EMC filters for power electronics

Abstract

For an EMC filter for power electronics, comprising a housing (30), wherein at least one printed circuit board (40) is arranged in the housing (30), wherein at least one electrical and / or electronic component (45) is arranged on the printed circuit board (40), wherein at least one first busbar (10) and at least one second busbar (20) is arranged in the housing (30), it is proposed that the housing (30) is at least partially filled with a potting compound (50), wherein the first busbar (10), the second busbar (20) and the printed circuit board (40) are potted in the housing (30) in the potting compound (50).

Description

State of the art

[0001] The invention relates to an EMC filter for power electronics.

[0002] In addition to circuit boards and busbars, an EMC filter for power electronics also includes electrical and / or electronic components, which are located, for example, on the circuit boards. The EMC filter also includes a housing and often one or more magnetic cores through which the busbars run. To electrically and mechanically connect the components in an EMC filter, they are fixed to the housing using screw connections, additional clamping components, or other mechanical connection techniques, such as snap-in hooks or press connections. For example, the circuit board with the electrical and / or electronic components is screwed to screw points in the housing, and the busbars are connected to the housing using clamping components.

[0003] The possible thermal connection is achieved via thermally conductive media, which is partially applied to critical areas. Disclosure of the invention

[0004] According to the invention, an EMC filter for power electronics is proposed. The EMC filter comprises a housing, wherein at least one printed circuit board is arranged in the housing, wherein at least one electrical and / or electronic component is arranged on the printed circuit board, wherein at least one first busbar and at least one second busbar are arranged in the housing. According to the invention, the housing is at least partially filled with a potting compound, wherein the first busbar, the second busbar, and the printed circuit board are potted in the potting compound in the housing. Advantages of the invention

[0005] Compared to the prior art, the EMC filter with the features of the independent claim has the advantage that the parts of the EMC filter arranged in the housing are encapsulated by the potting compound. The parts of the EMC filter arranged in the housing are thus completely or at least partially encased by the potting compound.

[0006] The EMC filter exhibits significantly increased vibration resistance due to the encapsulation of the components in the housing. The circuit board with at least one electrical and / or electronic component and the conductor rails are each vibration-proof connected to the housing by the encapsulation compound. This results in an advantageously robust EMC filter. The EMC filter is significantly less susceptible to errors that can occur due to vibration loads. This allows the EMC filter to be used in applications exposed to high vibration loads, such as in the commercial vehicle segment, where the loads are particularly high due to long operating times and service lives. The EMC filter therefore exhibits an advantageously longer service life.

[0007] Furthermore, the potting compound that encloses the EMC filter components and fills the gaps between them achieves optimized heat dissipation compared to the state of the art. The heat is dissipated over a large area and in all directions, for example, from the circuit board and the busbars to the housing via the potting compound. The housing can then dissipate the heat over a large area to the area surrounding the EMC filter. This allows the thermally connected surface to be maximized, thus optimizing the cooling effect.

[0008] This ensures that the EMC filter is cooled effectively and thus increases the performance of the EMC filter.

[0009] In the EMC filter, the mounting, insulation, and heat dissipation of the individual components are realized solely through the potting compound. Thus, no additional fixtures or materials are required for the mounting, insulation, and heat dissipation of the circuit board and busbars in the housing. This reduces the number of components required, and the EMC filter can be manufactured cost-effectively with only a few process steps. This advantageously eliminates screw joints and process steps such as welding, soldering, or pressing.

[0010] Because fewer components are required, the EMC filter can also be designed more compactly.

[0011] Further advantageous embodiments and developments of the invention are made possible by the features specified in the subclaims.

[0012] According to an advantageous embodiment, at least one magnetic core is further arranged in the housing, with the first busbar and the second busbar extending through the magnetic core, the magnetic core being at least partially encapsulated by the potting compound. Thus, the magnetic core of the SMD filter is also connected to the housing, the circuit board, and the busbars of the EMC filter by the potting compound.

[0013] According to an advantageous exemplary embodiment, it is provided that a first gap, which is formed between the first busbar and the magnetic core and circumferentially surrounds the first busbar, is filled with the potting compound and / or a second gap, which is formed between the second busbar and the magnetic core and circumferentially surrounds the second busbar, is filled with the potting compound. The magnetic core is pushed onto the busbars. In order to be able to push the magnetic core onto the busbars without force, a first gap is formed between the magnetic core and the first busbar and a second gap is formed between the magnetic core and the second busbar. The gaps between the magnetic core and the busbars allow a relative movement of the cores to the busbars and to the housing.If the gaps are filled with the potting compound, this relative movement is prevented and the cores are firmly attached to the busbars and the housing. Thus, the cores are not exposed to vibration loads.

[0014] According to an advantageous embodiment, it is provided that the potting compound has a, in particular flat, potting surface up to which the potting compound extends in the housing, wherein the first busbar and / or the second busbar run plane-parallel to the potting surface. However, the first busbar and / or second busbar can also run in a different orientation and run at an angle to the potting surface. According to an advantageous embodiment, it is provided that an upper part of the magnetic core protrudes from the potting compound. The upper part of the magnetic core protruding from the potting compound can be used as a cooling element and / or as a contact element to the device housing and connected with thermally conductive media. However, the magnetic core can also be completely enclosed by the potting compound, for example.

[0015] According to an advantageous embodiment, a flat cooling surface is formed on the magnetic core, wherein the cooling surface is arranged outside the potting compound. The cooling surface of the magnetic core can serve to dissipate heat from the magnetic core and can be connected, for example, to a heat sink, which can also be part of the housing.

[0016] According to an advantageous embodiment, an opening is formed in the housing, wherein the opening is closed by a sealing device. The housing can thus be filled with the potting compound even beyond the opening without the still-liquid potting compound flowing out of the opening. Once the potting compound has hardened, the sealing device in the opening can, for example, be removed again.

[0017] According to an advantageous exemplary embodiment, it is provided that the first busbar and / or the second busbar run through the opening from an interior of the housing into an exterior of the housing, wherein the sealing device, together with the busbars running through the opening, tightly closes the opening. The busbars can therefore also run out of the housing in the region in which the housing is filled with the potting compound. The housing is sealed by the sealing device at the point where the busbars run from the interior of the housing to the exterior of the housing, such that the potting compound can flow around the busbars in the interior of the housing even at the openings, without the potting compound that has not yet hardened being able to flow through the openings in the exterior of the housing.

[0018] According to an advantageous embodiment, the sealing device comprises a plastic part and a solid seal.

[0019] According to an advantageous embodiment, it is provided that the first busbar runs in the housing plane-parallel to the second busbar and in particular the first busbar runs above the second busbar. Short description of the drawings

[0020] Embodiments of the invention are illustrated in the drawing and are explained in more detail in the following description. It shows Fig. 1 a cross-section through a schematically illustrated first embodiment of the EMC filter, Fig. 2 a view of a second embodiment of the EMC filter without potting compound, Fig. 3 a view of the second embodiment of the EMC filter from Fig. 2 with casting compound. Embodiments of the invention

[0021] Fig. Figure 1 shows a cross-section through a schematically illustrated EMC filter 1. EMC filters 1 are used to suppress electromagnetic interference. EMC refers to electromagnetic compatibility. The EMC filter 1 can, for example, be designed as a passive filter without active elements such as transistors. The EMC filter 1 is used, for example, in vehicles, particularly electric vehicles. The EMC filter 1 can be used, in particular, in commercial vehicles. For example, the EMC filter 1 can be part of an inverter.

[0022] The EMC filter 1 comprises a first busbar 10 and a second busbar 20. The first busbar 10 and the second busbar 20 together form a busbar pair. The busbars 10, 20 are used to carry high currents. In the context of the present application, a busbar 10, 20 is understood to be an electrically conductive conductor, for example, an electrically conductive bar or an electrically conductive strip. Fig. 1 shows a cross-section perpendicular to the plane of extension of the busbars 10, 20. The busbars 10, 20 are designed, for example, as a busbar. In this exemplary embodiment, the busbars 10, 20 each run in one plane. The first busbar 10 runs in a first plane. The second busbar 20 runs in a second plane. The first busbar 10 runs plane-parallel to the second busbar 20. The busbars 10, 20 can also be bent or curved, for example, or can run in a curved or stepped manner. The busbars 10, 20 are made of an electrically conductive material, for example a metal such as copper. The busbars 10, 20 are designed, for example, in one piece. The busbars 10, 20 are each made, for example, continuously from the same material. The busbars 10, 20 are designed, for example, as stamped parts.The first busbar 10 and / or the second busbar 20 can have a constant thickness along a longitudinal extent, for example, perpendicular to the current direction. Furthermore, the first busbar 10 and the second busbar 20 can have a constant width along a longitudinal extent of the respective busbar 10, 20, for example, perpendicular to the current direction. The first busbar 10 runs parallel to the second busbar 20. The first busbar 10 can, for example, form a forward conductor, and the second busbar 20 can form the return conductor to the first busbar 10.

[0023] The first busbar 10 is separated from the second busbar 20 by a gap and is electrically insulated from it. For example, the current flows in the first busbar 10 in the opposite direction to that in the second busbar 20. The current direction in the first busbar 10 and the current direction in the second busbar 20 are opposite to each other. The first busbar 10 runs directly above the second busbar 20. The first busbar 10 overlaps the second busbar 20. A projection of the first busbar 10 onto the second busbar 20 lies, for example, exactly in the second busbar 20.

[0024] The EMC filter 1 further comprises at least one magnetic core 60. The magnetic core 60 can be made of a soft magnetic material. A soft magnetic material is classified in the IEC 60404-1 standard. The magnetic core 60 can be made of ferrite, for example. The magnetic core 60 can be a powder magnetic core, for example, or can also consist of crystalline or amorphous metal strips. The magnetic core 60 is ring-shaped, for example. The magnetic core 60 forms, for example, a closed magnetic circuit.

[0025] The magnetic core 60 can, for example, be formed in one piece. However, the magnetic core 60 can also be composed of several magnetic core segments, for example. The magnetic core segments can have different shapes. The magnetic core 60 is, for example, ring-shaped. The magnetic core 60 is, for example, toroidal.

[0026] The first busbar 10 and the second busbar 20 extend through the magnetic core 60. The magnetic core 60 surrounds the busbars 10, 20, for example, in a ring shape. Two recesses are formed in the magnetic core 60. The first busbar 10 extends through the first recess of the magnetic core 60. The second busbar 20 extends through the second recess of the magnetic core 60. The first recess and / or the second recess are, for example, rectangular in cross-section.

[0027] A first gap 15 is formed between the magnetic core 60 and the first busbar 10. The first gap 15 surrounds the first busbar 10 in an annular manner. The first gap 15 is arranged in the first recess of the magnetic core 60. A second gap 25 is formed between the magnetic core 60 and the second busbar 20. The second gap 25 surrounds the first busbar 10 in an annular manner. The second gap 25 is arranged in the second recess of the magnetic core 60.

[0028] The magnetic core 60, together with the first busbar 10 and the second busbar 20, forms, for example, a current-compensated choke or common-mode choke. The EMC filter 1 comprises, for example, as shown in the Fig. 2 and Fig. 3 illustrated embodiment, a plurality of magnetic cores 60, which are all lined up, for example, and each of which also surrounds the first busbar 10 and the second busbar 20.

[0029] The EMC filter 1 further comprises at least one printed circuit board 40. The printed circuit board 40 can, for example, be a rigid printed circuit board, for example a printed circuit board in FR4 design or higher, i.e., for example, a printed circuit board made of glass fiber reinforced epoxy resin. However, the printed circuit board 40 can also be an HDI (High Density Interconnect) printed circuit board, an LTCC (Low Temperature Cofired Ceramics), or another suitable rigid printed circuit board. One or more electrical and / or electronic components 45, connected to one another, for example, by conductor tracks, are arranged on the printed circuit board 40. The printed circuit board 40 is electrically contacted with the first busbar 10 and / or the second busbar 20 via electrical connection elements. The electrical and / or electronic components 45 can, for example, be designed as capacitors.The capacitors can be used, for example, as X-capacitors to attenuate differential-mode interference voltages. Furthermore, the capacitors can be used, for example, as Y-capacitors to suppress common-mode interference. Furthermore, the electrical and / or electronic components 45 can also be designed, for example, as chokes, in particular uncompensated ones. Furthermore, the electrical and / or electronic components 45 can also be resistors or other components, for example.

[0030] Furthermore, the EMC filter 1 comprises a housing 30. The housing 30 can be made of a metal, for example. The housing serves to accommodate the circuit board 40 and the magnetic core 60. The busbars 10, 20 run through the housing 30. Openings 33, for example, are formed on the housing 30. This is shown in the second embodiment in Fig. 2 and Fig. 3. Two openings 33 are formed in the housing 30. The two openings 33 are formed in the housing 30 on opposite sides of the housing 30. The busbars 10, 20 extend through the openings 30. The busbars 10, 20 extend partially in the interior 31 of the housing 30 and partially in the exterior 32 of the housing 30. The magnetic core 60 is arranged in the interior 31 of the housing 30. The circuit board 40 is arranged in the interior 31 of the housing 30.

[0031] The housing 30 is filled with potting compound 50. The potting compound 50 encloses the busbars 10, 20 in the housing 30. The potting compound 50 encloses the magnetic core 60 at least partially in the housing 30. For example, as in the Fig. 2 and Fig. In the second embodiment of the EMC filter shown in Figure 3, an upper part 65 of the magnetic core 60 protrudes from the potting compound 50. The potting compound 50 further encloses the printed circuit board 40, in particular completely, in the housing 30. The housing 30 is, for example, completely filled with the potting compound 50.

[0032] The potting compound 50 is a flowable and curable compound. The potting compound 50 is poured into the housing 30 in a liquid state and then cured within the housing 30. After curing, the potting compound 50 is no longer liquid.

[0033] The busbars 10, 20, the circuit board 40 with the electrical and / or electronic components 45, and the magnetic core 60 are arranged in the housing 30. The potting compound 50 is then poured into the housing 30 in a liquid state. The potting compound 50 flows into all gaps and spaces between the housing 30 and the elements arranged in the housing 30. The potting compound 50 is then cured. Thus, the busbars 10, 20, the magnetic core 60, and the circuit board with the electrical and / or electronic components 45 are fixed in the housing 30. The potting compound 50 is selected, for example, based on criteria such as viscosity, Shore hardness, Young's modulus, elongation at break, and expansion coefficient.

[0034] Sealing devices 70 are provided in the openings 33. The sealing devices 70 seal the opening 33 through which the busbars 10, 20 extend. The sealing device 70 is designed such that the area in the opening 33 between the housing 30 and the busbars 10, 20 extending through the opening 33 is sealed. The sealing device 70 is, as shown in Fig. 2 and Fig. 3, is designed as a plastic component with a solid seal. Depending on the viscosity of the potting compound, the tolerance range, or the shape of the parts, the sealing device may also be omitted. For example, foam or adhesive can also be used to seal the openings 33. If, for example, the housing 30 is completely closed without side openings 33, it is sufficient to prevent the potting compound 50 from leaking out by regulating the fill level.

[0035] Of course, further embodiments and mixed forms of the embodiments shown are also possible.

Claims

[1] EMC filter for power electronics, comprising a housing (30), wherein at least one printed circuit board (40) is arranged in the housing (30), wherein at least one electrical and / or electronic component (45) is arranged on the printed circuit board (40), wherein at least one first busbar (10) and at least one second busbar (20) is arranged in the housing (30), characterized by that the housing (30) is at least partially filled with a potting compound (50), wherein the first busbar (10), the second busbar (20) and the printed circuit board (40) in the housing (30) are potted in the potting compound (50). [2] EMC filter according to claim 1, characterized by that at least one magnetic core (60) is further arranged in the housing (30), wherein the first busbar (10) and the second busbar (20) run through the magnetic core (60), wherein the magnetic core (60) is at least partially encapsulated by the encapsulating compound (50). [3] EMC filter according to claim 2, characterized by that a first gap (15) which is formed between the first busbar (10) and the magnetic core (60) and circumferentially surrounds the first busbar (10) is filled by the potting compound (50) and / or a second gap (25) which is formed between the second busbar (20) and the magnetic core (60) and circumferentially surrounds the second busbar (20) is filled by the potting compound (50). [4] EMC filter according to one of the preceding claims, characterized by that the potting compound (50) has a, in particular flat, potting surface (51) up to which the potting compound (50) extends in the housing (30), wherein the first busbar (10) and / or the second busbar (20) run plane-parallel to the potting surface (51). [5] EMC filter according to one of claims 2 to 4, wherein an upper part (65) of the magnetic core (60) protrudes from the potting compound (50). [6] EMC filter according to one of claims 2 to 5, characterized by that a flat cooling surface (61) is formed on the magnetic core (60), wherein the cooling surface (61) is arranged outside the potting compound (50). [7] EMC filter according to one of the preceding claims, characterized by that an opening (33) is formed in the housing (30), wherein the opening (33) is closed by a sealing device (70). [8] EMC filter according to claim 7, characterized by that the first busbar (10) and / or the second busbar (20) extend through the opening (33) from an interior (31) of the housing (30) into an exterior (32) of the housing (30), wherein the sealing device (70) together with the busbars (10, 20) extending through the opening (33) tightly closes the opening (33). [9] EMC filter according to one of claims 7 or 8, characterized bythat the sealing device (70) comprises a plastic part and a solid seal. [10] EMC filter according to one of the preceding claims 2 to 9, characterized by that the first busbar (10) in the housing (30) runs plane-parallel to the second busbar (20) and in particular the first busbar (10) runs above the second busbar (20).

Images