Method and apparatus for determining a parameter of a switching element

Abstract

A method (100) for determining a first parameter (P1) of a first switching element (250) having a controllable current source driver (210), said method comprising the following steps: applying (110) a specifiable constant first identification current (I1_id) to the gate (252) of the first switching element (250) for a specifiable 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) and 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).

Description

[0001] Description

[0002] title

[0003] Procedures and to a parameter of a switching element

[0004] The invention relates to a method and a device for determining a parameter of a shift element. Furthermore, the invention relates to a drive train with a corresponding device and a vehicle with a drive train, as well as a computer program and a machine-readable storage medium.

[0005] State of the art

[0006] Gate drivers are used to control switching elements, preferably semiconductor switches. Tolerances of the semiconductor switches lead to different switching behavior of the individual switching elements. In particular, when controlling switching elements connected in parallel, this leads to different loads on the individual switching elements, e.g. because the switching element that switches on first briefly carries the entire current of the parallel-connected switching elements. This leads to high additional effort in the design of corresponding circuits, e.g. 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 for the switching elements to ensure sufficient cooling of the switching elements. Tolerances of the parameters of the switching elements, preferably the semiconductor switches, such asDifferent threshold voltages Vth of semiconductor switches (such as SiC MOSFETs, IGBTs, etc.) can have a negative influence on the switching behavior of the switching elements in power electronics, particularly in power electronic components such as power modules. For example, different switching behavior can occur when operating a switch that may comprise several switching elements connected in parallel, e.g. integrated MOSFETs, or when two individual switches, each comprising at least one switching element, are connected in parallel. This can lead to different switching times and switching speeds. This results in different thermal loads for each switching element. Likewise, different EMC interference or operating parameters that must be taken into account during operation, e.g. the maximum 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 enable operation taking the parameters into account, thus reducing the dispersion of the power losses of switching elements operated in parallel.

[0007] Disclosure of the invention

[0008] A method for determining a first parameter of a first switching element with a controllable current source driver is provided. The method comprises the steps:

[0009] Applying a predeterminable constant first identification current to the gate of the first switching element for a predeterminable first identification time;

[0010] Determining the voltage values ​​of the curve of the resulting first identification gate voltage over the first identification time,

[0011] Determining the first parameter as a function of the determined voltage values ​​of the curve of the resulting first identification gate voltage.

[0012] Consequently, a method is provided for determining or ascertaining a first parameter, preferably a first electrical or physical parameter, of a first switching element with a controllable current source driver. A first parameter is, for example, preferably a voltage threshold of a gate voltage at which the first switching element begins to conduct a current. Reaching this voltage thus influences the beginning or start time of the turn-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 the current is minimal. The duration of the charging thus influences the speed of turn-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 common semiconductor materials. A gate driver is preferably or comprises a current source driver or a voltage source driver. The gate driver is preferably an electronic component in a power converter, inverter, converter, or DC-DC converter. The gate driver is preferably integrated into a power converter that is to be operated in a vehicle, or the gate driver is integrated into a power converter in a vehicle. The gate driver is preferably an electrical circuit that receives an input signal corresponding to a desired switching state of the first switching element. The desired switching states preferably include an on state and an off state. Accordingly, the input signal preferably includes a high level and a low level.As an output signal, a gate driver outputs an output signal generated as a function of the input signal to the gate of the first switching element in order to control the first switching element in accordance with the desired state. The signal is preferably a voltage or a current. A current source driver is configured to output a predeterminable current as an output signal. Depending on the charge state of the gate-source capacitance of the controlled first switching element, a gate voltage resulting at the gate changes during control by the current source driver. A voltage source driver is configured to output a predeterminable voltage as an output signal. Depending on the charge state of the gate-source capacitance of the controlled first switching element, a resulting gate current flowing into the gate changes during control by the voltage source driver.Preferably, a controllable gate driver is configured to specify a plurality of different selectable or presettable voltage or current values, preferably voltage or current values ​​of any desired magnitude. Preferably, a controllable gate driver is programmable and can specify the presettable voltage or current values ​​for presettable periods of time or time segments, or can specify voltage or current profiles or voltage or current curves at presettable times.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. 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 constant and selected to be small enough to easily enable observation of the switching behavior, preferably observation, recording, determination or measurement of the curve of the gate-source voltage, the drain-source current and / or the drain-source voltage. The slower the first switching element is switched on or off, the less disrupted the said voltages and currents are. In this way, more precise measured values ​​of the said voltages and currents can be recorded, which in turn reflect the physical parameters of the first switching element.The terms chosen to designate the voltages and currents, e.g., gate-source voltage or drain-source voltage, refer to the voltages or currents that can be measured between the gate, source, and drain terminals of a switching element. Preferably, the terms base, emitter, and collector, which correspond to a corresponding bipolar transistor, are synonymous within the scope of this description when describing one of the terms gate, source, or drain. Various options for determining or measuring these voltages and currents are known to those skilled in the art. The terms used in connection with determining the voltages and currents explicitly also include measurements at other points in a power electronics system or circuit that are suitable for characterizing the aforementioned voltages and / or currents.The predefinable first identification time is selected to be long enough to ensure that the first switching element is switched on or off completely, depending on the magnitude of the identification current. This allows the entire switching process to be observed. As a further step, the voltage values ​​of the curve 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 between the gate and source terminals of the first switching element during the first identification time due to the application of the first identification current. In a subsequent step, a first parameter of the first switching element is determined depending on the determined voltage values ​​of the curve of the first identification gate voltage, preferably on the basis of the magnitude of the voltage values ​​and the curve, in particular the gradient of the first identification gate voltage.Preferably, the determination or ascertainment of a first parameter of the first switching element takes place before commissioning of a power converter, 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 during a vehicle visit to a workshop.

[0013] Advantageously, a method is provided which enables a reliable determination of a specific parameter of a specific switching element.

[0014] In one embodiment, a further method step comprises applying a first control current for a predeterminable first control time, depending on the determined first parameter, to the gate of the first switching element for operating the first switching element. Preferably, a predeterminable constant first identification current is applied to the gate of the first switching element for a predeterminable first identification time, and a first control current is applied for a predeterminable first control time, depending on the determined first parameter, to the gate of the first switching element for operating the first switching element by means of the same current source driver. Preferably, the first switching element is operated while a vehicle is driving.Preferably, operating the first switching element comprises switching the first switching element on or off, preferably operating the first switching element in an electronic device, for example in a power converter, a DC-DC converter, or an inverter for the preferably continuous provision of a converted current or a converted voltage. A power 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. When operating or during the operation of the first switching element, resulting switching losses should preferably be avoided as far as possible, so that the fastest possible switching is aimed for.Therefore, the first control current to be applied is preferably as large as possible, and the predeterminable first control time is as short as possible. The first control current to be applied and / or the predeterminable first control time are specified depending on the determined first parameter.

[0015] Advantageously, a method is provided for operating a first switching element as a function of a determined first parameter.

[0016] In one embodiment, the first identification time is longer than the predeterminable activation time for operating the first switching element by a factor of 10 to 10,000, preferably 100 to 1,000, preferably 400. As already mentioned above, the first identification time is longer so that the identification gate voltage is less affected by interference, whereas the activation time is shorter so that switching losses are as low as possible during operation.

[0017] Advantageously, an improved method is provided.

[0018] In one embodiment, while a predeterminable constant first identification current is applied to the gate of the first switching element for the first identification time, a predeterminable voltage is applied between the drain and source of the switching element, and no load current flows between the drain and source of the switching element. A connected load would lead to superpositions and interference during the determination of the voltage values ​​of the curve of the resulting first identification gate voltage over the first identification time and would falsify the determined voltage values. Therefore, a load current through the switching element is prevented or minimized during the determination of the first parameter of the first switching element. The voltage is preferably applied across the drain and source of the first switching element.

[0019] Advantageously, an improved method is provided.

[0020] In one embodiment, the first identification current is approximately 0.1 to 0.001 times smaller than the first drive current for operating the first switching element. As already mentioned above, the first identification current is smaller so that the identification gate voltage is less affected by interference, whereas the drive current is larger so that the switching process occurs more quickly during operation and switching losses are as low as possible.

[0021] Advantageously, an improved method is provided.

[0022] In one embodiment, 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 curve of the resulting first identification gate voltage at which the gradient of the first identification gate voltage reaches a first minimum over the first identification time. Preferably, the first threshold voltage of the first switching element is determined as the first parameter as a function of the first identification threshold voltage, preferably by multiplying the first identification threshold voltage by a first factor.

[0023] Consequently, the voltage values ​​of the curve of the resulting first identification gate voltage over the first identification time are first determined. Subsequently, the gradients of the curve of the resulting first identification voltage over the first identification time are determined. In a further step, the voltage value of the curve of the resulting first identification gate voltage at which a gradient of the first identification gate voltage over the first identification time reaches a first minimum is determined. This voltage value is determined as the identification threshold voltage. Preferably, the determined identification threshold voltage can be determined as a threshold voltage, as it results during operation of the switching element, by multiplying it by a first predeterminable factor as a first parameter.As the first factor, a specific value is preferably used which is determined from a parameterization or a preliminary diagnosis of a reference switching element and is stored in a retrievable manner, preferably in a characteristic map.

[0024] Advantageously, a method is provided for determining a first parameter, the identification threshold voltage or the threshold voltage. In one embodiment, 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 a function of the first identification plateau voltage, in particular by multiplying the first identification plateau voltage by a second factor.

[0025] Consequently, the voltage values ​​of the curve of the resulting first identification gate voltage over the first identification time are first determined. In a further step, the voltage value of the curve of the resulting first identification gate voltage at which a voltage value of the first identification gate voltage reaches a first maximum over the first identification time is determined. This voltage value is determined as the identification plateau voltage. The determined identification plateau voltage can preferably be determined as a plateau voltage, as it results during operation of the switching element, by multiplying it by a second predeterminable factor as a first parameter. The second factor is preferably a specific value that is determined from a parameterization or a preliminary diagnosis of a reference switching element and is stored retrievably, preferably in a characteristic map.

[0026] Advantageously, a method is provided for determining a first parameter, the identification plateau voltage or the plateau voltage.

[0027] In one embodiment, the parameter to be determined is a first transconductance. Preferably, the identification threshold voltage and / or the first identification plateau voltage, or preferably the difference between the identification plateau voltage and the identification threshold voltage, are taken into account for determining the transconductance and determined as a function of these. These values ​​are stored, preferably in a characteristic map, retrievably for further operation and control of the switching elements. Furthermore, the invention relates to a device for determining a first parameter of a first switching element, having a control device configured to carry out a method described above. The control device preferably comprises a computer unit or a PC, or a processor.Preferably, the control device is configured to control the current source driver and a voltage measuring device such that the described method steps are performed. Advantageously, a device for implementing the method is provided. The device preferably comprises a gate driver with the control device, the current source driver, and / or the voltage measuring device. The gate driver is preferably configured as an ASIC, i.e., as an application-specific integrated circuit configured to perform at least one or all of the method steps.

[0028] The invention further relates to a drive train with a described device. The drive train is preferably designed for the operation of an electrified vehicle or serves, for example, to drive an electric vehicle. The drive train preferably comprises the device, which is preferably arranged within a power 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. The method, the device, and the drive train enable more sustainable operation of the drive train.

[0029] The invention further relates to a vehicle having a described drive train. Advantageously, a vehicle is thus provided that includes a device with which a parameter of a first switching element can be determined.

[0030] The invention further relates to a computer program comprising instructions that cause the device to execute the method steps. The invention further relates to a computer-readable medium comprising instructions that, when executed by a device, cause the device to execute the method steps of the method.

[0031] It is understood that the features, properties and advantages of the method according to the invention apply or are applicable accordingly to the device or the drive train and the vehicle and vice versa.

[0032] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

[0033] Short description of the drawing

[0034] In the following, the invention will be explained in more detail with reference to some figures, which show:

[0035] Figure 1 is a schematic representation of a current source driver with a first and a second connected switching element.

[0036] Figure 2 is a schematic representation of an equivalent circuit diagram for a switching element

[0037] Figure 3 shows a schematically illustrated profile of a first identification current and a simulation of a first identification gate voltage

[0038] Figure 4

[0039] A schematic representation of currents and voltages during a switching operation of a switching element

[0040] Figure 5

[0041] A schematically illustrated course of currents and voltages during a switching-off process of a switching element. Figure 6 shows a schematically illustrated flow diagram for a method for determining a first parameter of a first switching element.

[0042] Figure 7 shows a schematic representation of a vehicle with a drive train,

[0043] Embodiments of the invention

[0044] Figure 1 shows a schematic representation of a current source driver 210, 310 with a first switching element 250 and a second switching element 350. Preferably, the gate 252 of the first switching element is connected to the current source driver 210, 310, preferably via a first output. Preferably, the gate 352 of the second switching element is connected to the current source driver 210, 310, preferably via a second output. Preferably, the current source driver 210, 310 comprises further outputs, which can be connected to a third or fourth switching element 270 or 280. Preferably, a current source driver is configured to control a first and a second switching element independently by means of two differently programmable outputs. Alternatively, individual current source drivers 210, 310, i.e. preferably a first current source driver 210 and a second current source driver 310, can each be connected to a single one of the, for example,four switching elements 250, 350, 270, 280 are connected. Preferably, the first and second switching elements 250, 350 are connected in parallel. Preferably, the third and fourth switching elements 270, 280 are connected in parallel. The four switching elements are arranged in Figure 1, for example, as a half-bridge, which is supplied with energy via a supply voltage source 260. The output of the half-bridge is preferably a center tap of the half-bridge 265, at which the positive or negative potential of the supply voltage source 265 is provided depending on the switch position of the four switching elements. Figure 2 shows a schematic representation of an equivalent circuit diagram for a switching element. On the top left-hand side of Figure 2, a circuit symbol for a field-effect transistor, e.g. a SiC MOSFET, with the terminals S (source), D (drain) and G (gate) is shown. Analogously, below this, a circuit symbol for another transistor, e.g.An IGBT, shown with terminals C (collector), E (emitter), and B (base). Both switching elements have in common that a current flow between drain and source or collector and emitter is controlled via the gate or base control terminal. An equivalent circuit diagram for the field-effect transistor is shown on the right side of the figure as an example, illustrating the transistor's parasitic properties. Preferably, a gate-source capacitance Cx_GS, a gate-drain capacitance Cx_GD, and a drain-source capacitance Cx_Ds are shown, which represent examples of parasitic properties between the terminals of a switching element.

[0045] Figure 3 shows a schematically illustrated profile of an identification current and an identification gate voltage. The lower case "x" in the reference numerals stands as a placeholder for a "1" or "2" to indicate that their values ​​can differ depending on whether they refer to a first or second switching element. The upper area of ​​Figure 3 shows a profile of a predeterminable constant identification current Ixjd, as it is applied to a gate 252, 352 of a switching element 250, 350 for a predeterminable identification time tx_id to determine a parameter P1, P2 of a switching element 250, 350. The area below schematically shows a resulting identification gate voltage UGxJd over the identification time txjd, based on the voltage values ​​of which a parameter P1, P2 of a switching element 250, 350 is determined. Preferably, the identification time txjd is approximately between 50 and 300 ps, ​​preferably between 90 and 150 ps, ​​preferably 120 ps.The 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 UGxJd. 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 UGxJd. The duration of the identification precharging tx_id_pre results from the period between the start of the identification time txjd and the time at which the identification threshold voltage Vx_th_id is reached. The duration of the identification commutation tx_id_com results from the period between the time at which the identification threshold voltage Vx_th_id is reached and the time at which the identification plateau voltage Vx_pl_id is reached.The duration of the identification reload tx_id_post is the period between the time the identification plateau voltage Vx_pl_id is reached and the end of the identification time txjd.

[0046] Figure 4 shows a schematically illustrated curve of currents and voltages during a switch-on process of a switching element, i.e. the curve of the currents and voltages during switch-on. As shown in the top graph of Figure 4, in order to operate and switch on a switching element 250, 260, a control current lx_c is applied to the gate 252, 352 of a switching element 250, 350 for a predeterminable first control time tx_c as a function of the determined parameter P1, P2. Depending on the switching element used or the technology of the switching element used, the control 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 Figure 4 shows the resulting gate voltage Vx_gs, which preferably increases during turn-on. The turn-on process preferably comprises the following successive time segments: precharging tx_on_pre, current commutation tx_on_cuco, voltage commutation tx_on_voco, and / or postcharging tx_on_post. During precharging, a preferably positive drive current lx_c is applied to the gate, the maximum drain-source voltage Vx_ds (second graph from the top in Figure 4) is applied to the switching element, no drain-source current lx_d (third graph from the top in Figure 4) flows yet, and the gate voltage Vx_gs increases. During current commutation, a preferably positive drive current is still applied to the gate, the maximum drain-source voltage is still present at the switching element, the drain-source current develops and increases to its maximum and the gate voltage continues to increase.During voltage commutation, a preferably positive drive current continues to be 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 continues to be applied to the gate, the drain-source voltage retains its minimum value, the drain-source current remains at its maximum, and the gate voltage continues to rise. The preferably positive drive current is preferably constant at a current value in the individual time segments, or it varies depending on the time segment and is specified as a function of the determined parameters P1, P2 for each time segment, preferably with different values ​​(shown as dotted lines in Figure 4). Alternatively, the drive current for each time segment can also be specified as a curve if required.

[0047] Figure 5 shows a schematically illustrated curve of currents and voltages during a switch-off process of a switching element, i.e. the curve of the currents and voltages during switch-off. As shown in the top graph of Figure 5, in order to operate and switch off a switching element 250, 260, a control current lx_c is applied to the gate 252, 352 of a switching element 250, 350 for a predeterminable first control time tx_off_c as a function of the determined parameter P1, P2. Preferably, the magnitude of the duration of the first control time tx_off_c corresponds to that of the first control time tx_c. Depending on the switching element used or the technology of the switching element used, the control 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 Figure 5 shows the resulting gate voltage Vx_gs, which preferably decreases during turn-off. The turn-off process preferably comprises the following successive time segments: pre-discharge tx_off_pre, voltage commutation tx_off_voco, current commutation tx_off_cuco, and / or post-discharge tx_off_post. During pre-discharge, a preferably negative drive current lx_c is applied to the gate, the minimum drain-source voltage Vx_ds (second graph from the top of Figure 5) is applied to the switching element, the maximum drain-source current lx_d flows (third graph from the top of Figure 5), and the gate voltage Vx_gs decreases.During voltage commutation, a preferably negative drive current continues to be 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 current commutation, a preferably negative drive current continues to be applied to the gate, the maximum drain-source voltage continues to be applied to the switching element, the drain-source current decreases and decreases to its minimum, and the gate voltage continues to drop. During post-discharge, a preferably negative drive current continues to be applied to the gate, the drain-source voltage retains its maximum value, the drain-source current remains at its minimum, and the gate voltage continues to drop.Preferably, the drive current, preferably negative, is constant at a current value in the individual time segments, or it varies depending on the time segment and is specified, preferably with different values, depending on the determined parameters P1, P2 for each time segment (shown in dotted lines in Figure 5). Alternatively, the drive current can also be specified as a curve for each time segment, if required.

[0048] Figure 6 shows a schematically illustrated flow diagram for a method for determining a parameter of a switching element. Method 100 begins with step 105. In step 110, a predeterminable constant first identification current 11 Jd is applied to the gate 252 of the first switching element 250 for a predeterminable first identification time t1_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 P1 is determined as a function of the determined voltage values ​​of the profile of the resulting first identification gate voltage UG1_id. Preferably, further in step 130, a predeterminable constant second identification current 12_id is applied to the gate 352 of the second switching element 350 for a predeterminable second identification time t2_id.Preferably, in step 140, voltage values ​​of the curve of the resulting second identification gate voltage UG2_id over the second identification time t2_id are determined. Preferably, in step 150, the second parameter P2 is determined as a function of the determined voltage values ​​of the curve of the resulting second identification gate voltage UG2_id. Preferably, in step 160, to operate the first switching element 250, a first drive current 11_c is applied to the gate 252 of the first switching element for a predeterminable first drive time t1_c as a function of the determined first parameter P1. Preferably, in step 170, to operate the second switching element 350, a second drive current 12_c is applied to the gate 352 of the second switching element as a function of the determined first and second parameters P1, P2. The method ends with step 175.

[0049] Figure 7 shows a schematically illustrated vehicle 400 with a drive train 300. The illustration shows, by way of example, a vehicle with four wheels 402, wherein the invention can be used equally in any vehicle with any number of wheels on land, on water, 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 electrical energy from the traction battery 305 to supply an electric machine 315 and / or the electric machine 315 to drive the vehicle 400. The inverter 310 preferably comprises a device 320. The device 320 serves to determine a parameter Px of a switching element 250, 350 and comprises a control device 325 that is configured to carry out a described method.

Claims

CLAIMS 1. 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 (11 _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), 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 Jd).

2. Method according to claim 1, further comprising the step of: Applying (160) a first drive current (11_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).

3. The method according to claim 2, wherein the first identification time (t1 _id) is longer by a factor of 10 to 10000 than the predeterminable control time (t1 _c) for operating the first switching element (250).

4. Method according to one of the preceding claims, wherein during the application (110) of the predeterminable constant first identification current (11 Jd) to the gate (252) of the first switching element (250) for the first identification time (t1 Jd), a predeterminable voltage is applied between the drain and source of the switching element (250) and no load current flows between the drain and source of the switching element (250).

5. The method according to any one of claims 2 to 4, wherein the first identification current (11 Jd) is smaller by approximately a factor of 0.1 to 0.001 than the first drive current (11 _c) for operating the first switching element (250).

6. The 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 curve 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 threshold voltage (V1 _th) of the first switching element (250) is determined as a function of the first identification threshold voltage (V1 _th_id), in particular by multiplying the first identification threshold voltage (V1 _th_id) by a first factor.

7. The method according to any 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 parameter (P1) is the first plateau voltage (V1 _pl) of the first switching element (250) as a function of the first identification plateau voltage (V1 _pl_id), in particular by multiplying the first identification plateau voltage (V1 _pl_id) by a second factor.

8. Device (320) for determining a first parameter (P1) of a first switching element (250), with a control device (325) which is configured to carry out a method (100) according to one of the preceding claims 1 to 7.

9. Drive train (300) with a device (320) according to claim 8.

10. Vehicle (400) having a drive train (300) according to claim 9.

11. A computer program comprising instructions that cause the device according to claim 8 to perform the method steps according to any one of claims 1 to 7.

12. A computer-readable medium comprising instructions that, when executed by a device according to claim 8, cause it to perform the method steps according to any one of claims 1 to 7.

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