Commanded reduction of the slope of the flanks during overflows

Abstract

An inverter control device is described, comprising a driver circuit (T) and a control circuit (MC) superior to the driver circuit (T). The control circuit (MC) is configured to receive at least one current value. When the current value falls within a predetermined interval, a shutdown signal (IS) is transmitted to the driver circuit (T), causing it to enter a permanent OFF state. Furthermore, this signal causes the driver circuit (T) to execute the transition to the OFF state with a reduced slew rate. Furthermore, a corresponding procedure for switching off a circuit breaker is described.

Description

[0001] Electric vehicles with electric traction drive systems are equipped with power electronics and a high-performance traction battery. Due to the design of these drive components, short circuits can cause serious damage. In the event of a short circuit, the traction drive system is deactivated.

[0002] Therefore, protective mechanisms are provided that open the current path in the event of a short circuit. Furthermore, in the event of a short circuit, the relevant high phase current is detected, and the driver circuit controls the control terminals (gates) of the power electronics to put the power electronics transistors into a permanently (or at least temporarily) safe state.

[0003] It is an object of the invention to show a possibility how undesirable effects when deactivating an electric drive can be reduced.

[0004] This problem is solved by the subject matter of the independent claims. Further properties, features, embodiments, and advantages are revealed by the dependent claims, the description, and the figure.

[0005] It was recognized that in the case of an overcurrent ("soft" short circuit), the driver circuit is insensitive enough and the driver circuit's response is not adapted to the magnitude of the overcurrent, especially for overcurrents that are lower than the currents in a direct, low-resistance short circuit, but which still require shutdown. It was recognized that with overcurrents (below the short-circuit currents in a low-resistance short circuit), disruptive overvoltages can occur if the shutdown occurs with the highest possible edge steepness, as with a negative pulse width modulation (PWM) edge or as with a low-resistance short circuit. Therefore, a reduced edge steepness during shutdown is provided for overcurrents that are greater than permissible PWM currents – and therefore require shutdown – and that are smaller than the currents in a low-resistance short circuit.On the one hand, a reduced edge steepness is possible because the currents are smaller than in a low-resistance short circuit, and on the other hand, the reduced edge steepness can prevent high (component-critical) overvoltages or voltage spikes. Thus, if the current value is within a predetermined interval (the lower limit of which is defined, for example, by the maximum permissible current in PWM or traction mode, and the upper limit of which is defined, for example, by the maximum permissible specification of the switched power semiconductor), a control circuit that controls the driver circuit outputs a shutdown signal.

[0006] The shutdown signal indicates that the driver circuit is transitioning to an OFF signal with a reduced edge slew rate. The edge slew rate provided by the driver circuit is preferably less than a slew rate that would cause the power semiconductor to operate outside its specifications. The slew rate can decrease with increasing current (to avoid overvoltages caused by shutdown even at higher current values). Alternatively, a predetermined, constant slew rate is used. The slew rate refers to the absolute value of the switching edge.

[0007] In particular, a gate driver (generally: a driver circuit) can receive a signal from a microcontroller as the higher-level unit that a shutdown according to a special short-circuit configuration is to be carried out by the gate driver. In this case, the driver switches off more slowly than usual in order not to destroy the power semiconductor (due to overvoltages that can result from rapid switch-off at high currents). The shutdown is carried out when a "soft" short circuit occurs, i.e. when a current value is detected (by the microcontroller) that lies within a predetermined interval. The predetermined interval represents the current values ​​that occur during a "soft" short circuit, i.e. an overcurrent that is above the maximum (maximum permissible) operating current, but below a threshold that can be identified by the gate driver as a ("hard") short circuit.The interval can therefore have a lower limit value that is higher than the maximum (maximum permissible) operating current, and can have an upper limit that is not higher than the threshold that can be identified by the gate driver as a ("hard") short circuit. Current values ​​within the specified interval can be referred to as a soft short circuit. Current values ​​above the interval or above an overcurrent limit can be referred to as a hard short circuit. The higher-level control circuit (microcontroller) is able to detect the soft short circuit; the driver circuit is not. Therefore, the higher-level unit detects whether a current value lies within the specified interval (corresponding to a soft short circuit) and transmits the shutdown signal to the driver circuit. The shutdown signal causes a shutdown in the driver circuit, but with a reduced edge steepness, i.e.reduced compared to a turn-off edge slew that the driver circuit generates in clocked operation (i.e. in normal operation, where the maximum current value is below the interval). In normal operation, there are few losses due to the high edge slew; with the reduced edge slew, there is a reduced overvoltage. This reduced overvoltage is reduced compared to the overvoltage that would result if the driver circuit applied the edge slew in normal operation / clocked operation due to the turn-off signal (of the higher-level control circuit). In particular, the current value refers to the phase current, i.e. the current that flows (for the relevant phase) through the transistor that is controlled by the driver circuit. In the case of multiple phases, for example in the case of multiple half-bridges provided by transistors, the current value refers to the relevant half-bridge orthe transistor in question; therefore, multiple current values ​​can be provided for multiple phases. The current value refers to the current flowing in (a power path) of a power circuit controlled by the driver circuit, in particular to at least one power switch controlled by the driver circuit and preferably part of the power circuit. The power circuit is, in particular, an inverter, such as a traction inverter. The power circuit has at least one power switch controlled by the driver circuit.

[0008] An inverter control device with a driver circuit and a control circuit superordinate to the driver circuit is described. In certain embodiments, the control circuit controls the driver circuit, for example with clocked or pulse-width modulated signals during normal operation. The control circuit is configured to receive a current value, for example directly or indirectly from a current sensor that measures the current itself, or from a device that calculates a current value (for example from other current values). The control circuit has an input for receiving the current value. The control circuit is further configured to evaluate the current value and, in particular, to compare it with one or more limit values. The control circuit is configured, for example, to transmit a shutdown signal to the driver circuit when the current value lies within a predetermined interval.The control circuit can be configured to compare the current value with the lower limit and / or the upper limit of the interval. The result of the comparison leads to the shutdown signal. The shutdown signal (which is generated when the current value is within the interval) causes the driver circuit to enter a permanent or temporary OFF state. Permanent or temporary means in particular that the OFF state is canceled after a safety period or after a reset or another event (and can be followed, for example, by clocked control, as is characteristic of fault-free operation). In the OFF state, the semiconductor switches controlled by the driver circuit are in the open state. In the OFF state, the driver circuit outputs a semiconductor switch control signal, such as a gate signal, which is configured to put downstream semiconductor switches into an OFF state.The driver circuit is also caused by the switch-off signal to execute the transition to the OFF signal with a reduced edge steepness. The interval represents a current range which lies above the maximum (permissible) operating current and which, in particular, lies below a detection threshold of the driver circuit. The driver circuit can be set up, in the same way as the control circuit, to evaluate a current and compare it with an upper limit in order to carry out a switch-off process; however, the upper limit of the driver circuit is greater than the upper limit of the interval, such that the driver circuit is less sensitive. The switch-off signal of the control circuit indicates that a “soft” short circuit is present, i.e. a current above the maximum operating current, but less than the overcurrent detection threshold of the driver circuit, i.e. a current value in the interval. If the current value lies above the interval, the control circuit maya different shutdown signal is emitted, in particular one that causes the driver circuit to shut down with a faster edge steepness than a shutdown signal assigned to a current value within the interval. Unless otherwise specified, a "soft" short circuit means a current value within the interval, and a "hard" short circuit or a short circuit without further specification means a current value above the interval. The shutdown signal can thus identify the current value and indicate that the current value lies within the interval ("soft short circuit"), can indicate the current value itself so that it can be assigned to an edge steepness (reduced according to the current value) according to a current value-edge steepness assignment, or both.Simply transmitting a current value via a specific (logical) channel can be interpreted as a signal to set an OFF state ("soft short circuit present"), while the magnitude of the transmitted current value determines the reduced edge slew rate. The reduced edge slew rate, or a signal representing it, can also be transmitted to the driver circuit as a shutdown signal. In this case, the control circuit has a current value-edge slew rate mapping.

[0009] The control circuit can be provided to receive the current value (from a current sensor or from a unit that stores the current value, see description of the figures) in order to transmit the current value to the driver circuit, and can also be configured to generate a (clocked) control signal, in the sense of a motor control. The current value and the control signal can then be transmitted via the same (physical) channel, and the connection between the driver circuit and the control circuit, or these units themselves, can be designed accordingly. However, these two functions can be separated and implemented by different units. For example, the control circuit, as the first unit, can be configured to transmit the current value to the control circuit, while a control signal generation unit, as the second unit, which exists alongside the first unit, transmits the control signal to the driver circuit.In this case, the control circuit can be considered a current value source, while the control signal generation unit should be considered a control signal source. If both functions coincide, as mentioned above, or are implemented by the same unit, then the control circuit can be considered a current value source and a control signal source.

[0010] The higher-level control unit is preferably connected to a current sensor or is configured to provide the current value (e.g., by calculation, evaluation of a measurement, etc.). A current sensor is generally defined as a device that measures the current, such as a Hall sensor or a shunt resistor, or that detects the current by calculation, such as by calculating from other current values ​​obtained by measurement. The current sensor is configured to detect a current flowing in the power switch controlled by the driver circuit. The current sensor is configured to detect a current flowing in the power path or phase in which the power switch controlled by the driver circuit is provided. If there are n phases, the current can be measured in n-1 phases, while for the remaining phase the current can be calculated from the node rule.The measured or calculated current defines the current value. The circuit breaker is in particular part of a power circuit, which may also have several circuit breakers. The current value can be determined (measured or calculated) as the current value that flows through the circuit breaker (or phase) that is controlled by the driver circuit, i.e. which is controlled indirectly (via the driver circuit) by the control unit. When several circuit breakers are controlled by the control unit, the current value of each circuit breaker or at least of each phase of the power circuit is preferably determined. The current value is determined relative to the relevant phase or relative to the relevant circuit breaker. The reduced edge steepness is then preferably provided individually for the relevant circuit breaker or phase.Alternatively, the reduced edge steepness is provided for all phases. If multiple current values ​​are present from multiple phases or circuit breakers, the edge steepness can be determined based on the mean, the median, or the largest value thereof. The driver circuit can be configured to provide the reduced edge steepness individually for each phase or for each circuit breaker based on the relevant current value. The driver circuit can be configured to provide a reduced edge steepness for all phases or circuit breakers of the power circuit, for example depending on the mean, median, or the absolute maximum of all current values. The current sensor is thus preferably configured to determine a current on an output side (AC side) of the power circuit, in particular on at least one phase current line of the power circuit.

[0011] Other embodiments provide that the current value represents the current introduced into the power circuit (i.e., the supply current). In these embodiments, the current sensor is configured to measure a current on a supply line (DC side) of the power circuit. The driver circuit may have an input for a current value, which, however, is output in particular by switching elements of the power circuit (rather than by a dedicated current sensor as described here) (and may therefore be less accurate). The current signals used by the driver circuit and the control unit therefore differ, in particular, with regard to their source (and possibly their accuracy).

[0012] The higher-level control unit is preferably configured to transmit a pulse wave control signal or a clocked control signal to the driver circuit. The control unit is capable of generating a multi-phase inverter control signal, i.e. a clocked control signal (suitable for generating a rotating field in an electrical machine). The control unit preferably comprises a control system for an electrical machine, in particular a space vector control system, which generates a suitable multi-phase clocked signal for generating a rotating field on the basis of target variables such as speed and torque. The clocked control signal of the control unit is output by the control unit. The control signal is output in error-free operating mode (maximum current within permissible operating parameter limits). In these embodiments, the control unit is configured to provide the current value and the control signal for the driver circuit orto transmit it to them. A pulse-wave control signal or clocked control signal is a switching signal (pulsed, clocked, or at least temporarily ON or OFF) that indicates the desired switching state of a power switch connected downstream of the driver circuit.

[0013] Other embodiments provide a control unit configured to transmit the current value to the driver circuit (and which, as described, is directly or indirectly connected to a current sensor and / or a current calculation unit) and additionally provide a control signal generation unit configured to transmit or generate a pulse wave control signal to the driver circuit. In this case, the control unit outputs only the current value, but not the control signal for the power circuit / power switch, to the driver circuit, while the control signal generation unit outputs the pulse wave control signal to the driver circuit, not the current value. The control signal generation unit and the control unit each have outputs that are connected to the respective inputs (logical or physical) of the driver circuit for data transmission.

[0014] The shutdown signal and the control signal are transmitted from the control unit to the driver circuit. The two signals can be transmitted over the same line or over separate lines. The two signals can be transmitted over the same physical channel or over different physical channels.

[0015] Preferably, both signals are transmitted via the same physical channel, for example via the same line. The signal output of the control unit can be connected to a signal input of the driver circuit via a physical channel (for example an electrical line). The two signals can be transmitted using a multiplexing method. The joint signal resulting from multiplexing is transmitted via one line. The shutdown signal can be modulated onto the unmodulated control signal (i.e. clocked inverter control signal). The modulation frequency used is outside the frequency range of the control signal occurring during operation, for example above the maximum clock frequency of the control signal (during fault-free operation). The control signal can remain unmodulated; the shutdown signal can be modulated, or vice versa. Both signals can also be modulated.The shutdown signal (and / or the control signal) can be encoded or modified by frequency division multiplexing, code division multiplexing, time division multiplexing (e.g., in specific time windows if this does not change the effect of the control signal), or by other multiplexing methods or methods for multiple access (sharing the physical channel). In particular, a pulse or edge in a control signal at a time at which the control signal exhibits no level change during error-free operation can represent the shutdown signal, corresponding to time division multiplexing of the shutdown signal. Furthermore, a pulse packet in a control signal with a frequency that does not occur in the control signal during error-free operation can represent the shutdown signal, corresponding to frequency division multiplexing of the shutdown signal.

[0016] As mentioned, it can be provided that only the shutdown signal, but not the control signal, is modified by multiplexing in order to be combined with the control signal to form a common signal. This means that no demultiplexing is required for the control signal (only for the shutdown signal). The driver circuit can have a corresponding demultiplexing device for the common signal, or a demultiplexing circuit can be provided that is connected upstream of the driver circuit. The multiplexing results in different logical channels or at least one logical channel (for the shutdown signal) that shares the physical channel for transmitting the control signal with the control signal. The two signals can thus be transmitted via different (logical / physical) channels. The control signal is, for example, a multi-phase clock signal (generated by pulse width modulation).

[0017] The shutdown signal can be a binary signal (or represent binary information) that indicates whether the current value lies within the interval or not. The absence of the shutdown signal can indicate that the current value is not within the interval, and in particular that the current value lies below the interval. The shutdown signal can also indicate the current value that lies within the interval, in particular in two or more current levels. This allows for different edge steepnesses or differently reduced edge steepnesses to be provided for different current values ​​that lie within the interval.

[0018] The reduced edge steepness is preferably implemented in the driver circuit (e.g., by designing a circuit or by storing a reduced edge steepness value there). Alternatively, a current value-edge steepness assignment is provided in the driver circuit. In this assignment, different current values ​​within the interval are assigned different edge steepnesses. The assignment is stored, in particular, as a lookup table, for example, in a memory of the driver circuit. Alternatively, the desired edge steepness can also be transmitted as a signal from the control circuit to the driver circuit, either as a standalone (modulated / multiplexed) signal or as part of the shutdown signal. In this case, the control circuit can have a reduced edge steepness (e.g., as a stored value) or can have an assignment as described above for the driver circuit.

[0019] The edge steepness used by the driver circuit due to the shutdown signal is reduced compared to the steepness of an edge that occurs in a pulse-width modulation signal generated by the driver circuit at a current value below the interval. The edge steepness associated with the shutdown signal is smaller than the edge steepness applied by the driver circuit due to the control signal. The edge steepness associated with the shutdown signal is smaller than the edge steepness generated by the driver circuit in the fault-free state (maximum). The reduced edge results in a slower current change, which does not lead to an overvoltage even at high current values. The reduced edge steepness can depend on the current value, whereby the higher the current value, the smaller the edge steepness is provided.

[0020] The driver circuit can also be configured to perform an emergency shutdown if the driver circuit detects that an overcurrent limit has been exceeded (in the sense of a hard short circuit). The overcurrent limit is greater than the upper limit of the interval. The driver circuit is sufficiently sensitive to detect that the overcurrent limit has been exceeded. The driver circuit can be connected to a power circuit or can be connected to receive a current value from it or to receive the signal that an overcurrent limit has been exceeded. If the latter signal is received by the driver circuit, it executes the emergency shutdown. In the event of an emergency shutdown, the driver circuit opens the switching elements of the power circuit by controlling them.

[0021] An inverter can comprise the inverter control circuit (driver circuit and control circuit) and the power circuit, as well as, if appropriate, a current sensor as described herein. An electric drive can comprise, in addition to the inverter, an electric machine connected to the inverter, in particular to its phase terminals or AC side. A current sensor can be located (functionally) at the phase terminals or (functionally) on the inverter's DC supply lines.

[0022] The power circuit can be a multi-phase full-bridge circuit, in particular a BnC bridge, where n is twice the number of phases (of the electric machine). The power circuit is in particular three-phase or six-phase. This also applies to the driver circuit.

[0023] The power circuit is designed in particular for converting power outputs of at least 50 kW. The inverter is in particular a traction inverter of a vehicle. The traction inverter is preferably part of an electric traction drive of a vehicle. The electric machine is preferably provided in the traction drive of a vehicle (as a traction drive). An electric traction drive of a vehicle can be provided that comprises the inverter and the electric machine (as a traction drive of a vehicle).

[0024] The inverter control circuit can be used to carry out a method for switching off a power switch (in particular a power circuit). A method for switching off a power switch (for example in an inverter) provides that the power switch is controlled by a driver circuit, in particular by means of a clocked signal (during fault-free operation). The driver circuit is controlled by a control circuit. The power switch is controlled by the control circuit via the driver circuit. Upon receiving a current value that lies within a predetermined interval, the control circuit controls the driver circuit to set a permanent or temporary OFF state. Furthermore, the driver circuit is controlled to execute the transition to the OFF signal with a reduced edge steepness. Several power switches can be grouped as a power circuit (e.g. inverter).The method is preferably performed for the circuit breakers of the power circuit. If the method is performed for several circuit breakers arranged in phases, the current value per phase is determined, and the edge steepness is determined (if the current value is too high) accordingly for this phase or for the relevant (closed, i.e., to be opened) circuit breaker. The method is configured to execute steps according to the functional purposes of the inverter control device or to execute steps defined based on the characteristics of the inverter control device.

[0025] The current value used in the method particularly represents a current flowing in a power path, such as a phase, of the power circuit, flowing in the power switch of the power circuit, or flowing to the power circuit (e.g., as a supply signal). The current value preferably represents the current flowing at phase connections or on an AC side or a DC side of the power circuit. The power circuit is preferably an inverter.

[0026] The slew rate that occurs or is used at a current value within the interval is lower than the slew rate of a pulse wave control signal with which the driver circuit controls the power circuit in a drive state (or fault-free state) of the inverter. If the current value is within the interval, then a fault exists (overcurrent, "weak" short circuit), and the inverter is not in fault-free operation. However, within the interval, the inverter is not in an emergency shutdown state, which would result from a "hard" short circuit. In the latter state, the inverter is preferably switched off (permanently) with an unreduced slew rate.

[0027] It can be provided that, for current values ​​within the interval, the edge steepness decreases with the current value (continuously or abruptly). Furthermore, different edge steepnesses can be provided for various other operating parameters. The operating parameters can be: semiconductor temperature of the circuit breaker, previous service life of the circuit breaker, intermediate circuit voltage supplied to a power circuit in which the circuit breaker is provided, and phase current during previous operation below the predetermined interval. Different edge steepnesses can be used for different values ​​of these parameters or for different value combinations (pairs, ...) of two or more of these parameters. The driver circuit can have an input for receiving the at least one other operating parameter.In the assignment described here, different current values ​​within the interval are assigned different edge steepnesses. Value tuples can be provided that, in addition to the different current values, have different values ​​of at least one of the specified operating parameters. In the assignment, these value tuples are assigned different edge steepnesses. The values ​​and the assigned edge steepnesses are configured to limit overshoots occurring during switching (with the assigned edge steepness) according to a predefined overshoot limit (absolute value or relative value related to the voltage difference to be overcome during switching) that must not be exceeded.

[0028] In embodiments of the method, the control circuit controls the driver circuit by means of a shutdown signal to set the permanent OFF state. The shutdown signal and the pulse wave control signal are transmitted from the control circuit to the driver circuit via the same physical channel or via different physical channels. This transmission has already been described with reference to the device, in particular the modulation and multiplexing methods.

[0029] The Fig. 1 serves to explain embodiments using an exemplary vehicle drive.

[0030] The vehicle drive FA has a driver circuit T that controls a power circuit LS via gate signals GS. Both circuits T and LS are part of an inverter INV. In alternative embodiments, the inverter INV' also has the control circuit MC, which controls the driver circuit T via the signals PS and IS.

[0031] In the illustrated embodiment, the power circuit comprises a plurality of MOSFETs as transistors or switching elements, so that the gate signals of the driver circuit control the control inputs or gates of the power circuit. A purely schematic representation of a three-phase bridge circuit BS within the power circuit LS is shown. The DC side is connected to HV+ and HV-, and the AC side is connected to the three phase outputs to which the electric machine can be connected. Symbolically, it is shown that a (multi-part or multi-phase) sensor S measures the individual phase currents, i.e., the currents of the half-bridges formed by the power switches of the bridge circuit BS.Due to the serial connection of two circuit breakers in each half-bridge / phase, the AC-side current is measured to detect the current in the respective power path. This current is delivered at an output to which the electric machine EM can be connected. The symbolically represented three-part sensor S is configured to measure the currents I delivered by the phases.

[0032] The power circuit LS shown as an example is designed as a three-phase inverter with a three-phase bridge circuit BS comprising three half-bridges whose ends are connected to each other (and to HV+, HV-) in a two-pole manner, as shown. The connection points in the half-bridges form the phase connections or AC voltage side of the power circuit, at which the individual currents I are measured. The current values ​​representing the strength (amplitude) of these currents I are also designated by the reference symbol I (due to their identical content). The current values ​​I are output to the control circuit MC, as shown (individually for each phase of the power circuit LS). The power switches of the power circuit LS are preferably transistors, in particular MOSFETs or IGBTs. The transistors of the power circuit LS are controlled by gate signals (generally: control signals).

[0033] The gate signals GS, or generally the signals by which the driver circuit T controls the power circuit LS, are clocked signals that have one of two different levels. The gate signals GS indicate whether the switching elements of the power circuit should be open or closed. Furthermore, the signals emitted by the driver circuit T define the edge steepness with which the transition between the two levels takes place. The driver circuit can be implemented using driver ASICs. The control circuit is preferably a microcontroller (or a microprocessor) in which, for example, the evaluation of the current value or the generation of the shutdown signal is at least partially implemented as software code executing there.

[0034] The aim is to specifically reduce the edge steepness of the transition to the OFF signal. This is to reduce overvoltages, for example in the HV+ and HV- supply lines that lead from a high-voltage on-board network section HV to the power circuit LS. Particularly at high currents, overvoltages can occur during switching, particularly during the transition to the OFF signal. These overvoltages can be suppressed or reduced by specifically reducing the edge steepness, as mentioned above. Since a low edge steepness otherwise leads to high losses during normal clocked operation of the power circuit, the edge steepness is only specifically reduced when a current value is received that lies within a predetermined interval. This interval is usually above the maximum operating current of the drive.

[0035] For normal, clocked operation, a pulse wave control signal (or, in general, a clocked signal) PS is output from the control circuit MC, which is higher-level than the driver circuit T, to the driver circuit T. If, as previously mentioned, the driver circuit T is caused by the control circuit MC to enter a permanent off state (i.e., current value I is within the predetermined interval), then a shutdown signal IS is transmitted from the control circuit MC to the driver circuit.

[0036] The shutdown signal IS is intended to be transmitted over the same line or the same physical channel as the clocked signal PS is transmitted during fault-free operation. In order to differentiate the signals from one another, at least the shutdown signal IS is modulated or designed in such a way that it does not influence the clocked signal PS or its effect. This prevents the shutdown signal from being mistakenly interpreted as a clocked signal PS and executed accordingly. While the clocked signal PS indicates when switching edges should be executed (during normal operation), the shutdown signal either indicates that the edge steepness should be reduced, or that a current value has occurred or is occurring that lies within the specified interval, or indicates a reduced edge steepness with which the driver circuit controls the transition to the OFF state.

[0037] To measure the current, a (multi-part) sensor S is provided, by means of which the current value I can be measured. The sensor S measures the individual currents at the phase connections or at the AC side of the power circuit LS (in Fig. 1 as a three-phase inverter). Here, the sensor S can have a measuring device for each phase (as shown), can have a measuring device for only some of the phases and a calculation device for the remaining phases, or can have a determination device that determines the phase currents (approximately or model-based) using other procedures, such as by calculation based on operating parameters (voltage between HV+, HV-, duty cycles, modulation type, drive model and / or control parameters, such as target torque, target speed, etc.). Ultimately, "sensor" is understood to be a signal source for the individual phase currents (current values), whereby these are measured or determined in another way. In other embodiments, the sensor can also display or measure the current on the DC voltage side HV+, HV- of the power circuit LS.

[0038] In the illustrated embodiment, the current value I is transmitted (by the sensor S) to the control circuit MC, with the corresponding current value I being transmitted for each phase. This circuit MC evaluates the current value I to determine whether it lies within the specified interval or not. If the current value I lies within the interval, the switch-off signal IS is transmitted from the control circuit MC to the driver circuit T. The driver circuit T then transmits a gate signal GS to the power circuit LS, leading to the OFF state. This gate signal does not have the (high) edge steepness of the clocked signals generated according to the signal PS, but rather a reduced edge steepness.

[0039] The reduced edge steepness can be implemented in the driver circuit, for example, by providing a memory there that defines the edge steepness, or by generating the gate signal GS by a circuit (e.g., in the driver circuit) that, due to its design, generates a lower edge steepness. In specific embodiments, a current value-edge steepness assignment IFZ is provided in the driver circuit T. Different current values ​​or current value ranges (all within the interval) can be provided there, to which corresponding (reduced) edge steepnesses are assigned. For example, the interval can be divided into several current value ranges, with each current value range being assigned its own (reduced) edge steepness.A first current value range or current value that is greater than a second current value range or current value is associated with a lower edge steepness than the second current value range or current value. In other words, the greater the current value, the more the edge steepness is reduced. Instead of the edge steepness itself, a value can be stored that influences the edge steepness. For example, the reduction in the edge steepness, an edge time (increased according to the edge steepness reduction), or an edge time increase that corresponds to the reduction in the edge steepness or the reduced edge steepness can be stored. For this purpose, information that reflects the level of the current value (e.g., stepped) should be transmitted as the shutdown signal IS, or such information should be transmitted together with a shutdown signal. This allows the driver circuit to provide a reduced edge steepness depending on the current value I.

[0040] In preferred cases, only a reduced edge steepness is stored in the driver circuit, or a value that defines the reduction or the edge steepness itself, so that no mapping is necessary and, upon the occurrence of a (binary) shutdown signal IS, the driver T can immediately execute the transition to the OFF state with a reduced edge steepness. The OFF state applies to all power semiconductor switching elements in the power circuit.

[0041] The sensor S can, for example, in embodiments not shown, detect at least one current I of the DC voltage supply HV+, HV-. As in Fig. As shown in Figure 1, at least one sensor element can be provided at a phase connection to measure a phase current. The sensor can therefore also be configured to detect at least one current between the power circuit LS and the electrical machine EM.

[0042] If multiple sensors are provided, or if the sensor is multi-part (i.e., configured with multiple current sensor elements) as shown, then preferably all detected current values ​​are also determined, and the largest of these values ​​(alternatively: the median or the average of the values) can be processed as shown here. Instead of transmitting all individual current values ​​of the phases to the control circuit MC, only one current value I can be transmitted, which results from the individual current values ​​of the phases (by averaging, median calculation, or maximum calculation).

[0043] In the Fig. 1, the solid line indicates that the control circuit MC transmits the current value IS and the pulse wave control signal PS. The control circuit MC thus provides the current value IS and the pulse wave control signal PS to the driver circuit.

[0044] A different embodiment is shown in dashed lines: here, the control circuit MC is not used to supply the driver circuit T with the current value IS and the pulse wave control signal PS, but serves to supply the driver circuit T with the current value IS', while the pulse wave control signal PS is provided by a control signal generation unit SE and transmitted to the driver circuit T. The control signal generation unit SE can be an integrated circuit designed for motor control (such as a microprocessor), and the control circuit MC can be a current monitoring circuit or a control unit superior to or secondary to the motor control, such as a drive train control unit, which is in particular superior to the inverter or a motor control.

Claims

[1] Inverter control device with a driver circuit (T) and a control circuit (MC) superordinate to the driver circuit (T), wherein the control circuit (MC) is set up to receive at least one current value and, if the current value is within a predetermined interval, to transmit to the driver circuit (T) a switch-off signal (IS) which causes the driver circuit (T) to enter a permanent OFF state and which further causes the driver circuit (T) to carry out the transition to the OFF state with a reduced edge steepness. [2] Inverter control device according to claim 1, wherein the higher-level control unit (MC) is connected to a current sensor (S) which is arranged to measure or determine a current flowing in the power switch which is controlled by the driver circuit (T) and which defines the current value. [3] Inverter control device according to claim 1 or 2, wherein the higher-level control unit (MC) is arranged to transmit a pulse wave control signal (PS) to the driver circuit (T). [4] Inverter control device according to claim 3, wherein the shutdown signal (IS) and the pulse wave drive signal (PS) are transmitted via the same physical channel or wherein the shutdown signal (IS) and the pulse wave drive signal (PS) are transmitted via different physical channels. [5] Inverter control device according to claim 1 or 2, wherein the drive unit (MC) is arranged to transmit the current value (IS') to the driver circuit (T), wherein the inverter control device further comprises a control signal generation unit (SE) which is arranged to transmit a pulse wave drive signal (PS') to the driver circuit (T). [6] Inverter control device according to one of the preceding claims, wherein the reduced edge steepness is reduced compared to a steepness of an edge occurring in a pulse width modulation signal generated by the driver circuit (T) at a current value below the interval. [7] Inverter control device according to one of the preceding claims, wherein the reduced edge steepness is provided in the driver circuit (T), or a current value edge steepness assignment (IFZ) is provided in the driver circuit (T), in which different current values ​​lying in the interval are assigned different edge steepnesses. [8] Inverter control device according to one of the preceding claims, wherein the driver circuit (T) is arranged to perform an emergency shutdown when the driver circuit (T) detects an exceeding of an overcurrent limit, the overcurrent limit being greater than the upper limit of the interval. [9] Method for switching off a power switch (LS) of an inverter (INV), wherein the power switch is controlled by a driver circuit (T), and the driver circuit (T) is controlled by a control circuit (MC), wherein, when a current value is present which lies within a predetermined interval, the driver circuit (T) sets a permanent or temporary OFF state and carries out the transition to the OFF state with a reduced edge steepness. [10] Method according to claim 9, wherein the edge steepness is less than the edge steepness of a pulse wave drive signal (PS) with which the driver circuit (T) drives the power switch (LS) in a drive state of the inverter. [11] Method according to claim 10, wherein the control circuit (MC) controls the driver circuit (T) by means of a switch-off signal (IS) to set the permanent or temporary OFF state, wherein the switch-off signal (IS) and the pulse wave control signal (PS) are transmitted from the control circuit (MC) to the driver circuit (T) via the same physical channel or via different physical channels. [12] Method according to claim 9, wherein the control circuit (MC) transmits the current value (IS) and a pulse wave control signal (PS) to the driver circuit (T) or the control circuit (MC) transmits the current value (IS') to the driver circuit (T) and a control signal generation unit (SE) transmits a pulse wave control signal (PS) to the driver circuit (T). [13] Method according to one of claims 9-12, wherein different edge steepnesses are used for different current values ​​and wherein furthermore the edge steepness is dependent on at least one parameter selected from: - semiconductor temperature of the circuit breaker, - previous service life of the circuit breaker, - intermediate circuit voltage supplied to a power circuit in which the circuit breaker is provided, and - Phase current during previous operation below the predetermined interval.

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