Method and device for determining a parameter of a switching element

Abstract

Method (100) for determining a first parameter (P1) of a first switching element (250) with a controllable current source driver (210) with the steps: applying (110) a predeterminable constant first identification current (I1_id) to the gate (252) of the first switching element (250) for a predeterminable first identification time (t1_id), determining (120) the voltage values ​​of the profile of the resulting first identification gate voltage (UG1_id) over the first identification time (t1_id) and determining (125) the first parameter (P1) as a function of the determined voltage values ​​of the profile of the resulting first identification gate voltage (UG1_id).

Description

The invention relates to a method and a device for determining a parameter of a switching element. The invention further relates to a drive train having a corresponding device and to a vehicle having a drive train, and also to a computer program and a machine-readable storage medium.Prior ArtGate drivers are used to drive switching elements, preferably semiconductor switches. Tolerances of the semiconductor switches lead to different switching characteristics of the individual switching elements. In particular when activating parallel-connected switching elements, this leads to different loads on the individual switching elements, for example since the switching element that is initially switched on carries the entire current of the parallel-connected switching elements for a short time. This leads to high additional outlay in the design of corresponding circuits, for example the provision of balancing resistors, the provision of a slower switching time taking into account the possible tolerances and thus increased losses and thus the provision of more space requirement for the switching elements in order to ensure sufficient cooling of the switching elements. Tolerances of the parameters of the switching elements, preferably of the semiconductor switches, such as different threshold voltages Vth of the semiconductor switches (such as SiC MOSFETs, IGBTs, among others), may have a negative influence on the switching behavior of the switching elements in the power electronics, preferably in power electronics components, such as in power modules. Thus, different switching behavior can occur during the operation of a switch which optionally comprises a plurality of parallel-connected switching elements, for example integrated MOSFETs, or during the parallel connection of two individual switches which each comprise at least one switching element. This can lead to different switching times and switching speeds. This results in different thermal loads per switching element. Likewise, different EMC disturbances or operating parameters to be taken into account during operation result, for example the maximum of the drain-source voltage, the voltage across the switching element. Therefore, there is a need for methods and devices that reliably determine the different parameters and allow operation taking into account the parameters with which the dispersion of the power losses of parallel-operated switching elements is reduced.Disclosure of the InventionA method for determining a first parameter of a first switching element with a controllable current source driver is provided. The method comprises the steps of:applying a predeterminable constant first identification current to the gate of the first switching element for a predeterminable first identification time;determining the voltage values of the course of the resulting first identification gate voltage over the first identification time,determining the first parameter as a function of the determined voltage values of the profile of the resulting first identification gate voltage.Consequently, a method for determining or ascertaining a first parameter, preferably a first electrical or physical parameter, of a first switching element having a controllable current source driver is provided. A first parameter is, for example, preferably a voltage threshold value of a gate voltage at which the first switching element starts to conduct a current. The reaching of this voltage thus influences the beginning or the starting time of the switching-on process of the first switching element. Another exemplary parameter is the size of the gate-source capacitance. When the gate-source capacitance of the first switching element is charged, the switching element is fully closed and its resistance to current is minimal. The duration of the charging thus influences the speed of the switching on. A first switching element is preferably a semiconductor switch, an IGBT or a MOSFET, made of silicon or silicon carbide or gallium nitride or other usual semiconductor materials. Preferably, a gate driver is or comprises a current source driver or a voltage source driver. The gate driver is preferably an electronic component in a power converter, inverter, inverter, converter or DC-DC converter. The gate driver is preferably integrated into a power converter which is intended to be operated in a vehicle or the gate driver is integrated into a power converter in a vehicle. Preferably, the gate driver is an electric circuit that receives an input signal corresponding to a target switching state of the first switching element. The target switching states preferably comprise an on state and an off state. Accordingly, the input signal preferably comprises a high level and a low level. As an output signal, a gate driver outputs an output signal generated depending on the input signal to the gate of the first switching element to drive the first switching element according to the target state. Preferably, the signal is a voltage or a current. A current source driver is configured to output a predefinable current as an output signal. Depending on the state of charge of the gate-source capacitance of the driven first switching element, a gate voltage resulting at the gate changes during the driving by means of the current source driver. A voltage source driver is configured to output a predefinable voltage as an output signal. Depending on the state of charge of the gate-source capacitance of the driven first switching element, a resulting gate current flowing into the gate changes during the driving by means of the voltage source driver. A controllable gate driver is preferably configured to specify a plurality of voltage values or current values that can be selected or specified differently, preferably voltage values or current values of any desired different height. A controllable gate driver is preferably programmable and can preset the predeterminable voltage values or current values for predeterminable time periods or time segments or preset voltage value or current value profiles or voltage value or current value curves at predeterminable times. The method comprises the steps of: applying a predefinable constant first identification current to the gate of the first switching element for a predefinable first identification time. A first identification current is applied to the gate or the gate terminal of the first switching element by means of the current source driver. The identification current is preferably selected to be constant and so small that observation of the switching behavior, preferably observation, recording, ascertainment or measurement of the profile of the gate-source voltage, of the drain-source current and or of the drain-source voltage, becomes readily possible. The slower the switching on or switching off of the first switching element, the more undisturbed the voltages and currents mentioned. More accurate measured values of the voltages and currents mentioned can thus be detected, which in turn reflect the physical parameters of the first switching element. The terms selected for the designation of the voltages and currents, for example. Gate-source voltage or drain-source voltage denote the voltages or currents which can be measured between the terminals gate, source and drain characterizing a switching element. Preferably, the names base, emitter, collector corresponding for a corresponding bipolar transistor are included interchangeably in the context of this description in a description with respect to one of the names gate, source or drain. The skilled person is familiar with different possibilities for determining or measuring these voltages and currents. The terms in connection with the determination of the voltages and currents explicitly also comprise measurements at another point of a power electronics system or circuit, which are suitable for characterizing the stated voltages and or currents. The predefinable first identification time is selected to be so great that switching on or switching off of the first switching element is certainly completely carried out as a function of the magnitude of the identification current. Thus, the entire switching operation can be observed. As a further step, the voltage values of the course of the resulting first identification gate voltage over the first identification time are determined. The first identification gate voltage is the gate-source voltage that results during the first identification time between the gate and source terminals of the first switching element due to the application of the first identification current. Depending on the ascertained voltage values of the curve of the first identification gate voltage, preferably from the magnitude of the voltage values and the curve, in particular the gradient of the first identification gate voltage, a first parameter of the first switching element is ascertained in a following step. Preferably, a first parameter of the first switching element is determined or ascertained before a power converter is put into operation, which is preferably provided for a vehicle, or at predeterminable regular time intervals, for example weekly or monthly before or after operation of the vehicle, or as part of maintenance or inspection, preferably when a vehicle is located at a workshop.Advantageously, a method is provided which enables a reliable determination of a specific parameter of a specific switching element.In one configuration, a further method step comprises applying a first drive current for a predefinable first drive time as a function of the ascertained first parameter to the gate of the first switching element for operating the first switching element. Preferably, a predefinable constant first identification current is applied to the gate of the first switching element for a predefinable first identification time and a first control current is applied to the gate of the first switching element for a predefinable first control time as a function of the ascertained first parameter for operating the first switching element by means of the same current source driver. The operation of the first shift element is preferably carried out during a driving operation of a vehicle. The operation of the first switching element preferably comprises switching on or switching off the first switching element, preferably the operation of the first switching element in an electronic device, for example in a power converter, a DC-to-DC converter or an inverter for, preferably continuously, providing a converted current or a converted voltage. A current converter is preferably designed as a DC-DC converter or as an inverter. The first control current to be applied for this purpose and the predefinable first control time differ by orders of magnitude from the first identification current and the first identification time. During operation or during operation of the first shift element, preferably resulting shift losses should be avoided to the greatest possible extent, so that shifting as quickly as possible is sought. Therefore, the first activation current to be applied is preferably as large as possible and the predefinable first activation time is as short as possible. The first drive current to be applied and the predefinable first drive time are predefined as a function of the ascertained first parameter.Advantageously, a method for operating a first switching element as a function of a determined first parameter is provided.In one configuration, the first identification time is longer than the predefinable activation time for operating the first switching element by a factor of 10 to 10000, preferably 100 to 1000, preferably 400. As already mentioned above, the first identification time is longer so that fewer disturbances are superimposed on the identification gate voltage, whereas the activation time is shorter so that the switching losses are as low as possible during operation.Advantageously, an improved method is provided.In one configuration, during the application of a predefinable constant first identification current to the gate of the first switching element, a predefinable voltage is present between the drain and the source of the switching element for the first identification time, and no load current flows between the drain and the source of the switching element. During the determination of the voltage values of the course of the resulting first identification gate voltage over the first identification time, a connected load would lead to superimpositions and interference and would distort the determined voltage values. Therefore, during the determination of the first parameter of the first switching element, a load current through the switching element is prevented or minimized. The voltage is preferably present across the drain and source of the first switching element.Advantageously, an improved method is provided.In one configuration, the first identification current is smaller by approximately a factor of 0.1 to 0.001 than the first drive current for operating the first switching element. As already mentioned above, the first identification current is smaller so that fewer disturbances are superimposed on the identification gate voltage, whereas the activation current is larger so that the switching process takes place more quickly during operation and the switching losses are as low as possible.Advantageously, an improved method is provided.In one configuration, the first parameter to be determined is a first identification threshold voltage of the first switching element, wherein the first identification threshold voltage is determined as the voltage value of the profile of the resulting first identification gate voltage at which the gradient of the first identification gate voltage over the first identification time reaches a first minimum. Preferably, the first threshold voltage of the first switching element is determined as a first parameter as a function of the first identification threshold voltage, preferably by multiplying the first identification threshold voltage by a first factor.Consequently, the voltage values of the course of the resulting first identification gate voltage over the first identification time are first ascertained. The gradients of the course of the resulting first identification voltage over the first identification time are then determined. In a further step, the voltage value of the course of the resulting first identification gate voltage is determined, at which a gradient of the first identification gate voltage over the first identification time reaches a first minimum. This voltage value is determined as an identification threshold voltage. The identification threshold voltage determined can preferably be determined by multiplication by a first predefinable factor as a first parameter as a threshold voltage, as results during operation of the switching element. A specific value is preferably used as the first factor, which is determined from a condition or a preliminary diagnosis of a reference shift element and is stored, preferably in a characteristic diagram, in a retrievable manner.Advantageously, a method for determining a first parameter, the identification threshold voltage or the threshold voltage, is provided.In one configuration, the first parameter to be determined is a first identification plateau voltage of the first switching element. The first identification plateau voltage is determined as the voltage value of the curve of the resulting first identification gate voltage at which the first identification gate voltage reaches a first maximum over the first identification time. Preferably, the first plateau voltage of the first switching element is determined as the first parameter as a function of the first identification plateau voltage, in particular by multiplying the first identification plateau voltage by a second factor.Consequently, the voltage values of the course of the resulting first identification gate voltage over the first identification time are first ascertained. In a further step, the voltage value of the course of the resulting first identification gate voltage is determined, at which a voltage value of the first identification gate voltage reaches a first maximum over the first identification time. This voltage value is determined as an identification plateau voltage. The identification plateau voltage determined can preferably be determined by multiplication by a second predefinable factor as a first parameter as a plateau voltage, as results during operation of the switching element. A specific value is preferably used as the second factor, which is determined from a condition or a preliminary diagnosis of a reference shift element and is stored, preferably in a characteristic diagram, in a retrievable manner.Advantageously, a method for determining a first parameter, the identification plateau voltage or the plateau voltage, is provided.In one embodiment, the parameter to be determined is a first transconductance. Preferably, for the determination of the transconductance, the identification threshold voltage and or the first identification plateau voltage, or preferably the difference of the identification plateau voltage and the identification threshold voltage, is taken into account and determined as a function thereof. These values are stored, preferably in a characteristic diagram, retrievable for the further operation and the actuation of the shift elements.The invention further relates to a device for determining a first parameter of a first shifting element, having a control device which is configured to carry out a method described above. The control device preferably comprises a computer unit or a μC, or a processor. The control device is preferably configured to actuate the current source driver and a voltage measurement device in such a way that the described method steps are carried out. Advantageously, an apparatus for implementing the method is provided. The apparatus preferably comprises a gate driver having the control device, the current source driver and or the voltage measurement device. The gate driver is preferably designed as an ASIC, that is to say as an application-specific integrated circuit which is configured to carry out at least one or all of the method steps.The invention further relates to a drive train having a described device. The drive train is preferably designed for the operation of an electrified vehicle or serves, for example, for driving an electric vehicle. The drive train preferably comprises the device, which is preferably arranged within a converter, a DC-DC converter, an inverter or power electronics, the inverter, a traction battery and or an electric machine for driving the vehicle. Advantageously, an improved drive train is provided. By means of the method, the device and the drive train, a more lasting operation of the drive train is made possible.The invention further relates to a vehicle having a drive train described. Advantageously, a vehicle is thus provided which comprises a device with which a parameter of a first shift element can be determined.The invention further relates to a computer program comprising instructions which cause the apparatus to execute the method steps.The invention further relates to a computer-readable medium comprising instructions which, when executed by a device, cause the device to carry out the method steps of the method.It is understood that the features, properties and advantages of the method according to the invention apply or are correspondingly applicable to the device or the drive train and the vehicle and vice versa.Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGThe invention will be explained in more detail below with reference to some figures, in which: FIG. 1 shows a schematic illustration of a current source driver having a first and a second connected switching element. FIG. 2 shows a schematic illustration of an equivalent circuit diagram for a switching element FIG. 3 shows a schematically illustrated profile of a first identification current and a replica of a first identification gate voltage FIG. 4 shows a schematically illustrated profile of currents and voltages during a switching-on process of a switching element FIG. 5 shows a schematically illustrated profile of currents and voltages during a switching-off process of a switching element FIG. 6 shows a schematically illustrated flow chart for a method for determining a first parameter of a first switching element. FIG. 7 shows a schematically illustrated vehicle having a drive train,Embodiments of the InventionFIG. 1 shows a schematic illustration of a current source driver 210, 310 having a first switching element 250 and a second switching element 350. The gate 252 of the first switching element is preferably connected to the current source driver 210, 310, preferably via a first output. The gate 352 of the second switching element is preferably connected to the current source driver 210, 310, preferably via a second output. The current source driver 210, 310 preferably comprises further outputs, which can be connected to a third or fourth switching element 270 or 280. Preferably, a current source driver is configured by means of two differently programmable outputs to drive a first and a second switching element independently. Alternatively, individual current source drivers 210, 310, i.e., preferably a first current source driver 210 and a second current source driver 310, may also be connected to an individual one of the four switching elements 250, 350, 270, 280, for example. Preferably, the first and second switching elements 250, 350 are connected in parallel. The third and the fourth switching elements 270, 280 are preferably connected in parallel. The four switching elements are arranged in FIG. 1 by way of example as a half bridge which is supplied with energy via a supply voltage source 260. The output of the half bridge preferably forms a center tap of the half bridge 265, at which center tap the positive or negative potential of the supply voltage source 265 is provided depending on the switch position of the four switching elements.FIG. 2 shows a schematic illustration of an equivalent circuit diagram for a switching element. On the left-hand side at the top of FIG. 2, a circuit symbol for a field effect transistor, for example an SiC MOSFET, is shown with the terminals S (source), D (drain) and G (gate). Analogously below this, a switching symbol for a further transistor, for example an IGBT, is shown with the connections C (collector), E (emitter) and B (base). Common to both switching elements is that a current flow between drain and source or collector and emitter is driven via the gate or base control terminal. For the field effect transistor, a substitute circuit diagram is shown by way of example on the right-hand side of the illustration, wherein the parasitic properties of the transistor are illustrated. Preferably, a gate-source capacitance Cx_GS, a gate-drain capacitance Cx_D, and a drain-source capacitance Cx_Ds are shown, which represent parasitic properties between the terminals of a switching element, for example.FIG. 3 shows a schematically illustrated profile of an identification current and an identification gate voltage. The small "x" in the reference numerals stands as place holders for a "1" or "2" to show that their values may differ depending on the reference to a first or second switching element. In the upper region of FIG. 3, a profile of a predefinable constant identification current Ix_id is depicted, as it is applied to a gate 252, 352 of a switching element 250, 350 for a predefinable identification time tx_id for determining a parameter P 1, P 2 of a switching element 250, 350. In the area below, a resulting identification gate voltage UGx_id is schematically shown over the identification time tx_id, on the basis of which a parameter P 1, P 2 of a switching element 250, 350 is determined. The identification time tx_id is preferably approximately between 50 and 300 μs, preferably between 90 and 150 μs, preferably 120 μs. The identification current identification current is preferably 0.5 to 5 mA, preferably 1 to 3 mA, preferably 1.5 mA. An identification threshold voltage Vx_th_id of a switching element 250, 350 is preferably determined as a function of the profile of the resulting identification gate voltage UGx_id. An identification plateau voltage Vx_pl_id of a switching element 250, 350 is preferably determined as a function of the profile of the resulting identification gate voltage UGx_id. The duration of the identification precharge tx_id_pre is obtained as a time period between the beginning of the identification time tx_id and the time of reaching the identification threshold voltage Vx_th_id. The duration of the identification commutation tx_id_com is obtained as a time period between the time when the identification threshold voltage Vx_th_id is reached and the time when the identification plateau voltage Vx_pl_id is reached. The duration of the identification recharging tx_id_post is obtained as a time period between the time of reaching the identification plateau voltage Vx_pl_id and the end of the identification time tx_id.FIG. 4 shows a schematically illustrated profile of currents and voltages during a switching-on process of a switching element, that is to say the profile of the currents and voltages during the switching-on. As illustrated in the top graph of FIG. 4, in order to operate and switch on a switching element 250, 260, a drive current Ix_c is applied to the gate 252, 352 of a switching element 250, 350 for a predefinable first drive time tx_c as a function of the ascertained parameter P 1, P 2. Depending on the switching element used or the technology of the switching element used, the activation time tx_c is preferably approximately 1 to 999 ns, preferably 200 to 700 ns, preferably 500 ns. Depending on the switching element used or the technology of the switching element used, the drive current is preferably 100 to 1500 mA, preferably 150 to 1100 mA, preferably 500 mA. The bottom graph of FIG. 4 shows the resulting gate voltage Vx_gs, which preferably rises during the switching-on. The switch-on process preferably comprises the following time segments in succession: the precharging tx_on_pre, the current commutation tx_on_cuco, the voltage commutation tx_on_voco and or the recharging tx_on_post. During the precharging, a preferably positive drive current Ix_c is applied to the gate, the maximum drain-source voltage Vx_ds (second graph from the top of FIG. 4 ) is applied to the switching element, no drain-source current Ix_d yet flows (third graph from the top of FIG. 4 ) and the gate voltage Vx_gs rises. During the current commutation, a preferably positive drive current is furthermore applied to the gate, the maximum drain-source voltage is still present at the switching element, the drain-source current forms and rises to its maximum and the gate voltage rises further. During the voltage commutation, a preferably positive drive current is furthermore applied to the gate, the drain-source voltage decreases and reaches its minimum, the drain-source current remains at its maximum and the gate voltage essentially retains its value. During recharging, a preferably positive drive current is still applied to the gate, the drain-source voltage maintains its minimum value, the drain-source current remains at a maximum, and the gate voltage continues to increase. The, preferably positive, drive current in the individual time segments is preferably constant at a current value or it varies depending on the time segment and is predefined depending on the determined parameters P 1, P 2 per time segment, preferably of different sizes (shown dotted in FIG. 4 ). Alternatively, the drive current per time segment can also be predefined as a curve as required.FIG. 5 shows a schematically illustrated profile of currents and voltages during a switching-off process of a switching element, that is to say the profile of the currents and voltages during the switching-off. As illustrated in the top graph of FIG. 5, in order to operate and switch off a switching element 250, 260, a drive current Ix_c is applied to the gate 252, 352 of a switching element 250, 350 for a predefinable first drive time tx_off_c as a function of the ascertained parameter P 1, P 2. The magnitude of the duration of the first activation time tx_off_c preferably corresponds to that of the first activation time tx_c. Depending on the switching element used or the technology of the switching element used, the activation time tx_off_c is preferably approximately 1 to 999 ns, preferably 200 to 700 ns, preferably 500 ns. Depending on the switching element used or the technology of the switching element used, the drive current is preferably 100 to 1500 mA, preferably 150 to 1100 mA, preferably 500 mA. The bottom graph of FIG. 5 shows the resulting gate voltage Vx_gs, which preferably decreases during the switching-off. The switch-off process preferably comprises the following time segments in succession: the pre-discharge tx_off_pre, the voltage commutation tx_off_voco, the current commutation tx_off_cuco, and or the post-discharge tx_off_post. During the pre-discharge, a preferably negative drive current Ix_c is applied to the gate, the minimum drain-source voltage Vx_ds (second graph from the top of FIG. 5 ) is applied to the switching element, the maximum drain-source current Ix_d (third graph from the top of FIG. 5 ) flows, and the gate voltage Vx_gs decreases. During the voltage commutation, a preferably negative drive current is furthermore applied to the gate, the drain-source voltage increases and reaches its maximum, the drain-source current remains at its maximum and the gate voltage essentially retains its value. During the current commutation, a preferably negative drive current is furthermore applied to the gate, the maximum drain-source voltage is furthermore applied to the switching element, the drain-source current is formed back and decreases to its minimum and the gate voltage decreases further. During the post-discharge, a preferably negative drive current is furthermore applied to the gate, the drain-source voltage retains its maximum value, the drain-source current remains minimal and the gate voltage falls further. The, preferably negative, drive current in the individual time segments is preferably constant at a current value or it varies depending on the time segment and is predefined depending on the determined parameters P 1, P 2 per time segment, preferably of different sizes (shown dotted in FIG. 5 ). Alternatively, the drive current per time segment can also be predefined as a curve as required.FIG. 6 shows a schematically illustrated flow chart for a method for determining a parameter of a switching element. Method 100 begins with step 105. In step 110, a predefinable constant first identification current I 1_id is applied to the gate 252 of the first switching element 250 for a predefinable first identification time t 1_id. In step 120, voltage values of the profile of the resulting first identification gate voltage UG1_id over the first identification time t1_id are determined. In step 125, the first parameter P 1 is ascertained as a function of the ascertained voltage values of the profile of the resulting first identification gate voltage UG 1_id. Preferably, a predefinable constant second identification current I2_id is also applied to the gate 352 of the second switching element 350 for a predefinable second identification time t2_id in step 130. In step 140, voltage values of the profile of the resulting second identification gate voltage UG2_id over the second identification time t2_id are preferably determined. Preferably, in step 150, the second parameter P 2 is determined as a function of the determined voltage values of the profile of the resulting second identification gate voltage UG 2_id. Preferably, for operating the first switching element 250, in step 160 a first control current I1_c is applied to the gate 252 of the first switching element for a predeterminable first control time t1_c as a function of the determined first parameter P1. In step 170, a second drive current I2_c is preferably applied to the gate 352 of the second switching element for operating the second switching element 350 as a function of the ascertained first and second parameters P1, P2. The method ends with step 175.FIG. 7 shows a schematically illustrated vehicle 400 having a drive train 300. The illustration shows, by way of example, a vehicle with four wheels 402, wherein the invention can likewise be used in any vehicle with any number of wheels on a country basis, on water basis and in the air. The drive train preferably comprises a traction battery 305 for supplying the electric drive with energy, power electronics or an inverter 310 for converting the electric energy from the traction battery 305 for supplying an electric machine 315 and or the electric machine 315 for driving the vehicle 400. Preferably, inverter 310 comprises a device 320. The device 320 serves for determining a parameter Px of a switching element 250, 350 and comprises a control device 325 which is configured to carry out a described method.

Claims

Method (100) for determining a first parameter (P1) of a first switching element (250), having a controllable current source driver (210), having the steps: applying (110) a predefinable constant first identification current (I1_id) to the gate (252) of the first switching element (250) for a predefinable first identification time (t1_id), ascertaining (120) the voltage values of the profile of the resulting first identification gate voltage (UG1_id) over the first identification time (t1_id), ascertaining (125) the first parameter (P1) as a function of the ascertained voltage values of the profile of the resulting first identification gate voltage (UG1_id).Method according to Claim 1, having the further step: applying (160) a first drive current (I1_c) for a predeterminable first drive time (t1_c) as a function of the determined first parameter (P1) to the gate (252) of the first switching element for operating the first switching element (250).Method according to Claim 2, wherein the first identification time (t1_id) is longer than the predefinable actuation time (t1_c) for operating the first switching element (250) by a factor of 10 to 10000.Method according to one of the preceding claims, wherein during the application (110) of the predeterminable constant first identification current (I1_id) to the gate (252) of the first switching element (250), a predeterminable voltage is present between drain and source of the switching element (250) for the first identification time (t1_id) and no load current flows between drain and source of the switching element (250).Method according to one of Claims 2 to 4, wherein the first identification current (I1_id) is smaller than the first drive current (I1_c) for operating the first switching element (250) by approximately the factor 0.1 to 0.001.Method according to one of the preceding claims, wherein the first parameter (P1) to be determined is a first identification threshold voltage (V1_th_id) of the first switching element (250), wherein the first identification threshold voltage (V1_th_id) is determined as the voltage value of the profile of the resulting first identification gate voltage (UG1_id), at which the gradient of the first identification gate voltage (UG1_id) over the first identification time (t1_id) reaches a first minimum, wherein in particular the first parameter (P1) determined is the first threshold voltage (V1_th) of the first switching element (250) as a function of the first identification threshold voltage (V1_th_id), in particular by the first identification threshold voltage (V1_th_id) being multiplied by a first factor.Method according to one of the preceding claims, wherein the first parameter (P1) to be determined is a first identification plateau voltage (V1_pl_id) of the first switching element (250), wherein the first identification plateau voltage (V1_pl_id) is determined as the voltage value of the profile of the resulting first identification gate voltage (UG1_id), at which the first identification gate voltage (UG1_id) reaches a first maximum over the first identification time (t1_id), wherein in particular the first plateau voltage (V1_pl) of the first switching element (250) is determined as the first parameter (P1) as a function of the first identification plateau voltage (V1_pl_id), in particular, by multiplying the first identification plateau voltage (V 1_pl_id) by a second factor.Device (320) for determining a first parameter (P1) of a first switching element (250), having a control device (325) which is configured to carry out a method (100) according to one of the preceding claims 1 to 7.Drive train (300) comprising a device (320) according to claim 8.Vehicle (400) comprising a drive train (300) according to claim 9.A computer program comprising instructions for causing the apparatus of claim 8 to perform the method steps of any one of claims 1 to 7.A computer readable medium comprising instructions which, when executed by an apparatus according to claim 8, cause the apparatus to perform the method steps according to any one of claims 1 to 7.

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