WO2022017715A1

WO2022017715A1 - Emc filter having shielding

Info

Publication number: WO2022017715A1
Application number: PCT/EP2021/067299
Authority: WO
Inventors: Wolfram Kienle; Christoph Jatzek
Original assignee: Robert Bosch Gmbh
Priority date: 2020-07-22
Filing date: 2021-06-24
Publication date: 2022-01-27
Also published as: DE102020209238A1

Abstract

The invention relates to an EMC filter. The EMC filter (1) has a circuit board (2). The EMC filter (1) has at least one filter capacitor (3, 4), the at least one filter capacitor being connected to at least one electrically conductive ground layer (5, 6) by means of a respective terminal (7, 8). An additional terminal (9, 10) of the capacitor is connected to an additional electrically conductive layer (12, 13). The additional electrically conductive layer (12, 13) is an internal layer located in the circuit board (2), and the additional electrically conductive layer (12, 13) is shielded by the ground layer (5, 6) lying further outside.

Description

description

title

EMC filter with a shield

State of the art

The invention relates to an EMC filter, in particular for an electric vehicle. The EMC filter has a printed circuit board.

In vehicles with an electric drive, an inverter of the electric vehicle emits high-frequency interference signals, which radiate into one of the vehicle's on-board electrical systems, and these high-frequency interference signals can be radiated via electrical connecting lines, in particular power rails.

Disclosure of Invention

According to the invention, the EMC filter (EMC=Electro Magnetic Compatibility) of the type mentioned at the outset has at least one filter capacitor, which is connected to a connection with at least one electrically conductive ground layer. Another connection of the capacitor is connected to another electrically conductive layer. The further electrically conductive layer is designed as an inner layer arranged in the printed circuit board, the further electrically conductive layer being shielded—in particular at least partially or completely—by the ground layer lying further on the outside. A low-radiation filter can advantageously be formed in this way. Improved damping of the filter can also advantageously be formed in this way. The electrically conductive ground layer and/or the at least one further electrically conductive layer are each preferably formed as a copper layer. The filter can thus advantageously be formed in a cost-effective manner by means of a multilayer printed circuit board.

In a preferred embodiment, the EMC filter has at least two filter capacitors, in particular Y-capacitors, which are each connected to a terminal with at least one electrically conductive ground layer. In the EMC filter, one of the capacitors, in particular a positive capacitor, is connected to a further connection with a further electrically conductive positive layer, and the other of the two capacitors, in particular a negative capacitor, is connected to a further connection with a further, in particular negative, electrically conductive layer connected. The further electrically conductive layers, in particular the positive layer and the negative layer, are preferably in the form of internal layers which are arranged in the printed circuit board and are shielded by the ground layer lying further outside. The positive layer is preferably designed to carry a positive potential and the negative layer is designed to carry a negative potential. The positive potential and the negative potential is preferably a potential of an electrical supply network of the electric vehicle, in particular a battery potential. A potential difference between the positive and the negative potential is between 400 volts and 1000 volts, for example.

The further electrically conductive layers, in particular the positive layer and the negative layer, are preferably designed to carry a battery potential. More preferably, the layers of the circuit carrier carrying battery potential are formed only as internal layers shielded by the at least one ground layer. The filter can advantageously achieve a good damping effect in this way.

In a preferred embodiment, the filter has an X-capacitor, which in particular suppresses differential mode interference, and which is connected to the electrically conductive layers lying on the inside, in particular the positive and the negative layer. A connection of the X- Capacitor connected to the internal positive layer and another terminal of the capacitor connected to the internal negative layer. The electrical connections leading to the X-capacitor, in particular its electrical connections, can thus advantageously be shielded by the ground layer. The X capacitor can be implemented on a filter independently of the Y capacitor mentioned at the outset. The capacitor, in particular the Y capacitor and/or the X capacitor, is preferably in the form of a film capacitor or a ceramic multilayer capacitor.

A space-saving structure can advantageously be formed by the internal electrically conductive layers, which each carry the potential of the vehicle electrical system. In a further advantageous manner, shielding can thus be formed in a space-saving manner by the ground layer formed on the printed circuit board which is further outside.

The printed circuit board is preferably a fiber-reinforced printed circuit board, more preferably a glass fiber-reinforced epoxy resin printed circuit board.

In a preferred embodiment, the printed circuit board has two ground layers spaced apart from one another along a thickness of the printed circuit board, which enclose the at least one further layer, in particular the positive and/or the negative layer, between one another—in particular in the manner of a sandwich. Advantageously, the further electrically conductive layers, in particular the negative and/or the positive electrically conductive layer, can thus be completely shielded. The shielding can advantageously be integrated in the printed circuit board. The ground layers are preferably each formed as an outer electrically conductive layer on the printed circuit board. In this way, all internal electrically conductive layers or additional components in the circuit carrier, in particular the printed circuit board, can advantageously be electrically shielded.

In a preferred embodiment, the further electrically conductive layers, in particular the positive layer and/or the negative layer, are each arranged in the same plane. A particularly flat printed circuit board can advantageously be formed in this way. In another embodiment, the further electrically conductive layers, in particular the positive layer and/or the negative electrically conductive layer, are arranged spaced apart from one another—in particular spaced parallel to one another—in mutually different planes along a thickness extension of the circuit carrier. The circuit carrier can thus advantageously have a small circuit carrier area.

In a preferred embodiment, at least half of the further electrically conductive layer and the at least one ground layer overlap. The at least one further layer is advantageously shielded in this way. At least half of the circuit carrier is preferably covered by the ground layer. A low-inductance filter can advantageously be formed in this way.

In a preferred embodiment, the printed circuit board has at least one connection, which is formed by a recess that extends to the further electrically conductive layer and through which, in particular the recess, the further layer can be contacted from the outside. A screw connection for connecting the EMC filter to a busbar or an electrical connection can advantageously be formed in this way. The printed circuit board preferably has an opening in the area of the recess. In this way, a connecting means and/or fastening means, in particular a screw or a mandrel, can advantageously be passed completely through the printed circuit board.

The at least one further electrically conductive layer, in particular the positive layer and/or the negative layer, is preferably connected to a connection which is formed by a recess. Advantageously, a large part of a rewiring of the filter can be designed as an internal shielded connection.

In a preferred embodiment, the connections of the capacitor are each designed as THT connections (THT=through-hole technology). In this embodiment, a via is provided in the printed circuit board for each connection. Breakthrough formed, the via breakthrough being electrically connected to the respective further electrically conductive layer, in particular the positive and/or the negative layer.

In another embodiment, the connections of the capacitor are each connected to the at least one further layer by means of an insulation displacement connection. Advantageously, the insulation displacement connection can be designed as a surface-mountable component, in particular an SMD component, and can thus be connected to the printed circuit board in a cost-effective manner. The insulation displacement connection is preferably designed to be connected to a connecting wire of the capacitor and to cut and clamp the connecting wire.

In a preferred embodiment, the printed circuit board has an electrical connection, in particular a screw connection, which is connected to the at least one ground layer. The connection is preferably in the form of an electrically conductive via which is electrically connected to the at least one ground layer or to both ground layers. Advantageously, the filter can be connected to a ground potential by screwing or caulking or soldering a dome and can also be fastened in this way.

The invention also relates to a control unit or an inverter for an electric vehicle with the filter of the type described above. In the control unit or the inverter, a battery potential is connected to the internal electrically conductive layers of the filter. The internal management of the battery potential in the printed circuit board of the filter can advantageously have a good damping effect on the filter.

The invention is now described below with reference to figures and further exemplary embodiments. Further advantageous embodiment variants result from a combination of the features described in the figures and in the dependent claims. FIG. 1 shows an exemplary embodiment of a printed circuit board arrangement forming an EMC filter, in which internal connecting lines are shielded by external electrically conductive ground layers.

Figure 1 shows - schematically - an embodiment of a printed circuit board assembly 1 in a sectional view. In this exemplary embodiment, the printed circuit board arrangement 1 forms an EMC filter. The printed circuit board arrangement 1 has a printed circuit board 2 . In this exemplary embodiment, the printed circuit board 2 is in the form of a multilayer printed circuit board.

In this exemplary embodiment, circuit board 2 has a ground layer 5 and a ground layer 6. Ground layers 5 and 6 each form outer layers of circuit board 2 and enclose at least one electrically insulating layer 11 and two further electrically conductive layers between one another. Of the two further electrically conductive layers, one layer is a positive layer 12 and another layer is a negative layer 13.

The printed circuit board arrangement 1 also has two filter capacitors 3 and 4 in this exemplary embodiment. The filter capacitors 3 and 4 are each designed as Y-capacitors, which in particular suppress common-mode interference, and each form a capacitive bridge between a ground layer and the positive or negative layer.

The filter capacitor 3 has a ground connection 8 which is electrically conductively connected to the ground layer 5 . Another connection 10 of the filter capacitor 3 is connected to the negative electrically conductive layer 13 . The additional connection 10 extends into the printed circuit board 2 and makes contact with the additional layer, in particular the negative layer 13, inside the printed circuit board 2.

The filter capacitor 4 has a ground connection 7 which is connected to the ground layer 5 . The filter capacitor 4 also has a further connection 9 which extends into the printed circuit board 2 and is electrically connected there to the further layer, in particular the positive electrically conductive layer 12 . The circuit board 2 for the connections of the filter capacitors 3 and / or 4, which in this embodiment as Wire connections are formed, each having a blind hole or a via, which is formed at least up to the other electrically conductive layer, or the circuit board 2 completely penetrates. FIG. 1 also shows a variant for the printed circuit board 2 , which completely penetrates connecting wires, which are designed as THT connections (THT=through-hole technology) on the filter capacitor 4 . A connection wire 7 ′ shown in dashed lines, which is connected to the ground layer 5 , passes through the electrically insulating layer 11 and is connected to the ground layer 6 on the further side of the printed circuit board 2 . Another wire connection 9 ′ penetrates the printed circuit board 2 completely and is connected to the positive electrically conductive layer 12 and is electrically insulated from the ground layer 6 . The ground layer 6 can have a particularly cylindrical recess for insulation from the wire connection 9′.

In this exemplary embodiment, the printed circuit board 2 is designed for connection, in particular screw connection, to a ground potential or to at least one or two further potentials. For this purpose, the printed circuit board 2 has an opening 26 for screw connection to a ground potential. In this exemplary embodiment, the printed circuit board 2 is screwed to a busbar 21 carrying ground potential by means of a screw 18 . In this exemplary embodiment, the electrically conductive ground layers 5 and 6 are electrically connected to one another by means of the electrically conductive screw 18 .

In this exemplary embodiment, the ground layers 5 and 6 are electrically insulated from the further electrically conductive layers 12 and 13 by means of the electrically insulating layer 11 . The electrically insulating layer 11, in particular a fiber-reinforced, for example glass-fiber-reinforced, epoxy resin layer is formed in several layers in this exemplary embodiment and encloses the further electrically conductive layers 12 and 13 between the layers.

In this exemplary embodiment, the printed circuit board 2 has a recess 14 which extends to the further electrically conductive layer 12, in particular the positive layer, and is designed in such a way that the positive layer can be electrically contacted from the outside through the recess 14. the In this exemplary embodiment, the recess 14 is designed as a blind hole through which the electrically conductive layer 12 can be electrically contacted from the outside.

The printed circuit board 2 has an opening in the area of the recess 14, which is designed, for example, as an electrically conductive via sleeve.

In this exemplary embodiment, the further electrically conductive layer 12 is electrically conductively connected to a busbar 16 . For this purpose, the busbar 16 has an angled end section 27 which contacts a via sleeve 20 which is electrically connected to the further electrically conductive layer 12 .

The conductor rail 16 is, for example, soldered to the end section 27 with the via sleeve 20 .

The printed circuit board 2 has a recess 15 for contacting the further electrically conductive layer 13, which is formed from the outside up to the electrically conductive layer 13. The recess 15 is designed as a blind hole in the printed circuit board 2, for example. In this exemplary embodiment, the printed circuit board arrangement 1 also includes a screw 17 which contacts the further electrically conductive layer 13 with a screw head and penetrates the printed circuit board 2 . For this purpose, the printed circuit board 2 has an opening in the area of the recess 15 . In this exemplary embodiment, the screw 17, in particular an end section 28 passing through the circuit board 2, is screw-connected to a conductor rail 19, which is arranged on the side of the circuit board 2 opposite the recess for the screw head. The printed circuit board 2 can advantageously be screwed and/or soldered to the live potentials.

Instead of the conductor rail, the circuit board arrangement 1 can have a screw with the end section 27 which is arranged in the recess 14 and contacts the further electrically conductive layer 12 with its screw head. In another embodiment, the circuit board arrangement 1 can have a busbar contacting the further electrically conductive layer 13 instead of the screw 17 . The circuit board arrangement 1 can be soldered to the circuit board 2 instead of the screw 18 Have busbar with a arranged in the opening 26, angled end portion.

In this exemplary embodiment, the printed circuit board arrangement 1 also includes at least one shielding cap which encloses a filter capacitor. In this exemplary embodiment, the circuit board arrangement 1 comprises a shielding cap 24 which encloses the filter capacitor 4 and a shielding cap 25 which encloses the filter capacitor 3 . In this exemplary embodiment, the shielding caps 24 and 25 are each designed as metal caps, in particular aluminum caps, or copper caps. The shielding caps 24 and 25 can each be electrically conductively connected to the ground layer 5, in particular soldered.

In this exemplary embodiment, the ground layer 5 and/or the ground layer 6 of the printed circuit board 2 overlaps with the further electrically conductive layer 13 in an overlapping region 23. The electrically conductive layer 13 is on the overlapping region 23—in particular in the manner of a sandwich—between the parallel ones Ground layers 5 and 6 included.

The further electrically conductive layer 12, in particular the positive layer, overlaps with the ground layer 5 and/or the ground layer 6 in an overlapping region 22. The further electrically conductive layer 12 is in this exemplary embodiment--in particular in the manner of a sandwich--between the parallel to one another extending ground layers 5 and 6 along a thickness extension (29) of the circuit board 2 included.

The electrically conductive layers 12 and 13 are thus shielded by the ground layers 5 and 6 which form an outer layer of the circuit board 2, respectively. The EMC filter 1 formed by the printed circuit board arrangement 1 can thus advantageously be of low-radiation design.

Claims

Expectations

1. EMC filter (1), in particular for an electric vehicle, with a circuit carrier (2), in particular a printed circuit board, characterized in that the EMC filter (1) has at least one filter capacitor (3, 4), each with a connection (7, 8) is connected to at least one electrically conductive ground layer (5, 6), the capacitor (3, 4) being connected to a further terminal (9, 10) to a further electrically conductive layer (12, 13), wherein the further electrically conductive layer (12, 13) is designed as an inner layer which is arranged in the printed circuit board (2) and is shielded by the ground layer (5, 6) lying further on the outside.

2. Filter (1) according to claim 1, characterized in that the EMC filter (1) has at least two filter capacitors (3, 4), which each have a connection (7, 8) with at least one electrically conductive ground layer (5, 6) are connected, wherein a capacitor (4) of the capacitors (3, 4), in particular a positive capacitor (4), is connected to a further terminal (9) with a further electrically conductive positive layer (12), and the further capacitor ( 3), in particular negative capacitor (3), is connected to a further terminal (10) with a further, in particular negative, electrically conductive layer (13), the further electrically conductive layers (12, 13) being arranged on the inside in the circuit carrier (2). Layers (12, 13) are formed, which are shielded by the further outward ground layer (5, 6).

3. Filter (1) according to claim 1 or 2, characterized in that the printed circuit board (2) has two ground layers (5, 6) which are spaced apart from one another along a thickness extension (29) of the circuit carrier (2) and which have the at least one further layer (12, 13), in particular the positive layer (12) and the negative layer (13) enclose between each other.

4. Filter (1) according to any one of the preceding claims, characterized in that the filter has an X-capacitor which suppresses normal-mode interference in particular and which is connected to the internal electrically conductive layers, in particular the positive and the negative layer.

5. Filter (1) according to any one of the preceding claims, characterized in that the positive layer (12) and the negative layer (13) are each arranged in the same plane.

6. Filter (1) according to one of the preceding claims, characterized in that the positive layer (12) and the negative layer (13) are each arranged spaced apart from one another in mutually different planes along a thickness extension (29) of the circuit carrier (2).

7. Filter (1) according to any one of the preceding claims, characterized in that at least half of the further electrically conductive layer (12, 13) and the at least one ground layer (5, 6) overlap (22, 23) and the further layer (12, 13) is so shielded.

8. Filter (1) according to one of the preceding claims, characterized in that the circuit carrier (2) has at least one connection which is formed by a recess (14, 15) which extends up to the further electrically conductive layer (12, 13 ) and through which the further layer (12, 13) can be contacted from the outside.

9. Filter (1) according to one of the preceding claims, characterized in that the connections (7, 8, 9, 10) of the capacitor (3, 4) are each designed as THT connections.

10. Filter (1) according to one of the preceding claims, characterized in that the connections (7, 8, 9, 10) of the capacitor (3, 4) are each connected to the at least one further layer (12 , 13) are connected.

11. Filter (1) according to any one of the preceding claims, characterized in that the printed circuit board (2) has a screw connection (18, 26) which is connected to the at least one ground layer (5, 6).

12. Filter (1) according to any one of the preceding claims, characterized in that the further electrically conductive layers (12, 13) are designed to carry a battery potential and the battery potential-carrying layers (12, 13) only as internal layers shielded from the at least one ground layer

layers are formed.