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 (l1_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

[0001] 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. State of the art

[0002] 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 the 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, thereby reducing the dispersion of the power losses of switching elements operated in parallel. Disclosure of the invention

[0003] 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: 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 curve 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 curve of the resulting first identification gate voltage.

[0004] 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 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 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 differently selectable or predeterminable voltage values ​​or current values, preferably voltage values ​​or current values ​​of any desired different levels. Preferably, a controllable gate driver is programmable and can specify the predeterminable voltage values ​​or current values ​​for predeterminable periods of time or time segments or can specify voltage value or current value profiles or voltage value or current value curves at predeterminable 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 chosen to be small enough to easily observe the switching behavior, preferably to observe, record, determine, or measure the gate-source voltage, drain-source current, and / or drain-source voltage. The slower the first switching element is switched on or off, the more smoothly these voltages and currents flow. This allows more precise measurements of these voltages and currents to be recorded, which in turn reflect the physical parameters of the first switching element. The terms chosen to describe 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 corresponding 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 sufficiently long that the first switching element is reliably switched on or off completely, depending on the magnitude of the identification current. This allows the entire switching process to be observed.In a further step, the voltage values ​​of the profile 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. Depending on the determined voltage values ​​of the profile of the first identification gate voltage, preferably on the level of the voltage values ​​and the profile, in particular the gradient of the first identification gate voltage, a first parameter of the first switching element is determined in a subsequent step.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.

[0005] Advantageously, a method is provided which enables a reliable determination of a specific parameter of a specific switching element.

[0006] In one embodiment, a further method step comprises applying a first drive current for a predeterminable first drive time as a function of 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 drive current is applied for a predeterminable first drive time as a function of 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 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.

[0007] Advantageously, a method is provided for operating a first switching element as a function of a determined first parameter.

[0008] In one embodiment, the first identification time is longer than the predeterminable drive 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 drive time is shorter so that switching losses are as low as possible during operation.

[0009] Advantageously, an improved method is provided.

[0010] 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.

[0011] Advantageously, an improved method is provided.

[0012] 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.

[0013] Advantageously, an improved method is provided.

[0014] In one embodiment, the first parameter to be determined is a first identification threshold voltage of the first switching element. 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 over the identification time is minimal.

[0015] 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 minimum is determined. This voltage value is determined as the first identification threshold voltage.

[0016] Advantageously, a method is provided for determining a first parameter, the identification threshold voltage.

[0017] In one embodiment, the duration of a first identification precharging is determined as the time from the start of the application of the predeterminable constant first identification current to the gate of the first switching element until the time at which the gradient of the first identification gate voltage over the first identification time is minimal.

[0018] 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 time period from the start of application of the predeterminable constant first identification current to the gate of the first switching element until the point in time at which a gradient of the first identification gate voltage over the first identification time reaches a minimum is determined. This time period is determined as the duration of a first identification precharge.

[0019] Advantageously, a method is provided for determining a first parameter, the duration of a first identification precharging. Advantageously, the duration of the first identification precharging is used, for example, to determine a first gate-source charge as the product of the applied, predeterminable constant first identification current and the duration of the first identification precharging of the first switching element.

[0020] 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 a function of the first identification threshold voltage, preferably by multiplying the first identification threshold voltage by a first factor.

[0021] 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 is determined at which a gradient of the first identification gate voltage over the first identification time reaches a first minimum. This voltage value is determined as 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 predefinable 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.

[0022] Advantageously, a method is provided for determining a first parameter, the identification threshold voltage or the threshold voltage.

[0023] 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.

[0024] 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.

[0025] Advantageously, a method is provided for determining a first parameter, the identification plateau voltage or the plateau voltage.

[0026] 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 thereof.

[0027] These values ​​are stored, preferably in a map, so that they can be retrieved for further operation and the control of the switching elements.

[0028] In one embodiment, the method for a second switching element for determining a second parameter of the second switching element is carried out with 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 resulting second identification gate voltage over the identification time, Determining the second parameter as a function of the determined voltage values ​​of the curve of the resulting second identification gate voltage, applying a second drive current as a function of the determined first and second parameters to the gate of the second switching element for operating the second switching element.

[0029] Analogous to the above, a method is therefore provided for determining or ascertaining a second parameter, preferably a second electrical or physical parameter, of a second switching element with a controllable current source driver. A second parameter is, for example, preferably a voltage threshold of a gate voltage at which the second switching element begins to conduct a current. Reaching this voltage thus influences the beginning or start time of the turn-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 the current is minimal. The duration of the charging thus influences the speed of turn-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 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, power 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 second switching element. The desired 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 as a function of the input signal to the gate of the second switching element in order to control the second 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 second 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 second 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 differently selectable or predeterminable voltage values ​​or current values, preferably voltage values ​​or current values ​​of any desired different levels. Preferably, a controllable gate driver is programmable and can specify the predeterminable voltage values ​​or current values ​​for predeterminable periods of time or time segments or can specify voltage value or current value profiles or voltage value or current value curves at predeterminable times. The method comprises the steps of: applying a predeterminable constant second identification current to the gate of the second switching element for a predeterminable second identification time. Preferably, the level of the second identification current corresponds to the level of the first identification current. Preferably, the duration of the second identification time corresponds to the duration of the first identification time.A second identification current is applied to the gate or gate terminal of the second 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 gate-source voltage profile. The predefinable second identification time is selected to be large enough to ensure that the second 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 next 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 between the gate and source terminals of the second switching element during the second identification time due to the application of the second identification current. Depending on the determined 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 determined in a subsequent step.The second parameter of the second switching element is preferably determined or ascertained 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. Preferably, operating the second switching element comprises switching the second switching element on or off, preferably operating the second 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 second control current to be applied for this purpose and the predeterminable second control time differ by orders of magnitude from the second identification current and the second identification time. During operation of the second switching element, resulting switching losses should preferably be avoided as far as possible, so that the fastest possible switching is desired. Therefore, the second control current to be applied is preferably as large as possible and the predeterminable second control time as short as possible. The second control current to be applied and / or the predeterminable second control time are specified as a function of the determined first and second parameters.Since the second drive current is specified at least as a function of a first parameter of the first switching element and a second parameter of the second switching element, adaptation of the switching behavior of the second switching element to the switching behavior of the first switching element is made possible, thus minimizing greater loading of one of the two switching elements when the two switching elements are operated in parallel. Preferably, a predeterminable, constant second identification current is applied to the gate of the second switching element for a predeterminable second identification time, and a second drive current is applied as a function of the determined first parameter and second parameter to the gate of the second switching element to operate the second switching element by means of the same current source driver. Preferably, the second switching element is operated while a vehicle is being driven.

[0030] 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.

[0031] In one embodiment, for operating the first switching element, the first drive current is constant over different time segments of switching on or off the first switching element or varies over the time segments of switching on or off the first switching element. Preferably, the first drive current is constant during the individual time segments of switching on or off the first switching element, with a predeterminable value depending on the determined first parameter. Preferably, for operating the second switching element, the second drive current is constant over the different time segments of switching on or off the second switching element or varies over the time segments of switching on or off the second switching element.Preferably, the second control current is constant during the individual time segments of switching on or off the second switching element, with a predeterminable value depending on the determined first and second parameters.

[0032] Preferably, the operation of the switching element and thus the switching on or off of the first and / or second switching element comprises successive time segments. The method is configured to specify the drive current for each time segment, preferably a different level or a predeterminable curve for the drive current for each time segment. The values ​​or level of the predeterminable first drive current are specified as a function of the respective time segment and the first parameter, and the values ​​or level of the predeterminable second drive current are specified as a function of the respective time segment and the first parameter and the second parameter.

[0033] Advantageously, a method is provided which enables an improved adaptation of the switching behavior of the second switching element to the switching behavior of the first switching element.

[0034] In one embodiment, the individual time segments during switching on comprise precharging, current commutation, voltage commutation, and / or recharging. Preferably, the individual time segments during switching off comprise predischarging, voltage commutation, current commutation, and / or redischarging.

[0035] During operation of a switching element during switch-on, the precharging time segment preferably comprises a first portion of a drive time during which a, preferably positive, drive current is specified, resulting in an increase in the gate voltage. The precharging time segment comprises the at least partial charging of the gate-source capacitance of the switching element and ends with the start of a current flow between the drain and source of the switching element. During operation of a switching element during switch-on, the current commutation time segment preferably comprises a second portion of a drive time during which a, preferably positive, drive current is specified, and an increase in the gate voltage occurs in parallel with an increase in the current flow between drain and source. The current commutation time segment 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 switch-on, the voltage commutation time segment preferably comprises a third portion of a drive time, during which a, preferably positive, drive current is specified, the gate voltage remains virtually constant, and the voltage between drain and source decreases. The voltage commutation time segment ends when the voltage between drain and source has reached its minimum and the gate voltage begins to rise again. During operation of a switching element during switch-on, the recharging time segment preferably comprises a fourth portion of a drive time, during which a, preferably positive, drive current is specified, the gate voltage continues to rise, the voltage between drain and source remains minimal, and the current flow between drain and source remains maximum.The recharging time segment 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 switching on.

[0036] During operation of a switching element during turn-off, the pre-discharge time segment preferably comprises a first portion of a drive time during which a, preferably negative, drive current is specified, resulting in a decrease in the gate voltage. The pre-discharge time segment comprises the at least partial discharging of the gate-source capacitance of the switching element and ends with the start of an increase in the voltage between drain and source of the switching element. During operation of a switching element during turn-off, the voltage commutation time segment preferably comprises a second portion of a drive time during which a, preferably negative, drive current is specified, the gate voltage remains almost constant, and the voltage between drain and source increases. The voltage commutation time segment ends when the voltage between drain and source has reached its maximum and a renewed decrease in the gate voltage begins.During operation of a switching element during turn-off, the time segment of current commutation preferably comprises a third portion of a drive time, during which a, preferably negative, drive current is specified and a decrease in the gate voltage occurs in parallel with a decrease 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 minimum, wherein the voltage between drain and source continues to be at a maximum. During operation of a switching element during turn-off, the time segment of post-discharge preferably comprises a fourth portion of a drive time, during which a, preferably negative, drive current is specified, the gate voltage continues to decrease, the voltage between drain and source remains at a maximum and the current flow between drain and source remains at a minimum.Preferably, the time segment of the post-discharge 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 switching on.

[0037] In one embodiment, a first, a second, and a third gradient are determined depending on 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 precharging is determined as the time during which the simulation has the first gradient, the duration of the first identification commutation is determined as the time during which the simulation has the second gradient, and / or the duration of the first identification recharging is determined as the time during which the simulation has the third gradient.

[0038] Depending on the determined 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 determined. For this purpose, a first, a second, and a third gradient are determined, preferably iteratively or using a regression, which, when arranged in successive time segments, simplify the determined first identification gate voltage over the first identification time. Preferably, the duration of the first identification precharging is determined using this simulation as the time during which the simulation has the first gradient. Preferably, the duration of the first identification commutation is determined using this simulation as the time during which the simulation has the second gradient.Preferably, this simulation is used to determine the duration of the first identification recharge as the time during which the simulation exhibits the third gradient. Alternatively, a simplified simulation of a resulting first identification gate voltage during a switch-off process can be determined analogously during a switch-off process as a function of determined voltage values ​​of the profile of a resulting first identification gate voltage over a first identification time.

[0039] Advantageously, a method is provided for determining the duration of successive time segments when a switching element is switched on.

[0040] In one embodiment, 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, predeterminable constant first identification current and the first gradient.

[0041] Advantageously, a method is provided for determining the specific gate-source capacitance of a specific switching element.

[0042] In one embodiment, the first parameter to be determined is a first turn-on capacitance of the first switching element. The first turn-on capacitance is determined as the quotient of the applied, predeterminable constant first identification current and the third gradient.

[0043] Advantageously, a method is provided for determining the specific switching capacity of a specific switching element.

[0044] In one embodiment, 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 simulation at which the first slope with the first gradient transitions into the second slope with the second gradient. Preferably, the first identification threshold voltage is determined as the voltage value of the simulation of the first identification gate voltage at which the straight line with the first slope or the first gradient ends and transitions into the straight line with the second slope or the second gradient.

[0045] Advantageously, a method is provided for determining the specific identification threshold voltage of a specific switching element.

[0046] In one embodiment, 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, predeterminable constant first identification current and the duration of the first identification precharging.

[0047] Advantageously, a method is provided for determining the specific gate-source charge of a specific switching element.

[0048] In one embodiment, 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, predeterminable, constant first identification current and the duration of the first identification commutation.

[0049] Advantageously, a method is provided for determining the specific gate-drain charge of a specific switching element.

[0050] In one embodiment, 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, predeterminable constant first identification current and the duration of the sum of the first identification precharging, the first identification commutation, and the first identification postcharging.

[0051] Advantageously, a method is provided for determining the specific total gate charge of a specific switching element.

[0052] In one embodiment, 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.

[0053] Advantageously, a method is provided for determining the second drive current for operating two parallel-connected switching elements, a first and a second switching element. The first and second switching elements can be arranged either in separate power converters, within a power converter, or within a power module.

[0054] In one embodiment, the correction factor is determined as a precharging correction factor, preferably for switching on, as the quotient of the duration of a second identification precharging to the duration of the first identification precharging. The duration of the second identification precharging of the second switching element is preferably determined in accordance with the determination of the duration of the first identification precharging for the first switching element.

[0055] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0056] In one embodiment, the correction factor is determined as an improved precharging correction factor, preferably for switching on, as a quotient of a dividend to a divisor, wherein the dividend is determined as the sum of the duration of the second identification precharging and the quotient of the difference between the second threshold voltage and the second identification threshold voltage 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 precharging and the quotient of the difference between the first threshold voltage and the first identification threshold voltage to the first gradient of the first switching element.

[0057] For switching elements with 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 based on studies of the types of semiconductor switches or switching elements used, and this is preferably not done 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 second threshold voltages. This value 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.Preferably, the second parameters of the second switching element are also determined in accordance with the determination of the corresponding first parameters for the first switching element.

[0058] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0059] In one embodiment, 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. Preferably, the second gate-source capacitance of the second switching element is determined in accordance with the determination of the first gate-source capacitance for the first switching element.

[0060] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0061] In one embodiment, the correction factor is determined as a complete current commutation correction factor, preferably for switching on, as the 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 switching element is preferably determined in accordance with the determination of the corresponding first parameter for the first switching element. To determine this correction factor, a value, preferably a specific value in each case, is used for the first and second transconductance, which value is determined via correlations from a parameterization or preliminary diagnostics, 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 map.

[0062] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0063] In one embodiment, the correction factor is determined as a supplemented current commutation correction factor, preferably for switching on, as a sum, 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 design of the power electronics and are almost identical for semiconductor switches connected in parallel. Preferably, the sum of the gate-source parameter and the gate-drain parameter is equal to one. Preferably, the gate-source parameter and the gate-drain parameter represent the components of the current commutation effects and the parasitic effects. The ratio preferably depends on the switching speed of the switching elements and the commutation inductance.The larger the product of switching speed and commutation inductance, the larger the gate-drain parameter becomes. Preferably, the quotient of the second gate-drain charge to the first gate-drain charge represents the difference in the gate-drain capacitance, which is additionally charged due to the parasitic voltage drop and thus subtracts the charge from the gate-source capacitance, thereby preferably leading to slower current commutation. Here, too, the second parameter of the second switching element is preferably determined in accordance with the determination of the corresponding first parameter for the first switching element.

[0064] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0065] In one embodiment, 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. Preferably, the second parameter of the second switching element is also determined here in accordance with the determination of the corresponding first parameter for the first switching element.

[0066] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0067] In one embodiment, the correction factor is determined as a pre-discharge correction factor, preferably for switching off, as the quotient of the duration of the second identification recharging to the duration of the first identification recharging. Preferably, the second parameter of the second switching element is also determined here in accordance with the determination of the corresponding first parameter for the first switching element.

[0068] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0069] In one embodiment, the correction factor is determined as an improved pre-discharge correction factor, preferably for switching off, as the quotient of a dividend to a divisor, wherein the dividend is determined as the sum of the duration of the second identification recharging and the quotient of the difference between the second threshold voltage and the second identification threshold voltage and the third gradient of the second switching element, and wherein the divisor is determined as the sum of the duration of the first identification recharging and the quotient of the difference between the first threshold voltage and the second identification threshold voltage and the third gradient of the first switching element. Preferably, the second parameter of the second switching element is also determined in accordance with the determination of the corresponding first parameter for the first switching element.

[0070] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0071] In one embodiment, the correction factor is determined as a voltage commutation correction factor, preferably for 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 switching off, as the quotient of the second gate-drain charge to the first gate-drain charge. Preferably, the second parameter of the second switching element is also determined here in accordance with the determination of the corresponding first parameter for the first switching element.

[0072] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0073] In one embodiment, the correction factor is determined as a current commutation correction factor, preferably for switching off, as the quotient of the second gate-source capacitance to the first gate-source capacitance. Preferably, the second parameter of the second switching element is also determined here in accordance with the determination of the corresponding first parameter for the first switching element.

[0074] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0075] In one embodiment, the correction factor is determined as a complete current commutation correction factor, preferably for turn-off, as the 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. Preferably, the second parameter of the second switching element is also determined here in accordance with the determination of the corresponding first parameter for the first switching element. The transconductance is determined as described above during turn-on.

[0076] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0077] In one embodiment, the correction factor is determined as a switch-on correction factor, preferably for switching on, as the sum of the pre-charging correction factor, the current commutation correction factor and the voltage commutation correction factor, wherein the individual factors are weighted before summation by multiplication by a switch-on weighting factor, the sum of the switch-on weighting factors being equal to one and each switch-on weighting factor having a value between 0 and 1 inclusive.

[0078] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0079] In one embodiment, the correction factor is determined as a switch-off correction factor, preferably for switching off, as the 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 summation by multiplication by a switch-off weighting factor, the sum of the switch-off weighting factors being equal to one and each switch-off weighting factor having a value between 0 and 1 inclusive.

[0080] Advantageously, a method is provided for determining a correction factor for determining the second drive current for operating the second switching element of two switching elements connected in parallel.

[0081] The invention further relates to a device for determining a first parameter of a first switching element, comprising a control device configured to carry out a method described above. The control device preferably comprises a computer unit, a microcontroller, or a processor. The control device is preferably configured to control the current source driver and a voltage measuring device such that the described method steps are carried out. A device for implementing the method is advantageously 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 carry out at least one or all of the method steps.

[0082] 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. By means of the method, the device, and the drive train, more sustainable operation of the drive train is enabled.

[0083] Furthermore, the invention relates to a vehicle with a described drive train. Advantageously, a vehicle is thus provided which comprises a device with which a parameter of a first switching element can be determined.

[0084] Furthermore, the invention relates to a computer program comprising instructions which cause the device to carry out the method steps.

[0085] Furthermore, the invention 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.

[0086] 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.

[0087] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings. Short description of the drawing

[0088] In the following, the invention will be explained in more detail with reference to some figures, which show: Fig. 1 a schematic representation of a current source driver with a first and a second connected switching element. Fig. 2 a schematic representation of an equivalent circuit diagram for a switching element Fig. 3 a schematically illustrated profile of a first identification current and a simulation of a first identification gate voltage Fig. 4 A schematic representation of the course of currents and voltages during the switching-on process of a switching element Fig. 5 A schematic representation of the course of currents and voltages during a switching-off process of a switching element Fig. 6 a schematically illustrated flow diagram for a method for determining a first parameter of a first switching element. Fig. 7 a schematically illustrated vehicle with a drive train, Embodiments of the invention

[0089] The Fig. 1 shows a schematic representation of a current source driver 210, 310 with 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. A current source driver is preferably 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 in the . Fig. 1 is arranged, 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 formed by 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.

[0090] Fig. 2 shows a schematic representation of an equivalent circuit for a switching element. On the top left side the Fig. Figure 2 shows a circuit symbol for a field-effect transistor, e.g., a SiC MOSFET, with the terminals S (source), D (drain), and G (gate). Analogously, below this, a circuit symbol for another transistor, e.g., an IGBT, is shown with the terminals C (collector), E (emitter), and B (base). What both switching elements have in common is 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-hand side of the figure as an example, illustrating the parasitic properties of the transistor. 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.

[0091] Fig. Figure 3 shows a schematic representation of an identification current and an identification gate voltage. The small "x" in the reference symbols 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. In the upper area of ​​the Fig. 3 shows a curve of a predeterminable constant identification current Ix_id, as 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 UGx_id plotted against the identification time tx_id, based on the voltage values ​​of which a parameter P1, P2 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. Preferably, an identification threshold voltage Vx_th_id of a switching element 250, 350 is determined as a function of the course of the resulting identification gate voltage UGx_id.Preferably, a first, a second, and a third gradient m1_x, m2_x, m3_x are determined for the 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 postcharge tx_id_post are determined.

[0092] Fig. Figure 4 shows a schematic representation of the currents and voltages during the switching-on process of a switching element, i.e. the current and voltage curves during switching-on. As shown in the top graph of the Fig. 4, for operating and switching 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 predeterminable first drive time tx_c depending on the determined parameter P1, P2. Depending on the switching element used or the technology of the switching element used, the drive 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. In the bottom graph of the Fig. 4 shows the resulting gate voltage Vx_gs, which preferably increases during switching on. The switching on process preferably comprises the following 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 Ix_c is applied to the gate, and the maximum drain-source voltage Vx_ds (second graph from the top of the Fig. 4) at the switching element, no drain-source current Ix_d flows yet (third graph from the top of the Fig. 4) 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 rise. During voltage commutation, a preferably positive drive current is still applied to the gate, the drain-source voltage decreases and reaches its minimum, the drain-source current remains 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 retains its minimum value, the drain-source current remains maximum, and the gate voltage continues to rise.Preferably, the, preferably positive, control current is constant at a current value in the individual time segments or it varies depending on the time segment and is predetermined depending on the determined parameters P1, P2 for each time segment, preferably with different values ​​(in the . Fig. shown dotted). Alternatively, the control current can also be specified as a curve for each time segment, if required.

[0093] Fig. Figure 5 shows a schematic representation of the current and voltage curves during the switching-off process of a switching element, i.e. the current and voltage curves during switching-off. As shown in the top graph of the 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 predeterminable first drive time tx_off_c as a function of the determined parameter P1, P2. Preferably, the order of magnitude of the duration of the first drive time tx_off_c corresponds to that of the first drive time tx_c. Depending on the switching element used or the technology of the switching element used, the drive 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. In the bottom graph of the Fig. 5 shows the resulting gate voltage Vx_gs, which preferably decreases during the turn-off process. The turn-off process preferably comprises the following successive time segments: 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, and the minimum drain-source voltage Vx_ds (second graph from the top of the Fig. 5) at the switching element, the maximum drain-source current Ix_d flows (third graph from the top of the Fig. 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 decrease.Preferably, the, preferably negative, control current is constant at a current value in the individual time segments or it varies depending on the time segment and is predetermined depending on the determined parameters P1, P2 for each time segment, preferably with different values ​​(in the . Fig. shown dotted). Alternatively, the control current can also be specified as a curve for each time segment, if required.

[0094] Fig. 6 shows a schematically illustrated flowchart 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 l1_id 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 l2_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 l1_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 l2_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.

[0095] Fig.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

[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 (l1_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 curve 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 curve of the resulting first identification gate voltage (UG1_id). [2] Method according to claim 1, comprising the further step: Applying (160) a first control current (l1_c) for a predeterminable first control 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] 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 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) is minimal. [5] Method according to one of the preceding claims, wherein the duration of a first identification pre-charging (t1_id_pre) is determined as the time from the start of the application (110) of the predeterminable constant first identification current (l1_id) to the gate (252) of the first switching element (250) until the time at which the gradient of the first identification gate voltage (UG1_id) over the first identification time (t1_id) is minimal. [6] Device (320) for determining a first parameter (P1) of a first switching element (250), with a control device (325) which is designed to carry out a method (100) according to one of the preceding claims 1 to 5. [7] Drive train (300) with a device (320) according to claim 6 [8] Vehicle (400) with a drive train (300) according to claim 7 [9] A computer program comprising instructions causing the device according to claim 6 to carry out the method steps according to any one of claims 1 to 5. [10] A computer-readable medium comprising instructions which, when executed by a device according to claim 6, cause the device to perform the method steps according to any one of claims 1 to 5.

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