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 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. 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 method for a second switching element for determining a second parameter of the second switching element is carried out using a controllable current source driver. The method comprises the further steps:applying a predeterminable constant second identification current to the gate of the second switching element for a predeterminable second identification time,determining the voltage values of the course of the resulting second identification gate voltage over the identification time,determining the second parameter as a function of the determined voltage values of the profile of the resulting second identification gate voltage, applying a second drive current as a function of the determined first and second parameter to the gate of the second switching element for operating the second switching element.Analogously to the above, a method for determining or ascertaining a second parameter, preferably a second electrical or physical parameter, of a second switching element having a controllable current source driver is consequently provided. A second parameter is, for example, preferably a voltage threshold value of a gate voltage at which the second 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 second switching element. Another exemplary parameter is the size of the gate-source capacitance. When the gate-source capacitance of the second 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 second 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 second 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 second switching element to drive the second 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 second 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 second 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 second identification current to the gate of the second switching element for a predefinable second identification time. Preferably, the height of the second identification current corresponds to the height of the first identification current. The duration of the second identification time preferably corresponds to the duration of the first identification time. A second identification current is applied to the gate or the gate terminal of the second 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, becomes readily possible. The predefinable second identification time is selected to be so great that switching on or switching off of the second 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 profile of the resulting second identification gate voltage over the second identification time are determined. The second identification gate voltage is the gate-source voltage that results during the second identification time between the gate and source terminals of the second switching element due to the application of the second identification current. Depending on the ascertained voltage values of the profile of the second identification gate voltage, preferably from the magnitude of the voltage values and the profile, in particular the gradient of the second identification gate voltage, a second parameter of the second switching element is ascertained in a following step. The determination or determination of the second parameter of the second switching element is preferably carried out before a power converter, which is preferably provided for a vehicle, is put into operation, 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. The operation of the second switching element preferably comprises switching on or switching off the second switching element, preferably the operation of the second 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 power converter is preferably designed as a DC-DC converter or as an inverter. The second drive current to be applied for this purpose and the predefinable second drive time differ by orders of magnitude from the second identification current and the second identification time. During operation or during operation of the second 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 second activation current to be applied is preferably as large as possible and the predefinable second activation time is as short as possible. The second drive current to be applied and the predefinable second drive time are predefined as a function of the ascertained first and second parameters. Since the second drive current is predefined at least as a function of a first parameter of the first switching element and a second parameter of the second switching element, an adaptation of the switching behavior of the second switching element to the switching behavior of the first switching element is made possible and therefore a greater load on one of the two switching elements is minimized during parallel operation of the two switching elements. Preferably, a predefinable constant second identification current is applied to the gate of the second switching element for a predefinable second identification time, and a second control current is applied to the gate of the second switching element as a function of the ascertained first parameter and second parameter for operating the second switching element by means of the same current source driver. The operation of the second shift element is preferably carried out during a driving operation of a vehicle.Advantageously, a method is provided which enables a reliable determination of a specific second parameter of a specific second switching element and a method is provided for operating the first and a second switching element as a function of the determined first and second parameters.In one configuration, for operating the first switching element, the first drive current is constant over different time segments of switching on or switching off the first switching element or varies over the time segments of switching on or switching off the first switching element. Preferably, the first drive current is in each case constant with a predefinable value as a function of the ascertained first parameter during the individual time segments of the switching on or switching off of the first switching element. For operating the second switching element, the second drive current is preferably constant over the different time segments of switching on or switching off the second switching element or varies over the time segments of switching on or switching off the second switching element. Preferably, the second drive current is constant with a predefinable value in each case during the individual time segments of the switching on or switching off of the second switching element as a function of the ascertained first and second parameter.Preferably, the operation of the switching element and thus the switching on or the switching off of the first and or the second switching element comprises time segments following one another. The method is configured to preset the control current per time segment, preferably preset a different level for each time segment, or preset a predeterminable curve profile, for the control current. The values or the height of the predefinable first drive current are predefined as a function of the respective time segment and the first parameter, and the values or the height of the predefinable second drive current are predefined as a function of the respective time segment and the first parameter and the second parameter.Advantageously, a method is provided that enables an improved adaptation of the switching behavior of the second switching element to the switching behavior of the first switching element.In one configuration, the individual time segments comprise the precharging, the current commutation, the voltage commutation and or the recharging when switching on. Preferably, the individual time segments comprise the pre-discharge, the voltage commutation, the current commutation and or the post-discharge during the switching off.During operation of a switching element during switching on, the time segment of the precharging preferably comprises a first portion of a drive time at which a preferably positive drive current is predefined and consequently an increase in the gate voltage results. The time segment of the precharging comprises the at least partial charging of the gate-source capacitance of the switching element and ends with the beginning of a current flow between drain and source of the switching element. During operation of a switching element during switching on, the time segment of the current commutation preferably comprises a second portion of a drive time, in which a preferably positive drive current is predefined and the gate voltage rises in parallel with an increase in the current flow between drain and source. The time segment of current commutation ends when the current flow between drain and source has reached its maximum and the decrease in the voltage between drain and source begins. During operation of a switching element during switching on, the time segment of the voltage commutation preferably comprises a third portion of a drive time, in which a preferably positive drive current is predefined, the gate voltage remains virtually constant and the voltage between drain and source decreases. The time segment of the voltage commutation ends when the voltage between drain and source has reached its minimum and a renewed rise of the gate voltage begins. During operation of a switching element during switching on, the time segment of recharging preferably comprises a fourth portion of a drive time, in which a preferably positive drive current is predefined, the gate voltage continues to rise, the voltage between drain and source remains minimal, and the current flow between drain and source remains maximal. The time segment of recharging ends when the, preferably positive, drive current has been reduced to such an extent that it reaches its minimum, preferably as before the start of the switching-on.During operation of a switching element during switching off, the time segment of the pre-discharge preferably comprises a first portion of a drive time at which a preferably negative drive current is predefined and consequently a decrease in the gate voltage results. The pre-discharge time segment comprises the at least partial discharge of the gate-source capacitance of the switching element and ends with the beginning of a rise in the voltage between drain and source of the switching element. During operation of a switching element during switching off, the time segment of the voltage commutation preferably comprises a second portion of a drive time, in which a preferably negative drive current is predefined, the gate voltage remains virtually constant and the voltage between drain and source increases. The time segment of the voltage commutation ends when the voltage between drain and source has reached its maximum and a renewed decrease of the gate voltage begins. During operation of a switching element during switching off, the time segment of the current commutation preferably comprises a third portion of a drive time, in which a preferably negative drive current is predefined and a decrease in the gate voltage takes place in parallel with a decrease in the current flow between drain and source. The time segment of the current commutation ends when the current flow between drain and source has reached its minimum, wherein the voltage between drain and source is still at a maximum. During operation of a switching element during switching off, the time segment of the after-discharge preferably comprises a fourth portion of a drive time, in which a preferably negative drive current is predefined, the gate voltage decreases further, the voltage between drain and source remains at a maximum and the current flow between drain and source remains at a minimum. The time segment of the post-discharge preferably ends when the gate voltage has reached its minimum or when the, preferably negative, amount of the drive current has been reduced to such an extent that it reaches its minimum, preferably as before the start of the switching-on.In one embodiment, a first, a second and a third gradient are determined as a function of the profile of the resulting first identification gate voltage for simplified simulation of the resulting first identification gate voltage, preferably when the switching element is switched on, preferably iteratively or with a regression. Preferably, the duration of the first identification precharge is determined as the time in which the replica has the first gradient, the duration of the first identification commutation is determined as the time in which the replica has the second gradient, and the duration of the first identification precharge is determined as the time in which the replica has the third gradient.Depending on the ascertained voltage values of the curve of the resulting first identification gate voltage over the first identification time, a simplified simulation of the resulting first identification gate voltage is ascertained. For this purpose, a first, a second and a third gradient are determined, preferably iteratively or with a regression, which, in a row in time segments following one another, map or simulate in a simplified manner the determined first identification gate voltage over the first identification time. Preferably, the duration of the first identification precharge is determined by means of this simulation as the time during which the simulation has the first gradient. Preferably, the duration of the first identification commutation is determined by means of this simulation as the time during which the simulation has the second gradient. Preferably, by means of this simulation, the duration of the first identification recharging is determined as the time during which the simulation has the third gradient. Alternatively, in an analogous manner, during an activation process, a simplified simulation of a resulting first identification gate voltage can be determined during an activation process as a function of ascertained voltage values of the curve of a resulting first identification gate voltage over a first identification time.Advantageously, a method is provided for determining the duration of successive time segments when a switching element is switched on.In one configuration, the first parameter to be determined is a first gate-source capacitance of the first switching element. The first gate-source capacitance is determined as the quotient of the applied predefinable constant first identification current and the first gradient.Advantageously, a method for determining the specific gate-source capacitance of a specific switching element is provided.In one configuration, the first parameter to be determined is a first switch-on capacitance of the first switching element. The first switch-on capacitance is determined as the quotient of the applied predefinable constant first identification current and the third gradient.Advantageously, a method for determining the specific switch-on capacitance of a specific switching element is provided.In one configuration, the first parameter to be determined is the first identification threshold voltage of the first switching element. The first identification threshold voltage is determined as the voltage value of the replica at which the first slope with the first gradient transitions into the second slope with the second gradient. The first identification threshold voltage is preferably determined as the voltage value of the replica of the first identification gate voltage at which the straight line having the first gradient or the first gradient ends and merges into the straight line having the second gradient or the second gradient.Advantageously, a method for determining the specific identification threshold voltage of a specific switching element is provided.In one configuration, the first parameter to be determined is a first gate-source charge of the first switching element. The first gate-source charge is determined as the product of the applied predefinable constant first identification current and the duration of the first identification precharge.Advantageously, a method for determining the specific gate-source charge of a specific switching element is provided.In one configuration, the first parameter to be determined is a first gate-drain charge of the first switching element. The first gate-drain charge is determined as the product of the applied predefinable constant first identification current and the duration of the first identification commutation.Advantageously, a method for determining the specific gate-drain charge of a specific switching element is provided.In one configuration, the first parameter to be determined is a first total gate charge of the first switching element. The first total gate charge is determined as the product of the applied predefinable constant first identification current and the duration of the sum of the first identification precharge, the first identification commutation and the first identification recharging.Advantageously, a method for determining the specific total gate charge of a specific switching element is provided.In one configuration, the second drive current for operating the second switching element is determined as a function of a product of the first drive current and a correction factor.Advantageously, a method for determining the second drive current for operating two parallel-connected switching elements, a first and a second switching element, is provided. The first and the second switching element can be arranged either in separate power converters, within a power converter or within a power module.In one embodiment, the correction factor is determined as a pre-charge correction factor, preferably for switching on, as the quotient of the duration of a second identification pre-charge to the duration of the first identification pre-charge. The duration of the second identification precharge of the second switching element is preferably ascertained in accordance with the ascertainment of the duration of the first identification precharge for the first switching element.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one configuration, the correction factor is determined as an improved precharge correction factor, preferably for switching on, as the quotient of a divisor to a divisor, wherein the divisor is determined as the sum of the duration of the second identification precharge and the quotient of the difference of the second threshold voltage and the second identification threshold voltage with respect to the first gradient of the second switching element, and wherein the divisor is determined as the sum of the duration of the first identification precharge and the quotient of the difference of the first threshold voltage and the first identification threshold voltage with respect to the first gradient of the first switching element.In switching elements of comparable technology, the difference between the first threshold voltage and the first identification threshold voltage preferably corresponds to the difference between the second threshold voltage and the second identification threshold voltage. This means that the difference between the threshold voltage and the identification threshold voltage is preferably determined on the basis of investigations on types of semiconductor switches or switching elements used, and this is preferably not carried out for each individual switching element. To determine this correction factor, a value, preferably a specific value in each case, is preferably used for the first and the second threshold value voltage, which value is determined from a condition or a preliminary diagnosis of a reference switching element and is stored in a retrievable manner, preferably in a characteristic diagram. Here, too, the second parameters of the second shift element are preferably determined in accordance with the determination of the corresponding first parameters for the first shift element.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one configuration, the correction factor is determined as a current commutation correction factor, preferably for switching on, as the quotient of the second gate-source capacitance to the first gate-source capacitance. The second gate-source capacitance of the second switching element is preferably determined in accordance with the determination of the first gate-source capacitance for the first switching element.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one embodiment, the correction factor is determined as a complete current commutation correction factor, preferably for switching on, as a product of the quotient of the second gate-source capacitance to the first gate-source capacitance and the quotient of a first transconductance to a second transconductance. Here, too, the second parameter of the second shift element is preferably determined in accordance with the determination of the corresponding first parameter for the first shift element. For ascertaining this correction factor, a value, preferably a specific value in each case, is used for the first and the second transconductance, which value is determined via correlations from a condition or preliminary diagnoses, preferably during development. Alternatively, the threshold voltage and or the plateau voltage or identification threshold voltage is used as an indicator for determining the transconductance. These values are stored in a retrievable manner, preferably in a characteristic diagram.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one configuration, the correction factor is determined as a sum as a supplemented current commutation correction factor, preferably for switching on, wherein the first summand is the product of a gate-source parameter and a current commutation correction factor and the second summand is the product of a gate-drain parameter and the quotient of the second gate-drain charge to the first gate-drain charge. The gate-source parameter and the gate-drain parameter result from the structure of the power electronics and are virtually identical for parallel-connected semiconductor switches. Preferably, the sum of the gate-source parameter and the gate-drain parameter is equal to one. The gate-source parameter and the gate-drain parameter preferably map the portions of the effects of the current commutation and of the parasitic effects. The ratio preferably depends on the switching speed of the switching elements and the commutation inductance. The greater the product of switching speed and commutation inductance, the greater the gate-drain parameter. The quotient of the second gate-drain charge to the first gate-drain charge preferably maps the difference in the gate-drain capacitance, which is additionally charged due to the parasitic voltage drop and thus subtracts the charge of the gate-source capacitance and thus preferably leads to a slowed current commutation. Here, too, the second parameter of the second shift element is preferably determined in accordance with the determination of the corresponding first parameter for the first shift element.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one configuration, the correction factor is determined as a voltage commutation correction factor, preferably for switching on, as the quotient of the second gate-drain capacitance to the first gate-drain capacitance, or the correction factor is determined as a voltage commutation correction factor, preferably for switching on, as the quotient of the second gate-drain charge to the first gate-drain charge. Here, too, the second parameter of the second shift element is preferably determined in accordance with the determination of the corresponding first parameter for the first shift element.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one embodiment, the correction factor is determined as a pre-discharge correction factor, preferably for the switching off, as the quotient of the duration of the second identification recharging to the duration of the first identification recharging. Here, too, the second parameter of the second shift element is preferably determined in accordance with the determination of the corresponding first parameter for the first shift element.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one configuration, the correction factor is determined as an improved pre-discharge correction factor, preferably for the switching off, as the quotient of a dividend to a divisor, wherein the divisor is determined as the sum of the duration of the second identification recharging and the quotient of the difference of the second threshold voltage and the second identification threshold voltage to the third gradient of the second switching element, and wherein divisor is determined as the sum of the duration of the first identification recharging and the quotient of the difference of the first threshold voltage and the second identification threshold voltage to the third gradient of the first switching element. Here, too, the second parameter of the second shift element is preferably determined in accordance with the determination of the corresponding first parameter for the first shift element.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one configuration, the correction factor is determined as a voltage commutation correction factor, preferably for the switching off, as the quotient of the second gate-drain capacitance to the first gate-drain capacitance, or the correction factor is determined as a voltage commutation correction factor, preferably for the switching off, as the quotient of the second gate-drain charge to the first gate-drain charge. Here, too, the second parameter of the second shift element is preferably determined in accordance with the determination of the corresponding first parameter for the first shift element.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one configuration, the correction factor is determined as a current commutation correction factor, preferably for the switching-off, as the quotient of the second gate-source capacitance to the first gate-source capacitance. Here, too, the second parameter of the second shift element is preferably determined in accordance with the determination of the corresponding first parameter for the first shift element.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one embodiment, the correction factor is determined as a complete current commutation correction factor, preferably for the switching off, as a product of the quotient of the second gate-source capacitance to the first gate-source capacitance and the quotient of the first transconductance to the second transconductance. Here, too, the second parameter of the second shift element is preferably determined in accordance with the determination of the corresponding first parameter for the first shift element. The transconductance is determined as described above during turn-on.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one embodiment, the correction factor is determined as a switch-on correction factor, preferably for switch-on, as a sum of the precharge correction factor, the current commutation correction factor and the voltage commutation correction factor, wherein the individual factors are weighted before the summation by multiplication by a switch-on weighting factor in each case, wherein the sum of the switch-on weighting factors is equal to one and each switch-on weighting factor has a value between 0 and 1 inclusive.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.In one embodiment, the correction factor is determined as a switch-off correction factor, preferably for the switch-off, as a sum of the pre-discharge correction factor, the voltage commutation correction factor and the current commutation correction factor, wherein the individual factors are weighted before the summation by multiplication by a switch-off weighting factor in each case, wherein the sum of the switch-off weighting factors is equal to one and each switch-off weighting factor has a value between 0 and 1 inclusive.Advantageously, a method for ascertaining a correction factor for ascertaining the second drive current for operating the second switching element of two parallel-connected switching elements is provided.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, an equivalent circuit diagram is shown by way of example on the right-hand side of the figure, wherein the parasitic properties of the transistor are shown. 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 between 50 and 300 μs, preferably between 90 and 150 μs, preferably 120 μs. 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 UGx_id. Preferably, a first, a second and a third gradient m 1_x, m 2_x, m 3_x are determined for simplified simulation UGx_id_mod of the resulting identification gate voltage UGx_id. From this, the durations of the identification precharge tx_id_pre, the identification commutation tx_id_com and the identification reload tx_id_post are determined.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_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, as a function of the profile of the resulting first identification gate voltage (UG1_id), a first, a second and a third gradient (m1_1, m2_1, m3_1) for simplified simulation (UG1_id_mod) of the resulting first identification gate voltage (UG1_id), in particular iteratively or with a regression, are determined and, in particular, the duration of the first identification precharge (t1_id_pre) is determined as the time in which the simulation (UG1_id_mod) has the first gradient (m1_1), the duration of the first identification commutation (t1_id_com) is determined as the time in which the replica (UG1_id_mod) has the second gradient (m2_1) and the duration of the first identification recharge (t1_id_post) is determined as the time in which the replica (UG1_id_mod) has the third gradient (m3_1).Method according to Claim 4, wherein the first parameter (P1) to be determined is a first gate-source capacitance (C1_GS) of the first switching element (250), wherein the first gate-source capacitance (C1_GS) is determined as the quotient of the applied predefinable constant first identification current (I1_id) and the first gradient (m1_1).Method according to Claim 4, wherein the first parameter (P1) to be determined is a first switch-on capacitance (C1_ON) of the first switching element (250), wherein the first switch-on capacitance (C1_ON) is determined as the quotient of the applied predefinable constant first identification current (I1_id) and the third gradient (m3_1).Method according to Claim 4, wherein the first parameter (P1) to be determined is the 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 replica (UG1_id_mod) at which the first gradient with the first gradient (m1_1) transitions into the second gradient with the second gradient (m2_1).Method according to Claim 4, wherein the first parameter (P1) to be determined is a first gate-source charge (Q1_GS) of the first switching element (250), wherein the first gate-source charge (Q1_GS) is determined as the product of the applied predefinable constant first identification current (I1_id) and the duration of the first identification precharge (t1_id_pre).Method according to Claim 4, wherein the first parameter (P1) to be determined is a first gate-drain charge (Q1_G) of the first switching element (250), wherein the first gate-drain charge (Q1_G) is determined as the product of the applied predefinable constant first identification current (I1_id) and the duration of the first identification commutation (t1_id_com).Method according to Claim 4, wherein the first parameter (P1) to be determined is a first total gate charge (Q1_Gtot) of the first switching element (250), wherein the first total gate charge (Q1_Gtot) is determined as the product of the applied predefinable constant first identification current (I1_id) and the duration of the first identification precharge (t1_id_pre), the first identification commutation (t1_id_com) and the first identification recharge (t1_id_post).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 10.Drive train (300) comprising a device (320) according to claim 11.Vehicle (400) comprising a drive train (300) according to claim 12.A computer program comprising instructions for causing the apparatus of claim 11 to perform the method steps of the method (100) of any one of claims 1 to 10.A computer readable medium comprising instructions which, when executed by an apparatus according to claim 11, cause the apparatus to perform the method steps of the method (100) according to any one of claims 1 to 10.

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