Device for supplying energy to a controller of a motor vehicle

Abstract

The invention relates to a device for supplying energy to a controller (18) of a motor vehicle, wherein: a controller (18) comprises at least two ground connections (41, 42) for contacting one vehicle ground (50) each; at least one disconnecting means (44) is provided in the controller (18) between the two ground connections (41, 42); at least one of the ground connections (41) is directly electrically conductively connected to an internal controller ground (52) while the other ground connection (42) is connected to the internal controller ground (52) via the disconnecting means (44); and the disconnecting means (44) is designed to prevent a compensating current between the two ground connections (41, 42) within a specific range of a voltage drop (U_gnd) between the two ground connections (41, 42).

Description

[0001] Description

[0002] title

[0003] Device for supplying energy to a control unit of a motor vehicle

[0004] The invention relates to a device for supplying energy to a control unit of a motor vehicle according to the preamble of the independent claim.

[0005] State of the art

[0006] DE 102016102248 A1 discloses a device for detecting a ground fault in a first ground line of a first power supply of a vehicle's steering system. The first power supply has a first ground potential. A first means for measuring a current is provided, wherein the means is arranged in the first ground line and wherein the first means is suitable for checking the connection of the first ground potential to the first ground line.

[0007] DE 102020205734 A1 discloses an electrical assembly with two ground terminals. A component is provided for connecting a second ground terminal to a first load, which component is configured to generate a predetermined voltage drop. The assembly may comprise a device for determining a current flowing through the second ground terminal and a control device for controlling a current drawn by the assembly depending on the determined current.

[0008] The invention is based on the object of providing a device characterized by increased safety. This object is achieved by the features of the independent claim. Disclosure of the invention

[0009] By providing two ground connections, the supply reliability and availability of the control unit can be increased. On the other hand, with advantageous wiring and evaluation, the isolating agent ensures that particularly dormant errors such as the failure of one or more ground lines can be reliably diagnosed and detected. This is particularly important when there are stringent safety requirements, particularly ASIL requirements (for example, according to DIN ISO 26262), as they arise, for example, when supplying safety-relevant consumers. For this purpose, a first or primary ground connection is directly electrically connected to the internal control unit ground, while the other, secondary ground connection is connected via the isolating agent.This allows the additional ground connection to be checked, which also allows conclusions to be drawn about the functionality of the primary ground connection. Furthermore, a compensating current in the event of a ground misalignment is prevented to a certain extent. Preferably, a compensating current between the two ground connections can be prevented up to a certain small voltage difference between the two ground connections.

[0010] In a useful development, the additional ground connection can be supplied with a voltage, in particular an internal supply voltage of the control unit for supplying components of the control unit, and / or with an impressed current for diagnosing a fault. In the event of an interruption at the additional ground connection, the voltage drop at the additional ground connection is correspondingly influenced by this voltage, so that a corresponding evaluation can reliably identify the associated fault. The evaluation means is particularly useful in concluding a fault if the detected value of the voltage drop at the additional ground connection deviates from zero and / or lies in the range of the applied voltage, in particular the supply voltage. This allows different faults such as an interruption of one ground connection or the interruption of the additional ground connection to be reliably diagnosed.In a useful development, at least one limiting device such as a Zener diode, particularly preferably a bidirectional Zener diode such as a bidirectional TVS diode, is connected in parallel with the isolating device. This further prevents damage caused, for example, by overvoltages or reversed polarity. For example, in the event of reversed polarity, a negative current can continue to flow via the internal control unit ground, which is necessary for an activation circuit to protect, in particular, a body diode of a MOSFET. On the other hand, the diagnostic result is not corrupted by a parasitic current, since a corrupting current flow through the limiting device is avoided thanks to a bidirectional Zener diode.

[0011] In an expedient development, at least one threshold value is designed to be variable depending on the voltage drop at the further ground connection of the control unit, wherein at least one switch unit for controlling at least one safety-relevant consumer and / or at least one trend switch for connecting or disconnecting the sub-vehicle networks is activated depending on a comparison of a characteristic value with the threshold value, in particular when the voltage drop falls below the threshold value. A voltage drop between the internal control unit ground and the vehicle ground that occurs when the ground line fails can be specifically taken into account by adjusting the threshold value accordingly. This allows undervoltage disconnection to be maintained unchanged even in the event of a fault. This further increases the safety during operation of safety-relevant consumers in particular.

[0012] In a useful development, the internal supply voltage can be connected to the potential of the additional ground connection via at least one switching device and / or at least one limiting device, in particular a Zener diode. This allows a cyclic check of the additional ground connection and can thus contribute to a reduction in the quiescent current.

[0013] In a practical development, the isolating means is configured such that, during fault-free operation, particularly when the ground connections are properly connected to a vehicle ground, a current flows from the internal control unit ground only via the directly connected ground connection. Particularly preferably, the isolating means is configured such that, during faulty operation, a current flows from the internal control unit ground via the additional ground connection. This contributes to improved diagnostic capabilities and, due to the redundancy of the ground connections, also increases the availability of the control unit.

[0014] In a suitable further development, at least one detection means, in particular a voltage divider, is provided for detecting a measure of a voltage drop at the additional ground connection. The voltage drop at the additional ground connection provides a suitable basis for evaluation for various fault scenarios.

[0015] In a suitable further development, at least one evaluation device is provided that evaluates the detected voltage drop at the additional ground connection, particularly via an analog-to-digital converter, and compares it with a limit value. This allows for flexible evaluation options for different fault scenarios.

[0016] In a useful further development, the isolating means is designed such that, if the voltage drop between the additional ground terminal and the ground terminal to which the internal control unit ground is directly connected is greater than zero, a compensating current between the additional ground terminal and the ground terminal is prevented, and / or if the voltage drop is less than zero and / or less than a limit value, a compensating current from the internal control unit ground to the additional ground terminal via the isolating means is prevented. In particular, when a diode is used as the isolating means, compensating currents between the two ground terminals can be completely prevented in blocking mode, and in forward mode at least up to a low voltage threshold (forward voltage of the diode or forward voltages of several diodes connected in series).This can reduce damage, particularly to the components of the control unit, by preventing corresponding compensating currents. In a practical development, the isolating agent is designed as a diode and / or the ground connection is connected to an anode of a isolating agent designed as a diode and / or the further ground connection is connected to a cathode of a isolating agent designed as a diode and / or the isolating agent comprises several diodes connected in series. This makes it particularly easy to achieve the desired safety and diagnostic capability with a simple electronic component. By connecting several diodes in series, the voltage range within which the compensating current is to be prevented can also be set. This increases flexibility according to the respective individual requirements.

[0017] In a practical development, it is provided that at least the evaluation unit, in particular a microcontroller, and / or at least one gate driver for controlling at least one switch unit for a particularly safety-relevant consumer and / or an emergency operation logic and / or a measuring device and / or an infrastructure or supply and / or at least one electronic component is / are connected to the control unit ground. This means that particularly safety-relevant components for operation or the power supply for the safety-relevant consumer are redundantly protected via the corresponding ground connections and can be specifically diagnosed. This further increases reliability.

[0018] Further useful developments arise from further dependent claims and from the description.

[0019] Short description of the drawing

[0020] Figure 1 shows an example of an embodiment of the power distributor that connects two sub-vehicle networks,

[0021] Figure 2 shows a schematic diagram of an embodiment and

[0022] Figure 3 shows a schematic diagram of another embodiment. Embodiment of the invention

[0023] The invention is illustrated schematically using an embodiment and is described in detail below with reference to the drawing.

[0024] Figure 1 shows a possible topology of an energy supply system consisting of an on-board electrical system 13, which includes an energy storage device 12, in particular a battery 12 with an associated sensor 14, preferably a battery sensor, as well as a plurality of, in particular, safety-relevant consumers 16, which are supplied and protected by a control unit 18 preferably designed as an electrical power distributor. A control unit 18 is suitable for supplying safety-relevant consumers 16 and is characterized by a particularly fault-tolerant design in that at least two ground connections 41, 42 are provided on the control unit 18. One ground connection 41 is connected to a vehicle ground 50 via a first ground cable 43, and the other ground connection 42 is connected to a vehicle ground 50 via a further ground cable 45. The two ground connections 41, 42 are connected to one another via a separator 44, in particular a diode.One ground connection 41 is directly connected to an internal ground 52 of the control unit 18 or power distributor 18. All essential components of the control unit 18 are supplied via the internal ground 52 or control unit ground 52. Examples include gate driver 31, emergency operation logic 32, measuring device 33 (for measuring, for example, current I, voltage U, temperature T or other quantities of interest), additional infrastructure or supplies 34, a chip or electronic component 35 on which the system basis is implemented, and also an evaluation or control device 21, such as a microcontroller 21. The gate driver 31 receives signals from the microcontroller 21 and / or the emergency operation logic 32 and controls the switching means 15 accordingly.

[0025] The loads 16 are special loads with high requirements or a high protection need, generally referred to as safety-relevant loads 16. These include, for example, an electric steering system and / or a braking system as components that absolutely must be supplied to ensure the steering and / or braking of the vehicle in the event of a fault. Parameters of the respective load 16 are recorded separately. If there is a deviation from tolerable values, the corresponding switch 15 is opened. The vehicle electrical system 13 consists of a safety-relevant sub-system 11 and a non-safety-relevant sub-system 10. The safety-relevant sub-system 11 can be separated from the non-safety-relevant sub-system 10 by the power distributor 18, particularly in the event of a fault or a critical condition of the non-safety-relevant sub-system 10.The safety-relevant sub-system 11 is, for example, an ASIL-qualified sub-system 11, in particular ASIL C (for example, according to DIN ISO 26262), which comprises at least one of the safety-relevant consumers 16 and can optionally be equipped with its own energy storage device 12 for voltage support. The non-safety-relevant sub-system 10 comprises at least one non-safety-relevant consumer 17, for example, this can be a so-called QM consumer or a consumer whose safety integrity is rated QM. However, it is not excluded that at least one further safety-relevant consumer can be arranged in the non-safety-relevant sub-system 10, for example in the case of a redundant design of the safety-relevant consumers. The non-safety-relevant sub-system 10 is a non-ASIL-qualified electrical system.

[0026] The energy storage device 12 is connected to a connection (terminal KL30_1) of the power distributor 18. The sensor 14 is capable of detecting an electrical parameter such as a voltage Ub at the energy storage device 12 and / or a current Ib through the energy storage device 12 and / or a temperature Tb of the energy storage device 12. The sensor 14 can determine, for example, the state of charge SOC of the energy storage device 12 or other parameters of the energy storage device 12 from the determined electrical parameters Ub, Ib, Tb. At the further connection (KL 30_1) of the power distributor 18, to which the energy storage device 12 is also connected, an additional supply branch for at least one additional consumer 25 can optionally be provided. The consumer 25 is, for example, protected by a fuse 23. Further consumers 25 can also be provided, which can also be protected by fuses 23.These loads 25 are those that should continue to be supplied with energy from the energy storage device 12 even when the switching device 19 in the power distributor 18 is disconnected or opened. These loads are preferably safety-critical loads 25 that are critical in terms of disruptions related to supply reliability or loads classified as QM that must meet certain requirements after an accident. Thus, an (optional) safety-relevant or safety-critical on-board power system path or sub-on-board power system 11 is connected to the terminal KL 30 _1.

[0027] The control unit 18 can be able to determine corresponding parameters such as voltage Uv, current Iv of the consumers 16 via the measuring device 33. The power distributor 18 can determine corresponding parameters of the energy storage device 12 such as voltage Ub and / or current Ib and / or temperature Tb. For this purpose, the power distributor 18 could contain the corresponding sensors or receive the data from the sensor 14. The power distributor 18 also has corresponding evaluation means 21 such as the microcontroller 21 to store or evaluate recorded variables. The evaluation means 21 serves to determine critical states, in particular of the safety-relevant sub-vehicle network 11, such as detecting an overcurrent and / or an undervoltage or overvoltage at the sub-vehicle network 11 for the safety-relevant consumers 16, 25. For this purpose, corresponding parameters are recorded and compared with suitable threshold values.A microcontroller, for example, is used as the evaluation device 21. The microcontroller or the evaluation device 21 is also capable of controlling corresponding switching units 15 via the gate driver 31. A switching unit 15 supplies the connected safety-relevant load 16 with energy provided via a distribution point, e.g., busbar 60 or backbone, or the supply voltage U1, via an output 66. For example, three switching units 15 are provided, each supplying the corresponding safety-relevant loads 16 with energy via the outputs 66. The safety-relevant loads 16 are connected to the vehicle ground 50. The other loads 17, 25, 26 are also connected to the vehicle ground 50.

[0028] Optionally, a disconnect switch 19 can be arranged between terminal KL30_0 and terminal KL30_1 in the control unit 18 designed as a power distributor. The optional disconnect switch 19 can be used to implement a corresponding disconnection or coupling function, particularly for the two vehicle electrical system branches (sub-vehicle electrical system 10 for non-safety-relevant consumers 17 at terminal KL 30_0; further sub-vehicle electrical system 11 for safety-relevant consumers 16, 25). This serves, in particular, as a safety function to prevent the effects of critical conditions such as overvoltages or undervoltages and / or overcurrents and / or thermal overload. In the event of a fault, the two vehicle electrical systems 10, 11 can be disconnected from one another by the control unit 18 designed as a power distributor by opening the disconnect switch 19. The disconnect switch 19 could comprise parallel-connected switching devices for a fail-safe supply.

[0029] The on-board electrical system 13 has a lower voltage level U1 than an optionally provided high-voltage on-board electrical system 20; for example, it could be a 14 V on-board electrical system. A DC-DC converter 22 is arranged between the on-board electrical system 13 and the high-voltage on-board electrical system 20. The high-voltage on-board electrical system 20 includes, for example, an energy storage device 24, for example a high-voltage battery, possibly with an integrated battery management system, a load 26 shown as an example, for example a comfort consumer such as an air conditioning system or refrigerant compressor etc. supplied with a higher voltage level, and an electric machine 28. In this context, high voltage is understood to mean a voltage level U2 that is higher than the voltage level U1 of the basic on-board electrical system 13. For example, it could be a 48 V on-board electrical system. Alternatively, especially in vehicles with electric drive, it could be even higher voltage levels, for example 400 V or 800 V.Alternatively, the high-voltage electrical system 20 could be omitted altogether.

[0030] By way of example, a battery or accumulator is described in the embodiment as a possible energy storage device 12, 24. Alternatively, however, other energy storage devices suitable for this task, for example, inductive or capacitive energy storage devices, fuel cells, capacitors, or similar, can equally be used.

[0031] According to Figure 2, the control unit 18 comprises at least one ground connection 41 and another ground connection 42. One ground connection 41 of the control unit 18 is connected to the vehicle ground 50 via one ground cable 43, and the other ground connection 42 is connected to the vehicle ground 50 via the further ground cable 45. The two ground connections 41, 42 are electrically separated from one another to a certain extent by the isolating means 44 arranged in the control unit 18. The first ground connection 41 is connected to the internal control unit ground 52. Furthermore, the first ground connection 41 is electrically conductively connected to the isolating means 44, in particular to an anode of a isolating means 44 designed as a diode. The further ground connection 42 is connected to another connection of the isolating means 44, in particular to a cathode of a isolating means 44, preferably designed as a diode.The common potential of the further ground connection 42 and the connection of the isolating means 44 is connected to a resistor 46, in particular a so-called pull-up resistor. The resistor 46, in particular a pull-up resistor, for example in the order of magnitude of 1 kOhm, is fed via a connection 48 with a supply voltage Up, for example in the order of magnitude of 5 V, in particular the pull-up supply voltage. The voltage Up or supply voltage Up can, for example, be an internal supply voltage Up of the control unit 18 for supplying certain electronic components of the control unit 18. This internal supply voltage Up is derived, for example, by suitable voltage converters or the like from the supply voltage of the on-board electrical system and usually differs from the supply voltage for the consumers 16, 25.The potential of the additional ground connection 42, which is connected to both a connection of the isolating agent 44 and to the resistor 46, is tapped as the voltage U to be evaluated for diagnostic purposes, relative to the internal control unit ground 52. The pull-up resistor 46 should, for example, be less than 5 kOhm (e.g., 1 kOhm) so that a dirt resistance at the connector pin (usually also around 5 kOhm) cannot falsify the diagnostic result. The supply voltage 60 should exceed a possible ground offset (e.g., 1.5 V - without a fault in the ground lines) (plus a certain reserve). For example, the supply voltage 60 should be in the range greater than 3 V.

[0032] As an example, an evaluation circuit 53 is shown for the evaluation or voltage measurement of the voltage U, i.e. the voltage U at the further ground connection 42. The measurement for this voltage U is suitable for diagnosing whether the ground cables 43, 45 are correctly connected to the associated ground connections 41, 42 or the vehicle ground 50. The voltage U to be recorded and evaluated is fed to a voltage divider via a resistor 54, preferably a high-ohm resistor, for example in the order of magnitude of 10 kOhm. A wide range for the resistor 54 is possible. However, the value must be significantly greater than the resistor 46, the pull-up resistor, so that the test result is not falsified by the voltage measurement alone. The voltage divider consists of a resistor 58 which is connected to a supply voltage 60 (for example, a component of the infrastructure 34 orsupply 34 according to Figure 1), for example in the order of magnitude of 5 V or similar, and a further resistor 56 connected to the internal ground 52 of the control unit 18. The voltage measurement must cover the range of the supply voltage 60 (U_Pullup) in the positive direction and the possible diode voltage drop in the negative direction. The two resistors 56, 58 of the voltage divider are, for example, in the order of magnitude of 26 kOhm. The resistors 56, 58 should have high resistance so as not to influence the diagnostic result, i.e. significantly larger than the resistor 46, the pull-up resistor. Depending on the application or voltage level, the resistance values ​​can be adjusted accordingly. The common potential of the two resistors 56, 58 of the voltage divider and the resistor 54 are fed to an analog-to-digital converter 62.The measured voltage U is digitized and fed to the evaluation unit 21, such as the microcontroller 21. The options for error detection can be implemented in the evaluation unit 21 as described below. However, other evaluation options, for example, in analog form, are also possible.

[0033] In the event of a fault, a ground voltage U_gnd can drop between the two ground connections 41, 42, which is indicated by an arrow. In proper condition, the two ground connections 41, 42 are connected to the vehicle ground 50, for example corresponding ground connections on the body, via the respective ground cables 43, 45. To increase availability, the control unit 18 is supplied externally via two independent ground lines 43, 45, namely via the two ground connections 41, 42. The arrangement according to Figure 2 serves to separate the two ground connections 41, 42 and to avoid a compensating current in the event of a ground offset, as well as for diagnostics such as detecting the failure or interruption of a ground cable 43, 45.The diagnosis is particularly necessary with regard to functional safety (according to DIN-ISO 26262) with ASIL requirements for safe functions such as the described safe supply in an arrangement according to Figure 1 of the safety-relevant consumers 16.

[0034] This is achieved by the isolating means 44, which serves to provide a certain electrical separation between the two ground connections 41, 42 in the control unit 18. The isolating means 44 is preferably designed to prevent a compensating current between the two ground connections 41, 42 within a specific range of a voltage drop U_gnd between the two ground connections 41, 42. In the exemplary embodiment according to Figure 2, the isolating means 44 is implemented as a diode. The primary ground connection 41 is directly connected to the internal control unit ground 52 or electronics ground 52 in the control unit 18. The isolating means 44 prevents compensating currents between the two ground lines 43, 45 at the two ground connections 41, 42 in the range of a voltage difference of a few 100 mV in the forward direction of the diode or up to higher differences in the reverse direction.

[0035] By isolating it via the isolating means 44, preferably a diode, the further ground connection 42 or the secondary ground can be checked. Failure of the primary ground at the ground connection 41 can also be detected by a voltage drop at the isolating means 44 or the diode due to a current flow. For diagnosis, a positive voltage Up is applied to a terminal 48 of the resistor 46, in particular a pull-up resistor. A voltage measurement to determine a voltage U at the further ground connection 42 is required for diagnosis. The internal 5 V supply within the infrastructure 34 or a similar device such as a current source could be used as the voltage source for providing the supply voltage Up. The resistor 46 is connected to the terminal 48 for the supply voltage Up and to the further ground connection 42 orcommon potential of the further ground connection 42 is connected to the separating agent 44.

[0036] In vehicles, a ground offset can occur between different ground connections 41, 42, especially if they are not located close to each other on the body. The possible ground offset is described in Figure 2 by the voltage drop U_gnd. The voltage drop U_gnd can be positive or negative. Cross current from one ground connection 41, 42 to the other must be avoided, as the current flow can damage the ground cables 43, 45 or the connection on the circuit board of the control unit 18.

[0037] With the aid of the separating means 44, which is preferably designed as a diode, the control unit 18 becomes tolerant to a limited ground offset.

[0038] In the event that the voltage drop U_gnd between the two ground connections 41, 42 or the ground offset is greater than zero, the diode blocks as an example for the isolating means 44. Even a voltage drop U_gnd or ground offset of several volts does not lead to a compensating current between the grounds 41, 42.

[0039] In the event that the voltage drop U_gnd between the two ground terminals 41, 42 or the ground offset is less than zero, a compensating current begins to flow only when the diode, for example, the isolating device 44, enters the forward-conducting range. At lower voltages, such as 300 mV, a current flow is prevented. If this voltage limit is insufficient, two or more isolating devices 44 or diodes connected in series can also be used. This increases the switching threshold accordingly to higher voltage values, above which a compensating current flows between the two ground terminals 41, 42.

[0040] The arrangement shown in Figure 2 can be used as a diagnostic function for an interruption in a ground cable 43, 45 to a ground terminal 41, 42. Two error scenarios must be distinguished here: an interruption in the first ground path or in the ground cable 43 at the ground terminal 41, and an interruption in the further ground path or in the further ground cable 45 at the ground terminal 42, for example, in the case of defective cables.

[0041] Case 1: Detection of an interruption in the first ground path or ground cable 43 at ground connection 41: Normally, without a defective ground connection 41 or ground cable 43, the operating current flows from the internal control unit ground 52 or the ground network formed in the control unit 18 via the ground connection 41 or the primary ground from the control unit 18. The voltage U (as shown in Figure 2) at the further ground connection 42 is zero, since no current flows via the isolating agent 44 or the diode. If this path is interrupted, the ground current will flow via the isolating agent 44 or the diode and the further ground connection 42. The forward voltage generated at the diode as the isolating agent 44 can be detected by measuring the voltage U applied to the further ground connection 42. Compared to the internal reference or internal ground 52 or control unit ground 52, the voltage at U is negative, for example in the range of -0.7 V.

[0042] Case 2: Detection of an interruption in the further ground path or further ground cable 45 at the further ground connection 42: In a fault-free state, the further ground connection 42 is connected to the ground connection 41 via the body or vehicle ground 50; therefore, the voltage U is close to 0 V or within the range of a normal ground offset between the two ground cables 43, 45. The resistor 46 to the positive voltage source (at terminal 48) does not change the voltage U, since the impressed current simply flows away via the further ground connection 42. In the event of an interruption at the further ground connection 42, the resistor 46 (pull-up resistor) succeeds in pulling the voltage U upwards. Therefore, if the voltage U is close to the supply voltage (Up) of the resistor 46, there is an interruption at the further ground connection 42. The isolating means 44 in the form of the diode blocks in this case.

[0043] Overview table for diagnosis:

[0044] In the exemplary embodiment, for example, the ground connection 41 or the ground cable 43 is defective if the voltage U at the further ground connection 42 is less than -200mV...-1V.

[0045] In the exemplary embodiment, for example, the further ground connection 42 or the further ground cable 45 is defective if the voltage U at the further ground connection 42 is greater than 2V...3V.

[0046] The threshold values ​​mentioned as examples above which an error is detected can be temperature-dependent.

[0047] For both error cases, the diagnosis can be performed once per drive cycle or continuously. Continuous monitoring may be necessary, especially with high ASIL requirements.

[0048] Alternatively, the separating means 44 could be implemented, for example, by means of corresponding electronic switches or the like, which only allow a current flow in one direction above a certain voltage drop.

[0049] In the exemplary embodiment according to Figure 3, the ground connection 41 of the control unit 18 is directly connected to the internal control unit ground 52. The isolating means 44, in particular an anode of at least one diode 44.1, 44.2, 44.3 as a possible isolating means 44, is contacted at the common potential of the internal control unit ground 52 and the ground connection 41. A connection of a limiter 51, which is connected in parallel to the isolating means 44, is at the same potential. The other connection of the isolating means 44 (the cathode of at least one of the series-connected diodes 44.1, 44.2, 44.3) and the other connection of the limiter 51 are at the same electrical potential, as are the further ground connection 42 of the control unit 18 and a connection of the resistor 46 (pull-up resistor). This common potential, related to the control unit ground 52, forms the voltage II to be evaluated, as represented by a circle.This voltage U to be evaluated is fed to the evaluation circuit 53 (as shown in more detail in Figure 2). The other terminal of the resistor 46 is connected to a limiting means 47, in particular a voltage limiting means, in particular to a cathode of a Zener diode. The other terminal of the limiting means 47 is connected via an optional switching means 49 to the terminal 48 for the supply voltage Up or pull-up voltage. The Zener diode as a limiting means 47 actually has no function when an internal supply voltage Up is connected for the pull-up resistor 46. It must simply not conduct any parasitic current during the activation of the pull-up Up or diagnosis. For this purpose, the Zener voltage should be above the diagnostic voltage used.

[0050] The embodiment according to Figure 3 differs from that of Figure 2 in that the separating means 44 comprises at least a first separating means 44.1 and at least one further separating means 44.2, which are connected in series. In the embodiment according to Figure 3, the two separating means 44.1, 44.2 are again designed as diodes. Optionally, a third separating means 44.3 can also be provided.

[0051] To reliably distinguish a proper operating condition from a fault with an interrupted ground cable 43, a larger distance between the two voltage ranges supplied to the evaluation circuit 53 is helpful. For this purpose, the current flow through the isolating devices 44.1, 44.2 (and their forward voltage when using diodes) must be distinguished from the correct current flow through the ground cable 43.

[0052] An additional ground offset in the body between the ground connections 41, 42 for the two ground cables 43, 45, or on the cables themselves, also influences the diagnostic result. Particularly with a negative voltage U_GND, the fault (ground cable 43 interrupted) may be incorrectly detected too early.

[0053] By the several proposed in the embodiment according to Figure 3

[0054] Isolating means 44.1, 44.2, 44.3 or, for example, the multiple diodes, can compensate for an additional ground offset in order to obtain a robust distinction between the fault case and the proper operating state.

[0055] In the embodiment shown in Figure 3, a limiter 51, for example in the form of a bidirectional TVS diode, is connected in parallel with the isolating means 44. In the event of a fault with a broken ground cable 43, the control unit 18 must fully function and also be robust against specific operating conditions. For this purpose, it is necessary for the circuit to allow a current flow toward the ground 52 of the control unit 18 even at negative supply voltages. This may be necessary to limit overvoltages or to supply internal circuits even in this case.

[0056] If, for example, pulses occur (e.g. a so-called ISO pulse in the range -100V / 2ms) or switching operations in the vehicle electrical system 13 that can generate negative voltage peaks, the limiter 51, such as the bidirectional TVS diode, protects the isolating means 44 or 44.1, 44.2, ... (diodes in the exemplary embodiment) from excessively high blocking voltage and thus from damage. Internal circuits for limiting the pulse height and thus protecting other internal components remain effective because the limiter 51 in the form of the bidirectional diode still permits a certain current flow towards the internal control unit ground 53 so that these internal circuits can continue to be supplied properly. In addition, the evaluation circuit 53 used, consisting of pull-up resistor 46 / pull-up voltage Up at connection 48, and the voltage measurement are protected from excessively high negative input voltages.

[0057] Protection against polarity reversal is also achieved. For example, some inputs or outputs of the control unit 18 require the activation of any switching units 15 in the event of polarity reversal protection to reduce power loss. Otherwise, in the event of polarity reversal, high reverse currents flowing through the connected loads 16 can damage the switching units 15 due to current flow via the body diode if the switching unit 15 is designed as a MOSFET. To control the switching units 15, a negative current flow via ground to the activation circuit is required (so-called reverse-on function). The provision of the limiter 51 in the form of a bidirectional diode allows this necessary negative current flow.

[0058] The limiter 51 should preferably be a Zener diode, which is particularly preferably designed as a bidirectional type, which also blocks when the forward voltage is applied (when using diodes as isolating means 44) via the diodes 44, 44.1, 44.2 and thus does not falsify the diagnostic result by a parasitic current.

[0059] The circuits can be used to particularly effectively compensate for undervoltage disconnection. As already described, the control unit 18 serves to protect, in particular, safety-relevant loads 16, such as the electric steering or brakes, from failure due to undervoltage. For this purpose, when a threshold value (the so-called undervoltage limit) is exceeded, less critical on-board power supply units or individual non-safety-relevant loads 17 are shut down to reduce the supply current and stabilize the on-board power supply 13.

[0060] If the ground cable 43 (as the primary ground line) fails, a voltage drop occurs between the internal control unit ground 52 and the vehicle ground 50 due to the forward voltage of the isolating means 44 designed as diodes. Since all functions in the control unit 18 reference the internal control unit ground 52, the amount of the forward voltage at the isolating means 44 or the diodes is missing for all internal supplies and voltage measurements.

[0061] However, since the resulting voltage loss is known from the voltage measurement of voltage U, the threshold value, in particular the undervoltage limit value, can be corrected or reduced by this amount. This ensures that the core function of undervoltage isolation of the safety-relevant loads 16 by the switch unit 15 remains unchanged, especially in the event of a fault.

[0062] The control unit 18, which is preferably designed as a power distributor, is arranged, for example, in a 12 V vehicle electrical system 13 in a motor vehicle directly at the interface between the non-safety-relevant sub-vehicle electrical system 10 and the safety-relevant sub-vehicle electrical system 11, in particular the ASI L-qualified sub-vehicle electrical system 11. However, its use is not limited to this.

Claims

Claims 1. Device for supplying energy to a control unit (18) of a motor vehicle, wherein a control unit (18) comprises at least two ground terminals (41, 42) for contacting a vehicle ground (50), wherein in the control unit (18) at least one isolating means (44) is provided between the two ground terminals (41, 42), wherein at least one of the ground terminals (41) is directly electrically connected to an internal control unit ground (52), while the further ground terminal (42) is connected via the isolating means (44) to the internal control unit ground (52), wherein the isolating means (44) is designed to prevent a compensating current between the two ground terminals (41, 42) within a specific range of a voltage drop (U_gnd) between the two ground terminals (41, 42), wherein at least one detection means (54, 56, 58) is provided for detecting a measure of a voltage drop (U) at the further ground terminal (42)and wherein at least one evaluation means (21) is provided which evaluates the detected degree of the voltage drop (II) at the further ground connection (42) in order to detect a fault in the ground connections (41, 42)., 2. Device according to claim 1, characterized in that the further ground connection (42) can be supplied with a voltage (Up), in particular an internal supply voltage (Up) of the control unit (18) for supplying components of the control unit (18), and / or with an impressed current (46, 48) for diagnosing a fault.

3. Device according to one of the preceding claims, characterized in that at least one limiting means (47) such as a Zener diode, particularly preferably a bidirectional Zener diode such as a bidirectional TVS diode, is connected in parallel to the isolating means (44).

4. Device according to one of the preceding claims, characterized in that the evaluation means (21) concludes that there is an error if the detected measure of the voltage drop (II) at the further ground connection (42) deviates from zero.

5. Device according to one of the preceding claims, characterized in that the evaluation means (21) concludes that there is a fault in the further ground connection (42) if the detected measure of the voltage drop (II) at the further ground connection (42) is in the range of the internal supply voltage (Up).

6. Device according to one of the preceding claims, characterized in that the evaluation means concludes that there is a fault in at least one of the ground connections (41), in particular a fault in the ground connection (41) directly connected to the control unit ground (52), if the detected measure of the voltage drop (U) at the further ground connection (42) is less than zero, in particular in the range of a forward voltage of a separating means (44) designed as a diode.

7. Device according to one of the preceding claims, characterized in that at least one threshold value is designed to be variable depending on the voltage drop (U) at the further ground connection (42) of the control device (18), wherein, depending on a comparison of a characteristic variable with the threshold value, an activation of at least one switch unit (15) for controlling at least one safety-relevant consumer (16) and / or at least one isolating switch (19) for connecting or disconnecting sub-vehicle networks (10, 11), in particular when the voltage drop (U) falls below the threshold value.

8. Device according to one of the preceding claims, characterized in that the control unit (18) comprises a plurality of switch units (15) for supplying in particular safety-relevant consumers (16) with electrical energy, wherein the switch units (15) can be controlled by a driver (31) which is connected to the control unit ground (52), and / or wherein the control unit (18) comprises at least two connections (KL30_0, KL30_1) via which a plurality of switch units (15) which are designed to be connectable to in particular safety-relevant consumers (16) can be supplied with energy, wherein at least one connected to the control unit evaluation means (21) connected to the device mass (52) is provided for controlling the switch units (15), in particular in the event of a faulty power supply.

9. Device according to one of the preceding claims, characterized in that the internal supply voltage (Up) can be connected to the potential of the further ground connection (42) via at least one switching means (49) and / or via at least one limiting means (47), in particular a Zener diode.

10. Device according to one of the preceding claims, characterized in that the ground connection (41) of the control unit (18) is electrically conductively connected both directly to the internal control unit ground (52) and to a connection of the isolating means (44), in particular an anode of at least one diode (44.1, 44.2) as a component of the isolating means (44), wherein the further ground connection (42) of the control unit (18) is electrically conductively connected both to a further connection of the isolating means (44), in particular a cathode of at least one diode (44.1, 44.2) as a component of the separating means (44), and also with a connection of a resistor (46), wherein a further connection of the resistor (46) can be connected to a supply voltage (48), in particular a control unit-internal supply voltage (48), wherein a potential of the further ground connection (42) relative to the internal control unit ground (52) is fed to an evaluation circuit (53) as a measure of the voltage drop (U) at the further ground connection (42).

11. Device according to one of the preceding claims, characterized in that the further ground connection (42) is connected, in particular via a resistor (54), to a voltage divider (56, 58) for detecting a measure of the voltage drop (U) at the further ground connection (42) and / or that the further ground connection (42) is connected to an analog-digital converter (62) for detecting and converting a measure of the voltage drop (U) at the further ground connection (42), in particular for feeding to the evaluation unit (21).

12. Device according to one of the preceding claims, characterized in that the isolating means (44) is configured such that, in error-free operation, in particular when the ground connections (41, 42) are properly connected to a vehicle ground (50), a current flows from the internal control unit ground (52) only via the directly connected ground connection (41) and / or that the isolating means (44) is configured such that, in faulty operation, in particular when at least one ground connection (41, 42) is not properly connected to a vehicle ground (50), a current flows from the internal control unit ground (52) via the further ground connection (41) and / or that the isolating means (44) is configured such that, in the event of a voltage drop (U_gnd) between the further ground connection (42) and the ground connection (41) to which the internal control unit ground (52) is directly connected,greater than zero, a compensating current between the further ground connection (42) and the ground connection (41) is prevented., 13. Device according to one of the preceding claims, characterized in that at least one diode is provided as the isolating means (44) and / or that the ground connection (41) is connected to an anode of a isolating means (44) designed as a diode and / or that the further ground connection (42) is connected to a cathode of a isolating means (44) designed as a diode and / or that several diodes connected in series are used as the isolating means (44).

14. Device according to one of the preceding claims, characterized in that the isolating means (44) is designed such that in the event of a voltage drop (U_gnd) between the further ground connection (42) and the ground connection (41) to which the internal control unit ground (52) is directly connected, which is less than zero and / or less than a limit value, a compensating current from the internal control unit ground (52) via the isolating means (44) to the further ground connection (42) is prevented.

15. Device according to one of the preceding claims, characterized in that at least the evaluation unit (21), in particular a microcontroller, and / or at least one gate driver (31) for controlling at least one switch unit (15) for a particularly safety-relevant Consumer (16) and / or an emergency operation logic (32) and / or a measuring device (33) and / or an infrastructure or supply (34) and / or at least one electronic component (35) is / are connected to the control unit ground (52).

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