, a connecting means 19 is arranged, which is glued to the carrier plates 14 and 15 and fixes the annular core 11. In the Fig. 3 also shows that a copper layer 13 is applied to the surface of the first carrier board 14. By appropriately structuring this copper layer 13, the electrical connections or conductor tracks required for electrically contacting the components of the EMC filter module 10 can be created. Thus, for example, the capacitors 6, 7, 8, or 9 can be arranged on such a surface of the first carrier board 14. Fig. 3 shows, by way of example, the first capacitor 6 (C1) on the first carrier board 14, which is used in the circuit of the Fig. 1 is arranged on the input side between the input terminals HV+ and HV-. Additional capacitors 7, 8, or 9 can be arranged on the copper layers 13 of the second carrier board 15.

[0068] The first carrier board 14 has two tab-shaped or flag-shaped contact elements 17a and 17b, with which an electrical connection can be established with the main board 12 (not shown). The main board 12 is provided with corresponding rectangular openings into which the contact elements 17a and 17b can be inserted. An electrical connection is established by soldering the copper layer 13 of the first carrier board 14 to a corresponding copper layer 13 or a conductor track 13 of the main board 12.

[0069] The same applies to the contact means 17c and 17d, which are arranged on the second carrier board 15. The contact means 17a and 17b correspond in the Fig. 1 the input terminal designations HV+ Input and HV-Input of the EMC filter module 10. The contact means 17c and 17d correspond in the Fig. 1 the output terminal designations HV+ Output and HV-Output of the EMC filter module 10. List of reference symbols 1 EMC filter (EMC filter circuit) 2 inverters 3 Input (HV+ / HV-) 4 first choke L1, winding L1 5 second choke L2, winding L2 6 first capacitor C1, first capacity 7 second capacitor C2, second capacitance 8 third capacitor C3, third capacity 9 fourth capacitor C4, fourth capacity 10 EMC filter module 11 core, choke core 12 Inverter main board 13 copper layers, conductor track, conductor line 14 first carrier board 15 second carrier board 16, 16a, 16b winding 17, 17a, 17b, 17c, 17d contact means 18 Solder connection 19 connecting devices

Claims

[1] EMC filter (1) for suppressing interference signals, which has at least one choke (4, 5), at least one core (11) and several capacitors (6, 7, 8, 9), characterized bythat in an EMC filter module (10) at least one core (11) of a choke (4, 5) with a winding (16) is arranged on a first carrier board (14), that at least one of the capacitors (6, 8, 9) is arranged on the first carrier board (14), that the first carrier board (14) has at least two contact means (17), that the first carrier board (14) of the EMC filter module (10) is arranged with its contact means (17) on a main board (12) of a converter (2) and is electrically connected thereto, that a second carrier board (15) is arranged in the EMC filter module (10), and that the core (11) is arranged between the first carrier board (14) and the second carrier board (15), wherein some of the capacitors (6, 8, 9) are arranged on the first carrier board (14) and at least one capacitor (7) is arranged on the second carrier board (15). [2] EMC filter (1) according to claim 1, characterized bythat the second carrier board (15) is arranged parallel to the first carrier board (14). [3] EMC filter (1) according to claim 1 or 2, characterized by that a connecting means (19) is arranged between the first carrier board (14) and the second carrier board (15) and that the core (11) of the choke (4, 5) is arranged between the first and the second carrier board (14, 15) and on the connecting means (19). [4] EMC filter (1) according to one of claims 1 to 3, characterized by that a copper layer (13) forming conductor tracks is arranged at least partially on a surface of the first carrier board (14) and / or on a surface of the second carrier board (15). [5] EMC filter (1) according to one of claims 1 to 4, characterized by that capacitors (6, 7, 8, 9) are arranged on the copper layer (13) forming the conductor tracks of the first carrier board (14) and / or the second carrier board (15). [6] EMC filter (1) according to one of claims 1 to 5, characterized by that lugs or flags are arranged on the first and / or the second carrier board (14, 15) or soldering flags or plug contacts or clamp contacts or screw contacts as contact means (17). [7] EMC filter (1) according to one of claims 1 to 6, characterized by that a core (11) of a common-mode choke is arranged between the first and the second carrier board (14, 15) or two cores (11) of two differential-mode chokes are arranged. [8] EMC filter (1) according to one of claims 4 to 7, characterized by that a solder connection (18) establishing an electrical connection is arranged at least between a copper layer (13) forming conductor tracks on the first carrier board (14) and a copper layer (13) forming conductor tracks on the main board (12). [9] EMC filter (1) according to one of claims 1 to 8, characterized bythat the first carrier board (14) is arranged perpendicular to the main board (12).

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