Temperature determination device for power module

Abstract

The invention relates to a temperature determination device for a power module. The temperature determination apparatus includes a water temperature estimation unit configured to determine a temperature increment of each of the switching elements based on operation information of the switching elements, determining an estimated water temperature of the cooling water based on the temperature increment and preset influence coefficients respectively corresponding to the remaining switching elements without the first temperature sensor; and a junction temperature determination unit configured to determine a junction temperature based on the estimated water temperature.

Description

Technical Field

[0001] The present invention relates to a temperature determination device for a power module, which is used to determine the junction temperature of the power module to protect the power module from over-temperature. Background Art

[0002] Generally, one end of each phase winding included in the motor is connected to one inverter, and the other end of each phase winding is connected to form a Y-type connection.

[0003] When driving the motor, the switching elements in the inverter are turned on / off by pulse width modulation control, and the line voltage is applied to the Y-connected windings of the motor to generate alternating current, thereby generating torque.

[0004] Since the fuel efficiency of environmentally friendly vehicles (such as electric vehicles that use the torque generated by such motors as power) is determined by the inverter-motor power conversion efficiency, in order to improve fuel efficiency, it is important to maximize the inverter power conversion efficiency and the efficiency of the motor.

[0005] The efficiency of the inverter-motor system is mainly determined by the voltage utilization of the inverter. When the operating point of the vehicle is determined by the relationship between the motor speed and torque in the range of high voltage utilization, the fuel efficiency of the vehicle can be improved.

[0006] However, in order to increase the maximum torque of the motor, as the number of windings of the motor increases, the range with higher voltage utilization will be away from the low torque area which is the main operating point of the vehicle, so the fuel efficiency will be reduced. In addition, from the perspective of fuel efficiency, when the main operating point is designed to be included in the range with higher voltage utilization, the maximum torque of the motor is limited, which may cause the problem of reduced acceleration and starting performance of the vehicle.

[0007] In the field of the present invention, due to the need for a motor driving technology capable of improving system efficiency while covering both low power ranges and high power ranges with one motor, a technology of driving one motor in two different modes using two inverters and a mode switch has recently been introduced.

[0008] In order to realize such motor driving technology, a power module including a plurality of switching elements may be used. In the case where such a power module operates at a high temperature, the power module may be damaged or its durability may be reduced, so it is necessary to manage the power module so that the power module operates within a specific temperature range.

[0009] The information contained in this background technology of the present invention is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that this information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0010] Various aspects of the present invention are directed to providing a temperature determination device for a power module, which can reduce the dependence on a water temperature sensor for measuring the temperature of cooling water for cooling the power module when determining the junction temperature of the power module, and can determine the junction temperature even when the junction temperature of a part of the switching element cannot be directly detected.

[0011] The objects of the present invention are not limited to the above objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

[0012] According to one aspect of the present invention, the above and other purposes can be achieved by providing a temperature determination device for a power module, the power module comprising a plurality of switching elements and a first temperature sensor, the first temperature sensor being arranged at a part of the plurality of switching elements and configured to measure the temperature of the switching elements, the temperature determination device being used to predict the temperature of the power module cooled by cooling water, the temperature determination device comprising: a water temperature estimation unit, configured to determine a temperature increment of each of the plurality of switching elements based on working information of the plurality of switching elements, and to determine an estimated water temperature of the cooling water based on the temperature increment and preset influence coefficients respectively corresponding to the remaining switching elements for which the first temperature sensor is not arranged; and a junction temperature determination unit, configured to determine a junction temperature of at least one of the plurality of switching elements based on the estimated water temperature.

[0013] For example, the temperature increase may be determined based on power loss and thermal resistance caused by the operation of the power module.

[0014] For example, the influence coefficient may be preset based on an experimental value regarding the correlation between the heat generation of the switching element, which is not provided with the first temperature sensor, among the plurality of switching elements and the measurement result of the first temperature sensor.

[0015] For example, the junction temperature determination unit may be configured to determine the junction temperature of at least one of the plurality of switching elements by further considering a measurement result of a second temperature sensor for measuring the temperature of cooling water.

[0016] For example, the multiple switching elements may include first switching elements and second switching elements of different types, and a third switching element that determines whether the second switching element will work according to the on / off state, the power module may include a first operating mode in which the first switching element works when the third switching element is turned on, or a second operating mode in which the second switching element works together with the first switching element when the third switching element is turned off, and the water temperature estimation unit may be configured to determine the estimated water temperature according to one of the first operating mode and the second operating mode.

[0017] For example, the first switching element may be implemented using silicon carbide (SiC).

[0018] For example, the first temperature sensor may be provided at the second switching element.

[0019] For example, when the operating mode of the power module is the first operating mode, the water temperature estimation unit can be configured to determine the estimated water temperature based on the first temperature increment and the first influence coefficient regarding the first switching element and the third temperature increment and the third influence coefficient regarding the third switching element.

[0020] For example, the water temperature estimation unit may be configured to determine the estimated water temperature by subtracting a value obtained by reflecting the first influence coefficient in the first temperature increment and a value obtained by reflecting the third influence coefficient in the third temperature increment from a measurement result of the first temperature sensor.

[0021] For example, the junction temperature determination unit may be configured to: determine the junction temperature of the first switching element based on the determined estimated water temperature and the first temperature increment; determine the junction temperature of the third switching element based on the determined estimated water temperature and the third temperature increment.

[0022] For example, when the operating mode of the power module is the second operating mode, the water temperature estimation unit may be configured to determine the estimated water temperature based on a first temperature increment and a first influence coefficient of the first switching element and a second temperature increment of the second switching element.

[0023] For example, the water temperature estimation unit may be configured to determine the estimated water temperature by subtracting a value obtained by reflecting the first influence coefficient in the first temperature increment and the second temperature increment from a measurement result of the first temperature sensor.

[0024] For example, the junction temperature determination unit may be configured to determine the junction temperature of the first switching element based on the determined estimated water temperature and the first temperature increment.

[0025] For example, the junction temperature determination unit may be configured to determine a temperature according to a measurement result of the first temperature sensor as the junction temperature of the second switching element.

[0026] For example, the junction temperature determination unit may be configured to determine the junction temperature of the second switching element based on the determined estimated water temperature and the second temperature increment.

[0027] The methods and apparatus of the present invention have other features and advantages that will be apparent from, or will be described in detail in, the accompanying drawings and subsequent detailed descriptions incorporated herein, which together serve to explain the specific principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a circuit diagram of a motor drive device applicable to various exemplary embodiments of the present invention;

[0029] Figure 2 is a schematic diagram showing switching of a driving mode of a motor driving device applicable to various exemplary embodiments of the present invention;

[0030] Figure 3 is a schematic diagram showing a power module suitable for use with various exemplary embodiments of the present invention;

[0031] Figure 4 is a circuit diagram of a power module suitable for use with various exemplary embodiments of the present invention;

[0032] Figure 5 is a schematic diagram of a temperature determination apparatus for a power module according to an exemplary embodiment of the present invention;

[0033] Figure 6 is a schematic diagram illustrating a working mechanism of determining a junction temperature according to an exemplary embodiment of the present invention; and

[0034] Fig. 7A and 7B is a diagram for describing a junction temperature determination result according to an exemplary embodiment of the present invention by comparing with a comparative example.

[0035] It should be understood that the attached drawings are not drawn to scale, but are only appropriately simplified drawings for illustrating various features of the basic principles of the present invention. The predetermined design features of the present invention disclosed herein (including, for example, specific dimensions, directions, positions and shapes) will be determined in part by the specific environment to be applied and used.

[0036] In the figures, like reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. DETAILED DESCRIPTION

[0037] Reference will now be made in detail to various embodiments of the present invention, examples of which are shown in the accompanying drawings and in the following description. Although the present invention will be described in conjunction with exemplary embodiments of the present invention, it will be understood that this specification is not intended to limit the present invention to those exemplary embodiments of the present invention. On the other hand, the present invention is intended to cover not only exemplary embodiments of the present invention, but also various variant embodiments, modified embodiments, equivalent embodiments and other embodiments that may be included within the spirit and scope of the present invention as defined by the appended claims.

[0038] In order to explain the exemplary embodiments according to the present invention, only the specific structure or functional description of the embodiments of the present invention included in the present specification or application is shown, and the exemplary embodiments of the present invention may be implemented in various forms and should not be construed as being limited to the exemplary embodiments described in the present specification or application.

[0039] The exemplary embodiments of the present invention can be modified in various ways and can have various forms, so specific embodiments are shown in the drawings and described in detail in this specification or application. However, it is not intended to limit the exemplary embodiments of the concept according to the present invention to specific inclusion forms, and it should be understood to include all modified embodiments, equivalent embodiments or variant embodiments included in the spirit and scope of the present invention.

[0040] Unless otherwise defined, all terms (including technical or scientific terms) have the same meaning as those generally understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms (such as terms defined in dictionaries) should be understood to be consistent with the meanings in the relevant technologies according to the context. Such terms should not be interpreted as ideal or overly formalized meanings, unless different definitions are carried out in the exemplary embodiments of the present invention.

[0041] Hereinafter, various exemplary embodiments included in the present specification will be described in detail with reference to the accompanying drawings, but the same or similar components are denoted by the same reference numerals and redundant descriptions thereof will be omitted.

[0042] The suffixes “module” and “part” of the elements herein are used for convenience of description and thus may be used interchangeably without having any distinguishable meanings or functions.

[0043] In the following description of the exemplary embodiments included in this specification, when the detailed description of the known functions and configurations incorporated herein may obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, the accompanying drawings are provided only to facilitate the understanding of the exemplary embodiments included in this specification, rather than to limit the technical spirit included herein, and include all modified embodiments, equivalent embodiments and variant embodiments included in the spirit and scope of the present invention.

[0044] The terms "first" and / or "second" are used to describe various components, but these components should not be limited by these terms. The terms are used to distinguish one component from another component.

[0045] When a component is "coupled" or "connected" to another component, it should be understood that there may be a third component between the two components, although the component can be directly coupled or connected to another component. When a component is "directly coupled" or "directly connected" to another component, it should be understood that there is no element between the two components.

[0046] Unless the context clearly indicates otherwise, elements described in the singular are intended to include plural elements.

[0047] In this specification, it will be further understood that the terms “include” or “comprises” indicate the presence of the described features, values, steps, operations, components, parts or a combination thereof, but do not exclude the presence or addition of one or more other features, values, steps, operations, components or a combination thereof.

[0048] Furthermore, the units or control units included in the names of motor control unit (MCU), hybrid control unit (HCU), etc. are simply terms widely used to name controllers configured to control specific vehicle functions and do not mean general functional units.

[0049] The controller may include a communication device to communicate with other controllers or sensors to control the functions of the controller, a memory to store operating system or logic commands and input / output information, and one or more processors to perform the determinations, operations and decisions required to control the functions.

[0050] Before describing the temperature determination apparatus for a power module according to an exemplary embodiment of the present invention, reference will first be made to Figure 1 , Figure 2 , Figure 3 and Figure 4 A motor drive device and a power module applicable to an exemplary embodiment of the present invention will be described.

[0051] Figure 1 is a circuit diagram of a motor driving device applicable to various exemplary embodiments of the present invention.

[0052] refer to Figure 1 The motor drive device according to various exemplary embodiments of the present invention may include a first inverter 10, a second inverter 20, a motor 30 including a plurality of windings C1, C2 and C3 corresponding to a plurality of phases, respectively, a mode switching unit 40, a battery 50, a DC capacitor (or a DC-link capacitor) 60, and a controller 70.

[0053] The first inverter 10 may include a plurality of first switching elements S11, S12, S13, S14, S15, and S16 connected to one end of each of the windings C1, C2, and C3, and the second inverter 20 may include a plurality of second switching elements S21, S22, S23, S24, S25, and S26 connected to the other end of each of the windings C1, C2, and C3. The mode switching unit 40 may include a plurality of mode switches S31, S32, and S33 connected between the other end of each of the windings C1, C2, and C3 and the neutral ends of the plurality of windings C1, C2, and C3. The controller 70 can be configured to control the on / off state of the first switching elements S11, S12, S13, S14, S15 and S16, the second switching elements S21, S22, S23, S24, S25 and S26, and the mode switches S31, S32 and S33 based on the required power of the motor (i.e., the torque command of the motor), the DC terminal voltage of the inverters 10 and 20 (i.e., the voltage of the battery), the phase current of the motor and the motor angle.

[0054] The first inverter 10 may include a plurality of branches 11, 12, and 13 to which a DC voltage formed in a DC capacitor 60 connected between both ends of the battery 50 is applied. The branches 11, 12, and 13 correspond to a plurality of phases of the motor 30 and thus may be electrically connected.

[0055] The first branch 11 may include two switch elements S11 and S12 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switch elements S11 and S12 may be connected to one end of the winding C1 of one phase in the motor 30, thereby inputting and outputting the AC power corresponding to one phase. Similarly, the second branch 12 may include two switch elements S13 and S14 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switch elements S13 and S14 may be connected to one end of the winding C2 of one phase in the motor 30, thereby inputting and outputting the AC power corresponding to one phase. In addition, the third branch 13 may include two switch elements S15 and S16 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switch elements S15 and S16 may be connected to one end of the winding C3 of one phase in the motor 30, thereby inputting and outputting the AC power corresponding to one phase.

[0056] The second inverter 20 may include a plurality of branches 21, 22, and 23 to which a DC voltage formed in a DC capacitor 60 connected between both ends of the battery 50 is applied. The branches 21, 22, and 23 may correspond to a plurality of phases of the motor 30 and thus may be electrically connected.

[0057] The first branch 21 includes two switching elements S21 and S22 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S21 and S22 can be connected to the other end of the winding C1 of one phase in the motor 30, so as to input and output the AC corresponding to one phase. Similarly, the second branch 22 includes two switching elements S23 and S24 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S23 and S24 can be connected to the other end of the winding C2 of one phase in the motor 30, so as to input and output the AC corresponding to one phase. In addition, the third branch 23 includes two switching elements S25 and S26 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S15 and S26 can be connected to the other end of the winding C3 of one phase in the motor 30, so as to input and output the AC corresponding to one phase.

[0058] One end of each of the mode switches S31, S32, and S33 may be connected to the other end of each of the windings C1, C2, and C3 included in the motor 30, and the other ends of the mode switches S33, S31, and S32 may be connected to each other at the neutral end of the motor 30. The plurality of mode switches S31, S32, and S33 may adopt various switching devices known in the art, for example, MOSFET, IGBT, thyristor, relay, etc.

[0059] although Figure 1 Not shown in the figure, the motor driving device may further include a so-called Y-type capacitor (Y-Cap) in which two capacitors are connected in series between the positive (+) DC terminal and the negative (-) DC terminal and a connection node between the two capacitors is grounded.

[0060] The controller 70 can be configured to control the motor 30 based on the required power of the motor 30 and to switch the switching elements S11, S12, S13, S14, S15, S16, S21, S22, S23, S24, S25 and S26 included in the first inverter 10 and the second inverter 20 through pulse width modulation control, thereby controlling the motor 30 so that the motor 30 runs.

[0061] In addition, the controller 70 may be configured to control the on / off state of the third switching elements S31, S32 and S33 included in the mode switching unit 40 according to the motor driving mode. The motor driving mode may include a first driving mode and a second driving mode. In this case, the first driving mode may be referred to as a "closed end winding (CEW) mode" and the second driving mode may be referred to as an "open end winding (OEW) mode".

[0062] In the CEW mode, the controller 70 may be configured to control the mode switches S31, S32, and S33 so that they are in an on state and drive the motor 30 through the first inverter 10. The mode switches S31, S32, and S33 may electrically connect the other end of each of the windings C1 to C3 to the neutral end of the plurality of windings C1 to C3 in the on state.

[0063] In the OEW mode, the controller 70 may be configured to control the mode switches S31, S32, and S33 so that they are in an off state, and drive the motor 30 through the two inverters 10 and 20. The mode switches S31, S32, and S33 may electrically separate the other end of each of the windings C1 to C3 from the neutral end of the plurality of windings C1 to C3 in an off state.

[0064] Figure 2 2 is a schematic diagram illustrating switching between driving modes of a motor driving device applicable to various exemplary embodiments of the present invention.

[0065] Figure 2 A motor operation point map is shown, wherein an output limit curve L1 of a CEW mode, an output limit curve L2 of an OEW mode, and a mode switching reference line L3 based on an efficiency map are displayed.

[0066] The output limit curves L1 and L2 may represent output torque limit values ​​of the motor for each rotation speed (e.g., RPM) of the motor in each motor driving mode. The output limit curve L2 has an output limit greater than that of the output limit curve L1 at least in a portion of the revolutions per minute (rpm) region, and the output limit curves L1 and L2 may be set in consideration of durability, heat generation, and current controllability of the motor and the inverter.

[0067] The mode switching reference line L3 based on the efficiency map may correspond to the boundary line between the high efficiency region of the CEW mode and the high efficiency region of the OEW mode. The efficiency map includes information on the more efficient mode between the CEW mode and the OEW mode in each combination of the torque and the reverse magnetic flux of the motor, and may have a tabular form depending on the implementation. For example, the efficiency map may be obtained based on the results of experimentally measuring the motor losses according to the speed and torque of the motor for each DC terminal voltage of the inverter in each motor drive mode. Here, the reverse magnetic flux of the motor may be inversely proportional to the DC terminal voltage of the inverter (i.e., the voltage of the battery) and may be directly proportional to the speed of the motor.

[0068] According to an exemplary embodiment of the present invention, the mode switching reference line L3 may have a shape such as L3' according to the specifications of the motor driving device. However, Figure 2 The mode switching reference lines L3 and L3' shown in FIG. 1 are exemplary and are not necessarily limited thereto.

[0069] In order to switch the motor drive mode according to the mode switching reference line L3, the controller 70 can refer to the efficiency map and bidirectionally switch the CEW mode and the OEW mode according to the torque command value and the reverse flux value of the motor. In this case, the reverse flux value can be determined based on the torque command of the motor, the DC terminal voltage of the inverter, and the required speed of the motor. According to an exemplary embodiment of the present invention, the controller 70 can correct the mode switching reference line in consideration of the output limit or hysteresis of the motor drive mode. In this case, the motor drive mode can be switched based on the corrected mode switching reference line according to the torque command value and the reverse flux value of the motor.

[0070] refer to Figure 1 and Figure 2 The motor drive device applicable to the exemplary embodiment of the present invention described above can be configured by a combination of power modules including a plurality of switching elements. For example, when one branch of each of the inverters 10 and 20 and one switching element constituting the mode switching unit 40 are arranged in one power module, the motor drive device can be configured using three power modules configured in this manner. This will be referred to as Figure 3 and Figure 4 Give a description.

[0071] Figure 3 is a schematic diagram showing a power module suitable for use in an exemplary embodiment of the present invention, Figure 4 yes Figure 3 The circuit diagram of the power module is shown in .

[0072] refer to Figure 3 and Figure 4A power module 100 applicable to an exemplary embodiment of the present invention may include an insulating circuit board 110, a pair of first switching elements S11 and S12, a pair of second switching elements S21 and S22, and a third switching element S31, and further includes a current sensor 120, a charging diode 130, and the like.

[0073] First, the first switching elements S11 and S12 can constitute a reference Figure 1 and Figure 2 The second switching elements S21 and S22 may constitute a branch of the first inverter 10 in the motor drive device described in the reference Figure 1 and Figure 2 The third switching element S31 may constitute a branch of the second inverter 20 in the motor drive device described in the embodiment of the present invention. Figure 1 and Figure 2 A mode switching unit in a motor drive device is described.

[0074] Multiple switching elements S11, S12, S21, S22 and S31 can be arranged on the insulating circuit board 110, and the power module 100 suitable for the exemplary embodiment of the present invention can be implemented as follows: the switching elements S11, S12, S21, S22 and S31 are arranged on one insulating circuit board 110, or the switching elements S11, S12, S21, S22 and S31 are arranged between multiple insulating circuit boards 110.

[0075] Although not shown, a cooling channel may be provided outside the power module 100 , and the power module 100 may be cooled by cooling water flowing in the cooling channel.

[0076] Meanwhile, these switch elements S11, S12, S21, S22 and S31 can be implemented by at least one semiconductor chip. For example, each switch element in a pair of first switch elements S11 and S12 can be implemented by two semiconductor chips. On the other hand, each switch element in a pair of second switch elements S21 and S22 and third switch element S31 can be implemented by one semiconductor chip.

[0077] In the case where each switching element (e.g., switching elements S11 and S12) is implemented using a plurality of semiconductor chips, the size and output performance of each semiconductor chip can be reduced when the same required power is assumed. Therefore, in the case where there are limitations (e.g., high cost) in implementing a switching element using a single semiconductor chip with high output performance, a method of implementing a switching element by combining a plurality of semiconductor chips can be used.

[0078] The semiconductor chip for realizing the switching elements S11, S12, S21, S22 and S31 can be realized using an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), etc., and silicon (Si) or silicon carbide (SiC) can be used as its material.

[0079] The first switching elements S11 and S12 , the second switching elements S21 and S22 , and the third switching element S31 may be implemented as different types of switching elements, and only a portion of the switching elements may be provided with the first temperature sensor 140 for measuring the junction temperature.

[0080] When the first temperature sensor 140 is set in all switching elements S11, S12, S21, S22 and S31, the temperature of each of the switching elements S11, S12, S21, S22 and S31 can be measured more simply and accurately, thereby easily realizing over-temperature protection of the power module 100.

[0081] However, when the first temperature sensor 140 is set in all the switching elements S11, S12, S21, S22 and S31, additional space is required for arranging additional first temperature sensors 140, signal pins for connecting the first temperature sensors 140, etc., which is not conducive to the miniaturization of the module and increases the cost.

[0082] Therefore, instead of setting the first temperature sensor 140 in all the switching elements S11, S12, S21, S22 and S31 in the power module 100, the first temperature sensor 140 may be set only in a part of the switching elements S21 and S22, and the switching elements S11, S12, S21, S22 and S31 in which the first temperature sensor 140 will be set may be determined based on the characteristics of the switching elements S11, S12, S21, S22 and S31.

[0083] Some of the first switching elements S11 and S12, the second switching elements S21 and S22, and the third switching element S31 can be implemented as the same type, and some can be implemented as different types, and whether the first temperature sensor 140 is set may depend on the type of each of the switching elements S11, S12, S21, S22, and S31.

[0084] Since the first switching elements S11 and S12 can always work when driving the motor, high-performance output specifications are required compared to the second switching elements S21 and S22. For this reason, the first switching elements S11 and S12 can be implemented using SiC. In the case where the first switching elements S11 and S12 are implemented using SiC, the cost is very high compared to the case where the first switching elements S11 and S12 are implemented using IGBTs, etc., and it is difficult to provide a space for installing the first temperature sensor 140.

[0085] On the other hand, since the second switching elements S21 and S22 can work together with the first switching elements S11 and S12 when the motor is operated in the high power mode, the required power specification can be lower than the power specification of the first switching elements S11 and S12. Therefore, unlike the first switching elements S11 and S12, the second switching elements S21 and S22 have less burden when the first temperature sensor 140 is installed, and can be implemented using, for example, IGBTs.

[0086] However, unlike the above description, the power module 100 applicable to the exemplary embodiment of the present invention may include a single type of switching element, and even if the same type of switching element is provided, whether the first temperature sensor 140 is provided may differ for the switching element.

[0087] The temperature determination device 200 for a power module according to an exemplary embodiment of the present invention is configured to determine the temperatures of the plurality of switching elements S11, S12, S21, S22 and S31 by means of the first temperature sensor 140 provided in a portion of the plurality of switching elements S11, S12, S21, S22 and S31 as described above, thereby being able to improve the accuracy of the junction temperature determination while improving the efficiency of the junction temperature determination.

[0088] In the following, reference will be made to Figure 5 and Figure 6 The temperature determining apparatus 200 for a power module according to an exemplary embodiment of the present invention is described in detail.

[0089] Figure 5 is a schematic diagram of a temperature determining apparatus for a power module according to an exemplary embodiment of the present invention.

[0090] refer to Figure 5 , a temperature determination device 200 for a power module according to an exemplary embodiment of the present invention is configured to predict the temperature of a power module 100, includes a water temperature estimation unit 210 and a junction temperature determination unit 220, receives operating information of switching elements S11, S12, S21, S22 and S31, a measurement result of a first temperature sensor 140, etc., and outputs a junction temperature determination result.

[0091] Here, the power module 100 includes a plurality of switching elements S11, S12, S21, S22, and S31 and a first temperature sensor 140 provided in a portion of the plurality of switching elements to measure junction temperatures of the switching elements, and the power module 100 may be cooled by cooling water.

[0092] The operation information of the switching elements S11, S12, S21, S22, and S31 input to the temperature determination device 200 may be used to determine the temperature change due to the heating of the switching elements S11, S12, S21, S22, and S31, and may include, for example, whether the switching elements S11, S12, S21, S22, and S31 are operating, load current, input voltage, variable frequency, etc. The operation information of the switching elements S11, S12, S21, S22, and S31 may be information about each of the switching elements S11, S12, S21, S22, and S31 included in the power module 100.

[0093] In addition, the temperature determination device 200 may use the measurement result of the first temperature sensor 140 as its input information, and the measurement result of the first temperature sensor 140 may be used to estimate the water temperature and determine the junction temperature.

[0094] Based on the above input information, the temperature determination device 200 according to the exemplary embodiment of the present invention can be configured to determine the junction temperature of the power module 100 and output the determination result as the output information. The output determination result can be used for over-temperature protection control of the power module 100.

[0095] The above input information can be obtained from a controller configured to control the power module 100 or its upper controller, and the above output information can be sent to the controller. To this end, the temperature determination device 200 according to the exemplary embodiment of the present invention can be connected to the controller configured to control the power module 100, or can be implemented as a function of the controller.

[0096] Meanwhile, the water temperature estimating unit 210 may be configured to determine a temperature increase of each of the switching elements S11 , S12 , S21 , S22 , and S31 based on operation information of the switching elements S11 , S12 , S21 , S22 , and S31 .

[0097] In this case, the temperature increase may be determined based on the power loss and thermal resistance caused by the operation of the power module.

[0098] The power loss caused by the operation of the power module 100 may occur during the operation of the switching elements S11, S12, S21, S22 and S31 and the charging diode, and may include conduction loss caused when the current flowing through the switching elements and the charging diode 130 passes through the resistor and switching loss caused by the switching operation.

[0099] The conduction loss and the switching loss of the switching elements S11 , S12 , S21 , S22 , and S31 and the charging diode 130 may be determined based on the input load current, the input voltage, the variable frequency, and the like.

[0100] The thermal resistance caused by the operation of the power module 100 may be determined according to the unique characteristics of the power module 100 and the heat dissipation characteristics of a cooler connected to the power module 100 , and based on input load current, input voltage, variable frequency, etc.

[0101] In addition, the water temperature estimation unit 210 can be configured to determine the estimated water temperature of the cooling water based on the determined temperature increment and a preset influence coefficient corresponding to the switching element without the first temperature sensor among the plurality of switching elements S11, S12, S21, S22 and S31.

[0102] In this case, the influence coefficient may be set based on an experimental value regarding correlation between heat generation of a switching element not provided with the first temperature sensor among the plurality of switching elements S11 , S12 , S21 , S22 , and S31 and a measurement result of the first temperature sensor 140 .

[0103] The measurement result of the first temperature sensor 140 is affected not only by the switch element provided with the first temperature sensor 140 but also by the heating of the switch element not provided with the first temperature sensor 140. In addition, the heating of the charging diode 130 also affects the measurement result of the first temperature sensor 140.

[0104] For example, when the plurality of switching elements S11, S12, S21, S22, and S31 include first switching elements S11 and S12, second switching elements S21 and S22, and third switching element S31, and the first temperature sensor 140 is provided only at the second switching elements S21 and S22, the vicinity of the first temperature sensor 140 may be directly heated due to the heat generated by the second switching elements S21 and S22, and may also be indirectly heated due to the heat generated by the first switching elements S11 and S12 and the third switching element S31. In addition, the vicinity of the first temperature sensor 140 may be heated due to the heat generated by the charging diode 130. In this case, the degree of contribution of each of the switching elements S11, S12, S21, S22, and S31 or the charging diode 130 to the temperature near the first temperature sensor 140 measured by the first temperature sensor 140 may be determined, and the influence coefficient may be set according to the degree of contribution.

[0105] By reflecting the mutual influence caused by the heat generation of the switching elements S11, S12, S21, S22 and S31 when estimating the water temperature and determining the junction temperature in this way, even the junction temperature of the switching element in which the first temperature sensor 140 is not set can be determined by setting the first temperature sensor 140 only in a part of the switching elements.

[0106] Meanwhile, the junction temperature determining unit 220 may be configured to determine the junction temperature of at least a portion of the plurality of switching elements S11 , S12 , S21 , S22 , and S31 based on the estimated water temperature of the cooling water determined by the water temperature estimating unit 210 .

[0107] The junction temperature determination unit 220 may be configured to determine the final junction temperature based on the temperature increment and the estimated water temperature determined by the water temperature estimation unit 210. Since the estimated water temperature may represent the temperature near the switching elements S11, S12, S21, S22, and S31, a value obtained by adding the temperature increment to the estimated water temperature may be determined as the junction temperature of the switching elements S11, S12, S21, S22, and S31.

[0108] In the case of a switching element provided with the first temperature sensor 140, the measurement result of the first temperature sensor 140 itself can represent the junction temperature of the switching element, so the measurement result of the first temperature sensor 140 itself can be determined as the junction temperature of the switching element instead of using the estimated water temperature as described above.

[0109] In addition, although not required, the junction temperature determination unit 220 may be configured to determine the junction temperature by further considering the measurement result of the second temperature sensor for measuring the temperature of the cooling water. In this case, if the water temperature measured by the second temperature sensor can be used to determine the junction temperature, the junction temperature may be determined by adding the temperature increment to the measurement result of the second temperature sensor, otherwise, the junction temperature may be determined using the estimated water temperature.

[0110] The plurality of switching elements S11, S12, S21, S22 and S31 provided in the power module 100 may be divided into different types of first switching elements S11 and S12, second switching elements S21 and S22, and a third switching element S31 configured to determine whether the second switching elements S21 and S22 will operate according to an on / off state.

[0111] In this case, the power module 100 can operate in different operating modes according to the on / off state of the third switch element S31. The operating modes of the power module 100 may include a first operating mode and a second operating mode. In the first operating mode, when the third switch element S31 is turned on, the first switch elements S11 and S12 operate. In the second operating mode, when the third switch element S31 is turned off, the second switch elements S21 and S22 work together with the first switch elements S11 and S12.

[0112] Here, the first operation mode is used to drive the motor driving device in a first driving mode (ie, CEW mode), and the second operation mode is used to drive the motor driving device in a second driving mode (eg, OEW mode).

[0113] In this case, the water temperature estimation unit 210 may be configured to determine the estimated water temperature according to the first operation mode and the second operation mode of the power module 100. Since the operation of each of the switching elements S11, S12, S21, S22, and S31 differs according to the operation mode of the power module 100, the accuracy and usability of the temperature determination may be improved by reflecting the operation mode in the estimated water temperature and the junction temperature determination.

[0114] In addition, the first switching elements S11 and S12 and the second switching elements S21 and S22 can be configured as different types of switching elements according to the driving mode of the motor drive device and the working mode of the power module 100 as described above. For example, as described above, the first switching elements S11 and S12 can be implemented using SiC, and the second switching elements S21 and S22 can be implemented using IGBT. In addition, the third switching element S31 can be implemented using SiC like the first switching elements S11 and S12.

[0115] In this case, the first temperature sensor 140 may be provided only to the second switching elements S21 and S22 which are relatively inexpensive and advantageous in terms of preparing a space for the sensor.

[0116] According to an exemplary embodiment of the present invention, the temperature determining device 200 may be a processor (eg, computer, microprocessor, CPU, ASIC, circuit, logic circuit, etc.) for executing a program, a software instruction reproduction algorithm, etc.

[0117] Alternatively, each of the water temperature estimation unit 210 and the junction temperature determination unit 220 may be a processor (eg, computer, microprocessor, CPU, ASIC, circuit, logic circuit, etc.) for executing a program, a software instruction reproduction algorithm, etc.

[0118] In the following, reference will be made to Figure 6 The temperature determination process of the power module 100 configured as above is described in detail.

[0119] Figure 6 is a schematic diagram illustrating a working mechanism of determining a junction temperature according to an exemplary embodiment of the present invention.

[0120] Figure 6 The process of determining the junction temperature T_1 of the first switching elements S11 and S12 , the junction temperature T_2 of the second switching elements S21 and S22 , and the junction temperature T_3 of the third switching element S31 is shown.

[0121] The measurement result T_sense of the first temperature sensor 140 may be expressed differently according to the working mode of the power module 100, such as Figure 6 As shown, in the case of the first working mode, the measurement result can be expressed as T_sense1, and in the case of the second working mode, the measurement result can be expressed as T_sense2.

[0122] Hereinafter, a temperature determination process in a case where the operation mode of the power module 100 applicable to the exemplary embodiment of the present invention is the first operation mode will be described first.

[0123] The water temperature estimation unit 210 may be configured to determine the estimated water temperature based on the first temperature increment ΔT_1 and the first influence coefficient X regarding the first switching elements S11 and S12 and the third temperature increment ΔT_3 and the third influence coefficient Y regarding the third switching element S31 .

[0124] For example, the water temperature estimation unit 210 may be configured to subtract a value obtained by reflecting the first influence coefficient X in the first temperature increment ΔT_1 and a value obtained by reflecting the third influence coefficient Y in the third temperature increment ΔT_3 from the measurement result T_sense1 of the first temperature sensor 140 provided at the second switching elements S21 and S22, thereby determining the estimated water temperature T_w.

[0125] That is, the estimated water temperature T_w can be determined by the following formula.

[0126] T_w=T_sense1-(X*ΔT_1+Y*ΔT_3)

[0127] In addition, the water temperature estimation process may be accompanied by filtering, and the value obtained by the above formula may be determined as the final estimated water temperature through filtering.

[0128] The junction temperature determination unit 220 may be configured to determine the junction temperature T_1 of the first switching elements S11 and S12 based on the estimated water temperature T_w and the first temperature increment ΔT_1 determined above, or determine the junction temperature T_3 of the third switching element S31 based on the determined estimated water temperature T_w and the third temperature increment ΔT_3.

[0129] For example, the junction temperature T_1 of the first switching elements S11 and S12 may be determined as a value obtained by adding the first temperature increment ΔT_1 to the estimated water temperature T_w, and the junction temperature T_3 of the third switching element S31 may be determined as a value obtained by adding the third temperature increment ΔT_3 to the estimated water temperature T_w.

[0130] That is, the junction temperatures of the first switching elements S11 and S12 and the third switching element S31 may be determined by the following formula.

[0131] T_1=ΔT_1+T_w

[0132] T_3=ΔT_3+T_w

[0133] In the case where the power module 100 applicable to the exemplary embodiment of the present invention operates in the second operation mode, the water temperature estimation unit 210 may be configured to determine the estimated water temperature T_w based on the first temperature increment ΔT_1 and the first influence coefficient X about the first switching elements S11 and S12 and the second temperature increment ΔT_2 about the second switching elements S21 and S22. Here, since the second switching elements S21 and S22 are the measurement target of the first temperature sensor 140 and the heat source generating heat, the influence coefficient is not reflected in the second switching elements S21 and S2, and the second temperature increment ΔT_2 may be directly reflected in the determination of the estimated water temperature T_w.

[0134] For example, the water temperature estimation unit 210 may be configured to subtract a value X*ΔT_1 obtained by reflecting the first influence coefficient X in the first temperature increment ΔT_1 and a second temperature increment ΔT_2 from a measurement result T_sense2 of the first temperature sensor 140 provided at the second switching elements S21 and S22 to determine the estimated water temperature T_w.

[0135] That is, the estimated water temperature T_w can be determined by the following formula.

[0136] T_w=T_sense2-(X*ΔT_1+ΔT_2)

[0137] In addition, the water temperature estimation process may be accompanied by filtering, and the value obtained by the above formula may be determined as the final estimated water temperature through filtering.

[0138] The junction temperature determination unit 220 may be configured to determine the junction temperatures of the first switching elements S11 and S12 based on the estimated water temperature T_w and the first temperature increment ΔT_1 determined above, or determine the junction temperatures of the second switching elements S21 and S22 based on the determined estimated water temperature T_w and the second temperature increment ΔT_2.

[0139] For example, the junction temperature T_1 of the first switching elements S11 and S12 may be determined as a value obtained by adding the first temperature increment ΔT_1 to the estimated water temperature T_w, and the junction temperature of the second switching elements S21 and S22 may be determined as a value obtained by adding the second temperature increment ΔT_2 to the estimated water temperature T_w.

[0140] That is, the junction temperatures of the first switching elements S11 and S12 and the second switching elements S21 and S22 may be determined by the following formula.

[0141] T_1=ΔT_1+T_w

[0142] T_2=ΔT_2+T_w

[0143] Furthermore, because the first temperature sensor 140 is provided at the second switching elements S21 and S22 , the junction temperature T_2 of the second switching elements S21 and S2 may be determined to be the same as the measurement result T_sense2 of the first temperature sensor 40 (ie, T_2=T_sense2 ).

[0144] In the following, reference will be made to Fig. 7A and Figure 7B A junction temperature determination result of the temperature determination apparatus for a power module according to an exemplary embodiment of the present invention is described.

[0145] Fig. 7A and Figure 7BA schematic diagram describing a junction temperature determination result according to an exemplary embodiment of the present invention by comparing with a comparative example.

[0146] Fig. 7A and Figure 7B is a graph showing the junction temperature determination result for a cooling water non-operating period (eg, EWP non-operating), wherein the horizontal axis represents time and the vertical axis represents temperature.

[0147] first, Fig. 7A Shown is a result of not applying the temperature determination according to the exemplary embodiment of the present invention but determining the junction temperature by the second water temperature sensor for measuring the temperature of cooling water.

[0148] In this case, under the condition that the cooling water is not operated, since the water temperature measured by the second temperature sensor cannot represent the temperature of any switching element, the result measured by the first temperature sensor 140 and the predicted junction temperature based on the measured water temperature may not be consistent.

[0149] Therefore, even in a case where an over-temperature protection operation is actually required due to high heat generation, the predicted junction temperature is found to be a lower value, and thus the over-temperature protection operation may not be performed.

[0150] on the other hand, Figure 7B The result of applying the temperature determination according to the exemplary embodiment of the present invention to determine the junction temperature by estimating the water temperature is shown.

[0151] In this case, with Fig. 7A Differently, since the estimated water temperature is used instead of the water temperature measured by the second temperature sensor, the temperature on the switching element side (i.e., the temperature near the radiator) can be relatively accurately reflected when determining the junction temperature, and the junction temperature can be relatively accurately determined even when the cooling water is not operating.

[0152] Since the second water temperature sensor generally measures the temperature of the cooling water flowing into the power module 100, there is a difference with the actual temperature of the switching element. However, the estimated water temperature according to the exemplary embodiment of the present invention is determined in consideration of the heat generation of the switching elements S11, S12, S21, S22, and S31, and thus can relatively accurately represent the actual temperature of the switching element.

[0153] Therefore, the over-temperature protection operation can be performed at a relatively accurate time point, which is different from not performing over-temperature protection even if the actual temperature is higher. Fig. 7A Unlike the comparison example, it is possible to check whether the predicted junction temperature exceeds the reference temperature, so that an overtemperature protection operation can be performed ( Figure 7B 350 to 400 on the horizontal axis).

[0154] As described above, according to various embodiments of the present invention, by estimating the water temperature to determine the junction temperature of the power module, the reliance on the water temperature sensor for detecting the cooling water temperature in the process of determining the junction temperature can be reduced. Therefore, the provision of the water temperature sensor and the connector for connecting the water temperature sensor can be omitted, thereby reducing costs and simplifying the circuit.

[0155] Furthermore, the estimated water temperature may be utilized to improve the determination accuracy of the junction temperature, thereby expanding the normal operating range of the over-temperature protection of the power module.

[0156] Furthermore, even if all the switching elements are not provided with sensors for detecting the junction temperature, the junction temperatures of all the switching elements can be determined, thereby improving the over-temperature protection performance of the power module.

[0157] Effects that can be obtained in the exemplary embodiments of the present invention are not limited to the above-mentioned effects, and other effects that are not mentioned can be clearly understood by those skilled in the art through the following description.

[0158] In addition, terms related to control devices (e.g., "controller", "control device", "control unit", "control device", "control module" or "server", etc.) refer to hardware devices including memory and processors, and the processor is configured to execute one or more steps interpreted as an algorithm structure. The memory stores the algorithm steps, and the processor executes the algorithm steps to perform one or more processes of the method according to various exemplary embodiments of the present invention. The control device according to the exemplary embodiment of the present invention can be implemented by a non-volatile memory and a processor, the non-volatile memory is configured to store an algorithm for controlling the operation of various components of the vehicle or data about software commands for executing the algorithm, and the processor is configured to perform the above operations using data stored in the memory. The memory and the processor can be separate chips. Alternatively, the memory and the processor can be integrated in a single chip. The processor can be implemented as one or more processors. The processor can include various logic circuits and operation circuits, can be configured to process data according to a program provided from the memory, and can be configured to generate a control signal according to the processing result.

[0159] The control device may be at least one microprocessor operated by a predetermined program, which may include a series of commands for executing the methods included in the aforementioned various exemplary embodiments of the present invention.

[0160] The above invention can also be implemented as a computer-readable code on a computer-readable recording medium. A computer-readable recording medium is any data storage device that can store data that can be subsequently read by a computer system and can store and execute program instructions that can be subsequently read by a computer system. Examples of computer-readable recording media include hard disk drives (HDDs), solid-state disks (SSDs), silicon disk drives (SDDs), read-only memories (ROMs), random access memories (RAMs), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, etc., and implementations as carrier waves (e.g., transmissions over the Internet). Examples of program instructions include machine language codes, such as those generated by a compiler, and high-level language codes that can be executed by a computer using an interpreter, etc.

[0161] In various exemplary embodiments of the present invention, each of the above-described operations may be performed by a control device, and the control device may be configured by a plurality of control devices or an integrated single control device.

[0162] In various exemplary embodiments of the present invention, the memory and the processor may be provided as one chip, or provided as separate chips.

[0163] In various exemplary embodiments of the present invention, the scope of the present invention includes software or machine-executable commands (e.g., operating systems, applications, firmware, programs, etc.) for enabling the steps of methods according to the various embodiments to be executed on a device or computer, including non-transitory computer-readable media on which such software or commands are stored and can be executed on the device or computer.

[0164] In various exemplary embodiments of the present invention, the control device may be implemented in the form of hardware or software, or may be implemented in a combination of hardware and software.

[0165] Furthermore, terms such as “unit”, “module” and the like included in the specification mean a unit for processing at least one function or operation, which may be implemented by hardware, software or a combination thereof.

[0166] For ease of interpretation and accurate definition in the appended claims, the terms "upper", "lower", "inner", "outer", "upper", "lower", "upward", "downward", "front", "rear", "rear", "inner", "external", "inwardly", "outwardly", "inner", "outer", "inner", "external", "forward" and "rearward" are used with reference to the features of the exemplary embodiments shown in the figures to describe the location of such features. It should be further understood that the term "connected" or its derivatives refer to both direct and indirect connections.

[0167] The term "and / or" may include a combination of multiple related listed items or any one of the multiple related listed items. For example, "A and / or B" includes all three situations such as "A", "B" and "A and B".

[0168] In this specification, a singular expression includes a plural expression unless the context clearly indicates otherwise.

[0169] In an exemplary embodiment of the present invention, “at least one of A and B” may refer to “at least one of A or B” or “at least one of a combination of at least one of A and B”. Furthermore, “one or more of A and B” may refer to “one or more of A or B” or “one or more of a combination of one or more of A and B”.

[0170] In the exemplary embodiments of the present invention, it should be understood that terms such as "include" or "have" are intended to indicate the presence of features, values, steps, operations, elements, parts, or a combination thereof described in the specification, and do not exclude the possibility of adding or existing one or more other features, values, steps, operations, elements, parts, or a combination thereof.

[0171] For the purpose of illustration and description, the above description of specific exemplary embodiments of the present invention has been presented. These descriptions are not intended to be exhaustive, nor are they intended to limit the present invention to the precise form disclosed, and it is clear that many modifications and changes are possible based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that other technical personnel in the field can realize and utilize various exemplary embodiments of the present invention and various alternative forms and modified forms thereof. The scope of the present invention is intended to be limited by the appended claims and their equivalent forms.

Claims

1. A temperature determination device for a power module, the power module comprising a plurality of switch elements and a first temperature sensor, the first temperature sensor being disposed at a portion of the plurality of switch elements and configured to measure the temperature of the switch elements, the temperature determination device being used to predict the temperature of the power module cooled by cooling water, the temperature determination device include: a water temperature estimation unit configured to: determine a temperature increment of each of the plurality of switching elements based on operation information of the plurality of switching elements; determining an estimated water temperature of the cooling water based on the temperature increment and preset influence coefficients respectively corresponding to the remaining switch elements not provided with the first temperature sensor; as well as A junction temperature determination unit is configured to determine a junction temperature of at least one of the plurality of switching elements based on the estimated water temperature.

2. The temperature determination device for a power module according to claim 1, in, The temperature increase is determined according to power loss and thermal resistance caused by the operation of the power module.

3. The temperature determination device for a power module according to claim 1, in, The influence coefficient is preset based on an experimental value regarding a correlation between heat generation of a switching element, among the plurality of switching elements, to which the first temperature sensor is not provided and a measurement result of the first temperature sensor.

4. The temperature determination device for a power module according to claim 1, in, The junction temperature determination unit is configured to determine the junction temperature of at least one of the plurality of switching elements in further consideration of a measurement result of a second temperature sensor for measuring the temperature of cooling water.

5. The temperature determination device for a power module according to claim 1, in, The plurality of switch elements include first and second switch elements of different types, and a third switch element that determines whether the second switch element is to be operated according to an on / off state, The power module includes a first operating mode in which the first switching element operates when the third switching element is turned on, or a second operating mode in which the second switching element operates together with the first switching element when the third switching element is turned off. The water temperature estimation unit is configured to determine an estimated water temperature according to one of a first operation mode and a second operation mode.

6. The temperature determination device for a power module according to claim 5, in, The first switching element is implemented by using silicon carbide.

7. The temperature determination device for a power module according to claim 6, in, The first temperature sensor is arranged on the second switch element.

8. The temperature determination device for a power module according to claim 5, in, In response to the operation mode of the power module being the first operation mode, the water temperature estimation unit is configured to determine an estimated water temperature based on a first temperature increment and a first influence coefficient regarding the first switching element and a third temperature increment and a third influence coefficient regarding the third switching element.

9. The temperature determination device for a power module according to claim 8, in, The water temperature estimation unit is configured to determine the estimated water temperature by subtracting a value obtained by reflecting the first influence coefficient in the first temperature increment and a value obtained by reflecting the third influence coefficient in the third temperature increment from a measurement result of the first temperature sensor.

10. The temperature determination device for a power module according to claim 8, in, The junction temperature determination unit is configured to: determine the junction temperature of the first switching element in the junction temperature based on the determined estimated water temperature and the first temperature increment; determine the junction temperature of the third switching element in the junction temperature based on the determined estimated water temperature and the third temperature increment.

11. The temperature determination device for a power module according to claim 5, in, In response to the operation mode of the power module being the second operation mode, the water temperature estimation unit is configured to determine an estimated water temperature based on a first temperature increment and a first influence coefficient regarding the first switching element and a second temperature increment regarding the second switching element.

12. The temperature determination device for a power module according to claim 11, in, The water temperature estimation unit is configured to determine the estimated water temperature by subtracting a value obtained by reflecting the first influence coefficient in the first temperature increment and the second temperature increment from a measurement result of the first temperature sensor.

13. The temperature determination device for a power module according to claim 11, in, The junction temperature determination unit is configured to determine a junction temperature of the first switching element based on the determined estimated water temperature and the first temperature increment.

14. The temperature determination device for a power module according to claim 11, in, The junction temperature determination unit is configured to determine a temperature according to a measurement result of the first temperature sensor as a junction temperature of the second switching element in the junction temperature.

15. The temperature determination device for a power module according to claim 11, in, The junction temperature determination unit is configured to determine a junction temperature of the second switching element in the junction temperature based on the determined estimated water temperature and the second temperature increment.

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