Temperature measurement system for power semiconductors arranged on a base plate of an inverter

Abstract

A temperature measuring system is proposed for power semiconductors arranged on an upper side of a base plate of an inverter serving as a cooling plate, wherein coolant is guided along an underside of the base plate opposite the upper side at least in the region below the power semiconductors, wherein the coolant is supplied via at least one first coolant supply provided at an edge region of the base plate and discharged via at least one coolant outlet provided at an edge region of the base plate, wherein the temperature measuring system comprises: a carrier made of electrically non-conductive material that can be fastened to the base plate, at least one temperature sensor that is embedded in the carrier or fastened to the carrier, and contact elements that are fastened to the carrier or partially embedded in the carrier and are electrically contacted with the temperature sensor, which contact elements point above the carrier,wherein the carrier, after mounting on the base plate, is arranged on a region of the base plate such that each temperature sensor is arranged above a region in which coolant is guided and is mechanically fastened to the base plate such that it is in thermally conductive contact with the base plate.

Description

[0001] The present invention relates to the field of electromobility, in particular the cooling of power semiconductors installed in a power electronics module of an electric drive.

[0002] The use of electronic modules, such as power electronics modules, in motor vehicles has increased significantly in recent decades. This is due on the one hand to the need to improve fuel economy and vehicle performance, and on the other hand to advances in semiconductor technology. The main components of such an electronic module, also known as power electronics, are an electronic control unit (ECU), which is connected to or forms part of the vehicle's control unit(s) and receives control signals and / or information based, for example, on driving behavior or signals from other control units, and a DC / AC inverter, which is used to supply electrical machines such as electric motors or generators with multi-phase alternating current (AC).In this process, a direct current generated by a DC energy source, such as a battery or accumulator, is converted into a multi-phase alternating current. For this purpose, the inverters comprise a variety of electronic components that create bridge circuits (such as half-bridges), such as semiconductor power switches, also known as power semiconductors.

[0003] The power semiconductors are temperature-sensitive and are therefore cooled via a cooling system. The base plate, on the upper side of which the power semiconductors are arranged, serves as the cooling plate. A channel-like structure is provided on the underside of the cooling plate through which coolant is conducted. Since the base plate is made of a thermally conductive material, such as copper or aluminum, the temperature is transferred from the underside of the base plate to the upper side and thus to the power semiconductors, thus cooling them.

[0004] The challenges of temperature measurement in inverters include the isolation between the high-voltage and low-voltage potentials, depending on the location of the temperature sensor. Other considerations include signal contacting, i.e., the distance between the measurement and further processing of the measured values, as well as the response time of the temperature sensors and the available installation space, particularly the space on the circuit board used for signal processing. Thermal contacting, including vibrations and thermal expansion, must also be taken into account when planning the temperature measurement.

[0005] Several options are known for monitoring the temperature of power semiconductors. Temperature monitoring can be integrated directly into the power semiconductor module, e.g., as a temperature sensor or sensing diodes. Temperature measurement can also be performed directly on the power semiconductor modules, i.e., on their housing (the casing). Measurement can be performed either with contact with the housing or without contact.

[0006] Since there is still a need for improvement in the temperature measurement of power semiconductors of an inverter, the invention is based on the object of providing an improved temperature measuring system for measuring the temperature of power semiconductors of an inverter.

[0007] This object is achieved by the features of the independent claims. Advantageous embodiments are the subject of the dependent claims.

[0008] A temperature measuring system is proposed for power semiconductors arranged on an upper side of a base plate of an inverter serving as a cooling plate, wherein coolant is guided along an underside of the base plate opposite the upper side at least in the region below the power semiconductors, wherein the coolant is supplied via at least one first coolant supply provided at an edge region of the base plate and discharged via at least one coolant outlet provided at an edge region of the base plate, wherein the temperature measuring system comprises: a carrier made of electrically non-conductive material that can be fastened to the base plate, at least one temperature sensor that is embedded in the carrier or fastened to the carrier, and contact elements that are fastened to the carrier or partially embedded in the carrier and are electrically contacted with the temperature sensor, which contact elements point above the carrier,wherein the carrier, after mounting on the base plate, is arranged on a region of the base plate such that each temperature sensor is arranged above a region in which coolant is guided and is mechanically fastened to the base plate such that it is in thermally conductive contact with the base plate.

[0009] In one embodiment, a temperature sensor is arranged at a region of at least one coolant outlet and / or at a region of at least one coolant inlet.

[0010] In one embodiment, a lead frame embedded in the carrier is provided, to which the at least one temperature sensor is electrically contacted.

[0011] In one embodiment, a circuit board embedded in the carrier is provided, to which the at least one temperature sensor is electrically contacted and arranged such that it points towards the base plate.

[0012] In one embodiment, the at least one temperature sensor is formed as an SMD component or as a through-hole component.

[0013] In one embodiment, in the case where the at least one temperature sensor is formed as a through-hole component, the carrier has a pocket into which the at least one temperature sensor is at least partially immersed.

[0014] In one embodiment, the contact elements are formed as spring contacts, or through-pins, or press-fit pins protruding above the top of the base plate, as flex foil, as ribbon cable or as an assembly aid for accommodating flexible electrical cables.

[0015] In one embodiment, the areas of the base plate where the at least one temperature sensor is arranged are edge areas or areas between two phases of the inverter.

[0016] In one version, the support is attached to at least one screwing point on the base plate.

[0017] In one embodiment, at least one additional functional component is embedded in or arranged on the carrier, comprising at least one RAD resistor.

[0018] Furthermore, an inverter is provided, comprising a base plate serving as a cooling plate with power semiconductors arranged on an upper side thereof, and an area for conducting coolant provided along a lower side opposite the upper side and at least in the area below the power semiconductors, wherein the coolant is supplied via at least one first coolant supply provided at an edge area of ​​the base plate and discharged via at least one coolant outlet provided at an edge area of ​​the base plate, and a printed circuit board arranged above the power semiconductors, which is configured at least for conducting signals, and at least one described temperature measuring system, the carrier of which is fastened to the base plate in such a way that the at least one temperature sensor is in thermal contact with the base plate and in signal connection with the printed circuit board.

[0019] Furthermore, an electric drive of a vehicle is provided, in particular an electric axle drive, comprising at least one electric machine, a transmission device and an electronic module for controlling the electric drive, which electronic module has the inverter.

[0020] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures of the drawing, which illustrate details of the invention, and from the claims. The individual features can be implemented individually or in combination in a variant of the invention.

[0021] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. Fig. 1 shows a base plate with temperature measuring system according to an embodiment of the present invention. Fig. 2 shows a carrier according to an embodiment of the present invention. Fig. 3 shows components to be embedded in the Fig. 2 shown carrier. Fig. 4 shows a carrier according to another embodiment of the present invention. Fig. 5 shows components to be embedded in the Fig. 4 shown carrier. Fig. 6 to 8 each show a carrier according to further embodiments of the present invention. Fig. 9 shows the Fig. 8 shown carrier, which is arranged on a base plate and whose temperature sensor is contacted with a circuit board.

[0022] In the following descriptions of the figures, the same elements or functions are provided with the same reference symbols.

[0023] As is well known from the prior art, the cooling of the power semiconductors 2 of an inverter arranged on a base plate 1 in the automotive sector takes place by heat transfer into the base plate 1, which also serves as a cooling plate, and from there into the coolant guided along its underside. The underside of the base plate 1 can have additional structures (e.g. pin / pinfin) in order to achieve an even better transfer of heat into the coolant. The underside of the base plate 1 forms (if necessary together with a corresponding counterstructure) cooling channels, which are thus located below the power semiconductors 2 arranged on the top side. The coolant connection, i.e. coolant supply and coolant removal, takes place via supply lines from outside the base plate 1, i.e. via its edge regions.

[0024] As already mentioned at the beginning, the power semiconductors 2 are temperature-sensitive, so it is important to monitor their temperature and take measures (e.g., shutdown) if the measured temperature exceeds a threshold value. In this case, it may be sufficient not to measure the temperature directly at the power semiconductor 2, but merely to measure the coolant temperature at one or more points. To monitor this, the invention proposes a carrier 4 fastened to the base plate 1, on which a temperature sensor 40 is arranged, which is in thermal connection with the base plate 1 (after assembly). An NTC element (so-called thermistor), for example, can be used as the temperature sensor 40. Several designs are possible for implementation, which are described below with reference to the figures.

[0025] In all versions, a support 4 made of an electrically non-conductive material such as plastic, e.g. thermoplastic or duroplastic, is provided, which is attached to the base plate 1. The attachment is advantageously carried out at least at one existing screw point 10 of the base plate 1, as e.g. in Fig. 1. For this purpose, the fastening areas of the carrier 4 are formed, for example, as screw holes 43 (with or without metal bushing 430), which can be brought into alignment with the respective screwing point 10, so that a fastening element such as a screw can still be passed through both.

[0026] In addition, the carrier 4 has at least one temperature sensor 40. This is embedded in the carrier 4 or attached thereto in such a way that it is in thermal connection with the base plate 1. It is therefore preferably in contact with the base plate 1, whereby a so-called thermally conductive gap filler can also be provided as an intermediate layer, in particular to attach the temperature sensor 40 to the base plate 1 (thermally conductively), but also to stabilize it.

[0027] The temperature sensor 40 can be formed as an SMD component (i.e. without protruding contact legs), as in Fig. 1, Fig. 2 / 3 and 8 / 9, or as a through-hole component, as shown in Fig. 4 to 7 shown.

[0028] In addition, the areas of the temperature sensor 40 that are used to transmit the measured values ​​(i.e., for signal transmission) are electrically connected to contact elements 42, which, after final assembly, are contacted with corresponding contact areas of the printed circuit board 3 located above the power semiconductors 2. These contact elements 42 are in the Fig. 1 to 7 (top view of the carrier 4) are designed as lead frames 41 that are embedded in the carrier 4, i.e., surrounded by plastic. In each case, one end 420 of the contact elements 42 is connected to a region of the temperature sensor 40 that serves for signal transmission, and the other end 421 serves as a contact region for contacting the printed circuit board 3. This end can be formed as a spring contact, a through-pin, a press-fit pin, or a ribbon cable, as a flexible film, or as a soldering eye for attaching an electrical line 5 (cable). For better attachment of the lead frame 41 in the plastic, the lead frame 41 can have tabs 410.

[0029] In case the temperature sensor 40 is formed as an SMD component, as in Fig. 1 to 3, the ends 420 of the lead frames 41 lie directly against its contact areas for signal transmission, serving both for electrical contact and for its stabilization.

[0030] In the case that the temperature sensor 40 is formed as a through-hole component, i.e. has signal contacts 401 (contact legs) pointing outside the sensor, as in Fig. As shown in Figures 4 to 7, the ends 420 of the lead frame 41 are also connected to its contact areas (contact legs) for signal transmission. In this embodiment, the carrier 4 is also formed as a pocket 44 around the actual sensor to accommodate it. Fig. 4 / 6 and 7, the temperature sensor 40 is shown in different orientations. These orientations depend on the available installation space and also on the type of temperature sensor 40. In the Fig. 4 / 6, the temperature sensor 40 is arranged such that it could move above the pocket 44 when the carrier 4 is mounted on the base plate 1, thus reducing the thermal connection. It is therefore essentially parallel to the base plate 1. Therefore, in an embodiment as shown in Fig. 6, an undercut 440 is provided in the pocket 44 such that it serves as an upper limit (cover) for the temperature sensor 40, so that it cannot be pushed out upwards during assembly. Fig. 7, the temperature sensor 40 is arranged such that it is always in contact with the base plate 1 during assembly, even if the base plate is pushed upwards. It is therefore arranged vertically. In this embodiment, too, a pocket 44 is provided around the temperature sensor 40 to accommodate it. In all Fig. In the embodiments shown in Figures 1 to 7, the area of ​​the pocket 44 where the temperature sensor 40 is intended to contact the base plate 1 is, of course, not overmolded. A gap filler is advantageously introduced into the pocket 44 to secure the temperature sensor 40 to the base plate 1 and stabilize it, as well as to improve thermal contact.

[0031] In the Fig. 8 / 9, a circuit board 45 is embedded in the carrier 4, on which a temperature sensor 40 is arranged. The carrier 4 surrounds the circuit board 45 in such a way that it does not cover the temperature sensor 40, as in Fig. 8 (bottom view of the carrier 4). On the side of the circuit board 3 opposite the temperature sensor 40, contact elements 42 are provided to electrically connect the temperature sensor 40 to the circuit board 3 arranged above the power semiconductors 2. This can be done by means of the Fig. 1 to 7. Alternatively, a cable lug can be provided on the circuit board 3, into which an electrical line 5 (cable) can be inserted (e.g. soldered), as in Fig. 9 shown.

[0032] In all versions, a corresponding area is provided on the circuit board 3 above the power semiconductors 2, where the contact elements 42 can be contacted in order to transfer the measured values ​​of the temperature sensor 40 to the circuit board 3 for further processing.

[0033] In all embodiments, the temperature sensor 40 is advantageously attached to the base plate 1 by means of a gap filler.

[0034] The number and position of the temperature sensor(s) 40 can be determined depending on the application. Fig. 1 shows an embodiment in which a base plate 1 carries three phases U, V, W. Here, only one temperature measuring system (carrier 4 with components as described) is arranged at an edge region (here at phase U), wherein the carrier 4 can be connected to two opposing screw points 10 and has two temperature sensors 40. As already described, the temperature sensors 40 are always provided in an area above a coolant connection in order to measure the temperature of the coolant flowing there through the heat input into the base plate 1. This embodiment can be expanded by installing another temperature measuring system at the opposite edge region (in Fig. 1 right) and / or between the phases U, V, W.

[0035] Depending on the design, only one temperature sensor 40 may be provided per base plate 1 (regardless of the number of phases U, V, W present). In one design, this is arranged at a coolant outlet, i.e., at an edge region of the base plate 1. Monitoring the coolant outlet temperature is particularly advantageous, since this is where the heat input of all power semiconductors 2 occurs.

[0036] However, one temperature sensor 40 can also be provided at each coolant inlet and one at each coolant outlet. Furthermore, one or more temperature sensors 40 can be provided between two phases U, V, W if the base plate 1 carries several phases U, V, W, as shown in Fig. 1. This allows monitoring the temperatures of the power semiconductors 2 of each phase U, V, and W. In such a design, the carrier 4 must be adapted according to the available installation space, while the basic concept remains the same.

[0037] Furthermore, several temperature sensors 40 can be provided at the cooling connection, i.e., in the area of ​​the coolant inlet or the coolant outlet, or in a central area of ​​the base plate 1, which enables a direct connection of the temperature sensor 40 to the base plate 1 between the individual phases U, V, W or power semiconductors 2. This allows redundancy to be provided.

[0038] In a further embodiment, an additional functional component (not shown in the figures) is integrated into the carrier 4, i.e., embedded therein or attached to it. A so-called RAD (redundant active discharge) element is particularly advantageously provided. This serves to safely discharge the inverter's intermediate circuit capacitor. The RAD element is designed as a resistor which, in the event of a fault, converts the stored energy in the inverter's intermediate circuit capacitor into heat, thus establishing a safe state. By arranging it on the carrier 4, which in turn is arranged on the base plate 1 and thus close to the coolant, the RAD element can be more effectively cooled. Complex attachment to the cooling area is also eliminated. The RAD element and temperature sensor 40 do not influence each other, since the RAD element is only active in the event of a fault, when the temperature sensor 40 is not active (the measurement is not used).

[0039] As already mentioned at the beginning, the described temperature measuring system is used to measure the temperature of power semiconductors 2 of an inverter used in the automotive sector. The structure of such an inverter is known and is therefore only described here with the components most necessary for the temperature measuring system. Basically, a base plate 1 made of thermally conductive material such as copper or aluminum is provided, which serves both as a carrier plate and as a cooling plate for a predetermined number of power semiconductors 2. Power semiconductors 2 of one or more phases U, V, W are arranged and fastened on the upper side of the base plate, so that a single-phase or multi-phase module is formed. On the underside of the base plate 1, one or more cooling channels are provided, into which coolant is introduced via one or more coolant inlets and guided to one or more coolant outlets and from there away.Above the power semiconductors 2, among other things, busbars are arranged. A printed circuit board 3 is arranged above them (in . Fig.9), which serves at least for signal routing. This means that sensor signals (as well as the measured values ​​of the temperature sensor(s) 40 of the carrier 4) are routed there and transmitted via integrated conductor tracks to, for example, a microcontroller or a control unit for further processing. To transmit the signals, the circuit board 3 is contacted by corresponding contact elements 42 of the sensors. In the case of spring contacts, these are formed in such a way that they are tensioned by the application of the circuit board 3. In the case of pins, through-holes are provided on the circuit board 3 through which the pins can be inserted and, for example, soldered. For other contact elements 42, other suitable connections can be provided, e.g., solder pads, cable lugs, open conductor tracks for direct connection, etc.

[0040] By providing a carrier 4 with at least one integrated temperature sensor 40, a significantly simplified installation of the temperature sensor 40 is achieved, as is modularity. The number of temperature sensors 40 on the carrier 4 can vary, as can the number and positioning of the carriers 4, since although they must be adapted to the topology of the base plate 1, they can be manufactured as separate components. Due to the very high adaptability of the carrier 4, it can be arranged on differently designed base plates 1, in particular on single-phase and multi-phase modules, provided their screw points 10 are available for fastening.

[0041] An inverter with the described temperature measurement system is part of a power electronics module that serves to operate an electric drive (also referred to as an electric drive for short) of a vehicle powered at least partially by a rechargeable battery or a fuel cell. The vehicle is, in particular, a commercial vehicle such as a truck or a bus, or a passenger car. The power electronics module comprises a DC / AC inverter. It can also comprise or be a part of an AC / DC rectifier, a DC / DC converter, a transformer, and / or another electrical converter or a part of such a converter. In particular, the power electronics module serves to supply current to an electric machine, for example an electric motor and / or a generator.A DC / AC inverter is typically used to generate a multiphase alternating current from a direct current generated by a DC voltage from an energy source, such as a battery. A DC / DC converter, for example, is used to convert (step up) a direct current coming from a fuel cell into a direct current usable by the drive. List of reference symbols 1 base plate 10 screwing point 2 power semiconductors 3 circuit board 4 carriers 40 Temperature sensor 401 signal contacts 41 punched grids 410 flags 42 contact elements 420 end in contact with 40 421 end as contact area for 3 43 screw holes 430 sockets 44 bag 440 undercut 45 board 5 Line U, V, W phases

Claims

[1] Temperature measuring system for power semiconductors (2) arranged on an upper side of a base plate (1) of an inverter serving as a cooling plate, wherein coolant is guided along an underside of the base plate (1) opposite the upper side at least in the region below the power semiconductors (2), wherein the coolant is supplied via at least one first coolant supply provided at an edge region of the base plate (1) and is discharged via at least one coolant outlet provided at an edge region of the base plate (1), wherein the temperature measuring system comprises: - a support (4) made of electrically non-conductive material that can be attached to the base plate (1), - at least one temperature sensor (40) embedded in the carrier (4) or attached to the carrier (4), and - contact elements (42) attached to the carrier (4) or partially embedded in the carrier (4) and electrically contacted with the temperature sensor (40), which point above the carrier (4), wherein - the carrier (4), after being mounted on the base plate (1), is arranged on a region of the base plate (1) in such a way that each temperature sensor (40) is arranged above a region in which coolant is guided and is mechanically fastened to the base plate (1) in such a way that it is in thermally conductive contact with the base plate (1). [2] Temperature measuring system according to claim 1, wherein a temperature sensor (40) is arranged at a region of at least one coolant outlet and / or at a region of at least one coolant inlet. [3] Temperature measuring system according to claim 1 or 2, wherein - a lead frame embedded in the carrier (4) is provided, to which the at least one temperature sensor (40) is electrically contacted, or - wherein a circuit board (45) embedded in the carrier (4) is provided, to which the at least one temperature sensor (40) is electrically contacted and arranged such that it points towards the base plate (1). [4] Temperature measuring system according to one of the preceding claims, wherein the at least one temperature sensor (40) is formed as an SMD component or as a through-hole component. [5] Temperature measuring system according to claim 4, wherein in the case that the at least one temperature sensor (40) is formed as a through-hole component, the carrier (4) has a pocket (44) into which the at least one temperature sensor (40) is at least partially immersed. [6] Temperature measuring system according to one of the preceding claims, wherein the contact elements (42) are formed as spring contacts projecting above the upper side of the base plate (1), or through-pins, or press-fit pins, as a flexible foil, as a ribbon cable or as an assembly aid for receiving flexible electrical lines (5). [7] Temperature measuring system according to one of the preceding claims, wherein the regions of the base plate (1) on which the at least one temperature sensor (40) is arranged are edge regions or regions between two phases (U, V, W) of the inverter. [8] Temperature measuring system according to one of the preceding claims, wherein the carrier (4) is fastened to at least one screwing point (10) of the base plate (1). [9] Temperature measuring system according to one of the preceding claims, wherein at least one additional functional component is embedded in or arranged on the carrier (4), comprising at least one RAD resistor. [10] Inverter, comprising - a base plate (1) serving as a cooling plate with power semiconductors (2) arranged on an upper side thereof, and an area for conducting coolant provided along a lower side opposite the upper side and at least in the area below the power semiconductors (2), wherein the coolant is supplied via at least one first coolant supply provided at an edge area of ​​the base plate (1) and discharged via at least one coolant outlet provided at an edge area of ​​the base plate (1), and - a printed circuit board (3) arranged above the power semiconductors (2), which is designed at least to carry signals, and - at least one temperature measuring system according to one of the preceding claims, the carrier (4) of which is fastened to the base plate (1) in such a way that the at least one temperature sensor (40) is in thermal contact with the base plate (1) and in signal connection with the printed circuit board (3). [11] Electric drive of a vehicle, in particular electric axle drive, comprising at least one electric machine, a transmission device and an electronic module for controlling the electric drive, which has an inverter according to claim 10.

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