Power module for a converter with shielding-optimized signal pins, converter, electric axle drive and vehicle

Abstract

Power module (10) for a converter for use in an at least partially electrified vehicle, wherein the power module (10) has one or more power switches (12, 12a-b) which are switchable for converting an input current into an output current and are mounted on a circuit carrier (29), wherein the power module (10) has a printed circuit board (31) which is equipped with components of a control device (30, 30a-b) for generating control signals, wherein the power module (10) has a plurality of signal pins (22, 22a-b) for transmitting the control signals to the control electrodes (122) of the power switches (12, 12a-b), wherein the power module (10) has a shielding jacket (24a-b) which encloses at least one of the signal pins (22, 22a-b) at least in sections, wherein a sheet metal element (28) is arranged between the power switches (12, 12a-b) and the circuit board (31), which is electrically connected to the shielding jacket (24a-b).

Description

[0001] The invention relates to a power module for a converter for use in an electrified vehicle, i.e., an electric vehicle or a hybrid vehicle. Furthermore, the invention relates to an electric axle drive comprising such a power module and a vehicle comprising such an electric axle drive.

[0002] Purely electric vehicles and hybrid vehicles are known in the prior art, which are powered exclusively or with support by one or more electric motors as drive units. Such electrified vehicles typically use a rechargeable vehicle drive battery that provides a direct current (DC voltage) to power the electric motors. To this end, the DC voltage is converted into an alternating current (AC voltage) by a DC / AC inverter in order to supply the electric motors with a multiphase alternating current (AC current).

[0003] The core component of such converters is a power electronics unit comprising a plurality of power switches. These power switches are interconnected to create a half-bridge arrangement comprising one or more half-bridges. Each half-bridge consists of a high-side device and a low-side device, each of which has one or more parallel-connected power switches. Each power switch comprises a positive-pole current electrode (e.g., drain electrode), a negative-pole current electrode (e.g., source electrode), and a control electrode (e.g., gate electrode).

[0004] For voltage conversion, the circuit breakers are switched in a targeted manner. To switch a circuit breaker, control signals are impressed on the circuit breaker's control electrode. The control signals are transmitted via a control path that connects a control device to the control electrode. In the power modules known from the prior art, signal pins are used for this purpose. Each of these pins is electrically connected to a control electrode on the one hand and to a circuit board that contains the components of the control device on the other. Such power modules are known, for example, from DE 10 2010 014 940 A1.

[0005] However, the known power modules have the disadvantage that the design of the signal pin arrangement results in a high coupling inductance between the control path (e.g., gate loop) and the load path (e.g., source loop), so that electromagnetic fields induced by the time-varying load current easily couple into the control path. This leads to parasitic effects such as parasitic turn-on (PTO) and exceeding the safety operating areas of the power switches, particularly during switching operations of the power switches, and poses a high risk of impairment for the entire converter.

[0006] It is an object of the invention to provide a power module for a converter in which the disadvantages described above are at least partially eliminated.

[0007] This object is achieved according to the invention by the power module, the converter, the electric axle drive, and the vehicle according to the independent patent claims. Advantageous embodiments and further developments of the invention are set forth in the dependent patent claims.

[0008] The invention relates to a power module for a converter for operating an electric axle drive in an at least partially electrified vehicle, such as an electric vehicle and / or hybrid vehicle. The converter is, for example, a DC / AC inverter. In this case, the input current is a DC current provided by a DC voltage source, such as a rechargeable vehicle drive battery, and the output current is an AC current with multiple phase currents. Alternatively, the converter is designed as an AC / DC rectifier, for example to recharge the vehicle drive battery. For this purpose, an AC input voltage provided by an AC voltage supply (e.g., charging station) is converted via the AC / DC rectifier into a DC output voltage, which can then be fed to the vehicle drive battery.Alternatively, the converter is used as a DC / DC converter to adapt a DC input voltage to the DC operating voltage (nominal voltage) of the vehicle drive battery, for example, to increase it from 400V to 800V.

[0009] The power module comprises at least one power switch, preferably a plurality of power switches, for feeding the input current and for generating the output current based on the fed-in input current by switching the power switches. In the case of a multi-phase DC / AC inverter, the entire power electronics comprises a plurality of (for example, three) phases, each having a half-bridge. Each phase or half-bridge serves to convert the fed-in DC current into a phase current by switching the associated power switches. The plurality of phase currents generated in this way are phase-shifted from one another and are each fed into a winding of the electric motor to supply current to the electric axle drive. The half-bridges each have a high side with a higher electrical potential and a low side with a lower electrical potential.In the case of a multi-phase AC / DC rectifier, the entire power electronics also comprises several (for example three) phases, with the power switches being switched to cancel the phase offsets between the phase currents of the injected AC current, resulting in a DC current at the output.

[0010] Various configurations of the power module are conceivable. For example, the power module can be designed as a so-called half-bridge module, which has a module highside and a module lowside, each with a single power switch or several power switches connected in parallel. In this case, each phase of the entire converter can comprise a single half-bridge module or several half-bridge modules connected in parallel. In the former case, the highside of the phase is formed by the module highside and the lowside of the phase is formed by the module lowside of the single half-bridge module. In the latter case, the highside of the phase is formed by a parallel connection of the module highsides of the parallel-connected half-bridge modules, with the lowside of the phase being formed by a parallel connection of the module lowsides of the parallel-connected half-bridge modules. Alternatively, the power module can comprise only one module highside or one module lowside.The case where the power module has a single power switch occurs, for example, when the module highside or the module lowside comprises only a single power switch. Alternatively, the power module can refer to the entirety of the parallel-connected half-bridge modules of a phase, or to the entirety of the parallel-connected module highsides or module lowsides of a phase.

[0011] The power switches are preferably transistors, such as MOSFETs and / or IGBTs. The semiconductor material underlying the power switches is preferably silicon or a so-called wide bandgap semiconductor (WBC), such as silicon carbide, gallium nitride, or gallium oxide. The power switches are also preferably mounted on a circuit carrier, e.g., a printed circuit board (PCB), or a multilayer ceramic substrate, at least partially coated with a metal (e.g., copper), such as direct-bonded copper (DBC), direct-plated copper (DPC), or active metal bonding (AMB). The power switches are preferably arranged on a first metal layer of the circuit carrier, with a second metal layer of the circuit carrier being connected to a cooler. An insulation layer is preferably arranged between the first metal layer and the second metal layer.

[0012] The power switches each comprise a positive-pole or controlled current electrode (e.g., drain electrode), a negative-pole or reference-potential current electrode (e.g., source electrode), and a control electrode (e.g., gate electrode). The positive-pole current electrode and the negative-pole current electrode, together with the semiconductor structure located between them, form a load path of the respective power switch, through which the load current flows when the power switch is open (conducting). To feed the input current (load current) into the power module or to draw the output current from the power module, several power terminals are provided in the power module; these terminals are electrically connected to the current electrodes of the respective power switch.The power connections are connected to busbars to enable current flow to other components of the converter, such as a DC link capacitor or an external unit such as the windings of the electric motor to be powered in the case of a DC / AC inverter. Current flow within the power module, for example, between the individual power switches, is achieved using multiple power lines, which are, for example, designed as wire bonds or integrated into a lead frame.

[0013] Several signal pins are provided for transmitting control signals to the control electrodes or gate electrodes of the power switches in the power module. The signal pins are electrically connected, on the one hand, to the circuit carrier (in particular to the control electrodes or gate electrodes) and, on the other hand, to a printed circuit board (e.g., driver board) equipped with a control device (e.g., gate driver). According to the invention, the signal pins are at least partially enclosed by a shielding jacket for electromagnetic shielding. Several signal pins, which are enclosed by the same shielding jacket, can be assigned to each shielding jacket. Electrical insulation can be provided between the shielding jacket and the signal pins in order to reduce the minimum clearance and creepage distances required for effective potential isolation and thus to reduce the stray inductance of the power module.In this way, a low-inductance power module can advantageously be achieved.

[0014] Additionally, a sheet metal element is arranged between the power breakers and the circuit board or driver board, which is electrically connected to the shielding jacket and is therefore equipotential. According to a preferred embodiment, the sheet metal element is mounted between the circuit board and several busbars. The shielding jacket enclosing the signal pins and the sheet metal element arranged below the circuit board and equipotential with the shielding jacket serve, in combination, to shield the signal lines represented by the signal pins against electromagnetic interference induced in the area of ​​the signal lines by the load currents of the power breakers. Depending on the coupling factor, a positive or negative voltage is induced in the signal pin, which leads to parasitic effects such as parasitic turn-on (PTO) or to exceeding the safety operating area (SOA).Such parasitic effects, which also increase with the switching speed of the power switches, impair the functionality of the power electronics and thus of the entire converter. The provision of shielding advantageously counteracts such parasitic effects. In particular, the entire control path of the electrodes connected to the signal pins between these and the circuit board is completely electromagnetically shielded, thus better reducing or even eliminating parasitic effects.

[0015] At the same time, the sheet metal element and thus also the shielding jacket can be connected to a reference potential. This can be achieved, for example, by connecting the shielding jacket and / or the shielding sheet metal element to a housing potential of the power module, with the housing potential providing the reference potential.

[0016] According to a further embodiment, at least one of the signal pins for transmitting control signals to a control electrode of an auxiliary switch separate from the power switches is accommodated in the secondary circuit board. The auxiliary switch is an electronic switch that is not a high-side or low-side switch of a half-bridge. It can be an active Miller clamping (ACM) auxiliary switch, a current sensor auxiliary switch, a temperature sensor auxiliary switch, a short-circuit protection auxiliary switch, or another auxiliary switch. Several signal pins, each for an auxiliary switch, can be integrated into the secondary circuit board. In this way, a signal connection can be established between at least one auxiliary switch and the primary circuit board or driver board via the secondary circuit board. A separate signal routing for the auxiliary switch can be dispensed with, which favors a more compact design of the converter.

[0017] The invention further relates to a converter with a power module according to one of the embodiments described here, a corresponding electric axle drive comprising such a converter, and a vehicle with such an electric axle drive. As described above, the converter can have a DC / AC inverter, an AC / DC rectifier, or a DC / DC converter, whereby the invention is not limited to these purely exemplary converter designs, but can generally be used in semiconductor-based power electronics. This results in the advantages already described in connection with the power module according to the invention also for the converter according to the invention, the electric axle drive according to the invention, and the vehicle according to the invention.

[0018] The invention is explained below by way of example with reference to embodiments shown in the figures.

[0019] They show: Fig. 1 a schematic representation of a power module in a side view, wherein the power module has a plurality of shielding jackets, each enclosing at least one signal pin, wherein a sheet metal element connected to the shielding jackets is arranged between a printed circuit board and a plurality of power switches of the power module; Fig. 2 a schematic representation of the power module according to a further embodiment in a perspective view, wherein three signal pins are assigned to each shielding sheath; Fig. 3 a schematic representation of the shielding jacket and the sheet metal element in a perspective view; Fig. 4 a schematic representation of the power module from Fig. 2 in a sectional view; Fig. 5 a schematic representation of the power module from Fig. 2 in a side view; Fig. 6 a schematic circuit diagram of a power module according to another embodiment.

[0020] Identical objects, functional units, and comparable components are designated by the same reference symbols throughout the figures. These objects, functional units, and comparable components are identical in terms of their technical features, unless explicitly or implicitly stated otherwise in the description.

[0021] Fig. 1 shows a schematic representation of a power module 10 according to one embodiment in a side view. The power module 10 is designed for use as a converter for operating an electric axle drive in an at least partially electrified vehicle, such as an electric vehicle and / or hybrid vehicle. The converter can be designed as a DC / AC inverter, AC / DC rectifier, or DC / DC converter.

[0022] The power module 10 comprises at least one circuit breaker 12a-b (see Fig. 2), preferably a plurality of power switches 12a-b, for feeding in an input current and for generating an output current based on the fed-in input current by switching the power switches 12a-b. In the case of a multi-phase DC / AC inverter, the entire power electronics comprises a plurality of (for example, three) phases, each having a half-bridge. Each phase or half-bridge serves to convert the fed-in DC current into a phase current by switching the associated power switches 12a-b, wherein the plurality of phase currents generated thereon are phase-shifted from one another and are each fed into a winding of the electric machine to supply current to the electric axle drive. The half-bridges each have a high side with a higher electrical potential and a low side with a lower electrical potential. As in Fig. 2 schematically and by way of example, at least one line switch 12a is assigned to the high side and at least one circuit breaker 12b is assigned to the low side.

[0023] The power switches 12a-b are preferably transistors, such as MOSFETs and / or IGBTs. The power switches 12a-b are also preferably mounted on a circuit carrier 29 (see Fig. 2), e.g., a printed circuit board (PCB), or a multilayer ceramic substrate, at least partially coated with a metal (e.g., copper), such as direct-bonded copper (DBC), direct-plated copper (DPC), or active metal bonding (AMB). Preferably, the power switches 12a-b are arranged on a first metal layer of the multilayer circuit carrier 29, wherein a second metal layer of the circuit carrier 29 is connected to a cooler 25 or a top side 252 of the cooler 25 by means of a thermally conductive layer 27, such as a sintered or soldered layer. An insulation layer is preferably arranged between the first metal layer and the second metal layer. The cooler 25 can, as in Fig. 1 purely by way of example and shown schematically, have a pin-fin structure 254 in order to increase the area that can be acted upon by the cooling medium (e.g. water) and thus increase the cooling performance.

[0024] The power switches 12a-b each comprise a positive-pole or controlled current electrode (e.g. drain electrode) 126, a negative-pole or reference-potential current electrode (e.g. source electrode) 124 and a control electrode (e.g. gate electrode) 122 (see schematic diagram in Fig. 6). The positive-pole current electrode 126 and the negative-pole current electrode 124, together with the semiconductor structure located therebetween, form a load path of the respective power switch 12a-b, through which the load current flows when the power switch 12a-b is open (conductive). To feed the input current (load current) into the power module 10 or to draw the output current from the power module 10, several power terminals 14, 16, 18 are provided in the power module 10, which are electrically connected to the current electrodes 126, 124 of the respective power switch 12. The power terminals 14, 16, 18 are, in the case of a DC / AC inverter, as in Fig. 1, as shown by way of example, as positive-pole DC power connections 16, negative-pole DC power connections 14, and AC power connections 18. In addition, the power connections 14, 16, 18 are connected to corresponding busbars 13, 15, 17 in order to enable current conduction to other components of the converter, such as an intermediate circuit capacitor in the case of a DC / AC inverter, or an external unit such as the windings of the electric motor to be powered. The positive-pole DC power connections 16 are electrically connected to positive-pole DC busbars 15, with the negative-pole DC power connections 14 being electrically connected to negative-pole DC busbars 13, and the AC power connections 18 being electrically connected to AC busbars 17. An insulating layer 19 is arranged between the positive-pole DC busbars 13 and the negative-pole DC busbars 15 for the purpose of potential separation.The current is carried within the power module 10, for example between the individual power switches 12a-b, by means of several power lines, which are designed, for example, as wire bonds or integrated in a lead frame.

[0025] The circuit breakers 12a-b are, as in Fig. 1, preferably covered with a current-insulating material. The protective covering 11 is formed, for example, by encapsulating or overmolding the circuit breaker together with the circuit carrier 29 and the power terminals 14, 16, 18, wherein a contact surface of the respective power terminals 14, 16, 18, accessible from the outside of the protective covering or protective encapsulation compound or protective overmolding, is exposed from the current-insulating material.

[0026] In addition, the power module 10 comprises a circuit board 29, which is equipped with electrical and / or electronic components of a control device 30a-b for generating control signals for switching the power switches 12a-b. The circuit board 29 can be designed as a circuit board, in particular a driver board. Preferably, the circuit board 29 extends in a plane substantially parallel to the circuit carrier 29. As shown in Fig. 1, a first control device 30a is assigned to the high side of a half-bridge, while a second control device 30b is assigned to the low side of the half-bridge. The first control device 30a is therefore configured to control the high-side power switch 12a, while the second control device 30b is configured to control the low-side power switch 12b.

[0027] The power module 10 has a plurality of signal pins 22a-b for transmitting the control signals to the power switches 12a-b. The signal pins 22a-b are electrically connected to the circuit carrier 29 on the one hand and to the printed circuit board 29 on the other. A first signal pin 22a is electrically connected to a control electrode (e.g., gate electrode) 122 of the high-side power switch 12a, and a second signal pin 22b is electrically connected to a control electrode (e.g., gate electrode) 122 of the low-side power switch 12b. The signal pins 22a-b are each enclosed by a shielding jacket 24a-b to shield the signal pins 22a-b from electromagnetic interference attributable to the load path of the respective power switch 12a-b. In addition, a shielding sheet metal element 28 is arranged between the circuit board 31 and the circuit breakers 12a-b, which is connected to the shielding sheaths 24a-b.The combination of the shielding shells 24a-b and the sheet metal element 28 is shown in . Fig. 3 is shown purely as an example. As in Fig. 1 purely schematically, the sheet metal element 28 is preferably arranged here between the circuit board 31 and the busbars 13, 15, 17 and extends horizontally over the entire length of the circuit board 31.

[0028] Fig. 2-5 show the power module 10 according to a further embodiment. For reasons of clarity, the printed circuit board or driver board 31 is not shown here. Three signal pins 21a-b, 22a-b, and 23a-b are each encased in the shielding jacket 24a of the high side and the shielding jacket 24b of the low side, for example. The signal pins 21ab, 22a-b, and 23a-b extend into the respective shielding jacket 24a-b via an opening 242 and protrude from the shielding jacket 24ab on the circuit board side, as well as from the shielding sheet metal element 28 via recesses formed in the shielding sheet metal element 28 in order to be contacted on the top side. This is shown in Fig. 4. The assignment of the signal pins 21a-b, 22a-b, and 23a-b to the power switches 12a-b can be configured as desired. For example, a first signal pin 22a-b can be connected to a control electrode (e.g., gate electrode) 122 of a power switch 12a-b, a second signal pin 23a-b can be connected to a control electrode (e.g., gate electrode) 132 of an auxiliary switch 130, and a third signal pin 21a-b can be connected to a negative-pole current electrode (e.g., source electrode) 124 of the power switch 12a-b.

[0029] In the schematic diagram in Fig. Figure 6 shows the interconnection of the power switch 12, the auxiliary switch 130 (designed here purely by way of example and without limitation for the present invention as an ACM auxiliary switch or clamping switch), the signal pins 21, 22, 23, and the control device 30 in the power module 10. For reasons of clarity, only one power switch 12 is shown here, which in principle can be a high-side power switch or a low-side power switch. The ACM auxiliary switch 130 serves to short-circuit the control electrode or gate electrode 122 with the negative-pole current electrode or source electrode 124 of the power switch 12 when a predefined threshold of the load current flowing from the positive-pole current electrode or drain electrode 126 to the negative-pole current electrode or source electrode 124 is exceeded.The control device 30 is preferably designed as a gate driver and comprises a first driver module 302 for generating control signals (gate signals) for the power switch 12. In addition, the control device 30 or the gate driver comprises a second driver module 304 for generating control signals (gate signals) for the auxiliary switch or ACM auxiliary switch 130. Furthermore, a positive voltage supply (VDD) 34 is connected to the control device 30 via a connection node 301. The intermediate circuit capacitor 33 is connected between a positive pole of the positive voltage supply 34 and a housing potential 35 providing the reference potential. Although in . Fig. 6 is not visible, the control device 30 is on the circuit board 31 (see Fig. 1) and can be controlled from a central control unit (e.g. the vehicle's ECU).

[0030] The first signal pin 22 is connected on the circuit carrier side via a contact 292 to the circuit carrier 29 or the gate electrode 122 of the power switch 12 on the one hand, and on the circuit board side via a contact 312 to the circuit board 31 or the control device 30 mounted there on the other hand, in particular the first driver module 302. Analogously, the second signal pin 23 is connected on the circuit carrier side via a contact 293 to the circuit carrier 29 or the gate electrode 132 of the ACM auxiliary switch 130 on the one hand, and on the circuit board side via a contact 313 to the circuit board 31 or the control device 30 mounted there on the other hand, in particular the second driver module 304. The third signal pin 21 is electrically connected to the housing potential 35. Furthermore, the third signal pin 21 is connected on the circuit carrier side via a contact 291 to the negative-pole electrode orSource electrode 124, 134 of the power switch 12 and the ACM auxiliary switch 130, and on the circuit board side via a contact 311 to the circuit board 31, in particular to the control device 30. In this way, a first control path of the power switch 12 is formed (indicated by a dotted arrow line), which begins at the first driver module 302 and runs via the first signal pin 22 to the control electrode or gate electrode 122 of the power switch 12 and from there via the negative-pole current electrode or source electrode 124, the third signal pin 21 to the housing potential 35. Analogously, a second control path of the ACM auxiliary switch 130 is formed (indicated by a dotted arrow line), which starts from the second driver module 304 and runs via the second signal pin 23 to the control electrode or gate electrode 132 of the ACM auxiliary switch 130 and from there via the negative-pole current electrode orSource electrode 134, the third signal pin 21 to the housing potential 35. The first control path of the power switch 12 is electromagnetically decoupled from the actual load path (which runs from the positive-pole current electrode or drain electrode 126 via the semiconductor structure of the power switch 12 to the negative-pole current electrode or source electrode 124 and further to the housing potential 35) by means of the shielding jacket 24a-b and the sheet metal element 28, so that the transmission of the control signal (gate signal) for the power switch 12 is not impaired by interference and is therefore more robust. The same applies to the second control path of the auxiliary switch 130. Reference symbol 10 Power module 11 Protective cover (protective overmolding) 12,12a-b circuit breaker 122,132 Control electrode (gate electrode) 124,134 negative current electrode (source electrode) 126,136 positive current electrode (drain electrode) 130 auxiliary switches (ACM auxiliary switches) 14,16,18 power connections 13,15,17 Busbars 19 Insulating layer 22,22a-b (first) signal pin 24a-b umbrella cover 242 Opening 25 coolers 252 top 254 pin-fin structure 27 Sinter layer 28 shielding sheet metal element 29 Printed Circuit Boards (PCBs) 291-293 circuit carrier side contacts 30,30a-b Control device (gate driver) 301 connection nodes 302 first driver module 304 second driver module 31 Circuit board (driver board) 311-313 PCB-side contacts 33 DC link capacitor 34 positive voltage supply (VDD) 35 Housing potential

Claims

[1] Power module (10) for a converter for use in an at least partially electrified vehicle, wherein the power module (10) has one or more power switches (12, 12a-b) which are switchable for converting an input current into an output current and are mounted on a circuit carrier (29), wherein the power module (10) has a printed circuit board (31) which is equipped with components of a control device (30, 30a-b) for generating control signals, wherein the power module (10) has a plurality of signal pins (22, 22a-b) for transmitting the control signals to the control electrodes (122) of the power switches (12, 12a-b), wherein the power module (10) has a shielding jacket (24a-b) which encloses at least one of the signal pins (22, 22a-b) at least in sections, wherein a sheet metal element (28) is arranged between the power switches (12,12a-b) and the circuit board (31), which is potential-connected to the shielding jacket (24a-b). [2] Power module (10) according to claim 1, wherein the sheet metal element (28) is arranged on an underside of the circuit board (31) facing the power switches (12, 12a-b). [3] Power module (10) according to claim 2, wherein the underside of the circuit board (31) is completely covered by the sheet metal element (28) as viewed from the power switches (12, 12a-b). [4] Power module (10) according to one of the preceding claims, wherein the shielding jacket (24a-b) is formed in one piece with the sheet metal element (28). [5] Power module (10) according to one of the preceding claims, wherein a recess (282) is formed in the sheet metal element (28) for passing through the signal pins (22, 22a-b). [6] Power module (10) according to one of the preceding claims, wherein at least one further signal pin (23) for transmitting control signals to a control electrode (132) of an auxiliary switch (130) separate from the power switches (12, 12a-b) is enclosed by the shielding jacket (24a-b). [7] Power module (10) according to one of the preceding claims, wherein the shielding jacket (24a-b) is connected on the circuit carrier side to a negative-pole current electrode (124), in particular a source electrode, of the power switches (12, 12a-b) and on the circuit board side to a housing potential. [8] Converter for use in an at least partially electrified vehicle, comprising one or more power modules (10) according to one of the preceding claims. [9] Electric axle drive for an at least partially electrified vehicle, comprising an electric motor, a transmission device and a converter according to claim 8. [10] Vehicle, in particular at least partially electrified vehicle, comprising an electric axle drive according to claim 9.

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