Increasing the switching level in the event of a reduced inverter supply voltage

Abstract

The invention describes an inverter control device having a driver circuit (T) and an actuation circuit (MC), which is superordinate to the driver circuit (T). The actuation circuit (MC) is designed to receive a supply voltage value (U) and to transmit to the driver circuit (T) a supply signal (VS) characterizing the supply voltage value (U). The driver circuit (T) is designed to output a clocked actuation signal (GS), the high level of which increases as the supply voltage value (U) decreases. The invention also describes a corresponding electric vehicle traction inverter, a driver circuit, and a corresponding method.

Description

[0001] Description

[0002] Increasing the switching level when the supply voltage of an inverter is reduced

[0003] Electric vehicles with electric traction drive have power electronics and a high-performance traction battery. The range of electric vehicles is largely determined by the capacity of the traction battery that supplies the power electronics, as well as by the efficiency of the power electronics' conversion of the current provided by the traction battery. To achieve high efficiency, high supply voltages are used to supply the power electronics. It is known to increase the voltage of the traction battery using a DC-DC converter to provide the power electronics with a higher supply voltage.

[0004] It is also known that power semiconductors with high edge steepness reduce power dissipation by shortening operating points in the lossy linear operating range. Therefore, fast-switching MOSFETs with a wide band gap and thus high electron mobility, such as SiC MOSFETs or GaN MOSFETs, are increasingly being used.

[0005] It is an object of the invention to show a possibility by which the efficiency of electric traction vehicle drives can be further increased in a simple and safe manner.

[0006] 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.

[0007] It has been recognized that a clocked control signal of a driver circuit at high high levels or turn-on levels enables fast switching of MOSFETs (or IGBTs) in a power circuit, with losses decreasing with increasing gate voltage due to the resulting decrease in forward voltage. However, high high levels are a hindrance to short-circuit shutdown because at high high levels a larger amount of charge must be withdrawn from the gates in order to achieve the OFF state of the MOSFET (or IGBT) desired for short-circuit shutdown, and the short-circuit current is higher than at a lower high level. Setting the high level to a fixed value must therefore be based on the feasibility of an emergency shutdown in the most difficult case, i.e. when the power circuit is supplied with a maximum permissible supply voltage.In particular, it was recognized that, especially at reduced supply voltages, for example when the traction battery is at a low charge level, the high level can be increased in order to achieve a low forward voltage in the power path of the semiconductor switch, which leads to increased efficiency without deteriorating the switching properties in the event of an emergency shutdown (compared to a non-increased high level at non-reduced supply voltages).

[0008] It was recognized that the improved manageability of emergency shutdowns, which results from reduced supply voltages, can be used to increase the high level and thus to increase efficiency. The improved manageability of emergency shutdowns, which results from reduced supply voltages, is therefore used to increase efficiency by increasing the high level for this case (compared to the high level with a non-reduced / higher supply voltage). This results in increased efficiency, particularly for operating conditions with a reduced supply voltage (compared to the nominal voltage). The increased efficiency results from the forward voltage, which decreases with increasing gate voltage (for a given switch current). The lower the forward voltage, the lower the power dissipation (for a given switch current).

[0009] An inverter control device with a driver circuit and a control circuit superordinate to the driver circuit is described. The control circuit controls the driver circuit, for example, with clocked or pulse-width modulated signals. This applies in particular to normal operation of the inverter control device. The control circuit is configured to receive a supply voltage value. The control circuit has an input for receiving the supply voltage value. The control circuit is configured to determine the (current) supply voltage value. The control circuit is further configured to output a supply signal to the driver circuit, which directly reproduces the supply voltage value itself or otherwise characterizes the supply voltage value. The driver circuit is configured to output a clocked control signal (analog control signal). This analog control signal has a high level, i.e.a level that puts the power switching elements controlled thereby into an ON state. The inverter control device is configured to set the high level depending on the supply voltage value. A (relatively) lower supply voltage value results in a high level that is greater than a high level provided at a (relatively) higher supply voltage value. As a result, when the supply voltage drops, which reduces the problem of rapid emergency shutdown, a higher high level is provided than at the nominal supply voltage. With a reduced supply voltage, a higher high level results (than at the nominal supply voltage), which leads to a lower forward voltage than a non-increased high level. The lower forward voltage results in lower loss and increased efficiency. A pulse-width modulated or generally pulsed control signal is referred to as a clocked control signal.In particular, a clocked control signal is a signal with discrete levels, in particular with two or three different levels, for example alternating high levels (switch-on levels) and low levels (switch-off levels).

[0010] The high level is selected depending on the supply voltage level (represented by the supply voltage value), with the high level increasing (discretely or continuously) as the supply voltage decreases. The supply voltage level serves as the influencing parameter; the high level is changed accordingly. In addition to this influencing parameter, the semiconductor temperature, the aging state, and the current to be supplied (phase current of the inverter) can also be taken into account. Thus, in addition to the dependency on the supply voltage, a dependency on at least one of these parameters can be provided. The control circuit or the driver circuit can thus be configured to receive a semiconductor temperature value, an aging state value, and a phase current value, in addition to the supply voltage value.The high level can be configured to change (in addition to increasing with reduced supply voltage) with increasing semiconductor temperature, increasing aging, and / or increasing phase current. These parameters refer to a power circuit controlled by the driver circuit. With increasing semiconductor temperature, the high level can increase (or decrease, if applicable). With increasing aging, the high level can increase (or decrease, if applicable). With increasing phase current (average current magnitude or peak current), the high level can decrease (or increase, if applicable).

[0011] The higher-level control unit can be connected to a voltage sensor. This connection transmits signals and can be provided directly or via (signal-processing) components. The voltage sensor is configured to detect a supply voltage of a power circuit that is controlled by the driver circuit, wherein the supply voltage defines the supply voltage value. The voltage sensor has the function of detecting the level of the supply voltage. For this purpose, it can be configured to measure this voltage or can be configured to receive a value that represents the level of the voltage, for example from another control component or from an analog / digital converter. In particular, a voltage divider can be provided so that the input of the voltage sensor does not have to be loaded with a high voltage.The detected DC voltage is the voltage of a high-voltage vehicle electrical system or the DC side of a power circuit (which is controlled by the driver circuit).

[0012] Further embodiments provide for the driver circuit to be connected to a voltage sensor. This connection transmits signals and can be provided directly or via (signal-processing) components. In particular, it is provided for the driver circuit to directly receive the voltage measured by the voltage sensor. In addition, the higher-level control unit can also be connected to the voltage sensor in order to receive this voltage. If the control unit only has the task of transmitting the supply voltage value to the driver circuit, then the control unit can be implemented, for example, by an analog-to-digital converter or by a communication device for transmitting the voltage value to the driver circuit. The control unit can then be designed not to provide any further function besides transmitting the supply voltage value that would be required for the operation of the driver circuit.

[0013] As mentioned, the connection can be provided via signal-processing components. A data processing unit can be provided, such as a monitoring device for a rechargeable battery or an on-board electrical system, which receives the voltage measured by the voltage sensor (or a signal representing this voltage, such as a supply voltage value as described herein). The data processing unit is connected downstream of the voltage sensor. The voltage sensor is preferably configured to detect the supply voltage of a power circuit controlled by the driver circuit. The supply voltage defines the supply voltage value. The voltage sensor can be configured to detect the supply voltage of an on-board electrical system or a rechargeable battery that supplies the power circuit.The voltage sensor can thus transmit a signal directly to the driver circuit and / or to the higher-level control unit, whereby the signal indicates the supply voltage, or the signal can originate from a monitoring device. The monitoring device or the voltage sensor is the source of the signal that indicates the voltage. The monitoring device can itself be connected downstream of a voltage sensor (and thus serves to forward a signal that indicates the voltage). In addition to the function of emitting a signal that indicates the supply voltage, the monitoring device can have other functions, such as overvoltage detection, fault current detection, torque and / or speed control, fault detection for errors in the power supply, and the like.

[0014] The voltage sensor is configured to detect the supply voltage of a power circuit controlled by the driver circuit. Particularly in the case of a (controlled) three-phase bridge as the power circuit, the control unit is configured to detect the DC supply voltage of the three-phase bridge. The voltage on the DC side of the three-phase bridge corresponds to the supply voltage. The supply voltage of the power circuit defines the supply voltage value. In particular, the supply voltage is the voltage of a traction battery; an associated battery monitoring unit can be connected to the control unit for signal transmission in order to transmit the supply voltage value. The respective data input or battery monitoring unit forms (functionally) the voltage sensor.

[0015] 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 pulse wave control signal (suitable for generating a rotating field in an electrical machine). The control unit preferably comprises a control of an electrical machine, in particular a space vector control, which generates a suitable multi-phase clocked signal for generating a rotating field based on target variables such as speed and torque. The pulse wave control signal (short: pulse pattern or pulse pattern signal) of the control unit is output by the control unit. The driver circuit is configured to generate the analog control signal with a high level that increases as the supply voltage value decreases.The pulse pattern sent to the driver circuit represents the switching times and thus defines the occurrence times of the edges.

[0016] The pulse pattern is thus a binary (or ternary) pattern that represents discrete states (high / low or high / 0 / low). However, the pulse pattern does not represent the specific voltage values ​​of individual levels (high / low or high / 0 / low), i.e., the voltage levels to which the individual binary (or ternary) states of the pulse wave control signal are assigned. The level depends on the supply voltage value, so that, for example, the supply voltage value is transmitted to the driver circuit along with the pulse pattern. The driver circuit is able to provide the timing of switching edges in the analog control signal according to the pulse pattern and is able to provide the height of the high level depending on the supply voltage value. This dependency means that for (at least two) different supply voltage values, different high levels are provided in the control signal.Since the high level of the analog control signal varies with different supply voltage values, different levels (high level) result for the same level state (high). Due to this varying high level, this control signal is referred to as an analog control signal.

[0017] A first supply voltage value, which is below a second supply voltage value, is linked to a high level that is greater than the high level linked to the second supply voltage value. A dependency or mapping can be provided which assigns different high level heights to different supply voltage values ​​and which is decreasing at least in sections. This mapping or assignment can be continuous or discrete. The mapping has at least two assignments: a first supply voltage value assigned to a first high level, and a second supply voltage value assigned to a second high level, wherein the first supply voltage value is less than the second supply voltage value and thus the first high level is greater (can be greater without disadvantages in the event of an emergency shutdown) than the second high level.

[0018] The increase in the high level is preferably implemented in the driver circuit (e.g., by designing a circuit or by storing an increased high level there). Alternatively, a supply voltage high level assignment is provided in the driver circuit. In this assignment, different supply voltages are assigned different high level values. The assignment of the high level, which increases with decreasing supply voltage, is stored, in particular, as a lookup table, for example, in a memory of the driver circuit or in the control circuit. The supply voltage referred to here can reflect the supply voltage value unchanged, or can characterize it, for example, as a deviation from a standard value.The control circuit is preferably configured to transmit a supply signal to the driver circuit, which represents the supply voltage value as an absolute value (in particular with discrete values). The driver circuit thus receives the level of the supply voltage itself. Alternatively, the driver circuit can receive a supply signal that represents the deviation of the supply voltage value from a nominal value. In addition, the supply signal can be transmitted to the driver circuit as the high level dependent on the level of the supply voltage value. In the latter case, the level of the supply voltage has already been mapped to a quantity that characterizes the high level, with this mapping being provided in the driver circuit or in the higher-level control circuit. It is also possible for the control circuit to receive the level of the supply voltage itself and convert it into a deviation from a nominal value.In this case, the control circuit is preferably configured to transmit the deviation to the driver circuit as a supply voltage value. Thus, the level of the supply voltage itself can be transmitted to the driver circuit as a supply signal, or a signal (preprocessed, for example, in the control circuit) indicating the reduction in the supply voltage compared to a standard or maximum value, or a value can be transmitted that represents the high level of the analog control signal, which is already increased according to the supply voltage.

[0019] Preferably, the pulse pattern signal (pulse wave control signal) is transmitted together (in particular with a temporal overlap) with the supply signal. These signals are transmitted from the control circuit to the driver circuit. The supply signal represents the supply voltage value. The pulse pattern signal and the supply signal are transmitted in particular via the same physical channel. There is one physical channel, for example in the form of a signal line, between the control circuit and the driver circuit. Alternatively, the pulse pattern signal and the supply signal are transmitted via different physical channels. There may be several physical channels, for example in several signal lines, between the control circuit and the driver circuit. Preferably, within the scope of the control device or within the scope of the method described here, 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 (e.g., an electrical line). The two signals can be transmitted using a multiplexing process. The combined signal resulting from multiplexing is transmitted via one line. The supply signal can be modulated onto the unmodulated pulse pattern signal, particularly as a digital representation of the value. The modulation frequency used is outside the frequency range of the pulse pattern signal occurring during operation, for example, above the maximum clock frequency of the pulse pattern signal (during fault-free operation). The pulse pattern signal can remain unmodulated or unprocessed; the supply signal can be modulated, or vice versa. Both signals can also be modulated.The pulse pattern signal (and / or the supply signal) can be encoded or modified by frequency division multiplexing, code division multiplexing, time division multiplexing (e.g., in specific time slots, provided this does not alter the effect of the pulse pattern signal), or by other multiplexing or multiple access methods (sharing the physical channel). In particular, a pulse or pulse sequence in a pulse pattern signal at a time point at which the pulse pattern signal exhibits no level change during error-free operation can represent the supply signal, corresponding to time division multiplexing of the supply signal. Furthermore, a pulse packet in a pulse pattern signal with a frequency that does not occur in the pulse pattern signal during error-free operation can represent the supply signal, corresponding to frequency division multiplexing of the pulse pattern signal.

[0020] As mentioned, it can be provided that only the supply signal, but not the pulse pattern signal, is modified by multiplexing in order to combine the supply signal with the pulse pattern signal to form a common signal. This means that no demultiplexing is required for the pulse pattern signal (only for the supply signal). The driver circuit can have a corresponding demultiplexing device for the common signal, or a demultiplexing circuit can be provided which is connected upstream of the driver circuit. The multiplexing results in different logical channels or at least one logical channel (for the supply signal) which shares the physical channel for transmitting the pulse pattern signal with the pulse pattern signal. The two signals can thus be transmitted via different (logical / physical) channels. The pulse pattern signal is, for example, a multi-phase signal generated by pulse width modulation.The driver circuit generates a signal for controlling power semiconductors, such as a gate signal, from the pulse pattern signal (and the possibly increased high level).

[0021] It can be provided that the change in the high level (compared to a value used at a nominal or maximum supply voltage) at least partially compensates for the higher forward voltage resulting from a lower supply voltage. The forward voltage refers to the element (semiconductor switching element) that is controlled by the clocked control signal. The nominal or maximum supply voltage refers to the voltage applied across the power path of the element (in the open switching state), such as a drain-source voltage or a collector-emitter voltage. The increase in the high level with a decreasing supply voltage value can be designed such that, with a reduced supply voltage and in the event of a short circuit, a short-circuit energy results that is no greater than the short-circuit energy at a nominal supply voltage value.This prevents an increase in the high level at a reduced supply voltage from leading to a more critical short-circuit scenario. In other words, this allows the high level to be increased at a reduced supply voltage without increasing the risk of damage in the event of a short circuit. The inventive increase in the high level does not impair the manageability of a short circuit.

[0022] The short circuit refers to a power circuit that is controlled by the driver circuit or to a power circuit or power component connected to it, such as an on-board power system, a battery, an electrical machine or connecting elements that are connected to the power circuit. The short circuit refers to at least one component that is affected by the short-circuit current, i.e. through which the short-circuit current flows, which results from the short-circuit energy. Increasing the high level when the supply voltage is reduced does not increase the resulting short-circuit energy, because increasing the high level takes the resulting change in the short-circuit current into account. The short-circuit energy can be estimated using the short-circuit current (maximum or averaged over a time window) or using the temperature (increase) that results from the short-circuit current in the time window in which the current flows.The short-circuit energy refers specifically to the energy that is converted into heat due to the short circuit in the power circuit controlled by the control device or in components provided within the power path in which the power circuit is located. The short-circuit energy can be considered as an energy value or, when related to a time window (e.g., corresponding to the time window of occurrence of the short circuit), as an energy related to a time window in the sense of a power.

[0023] The control circuit is preferably a microcontroller (or a microprocessor) in which, for example, the generation of the shutdown signal is implemented at least partially as software code running there, possibly a multiplexing function, and / or processing of the supply voltage for transmission to the driver circuit. The control circuit is designed to control an electrical machine and, in particular, implements vector control. The control circuit can transmit a pulse pattern signal resulting from the control to the driver circuit.

[0024] An electric vehicle traction inverter can be equipped with a power circuit and an inverter control device, as described herein. The driver circuit is connected to the power circuit for driving purposes. The power circuit is connected to a supply voltage source. The supply voltage value indicates the voltage of the supply voltage source. 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. The power circuit is in particular designed to convert 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, which includes the inverter and the electric machine (as a traction drive of a vehicle). The power circuit has an AC voltage side (opposite the DC voltage side, to which the supply voltage is applied), which is connected in phases to the electric machine.

[0025] The inverter control circuit can be used to carry out a method for controlling a power circuit of an inverter. A power circuit of the inverter is controlled by a driver circuit. The driver circuit is controlled by a control circuit. The control circuit transmits a supply voltage value to the driver circuit. The driver circuit controls the power circuit with a clocked control signal (gate signal). The high level of the control signal increases as the supply voltage value decreases. This increase can be continuous, discontinuous, or sudden, for example in the form of a single jump. The method is designed to carry out steps according to the functional purposes of the inverter control device or to carry out steps that are defined based on the features of the inverter control device. It is provided that the supply voltage value or the supply voltage is mapped to the height of the high level.This can be done in the control circuit or in the driver circuit.

[0026] The control circuit performs closed-loop control of an electrical machine (and is designed to do so). The control circuit preferably controls the electrical machine according to vector control. The control generates the pulse pattern signal or generates the pulse wave control signal. The pulse pattern signal and the supply voltage value are transmitted to the driver circuit, in particular from the control circuit, via the same physical channel or via different physical channels. Modulation or multiplexing can be performed to transmit the pulse pattern signal and the supply voltage value as a common signal. This signal is transmitted to the driver circuit, in particular from the control circuit.It can be provided (in the sense of time division multiplexing) that the supply voltage value is transmitted during pauses in the pulse pattern signal, either as an analog signal, a digital signal (bit sequence), or a frequency-modulated signal. Alternative embodiments provide for a supply monitor, such as a battery management system (BMS), to transmit the supply voltage value to the driver circuit. A modulator, multiplexer, or other signal combiner can be provided to combine the pulse pattern signal of the control circuit with the supply voltage value. The thus combined (and separable) signal is transmitted to the driver circuit.

[0027] The inverter control device is preferably used in a traction inverter of an electric vehicle (BEV or hybrid vehicle). The electric vehicle traction inverter is equipped with a power circuit and the inverter control device described here. The power circuit (power module) comprises several controllable half-bridges. The ends of the half-bridges are interconnected and connected to a positive or negative supply potential. The voltage between the supply potentials is measured or recorded in another way (e.g., by forwarding or processing a voltage measurement signal). The voltage corresponds to the supply voltage. The supply voltage value indicates the level of the supply voltage. The ends of the half-bridges are connected to a supply voltage input. This is connected or can be connected to a supply voltage source.The supply voltage source is, in particular, a traction battery, in particular a high-voltage battery. The word component "high-voltage" defines a nominal or operating voltage of more than 60 V, in particular of at least 200 V, 400 V, or 800 V, of the component containing the word component. The power circuit is preferably a high-voltage power circuit. The driver circuit is connected to the power circuit in a driving manner. The power circuit has transistors, in particular MOSFETs or IGBTs. The half-bridges are formed by the transistors. The transistors are high-voltage transistors. The transistors have a control input or a gate connection. The driver circuit is connected to the gate connections of the transistors (the half-bridges) of the power circuit in a driving manner. The supply voltage value specifies, in particular, the voltage across the transistors, preferably the voltage between the ends of the half-bridges.

[0028] The inverter control device or the traction inverter are designed to carry out a method. The method described here relates in particular to the functioning of the inverter control device or the traction inverter. A method for controlling a power circuit of an inverter is proposed, in particular the power circuit of the inverter described here. A power circuit of the inverter, in particular the power circuit described here, is controlled by a driver circuit, in particular the driver circuit described here. The driver circuit is controlled by a control circuit, in particular by the control circuit described here. As described with reference to the control device, the control circuit transmits a supply voltage value (or a supply signal characterizing the supply voltage value) to the driver circuit.The supply voltage value preferably corresponds to the supply voltage value described with reference to the control device. This also applies to the supply signal. The driver circuit controls the power circuit with a clocked control signal, as described herein with reference to the control device. The high levels of the control signal increase with decreasing supply voltage value (stepwise or continuously, or even just in the form of a single step). Different high levels are used for different supply voltage values. A mapping that maps the supply voltage values ​​to different high levels is preferably in the form of a decreasing function.

[0029] A corresponding mapping maps the supply voltage value to the high level. Preferably, the mapping is performed by the driver circuit. In this case, the supply voltage value represents the level of the supply voltage (with continuous or discrete values, in absolute or relative terms as a difference from a standard value). The driver circuit receives these values ​​(preferably from the control circuit or from a battery monitoring system (BMS), a zone controller, or a powertrain control unit (PCU)) and executes the mapping. The mapped levels are used to control the power circuit. The driver circuit controls the power circuit with the high levels thus obtained. Furthermore, the control circuit can perform the mapping and transmit previously mapped values ​​(which can form the supply signal) to the driver circuit.The mapped values ​​are linked (due to the map) to the level of the supply voltage, so that the mapped values ​​characterize the supply voltage. Therefore, the already mapped values ​​are also referred to herein as the supply voltage value. The supply signal can be configured to reflect the mapped values. The control circuit is preferably configured to receive (or retrieve) voltage measurement values ​​obtained by measuring the level of the supply voltage.

[0030] As mentioned, the control circuit carries out a closed-loop control of an electrical machine, for example a vector control. The pulse pattern signal is generated, in particular, by means of a space vector-based control. The control circuit preferably transmits the pulse pattern signal and the supply voltage value (for example in the form of the supply signal) via the same physical channel, or can transmit them to the driver circuit via different physical channels. The control circuit transmits, in particular, the pulse pattern signal and the supply voltage value (for example in the form of the supply signal) via the same electrical line, which represents the common physical channel. The pulse pattern signal and the supply voltage value (or the supply signal) are transmitted as a combined signal, in particular as a multiplex combination of the pulse pattern signal and the supply voltage value.The supply signal, which characterizes the supply voltage value, can be modulated onto the (unmodulated) pulse pattern signal, in particular as a digital image of the value. The modulation frequency used is outside the frequency range of the pulse pattern signal occurring during operation, for example above the maximum clock frequency of the pulse pattern signal (in error-free operation). The modulation or multiplexing is preferably carried out by the control circuit. The driver circuit separates the signals combined in this way, for example by demodulation or demultiplexing. The driver circuit has a device designed for this purpose. The separated signals obtained in this way in the driver circuit are used by the driver circuit to output a control signal, the high and low states of which (in particular their times of occurrence orchange times) are determined by the pulse pattern signal, and whose high level is determined by the supply voltage value or by the supply signal.

[0031] Figure 1 serves to explain embodiments using an exemplary vehicle drive.

[0032] The vehicle drive FA has a driver circuit T that controls a power circuit LS via clocked control signals GS. The control signals GS are, in particular, gate signals with which semiconductor switches of the power circuit LS are controlled. Both circuits T, LS are part of an inverter INV. In the illustrated embodiment, the power circuit comprises a plurality of MOSFETs as transistors or as switching elements, such that the control signals GS of the driver circuit T control the control inputs or gates of the power circuit LS. The control signal GS or, in general, the signals by means of which the driver circuit T controls the power circuit LS are clocked signals that have one of two different levels. The control signals GS indicate whether the switching elements of the power circuit should be open or closed.Furthermore, the signals GS emitted by the driver circuit T define the level with which the power circuit is controlled. In particular, the driver circuit T can be used to define the high level of the control signal GS. The driver circuit can be designed using driver ASICs. The control circuit is preferably a microcontroller (or a microprocessor) in which, for example, the reception of a supply voltage value U or the generation of a pulse pattern signal (or the control for generating the pulse pattern signal) is at least partially implemented as software code running there. The power circuit LS has semiconductor switches that are controlled by the driver circuit T. In particular, the driver circuit outputs gate signals for the semiconductor switches, which are designed as MOSFETs or IGBTs, as the control signal GS. The power circuit LS or its semiconductor switches has orhave power paths whose conduction state is defined by the control signal GS. Depending on the conduction state, a current is generated or not generated in the phases of an electrical machine connected downstream of the power circuit LS due to the voltage U between HV+ and HV-. Due to the control (defined by pulse pattern PS), a rotating field results in the electrical machine EM. The electrical machine is, in particular, a (permanently or separately excited) synchronous machine or an asynchronous machine.

[0033] The voltage U refers to the voltage across the power paths of the power circuit or the semiconductor switches in the open state. The voltage U indicates the drain-source voltage or emitter-collector voltage across the semiconductor switches of the power circuit. If this is lower than a voltage range that exists at a high state of charge (e.g., at least 50%, 60%, 70%, 80%, or 90%), the control signal GS (gate signal) is provided with a higher high level than at a voltage U that exists within this voltage range. The lower limit of the voltage range can be 50%, 60%, 70%, 80%, or 90%) of the nominal voltage of the voltage source HV (a high-voltage battery). The nominal voltage of the voltage source HV can be 800 V, 820 V, or 850 V, whereby the high level is increased if the voltage U is below 700 V, 650 V, 600 V, or 500 V. The increase in the high level is, for example, at least 0.3% or at least 0.5%.The increase in the high level can be up to 1% or 2%, for example.

[0034] The aim is to specifically increase the high level (in short: the high level) when the supply voltage value U is reduced (e.g. compared to a standard value). This is to adapt the control of the power semiconductors within the power circuit LS. This allows a different compromise to be made between the high level (high gate voltage) and short-circuit behavior at reduced supply voltage values ​​U than with supply voltage values ​​U, which essentially correspond to a nominal voltage. At reduced supply voltage values ​​U, a higher high level is used than with a supply voltage in the nominal range in order to enable lower power loss without deteriorating the short-circuit switching behavior. In the event of a short circuit, the power circuit must be transferred to an open state within a short time by controlling it with a low level.The higher the supply voltage, the higher the short-circuit currents, so that especially at high supply voltages the high level used in fault-free operation must be designed in such a way that a low level can be reached quickly. However, as the supply voltage decreases the short-circuit currents naturally decrease, so that the need for rapid, safe shutdown in the event of a short circuit is reduced. Therefore, with a reduced supply voltage a higher high level can be used. Although this increases the shutdown time in the event of a short circuit, this does not lead to greater heat quantities in the power circuit than would be the case with a constant supply voltage. The reason for this is the reduced short-circuit current, which decreases with the supply voltage (together with the need to switch off safely and particularly quickly in the event of a short circuit).The supply voltage decreases - with the same configuration - with decreasing state of charge (SoC) of the high-voltage source HV.

[0035] For normal, clocked operation, a pulse pattern signal PS is output from the control circuit MC, which is higher-level than the driver circuit T, to the driver circuit T. Furthermore, the supply signal VS is transmitted from the control circuit MC to the driver circuit T. The supply signal VS directly or indirectly indicates the level of the supply voltage U (i.e., a supply voltage value), or indicates that the voltage U is below a (specified) voltage threshold.

[0036] The supply signal VS is intended to be transmitted via the same line or the same physical channel as the pulse pattern signal PS. In order to differentiate the signals from one another, at least the supply signal VS is modulated or provided in such a way that it does not influence the pulse pattern signal PS or its effect. This prevents the supply signal VS from being mistakenly interpreted as part of the pulse pattern signal PS and executed accordingly. While the pulse pattern signal PS indicates when a high level and when a low level (during normal operation) is to be delivered as a control signal GS from the driver T to the power circuit, the supply signal VS indicates the level of the supply voltage U (either as an absolute value or as a value relative to a nominal value or already mapped to an increased high level). This makes the driver circuit T of Fig.1 capable of using a high level at a reduced supply voltage value of the voltage U that is higher than a high level used at a non-reduced supply voltage value. A reduced supply voltage value of the voltage U is a value that is reduced by a minimum amount compared to a nominal value. A non-reduced supply voltage value of the voltage U is a value that is not reduced by a minimum amount compared to a nominal value or is reduced by less than the minimum amount. The supply voltage value of the supply voltage U is also referred to as the supply voltage value U due to the identical meaning.

[0037] A sensor S is provided to detect the supply voltage value U (or the relevant supply voltage of the high-voltage source HV). This sensor detects the voltage and transmits the relevant value U to the control circuit MC. Other embodiments provide a monitoring unit (BMS or PCU) configured to process the supply voltage value U. Such a monitoring unit can be connected to the control circuit MC via a signal transmission or directly to the driver circuit T in order to transmit the supply voltage value U itself, a signal that characterizes the value U, or an already mapped value.

[0038] The supply voltage value U is mapped to the high level. A first supply voltage value U, which is lower than a second supply voltage value U, is mapped to a higher high level than the second, higher supply voltage value U. This mapping can be provided in the aforementioned monitoring unit, in the control circuit MC, or, as shown, in the driver circuit T. The driver circuit has a mapping VHZ for this purpose. The mapping VHZ assigns a high level to the supply voltage level U.

[0039] Fig. 1 shows a driver circuit T which is configured to receive a pulse pattern signal PS, in particular from the control circuit MC which is higher-level therefor. Furthermore, the driver circuit T is configured to receive the supply signal VS. This indicates a value of the supply voltage U which is used to supply the power circuit LS. The driver circuit T is connected to the power circuit LS in a controlling manner. The driver circuit T is thus configured to be connected to the power circuit LS in a controlling manner and has a corresponding output for this purpose. The driver circuit T is configured to receive the pulse pattern signal PS and to receive the supply signal VS in that the driver circuit T has a corresponding input. The input is preferably designed for a physical channel (for example a signal line) via which the pulse pattern signal PS and the supply signal VS (as a combined orMultiplex signal) to the driver circuit T. The driver circuit T has a demultiplexer or a demodulator (or another signal separator such as a frequency-dependent filter) to separate the supply signal VS from the pulse pattern signal PS. The mapping VHZ is connected downstream of this. The driver circuit T has the mapping VHZ. The mapping VHZ maps different supply voltage values ​​U to at least two different high levels and implements a falling function. The driver circuit T is configured to generate a (particularly temporally) corresponding clocked control signal GS from the pulse pattern signal PS, wherein the control signal GS has the high level that is determined using the mapping VHZ. The control signal GS corresponds to a gate signal that is output to the gates of the transistors of the power circuit LS.

[0040] This control signal GS has an increased high level when the voltage U is below a limit value. If the voltage U is not below the limit value, the high level is lower. The relevant mapping or assignment between the supply voltage value U and the (possibly increased) high level is implemented in Fig. 1 in the driver circuit T. For example, a memory can be present there that defines the high level (depending on U). In specific embodiments, a supply voltage high level assignment (VHZ) is provided in the driver circuit T. Different voltage values ​​U or voltage value ranges (all within the interval) can be provided there, to which corresponding (possibly increased) high levels are assigned. For example, the interval can be divided into several voltage value ranges, with each voltage value range being assigned its own (possibly increased) high level.A first voltage value range or voltage value that is smaller than a second voltage value range or voltage value is linked to a higher high level than the second voltage value range or voltage value. In other words, the lower the value of the supply voltage U, the more the high level is increased. Instead of the high level itself, a value can be stored that influences the high level (or increases it if the voltage U is reduced). For example, the height of the high level itself or an increase in the high level can be stored. In a simple embodiment, the driver circuit T provides for increasing the high level by a predetermined (in particular constant) value if the voltage U is below a predetermined limit, and not increasing it if this is not the case.In preferred cases, only an increased high level is stored in the driver circuit T, or a value that defines the increase or the high level itself, so that no mapping is necessary, and upon the occurrence of a (binary) signal or state that indicates a reduced supply voltage U, the driver circuit T can immediately apply the thus provided high level to the control signal GS. The high level thus obtained applies to all power semiconductor switching elements in the power circuit LS.

[0041] Figure 1 shows that the sensor S detects a supply voltage U of the DC voltage supply HV+, HV-, which is provided by the high-voltage source HV. The voltage U or the corresponding signal indicates the voltage between the potentials HV+, HV-. The voltage sensor can be a voltage tap, whereby the voltage value U is preferably output by a control or monitoring unit that determines the voltage U (to implement other functions), possibly with its own voltage sensor. The voltage sensor can be provided as a tap at the potentials HV+, HV-, combined with a voltage divider and possibly a downstream comparator or analog / digital converter.

[0042] Further embodiments, which can be seen in Fig. 1, relate to the transmission of the voltage U measured by the sensor S to the driver circuit T. This is shown in dashed lines in Fig. 1. In this case, the driver circuit receives the voltage value of the supply voltage U not via the control unit MC, but from the sensor S. In this case, the driver circuit T has a corresponding input that is connected to the voltage sensor S. Thus, the voltage sensor can be connected directly upstream of the control unit MC or the driver circuit T. The signal source for the control unit MC or for the driver circuit T in these cases is the voltage sensor S.

[0043] Other embodiments, which can be seen in Fig. 1, provide that a data processing unit DV is connected downstream of the sensor S in order to receive the supply voltage U (as a measurement signal) from it. The data processing unit DV outputs the relevant supply signal VS (i.e. a signal that characterizes the supply voltage U) to the driver circuit T or to the higher-level control unit MC. The relevant signal paths are shown in dashed lines as arrows emanating from the data processing unit DV. As a data processing function, the data processing unit DV can have other functions in addition to outputting the supply signal VS, such as monitoring the supply voltage (or an on-board power supply HV).Therefore, the data processing unit DV can perform such a function and, since this function includes the processing of the (level of the) supply voltage U, can forward the supply voltage U, which is already present in terms of level, to the driver circuit T and / or to the higher-level control unit MC.

Claims

Patent 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 configured to receive a supply voltage value (U) and to transmit to the driver circuit (T) a supply signal (VS) which characterizes the supply voltage value (U), wherein the driver circuit (T) is configured to output a clocked control signal (GS) whose high level increases with decreasing supply voltage value (U).

2. Inverter control device according to claim 1, wherein - the higher-level control unit (MC) or the driver circuit (T) is connected to a voltage sensor (S) which is designed to detect a supply voltage (U) of a power circuit (LS) which is controlled by the driver circuit (T), wherein the supply voltage (U) defines the supply voltage value or - the higher-level control unit (MC) or the driver circuit (T) is connected to a data processing unit (DV) which is connected downstream of a voltage sensor (S) which is designed to detect a supply voltage (U) of a power circuit (LS) which is controlled by the driver circuit (T), wherein the supply voltage (U) defines the supply voltage value.

3. Inverter control device according to claim 1 or 2, wherein the higher-level control unit (MC) is configured to transmit a pulse pattern signal (PS) to the driver circuit (T), according to which the driver circuit (T) generates the clocked control signal (GS).

4. Inverter control device according to one of the preceding claims, wherein the control circuit (MC) is arranged to transmit to the driver circuit (T) a supply signal (VS) which represents the supply voltage value (U) as an absolute value, which represents the deviation of the supply voltage value (U) from a nominal value, or which represents the high level dependent on the level of the supply voltage value (U).

5. Inverter control device according to one of the preceding claims, wherein the control circuit (MC) is set up to transmit a pulse pattern signal (PS) corresponding to the clocked control signal (GS) and the supply signal (VS) which represents the supply voltage value (U), wherein the pulse pattern signal (PS) and the supply signal (VS) are transmitted via the same physical channel or wherein the pulse pattern signal (PS) and the supply signal (VS) are transmitted via different physical channels.

6. Inverter control device according to one of the preceding claims, wherein the increase of the high level with decreasing supply voltage value (U) is designed such that in the event of a short circuit which results for a power circuit (LS) which is controlled by the driver circuit (T), a short-circuit energy results in the load path of the power circuit (LS) which is not greater than a short-circuit energy at a nominal supply voltage value (U).

7. Inverter control device according to one of the preceding claims, wherein the control circuit (MC) is a microcontroller or a microprocessor having a control of an electrical machine which is configured to transmit a pulse pattern signal (PS) to the driver circuit (T).

8. Electric vehicle traction inverter (INV') with a power circuit (LS) and an inverter control device according to one of the preceding claims, wherein the driver circuit (T) is connected to the power circuit (LS) in a driving manner and the power circuit (LS) is connected to a supply voltage source (HV), wherein the supply voltage value (U) indicates the voltage of the supply voltage source (HV).

9. Driver circuit (T) configured to receive a pulse pattern signal (PS) and a supply signal (VS) which characterizes a value of a supply voltage (U) with which a power circuit (LS) is supplied, to which the driver circuit (T) is connected in a driving manner, wherein the driver circuit (T) has a mapping (VHZ) which assigns a higher high level to a comparatively reduced supply voltage value (U) than to a non-reduced supply voltage value (U), wherein the driver circuit (T) is configured to output a clocked control signal (GS) which is executed in accordance with the pulse pattern signal (PS) and which has the high level.

10. Method for controlling a power circuit (LS) of an inverter (INV), wherein a power circuit (LS) of the inverter is controlled by a driver circuit (T), and the driver circuit (T) is controlled by a control circuit (MC), wherein the control circuit (MC) transmits a supply voltage value (U) to the driver circuit and the driver circuit (T) controls the power circuit (LS) with a clocked control signal (GS) whose high level increases with decreasing supply voltage value (U).

11. Method according to claim 10, wherein the control circuit (MC) or the driver circuit (T) maps the supply voltage value (U) to the height of the high level.

12. The method according to claim 10 or 11, wherein the control circuit (MC) carries out a control of an electrical machine (EM) by means of which the pulse pattern signal (PS) is generated, wherein the control circuit (MC) transmits the pulse pattern signal (PS) and the supply voltage value (U) to the driver circuit via the same physical channel or via different physical channels.

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