Power switching module for a power inverter

Abstract

The present invention relates to a power switching module for a power inverter in a motor vehicle, comprising a DC voltage section with a positive conductor and a negative conductor, wherein the positive conductor and the negative conductor are arranged on a substrate base and insulated from each other by a gap; an AC voltage section with a copper sheet arranged parallel to the positive and negative conductors; several first power semiconductors that contact the copper sheet with a source terminal and the positive conductor with a drain terminal; several second power semiconductors that contact the copper sheet with a drain terminal and the negative conductor with a source terminal; and a first gate supply terminal arranged in the gap and electrically connected to a gate terminal of the first power semiconductors.to switch an electric current between the positive conductor and the copper sheet, and a second gate supply terminal which is arranged in the gap and is electrically connected to a gate terminal of the second power semiconductor to switch an electric current between the negative conductor and the copper sheet.

Description

State of the art

[0001] The present invention relates to a power inverter and an associated power switching module.

[0002] Silicon carbide (SiC) semiconductor technology has now found its way into the world of automotive inverters. The main advantages of a SiC inverter are the ability to use fast-charging-compatible 800V electrical systems and new possibilities for increasing part-load efficiency through reduced conduction and switching losses. Besides higher manufacturing costs, SiC semiconductors exhibit more difficult-to-control technical characteristics compared to silicon (Si) semiconductors. These particularly affect short-circuit withstand capability, body diode snappyness, and the variation in chip parameters. These characteristics pose problems, especially with regard to short-circuit withstand capability and electromagnetic compatibility (EMC).To meet the requirements for new power inverters for electric vehicles, very low-inductance power switching modules with simultaneously good heat dissipation capabilities are needed, which exhibit the highest possible EMC compliance with high reliability and the most cost-effective manufacturing possible. Disclosure of the invention

[0003] The power switching module according to the invention, comprising the features of claim 1, and the power inverter according to claim 10, have the advantage that the inductance of the power switching module can be reduced by the geometry according to the invention, in order to enable reliable and efficient operation of the power inverter. This is achieved according to the invention by the power switching module having a DC voltage section with a positive conductor and a negative conductor, wherein the positive conductor and the negative conductor are arranged on a substrate base and insulated from each other by a gap. Furthermore, the power switching module has an AC voltage section with a copper sheet arranged parallel to the positive and negative conductors.Between the DC and AC voltage sections, several first power semiconductors are arranged, which contact the copper sheet at a source terminal and the positive conductor at a drain terminal. According to the invention, the first power semiconductors can form a high-side switch. Furthermore, the power switching module has several second power semiconductors, which contact the copper sheet at a drain terminal and the negative conductor at a source terminal. According to the invention, the second power semiconductors can form a low-side switch. The contact between the first power semiconductors with the copper sheet and the positive conductor is preferably made by means of a weld, solder, or sintered connection. Furthermore, the contact between the second power semiconductors with the copper sheet and the negative conductor is also preferably made by means of a weld, solder, or sintered connection.The power switching module also has a first gate supply connection and a second gate supply connection, which are arranged in the gap between the positive and negative conductors. The first gate supply connection is connected to a gate terminal of the first power semiconductor to switch an electric current between the positive conductor and the copper sheet, and the second gate supply connection is connected to a gate terminal of the second power semiconductor to switch an electric current between the negative conductor and the copper sheet. Due to the arrangement of the first and second power semiconductors according to the invention, the positive conductor can be arranged on the same plane as the negative conductor, and the copper sheet of the AC voltage range between the positive and negative conductors can be routed parallel to the DC voltage range.This allows for a compact and as symmetrical a design as possible for the power switching module, resulting in efficient current flow and, in particular, low inductance. The electrical design of the power switching module forms a half-bridge. The substrate is preferably a ceramic substrate. The negative and positive conductors are preferably made of copper sheet. The negative and positive conductors can, in particular, be implemented as a copper coating on the (ceramic) substrate. The first and second gate supply connections can be implemented as conductive traces on the substrate, with the conductive trace being connectable to the gate connections. Alternatively, the first and second gate supply connections can also be implemented as stamped copper parts.The first power semiconductors preferably comprise a maximum of three, and in particular two, first power semiconductors, which are preferably designed as SiC power semiconductors. Furthermore, the power switching module also comprises a maximum of three, and in particular two, second power semiconductors, which are also preferably designed as SiC power semiconductors. The small number of semiconductors reduces the cost and space requirements of the power switching module. For increased power requirements, several power switching modules can be connected in parallel to switch a common phase potential. Parallelizing multiple power switching modules also increases reliability in the event of a failure of one of the power switching modules.

[0004] The dependent claims describe preferred embodiments of the invention.

[0005] Preferably, the power switching module includes a temperature sensor that passes through an opening in the copper sheet and is positioned centrally in the gap. The temperature sensor is preferably a thermistor. This position allows the temperature sensor to be located close to the first and second power semiconductors, and also enables the copper sheet to be cut with minimal impact on the parasitic inductance. The temperature sensor preferably has the same electrical potential as the copper sheet, thus minimizing the requirements for air and creepage distances between the temperature sensor and the copper sheet.

[0006] Preferably, the first and second power semiconductors are arranged parallel to each other along the gap. This allows for a highly symmetrical and compact design of the power semiconductor. This can result in very low parasitic capacitances between the AC voltage range and adjacent components such as a heat sink, while the DC voltage range can act as a parasitic Y-capacitor, forming a small initial EMC filter. Furthermore, the parallel arrangement of the power semiconductors along the gap reduces the inductance of the power switching module.

[0007] The negative conductor, the positive conductor, the gap, the first power semiconductors, and the second power semiconductors preferably extend parallel to a longitudinal axis. This allows for a short current path from the negative conductor to the copper sheet and from the copper sheet to the positive conductor. The current path is essentially perpendicular to the longitudinal axis. The first and second power semiconductors can preferably be scaled along the longitudinal axis, perpendicular to the current path. This allows thermal hotspots to be further separated on larger chip areas, thereby improving thermal impedance.

[0008] The DC voltage section, the AC voltage section, the first power semiconductors, and the second power semiconductors are preferably arranged symmetrically about a first plane and a second plane, the first plane being perpendicular to the second plane. The first plane is preferably an XZ plane and the second plane an YZ plane, with the base lying in an XY plane. This geometric symmetry of the power switching module can result in a symmetrical and uniform current flow and a reduced inductance of the power switching module.

[0009] The power switching module preferably comprises a first busbar that contacts the positive conductor and a second busbar that contacts the negative conductor. The first busbar is arranged parallel to and overlapping with the second busbar. This parallel overlapping arrangement of the first and second busbars enables the lowest possible inductive contact between the positive and negative conductors, allowing the power switching module to be switched quickly without risk of high transient voltages being induced. The first and second busbars preferably also completely overlap the negative and positive conductors.

[0010] The power switching module preferably comprises a metallic body and a phase bus, wherein the phase bus contacts the copper sheet via the metallic body. The metallic body acts as a thermal capacitor and can increase the thermal time constant of the power switching module to meet the thermal requirements during short peak loads. The metallic body is preferably made of copper. More preferably, the power switching module has several metallic bodies that electrically contact the phase bus with the copper sheet. A hole for the temperature sensor is preferably arranged centrally in the metallic body.

[0011] The power switching module preferably includes a heat sink arranged on one side of the substrate opposite the base, with the phase busbar in contact with the heat sink. This allows heat to be easily dissipated from the phase busbar to the heat sink. Furthermore, this allows thermal losses from the electric motor connected to the phase busbar to be dissipated.

[0012] According to a further preferred embodiment of the invention, the power switching module preferably comprises a first source Kelvin supply terminal and a second source Kelvin supply terminal arranged in the gap. The first source Kelvin supply terminal is connected to a source Kelvin terminal of the first power semiconductors and, together with the first gate supply terminal, switches an electrical current between the positive conductor and the copper sheet. The second source Kelvin supply terminal is electrically connected to a source Kelvin terminal of the second power semiconductors and, together with the second gate supply terminal, switches an electrical current between the negative conductor and the copper sheet. This enables low-inductance and reliable switching of the power switching module. The first power semiconductors are preferably switched synchronously.Furthermore, the second power semiconductors are preferably also switched synchronously.

[0013] Furthermore, the invention relates to a power inverter for a motor vehicle, wherein the power inverter comprises at least one power switching module according to one of the preceding claims for controlling an electric motor. With the aid of the power switching module described above, the power inverter can be designed to be compact and cost-effective, and enables fast and efficient control of the electric motor.

[0014] Preferably, several power switching modules of the power inverter are connected in parallel to switch a common phase potential. This allows the power inverter to be easily adapted to the power requirements by adjusting the number of power switching modules. Furthermore, multiple parallel-connected power switching modules can increase the failure probability of the power inverter, as a failed power switching module can be easily replaced. The power inverter preferably switches three phase potentials, with each phase potential having at least one power switching module.

[0015] A preferred embodiment of the invention is described in detail below with reference to the accompanying drawings. The drawing shows: Fig. 1 a perspective view of a power switching module according to a preferred embodiment of the invention, Fig. 2 a side view of a power inverter with the power switching module according to the preferred embodiment of the invention and Fig. 3 a perspective view of the power inverter with the power switching module according to the preferred embodiment of the invention Embodiments of the invention

[0016] Preferably, all identical components, elements and / or units in all figures are provided with the same reference numerals.

[0017] The following refers to the Fig. 1, Fig. 2 to Fig. 3 a power switching module 1 and a power inverter 100 described in detail.

[0018] Fig. Figure 1 shows the power switching module 1, which is designed as a half-bridge to convert a DC voltage from an intermediate circuit capacitor into an AC voltage for an electric motor. The DC voltage is applied to a DC voltage range 10, which is formed by a positive conductor 11 and a negative conductor 12. The positive conductor 11 and the negative conductor 12 are electrically isolated from each other by a gap 13. The positive conductor 12 and the negative conductor 11 are formed as copper plates arranged on a base 2 of a substrate 3. The positive conductor 11, the negative conductor 12, and the substrate 3 can, for example, be designed as a direct-bonded copper structure.

[0019] Three first power semiconductors 31 are arranged on the positive conductor 11. The first power semiconductors 31 are arranged parallel to the gap 13 and extend along a longitudinal axis XX. The first power semiconductors 31 are preferably designed as silicon carbide MOSFET semiconductors. The positive conductor 11 is contacted by the first power semiconductors via a drain terminal 34. This contact is preferably made by soldering, welding, or sintering. On a side opposite the drain terminal 34 of the first power semiconductors 31, the first power semiconductors 31 are connected to a copper sheet 21 via a source terminal 33. The connection of the first power semiconductors 31 to the copper sheet 21 via the source terminal 33 is also preferably made by soldering, welding, or sintering.

[0020] The gap 13 extends linearly along a longitudinal axis XX between the negative conductor 12 and the positive conductor 11. The negative conductor 12 and the positive conductor 11 have a rectangular shape extending in the direction of the longitudinal axis XX. The dimensions of the positive conductor 11 and the negative conductor 12 are essentially identical.

[0021] Three secondary power semiconductors 32, preferably silicon carbide MOSFET semiconductors, are also arranged on the negative conductor 12. Unlike the first power semiconductors 31, the secondary semiconductors 32 are attached to the copper sheet 21 via their drain terminal 34. The source terminal 33 of the secondary power semiconductors 31 is connected to the negative conductor 12 on the side opposite the drain terminal 34. The connections between the copper sheet 21, the secondary power semiconductors 32, and the negative conductor 12 are also preferably formed by welding, soldering, or sintering.

[0022] The copper sheet 21 is arranged parallel to the negative conductor 12 and the positive conductor 11 above the gap 13 and connects the first power semiconductors 31 and the second power semiconductors 32. Thus, an electric current can flow from the negative conductor 12 through the second power semiconductors 32 to the copper sheet 21 and from there through the first power semiconductors 31 to the positive conductor. Preferably, however, the current flows from a negative conductor 12 of a first power switching module 1 via an AC voltage range 20 with the copper sheet 21 to an electric motor and from there back to another power switching module of the power inverter 100.

[0023] To switch an electric current between the positive conductor 11 and the copper sheet 21, the power switching module 1 has a first gate supply terminal 35, which is arranged in the gap 1 and is electrically connected to a gate terminal 37 of the first power semiconductor 31. To switch an electric current between the negative conductor 12 and the copper sheet 21, the power switching module 1 has a second gate supply terminal 36, which is arranged in the gap 12 and is electrically connected to the gate terminal 37 of the second power semiconductor 32.

[0024] Parallel to the first gate supply terminal 35, the power switching module 1 has a first source Kelvin supply terminal 41, which is also arranged in the gap 13 and is electrically connected to a source Kelvin terminal 43 of the first power semiconductors 31 in order to switch an electrical current between the positive conductor 11 and the copper sheet 21 together with the first gate supply terminal 35. Furthermore, the power switching module 1 has a second source Kelvin supply terminal 42, which is arranged in parallel to the second gate supply terminal 36 in the gap 13 and is electrically connected to a source Kelvin terminal 43 of the second power semiconductors 32 in order to switch an electrical current between the negative conductor 12 and the copper sheet 21 together with the second gate supply terminal 36.The first and second gate supply terminals 35, 36 and source Kelvin supply terminals 41, 42 are further preferably electrically connected to a control unit to switch the power switching module 1.

[0025] The source Kelvin terminals 43 and the gate terminals 37 are arranged next to the first power semiconductors 31 on the positive conductor 11 and next to the second power semiconductors 32 on the negative conductor 12. The gate terminals 37 and source Kelvin terminals 43 are electrically contacted by means of wire bonds.

[0026] A temperature sensor 5, designed as a thermistor, is arranged centrally in the power switching module 1. The temperature sensor 5 is positioned through an opening 24 in the copper sheet 21 and extends perpendicular to the base surface 2. The temperature sensor 5 is located in the gap 13 on the first source Kelvin supply terminal 41 and is at the electrical potential of the source Kelvin supply terminal 41.

[0027] The power switching module 1 exhibits a high degree of symmetry, wherein the DC voltage range 10, the AC voltage range 20, the first power semiconductors 31, and the second power semiconductors 31 are arranged symmetrically about a first plane and a second plane, the first plane being perpendicular to the second plane. The first plane and the second plane are oriented perpendicular to the base 2, with the first plane lying on the longitudinal axis XX.

[0028] Fig. Figure 2 shows a side view of the power switching module 1. Fig. 1, wherein the substrate 3 is arranged on a heat sink 4 on one side opposite the base surface 2. The heat sink 4 is preferably a fluid cooler and can efficiently dissipate heat from the power switching module 1.

[0029] The positive conductor 11, the negative conductor 12, and the copper sheet 21 are each contacted with metallic solids 22, which efficiently conduct the electrical current in the power switching module 1 and have a high heat capacity. The metallic solids 22 are preferably connected to the respective electrical conductors by soldering, welding, or sintering.

[0030] A first busbar 14 is arranged parallel to the base 2 and contacts the positive conductor 11 by means of the metallic volume 22. Furthermore, the power switching module 1 has a second busbar 15, which is arranged parallel to the first busbar 14 and electrically contacts the negative conductor 12 by means of the metallic volume 22. The first busbar 14 is electrically insulated from the second busbar 15.

[0031] The first busbar 14 is arranged parallel and overlapping with the second busbar 15. This enables the lowest possible inductance transfer of an electric current from a DC link capacitor to the power switching module 1, thus ensuring efficient and reliable operation of the power switching module 1.

[0032] Furthermore, the power switching module 1 has a phase bus 23, which contacts the copper sheet 21 via the metallic body 22. The phase bus 23 is configured to electrically connect the power switching module 1 to an electric motor to supply it with electrical power. The phase bus 23 is also arranged parallel to the base 2. The increased distance between the phase bus 23 and the heat sink 4 reduces parasitic capacitances, thereby improving the EMC characteristics of the power switching module 1.

[0033] Fig. Figure 3 shows a perspective view of the power inverter 10 with the power switching module 1. Fig.2. The figure shows how the phase busbar 23 is guided towards the heat sink 4 to make contact with it and dissipate heat. The phase busbar 23 is electrically insulated from the heat sink 4 to prevent voltage breakdowns.

[0034] The first busbar 14 and the second busbar 15 completely overlap and also overlap the base area 2 of the substrate 3. Openings are provided in the first busbar 14 and the second busbar 15 through which the first gate supply connection 35, the second gate supply connection 36, the first source Kelvin supply connection 41, and the second source Kelvin supply connection 42 are routed to the gap 14. The openings in the first busbar 14 and the second busbar 15 provide sufficient clearance and creepage distances.

[0035] The metallic volume body 22 and the phase busbar 23 contacted thereon also have an opening for the temperature sensor 5, in order to further arrange it through the opening 24 in the copper sheet 21 centrally in the gap 13, in order to detect the temperatures of the power semiconductors 31, 32 as directly as possible.

[0036] In parallel to the power switching module 1, 4 further power switching modules can be arranged on the heat sink to control an electric motor. Several power switching modules 1 can be connected to a common phase bus 23 to switch a common phase potential, or they can be connected to different phase potentials using their own phase bus bars.

[0037] The DC voltage ranges 10 of the further power switching modules 1 can be contacted via the common first busbar 14 and second busbar 15 in order to electrically connect the power switching modules 1 to an intermediate circuit capacitor.

[0038] Thus, a power switching module 1 can be provided which features a low-inductance and EMC-compliant design with a simple structure and good thermal properties. In particular, the illustrated power switching module can achieve an inductance of less than 3.5 nH. The high geometric symmetry of the components of the power switching module can lead to a high electrical symmetry of the current flow, so that the components are loaded evenly and no complex fine-tuning of the power switching module is necessary. Furthermore, the power switching module requires a small footprint 2 on the substrate 3 and can be made very flat, so that the power switching modules 1 can be easily integrated into a power inverter 100.

Claims

[1] Power switching module for a power inverter (100) in a motor vehicle, comprising - a DC voltage area (10) with a positive conductor (11) and a negative conductor (12), wherein the positive conductor (11) and the negative conductor (12) are arranged on a base surface (2) of a substrate (3) insulated from each other by a gap (13), - an alternating voltage range (20) with a copper sheet (21) arranged parallel to the positive conductor (11) and the negative conductor (12), - several first power semiconductors (31) which contact the copper sheet (21) with a source terminal (33) and the positive conductor (11) with a drain terminal (34), - several second power semiconductors (32) which contact the copper sheet (21) with the drain terminal (34) and the negative conductor (12) with the source terminal (33), - a first gate supply terminal (35) which is arranged in the gap (13) and is electrically connected to a gate terminal (37) of the first power semiconductors (31) to switch an electric current between the positive conductor (11) and the copper sheet (21), and - a second gate supply terminal (36) which is arranged in the gap (13) and is electrically connected to a gate terminal (37) of the second power semiconductor (32) to switch an electric current between the negative conductor (12) and the copper sheet (21). [2] Power switching module according to claim 1, comprising a temperature sensor (5), in particular a thermistor, which is guided through an opening (24) in the copper sheet (21) and is arranged centrally in the gap (13). [3] Power semiconductors according to any of the preceding claims, wherein the first power semiconductors (31) and the second power semiconductors (32) are arranged parallel to each other along the gap (13). [4] Power switching module according to one of the preceding claims, wherein the negative conductor (12), the positive conductor (11), the gap (13), the first power semiconductors (31) and the second power semiconductors (32) extend parallel to a longitudinal axis (XX). [5] Power switching module according to one of the preceding claims, wherein the DC voltage range (10), the AC voltage range (20), the first power semiconductors (31) and the second power semiconductors (32) are arranged symmetrically to a first plane and to a second plane, the first plane being arranged perpendicular to the second plane. [6] Power switching module according to one of the preceding claims, comprising a first busbar (14) contacting the positive conductor (11) and a second busbar (15) contacting the negative conductor (12), wherein the first busbar (14) is arranged parallel overlapping with the second busbar (15). [7] Power switching module according to one of the preceding claims, comprising a metallic volume body (22) and a phase busbar (23), wherein the phase busbar (23) contacts the copper sheet (21) by means of the metallic volume body (22). [8] Power switching module according to claim 7, comprising a heat sink (4) arranged on one side of the substrate (3) opposite the base (2), wherein the phase busbar (23) contacts the heat sink (4). [9] Power switching module according to one of the preceding connections, comprising a first source Kelvin supply terminal (41) arranged in the gap (13) and electrically connected to a source Kelvin terminal (43) of the first power semiconductors (31) to switch an electric current together with the first gate supply terminal (35) between the positive conductor (11) and the copper sheet (21), and a second source Kelvin supply terminal (42) arranged in the gap (13) and electrically connected to a source Kelvin terminal (43) of the second power semiconductors (32) to switch an electric current together with the second gate supply terminal (36) between the negative conductor (12) and the copper sheet (21). [10] Power inverter for a motor vehicle, wherein the power inverter (100) comprises at least one power switching module (1) according to any of the preceding claims for controlling an electric motor. [11] Power inverter according to claim 10, wherein several power switching modules (1) are connected in parallel to switch a common phase potential.

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