Method and device for operating power semiconductor element

Abstract

The invention relates to a method and a device for operating a power semiconductor element comprising a contact resistance that can be set for a power current (I), in which a control variable (SGmin) for setting a minimum contact resistance is varied, in which the control variable (SGmin) for setting the minimum contact resistance is set to a target value (ZW), the target value deviates from a recommended value (SGminr) for adjusting the target minimum contact resistance and facilitates a reduction of the minimum contact resistance in comparison to the target minimum contact resistance, and wherein the control variable (SGmin) is adjusted to the target value (ZW) if a current or future high-current event is detected.

Description

Technical Field

[0001] The invention relates to a method and a device for operating a power semiconductor component. Background Art

[0002] Power semiconductor components are used in electric or hybrid vehicles, as well as in other applications. These power semiconductor components can be, for example, components of a pulse inverter (PWR), which is a key component of an electric vehicle. The optimization of these components has a positive impact on the entire drive train and thus contributes to real added value for the end consumer. The commutation unit (Kommutierungszelle) of the PWR consists of an intermediate circuit and at least one half-bridge. The optimization can be performed not only mechanically, for example, on the layout of the half-bridge, on the connection of the intermediate circuit, but also electrically, for example, by optimizing the gate driver circuit or optimizing the semiconductor properties. In an electric or hybrid vehicle, the PWR can be part of a traction grid and is used to provide an AC voltage for an electrically driven motor (elektrische Antriebsmaschine).

[0003] For example, the power semiconductor element can be configured as a silicon carbide MOSFET. The gate voltage recommended for such a MOSFET to adjust the rated maximum or minimum contact resistance is generally provided by the semiconductor manufacturer. For example, the recommended value for adjusting the rated minimum contact resistance of each manufacturer is between 15V and 18V. Generally, the recommended value is kept unchanged during operation. The chip area of ​​the power semiconductor element is often designed with respect to the highest current that occurs during the control. In the case of high coolant and ambient temperatures, such a current can occur, for example, in a short-term boost operation (Boostbetrieb) with a duration of 5-20 seconds. The active short-circuit fault of the drive motor can also be selected as a design criterion because the highest current occurs here.

[0004] Document US 2011 / 007536 A1 relates to a device for controlling an inverter and in particular to the suppression of surge voltages and the reduction of static losses.

[0005] Document US2019 / 0149145 A1 discloses a gate driver for a solid-state switch of a vehicle power module, wherein a variable resistor is coupled between the emitter of a mirror switch and the emitter of a load switch.

[0006] Document US 10,505,538 B1 discloses a circuit topology and a corresponding control method for use in a system when supplying energy to a controlled load, such as a multiphase motor or an ohmic load, and in particular discloses a dynamic gate control system and a control method that jointly overcome the limitations of a specific circuit topology that is tailored to the worst-case dimensioning of the gate resistor.

[0007] Document WO 2021 / 047768 A1 discloses a power semiconductor switch, such as an IGBT, and in particular reducing the thermal load of the power semiconductor switch.

[0008] Document US 2009 / 0001915 A1 relates to a method and a device for controlling an electric drive, in particular for voltage control of an electric machine.

[0009] The technical problem addressed here is to provide a method and a device for operating a power semiconductor component which increase the range of application of the power semiconductor component without changing, in particular increasing, the installation space of the power semiconductor component. Summary of the invention

[0010] A method for operating a power semiconductor component is proposed, which comprises a contact resistance that can be adjusted for the power current. The power semiconductor component can be a field effect transistor or a thyristor. For example, the power semiconductor component can be a MOSFET (metal oxide semiconductor field effect transistor), in particular a silicon MOSFET or a gallium nitride MOSFET, an IGBT (insulated gate bipolar transistor), an IGCT (integrated gate commutated thyristor) or another power semiconductor component.

[0011] The power semiconductor element can be a component of a converter, in particular an inverter or a rectifier, in particular a component of a single-phase or multi-phase, in particular a three-phase inverter. The converter can in turn be a component of a power grid, in particular a traction grid of a vehicle, for example an electric vehicle or a hybrid vehicle. The traction grid can include, in addition to the converter or the power semiconductor element, an energy storage device, in particular a traction battery, a drive motor, in particular an electric drive motor and / or an intermediate circuit capacitor. Therefore, a converter, a traction grid and a vehicle with one or more power semiconductor elements are also described according to the embodiments described in the present disclosure.

[0012] In this method, a control parameter for setting a minimum contact resistance is changed. In order to switch on and off a power semiconductor element, the control parameter can be changed between a recommended minimum value and a recommended maximum value, wherein if the control parameter is set to the recommended minimum value or the recommended maximum value, the power semiconductor element is switched to a state of switching on and thus switching to a state of conducting a power current. If the control parameter is set to the remaining value of the two recommended values, the power semiconductor element is switched to a state of switching off and thus switching to a state of not conducting a power current. The recommended minimum value and the recommended maximum value can be fixed predetermined values ​​specific to the power semiconductor element. These values ​​can be predetermined, for example, by the manufacturer of the power semiconductor element. Therefore, one of the recommended values ​​is assigned to the conducting state. The rated minimum contact resistance here represents the resistance in the conducting, i.e. connected state and can also be referred to as the so-called Rds_on, i.e. the resistance in the following state, in which the control parameter is set to the corresponding recommended value. The rated maximum contact resistance here represents the resistance in the non-conducting, i.e. turned-off state, i.e. in the following state, in which the control parameter is set to the corresponding recommended value. The control variable can be a voltage or a current, for example a gate voltage.

[0013] In the case of a MOSFET, the control variable is the gate voltage, wherein the MOSFET is switched to a conducting state with a nominal minimum contact resistance if the gate voltage is set to a recommended maximum value, for example +15 V. This value is often also referred to as Vgs, max or recommended Vgs. If the gate voltage is set to a recommended minimum value, for example -4 V, the MOSFET can be switched to a non-conducting state with a nominal maximum contact resistance.

[0014] In addition, the control variable for setting the minimum contact resistance is set to a target value, which deviates from the recommended value for setting the rated minimum contact resistance and promotes a reduction in the minimum contact resistance compared to the rated minimum contact resistance. The rated minimum contact resistance here means the contact resistance obtained if the control variable is set to the recommended value for setting the minimum contact resistance. This value is generated by the characteristics of the power semiconductor element and can also be specified by the manufacturer of the power semiconductor element, for example. In particular, the target value is outside the value range between the rated minimum contact resistance and the rated maximum contact resistance, in particular, so that the actual minimum contact resistance is less than the rated minimum contact resistance, which is obtained when the control variable is set to the recommended value assigned to the conductive state. For this purpose, for example, in the case of a MOSFET, the gate voltage can be set to a value that is greater than the recommended maximum value by a predetermined difference, such as +3V. In other words, the target value is +18V in this embodiment. The control variable for setting the minimum contact resistance can be set to a target value for a predetermined duration, wherein the predetermined duration is fixedly parameterized. Fixed parameterization can mean in particular that the duration is not changed during the life of the power semiconductor element, or the duration is only slightly changed during the life of the power semiconductor element, for example, not more than 10%. The predetermined duration can be in the range of seconds, for example, less than 10 seconds. The change can be related to the running time that has been completed. The predetermined duration can be stored in a storage device, for example, before the power semiconductor element is put into use. The setting to the target value is realized in particular under the condition that it is independent of the surge voltage of the power semiconductor element. The value of the predetermined duration can be determined here so that the total duration of the period for setting the target value does not exceed the predetermined value during the predetermined duration of the power semiconductor element. For this purpose, the number of time periods for setting the target value can be predetermined based on experts and / or practical experience or based on a model.

[0015] However, fixed parameterization is not mandatory. As will be explained further below, the duration of the control variable can also be set to the value for a duration that is not predetermined in advance.

[0016] As will be explained further below, the control variable can be provided by at least one device for providing the control variable. The device can in turn be controlled by a control and analysis device for providing the desired control variable. The control and analysis device can also analyze at least one criterion for setting the control variable to a target value. Exemplary criteria are explained further below.

[0017] According to the invention, if a future high current event is detected, the control variable is set to a target value. A high current event can in particular represent an operating scenario in which the rated or actual power current through the power semiconductor element is greater than a predetermined threshold value. In addition, in the case of a high current event, it can also be characterized by the switching frequency of the power semiconductor element being less than a predetermined switching frequency. The predetermined switching frequency is in particular selected so that the rotational frequency of the electrically driven motor, which is provided by means of an operating voltage or an operating current of the power semiconductor element, is less than the predetermined rotational frequency. A low rotational frequency can lead to a high load on the power semiconductor element, which generally provides an operating voltage or an operating current for driving the motor. The rotational frequency can be related to the frequency of the operating current (i.e., the power current) or the operating voltage.

[0018] The detection of a current or future high-current event can be realized in particular by means of an analysis device, for example the control and analysis device described above. The control and analysis device can, for example, analyze a current rated value or actual value of a power current, detected, for example, by an existing current sensor, and can detect a current high-current event if this value is greater than a predetermined threshold value. In addition, the analysis device can analyze a current rated value or actual value of a switching frequency, predetermined, for example, by an existing control device, and can detect a current high-current event if this value is less than a predetermined threshold value. The switching frequency can also be determined here as a function of the frequency of the power current, which can in particular be detected with the aid of a sensor.

[0019] For example, a future high-current event can be determined based on the time curve of the power current. Thus, for example, the rate of change of the power current can be determined, wherein a high-current event is detected if the sum of the current actual value of the power current and the product of the rate of change and a predetermined duration is greater than a predetermined threshold value. In addition, the analysis device can also determine the rate of change of the switching frequency, and if the sum of the current actual value of the switching frequency and the product of the rate of change and a predetermined duration is less than a predetermined threshold value, a future high-current event is detected. A high-current event can occur in particular if a vehicle driven by a control motor accelerates over a curb, wherein the operating voltage or operating current of the control motor is at least partially provided by a power semiconductor element. In this case, a high-current event can be detected if such a driving over or accelerated driving over a curb is detected. It can then be advantageously achieved that the curb can be driven over more easily.

[0020] It goes without saying that other high current events are also conceivable.

[0021] Therefore, it is advantageously obtained that in an operating scenario requiring a large power current, the power semiconductor element can be operated with a minimum contact resistance that is reduced compared to normal operation. This can also advantageously reduce the heat energy generated due to resistance loss when the power current flows through the power semiconductor element and thus also reduce the thermal load of the power semiconductor element. This can also be achieved, for example, at a high (semiconductor and / or ambient) temperature without exceeding the maximum temperature allowed by the power semiconductor element for a short time, wherein the temperature of the power semiconductor element is particularly related to the ambient temperature, the coolant temperature and the resistance loss. Therefore, for example, without exceeding the maximum temperature allowed, the reduction in resistance loss allows the increase of the ambient temperature and / or the coolant temperature. In addition, it is advantageously achieved that such operation can be achieved without increasing the structural space of the power semiconductor element, especially the required chip area, because there is no need to increase the structural space in order to reduce the minimum contact resistance. In other words, the power density of the semiconductor structural element can therefore be advantageously increased. This can also be advantageously achieved without increasing the manufacturing cost. Therefore, the application range of the power semiconductor element is expanded. If a large current event is detected using structural elements, especially sensors and analysis devices that are already present in the vehicle, a simple and cost-effective implementation of the method is advantageously obtained. Overall, the approach may also contribute to improved acceptability of electric vehicles.

[0022] The method can also be used in industry, energy technology, entertainment electronics, medical technology and other fields, in particular for operating power semiconductor components as components of converters. In vehicles, the method can advantageously achieve increased efficiency, reduced losses and thus also extended range.

[0023] In another embodiment, if a future high-current event is detected, the control variable is set directly to the target value. In this case, the setting is carried out before the high-current event occurs. It can be achieved that the power current through the power semiconductor element is increased before the high-current event occurs due to the reduced contact resistance, so that in the event of the occurrence, the difference between the subsequently required rated power current and the actual power current subsequently changed by the increase is smaller than the difference without the explained increase. The required rated power current can then also be set more quickly, which leads to an improved driving feel when and during the high-current event, for example, to a smoother driving over a curb.

[0024] In another embodiment, if a future high current event is detected at the detection time, the control variable is set to the target value after a predetermined duration has passed after the detection time. The predetermined duration can be the duration until the high current event occurs. The predetermined duration can also be the duration until a moment shortly before the high current event occurs, which is, for example, located at a predetermined time threshold before the occurrence of the high current event. The predetermined duration can be determined here, in particular by analyzing the value detected by at least one sensor or its time curve and / or by analyzing the value predetermined by at least one control device or its time curve, for example, by the explained analysis device to determine the predetermined duration. Such a value can be a value of the power current or the switching frequency, but it can also be a value different therefrom. This advantageously results in: reducing the heat energy generated due to the resistance loss when the power current flows through the power semiconductor element and thus also reducing the thermal load of the power semiconductor element, wherein, however, the duration of adjusting the control variable to the target value is kept as short as possible, which has an advantageous effect on the life of the power semiconductor element.

[0025] In another embodiment, current or future high-current events are detected by analyzing signals generated by vehicle sensors. Vehicle sensors can refer to sensors that are already fixedly installed in the vehicle. Exemplary sensors will be further explained below. In particular, obstacles, such as curbstones, located in front of the vehicle along the current or predicted direction of travel can be detected by analyzing optical signals, wherein driving over the obstacle indicates a high-current event. It is possible to detect high-current events by analyzing multiple signals generated by at least two different vehicle sensors. It is also possible to detect high-current events by analyzing fused signals, which are generated by output signals of at least two different vehicle sensors. As described above, the following advantages are obtained: high-current events can be detected using structural elements that are already present in the vehicle, which can achieve a simple and cost-effective implementation of the method.

[0026] In another embodiment, the signal is generated by at least one image detection device of the vehicle. The image detection device may include a CMOS or CCD sensor and generate a two-dimensional image. The image detection device may be a front camera or a reversing camera of the vehicle. As an alternative, the signal may be generated by at least one radar sensor or by at least one laser radar sensor. In addition, as an alternative, the signal may be generated by at least one torque sensor. The torque sensor may detect or determine the torque required or provided on at least one control wheel, for example, by suitable calculations based on other parameters. Thus, if the torque is above a predetermined threshold, a high current event may be detected, for example. If the vehicle includes a plurality of control wheels, such as, for example, in the case of all-wheel control, the difference between the torques required or provided on different control wheels may also be analyzed in order to detect a high current event. Thus, a first torque for controlling a first wheel or a first number of wheels, for example, a rear wheel, and another torque for controlling another wheel or another number of wheels, for example, a front wheel, may be determined, wherein a high current event is detected based on the difference between the other torque and the first torque, for example, when the difference is greater than a predetermined threshold. If the vehicle is traveling forward, for example, and it is detected that the other torque is greater than the first torque at the same rated speed for two wheels / number of wheels, it can be detected that the vehicle has passed an obstacle. In this case, a future high-current event can be detected for a power semiconductor element, which is part of an inverter for driving the first wheel or the first number of wheels. In addition, as an alternative, the signal can be generated by at least one tire position sensor. The tire position sensor can here represent a device that can detect or determine the tire position, for example by suitable calculation based on other parameters, such as displacement parameters, speed parameters or acceleration parameters. If an obstacle is detected in front of the vehicle along the current or predicted driving direction based on the current tire position, a current or future high-current event can be detected, wherein the obstacle position can be determined, for example, by predetermined map data. By using the output signal of the explained sensor, a reliable and accurate detection of the high-current event is advantageously produced.

[0027] In another embodiment, a current or future high-current event is detected based on the actual value of the power current and / or the time curve of the actual value of the power current, wherein the power current is the current flowing through the power semiconductor element. An exemplary embodiment of such a detection has been explained above. However, in this embodiment, it is important to analyze the power current of the power semiconductor element whose contact resistance subsequently changes. Since a current variable specific to the power semiconductor element is thus analyzed, a reliable detection is advantageously obtained.

[0028] In another embodiment, a current or future high current event is detected according to the actual value of the power current and / or the time curve of the actual value of the power current, wherein the power current is the current flowing through another power semiconductor element. The exemplary implementation of such detection has been explained above. However, in this embodiment, it is important not to analyze the power current of the power semiconductor element whose contact resistance is subsequently changed, but to analyze the power current of another power semiconductor element different from it. Thus, an alternative detection of a high current event is advantageously obtained. If the power semiconductor element-whose contact resistance is subsequently changed-is part of the first inverter, then the other power semiconductor element can also be, for example, part of the first inverter. But preferably, the other power semiconductor element is part of another inverter different from the first inverter. Therefore, for example, the vehicle can include different drive inverters, for example, for driving different wheels, such as in the case of an all-wheel vehicle. In this case, the first inverter can be used, for example, to drive the first wheel or the first number of wheels, such as the rear wheel, and the other inverter can be used, for example, to drive another wheel or another number of wheels, such as the front wheel.

[0029] In another embodiment, if a current or future high current event is detected, the cooling power and / or power current is additionally increased. The cooling power can represent the power of a cooling device for cooling a power semiconductor element. The power current can represent the current of a power semiconductor element whose contact resistance is reduced. The increase can be achieved here - as previously explained with respect to the control parameter - directly after the detection time or for a predetermined duration after the detection time. The increase in power current can be achieved in particular in the following case, that is, if the power semiconductor element is part of an inverter for providing an operating voltage for an externally excited synchronous motor, which in this case forms the described drive motor. The increase in cooling power can be achieved in particular by increasing the coolant volume flow of the coolant pump. By increasing the coolant capacity, the temperature increase of the power semiconductor element, especially during a high current event, can be slowed down or even the temperature can be reduced, which has a positive impact on the life, in particular, prolongs the life. By increasing the power current—as described above—the difference between the required rated power current in the event of a high-current event and the actual power current changed by the increase is reduced, whereby the required rated power current can also be advantageously adjusted more quickly, which leads to an improved driving feel when and during a high-current event.

[0030] In another embodiment, the setting of the control variable to the target value is canceled if a predetermined time period has elapsed or if a criterion related to the power semiconductor temperature is met. In particular, the setting can be terminated if the semiconductor temperature is greater than a predetermined temperature threshold value or if the semiconductor temperature changes by more than a predetermined measure. This can advantageously increase operational safety and extend the service life of the power semiconductor component.

[0031] In addition, if the rated value of the power current is additionally greater than a predetermined threshold value, the control variable can be set to the target value. In addition, if the semiconductor temperature, that is, the temperature of the power semiconductor element, is greater than a predetermined threshold value as an alternative, preferably but cumulatively, the target value can be further set. In addition, the rated value of the power current can be provided via a bus system, in particular via an SPI bus system. As an alternative or cumulatively, the semiconductor temperature and / or the ambient temperature can be detected by a temperature sensor and / or provided via a bus system. In addition, the duration of the fixed parameterization can be less than or equal to 20 seconds, preferably less than or equal to 10 seconds. In addition, the sum of the following durations can be determined, during which the control variable for setting the minimum contact resistance is set to the target value, wherein only when the sum is less than or equal to the predetermined threshold value, the control variable is set to the target value. For example, it is possible that not only the sum valid at the current time but also the predetermined threshold value is stored in a storage device and, for example, called by a control device. If the check results that the setting to the target value can be performed, the currently stored sum can be incremented by a predetermined duration and the resulting value can be stored as an updated sum. The predetermined threshold value can be selected depending on the application and can be, for example, 100 seconds or more. The predetermined threshold value can be selected in particular such that the power semiconductor element is operated with a control variable outside the recommended value range during a service life that is no longer than an allowed duration. This advantageously results in improved operational safety while at the same time increasing the range of applications.

[0032] Furthermore, the setting to the target value can be realized in the following way: the target value is transmitted as a setpoint value to a device for providing the control variable. In this case, a device can be controlled, which also provides a control variable with a recommended value for setting the setpoint minimum contact resistance, in order to provide a control variable with a target value. This can be realized by a suitable control or regulation strategy. This advantageously results in a simple setting to the target value, in particular without the need for additional components.

[0033] As an alternative, a recommended value for setting the nominal minimum contact resistance can be transmitted to the device for providing the control variable as the nominal value, wherein the device for providing the additional control variable provides the additional variable corresponding to the difference between the target value and the initial value or the recommended value provided by the device for generating the control variable. This advantageously results in that the corresponding function can be easily upgraded, in particular when the device for providing the control variable is not designed for providing the target value.

[0034] The device for providing the additional variable can be a device which is designed in hardware technology to be separate from the device for providing the control variable. It is also possible to operate the device for providing the additional control variable, in particular if a fault situation is detected, such as, for example, a short circuit or an active short circuit or a malfunction or inaccessibility of the device providing the control variable, so that it provides a target value or a recommended value (and therefore not only the additional variable). This advantageously results in an increase in the range of applications.

[0035] Furthermore, a device for operating a power semiconductor element is proposed, which comprises a contact resistance that can be adjusted for the power current, wherein the device comprises at least one device for providing a control variable for adjusting the contact resistance. The device can be, for example, a driver circuit, in particular a gate driver circuit. The device can also comprise the device already described above for providing an additional control variable and be designed so that the control variable and the additional control variable are added together to provide the resulting control variable.

[0036] Furthermore, a control variable for setting the minimum contact resistance is changed, wherein the control variable for setting the minimum contact resistance is set to a target value which deviates from a recommended value for setting the nominal minimum contact resistance and leads to a reduction in the minimum contact resistance compared to the nominal minimum contact resistance.

[0037] According to the invention, the device comprises at least one device for detecting a high current event, wherein if a current or future high current event is detected, the control variable is set to a target value. The device may comprise the above-mentioned control device or control and analysis device or analysis device, which controls the operation of the device for providing the control variable and, if possible, the operation of the device for providing the additional control variable and detects the high current event. In addition, the device may comprise a storage device, for example, for fixing the value of the parameterized duration. The storage device may also be used to store the above-mentioned sum. In addition, the device may comprise at least one interface, for example, for receiving a rated value, a temperature value, an activation signal or for connecting to a superordinate system in terms of data technology, which superordinate system may be a system inside the vehicle, but may also be a system outside the vehicle. The device may also comprise a power semiconductor element. In addition, the device may comprise at least one vehicle sensor, in particular one of the above-mentioned vehicle sensors. The device may also comprise at least one current sensor for detecting the power current and / or a device for determining / detecting the switching frequency of the power semiconductor element and / or a temperature sensor or an interface for connecting such a sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The device can be configured in this case so that the method according to the embodiment described in the present disclosure with the explained advantages is implementable with the device. Therefore, the method is implementable with the device configured according to the embodiment described in the present disclosure.

[0039] The present invention is further explained according to various embodiments.

[0040] Figure 1 A schematic flow chart showing a method according to the present invention;

[0041] Figure 2 A schematic flow chart of a method according to the present invention in another embodiment is shown;

[0042] Figure 3 shows a schematic time curve of the control parameter;

[0043] Figure 4 A schematic block diagram showing an apparatus according to the present invention;

[0044] Figure 5 A schematic block diagram showing the device according to the invention in a vehicle; and

[0045] Figure 6 An exemplary time profile of the power current is shown.

[0046] In the following, the same reference numerals denote elements having the same or similar technical features. DETAILED DESCRIPTION

[0047] Figure 1 1 and 2. A schematic flow chart of the method according to the invention is shown. In a first step S1, it is checked whether a control variable SGmin for setting a minimum contact resistance, for example a power semiconductor element (for example a MOSFET 1, 2 (see Figure 4 )) of the gate voltage VG (see Figure 3 ) should be set to a target value ZW, which deviates from the recommended value SGmin_r for setting the rated minimum contact resistance and leads to a reduction in the minimum contact resistance compared to the rated minimum contact resistance, which applies when the control variable SGmin is set to the recommended value SGmin_r. If a current or future high-current event is detected, the control variable SGmin is set to the target value in a second step S2. Cumulatively, the cooling power for the power semiconductor element and / or the power current I through the power semiconductor element can also be increased (see Figure 6 ). The adjustment or increase can be performed immediately after the detection time. As an alternative, the adjustment or increase can be performed after a predetermined duration has elapsed after the detection time, in particular when a future high current event is detected. Thus, the adjustment can be performed when a high current event occurs or shortly before it, for example, for a predetermined duration before it occurs.

[0048] The control variable SGmin can here be set to a target value ZW for a predetermined duration. The predetermined duration can be fixedly parameterized. In this case, it can be checked repeatedly, in particular periodically, in a third step S3 whether the duration with the set target value ZW is less than a predetermined and fixedly parameterized threshold value Tf or is equal to the threshold value Tf. The threshold value Tf thus corresponds to the predetermined duration. If this is not the case, the time count value ct is incremented by the time increment Δt and the third step S3 is executed again. As soon as the time count value ct is greater than the predetermined threshold value Tf, the control variable SGmin is set to the recommended value SGmin_r in a fourth step S4. It goes without saying that the control variable can then also be set back to a value that deviates from the control variable SGmin for setting the rated minimum contact resistance. The predetermined threshold value Tf can here be stored in the storage device 9 (see Figure 4 ) and can be retrieved from this storage device for analysis. However, it is also possible to set the control variable SGmin to a value different from the target value if the high-current event ends, in particular also before the target value is reached.

[0049] If no current or future high-current event is detected in the first step S1 , the control variable SGmin is set to the recommended value SGmin_r or is unchanged.

[0050] High current events can be detected by analyzing the signals generated by vehicle sensors. The current value of the signal and / or the time curve of the signal can be analyzed. Such a vehicle sensor can be, for example, an image capture device 11 of the vehicle, in particular an image capture device 11 designed as a front camera. The vehicle sensor can also be a torque sensor or a device for determining the torque provided at the drive wheel.

[0051] It is also possible to calculate the power current I flowing through the power semiconductor element whose contact resistance is reduced (see Figure 6 ) and / or the time curve of the actual value of the power current I. Alternatively or cumulatively, a high-current event can be detected based on the actual value of the power current I flowing through a power semiconductor element other than the power semiconductor element whose contact resistance is reduced and / or the time curve of the actual value of the power current I.

[0052] Figure 2 A schematic flow chart of a method according to the present invention in another embodiment is shown. Figure 1 In the embodiment shown in , the control variable SGmin is not set to the target value ZW for a predetermined duration. Instead, the setting is canceled if the temperature T of the power semiconductor element is greater than a predetermined threshold value Ts. For this purpose, it can be checked in particular periodically in a third step S3 whether the temperature T is less than or equal to the threshold value Ts. If this is the case, the third step S3 is executed again. As soon as the temperature T is greater than the predetermined threshold value Ts, the control variable SGmin is set to the recommended value SGmin_r in a fourth step S4. The predetermined threshold value Ts can be stored in the storage device 9 (see Figure 4 ) and can be retrieved from this storage device for analysis. Of course, in this embodiment, it is also possible to cancel the setting if the high-current event ends, in particular also before the temperature threshold value Ts is reached.

[0053] Figure 3 The control variables, namely the MOSFETs 1 and 2 (see Figure 4 ) is a schematic time curve of the gate voltage VG of the MOSFET 1, 2. The MOSFET 1, 2 can be, for example, a component of a converter, which in turn can provide an AC voltage for operating an electric machine, for example a traction motor in an electric or hybrid vehicle. For this purpose, the MOSFET 1, 2 can be operated in a pulsed manner, wherein the gate voltage VG is operated with a duty cycle—which can be determined by a higher-level system—between a value for setting a minimum contact resistance and a value for setting a maximum contact resistance. Figure 3 , it is shown that the recommended value SGmin_r of the control variable for setting the nominal minimum contact resistance, ie the recommended minimum contact resistance, is +15 V. The recommended value for setting the nominal maximum contact resistance is -4 V.

[0054] At a first time t1, a high current event is detected and the minimum contact resistance is further reduced compared to the contact resistance at the set recommended control variable SGmin_r. The target value ZW is, for example, +18 V. It is also shown that the control variable SGmin remains set to the target value ZW until a further time t2, wherein the time difference between the second time t2 and the first time t1 corresponds to a predetermined threshold value Tf, which can be, for example, 10 or 20 seconds.

[0055] Figure 4 FIG. 3 shows a schematic block diagram of a device 3 according to the present invention. The device 3 is used to generate a voltage for a power current I (see Figure 6 ) to operate a power semiconductor element with an adjustable contact resistance, for example, for operating MOSFETs 1, 2. The power semiconductor element may be part of a power grid, which may be, for example, a traction grid of an electric or hybrid vehicle. The power grid may include an intermediate circuit capacitor CZ. The first MOSFET 1 may be a so-called high-side MOSFET of a half-bridge of a converter, and the second MOSFET 2 may be a so-called low-side MOSFET of a half-bridge of a converter, wherein the MOSFETs 1, 2 are operated so that a DC voltage in the intermediate circuit 4 is converted into an AC voltage of a phase line 5. The device 3 includes a first device 6 for providing a control variable for adjusting the contact resistance of the first MOSFET 1 and a second device 7 for adjusting the contact resistance of the second MOSFET 2. Such devices 6, 7 are known to those skilled in the art and may include electrical or electronic components for providing a control variable, for example, in the form of a gate voltage VG. In addition, the device 3 includes a control and analysis device 8, which is, for example, in the form of a microcontroller or an integrated circuit or may include such a microcontroller or integrated circuit. The control and analysis device 8 controls the devices 6, 7 so that they provide the desired time curve of the control variable.

[0056] Not present Figure 4 , an energy supply device for supplying power to the devices 6, 7, wherein the energy supply device provides the desired control variable from a different energy storage device, such as a capacitor or a different energy storage device. In particular, the control and analysis device 8 can detect high current events. In addition, the control and analysis device 8 can analyze the variable used for detection, such as the output signal of at least one sensor. The control and analysis device 8 can then control the first device 6, the second device 7 or both devices 6, 7 so that the target value ZW is set as the control variable SGmin for setting the minimum contact resistance (see, for example Figure 1), wherein the target value deviates from the recommended value SGmin_r for setting the nominal minimum contact resistance as described above. For this purpose, the control and evaluation device 8 can in particular change the nominal value for the control variable provided by the device 6, 7, which is the output variable of the device 6, 7, for example from the value +15V to the value +18V.

[0057] Figure 5 A schematic block diagram of the device 3 according to the invention is shown in a vehicle 14, in particular an electric or hybrid vehicle. The vehicle 14 comprises the device 3 and an image capture device 11, which can form, for example, a front camera of the vehicle 14. A curb 12 is shown here, which is arranged in the driving direction 13 in front of the vehicle 14. If the vehicle 14 continues to drive in the driving direction 13, the vehicle passes the curb 12, in particular it passes the curb 12 at an accelerated speed. This is done, for example, by a control and analysis device 8 (see Figure 4 ) By analyzing the output signals provided by the image detection device 11, a kerb 12 located in front of the vehicle 14 in the current driving direction 13 can be detected. A "driving over" can then be detected as a future high-current event. In addition, by analyzing the output signals provided by the image detection device 11, the distance of the vehicle 14 to the kerb 12 can be determined and then the duration until the kerb 12 is reached and thus until the high-current event occurs can be determined based on the vehicle speed. The tire position can also be determined in order to predict or detect the occurrence of a high-current event.

[0058] Figure 6 An exemplary time curve of the power current I over time t is shown. The first row shows an ideal time curve of the power current I in normal operation without a high current event. It is clear that neither the amplitude nor the frequency of the power current changes. The second row shows the time curve of the power current I in the case of a high current event. Since the first time t1, not only the amplitude of the power current I has increased, but also the frequency of the power current I has decreased. Therefore, after the first time t1, a high current event can be detected by analyzing these two variables.

[0059] Reference numerals list

[0060] 1.2 MOSFET

[0061] 3. Installation

[0062] 4Intermediate circuit

[0063] 5-phase line

[0064] 6 A first device for providing a control parameter

[0065] 7. Second device for providing control parameters

[0066] 8Control and analysis equipment

[0067] 9 Storage Devices

[0068] 11Image detection equipment

[0069] 12 Roadside Stone

[0070] 13 Driving Directions

[0071] 14 Vehicles

[0072] ct time count value

[0073] CZ intermediate circuit capacitor

[0074] IPower Current

[0075] S1 First step

[0076] S2 Second step

[0077] S3 Step 3

[0078] S4 Step 4

[0079] SGmin is used to adjust the control parameter of minimum contact resistance

[0080] SGmin_r is used to set the recommended value of the rated minimum contact resistance

[0081] T Temperature

[0082] Tf parameterized threshold

[0083] Ts temperature threshold

[0084] t time

[0085] t1 first moment

[0086] t2 second moment

[0087] VG gate voltage

[0088] ZW target value

[0089] Δt time increment

Claims

1. A method for operating a power semiconductor component, the power semiconductor component comprising a contact resistance that can be adjusted for a power current (I), wherein a control variable (SGmin) for adjusting a minimum contact resistance is changed, wherein the control variable (SGmin) for adjusting the minimum contact resistance is adjusted to a target value (ZW) that deviates from a recommended value (SGmin_r) for adjusting a rated minimum contact resistance and leads to a reduction of the minimum contact resistance compared to the rated minimum contact resistance, It is characterized in that If a current or future high-current event is detected, the controlled variable (SGmin) is set to the target value (ZW).

2. The method according to claim 1, characterized in that If a future high-current event is detected, the controlled variable (SGmin) is set directly to the target value (ZW).

3. The method according to claim 1, characterized in that: If a future high-current event is detected at a detection time, the controlled variable (SGmin) is set to the target value (ZW) after a predetermined time period has elapsed after the detection time.

4. The method according to any one of the preceding claims, characterized in that Detect current or future high current events by analyzing signals generated by vehicle sensors.

5. The method according to claim 4, characterized in that The signal is generated by at least one image detection device (11), at least one radar sensor, at least one lidar sensor, at least one torque sensor and / or at least one tire position sensor.

6. The method according to any one of claims 1 to 3, characterized in that A current or future high-current event is detected based on an actual value of a power current (I) and / or a time profile of the actual value of the power current (I), wherein the power current (I) is the current flowing through the power semiconductor component.

7. The method according to any one of claims 1 to 3, characterized in that A current or future high-current event is detected based on an actual value of a power current (I) and / or a time profile of the actual value of the power current (I), wherein the power current (I) is the current flowing through a further power semiconductor component.

8. The method according to any one of the preceding claims, characterized in that If a current or future high current event is detected, the cooling power and / or the power current (I) is additionally increased.

9. The method according to any one of the preceding claims, characterized in that If a predetermined period of time has elapsed or if a criterion relating to the temperature of the power semiconductor is met, the adjustment of the controlled variable (SGmin) to the target value (ZW) is cancelled.

10. A device for operating a power semiconductor element, the power semiconductor element comprising a contact resistance adjustable for a power current (I), wherein the device (3) comprises at least one device (6, 7) for providing a control variable (SGmin) for adjusting the contact resistance, wherein the control variable (SGmin) for adjusting the minimum contact resistance is changed, wherein the control variable (SGmin) for adjusting the minimum contact resistance is adjusted to a target value (ZW), which deviates from a recommended value (SGmin_r) for adjusting a rated minimum contact resistance and causes the minimum contact resistance to be reduced compared to the rated minimum contact resistance, characterized in that The device (3) comprises at least one means for detecting a high-current event, wherein the control variable (SGmin) is set to the target value (ZW) if a current or future high-current event is detected.

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