Device for a current transformer, current transformer and vehicle

Abstract

The invention relates to a device (100) for a current transformer (200), comprising: - at least one separating layer (1), - at least one conductor layer (2), - at least one power semiconductor (3), wherein the at least one separating layer (1), the at least one conductor layer (2) and the at least one power semiconductor (3) are at least partially encapsulated in a potting compound (M), wherein the device (100) has at least one connection surface (K) for electrical contact, wherein the at least one connection surface (K) is configured as a connection of a DC terminal of the device (100), characterized in that the potting compound (M) does not cover the at least one connection surface (K), wherein the at least one connection surface (K) is planar, wherein the at least one connection surface (K) is configured as a partial surface of the at least one conductor layer (2) or is arranged in a plane parallel above the at least one conductor layer (2), such that the at least one connection surface (K) overlaps the at least one conductor layer (2), as well as a current transformer (200) and a vehicle (300).

Description

[0001] The invention relates to a device for a current transformer, a current transformer and a vehicle.

[0002] In power electronic circuits, such as those used in inverters for electric vehicles, a high switching speed of the power semiconductors used, such as MOSFETs, is desirable. It is known that the switching speed can be improved primarily by reducing the parasitic inductance in the power electronic circuit, especially in the commutation cell.

[0003] DE 10 2019 109 461 A1 is a generic patent and relates to a power module with at least one power semiconductor switch and a DC link capacitor for a power converter, wherein the DC link capacitor is connected to the power module by a screw connection. However, a disadvantage is that the DC link capacitor can only be connected to the power module by a screw connection and the parasitic inductance remains too high.

[0004] DE 11 2023 001 614 T5 relates to a semiconductor device.

[0005] DE 10 2022 124 513 A1 relates to a printed circuit board arrangement and a method for manufacturing such a printed circuit board arrangement.

[0006] DE 10 2023 202 386 A1 relates to a power electronics module, an inverter for an electric drive of a motor vehicle and a method for manufacturing a power electronics module.

[0007] The technical problem is to create a device for a current transformer, a current transformer and a vehicle that can increase flexibility in the type of mechanical connection and further reduce parasitic inductance.

[0008] The solution to the technical problem is provided by the articles with the features of the independent claims. Further advantageous embodiments of the invention are described in the dependent claims.

[0009] A device for a current transformer is proposed, comprising: - at least one separating layer, - at least one conductor layer, - at least one power semiconductor, wherein the at least one separating layer, the at least one conductor layer and the at least one power semiconductor are at least partially encapsulated in a potting compound, wherein the device has at least one contact surface for electrical contact, wherein the potting compound does not cover the at least one contact surface, wherein the at least one contact surface is designed as a connection of a DC terminal of the device.

[0010] According to the invention, the at least one connection surface is planar, wherein the at least one connection surface is formed as a partial surface of the at least one conductor layer or is arranged in a plane parallel above the at least one conductor layer, so that the at least one connection surface overlaps the at least one conductor layer.

[0011] The device has the advantage that, for example, a DC link capacitor can be electrically connected directly to the conductor layer or in a plane parallel to the conductor layer. This shortens conductor paths and thus reduces parasitic effects. Both alternatives also share the advantage that the planar contact surface offers increased flexibility in the type of mechanical connection. For example, the contact surface can be made contact by busbars, wires, and / or brushes using force-fit, form-fit, and / or material-fit connections. The aforementioned alternatives are thus interconnected in such a way that they realize a single general inventive idea.

[0012] A current transformer comprising at least one device according to an embodiment described in this disclosure is further proposed. The current transformer can, for example, be configured as an inverter, in particular as a pulse inverter. The current transformer can, in particular, be configured for use in a vehicle. The current transformer can be arranged between a traction battery of the vehicle and an electric motor of the vehicle, for example, to convert direct current from the traction battery into alternating current for the electric motor. The current transformer can further comprise a DC link capacitor. The device can, for example, be connected to the DC link capacitor on the input side and to the electric motor on the output side. The device can be part of a commutation cell of the current transformer. The device can also be referred to as a power module or power box.

[0013] A further proposal is a vehicle comprising at least one current transformer according to an embodiment described in this disclosure. The vehicle can be, for example, a car, bus, truck, rail vehicle, aircraft, or watercraft. Due to the reduced parasitic inductance during electrical operation, the vehicle can achieve a greater range, since the reduced parasitic inductance improves, for example, the switching times of the power semiconductors and thus minimizes electrical losses during current conversion.

[0014] The technical effects and advantages described in this disclosure for the device also apply, of course, to the current transformer and the vehicle, and vice versa.

[0015] The separating layer can also be referred to as a substrate or circuit carrier. The separating layer is electrically non-conductive. It can be made of a non-metallic material such as ceramic. A conductor layer can be arranged on the top side of the separating layer. A metal layer can be arranged on the bottom side of the separating layer. In particular, the bottom side of the metal layer can serve to connect a heat sink to the device. The metal layer can, in particular, be grounded.

[0016] The conductor layer can also be called a metallization layer. The conductor layer is electrically conductive and can be made of copper, for example. The conductor layer is typically planar. It can be formed as a plate. The top surface of the conductor layer can be a plane or span. The conductor layer can have multiple conductor tracks, which may have different electrical potentials. Naturally, insulating gaps may exist between the conductor tracks in the conductor layer, which are filled, for example, with potting compound. A first conductor track, for example, can be connected to the positive terminal of a vehicle's high-voltage battery via the intermediate circuit capacitor and therefore have a high electrical potential. Another conductor track, for example, can be connected to the negative terminal of a vehicle's high-voltage battery via the intermediate circuit capacitor and therefore have a low electrical potential.

[0017] The power semiconductor can be a transistor or at least include one. The transistor can be, for example, a MOSFET or IGBT. The power semiconductor can be electrically connected to the conductor layer, for example, by soldering or sintering. In particular, the power semiconductor can be located on the first conductor track mentioned earlier and be electrically connected to the next conductor track, for example, via a bond wire.

[0018] The potting compound can be a flowable plastic such as polyurethane or epoxy resin. In its cured state, exposed areas of the device's surface, particularly the surface of the separating layer, the conductor layer, and / or the power semiconductor, may be covered with the potting compound. The potting compound serves as passive protection for the device against damage and contamination.

[0019] The contact surface is not covered by the potting compound, allowing it to be contacted from the outside. The contact surface can, for example, have a size ranging from 0.1 to 5 square centimeters, particularly from 0.5 to 5 square centimeters. The contact surface is planar, i.e., flat and straight. In particular, the device has at least one first planar contact surface for a first electrical potential and at least one further planar contact surface for a further electrical potential. In particular, the first contact surface is configured as a partial surface of the at least one first conductor track or arranged in a plane parallel to the at least one first conductor track.Furthermore, the additional connection surface is designed as a partial surface of at least one additional conductor track or arranged parallel to the at least one additional conductor track in a further plane (or the previously mentioned plane). This allows the first and the additional connection surfaces to function as a fully functional DC terminal of the device – with the advantages mentioned at the outset.

[0020] If the contact surface is arranged in a plane parallel to the conductor layer, then the contact surface is offset vertically to the top surface of the conductor layer. Specifically, the contact surface overlaps the conductor layer in a spatial direction that is oriented, for example, parallel to a current flow direction through the conductor layer. The plane in which the contact surface is arranged can be offset, for example, by a maximum of five centimeters parallel to the top surface of the conductor layer.

[0021] In one embodiment, the potting compound has at least one recess, wherein the at least one contact surface forms the bottom of the recess. In this way, the aforementioned free areas of the device's surface, particularly the conductor layer—apart from the contact surface—can be covered with potting compound. In other words, the recess allows the contact surface to be a partial area of ​​the conductor layer without compromising the protection provided by the potting compound. The recess can be created, for example, by masking the conductor layer in the area of ​​the contact surface during the potting process. The recess can be conically shaped to facilitate external contact with the contact surface.

[0022] In one embodiment, the at least one connection surface is arranged in the plane parallel to the at least one conductor layer by means of at least one spacer. In this way, the connection surface can be spaced apart from the conductor layer without losing the flexibility of the mechanical connection described above. The spacer can, for example, be made of copper. The spacer can, for example, be cuboid in shape or designed as a bent sheet. The connection surface can, for example, be a top surface of the spacer. A bottom surface of the spacer contacts, for example, the conductor layer, thus establishing an electrical connection between the connection surface and the conductor layer. The spacer is particularly well bonded to the conductor layer. For example, a bottom surface of the spacer can be welded to a top surface of the conductor layer.

[0023] In one embodiment, the at least one contact surface is arranged flush with the top surface of the potting compound. This allows the spacer to be potted without covering the contact surface with the compound. This improves the protection of the device. In particular, the previously described recess in the potting compound is unnecessary. Instead, the spacer can be bonded to the conductor layer, and the device can then be potted in the compound as usual. The contact surface can be masked for the potting process. The potting compound can, for example, frame the contact surface. The top surface of the potting compound can form a top surface of the device.

[0024] In one embodiment, the at least one spacer has a C-profile. This allows the spacer to be manufactured with particularly low material usage, especially compared to a cuboid. This reduces material costs and the weight of the device. The C-profile can, for example, be the cross-sectional shape of the spacer. The spacer can, for example, be designed as a so-called C-sheet. The C-sheet can, for example, be a double-bent sheet. The C-sheet can have a constant thickness. A top surface of the C-profile can form the planar contact surface. A bottom surface of the C-profile can be connected to the conductor layer, for example, by laser welding.

[0025] In one embodiment, the at least one conductor layer has at least one first conductor track with a first electrical potential and at least one further conductor track with a further electrical potential, wherein the at least one spacer contacts the at least one first conductor track, and wherein the at least one spacer is configured such that it at least partially overlaps the at least one further conductor track in one spatial direction. Due to the overlap, the electromagnetic effects between the further conductor track and the spacer can be better contained. Since a top surface of the spacer can serve as a contact surface, the contact area can also be easily increased by the described overlap. The cross-sectional shape of the spacer can, for example, have a T-profile to achieve the overlap.The spatial direction in which the spacer overlaps the other conductor track is oriented orthogonally to the direction of current flow through the other conductor track. The other conductor track features, in particular, the additional connection surface described earlier, for connecting the device, for example, to the negative terminal of a high-voltage battery. In the area of ​​overlap, potting compound can, of course, be applied between the spacer and the other conductor track to isolate the different electrical potentials. The distance between the spacer and the at least one other conductor track in the area of ​​overlap can, for example, be between 0.1 mm and five centimeters.

[0026] In one embodiment, the at least one spacer contacts several first conductor tracks of a first electrical potential, wherein at least one further conductor track of a further electrical potential is arranged between the first conductor tracks, and wherein the at least one spacer is designed such that it completely overlaps the at least one further conductor track in one spatial direction. Due to the complete overlap of the further conductor track, the electromagnetic effects between the further conductor track and the spacer can be further reduced. For example, the cross-sectional shape of the spacer can be a double-T profile to achieve the complete overlap of the further conductor track. The spatial direction in which the spacer overlaps the further conductor track is, in particular, oriented orthogonally to a current flow direction through the further conductor track.

[0027] In one embodiment, the at least one spacer has at least one opening in its at least one connection surface, the opening being opposite a connection point of the spacer. This allows a laser beam for laser welding to pass through the opening and act on the connection point, thus bonding the spacer to the conductor layer. The opening can be, for example, a small hole in the top surface of the previously described C-sheet. The connection point can be a weld point on the underside of the previously described C-sheet. The spacer can have at least one further opening, for example, in a vertical section of the C-sheet. This further opening can serve to fix the spacer in a position on the at least one conductor layer. This allows the spacer to be, for example,The components are positioned and fixed in place on the conductor layer by a gripping robot in order to perform laser welding more precisely.

[0028] The invention is explained in more detail using exemplary embodiments. The figures show: Fig. 1 a schematic representation of an embodiment of a current transformer with a device, Fig. 2 a schematic representation of another embodiment of a current transformer with a device, Fig. 3 a schematic representation of another embodiment of a current transformer with a device, Fig. 4 a schematic representation of another embodiment of a current transformer with a device, Fig. 5 a schematic representation of another embodiment of a current transformer with a device Fig. 6 a schematic representation of another embodiment of a current transformer with a device, Fig. Figure 7 shows a schematic representation of another embodiment of a current transformer with a device.

[0029] In the following, identical reference symbols denote elements with the same technical characteristics.

[0030] Fig. Figure 1 shows a schematic representation of an embodiment of a current transformer 200 designed as a pulse inverter with a device 100 for the current transformer 200.

[0031] The current transformer 200 is installed in a vehicle 300 designed as a passenger car, which is partially or fully electrically powered. The current transformer 200 converts, for example, direct current from a high-voltage battery (not shown) into alternating current to drive an electric motor (not shown).

[0032] To simplify the explanation of device 100, see in Fig. Figure 1 shows a vehicle-mounted, Cartesian coordinate system. The coordinate system is also shown in the Fig. 2 to Fig. Figure 6 illustrates this. A vertical axis Z of the coordinate system is, for example, oriented opposite to one direction of gravity. A longitudinal axis X and a transverse axis Y are each oriented orthogonally to the vertical axis Z. The longitudinal axis X can, for example, be parallel to one direction of travel of vehicle 300. The transverse axis Y can accordingly be oriented orthogonally to the direction of travel of vehicle 300.

[0033] The device 100 can be described as a power module. The device 100 comprises several components, namely a separating layer 1, a conductor layer 2, a power semiconductor 3, and a metal layer 4. The aforementioned components are almost completely encapsulated in a potting compound M, e.g., made of polyurethane.

[0034] The separating layer 1 is made of a ceramic, for example, and serves as a non-conductive circuit carrier that electrically insulates the conductive layer 2 from the metal layer 4, which is made of copper, for example. The separating, conductive, and metal layers 1, 2, and 4 can form a so-called direct-bonded copper structure.

[0035] An underside of the metal layer 4 can serve to connect a heat sink (not shown) to the device 100 and is therefore of course free of potting compound M.

[0036] The conductor layer 2 is, for example, arranged on a top surface of the separating layer 1 and is flat. The conductor layer 2 is, for example, made of copper and has several conductor tracks 21, 22, which are designed to carry different electrical potentials of a direct current.

[0037] A power semiconductor 3 designed as a MOSFET is also arranged on the upper side of the first conductor track 21 of conductor layer 2. A lower side of the power semiconductor 3 is electrically connected to the first conductor track 21, for example by sintering. Fig. Figure 1 therefore shows a sintered layer 13. One top side of the power semiconductor 3 is connected, for example, to the further conductor track 22 via a bond wire 14. With the help of the power semiconductor 3, the direct current supplied via the conductor tracks 21, 22 can, for example, be converted into alternating current. For this purpose, the device 100 can of course include further conductor tracks, power semiconductors and AC connections, which are shown in Figure 100 for better clarity. Fig. 1 are not shown.

[0038] To enable external contact with the conductor tracks 21, 22 of conductor layer 2, each conductor track 21, 22 has a planar contact surface K. The contact surfaces K are thus sub-areas of the respective conductor track 21, 22. The contact surfaces K can be circular or rectangular in shape. The contact surfaces K can each have, for example, a size of two square centimeters. The contact surfaces K can form a DC terminal of the device 100.

[0039] The potting compound M has a conical recess A for each of the connection surfaces K, with the respective connection surface K forming the base of the recess A. This allows the components of the device 100 – apart from the connection surfaces K – to be encased in the potting compound M and thus optimally protected from environmental influences, while the connection surfaces K simultaneously form part of the planar conductor layer 2.

[0040] The current transformer 200 can, for example, include a DC link capacitor (not shown). A first busbar (not shown) of the DC link capacitor can be directly electrically connected to the first conductor track 21 via the first connection surface K. A second busbar (not shown) of the DC link capacitor can be directly electrically connected to the second conductor track 22 via the second connection surface K.

[0041] The in Fig. The connection surfaces K shown in Figure 1 offer the advantage of increased flexibility in the electrical connection of electronic components of the current transformer 200 – as explained, for example, in the previous paragraph for the intermediate circuit capacitor – to the device 100. Electrical connection via the connection surfaces K can be achieved, for example, by welding, soldering, or by means of an electrically conductive spring. Because each connection surface K is a partial area of ​​the conductor layer 2, the conduction paths to the power semiconductor 3 are particularly short, thus minimizing parasitic effects.

[0042] Fig. Figure 2 shows a schematic representation of another embodiment of a current transformer 200 with a device 100 for the current transformer 200.

[0043] In contrast to the one in Fig. In the embodiment shown in Figure 1, the connection surfaces K are not a sub-surface of the conductor layer 2, but are each arranged in a plane parallel to the conductor layer 2 by means of a spacer C designed as a copper cuboid. The spacers C are encased in the potting compound M, except for the respective connection surface K.

[0044] The connection surfaces K are spaced vertically from conductor layer 2 along the vertical axis Z by the respective spacer C. The distance between conductor layer 2 and the connection surface K can be, for example, 0.5 mm to 1 mm. This means that the recesses A do not need to penetrate as deeply into the potting compound M, which in turn facilitates the connection of electronic components to the connection surfaces K. The respective spacer C can be connected to the respective conductor track 21, 22 of conductor layer 2, for example, by welding or soldering.

[0045] Fig. Figure 3 shows a schematic representation of another embodiment of a current transformer 200 with a device 100 for the current transformer 200.

[0046] In contrast to the one in Fig. In the embodiment shown in Figure 2, the respective spacer C has a C-profile in a plane spanned by the longitudinal axis X and vertical axis Z. The respective spacer C is, for example, designed as a C-shaped sheet. One upper surface of the C-profile forms the respective connection surface K. The C-profile has the advantage that, for example, compared to cuboid spacers C, weight and material can be saved (see Figure 2). Fig. 2).

[0047] The spacers C are also arranged in the device 100 such that the respective connection surface K is flush with a top surface O of the potting compound M. The top surface O of the potting compound M simultaneously forms a top surface of the device 100. This eliminates the need for a recess A (see Figure 1). Fig. 1 and Fig. 2) in the potting compound M, which in turn allows electronic components to be connected directly to the top surface O of the potting compound M. For example, due to manufacturing tolerances, the respective spacer C may also protrude slightly from the top surface O of the potting compound M, e.g. by 1 mm, so that the associated connection surface K can be arranged in a plane parallel above the top surface O of the potting compound M.

[0048] In Fig. Figure 3 also shows a section through the device 100 in a section plane BB (see Figure 3). Fig. 4 and Fig. 5).

[0049] Fig. Figure 4 shows a schematic representation of another embodiment of a current transformer 200 with a device 100 for the current transformer 200 in the section plane BB. The section plane BB is oriented parallel to a plane spanned by the transverse axis Y and the vertical axis Z.

[0050] In the section plane BB, it can be seen that a conductor layer 2 has several first conductor tracks 21 and several further conductor tracks 22. The first conductor tracks 21 serve to carry a first electrical potential, e.g., a high electrical potential. The further conductor tracks 22, on the other hand, serve to carry a further electrical potential, e.g., a lower electrical potential compared to the first electrical potential. The first and the further conductor tracks 21, 22 are arranged alternately along the transverse axis Y. This reduces parasitic effects within the device 100.

[0051] The spacers C each contact the first conductor tracks 21 with their underside. Each spacer C has a T-profile in the cross-sectional plane BB, such that a contact surface K on one top surface of the respective spacer C at least partially overlaps the corresponding and adjacent conductor tracks 22. The contact surfaces K on the top surface of the respective spacers C can serve as a first DC connection of the device 100. The other conductor tracks 22, on the other hand, can partially protrude from the device 100 and serve as a further DC connection of the device 100. Due to the T-profile, the contact area K is increased in a simple manner, and the overlap also more effectively limits electromagnetic effects between the conductor tracks 21 and 22, which in turn reduces parasitic effects.

[0052] A distance D between the spacer C and the other conductor track 22 can be, for example, two centimeters in the area of ​​overlap. The distance D is oriented, for example, parallel to the vertical axis Z.

[0053] Fig. Figure 5 shows a schematic representation of another embodiment of a current transformer 200 with a device 100 for the current transformer 200 in the section plane BB.

[0054] In contrast to the one in Fig. In the embodiment shown in 4, the spacer C is in Fig. 5 is designed such that it contacts several first conductor tracks 21. The spacer C has a double-T profile in the section plane BB, such that a contact surface K on a top side of the spacer C completely overlaps the further conductor tracks 22 arranged between the first conductor tracks 21. Due to the double-T profile, the size of the contact surface K on the top side of the spacer C is smaller compared to the embodiment in Fig. 4 more than doubled. At the same time, the electromagnetic effects between the further conductor track 22 and the spacer C are further limited due to the closed overlap, which in turn further reduces the parasitic effects within the device 100.

[0055] Furthermore, due to the double-T profile, the conductor tracks 22 adjacent to the left and right are at least partially overlapped by the spacer C.

[0056] Fig. Figure 6 shows a schematic representation of an embodiment of a current transformer 200 with a device 100 for the current transformer 200.

[0057] As opposed to Fig. 3. The left-hand spacer C has an opening L1 in its connection surface K. The opening L1 can be, for example, a circular bore or a cutout. The opening L1 is located opposite a connection point P of the spacer C. This allows, for example, a laser beam L to shine through the opening onto the connection point P in order to bond the spacer C to the first conductor track 21 of conductor layer 2 by laser welding.

[0058] To facilitate positioning and fixing of the spacer C during connection, a further opening L2 is provided in a vertical section of the spacer C. This can also be designed as a circular bore or a cutout. For example, a locking tool of an industrial robot can engage in the further opening L2 to grip the spacer C and position and fix it on conductor layer 2.

[0059] Since the laser welding naturally takes place before the potting compound M is poured, in Fig. 6 the potting compound M not shown.

[0060] Fig. Figure 7 shows a schematic representation of another embodiment of a current transformer 200 with a device 100 for the current transformer 200 in a perspective view.

[0061] In addition to Fig. 5 is in Fig. 7. It can be seen that a spacer C contacts a first conductor track 21 of conductor layer 2 and another spacer C2 contacts another conductor track 22 of conductor layer 2. The spacers C, C2 are designed such that they contact the conductor tracks 21, 22 alternately in a common plane (e.g. the XY plane).

[0062] Here, the spacer C has, for example, a multiple T-profile in the YZ plane, so that the conductor tracks 21, 22 are completely overlapped by a contact surface K of the spacer C - with the previously to Fig. 5 explained advantages.

[0063] The spacer C is in Fig. 7 designed as a C-sheet. However, it should be mentioned that the spacer C can also be several cuboids (cf. Fig. 2) may exhibit so-called power spacers. In this case, one top surface of the cuboid could form the connection surface K.

[0064] The connection surface K can be used, for example, to establish an electrical connection to the negative terminal of a high-voltage battery (not shown) or to an intermediate circuit capacitor (not shown).

[0065] The additional spacer C2 also has a multiple T-profile in the YZ plane, but unlike spacer C, it is designed as a so-called Z-shaped sheet. Spacer C2 is therefore bent in a different direction than spacer C.

[0066] The additional spacer C2 has another connection surface K2, whereby the connection surfaces K and K2 do not overlap due to the bending of the additional spacer C. This simplifies the connection of busbars. For example, an electrical connection to the positive terminal of a high-voltage battery (not shown) or to an intermediate circuit capacitor (not shown) can be made via the additional connection surface K2.

[0067] A distance D2 between the connection surfaces K, K2 (along the vertical axis Z) can be reduced to a constructive minimum, e.g., to a minimum of 3 mm, using spacers C, C2. For example, the distance between the current-carrying busbars (not shown), which electrically connect the device 100 to the DC link capacitor (not shown), can be minimized to the distance D2. This allows parasitic effects to be reduced particularly effectively. Reference symbol list 1 separating layer 2 conductor layer 21 first conductor track 22 more conductor tracks 3 Power semiconductors 4 metal layers 13 Sintered layer 14 Bond wire 100 Device 200 current transformers 300 vehicles A recess BB section plane C spacers C2 further spacer D distance D2 Distance between connection surfaces K Connection surface K2 further connection area L laser beam L1 Opening L2 further opening M potting compound O Top side of the potting compound P connection point X Longitudinal axis Y transverse axis Z vertical axis

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