Power module with shielding layer

Abstract

A power module for an inverter, wherein the power module has several metallic layers (2, 7, 8), comprising at least two DC layers (7, 8) and at least one AC layer (2), wherein the DC layers (7, 8) each have a potential of a DC supply voltage (DC), namely a first potential or a second potential of the DC supply voltage (DC), and the at least one AC layer (2) has a potential of at least one AC output voltage (AC) of the power module, wherein the power module comprises a metallic base plate (1) for dissipating heat from the DC layers (7, 8) and the AC layer (2), wherein at least one shielding layer (3) is arranged between the at least one AC layer (2) and the base plate (1), wherein the at least one shielding layer (3) is electrically connected to a specific potential.wherein the determined potential is electrically symmetrical and thus galvanically isolated from the potentials of the supply DC voltage and the at least one output AC voltage of the power module, so that common-mode currents between the AC layer (2) and the base plate (1) are reduced.

Description

Field of invention

[0001] The present invention relates to a power module for use in an inverter, in particular for supplying power to an electric machine, and to an electrically powered motor vehicle comprising such a power module. State of the art

[0002] It is known that in electric drives, inverters are frequently used to supply the electric machine with the required alternating voltage, especially three-phase alternating voltage. These inverters are fed from direct current sources. They are also called voltage converters, voltage transformers, or converters.

[0003] It is known that in such electric drives, parasitic capacitances can generate unwanted common-mode currents and voltages. These common-mode values ​​can be coupled into system components and cabling via the grounding and housing structure, causing excessive conducted and radiated emissions. This poses, among other things, the risk of EMC (electromagnetic compatibility) interference. Costly mitigation measures are therefore necessary.

[0004] In particular, parasitic capacitances between a voltage-carrying layer of an inverter's power module, especially a semiconductor power module that can accommodate power components with semiconductor elements, and an electrically conductive heat sink of the inverter, together with the heat sink's grounding, can create a path for unwanted common-mode currents along the housing structures of electric drives. This can distribute high-frequency interference throughout the system, which must be countered by costly, bulky, and heavy interference suppression components.

[0005] Furthermore, it is known that common-mode values ​​arising from parasitic capacitances can be reduced by electrical shielding measures.

[0006] From WO 2023 / 222220 A1, shielding measures in semiconductor power modules are known that are galvanically connected to one pole of the DC power supply of the power modules or are formed directly by a layer of the modules that represents one pole of the DC power supply. However, such one-sided shielding can cause further problems, in particular electrical asymmetries with respect to the DC power supply and the grounded inverter housing and the associated common-mode to differential-mode conversions, and therefore do not represent a satisfactory solution to the described interference problem. Summary of the invention

[0007] One object of the invention is to describe a power module that generates fewer common-mode currents in housing structures, thereby reducing the risk of EMC interference, thus enabling a reduction in damage-limiting components, and consequently allowing the electric drive to have lower costs, volume, and weight. A further object of the invention is to provide an electrically powered motor vehicle, comprising at least one drive device configured for propelling the motor vehicle, comprising at least one inverter, and comprising at least one such power module that generates fewer common-mode currents, thereby reducing the risk of EMC interference.

[0008] The problem is solved by a performance module with the features according to claim 1.

[0009] A power module according to the invention has a metallic base plate above which the potentials of the DC supply voltage and at least one AC output voltage of the power module are applied on further insulated layers, wherein the power module is preferably mounted on a metallic heat sink not belonging to the semiconductor power module for heat dissipation from the base plate, wherein a shielding layer is arranged between the base plate and each layer carrying an AC output voltage, wherein the shielding layer is galvanically or capacitively electrically connected to a specific potential, wherein the specific potential is electrically symmetrical with respect to the DC supply voltage and the housing structure of the drive system and is thus galvanically isolated from the potentials of the DC supply voltage and the at least one AC output voltage of the power module.so that common-mode currents to the base plate and heat sink are reduced.

[0010] According to the invention, at least one shielding layer is provided between a metallic, i.e., electrically conductive, base plate, preferably made of copper, which is connected to a grounded heat sink (not belonging to the semiconductor power module) for heat dissipation, and each layer with an AC output voltage of the power module with a high voltage change rate dU / dt. At least one AC voltage connection is arranged on this at least one AC layer and electrically connected to the AC layer, and, depending on the embodiment, at least one power module with semiconductor elements is also located there. Due to the shielding layer, the parasitic capacitance no longer acts directly on the base plate and the grounded heat sink connected to it, but primarily on the shielding layer, from which it can be dissipated in a suitable manner, thereby reducing common-mode currents in grounding and housing structures.

[0011] By introducing a shielding layer connected to a specific potential, an optimized return path for common-mode currents can be created, preferably to the inverter's DC link – bypassing the housing structure. This eliminates or at least drastically reduces common-mode currents along the housing structure of electric drives. Based on this, the required interference suppression components in the drive system can be minimized.

[0012] The shielding layer can be electrically connected to a specific potential that is galvanically isolated from the two potentials of the DC supply voltage and the AC output voltage of the power module, for example via at least one terminal of the shielding layer that is led out of the housing of the semiconductor power module, preferably to a suitable point of the intermediate circuit of the inverter, and / or internally via capacitors, in particular Y-capacitors.

[0013] Preferably, the shielding layer is electrically connected to a specific potential by connecting at least one capacitor between the shielding layer and the first potential of the DC supply voltage, and between the shielding layer and the second potential of the DC supply voltage.

[0014] Alternatively or additionally to capacitors, the at least one shielding layer can be electrically connected to a specific potential via at least one electrical connection of the shielding layer, wherein preferably the at least one electrical connection of the shielding layer is electrically conductively connected to a suitable point of the inverter's intermediate circuit. In this way, an optimized return path for common-mode currents to the intermediate circuit is created.

[0015] The base plate, the surface of the heat sink (which is not part of the semiconductor power module), and the shielding layer preferably form surfaces that lie parallel to each other.

[0016] The AC layer is preferably a metallic layer applied directly onto an insulating layer.

[0017] Preferably, the shielding layer is arranged between two electrically insulating layers, in particular ceramic layers, wherein the two electrically insulating layers are arranged with the shielding layer between the base plate and each AC layer with an output AC voltage of the power module with a high voltage change rate dU / dt.

[0018] Each AC layer with the potential of the power module's output AC voltage can have an output AC voltage terminal. Preferably, two further layers, namely DC layers, have the potentials of the supply DC voltage. These two further layers preferably have DC voltage terminals, namely one of the DC layers having at least one first DC voltage terminal and the other DC layer having at least one second DC voltage terminal. Preferably, the DC layers having the two potentials of the supply DC voltage are arranged laterally on two sides adjacent to the at least one AC layer, preferably in the same plane in the direction normal to the layers.

[0019] In a preferred embodiment, the shielding layer is formed only between the at least one AC layer, which has the potential of the at least one output AC voltage of the power module, and the base plate, and not between the further layers, which have the two potentials of the supply DC voltage, and the base plate. The shielding layer is thus located only in each region associated with a layer having the potential of the at least one output AC voltage.

[0020] In another preferred embodiment, the shielding layer is formed both between each AC layer, which has the potential of the at least one output AC voltage of the power module, and the base plate, and between the further layers, which have the two potentials of the supply DC voltage, and the base plate.

[0021] According to the invention, a drive device can comprise an electric machine and an inverter with at least one semiconductor power module as described above, wherein the inverter serves to supply the electric machine with an alternating voltage, wherein the electric machine comprises a rotor and a stator surrounding the rotor, wherein the stator has a stator core, wherein the stator core comprises a stack of stator laminations and includes windings received by the stack of stator laminations, wherein the stator is received in a housing, wherein the stator is electrically insulated from the housing.

[0022] In order to reduce common-mode currents in a drive device particularly effectively, the stator of the drive motor is isolated from the housing, and each AC layer that has the potential of at least one output AC voltage of the power module is decoupled from the grounded heat sink by a shielding layer, and each shielding layer is also connected to the isolated stator of the drive motor.

[0023] An electrically powered motor vehicle preferably comprises at least one drive device designed to propel the motor vehicle, comprising at least one inverter, comprising at least one power module as previously described. Brief description of the drawings

[0024] The invention is described below by way of example with reference to the drawings. Fig. Figure 1a is a schematic side view of a power module according to the invention. Fig. Figure 1b is a schematic three-dimensional top view of the power module according to Fig. 1a. Fig. 2a and Fig. 2b are schematic views according to Fig. 1a and Fig. 1b of a power module according to the invention in a further embodiment. Fig. 3a and Fig. 3b are schematic views according to Fig. 1a and Fig. 1b of a power module according to the invention in a further embodiment. Fig. 4a and Fig. 4b are schematic views according to Fig. 1a and Fig. 1b of a power module according to the invention in a further embodiment. Fig. 5a and Fig. 5b are schematic views according to Fig. 1a and Fig. 1b of a power module according to the invention in a further embodiment. Fig. 6a and Fig. 6b are schematic views according to Fig. 1a and Fig. 1b of a power module according to the invention in a further embodiment. Detailed description of the invention

[0025] In Fig. 1a and Fig. Figure 1b shows a power module according to the invention of an inverter of a drive device in a first embodiment.

[0026] The power module comprises a metallic AC layer 2, which has the potential of an AC output voltage of the power module. An AC output voltage terminal 6 is arranged on the AC layer 2 and connected to the AC layer 2 by means of a solder joint or other electrical connection 10.

[0027] The power module includes a metallic base plate 1 on its underside, facing away from the output AC voltage connection 6, for heat dissipation and mounting on a heat sink that does not belong to the semiconductor power module.

[0028] Two further layers 7 and 8, namely DC layers exhibiting the potentials of a DC supply voltage, are arranged laterally on two sides adjacent to the AC layer 2. In the illustrated embodiment, the AC layer 2 is located higher than the further layers 7 and 8, in a direction normal to the extent of the layers.

[0029] At the same level as the other layers 7 and 8, a shielding layer 3 is arranged between base plate 1 and AC layer 2. The shielding layer 3 is electrically connected to a specific potential that is electrically symmetrical and thus galvanically isolated from the first potential of the DC supply voltage, the second potential of the DC supply voltage, and the AC output voltage of the power module, so that common-mode currents between base plate 1 and AC layer 2 are reduced.

[0030] The shielding layer 3 is electrically connected to the specified potential via an electrical connection 4 of the shielding layer 3. The electrical connection 4 of the shielding layer 3 can be electrically connected to a suitable point of the intermediate circuit of the inverter.

[0031] The AC layer 2, the base plate 1, and the shielding layer 3 are parallel surfaces or layers. The base plate 1 can, for example, serve to dissipate heat to a surface of a heat sink connected to a cooling device. Base plate 1 and AC layer 2 can be made of copper.

[0032] The shielding layer 3 is arranged between two electrically insulating layers 5, in particular ceramic layers, such that the two electrically insulating layers 5 with the shielding layer 3 are arranged between base plate 1 and AC layer 2.

[0033] In the execution according to Fig. 1a and Fig. 1b the shielding layer 3 is formed only between the AC layer 2, which has the potential of the output AC voltage of the power module, and the base plate 1 and not between the further layers 7, 8, which have the first potential of the supply DC voltage and the second potential of the supply DC voltage, and the base plate 1.

[0034] An insulating layer 5 is arranged between each of the two further layers 7, 8 and the common base plate 1, preferably formed by the same layer that also separates the shielding layer 3 from the base plate 1.

[0035] On each of the two further layers 7, 8, which exhibit the potentials of the DC supply voltage, a vertical power module 12, each with a power terminal on its top and bottom surface and preferably comprising semiconductor elements, is arranged and electrically connected via a soldered connection or other electrical connection 10. The top surfaces of the two power modules 12 are electrically connected to the AC layer 2 via bonding connections 11. A DC supply voltage terminal 9 is also arranged on each of the two DC layers 7, 8.

[0036] The execution according to Fig. 1a and Fig. 1b thus uses an electrical connection 4 of the shielding layer 3 to establish an electrical connection between the shielding layer 3 and a specific, electrically symmetrical potential.

[0037] The electrical connection 4 of the shielding layer 3 can additionally be used to create further EMC-advantageous connections, preferably to an insulated stator of an electrical machine.

[0038] In the Fig. 2a and Fig. In the embodiment shown in Figure 2b, in addition to the electrical connection 4 of the shielding layer 3, two capacitors Cy with the same capacitance values ​​are used between the shielding layer 3 and each of the two further layers 7, 8 to achieve the specific electrically symmetrical potential of the shielding layer 3. The shielding layer 3 is thus electrically connected to the specific potential by connecting at least one capacitor Cy between the shielding layer 3 and the first potential of the DC supply voltage, and between the shielding layer 3 and the second potential of the DC supply voltage.

[0039] The electrical connection 4 of the shielding layer 3, with the electrically symmetrical potential achieved by the two capacitors Cy, can be used to create further EMC-advantageous connections, preferably to an insulated stator of an electrical machine.

[0040] Fig. 3a and Fig. Figure 3b shows an embodiment which, to produce the specific electrically symmetrical potential of the shielding layer 3, uses only two capacitors Cy between the shielding layer 3 and each of the two further layers 7, 8 and has no electrical connection 4 of the shielding layer 3 and thus no module-external electrical connection of the shielding layer 3.

[0041] In the embodiment of the Fig. 4a and Fig. 4b a common shielding layer 3 extends between two insulating layers 5 along the entire power module, namely the base plate 1 on the underside and a sequence of the AC layer 2 and the further layers 7, 8 above the shielding layer 3.

[0042] Thus, the shielding layer 3 is formed both between the AC layer 2, which has the potential of the output AC voltage of the power module and the base plate 1, and between the further layers 7, 8, which have the potentials of the supply DC voltage, and the base plate 1.

[0043] Shielding layer 3 is electrically connected to an electrical connection 4 of shielding layer 3 via a bonding 13 of the shielding layer. Shielding layer 3 is also electrically connected to the two other layers 7 and 8 via capacitors Cy.

[0044] An AC layer 2, which has the potential of the AC output voltage of the power module, is arranged laterally next to two further layers 7, 8, which have the potentials of the DC supply voltage. A vertical power component 12 is arranged and electrically connected to the AC layer 2 via a solder joint or other electrical connection 10 and electrically connected to the further layer 7 on the top side via bonding connections 11.

[0045] The arrangement of layers 2, 7, 8 is in the execution according to Fig. 5a and Fig. 5b is again geometrically symmetrical, such that the AC layer 2, which has the potential of the AC output voltage of the power module, is located in the center, and the two DC layers 7, 8 are arranged to the left and right of the AC layer 2. The AC layer 2, which has the potential of the AC output voltage of the power module, is formed here by an electrically conductive AC rail 14, preferably made of copper, which is supported by angled rail spacings via soldering or other electrical connections with exposed rail pads 15. The AC rail is not isolated here by an electrically non-conductive layer, but rather by spatial separation from the shielding layer 3. This reduces the need for an additional physical insulating layer, and thus eliminates additional manufacturing steps and material costs. The AC output voltage connection 6 is located on the AC rail 14.

[0046] The embodiment accordingly Fig. 6a and Fig. 6b corresponds to the Fig. 5a and Fig. 5b, wherein, however, a lateral power module 12 with power connections located next to each other on its upper side is arranged on each further layer 7, 8. In each case, one power connection of a power module 12 is electrically connected to the AC voltage rail 14 via bonding connections 11, and a second power connection of a power module 12, arranged laterally next to it, is electrically connected to the respective DC voltage layer 7 or 8 via bonding connections 11. Reference symbol list 1 Base plate 2 AC layer 3 Shielding layer 4. Electrical connection of the shielding layer 5 electrically insulating layer 6 AC output terminals 7 DC layer 8 DC layer 9 DC power supply connection 10 Solder layer or other electrical connection 11 Bonding connection 12 Performance module 13 Bonding of the shielding layer 14 AC rail 15 rail pads AC output voltage Cy capacitor DC supply voltage, (first / second) potential of the DC supply voltage

Claims

[1] Power module for an inverter, wherein the power module comprises several metallic layers (2, 7, 8), comprising at least two DC layers (7, 8) and at least one AC layer (2), wherein the DC layers (7, 8) each have a potential of a DC supply voltage (DC), namely a first potential or a second potential of the DC supply voltage (DC), and the at least one AC layer (2) has a potential of at least one AC output voltage (AC) of the power module, wherein the power module comprises a metallic base plate (1) for dissipating heat from the DC layers (7, 8) and the AC layer (2), characterized by, that at least one shielding layer (3) is arranged between the at least one AC layer (2) and the base plate (1), wherein the at least one shielding layer (3) is electrically connected to a specific potential, wherein the specific potential is electrically symmetrical and thus galvanically isolated from the potentials of the supply DC voltage and the at least one output AC voltage of the power module, so that common-mode currents between the AC layer (2) and the base plate (1) are reduced. [2] Power module according to claim 1, characterized by , that at least one shielding layer (3) is electrically connected to the specified potential by connecting at least one capacitor (Cy) between shielding layer (3) and the first potential of the supply DC voltage (DC) and between shielding layer (3) and the second potential of the supply DC voltage (DC). [3] Power module according to any one of the preceding claims, characterized by , that the at least one shielding layer (3) is electrically connected to the determined potential by at least one electrical connection (4) of the shielding layer (3), wherein preferably the at least one electrical connection (4) of the shielding layer (3) is electrically connected to a suitable point of the intermediate circuit of the inverter. [4] Power module according to any one of the preceding claims, characterized by , that the base plate (1), the at least one AC layer (2) and the at least one shielding layer (3) form surfaces parallel to each other. [5] Power module according to any one of the preceding claims, characterized by, that the at least one shielding layer (3) is arranged between two electrically insulating layers (5), in particular ceramic layers, wherein the two electrically insulating layers (5) are arranged with the shielding layer (3) between the base plate (1) and the at least one AC layer (2). [6] Power module according to any one of the preceding claims, characterized by , that the at least one AC layer (2) has the potential of the at least one AC output voltage (AC) of the power module and at least one AC output voltage connection (6) is arranged on the AC layer (2), wherein the two DC layers (7, 8) have the first potential of the DC supply voltage (DC) and the second potential of the DC supply voltage (DC). [7] Power module according to claim 6, characterized by, that the DC layers (7, 8) which have the potentials of the supply DC voltage are arranged laterally on two sides next to the respective AC layer (2), preferably in the same plane. [8] Power module according to claim 6 or 7, characterized by , that the at least one shielding layer (3) is formed only between the at least one AC layer (2), which has the potential of the at least one output AC voltage (AC) of the power module, and the base plate (1), and not between the DC layers (7, 8), which have the potentials of the supply DC voltage (DC), and the base plate (1). [9] Power module according to claim 6 or 7, characterized by, that the at least one shielding layer (3) is formed both between the at least one AC layer (2), which has the potential of the at least one output AC voltage (AC) of the power module, and the base plate (1), and between the DC layers (7,8), which have the potentials of the supply DC voltage (DC), and the base plate (1). [10] Power module according to any one of the preceding claims, characterized by, that the at least one AC layer (2) is not formed by a metallic layer applied directly to an insulating layer, but by at least one metallic AC rail (14), preferably made of copper, which ensures a geometric separation of an upper, substantially planar part of the AC rail (14) from the underlying shielding layer (3) by means of suitably angled parts of the AC rail (14), wherein the angled parts of the AC rail (14) are attached to exposed, and thus electrically insulated, rail pads (15) on the plane of the shielding layer (3), wherein the at least one output AC voltage connection (6) is preferably attached to the AC rail (14) or is formed by a specially shaped part of the AC rail (14). [11] Electrically powered motor vehicle comprising at least one drive device configured to drive the motor vehicle, comprising at least one inverter, comprising at least one power module according to any one of claims 1 to 10.

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