Method for configuring an on-board electrical system

Abstract

The invention relates to a method for configuring an onboard electrical system (10) of a motor vehicle, wherein at least one load (30) is provided in the onboard electrical system, wherein within the scope of the configuration of the onboard electrical system (10), at least one of the at least one load (30) is assigned an electrical module, which is in turn selected from a module group, wherein a first load criterion related to the power supply requirement of the at least one load (30) and a second load criterion related to the degree of reaction of the at least one load (30) are taken into account when selecting the electrical module.

Description

Technical Field

[0001] The present invention relates to a method for configuring an onboard electrical system and to such an onboard electrical system. Background Art

[0002] In automotive usage, the term "onboard power supply" refers collectively to all electrical components in a vehicle. This includes not only electrical loads but also supply sources, such as batteries. A distinction is made between the energy onboard power supply and the communication onboard power supply. In this context, the energy onboard power supply, which supplies energy to the vehicle's components, will be considered first.

[0003] In modern motor vehicles, the energy flow within the onboard power system is often regulated by energy management concepts. To control the onboard power system, a microcontroller is usually provided which, in addition to control functions, also performs monitoring functions.

[0004] In motor vehicles, it is important that electrical energy is available so that the vehicle can be started at any time and that a sufficient current supply is available during operation. However, in the switched-off state, electrical loads can still be operated for a suitable period of time without adversely affecting the subsequent start.

[0005] Consumers provided in the onboard electrical system can be connected directly to the onboard electrical system or can be coupled to the onboard electrical system via components, also referred to below as electrical modules.

[0006] Nowadays, new components are used in vehicle power systems. These components require defined quality and availability, i.e., the integrity of the energy supply must meet ASIL targets (Automotive Safety Integrity Level). Quality must be guaranteed, and the supply voltage must be maintained within defined target ranges. Negative side effects caused by faults and malfunctions must be isolated.

[0007] With regard to availability, this has the consequence that safety-critical components may only be disconnected from the stable electrical energy supply with minimal probability. At the same time, it must be ensured that disturbances in the onboard power supply are avoided with high reliability or that the disturbance point is isolated in order to limit any negative effects on the power supply and thus on the safety-critical loads.

[0008] Individual solutions that address specific use cases and requirements are known. In particular, combining competing safety objectives with the goal of supplying loads to the onboard power supply system while simultaneously isolating the loads from interference with the onboard power supply system is currently not available on the market. Furthermore, complex solutions are known that, for example, use a DC converter.

[0009] In many cases, only fuses are used to protect wiring harnesses from overheating by disconnecting faulty current paths after their melting integral is exceeded. However, fuses can only be used to a very limited extent for use in highly available onboard electrical systems. On the one hand, sudden failures can occur, disrupting the energy supply to connected loads. On the other hand, fuses require a relatively high melting integral to disconnect, resulting in high short-circuit currents in the millisecond range. These high short-circuit currents can cause critical voltage fluctuations in the onboard electrical system, disrupting the power supply to other critical loads.

[0010] Furthermore, the tripping behavior of the fuse is not decisive especially for very large overloads. Conventional automobile fuses may trip, for example, after 90 seconds or after an hour at 1.5 times the rated current. Summary of the Invention

[0011] Against this background, a method having the features of claim 1 and an onboard electrical system according to claim 9 are described. Specific embodiments are derived from the dependent claims and from the description.

[0012] A method for configuring an onboard electrical system of a motor vehicle is described, wherein at least one load is provided in the onboard electrical system. Within the scope of configuring the onboard electrical system, an electrical module is assigned to at least one of the at least one load, the electrical module being selected from a module group, wherein a first load criterion related to the power supply requirement of the at least one load and a second load criterion related to the degree of reaction of the at least one load are taken into consideration when selecting the electrical module.

[0013] In one embodiment, suitable electrical or electronic modules are assigned to all loads to be provided in the onboard electrical system. However, it is also possible to assign suitable electrical modules only to selected loads. This assignment first dictates the selection of one or more suitable modules and then their consideration in the circuit design of the onboard electrical system.

[0014] The electrical modules in the module group are typically classified according to a first module criterion related to power supply safety and according to a second module criterion related to disconnectability. Then, when selecting an electrical module for at least one load, the first load criterion and the second load criterion are compared with the first module criterion and the second module criterion of the electrical modules in the module group. Thus, based on the first and second load criterion, the electrical modules are selected, whose two module criterion match the two load criterion. This means, for example, that loads with high power supply requirements and only a small degree of reaction are assigned the following electrical modules, which provide high power supply safety but only a small degree of disconnectability. In addition to the mentioned criteria, other criteria, such as cost and availability, can of course also be taken into account during the selection.

[0015] The method described thus provides for a configuration of an onboard electrical system or energy system, which can also be performed in an automated manner, within the scope of which at least one electrical or electronic module is selected from a module group, which is in turn assigned to a load. The selection takes into account the type of load, with criteria being used for this consideration. The load criteria for the power supply requirement are compared with the module criteria for the power supply safety, and the load criteria for the degree of reaction are compared with the module criteria for disconnectability.

[0016] In this context, "onboard electrical system configuration" refers to the selection of suitable electrical modules for connecting a load to or coupling it to the onboard electrical system. The load in question is then part of the onboard electrical system. For selection, a library of loads, referred to in this context as a module group, can be accessed. This module group contains possible electrical modules, which can be divided or categorized according to the criteria of power supply safety and disconnectability. This means that each electrical module in the module group is assigned a first characteristic variable or first value for power supply safety or a second characteristic variable or second value for disconnectability. These two characteristic variables or values, which only comprise a single numerical value in the design, provide information about the electrical module with respect to the two aforementioned criteria. This allows the quality of the electrical module with respect to power supply safety and disconnectability to be identified.

[0017] Accordingly, loads that are to be coupled to the onboard electrical system are classified. The load criterion for power supply requirements indicates how important the safe operation of these loads is to the vehicle or its driver. Therefore, safety-related loads, such as steering and brakes, often require a higher degree of power supply safety than non-safety-related loads, such as comfort loads, such as air conditioning systems. The load criterion for the degree of reaction indicates the potential impact of a defective load on the rest of the onboard electrical system. This defines, in particular, the time period within which a defective load can be disconnected from the rest of the onboard electrical system and its significance.

[0018] This provides a modular concept that can be used in a motor vehicle onboard energy system for distributing energy to loads. In this case, not only the requirement for the availability of the energy supply for the load paths is addressed, but also the requirement for the reliable disconnectability of the load paths is addressed if these load paths endanger the integrity of the input-side energy supply due to a short circuit.

[0019] The described onboard electrical system is provided for use in a motor vehicle having at least one consumer, wherein an electronic module selected according to the above-described method is assigned to at least one of the at least one consumer.

[0020] The electrical module can be selected from a module group comprising a first electrical module having a switch and a fuse connected in parallel to one another, a second electrical module having a fuse with a simple plausibility check function, a third electrical module having a fuse with a redundant current measurement function, and / or a fourth electrical module having two switches connected in parallel.

[0021] As a switch, for example, an electronic switch such as a transistor, in particular a field effect transistor such as a MOSFET can be used. As a fuse, a fuse or other suitable fuse can be used.

[0022] Further advantages and embodiments of the invention are apparent from the description and the drawings.

[0023] It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations or alone without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] It shows:

[0025] Figure 1A first embodiment of the described onboard electrical system is shown;

[0026] Figure 2 A second embodiment of the described onboard electrical system is shown;

[0027] Figure 3 A third embodiment of the described onboard electrical system is shown;

[0028] Figure 4 A fourth embodiment of the described onboard electrical system is shown;

[0029] Figure 5 A fifth specific embodiment of the presented onboard electrical system is shown. DETAILED DESCRIPTION

[0030] The invention is schematically illustrated in the drawings using exemplary embodiments and is described in more detail below with reference to the drawings.

[0031] Some possible implementations are described below. It should be noted that different implementation modules are derived for different requirement ranges, each of which is divided into requirements for the guaranteed ability to isolate load reactions, the degree of reaction or reaction freedom, and the guaranteed ability to provide an uninterrupted connection to the energy supply, namely, power supply security.

[0032] Figure 1 A first specific embodiment of the described onboard electrical system is shown, which is designated overall by reference numeral 10 . In this embodiment, disconnection is performed with ASIL C and power supply is performed with QM. The illustration shows a first onboard electrical system path 12 and a second onboard electrical system path 14 in onboard electrical system 10 , which are connected to each other via a firewall 16 .

[0033] A battery 20 for energy supply is arranged in the first onboard electrical system path 12. In addition, the internal resistance R of the battery 20 is drawn in the figure. i 22 and line 26 line resistance R cu 24. This onboard power supply line 12 connected to the terminal 30_1 28 is therefore used for energy supply, and the safe operation of this first onboard power supply line 12 is to be ensured.

[0034] Non-safety-related QM loads 30, i.e., comfort loads such as a ventilation system, are located in the second onboard power supply path 14. These loads therefore have low requirements regarding the power supply. However, in the event of a fault, these loads have a negative impact on the entire onboard power supply 10, meaning they have a low degree of freedom for reaction or a high degree of reaction. Therefore, it should be ensured that these loads can be reliably disconnected from the onboard power supply 10. The second onboard power supply path connected to terminal 30_032, or its loads, therefore, do not have high power supply requirements.

[0035] Firewall 16 includes a first switch 40, in this case a MOSFET, and a second switch 42, in this case a MOSFET. Furthermore, a monitoring unit 50 is provided, which provides current measurement, overcurrent protection, drivers for the MOSFETs, MOSFET diagnostics, and, if necessary, a computing unit and its power supply and monitoring. This monitoring unit can be a combination of discrete logic circuits and computing units and, if necessary, can also include one or more application-specific integrated circuits for convergence functions. Furthermore, a first sensor 60 for voltage measurement, a second sensor 62 for temperature measurement, a third sensor 64 for voltage measurement, and a fourth sensor 66 for current measurement are provided.

[0036] The illustrated embodiment clearly demonstrates that if two parallel current paths are used, each of these current paths can be controlled individually. During operation, the hardware protection threshold for each path or onboard power supply path is periodically lowered to trigger diagnostics. Once the hardware threshold is triggered at the correct level, the voltage drop across the entire current path changes due to the increased resistance of the entire switch. This approach tests the entire safety-related circuit, including the current measurement, comparator, shutdown logic, gate driver, and MOSFET path. The goal is to achieve ASIL compliance with high diagnostic coverage for the MOSFETs and the control / diagnostic circuitry or ASIC.

[0037] The above-described possibilities for disconnecting the two onboard power supply paths 12 , 14 can be considered in conjunction with the electrical modules explained below or individually, ie independently of the coupling of consumers to the electrical modules.

[0038] Figure 2 Another embodiment of the described onboard electrical system is shown, which is designated overall by reference numeral 100. In this embodiment, the disconnection is carried out with QM and the power supply is carried out with ASIL C. The illustration shows a battery 102 as an energy supply, an internal resistance Ri 104 and line 108 line resistance R cu 106. This power supply branch is connected to terminal 30_1 110.

[0039] Connected to terminal 30_1 110 is a first electrical module 120 in which a switch 122, in this case a MOSFET, and a fuse 124, in particular a fuse, are connected in parallel. Furthermore, a unit 130 is provided, including a first sensor 132 for temperature measurement, a second sensor 134 for current measurement, a third sensor 136 for temperature measurement, and a fourth sensor 138 for voltage measurement. In an additional embodiment, current sensor 134 can also be implemented in duplicate for redundancy reasons, for example, by first measuring the voltage drop across the parallel circuit formed by the fuse and the MOSFET, and secondly by an additional independent measurement method, such as a series-connected shunt resistor or Hall element.

[0040] By measuring the output voltage, fault causes such as defective disconnection or drift of fuses and MOSFETs can be identified. The combination of a temperature sensor and a current sensor allows, on the one hand, the temperature history of the fuse / MOSFET to be calculated for the current measurement. On the other hand, the combination of an elevated temperature sensor value and implausible measured values ​​from one or more current sensors can be used to infer drift in the resistance of the MOSFET or fuse.

[0041] Furthermore, the already described brief disconnection of the semiconductor switch can intentionally cause a change in the resistance value of the parallel circuit of the fuse and the MOSFET. As a diagnostic measure, it can be checked whether this change is manifested in a change in one or more sensor values, in particular in a change in the voltage drop across the parallel circuit of the MOSFET and the fuse.

[0042] A load can be connected to the connection 140 , which load is assigned to the first electronic module 120 .

[0043] The embodiment shown thus provides a method for safely supplying high currents to a load, while simultaneously preventing negative reactions to the onboard electrical system, thereby enabling the use of a fuse.

[0044] In this embodiment, the MOSFET and the fuse are arranged in parallel. During normal operation, the MOSFET is usually in a conducting state, and the two parallel or redundant paths carry the current load together. By briefly disconnecting the MOSFET for diagnostic purposes, that is, for a shorter time than the tolerance time, the fuse resistance can be monitored. This is done to detect potential faults in the fuse, such as disconnection or drift, as well as potential faults in the MOSFET, such as its inability to disconnect.

[0045] If the fuse 124 exhibits an incorrectly increased resistance, the MOSFET path is designed to carry the full current.

[0046] In the event of a MOSFET or ASIC failure, fuse 124 is designed to conduct the entire current for supplying the load or consumers. The risk of systemic failures within the MOSFET or its driver for maintaining the MOSFET in a conductive state can be prevented by connecting fuse 124 in parallel, wherein systemic failures in the parallel fuse path can be eliminated by suitable design.

[0047] Due to the current sharing between the MOSFET and the fuse 124, the fuse and the MOSFET can be kept away from aging-related currents. Thus, both the MOSFET and the fuse can be shielded from aging-related faults.

[0048] If this path is used for higher currents, fuse 124 cannot ensure rapid disconnection from the load, and the load must therefore be protected from negative influences, ie, it must have a high degree of freedom from reaction.

[0049] Due to the reduced aging of the fuse and the MOSFET, it is possible to use a fuse with a diffusion-free region having small tolerances, which is usually used to increase the melting integral I 2 The design of the diffusion-free zone makes the triggering characteristics of the safety device predictable. In addition, the safety device becomes insensitive to thermal stress.

[0050] In the event of a short circuit at the output of the circuit, the parallel MOSFET circuit can be kept closed for a delay time controlled by the microcontroller. This then produces the same behavior as a passive fuse, but without the disadvantage of significantly increased tolerances.

[0051] Figure 3A third specific embodiment of the onboard electrical system is shown, which is designated overall by reference numeral 200. In this embodiment, the disconnection is performed with QM and the power supply is performed with ASIL A. The illustration shows a battery 202 as an energy supply in onboard electrical system 200, an internal resistance R of battery 202, and a i 204 and the line resistance R of line 208 cu 206. This power supply branch is connected to terminal 30_1 210.

[0052] Connected to terminal 30_1 210 is a second electrical module 220 having a differential amplifier 222, a fuse 224, and a microcontroller 226. Furthermore, a first sensor 230 for temperature measurement, a second sensor 232 for current measurement, and a third sensor 234 for voltage measurement are provided.

[0053] Temperature sensor 230 can be used to measure the temperature increase across fuse 224 in order to calculate the temperature compensation of the fuse resistance. Furthermore, excessive temperature increases due to malfunctions (drift) of fuse 224 can be detected. Knowledge of the temperature-compensated internal resistance of the fuse and the voltage drop across fuse 224 via differential amplifier 222 allows, on the one hand, the current flowing through fuse 224 to be calculated, and, on the other hand, aging-related stresses on fuse 224 to be detected and, if necessary, incorporated into an aging model.

[0054] A load can be connected to terminal 240, which is then connected to vehicle electrical system 200 via second electrical module 220. The embodiment shown provides for a safe power supply via fuse 224. This configuration prevents negative feedback from the load and includes a fuse with a simple plausibility check function.

[0055] By means of a diagnosed fuse 224, for example, a power supply safety according to ASIL A can be achieved. If this is sufficient, this can be performed by counting the current pulses and by providing a stress analysis and aging prediction. The onboard power supply path and the wiring to the loads form a voltage divider between the power source and the short-circuit switching circuit.

[0056] The onboard energy system configuration must ensure that a short circuit in a load does not adversely affect the safe power supply of other loads.

[0057] Figure 4A fourth specific embodiment of the onboard electrical system is shown, which is generally designated by reference numeral 300. In this embodiment, the disconnection is performed with QM and the power supply is performed with ASIL A (C) or B (D). The illustration shows a battery 302 as an energy supply in onboard electrical system 200, an internal resistance R of battery 302, and a resistance of battery 302. i 304 and the line resistance R of line 308 cu 306. This power supply branch is connected to terminal 30_1 310.

[0058] Connected to terminal 30_1 310 is a third electrical module 320 comprising a first differential amplifier 322, a fuse 324, a second differential amplifier 326 with an associated measuring resistor 328, and a microcontroller 330. Furthermore, a first sensor 332 for temperature measurement, a second sensor 334 for current measurement, a third sensor 336 for voltage measurement, and a fourth sensor 338 for temperature measurement are provided.

[0059] In this embodiment, serious faults can also be detected by measuring the output voltage with third sensor 336 . For a detailed evaluation of the functional state of fuse 324 , the expected internal resistance of fuse 324 can be determined from the temperature measured with fourth sensor 338 .

[0060] Current information can be obtained by knowing the voltage drop across fuse 324 via differential amplifier 322 and the temperature-compensated resistance. This current information can be compared with the current information from second differential amplifier 326 via measuring resistor 328 in order to mutually plausibly check the two current information and to detect critical resistance drifts of fuse 324.

[0061] A load can be connected to terminal 340 , which load is then connected to vehicle electrical system 300 via second electrical module 320 .

[0062] This embodiment provides for a safe power supply via the fuse 324. The onboard energy system configuration prevents negative feedback of the load.

[0063] Fuse 324 must ensure availability in order to ensure ASIL A (C) for manual driving operation or, for example, ASIL B (D) in automated driving operation by means of improved diagnostics. Therefore, it is advantageous to monitor the fuse resistance and its characteristics by additionally measuring the current through a measuring resistor.

[0064] The onboard energy supply path and the wiring to the loads create a voltage divider between the power source and the short-circuit switching circuit.

[0065] The energy onboard power grid configuration must ensure that a short circuit on a load does not adversely affect the safe power supply of other loads.

[0066] Figure 5 The fifth embodiment of the described onboard electrical system is shown, which is generally designated by reference numeral 400. In this embodiment, the disconnection is performed with ASIL B(D) and the power supply is performed with ASIL B(D). The illustration shows a battery 402 as an energy supply in onboard electrical system 400, an internal resistance R of battery 402, and a resistance of 0. i 404 and the line resistance R of line 408 cu 406. This power supply branch is connected to terminal 30_1 410.

[0067] A fourth electrical module 420 is connected to terminal 30_1 410. A first switch 422, in this case a MOSFET, a second switch 424, in this case a MOSFET, a first control and diagnostic device 426, and a second control and diagnostic device 428 are provided in this fourth electrical module 420. Furthermore, a first sensor 430 for temperature measurement, a second sensor 432 for current measurement, a third sensor 434 for voltage measurement, and a fourth sensor 436 for temperature measurement are provided.

[0068] Similar to the previous embodiment, voltage measurement can be used to detect serious faults. Since output 440 can be disconnected entirely via semiconductors in this embodiment, the disconnection capability of both switches 422 and 424 is checked by opening them while the vehicle is in a safe state. In this embodiment, current measurement is performed using a second sensor 432 by determining the voltage drop across the two switches 422 and 424. The quality of the measurement can be further improved by installing an additional resistor-based current measurement in series. Each switch 422, 424 is assigned a temperature sensor, which allows the temperature compensation of the switch resistance to be calculated and, on the other hand, allows the inference of a fault in the thermal connection of the MOSFET to be drawn from the temperature increase relative to the ambient temperature.

[0069] To prevent semiconductor damage in the event of a short circuit, an autonomous, fast-acting overload circuit is integrated into modules 426 and 428. This overload circuit compares the current flowing from sensor system 432 installed in the module with a variable limit value. By fine-tuning the cutoff limit to a value below the current applied, the protective device can be diagnosed before a potential fault occurs. The autonomous overload circuit should detect the overload and, in response, disconnect the corresponding switch 422 or 424. This can be verified by reversely measuring the voltage drop across switch 422 or 424. This diagnosis can be performed during coasting operation or even during continuous operation, provided that one of the two independent current paths remains closed at all times.

[0070] A load 440 can be connected to output 440 , which is then connected to vehicle electrical system 400 via second electrical module 420 .

[0071] This embodiment thus illustrates a scenario where the power supply is safe solely via MOSFETs. Here, two parallel MOSFET paths ensure the availability of a voltage supply that meets ASIL B (D), which can be distributed to two A (D) for each path. Furthermore, rapid disconnection is possible.

Claims

1. A method for configuring an onboard power supply system (10, 100, 200, 300, 400) of a motor vehicle, wherein at least one load (30) is provided in the onboard power supply system (10, 100, 200, 300, 400), wherein within the scope of the configuration of the onboard power supply system (10, 100, 200, 300, 400), at least one of the at least one load (30) is assigned an electrical module (120, 220, 320, 420), which is in turn selected from a module group, wherein a first load criterion related to the power supply requirement of the at least one load (30) and a second load criterion related to the degree of reaction of the at least one load (30) are taken into account when selecting the electrical module (120, 220, 320, 420), in, The first load criterion, which is related to the power supply requirement of the at least one load (30), indicates how safe operation of the load is important for the vehicle or the driver of the vehicle, and the second load criterion, which is related to the degree of reaction of the at least one load (30), indicates the possible influence of a defective load on the rest of the vehicle electrical system.

2. The method according to claim 1 , wherein the electrical modules (120, 220, 320, 420) in the module group are sorted according to a first module criterion related to power supply safety and according to a second module criterion related to disconnectability, wherein when selecting the electrical module (120, 220, 320, 420) for at least one load (30), the first load criterion and the second load criterion are compared with the first module criterion and the second module criterion of the electrical modules (120, 220, 320, 420) in the module group.

3. The method according to claim 1 or 2, wherein the module group comprises a first electrical module (120) having switches (40, 42, 122, 422, 424) and fuses (124, 224, 324) connected in parallel with one another.

4. The method according to claim 1 or 2, wherein the module group comprises a second electrical module (220) having a fuse (124, 224, 324) with a simple plausibility check function.

5. The method according to claim 1 or 2, wherein the module group comprises a third electrical module (320) having a fuse (124, 224, 324) with a redundant current measurement function.

6. The method according to claim 3, wherein the fuse (124, 224, 324) is a fuse selected from the group consisting of a fusible fuse, a conductor track fuse, and a narrowed conductor track.

7. The method according to claim 1 or 2, wherein the module group comprises a fourth electrical module (420) having two switches (40, 42, 122, 422, 424) connected in parallel.

8. The method according to claim 1 or 2, wherein a fire barrier (16) is additionally provided for connecting the onboard power supply lines (12, 14) to one another.

9. An onboard power system for a motor vehicle, comprising at least one load (30), which is connected to the onboard power system (10, 100, 200, 300, 400) via an electrical module (120, 220, 320, 420), wherein the electrical module is used to implement the method according to any one of claims 1 to 8.

10. The onboard electrical system according to claim 9, wherein the electrical module (120, 220, 320, 420) is selected from a module group, the module group comprising a first electrical module (120) having a switch (40, 42, 122, 422, 424) and a fuse (124, 224, 324) connected in parallel with one another, a second electrical module (220) having a fuse (124, 224, 324) with a simple plausibility check function, a third electrical module (320) having a fuse (124, 224, 324) with a redundant current measurement function, and / or a fourth electrical module (420) having two switches (40, 42, 122, 422, 424) connected in parallel.

11. The onboard power supply system according to claim 9 or 10, wherein the onboard power supply system (10, 100, 200, 300, 400) has at least two onboard power supply paths (12, 14) connected to one another via a fire wall (16).

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