Measuring assembly for detecting faults in a controller

Abstract

The invention relates to a measuring assembly (10) for detecting faults in a controller (1C), having an ohmic resistor (Rp) which is connected between two galvanically isolated voltage domains (3, 5) and interconnects reference potentials of voltage sources (4, 6) of the two voltage domains (3, 5); a first measuring device (11) which determines a first measuring voltage (UM1), produced by a current flow, at the ohmic resistor (Rp); another ohmic resistor (Rpu) which, in a first test mode, connects the potential of a first nominal voltage (U1) of the higher, first voltage domain (3) to the reference potential of a second nominal voltage (U2) of the lower, second voltage domain (5) via a switching element (S); a second measuring device (12) which, in the first test mode, detects a second measuring voltage (UM2) between at least one connection pin (9) of the lower second voltage domain (5) and the reference potential of the first nominal voltage (U1) of the higher first voltage domain (3); and an evaluation and control unit (16) which, in a normal mode, detects the first measuring voltage (UM1) at the ohmic resistor (Rp), activates the first test mode, and, in the first test mode, evaluates the second measuring voltage (UM2) at the other ohmic resistor (Rpu) and identifies multiple types of short circuits in the controller (1). The invention also relates to a controller (1) having at least one such measuring assembly (10) for detecting faults.

Description

[0001] R. 418155

[0002] - 1 -

[0003] Description

[0004] title

[0005] A measuring arrangement for fault detection in a control unit

[0006] The invention relates to a measuring arrangement for fault detection in a control unit. The present invention also relates to a control unit with such a measuring arrangement for fault detection.

[0007] Modern vehicles increasingly use different voltage domains. As can be seen in Fig. 1, an illustrated embodiment of a control unit 1A of a vehicle, for example, provides a first voltage domain 3 with a first voltage source 4 and a first nominal voltage U1 of 48 volts for high-current consumers V1, and a second voltage domain 5 with a second voltage source 6 and a second nominal voltage U2 of 12 volts for standard consumers V2, V3. Since the cables of these voltage domains 3, 5 can potentially be short-circuited in the vehicle, the standard consumers V2, V3 of the second voltage domain 5 with the second nominal voltage U2 of 12 volts can be destroyed by a short circuit 7 to the first voltage domain 3 with the first nominal voltage U1 of 48 volts. This is illustrated in Fig. 1 by the dashed outline around the standard consumer V2.Since many standard consumers V2, V3 of the second voltage domain 5 with the second nominal voltage U2 of 12 volts would be destroyed by a short circuit 7 to the first voltage domain 3 with the first nominal voltage U1 of 48 volts, the standard consumers V2, V3 of the second voltage domain 5 are protected accordingly. For units with few supply lines, this can be accomplished with little effort. However, for control units that have a large number of lines to the vehicle, such as an airbag control unit, protecting the individual lines is not possible or only with great difficulty. R. 418155.

[0008] - 2 -

[0009] As can be seen in Fig. 2, the standard loads V2, V3 of the second voltage domain 5 can, for example, be galvanically decoupled from the first voltage domain 3 in order to protect them. This is preferably achieved by an isolated DC / DC converter (not shown) which isolates the second voltage domain 5, with its second nominal voltage U1 of 12 volts, from the first voltage domain 3, with its first nominal voltage U1 of 48 volts. This measure prevents the standard loads V2, V3 of the second voltage domain 5 from being destroyed by a single short circuit 7 to the first voltage domain 3. However, such a short circuit 7 between the two voltage domains 3, 5 can no longer be detected and thus becomes a "latent fault".If another short circuit 7 occurs between the two voltage domains 3, 5, this can again lead to the destruction of a standard consumer V2, V3 of the second voltage domain 5.

[0010] This procedure can also be used if the standard loads V2 and V3 of the second voltage domain 5 are supplied from the first voltage domain 3. In this case, the DC / DC converter, in addition to galvanic isolation, also reduces the voltage to the permissible value.

[0011] From DE 10235 162 A1, a control unit in a vehicle is known which is characterized by the fact that the power supply runs via a converter that provides galvanic isolation. In addition, the component isolated by this galvanic isolation is connected for data exchange with external components and other components in the control unit that are not galvanically isolated by means of a coupling element that also provides galvanic isolation.

[0012] From DE 102015 211 663 A1, an arrangement for use in a motor vehicle is known, comprising at least one central control unit, at least two decentralized control units, and at least two actuators. In this arrangement, at least one signal connection exists between the central control unit and each decentralized control unit. At least one signal connection also exists between each decentralized control unit and each actuator. (R. 418155)

[0013] - 3 -

[0014] The vehicle has a first electrical system and a second electrical system; the first and second electrical systems are galvanically isolated from each other or connected at a star point. The first electrical system includes at least part of the central control unit. The second electrical system includes at least part of the actuators. The second electrical system includes at least part of the decentralized control units.

[0015] Disclosure of the invention

[0016] The measuring arrangement for fault detection in a control unit with the features of independent claim 1 and the control unit for a vehicle with the features of independent claim 17 each have the advantage that a short circuit between two galvanically isolated voltage domains with different nominal voltages can be reliably detected. The switchable additional ohmic resistor allows a reference potential (for example, in the sense of a ground potential) of a lower voltage domain to be raised relative to the reference potential of the higher voltage domain. This enables the detection, during initial testing, of short circuits from connection pins of the lower voltage domain to the potential of the nominal voltage of the lower voltage domain or to the potential of the nominal voltage of the higher voltage domain.The measures described above allow a control unit with a lower voltage domain to be operated robustly in an environment with a higher voltage domain without sacrificing full diagnostic capability.

[0017] If a galvanic isolator is used to decouple a second voltage domain with a lower nominal voltage from a first voltage domain with a higher nominal voltage, the reference potential of the second voltage domain on the secondary side of the galvanic isolator is undefined relative to a reference potential of the first voltage domain (floating potential). Therefore, a single short circuit between terminals of the two galvanically isolated voltage domains can no longer be detected. Each individual short circuit between two terminals of the two voltage domains would thus become a "dormant" or "latent" single fault. A second short circuit between two terminals of the two voltage domains would then be detected.

[0018] - 4 -

[0019] A short circuit between the other terminals of the two voltage domains could then lead to the destruction of the standard loads of the second voltage domain or to the destruction of the control unit. To solve the problem of failing to detect a short circuit between two terminals of the two voltage domains, in embodiments of the invention, the reference potentials of the two voltage domains can be connected to each other via the ohmic resistor. This provides a high-impedance reference potential against which a standard diagnostic tool is able to detect a single short circuit. A current flowing through the ohmic resistor in the event of a short circuit allows the corresponding short circuit between the two voltage domains to be detected.

[0020] Embodiments of the present invention provide a measuring arrangement for fault detection, and in particular for short-circuit detection, in a control unit with two galvanically isolated voltage domains, each comprising a voltage source and different nominal voltages. The measuring arrangement includes an ohmic resistor which is connected between the two galvanically isolated voltage domains and connects the reference potentials of the two voltage sources of the two voltage domains. Furthermore, at least one first measuring device is provided, which is configured to determine a first measuring voltage across the ohmic resistor caused by a current flow.Furthermore, the measuring arrangement includes an additional ohmic resistor which, during an initial test operation, connects a potential of a first nominal voltage of a higher first voltage domain to a reference potential of a second nominal voltage of a lower second voltage domain via a switching element. In particular, the reference potential of the second voltage domain, which has a lower voltage level, is changed or raised. At least one second measuring device is also provided, which is designed to detect a second measuring voltage during the initial test operation between at least one terminal of the lower second voltage domain and a reference potential of the first nominal voltage of the higher first voltage domain. The measuring arrangement also includes an evaluation and control unit, which is designed to evaluate the first measuring voltage across the ohmic resistor during normal operation. (R. 418155.)

[0021] - 5 -

[0022] to activate and, in the first test operation, to evaluate the second measuring voltage at the further ohmic resistance and, depending on the evaluation, to detect several types of short circuits in the control unit.

[0023] Furthermore, a control unit for a vehicle, with two galvanically isolated voltage domains, each comprising a voltage source and different nominal voltages, and a measuring arrangement for fault detection is proposed.

[0024] The two measuring devices can preferably each be designed as a voltmeter. This allows for simple, direct measurement of the first voltage across the ohmic resistor and the second voltage across the other ohmic resistor. Furthermore, in the event of a short circuit, the corresponding short-circuit current can be easily and quickly determined from a detected increase in the first voltage across the ohmic resistor.

[0025] In this context, the term control unit can be understood as an electrical device, such as an airbag control unit, which processes or evaluates detected sensor signals.

[0026] In this context, the term "evaluation and control unit" refers to an electrical circuit that is part of a control device and processes or evaluates acquired sensor signals. The evaluation and control unit can have at least one interface, which may be implemented in hardware and / or software. In the case of a hardware implementation, the interfaces may, for example, be part of a so-called system ASIC, which incorporates various functions of the evaluation and control unit. However, it is also possible for the interfaces to be separate integrated circuits or at least partially composed of discrete components. In the case of a software implementation, the interfaces may be software modules that are present, for example, on a microcontroller alongside other software modules.Also advantageous is a computer program product with program code stored on a machine-readable medium such as semiconductor memory, hard disk memory or optical memory and for R. 418155.

[0027] - 6 -

[0028] The evaluation is performed when the program is executed by the evaluation and control unit.

[0029] The measures and further developments listed in the dependent claims enable advantageous improvements to the measuring arrangement for fault detection in a control unit specified in independent claim 1 and to the control unit for a vehicle specified in independent claim 17.

[0030] It is particularly advantageous that the at least one second measuring device can be electrically connected to several connection pins of the lower second voltage domain via a switchable multiplexer. The evaluation and control unit can be further configured to control the switchable multiplexer during the initial test operation such that the at least one second measuring device is sequentially electrically connected to the individual connection pins of the lower second voltage domain. Preferably, the at least one second measuring device can be sequentially connected to the individual connection pins of the lower second voltage domain in a predetermined order.This measure preferably allows all connection pins of the lower voltage domain to be checked to see if there are short circuits to the potential of the first nominal voltage of the higher first voltage domain or to the potential of the second nominal voltage of the lower second voltage domain.

[0031] In an advantageous embodiment of the measuring arrangement, the evaluation and control unit can detect a first short circuit between the two voltage domains during normal operation when the first measuring voltage across the ohmic resistor, caused by a short-circuit current, exceeds a first threshold value. The first threshold value can preferably be selected such that it lies between a lower nominal voltage of, for example, 12 volts and a higher nominal voltage of, for example, 48 volts.

[0032] In a further advantageous embodiment of the measuring arrangement, the evaluation and control unit can, during the first test operation, create a second short circuit between the corresponding connection pin of the lower second resistor. 418155

[0033] - 7 -

[0034] The evaluation and control unit can detect a third short circuit between the corresponding terminal pin of the lower second voltage domain and the potential of the second nominal voltage of the lower second voltage domain if the second measured voltage across the further ohmic resistance falls below a second threshold. Alternatively, the unit can detect a third short circuit between the corresponding terminal pin of the lower second voltage domain and the potential of the second nominal voltage of the lower second voltage domain if the second measured voltage across the further ohmic resistance exceeds the second threshold and falls below a third threshold.As a further alternative, the evaluation and control unit can detect a fourth short circuit between the corresponding connection pin of the lower second voltage domain and the potential of the first nominal voltage of the higher first voltage domain if the second measured voltage at the further ohmic resistance exceeds the third threshold.

[0035] In a further advantageous embodiment of the measuring arrangement, a current source can be configured to generate a test current through the ohmic resistor in a second test mode. The evaluation and control unit can be further configured to activate the second test mode and verify the functionality of the ohmic resistor during this second test mode. Since the ohmic resistor is an important component of fault detection, it is advantageous to monitor its functionality. A short circuit in the ohmic resistor would reconnect the two voltage domains galvanically, and a single short circuit could destroy a load or the voltage domain with the lower nominal voltage. If the ohmic resistor is interrupted, fault detection would no longer be possible.Furthermore, by monitoring the ohmic resistance, other dormant faults between the voltage domains, such as a short circuit between the reference potentials of the two voltage sources of the two voltage domains, can be detected, which cannot be found via normal fault detection.

[0036] In a further advantageous embodiment of the measuring arrangement, the evaluation and control unit can be further developed, in the second test operation the ohmic resistance. 418155

[0037] - 8 -

[0038] A resistor is identified as faulty if the first measurement voltage across the resistor, generated by the test current, is below a lower fourth threshold or above a higher fifth threshold that is lower than the first threshold. Alternatively, the resistor can be identified as fault-free if the first measurement voltage across the resistor, generated by the test current, is greater than or equal to the fourth threshold and less than or equal to the fifth threshold. In the second test mode, the evaluation and control unit can detect a short circuit in the resistor if the first measurement voltage across the resistor, generated by the test current, is below the fourth threshold. In such a short circuit, the measurement voltage will be 0 volts.Alternatively, the evaluation and control unit can detect an open-circuit resistor during testing if the initial measurement voltage across the resistor, caused by the test current, exceeds the fifth threshold. The open-circuit resistor results in a significantly higher measurement voltage than a fault-free resistor, which can be calculated by multiplying the test current value by the resistance value. Accordingly, the fourth and fifth thresholds can be selected and predefined.

[0039] In a further advantageous embodiment of the measuring arrangement, the evaluation and control unit can be further configured to activate the first test operation and / or the second test operation initially, for example when a vehicle is started, or cyclically for a predetermined period of time. The period of time can be predefined to ensure stable voltage measurements.

[0040] In a further advantageous embodiment of the measuring arrangement, the evaluation and control unit can be designed to suspend the test operation if a short circuit between the two voltage domains is detected. This prevents negative influence or damage to the power source.

[0041] In a further advantageous embodiment of the measuring arrangement, the evaluation and control unit can be further designed to provide corresponding error messages about the types of short circuits detected in the control unit and / or about a missing resistor. 418155

[0042] - 9 -

[0043] The system generates and outputs the functionality of the ohmic resistance. This allows the driver to be warned in time and contact or visit a repair shop.

[0044] In a further advantageous embodiment of the measuring arrangement, the ohmic resistor can provide a high-impedance reference potential. The ohmic resistor can preferably have a value in the range of 1 kilohm to 5 kilohm. Furthermore, the ohmic resistor can limit the short-circuit current and thereby prevent damage to any of the connected devices.

[0045] In a further advantageous embodiment of the measuring arrangement, the additional ohmic resistance can raise the reference potential of the second nominal voltage of the lower second voltage domain in the first test operation and, for example, have a value in the range of 1 kiloohm to 5 kiloohms.

[0046] In a further advantageous embodiment of the measuring arrangement, a capacitor can be connected in parallel to the ohmic resistor, which is designed to reduce EMC interference (EMC: Electromagnetic Compatibility).

[0047] In an advantageous embodiment of the control unit, a first nominal voltage of a first voltage source of a first voltage domain can be higher than a second nominal voltage of a second voltage source of a second voltage domain. For example, the first nominal voltage can be 48 volts, and the second nominal voltage can be 12 volts.

[0048] In a further advantageous embodiment of the control unit, the two voltage domains can be galvanically isolated from each other by an isolation transformer. The first voltage domain, with the higher nominal voltage, can be connected to a primary side of the isolation transformer, and the second voltage domain, with the lower nominal voltage, can be connected to a secondary side of the isolation transformer.

[0049] The claimed measuring arrangement describes the detection of a short circuit to the vehicle ground. Since both voltage sources, for example R. 418155

[0050] - 10 -

[0051] Since a 12V and a 48V power supply in the vehicle can each have their own reference potential / ground potential, a common ground potential can be formed by connecting the two masses via a resistor.

[0052] Alternatively, one of the two reference potentials or ground connections can be raised to a higher voltage level in order to clearly deduce the type of short circuit from the measured (second) voltage. For example, a short circuit between the two ground connections can be detected if they are at different voltage levels. Optionally, by selectively raising one ground connection (or reference potential) of the two voltage domains in a (first) test run, it can be determined in which voltage domain a short circuit has occurred.

[0053] The measuring arrangement claimed herein can detect a fault source during the operation of different voltage domains or switching areas with varying voltage supplies. By configuring the circuit and selectively connecting the reference potentials and potentials of both voltage domains, the type of fault, and in particular the type of short circuit, can be determined. To identify the fault and / or short circuit, a targeted change in at least one of the reference potentials can also be performed, for example, by using the potential of the other voltage domain or an additional test current.

[0054] Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description. In the drawings, identical reference numerals denote components or elements that perform the same or analogous functions.

[0055] Brief description of the drawings

[0056] Fig. 1 shows a schematic representation of a first embodiment of a known control unit with two voltage domains, each comprising a voltage source and different nominal voltages. R. 418155

[0057] - 11 -

[0058] Fig. 2 shows a schematic representation of a second embodiment of a known control unit with two galvanically isolated voltage domains, each comprising a voltage source and different nominal voltages.

[0059] Fig. 3 shows a schematic representation of an embodiment of a control unit according to the invention with two galvanically isolated voltage domains, each comprising a voltage source and different nominal voltages, and an embodiment of a measuring arrangement according to the invention for fault detection in a control unit.

[0060] Fig. 4 shows a schematic representation of a second embodiment of a control unit according to the invention with two galvanically isolated voltage domains, each comprising a voltage source and different nominal voltages, and a second embodiment of a measuring arrangement according to the invention for fault detection in a control unit.

[0061] Embodiments of the invention

[0062] As can be seen from Figs. 3 and 4, the illustrated embodiments of a control unit 1 according to the invention for a vehicle each comprise two galvanically isolated voltage domains 3, 5, each comprising a voltage source 4, 6 and different nominal voltages U1, U2, and a measuring arrangement 10 according to the invention for fault detection.

[0063] As can be further seen from Figures 3 and 4, the illustrated embodiments of the measuring arrangement 10 according to the invention for fault detection in a control unit 1 each comprise an ohmic resistor Rp, which is connected between the two galvanically isolated voltage domains 3, 5 and connects the reference potentials of the two voltage sources 4, 6 of the two galvanic voltage domains 3, 5, a first measuring device 11, which is designed to determine a first measuring voltage UM1 across the ohmic resistor Rp caused by a current flow, and a further ohmic resistor Rpu, which in a first test operation is connected via an R. 418155

[0064] - 12 -

[0065] Switching element S connects a potential of a first nominal voltage U1 of a higher first voltage domain 3 with a reference potential of a second nominal voltage U2 of a lower second voltage domain 5, at least a second measuring device 12, which is configured to detect a second measuring voltage UM2 between at least one connection pin 9 of the lower second voltage domain 5 and a reference potential of the first nominal voltage U1 of the higher first voltage domain 3 in the first test operation, and an evaluation and control unit 16, which is configured to evaluate the first measuring voltage UM1 at the ohmic resistor Rp in normal operation, to activate the first test operation and to evaluate the second measuring voltage UM2 at the further ohmic resistor Rpu in the first test operation and to detect several short circuit types in the control unit 1 depending on the evaluation.

[0066] As can be seen in Figures 3 and 4, a first voltage source 4 of a first voltage domain 3 has a first nominal voltage U1 of 48 volts in both the first embodiment of control unit 1C shown in Figure 3 and the second embodiment of control unit 1B shown in Figure 4. This first nominal voltage U1 is higher than a second nominal voltage U2 of 12 volts of a second voltage source 6 of a second voltage domain 5. Furthermore, the two voltage domains 3 and 5 are galvanically isolated from each other by an isolation transformer (not shown in detail). The illustrated embodiments of the measuring arrangement 10 each comprise a first measuring device 11 and a second measuring device 12. As can be seen in Figures 3 and 4, the two measuring devices 11 and 12 in the illustrated embodiments of the measuring arrangement 10 are each designed as voltmeters and directly measure the respective measuring voltages UM1 and UM2.

[0067] As can be seen from Figures 3 and 4, both the first embodiment of the measuring arrangement 10A shown in Figure 3 and the second embodiment of the measuring arrangement 10B shown in Figure 4 each comprise a multiplexer 14, which in the illustrated embodiments of the measuring arrangement 10 each comprises one input and three outputs. The input of the multiplexer 14 is connected to the second measuring device 12, and the three outputs are each connected to a pin 9 of the lower second measuring device. 418155

[0068] - 13 -

[0069] Voltage domain 5 is connected. Thus, a first output of the multiplexer 14 is connected to a first pin 9A of the lower second voltage domain 5. A second output of the multiplexer 14 is connected to a second pin 9B of the lower second voltage domain 5, and a third output of the multiplexer 14 is connected to a third pin 9C of the lower second voltage domain 5. Therefore, the second measuring device 12 can be electrically connected to several pins 9 of the lower second voltage domain 5 via the switchable multiplexer 14. In the illustrated embodiments of the measuring arrangement 10, three pins 9 are shown as examples, which can be electrically connected to the second measuring device 12 via the multiplexer 14.In the illustrated embodiments of the measuring arrangement 10, the evaluation and control unit 16 is further designed to control the switchable multiplexer 14 during the first test operation such that the second measuring device 12 is successively electrically connected to the individual connection pins 9 of the lower second voltage domain 5. Preferably, the second measuring device 12 can be successively electrically connected to the individual connection pins 9 of the lower second voltage domain 5 in a predetermined sequence.

[0070] In the illustrated embodiments of the measuring arrangement 10, the evaluation and control unit 16 detects a first short circuit 7 between the two voltage domains 3, 5 during normal operation when the first measuring voltage UM1 caused by a short-circuit current Ik at the ohmic resistance Rp exceeds a first threshold value, which is specified, for example, in the range of 15 volts to 20 volts.

[0071] In the first test operation, the evaluation and control unit 16 detects a second short circuit between the corresponding connection pin 9 of the lower second voltage domain 5 and the reference potential of the first nominal voltage U1 of the higher first voltage domain 3 or the reference potential of the second nominal voltage U2 of the lower second voltage domain 5, if the second measured voltage UM2 across the further ohmic resistor Rpu falls below a second threshold value, which is predefined, for example, in the range of 0.1 volts to 1 volt. Alternatively, the evaluation and control unit R. 418155

[0072] - 14 -

[0073] 16 detects a third short circuit between the corresponding terminal 9 of the lower second voltage domain 5 and the potential of the second nominal voltage U2 of the lower second voltage domain 5 when the second measured voltage UM2 across the further ohmic resistor Rpu exceeds the second threshold and falls below a third threshold, which can be predefined, for example, in the range of 14 volts to 20 volts. Furthermore, the evaluation and control unit 16 detects a fourth short circuit between the corresponding terminal 9 of the lower second voltage domain 5 and the potential of the first nominal voltage U1 of the higher first voltage domain 3 when the second measured voltage UM2 across the further ohmic resistor Rpu exceeds the third threshold.

[0074] As can be further seen from Fig. 4, the illustrated second embodiment of the measuring arrangement 10B, unlike the embodiment of the measuring arrangement 10A shown in Fig. 3, comprises a current source 14 which is configured to generate a test current IT through the ohmic resistor Rp in a second test operation. The evaluation and control unit 16 is further configured to activate the second test operation and to verify the functionality of the ohmic resistor Rp in the second test operation.

[0075] In the second embodiment of the measuring arrangement 10B shown, the evaluation and control unit 16 is further designed to detect the ohmic resistance Rp as faulty during test operation if the first measurement voltage UM1 across the ohmic resistance Rp, caused by the test current IT, is below a lower fourth threshold, which is predefined, for example, in the range of 0.1 volts to 1 volt, or above a higher fifth threshold, which is lower than the first threshold and is predefined, for example, in the range of 9 volts to 12 volts. Alternatively, the ohmic resistance Rp is detected as fault-free if the first measurement voltage UM across the ohmic resistance Rp, caused by the test current IT, is greater than or equal to the fourth threshold and less than or equal to the fifth threshold.In the illustrated second embodiment of the measuring arrangement 10B, the ohmic resistor Rp is recognized as fault-free if the first measuring voltage UM1 across the ohmic resistor Rp is in the range between 1 volt and 9 volts. Here, the R. 418155.

[0076] - 15 -

[0077] In test mode, the evaluation and control unit 16 detects a short circuit of the ohmic resistance Rp if the first measurement voltage UM1 across the ohmic resistance Rp caused by the test current IT is below the fourth threshold. Alternatively, in the second test mode, the evaluation and control unit 16 detects an open ohmic resistance Rp if the first measurement voltage UM1 across the ohmic resistance Rp caused by the test current IT is above the fifth threshold.

[0078] In the illustrated embodiments of the measuring arrangement 10, the evaluation and control unit 16 is further configured to activate the test operation initially or cyclically for a predetermined time period. Furthermore, the evaluation and control unit 16 is configured to suspend the test operation if a short circuit 7 between the two voltage domains 3 and 5 is detected.

[0079] In the illustrated embodiments of the measuring arrangement 10, the evaluation and control unit 16 is further designed to generate and output corresponding error messages about the types of short circuits detected in the control unit 1 and / or about a lack of functionality of the ohmic resistance Rp.

[0080] In the illustrated embodiments of the measuring arrangement 10, the ohmic resistor Rp provides a high-impedance reference potential. For this purpose, the ohmic resistor Rp has a value in the range of 1 kilohm to 5 kilohm. Furthermore, the ohmic resistor Rp limits the short-circuit current Ik. The additional ohmic resistor Rpu raises the reference potential of the second nominal voltage U2 of the lower second voltage domain 5 during the first test operation and also has a value in the range of 1 kilohm to 5 kilohm.

[0081] As can be seen from Figs. 3 and 4, a capacitor Cp is connected in parallel to the ohmic resistor Rp and designed to reduce EMC interference.

Claims

R. 418155 - 16 - Claims 1. Measuring arrangement (10) for fault detection, in particular for the detection of a short circuit, in a control unit (1 C) with two galvanically isolated voltage domains (3, 5), each comprising a voltage source (4, 6) and different nominal voltages (U1, U2), comprising an ohmic resistor (Rp) which is connected between the two galvanically isolated voltage domains (3, 5) and connects reference potentials of the two voltage sources (4, 6) of the two voltage domains (3, 5) to each other, at least a first measuring device (11) which is configured to determine a first measuring voltage (UM1) across the ohmic resistor (Rp) caused by a current flow, and a further ohmic resistor (Rpu) which, in a first test operation, connects a potential of a first nominal voltage (U1) of a higher first voltage domain (3) to a reference potential of a second nominal voltage (U2) of a lower second voltage domain (5) via a switching element (S).at least a second measuring device (12) configured to detect a second measuring voltage (UM2) between at least one connection pin (9) of the lower second voltage domain (5) and a reference potential of the first nominal voltage (U1) of the higher first voltage domain (3) during the first test operation, and an evaluation and control unit (16) configured to evaluate the first measuring voltage (UM1) at the ohmic resistor (Rp) during normal operation, to activate the first test operation, and to evaluate the second measuring voltage (UM2) at the further ohmic resistor (Rpu) during the first test operation, and to detect several short circuit types in the control unit (1) depending on the evaluation.

2. Measuring arrangement (10) according to claim 1, characterized in that the at least one second measuring device (12) is connected via a R. 418155 - 17 - The switchable multiplexer (14) is electrically connected to several connection pins (9) of the lower second voltage domain (5).

3. Measuring arrangement (10) according to claim 2, characterized in that the evaluation and control unit (16) is further designed to control the switchable multiplexer (14) in the first test operation such that the at least one second measuring device (12) is successively electrically connected to the individual connection pins (9) of the lower second voltage domain (5).

4. Measuring arrangement (10) according to claim 3, characterized in that the evaluation and control unit (16) is further designed to control the switchable multiplexer (14) in the first test operation such that the at least one second measuring device (12) is electrically connected in a predetermined sequence to the individual connection pins (9) of the lower second voltage domain (5).

5. Measuring arrangement (10) according to one of claims 1 to 4, characterized in that the evaluation and control unit (16) detects a first short circuit (7) between the two voltage domains (3, 5) during normal operation when the first measuring voltage (UM1) caused by a short-circuit current (Ik) at the ohmic resistance (Rp) exceeds a first threshold value.

6. Measuring arrangement (10) according to one of claims 1 to 5, characterized in that the evaluation and control unit (16) detects, during the first test operation, a second short circuit between the corresponding terminal pin (9) of the lower second voltage domain (5) and the reference potential of the first nominal voltage (U1) of the higher first voltage domain (3) or the reference potential of the second nominal voltage (U2) of the lower second voltage domain (5), if the second measuring voltage (UM2) across the further ohmic resistance (Rpu) falls below a second threshold value, or a third short circuit between the corresponding terminal pin (9) of the lower second voltage domain (5) and the potential of the R. 418155 - 18 - second nominal voltage (U2) of the lower second voltage domain (5) detects when the second measurement voltage (UM2) at the further ohmic resistance (Rpu) exceeds the second threshold and falls below a third threshold, or a fourth short circuit between the corresponding terminal pin (9) of the lower second voltage domain (5) and the potential of the first nominal voltage (U1) of the higher first voltage domain (3) is detected when the second measurement voltage (UM2) at the further ohmic resistance (Rpu) exceeds the third threshold.

7. Measuring arrangement (10) according to one of claims 1 to 6, characterized in that a current source (14) is configured to generate a test current (IT) through the ohmic resistance (Rp) in a second test operation, wherein the evaluation and control unit (16) is further configured to activate the second test operation and to check the functionality of the ohmic resistance (Rp) in the second test operation.

8. Measuring arrangement (10) according to claim 7, characterized in that the evaluation and control unit (16) is further designed to recognize the ohmic resistance (Rp) as faulty in the second test operation if the first measuring voltage (UM1) across the ohmic resistance (Rp) caused by the test current (IT) is below a smaller fourth threshold or above a larger fifth threshold which is smaller than the first threshold, or to recognize the ohmic resistance (Rp) as fault-free if the measuring voltage (UM) across the ohmic resistance (Rp) caused by the test current (IT) is greater than or equal to the fourth threshold and less than or equal to the fifth threshold.

9. Measuring arrangement (10) according to claim 8, characterized in that the evaluation and control unit (16) detects a short circuit of the ohmic resistance (Rp) in the second test operation if the first measuring voltage (UM1) across the ohmic resistance (Rp) caused by the test current (IT) is below the fourth threshold value, or an open circuit. 418155 - 19 - The ohmic resistance (Rp) detects when the first measurement voltage (UM1) across the ohmic resistance (Rp) caused by the test current (IT) is above the fifth threshold.

10. Measuring arrangement (10) according to one of claims 1 to 9, characterized in that the evaluation and control unit (16) is further designed to activate the first test operation and / or the second test operation initially or cyclically for a predetermined period of time.

11. Measuring arrangement (10) according to one of claims 1 to 10, characterized in that the evaluation and control unit (16) is further designed to suspend the test operation when the first short circuit (7) between the two voltage domains (3, 5) is detected.

12. Measuring arrangement (10) according to one of claims 1 to 11, characterized in that the evaluation and control unit (16) is further designed to generate and output corresponding error messages about the types of short circuits detected in the control unit (1) and / or about a lack of functionality of the ohmic resistance (Rp).

13. Measuring arrangement (10) according to one of claims 1 to 12, characterized in that the ohmic resistance (Rp) provides a high-impedance reference potential and has a value in the range of 1 kiloohm to 5 kiloohm.

14. Measuring arrangement (10) according to one of claims 1 to 13, characterized in that the further ohmic resistance (Rpu) raises the reference potential of the second nominal voltage (U2) of the lower second voltage domain (5) in the first test operation and has a value in the range of 1 kiloohm to 5 kiloohm.

15. Measuring arrangement (10) according to one of claims 1 to 14, characterized in that the ohmic resistance (Rp) limits the resulting short-circuit current (Ik). R. 418155 - 20 - 16. Measuring arrangement (10) according to one of claims 1 to 15, characterized in that a capacitor (Cp) is connected in parallel to the ohmic resistor (Rp), which is designed to reduce EMC interference.

17. Control unit (1) for a vehicle, comprising two galvanically isolated voltage domains (3, 5), each comprising a voltage source (4, 6) and different nominal voltages (U1, U2), and a measuring arrangement (10) for fault detection, which is designed according to one of claims 1 to 16.

18. Control unit (1) according to claim 17, characterized in that a first nominal voltage (U1) of a first voltage source (4) of a first voltage domain (3) is higher than a second nominal voltage (U2) of a second voltage source (6) of a second voltage domain (5).

19. Control unit (1 ) according to claim 17 or 18, characterized in that the two voltage domains (3, 5) are galvanically isolated from each other by a transformer.

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