ELECTRICAL CIRCUIT ARRANGEMENT AND METHOD FOR DETECTING A SHORT CIRCUIT

Description

[0001] The invention relates to an electrical circuit arrangement comprising an inverter and a measuring device for detecting a short circuit between a conductor and a shield in a circuit connected or connectable to the inverter, wherein the shield is capacitively connected to a ground of the inverter and a pulsed voltage can be generated on the conductor by the inverter. Furthermore, the invention relates to a method for detecting a short circuit between a conductor and a shield in a circuit connected to an electrical circuit arrangement, wherein the electrical circuit arrangement comprises an inverter and a measuring device for detecting the short circuit.

[0002] Electrical circuits in motor vehicles are subject to strict electromagnetic compatibility (EMC) requirements to prevent interference with other electrical circuits inside and outside the vehicle. In many cases, such electrical circuits include components such as electrical machines that are powered by an inverter. If a connection occurs between a conductor and a shield in the component or in a connector used to connect the component, a short circuit occurs.

[0003] Such a short circuit can, in particular, lead to the shield losing its shielding effect, i.e., its ability to prevent electromagnetic interference, due to the electrical connection between the conductor and the shield. Electromagnetic compatibility or the required limit values ​​can no longer be met by the electrical circuit arrangement. This can occur, for example, with a conductor carrying a motor phase current, since when a short circuit occurs, the pulsed voltage of the motor phase is applied to the shield, causing the shield to significantly lose its shielding effect relative to the conductor.

[0004] In order to be able to react to the possibly reduced shielding against interference, it is desirable to be able to determine or detect the occurrence of such a short circuit. It is generally known that a short circuit can be detected by measuring a short-circuit current. However, particularly in electrical circuit arrangements used in motor vehicles, system architectures may exist in which, due to purely capacitive connections between individual potentials, no closed circuit for a direct current or a low-frequency alternating current is created between the conductor and the shield in the event of a short circuit. In such a case, the short circuit will not lead to the formation of a significant short-circuit current or to an increase in the current on the conductor connected to the shield via the short circuit.However, even in such a case, the shielding effect of the shield may be lost, so it is desirable to be able to detect the occurrence of such a short circuit.

[0005] From DE 10 2014 018642 A1 an electrical circuit arrangement is known, comprising an inverter and a measuring device for determining a short circuit between a shield and a ground in a circuit connected or connectable to the inverter, wherein the shield is capacitively connected to a ground of the inverter, wherein the measuring device is designed to evaluate a voltage between the ground of the inverter and the shield.

[0006] The invention is therefore based on the object of specifying an electrical circuit arrangement which enables an improved detection of a short circuit between a conductor and a shield in a circuit connected or connectable to the inverter, in particular in the event that the short circuit does not lead to the occurrence of a significant short-circuit current.

[0007] To achieve this object, in an electrical circuit arrangement of the type mentioned at the outset, it is provided according to the invention that the measuring device is designed to evaluate a voltage between the ground of the inverter and the shielding and to generate a short-circuit signal when at least one pulse of the voltage occurs.

[0008] The pulsed voltage generated on the conductor by the inverter can, for example, move a current onto the conductor, which is then fed to the circuit that is connected to or can be connected to the inverter. This circuit can, for example, be an electrical machine or a circuit comprising an electrical machine. The electrical machine can be connected directly to the inverter and, for example, arranged as a common structural unit with the inverter in a housing. It is also possible for the circuit to include a connecting means with the inverter, for example a single-phase or multi-phase line or cable, via which the circuit is or can be connected to the inverter. The short circuit between the conductor and the shielding can in this case be in the connecting means or between the conductor or the conductor potential and the shielding ora shielding potential inside another component of the connected circuit or the connected electrical machine.

[0009] Due to the capacitive connection between the inverter's ground and the shielding, direct current or low-frequency alternating current cannot flow back through the inverter into a power source. If the electrical circuit is arranged such that a power source feeding the inverter is also capacitively connected to the shielding or capacitively decoupled from the shielding, no direct current or low-frequency alternating current can flow through such a path. The pulsed voltage that can be generated by the inverter on the conductor has a comparatively low frequency, e.g., 1 kHz or less, so that the current generated on the conductor cannot flow through the capacitive connections, as these represent a high impedance for the current.

[0010] Therefore, the occurrence of a short circuit between the conductor and the shield is determined according to the invention by measuring the voltage between the inverter ground and the shield. If there is no short circuit, the voltage between the inverter ground and the shield is not pulsed. If there is a short circuit between the conductor and the shield, a pulsed voltage is also present at the shield, so that the occurrence of pulses or the pulsed voltage on the shield or on a conductor connected to the shield potential can be used to infer a short circuit. Thus, the occurrence of a short circuit can be detected without a short-circuit current or an increased current on the conductor or something similar being required for short-circuit detection.

[0011] Advantageously, when a short circuit occurs between the conductor and the shield, a short-circuit signal describing the occurrence of the short circuit can be generated, based on which, for example, a measure can be taken to take account of the short circuit. For example, when the short-circuit signal is present or when a short-circuit signal describing an existing short circuit is present, the inverter and / or a circuit connected to the inverter can be shut down.

[0012] This prevents the electrical circuit arrangement and / or the switch that can be connected to it or is connected from being in an operating state in which increased interference emissions occur due to a short circuit between the conductor and the shielding. Impairment of other electrical circuit arrangements in the vicinity of the electrical circuit arrangement due to an undetected short circuit can thus be advantageously avoided. Particularly when the electrical circuit arrangement is used in a motor vehicle, specifications for electromagnetic compatibility can thus be met even if a short circuit occurs, and impairments due to increased interference emissions from other motor vehicle components and / or other electronic circuits in the vicinity of the motor vehicle can be avoided.

[0013] According to the invention, the measuring device can be configured to generate the short-circuit signal when multiple voltage pulses have occurred within a predetermined time. The detection of a short circuit and thus the generation of the short-circuit signal only occurs when multiple pulses, i.e., the presence of a pulse sequence or a pulsed and / or periodically changing voltage, are detected. A single pulse detected by the measuring device does not result in the generation of a short-circuit signal.

[0014] This has the advantage that individual pulses, which are used, for example, in an electrostatic discharge (ESD) test, do not lead to the detection of a short circuit. Such ESD pulses can occur particularly in electrical circuitry installed in motor vehicles, as ESD testing is a common test procedure for components installed in motor vehicles or for entire vehicles. The measuring device is therefore able to distinguish whether individual, non-repeating voltage pulses occur that are not caused by a short circuit and are, for example, the result of an ESD test, or whether multiple voltage pulses are measured, which therefore most likely indicate a short circuit.The specified time within which the multiple pulses can occur can be selected depending on a frequency of the pulsed voltage generated by the inverter and, for example, can cover a time range between 1 ms and 1 s, so that two subsequently performed ESD tests also do not lead to a short-circuit detection.

[0015] In a preferred embodiment of the invention, it can be provided that the measuring device comprises a comparator, wherein the voltage between the ground of the inverter and the shielding is applied to a first input of the comparator, and a reference voltage is applied to a second input of the comparator, wherein the measuring device is designed to generate the short-circuit signal from an output signal of the comparator.

[0016] The voltage present between the inverter's ground and the shielding can, for example, be dropped across at least one capacitor connected between a ground terminal of the inverter and a terminal at the shielding potential, thus creating the capacitive connection or decoupling between the shielding and the inverter's ground. The capacitor can be provided as a mounted component, particularly in a printed circuit board carrying the electrical circuit arrangement. In addition to the at least one capacitor, the capacitive connection can also include one or more resistive elements.

[0017] Depending on the voltage level that can be expected to occur across this capacitor or between the inverter ground and the shielding in the event of a short circuit, the voltage can be applied directly to the comparator input, or a voltage divider can be used to reduce the voltage, particularly if the expected voltages are above a permissible input voltage for the comparator. The use of a comparator that compares the voltage applied to a first input with the reference voltage advantageously compensates for fluctuations and / or an unpredictable level of the voltage applied to the first input and always generates the same comparator output signal, i.e., a logical 0 or 1, regardless of the actual value.Advantageously, voltages within a predetermined range that may occur during a short circuit can thus be evaluated, with the same comparator output signal always being generated regardless of the actual level. When the short-circuit signal is generated from the comparator output signal, a uniform output signal can be used, which occurs when the voltage applied to the first input is above the comparator's reference voltage. The reference voltage can, for example, be generated in a separate circuit of the measuring device. If there is no galvanic connection between a ground of the inverter and a separate ground of the measuring device, an isolating comparator or a comparator with a downstream isolator can be used.

[0018] According to the invention, it can further be provided that the measuring device comprises a retriggerable monostable multivibrator, wherein the hold time of the multivibrator is greater than the period of the pulsed voltage generated by the inverter and the output signal of the comparator is applied to the input of the multivibrator and the measuring device is designed to generate the short-circuit signal when the output signal of the multivibrator has a constant switching state for a predetermined period of time. A retriggerable monostable multivibrator, also referred to as a retriggerable monoflop, changes its switching state from a first switching state or initial state to a second switching state or active state for a specific period of time by means of a trigger signal applied to the input of the multivibrator. The multivibrator then returns to the initial state after the hold time has elapsed, wherein in a retriggerable orIn a retriggerable flip-flop, a new trigger signal received during the hold time restarts the timing until the flip-flop returns to the initial state, and the flip-flop remains in the active state. A new trigger signal received during the active, triggered state thus extends the active time state.

[0019] The hold time of the monostable multivibrator is preferably longer than the maximum period of the pulsed voltage generated by the inverter if the inverter can generate different frequencies, for example, to set different speeds for an electric motor connected to the inverter. The hold time can, for example, be twice the period or a maximum period of the voltage that can be generated by the inverter. If a short circuit occurs, an output signal that is permanently at a logical value is generated at the output of the monostable multivibrator, since the retriggerable multivibrator is constantly retriggered or triggered by the voltage pulses between the ground of the inverter and the shielding or the comparator output voltage pulses that arrive during the hold time.

[0020] The short-circuit signal can be generated if the output signal of the monostable multivibrator remains at the logical voltage level corresponding to the active switching state for a specified period of time, which in particular corresponds to several pulses of the voltage generated by the inverter. This allows a simple measuring device design with analog elements to be realized, which only generates a short-circuit signal when several pulses occur. Particularly in conjunction with the comparator, this also allows for tolerance to voltage fluctuations in the event of a short circuit, allowing a reliable and rapid diagnosis of a short circuit that has occurred.

[0021] According to the invention, it can be provided that the electrical circuit arrangement comprises a control device, wherein the short-circuit signal can be determined by the control device or can be transmitted from the measuring device to the control device, wherein the control device is designed to initiate at least one measure when the short-circuit signal is present.

[0022] The control device can therefore be part of the measuring device or it can be an additional control device of the electrical circuit arrangement. If it is part of the measuring device, the control device can generate the short-circuit signal from an output signal of the measuring device, in particular from the output signal of the flip-flop. This can occur, for example, if the output signal of the flip-flop corresponds to the active switching state of the flip-flop for a predetermined period of time. The predetermined period of time can in particular correspond to a multiple of the holding time of the flip-flop and, for example, comprise at least ten periods of the pulsed voltage generated by the inverter.Alternatively, it is possible for the short-circuit signal to be generated by another component of the measuring device from the output signal of the flip-flop and / or the comparator, wherein the short-circuit signal generated by the measuring device is transmitted to the control device, for example in the form of a one-bit signal or a voltage corresponding to a predetermined value.

[0023] In addition to detecting or receiving the short-circuit signal, the control device can also include further functions; in particular, it can also control or regulate the inverter. For this purpose, the control device can be connected or can be connected to at least one data communication interface, via which corresponding information or commands for operating the inverter can be received and / or sent. If a short-circuit signal is present, the control device can initiate a measure that takes the short circuit that has occurred into account. In particular, the inverter can be switched off and / or short-circuit information describing the presence of a short circuit can be transmitted via a data interface connected to the control device.

[0024] In a preferred embodiment of the invention, the electrical circuit arrangement can comprise a ground contact and / or a housing, wherein the ground contact and / or the housing are at the potential of the shielding, and the ground of the inverter is capacitively coupled to the ground contact and / or the housing. The ground contact can be embodied, for example, as a base plate made of a metal, as a layer in the structure of a printed circuit board, in particular a printed circuit board (PCB), of the electrical circuit arrangement.

[0025] The ground potential of the electrical circuit arrangement can additionally or alternatively also be applied to a housing, in particular a metal housing, of the electrical circuit. The shielding potential is applied to the ground contact and / or to the housing. This can be achieved, for example, via an electrical connection between the ground contact and the shielding, in particular via a contact pin provided for this purpose. A connection to a housing of the electrical circuit arrangement can also be made, for example, via an electrical pin on the housing side, which is or can be connected to the shielding of the circuit.

[0026] According to the invention, it can be provided that the inverter is connected or connectable to an energy storage device, wherein the energy storage device is capacitively coupled to the shield. The energy storage device can be, for example, a low-voltage energy storage device, in particular a low-voltage battery, which provides a voltage of, for example, 12 volts, 24 volts, or 48 volts. Alternatively, it is possible for the energy storage device to be a high-voltage energy storage device, in particular a high-voltage battery, which provides a voltage between 400 volts and 800 volts. The capacitive coupling of the energy storage device to the shield can be direct or indirect. An indirect capacitive coupling can occur, for example, if the energy storage device and the shield are each capacitively coupled to another potential, for example the chassis of a motor vehicle.

[0027] In electrical circuit arrangements used in a motor vehicle, the low-voltage energy storage device can, for example, be a battery intended to supply a low-voltage vehicle electrical system. In a high-voltage energy storage device, it can accordingly be a traction energy storage device that operates a high-voltage vehicle electrical system and can, for example, supply current to a traction electric machine as a circuit connected to the inverter via the inverter of the electrical circuit arrangement. The energy storage device connected to the inverter is, in particular, also capacitively coupled to the shielding or to a chassis coupled to the shielding, so that in the event of a short circuit, no short-circuit current can flow into the energy storage device via the conductor and the shielding.

[0028] In a preferred embodiment of the invention, the electrical circuit arrangement can have a circuit connected to the inverter, wherein the circuit comprises at least one electrical machine. The inverter of the electrical circuit arrangement can be designed, in particular, as a three-phase inverter, for example, as a B6 bridge comprising three half-bridges or as a pulse-controlled inverter.

[0029] The electrical circuit arrangement can be a roll stabilizer, an electric steering system and / or an electric traction drive for a motor vehicle. Many other systems with this architecture are also conceivable, so that the electrical circuit arrangement can also be used for other purposes. The electric steering system can, for example, be a front-axle steering system or a rear-axle steering system. The electric machine of the circuit connected to the inverter can therefore be, for example, an electric traction machine for a motor vehicle. It is also possible for the electric machine of the circuit to be part of a motor vehicle actuator that is different from a traction drive and is controlled or operated via the electrical circuit arrangement.

[0030] For a method according to the invention for detecting a short circuit between a conductor and a shield in a circuit connected to an electrical circuit arrangement, wherein the electrical circuit arrangement comprises an inverter and the shield is capacitively connected to a ground of the inverter, wherein a pulsed voltage is generated on the conductor by the inverter, it is provided that a voltage between the ground of the inverter and the shield is evaluated and a short circuit signal is generated when at least one pulse of the voltage occurs.

[0031] The short-circuit signal can be generated if several voltage pulses have occurred within a given time.

[0032] The electrical circuit arrangement can comprise a measuring device that evaluates the voltage between the ground of the inverter and the shielding and generates a short-circuit signal upon the occurrence of at least one voltage pulse. Preferably, the measuring device can comprise a comparator, with the voltage between the ground of the inverter and the shielding being applied to a first input of the comparator and a reference voltage being applied to a second input of the comparator, with the measuring device generating the short-circuit signal from an output signal of the comparator.

[0033] Preferably, the measuring device may comprise a retriggerable monostable flip-flop, wherein the holding time of the flip-flop is greater than the period of the pulsed voltage generated by the inverter and the output signal of the comparator is applied to the input of the flip-flop and the short-circuit signal is generated by the measuring device when the output signal of the flip-flop has a constant switching state for a predetermined period of time.

[0034] Preferably, the electrical circuit arrangement may comprise a control device, wherein the short-circuit signal is determined by the control device or transmitted from the measuring device to the control device, wherein the control device initiates at least one measure when the short circuit occurs.

[0035] All the advantages and embodiments described above in relation to the electrical circuit arrangement according to the invention apply accordingly to the method according to the invention and vice versa.

[0036] The invention is explained below using exemplary embodiments with reference to the drawings. The drawings are schematic representations and show: Figure 1 shows an embodiment of an electrical circuit arrangement according to the invention, and Figure 2 shows a detailed view of the measuring device of the electrical circuit arrangement according to the invention.

[0037] In Figure 1an embodiment of an electrical circuit arrangement 1 is shown. The electrical circuit arrangement comprises an inverter 2 and a measuring device 3 for detecting a short circuit in a circuit 4 that is connected or connectable to the inverter 2. In the present example, the circuit 4 connected to the inverter 2 comprises an electrical machine 5 and a connecting means 6, which in the present example is designed as a three-phase, shielded motor cable. Via the connecting means 6, an alternating current, which in the present embodiment is three-phase, can be transmitted from the inverter 2 to the electrical machine 5, so that motor operation of the electrical machine 5 is possible via the inverter 2. To provide this alternating current, the inverter 2 is connected to an energy storage device 7. The inverter 2 can be designed, for example, as a B6 bridge.

[0038] The measuring device 3 is designed to detect a short circuit between a conductor 8 and a shield 9 of the circuit 4. This short circuit is schematically represented as a dashed connection 10 between the conductor 8 and the shield 9. The short circuit can occur in the connecting means 6 or within the electrical machine 5.

[0039] The conductor 8 is connected to an AC side of the inverter 2. The shield 9 is capacitively connected to a ground potential GND 1 of the inverter 2 via a capacitor C 1. The shield 9 is connected via a contact pin 11 to a housing 12 of the electrical circuit arrangement 1, wherein the housing 12 is a metal housing and represents a ground potential GND 1 of the electrical circuit arrangement 1. A capacitor C 2 is arranged between the ground potential GND 1 of the inverter 2 and the ground potential GND 2 of the housing 12, so that the ground GND 1 of the inverter is also capacitively coupled to the shield 9 connected to the housing 12 via the capacitor C 2.

[0040] In addition to the capacitances C 1 and C 2, the connection between GND 1 and GND 2 can also include one or more resistive elements. The capacitances C 1 and C 2, as well as any resistive elements present, can be configured, for example, as populated capacitors or resistors on a printed circuit board on which the electrical circuit arrangement 1 is formed in whole or in part.

[0041] The electrical circuit arrangement 1 is shown installed in a motor vehicle, with the connections of the components to a ground potential GND 3 of the motor vehicle, for example a ground of a chassis of the motor vehicle, also being shown. The housing 12 is resistively connected to the ground GND 3 via a resistor R 1. A ground potential GND 4 of the electrical machine 5 of the circuit 4 is also resistively coupled to the ground GND 3 via a resistor R 2. The energy store 7 is also capacitively coupled to the ground GND 3 via a capacitor C 3. When the short circuit 10 occurs between the conductor 8 and the shield 9, every possible short-circuit current path runs via at least one of the capacitive connections formed by the capacitors C1, C2 and C3. In this way, a direct current ora low-frequency alternating current cannot flow as a short-circuit current, since the capacitive connections represent an infinite or at least a very high impedance for such a current.

[0042] The inverter 2 generates a pulsed, in this case three-phase voltage, for example at a switching frequency between 1 kHz and 500 kHz, in particular between 10 kHz and 20 kHz, on the conductors 8 of the circuit 4. This voltage causes a current on the conductors 8 of the circuit 4, the frequency of which is, for example, between 1 Hz and 10 kHz, in particular between 1 Hz and 1 kHz. If a short circuit occurs between the conductor 8 and the shield 9, the voltage UP of one of the phases, pulsed at the switching frequency of the inverter, is also present at the shield 9, the frequency of the voltage UP being significantly higher than the frequency of the current fed into the electrical machine 5, also referred to as the fundamental motor current frequency.

[0043] The voltage UP applied to the shield 9 causes the shield to lose its shielding effect. This can result in impaired electromagnetic compatibility (EMC) of the circuit 4, which is why the measuring device 3 is designed to detect such a short circuit. Since the measurement of a short circuit is not possible via a short-circuit current or via a measurement of the phase currents flowing on the conductors 8 for energizing the electrical machine 5, the measuring device 3 evaluates a voltage UM between the ground GND 1 of the inverter 2 and the shield 9. The voltage UM corresponds to the switching frequency of the inverter 2 and is significantly higher frequency than the motor current frequency. The measuring device 3 is also designed to generate a short-circuit signal upon the occurrence of at least one pulse of this voltage.

[0044] The housing 12 of the electrical circuit arrangement 11 can be designed as a metal housing that is connected to the ground potential GND 2. Alternatively, the ground contact of the ground potential GND 2 can also be designed as a conductive metal plate and / or as a layer of a circuit board, for example a printed circuit board, of the electrical circuit arrangement 1.

[0045] In Figure 2 The structure of the measuring device 3 is shown schematically. The measuring device 3 comprises a comparator 13 and a flip-flop 14. Furthermore, the measuring device 3 comprises a control device 15, which is designed, for example, as a microcontroller. Alternatively, the measuring device 3 is connected to a control device 15 of the electrical circuit arrangement 1, as will be explained in more detail below. The ground potential of the control device 15 is in Figure 2referred to as GND 5. The ground potential GND 5 of the control device 15 can be galvanically connected to the ground potential GND 1 of the inverter 2. For this purpose, for example, a galvanic connection 16 in the form of a conductor track can be provided on a circuit board of the electrical circuit device 1. Alternatively, another type of galvanic connection 16 can also be provided, for example a connecting metallization between the equipotential surfaces assigned to the ground potentials GND 1 and GND 5 of one or more circuit boards of the electrical circuit arrangement 1. If there is no galvanic connection between the ground potential GND 1 of the inverter 2 and the ground potential GND 5, the comparator 13 can also be designed as an isolating comparator or as a comparator with a downstream insulator.

[0046] The voltage UM between the ground GND 1 of the inverter 2 or the ground GND 5 of the control device 15 connected to it and the shielding or the ground potential GND 2 of the electrical circuit arrangement 1 is applied to a first input 17 of the comparator 13. A reference voltage source 19 is connected to a second input 18 of the comparator, so that the voltage applied to the first terminal 17 is compared with the reference voltage UR applied to the second terminal 18. For example, the first terminal 17 can be a negative terminal of the comparator and the second terminal 18 a positive terminal of the comparator. A reverse assignment is also possible.Depending on the level of the voltages that can occur between the shielding 9 and the ground GND 1 of the inverter 2, the measuring device 3 can comprise a voltage divider so that the voltages UM can be reduced to a voltage level that matches the input 18 of the comparator 13.

[0047] The output 20 of the comparator 13 is connected to the flip-flop 14. The flip-flop 14 is designed as a retriggerable monostable flip-flop, also referred to as a retriggerable monoflop, and can be in the form of an integrated circuit (IC), for example. The hold time of the flip-flop 14 is greater than the period of the pulsed voltage U p generated by the inverter 2, which is applied to the conductor 8 or, in the case of a short circuit, also to the shield 9. The hold time can, for example, be at least twice the period or the maximum period that can be generated by the inverter 2 during operation of the circuit 4 or the electrical machine 5.

[0048] The use of comparator 13 makes it possible to generate a similar output signal corresponding to a logic level at output 20 of comparator 13, even when the measured voltage UM exceeds the reference voltage UR, even if the voltages between ground GND 1 of inverter 2 and shielding 9 vary. In this way, measuring device 3 can be robustly designed to accommodate varying voltages UM. This improves the reliability of measuring device 3 or electrical circuit arrangement 1 in detecting a short circuit.

[0049] The use of the monostable multivibrator 14 makes it possible to design the measuring device 3 such that it generates the short-circuit signal when several pulses of the measured voltage UM have occurred within a predetermined time. If the multivibrator 14 is designed as a retriggerable monostable multivibrator and the hold time of an activated state of the multivibrator 14 is greater than the period of the pulsed voltage U p generated by the inverter 2, the hold time of the multivibrator 14 is continuously retriggered when a short circuit occurs, resulting in a constant signal level at an output 21 of the multivibrator 14.

[0050] If this is present for a predetermined time, which in particular is greater than one or more periods of the pulsed voltage generated by the inverter 2, a short circuit can be concluded. The output 21 of the flip-flop 14 can be connected to the control device 15, wherein the control device 15 carries out the corresponding evaluation of the output 21. This means that the control device 15 monitors whether an active switching state of the flip-flop 14 exists for the predetermined time. Alternatively, a different type of evaluation can also be carried out, for example by a further, in particular analog component of the measuring device 3. In this case, the control device may not be a component of the measuring device, wherein the short-circuit signal generated by the measuring device 3 is transmitted to the control device 15.

[0051] Both cases have the advantage that the short-circuit signal is present in analog form or is determined based on the duration of an analog signal at the output 21 of the flip-flop 14, so that the short-circuit signal can be used quickly and without digitization delay to initiate measures due to the short circuit. For example, it is possible for the short-circuit signal to be transmitted to the electrical machine 5 or another component of the circuit 4, so that its operation is stopped. Another type of use in the circuit 4 is also possible, in particular if the circuit 4 has a different structure than that shown. Furthermore, it is possible for the control device 15 to be connected to a communications link, so that the short-circuit information and / or information on measures to be taken due to the short circuit can also be transmitted to other components of a motor vehicle.

[0052] The electrical circuit arrangement 1 can be designed, for example, as a roll stabilizer, an electric steering system, and / or as an electric traction drive for a motor vehicle. It is possible for the circuit 4 to represent part of the circuit arrangement 1, in particular for the electric machine 5 to be directly connected to the inverter 2 and for no connecting means 6 to be used. Even in such a case, a short circuit can be detected between a conductor 8 or a line potential and a shield 9 or a shielding potential inside the motor 5. As shown in Figure 2As shown, the measuring device 3 and the control device 15 can be designed as a control unit 22 connected to the inverter 2. The control unit 22 can further comprise a device 23 for generating a supply voltage for the comparator 13 and a device 24 for generating a supply voltage for the flip-flop 24. It is possible that the inverter 2 is also designed as part of the control unit 22, as shown in Figure 1 is shown.

[0053] The energy storage device 7 can be designed as a low-voltage energy storage device, for example as a low-voltage battery, and have a voltage level of 12 volts, 24 volts, or 48 volts. This is particularly possible if the electrical circuit arrangement 1 is designed as a roll stabilizer or an electric steering system. In a circuit arrangement 1 designed as an electric traction drive for a motor vehicle, the energy storage device 7 can be designed as a high-voltage energy storage device, in particular a high-voltage battery, and provide a voltage between 700 volts and 800 volts. Depending on the design of the electrical circuit arrangement 1, the circuit 4, in particular the size and / or the power to be converted by the electrical machine 5, can also be selected differently. Use of the electrical circuit arrangement 1 for other purposes in addition to those mentioned above is also possible.

[0054] In one embodiment of the method according to the invention, the measuring device 3 evaluates the voltage UM between the ground GND 1 of the inverter 2 and the shielding 9, and if several pulses of the voltage UM occur, i.e. if a pulsed voltage UM occurs at the shielding 9 with respect to the ground GND 1 of the inverter 2, a short-circuit signal is generated. For this purpose, the voltage UM at the first input 17 of the comparator 13 is compared with the reference voltage UR at the second input 18 of the comparator 13. If the reference voltage UR is exceeded, an output signal, for example a logical one, is generated at the output 20. This triggers the flip-flop 14, so that it also generates a logical one, for example, at its output 21.

[0055] Since the hold time of the flip-flop 14 is longer than the period of the pulsed voltage U p of the inverter 2 and thus also of the pulsed voltage UM between the ground GND 1 of the inverter 2 and the shield 9 in the event of a short circuit, continuous retriggering of the flip-flop 14 is achieved. At the output 20 of the flip-flop, for example, a logical one is therefore permanently present, whereby the short-circuit signal is generated by the control device 15 if this logical one is present for a period of time which is longer than the hold time of the flip-flop 14. The hold time of the flip-flop 14 can, for example, correspond to twice the period of U p and the period for which the control device 15 evaluates the signal at the output 21 of the flip-flop 14 can be a multiple, for example ten times, of the period of the voltage Up and thus likewise exceed the hold time of the flip-flop.

[0056] By selecting a shorter hold time for the flip-flop and a shorter period for which the control device 15 evaluates the signal at output 21 of the flip-flop 14, it is also possible for a single pulse of the voltage UM to generate a short-circuit signal describing a short circuit that has occurred. This can occur, for example, if robustness of the short-circuit detection against an ESD test is not required.

[0057] The control device 15 can then take action to counteract the short circuit that has occurred. For example, the control device 15 can also be configured to control or regulate the inverter 2 and shut down the inverter 2. Additionally or alternatively, the control device 15 can transmit corresponding short-circuit information via a data interface (not shown here), so that, for example, if the electrical circuit 1 is arranged in a motor vehicle, a corresponding action can also be taken by other components of the motor vehicle.

[0058] The use of the flip-flop 14 and the detection of multiple pulses in the voltage UM has the advantage that a single pulse, which may occur, for example, during an ESD test, is not detected as a short circuit between the conductor 8 and the shield 9. Only multiple pulses within a predetermined time, which may be, for example, between 1 ms and 1 s, are interpreted by the measuring device 3 as a short circuit. This ensures that no short circuit is detected during an ESD test of a motor vehicle comprising the electrical circuit arrangement 1. List of reference symbols

[0059] 1Circuit arrangement 2Inverter 3Measuring device 4Circuit 5Motor 6Connector 7Energy storage 8Conductor 9Shielding 10Connection 11Contact pin 12Housing 13Comparator 14Flip-flop 15Control device 16Connection 17First input 18Second input 19Reference voltage source 20Output 21Output 22Control unit 23Device 24Device

Claims

1. An electrical circuit arrangement comprising an inverter (2) and a measuring device (3) for identifying a short circuit between a conductor (8) and a shielding (9) in a circuit (4) that is connected or can be connected to the inverter (2), wherein the shielding (9) is connected capacitively to a ground (GND1) of the inverter (2), and a pulsed voltage (UP) can be generated on the conductor (8) by the inverter (2), wherein the measuring device (3) is designed to evaluate a voltage (UM) between the ground (GND1) of the inverter (2) and the shielding (9) and to generate a short circuit signal when at least one pulse of the voltage (UM) occurs.

2. The electrical circuit arrangement according to claim 1, characterized in that the measuring device (3) is designed to generate the short circuit signal when a plurality of pulses of the voltage (UM) have occurred within a specified period of time.

3. The electrical circuit arrangement according to claim 1 or 2, characterized in that the measuring device comprises a comparator (13), wherein the voltage (UM) is applied between the ground (GND1) of the inverter (2) and the shielding (9) at a first input (17) of the comparator (13) and a reference voltage (UR) is applied at a second input (18) of the comparator (13), wherein the measuring device (3) is designed to generate the short circuit signal from an output signal of the comparator (13).

4. The electrical circuit arrangement according to claim 3, characterized in that the measuring device (3) comprises a retriggerable mono-stable trigger circuit (14), wherein the holding time of the trigger circuit (14) is greater than the period of the pulsed voltage (UP) generated by the inverter and the output signal of the comparator (13) is applied to the input of the trigger circuit (14) and the measuring device (3) is designed to generate the short circuit signal when the output signal of the trigger circuit (14) has a constant switching state for a predetermined period of time.

5. The electrical circuit arrangement according to any one of the preceding claims, characterized in that the electrical circuit arrangement (1) comprises a control device (15), wherein the short circuit signal can be identified by the control device (15) or can be transmitted from the measuring device (3) to the control device (15), wherein the control device (15) is designed to initiate at least one action when the short circuit signal is present.

6. The electrical circuit arrangement according to any one of the preceding claims, characterized in that it comprises a ground contact and / or a housing (12), wherein the ground contact and / or the housing (12) are at the potential of the shielding (9) and the ground (GND1) of the inverter (2) is coupled capacitively to the ground contact and / or the housing (12).

7. The electrical circuit arrangement according to any one of the preceding claims, characterized in that the inverter (2) is connected or can be connected to an energy store (7), wherein the energy store (7) is coupled capacitively to the shielding (9).

8. The electrical circuit arrangement according to any one of the preceding claims, characterized in that it has a circuit (4) connected to the inverter (2), wherein the circuit comprises at least one electrical machine (5).

9. The electrical circuit arrangement according to claim 8, characterized in that the electrical circuit arrangement (1) is a roll stabilizer, an electric steering system and / or an electric traction drive for a motor vehicle.

10. A method for detecting a short circuit between a conductor (8) and a shielding (9) in a circuit (4) connected to an electrical circuit arrangement (1), wherein the electrical circuit arrangement (1) comprises an inverter (2) and the shielding (9) is connected capacitively to a ground (GND1) of the inverter (2), wherein a pulsed voltage (UP) is generated on the conductor (8) by the inverter (2), wherein a voltage (UM) is evaluated between the ground (GND1) of the inverter (2) and the shielding (9) and a short circuit signal is generated when at least one pulse of the voltage (UM) occurs.