Safety circuit for a vehicle electrical system and vehicle electrical system

Abstract

The safety circuit (SI) has one or more diode half-bridge circuits, each having a first diode (D11,..., D14) and a second diode (D21,..., D24), which are connected in series. The respective diode half-bridge circuit has a central connection (M1,..., M4), a first connection which is connected to the cathode of the first diode (D11,..., D14) and a second connection which is connected to the anode of the second diode (D21,..., D24). The respective diode half-bridge circuits can be connected via their central connections (M1,..., M4) in each case to a low-voltage conductor which conducts out of a high-voltage region of the vehicle electrical system. The safety circuit (SI) comprises a current-limiting circuit (CL), and the first connections and the second connections of the diode half-bridge circuits are connected to a reference potential connection via the current-limiting circuit (CL), which has a current-limiting element (R) and a plurality of electrical one-way elements (DCL1, DCL2), such that, in the event of a fault in which at least one of the low-voltage conductors (L1,..., L4) conducts a positive high-voltage potential (HV+) or a negative high-voltage potential (HV-) out of the high-voltage region (HVB), a fault current which flows over the low-voltage conductor (L1, …, L4) is conducted away to the reference potential connection.

Description

[0001] Description

[0002] Fuse circuit for a vehicle electrical system and vehicle electrical system

[0003] The invention relates to a safety circuit for a vehicle electrical system and a vehicle electrical system having the safety circuit.

[0004] It is common practice to equip vehicles with electric drives or other electrical components. To achieve high performance, especially for traction, high voltages are used, for example, 400 volts or more, which, unlike the otherwise common 12-volt electrical systems, can pose a danger to humans.

[0005] For this reason, vehicles that have a high-voltage electrical system (i.e. a high-voltage electrical system - HV electrical system) are provided with insulation that electrically separates the HV electrical system from the rest of the electrical system and the ground potential, in particular from the chassis of the vehicle.

[0006] In addition, the vehicles include control or sensor signals or low-voltage supply signals, which, in contrast to the high-voltage potentials, are not particularly protected against contact.

[0007] Since a fault in the insulation can lead to a touch voltage that is harmful, if not fatal, to humans, additional protective measures are necessary.

[0008] It is an object of the invention to provide a safety circuit which enables improved protection against dangerous touch voltages with a small space requirement and low cost.

[0009] The problem is solved by the features of the independent patent claims. Advantageous embodiments are characterized in the subclaims.

[0010] According to a first aspect, the problem is solved by a fuse circuit for a vehicle electrical system. The vehicle electrical system has a high-voltage electrical system (HV electrical system) and a low-voltage electrical system (LV electrical system). At least part of the high-voltage electrical system is arranged in a predetermined high-voltage area. One or more low-voltage conductors lead out of the high-voltage area. The low-voltage conductors connect, in particular, low-voltage components arranged in the high-voltage area with further low-voltage components arranged outside the high-voltage area.

[0011] The low-voltage conductors are designed to conduct a low-voltage signal potential and / or a low-voltage supply potential (e.g., 12 V or +5 V and ground) from the high-voltage area, at least during fault-free operation. The low-voltage signal potentials are used to transmit information, in particular control signals, monitoring signals, sensor signals, and the like.

[0012] The high-voltage area is, in particular, a closed or enclosed high-voltage area or a closed space. The high-voltage area is enclosed, for example, by a housing.

[0013] The fuse circuit has a reference potential terminal for connecting to a protective conductor potential of the vehicle. The protective conductor potential can, in particular, correspond to a vehicle ground or chassis potential.

[0014] The fuse circuit comprises one or more diode half-bridge circuits, each comprising a first diode and a second diode connected in series. Each diode half-bridge circuit has a center terminal, a first terminal connected to the cathode of the first diode, and a second terminal connected to the anode of the second diode. Furthermore, the fuse circuit comprises one or more low-voltage potential terminals for connecting the respective center terminals to one of the low-voltage conductors leading out of the high-voltage region. The fuse circuit comprises a current-limiting circuit.The first and second terminals of the diode half-bridge circuits are connected to the reference potential terminal via the current-limiting circuit, which has a current-limiting element and several electrical one-way elements. If a fault occurs in which at least one of the low-voltage conductors conducts a positive high-voltage potential or a negative high-voltage potential out of the high-voltage range, a fault current flowing through the low-voltage conductor is diverted via the reference potential terminal. The fault current is triggered by the fault, in particular an insulation fault.

[0015] In multiple diode half-bridge circuits, these are connected in parallel. The cathodes of the first diodes are connected, and the anodes of the second diodes are connected. The diodes of the respective diode half-bridge circuits are connected in the same forward direction.

[0016] The number of diode half-bridge circuits corresponds in particular to the number of low-voltage conductors leading out of the high-voltage area, so that each diode half-bridge circuit is individually connected to one of the low-voltage conductors.

[0017] The current-limiting circuit has a first terminal and a second terminal. The cathodes of the first diodes are connected to the first terminal of the current-limiting circuit, and the anodes of the second diodes are connected to the second terminal of the current-limiting circuit. The current-limiting element is preferably designed for high current pulses, since very high voltage peaks can be present at the current-limiting element.

[0018] The fuse circuit has a first voltage limiting element and a second voltage limiting element. The first terminals of the diode half-bridge circuits are connected to the first terminal of the current limiting circuit via the first voltage limiting element, and / or the second terminals of the diode half-bridge circuits are connected to the second terminal of the current limiting circuit via the second voltage limiting element.

[0019] In particular, the safety circuit enables the contact voltage to be limited to less than 60 V DC at accessible terminals of voltage class A as a precautionary measure for fault protection.

[0020] The invention is based on the finding that the low-voltage signal conductors and / or low-voltage potential conductors present in a high-voltage area with high potentials and extending from a high-voltage area are not specially protected and therefore pose a significant hazard in the event of a fault, particularly in the event of an insulation fault. The fuse circuit enables the low-voltage conductors extending from the high-voltage area to be specially protected.

[0021] The special design of the current-limiting circuit with its one-way electrical elements means that only one current-limiting element is required to divert the fault current via the reference potential connection. This means that the fault current is diverted via the single current-limiting element regardless of the polarity of the high-voltage potential present on the respective low-voltage conductor.

[0022] In this way, the safety circuit is designed to divert the current to the protective conductor potential via the current limiting circuit when each of the two high-voltage potentials is introduced into at least one of the low-voltage conductors.

[0023] The fault current, which flows in the affected low-voltage conductor, particularly in the event of a fault, due to a discharge of existing capacitances arranged between the positive HV potential and the protective conductor potential and between the negative HV potential and the protective conductor potential in the high-voltage area, can be diverted to the protective conductor connection or to the protective conductor potential via the fuse circuit.

[0024] In at least one advantageous embodiment according to the first aspect, the current-limiting element comprises a resistor or is formed by a resistor. The resistor is preferably an ohmic resistor. The current-limiting element can be formed by one or more resistive components. The resistive components can be connected in series. In particular, multiple resistive components can be used to absorb / dissipate more potentially dangerous energy and / or to increase resistance to voltage surges with a higher amplitude / peak value, such as 1,000 Vpeak instead of just 500 Vpeak.

[0025] In at least one embodiment according to the first aspect, the plurality of one-way electrical elements comprise a first one-way electrical element and a second one-way electrical element. The first one-way electrical element is arranged in a first branch, and the second one-way electrical element is arranged in series with the current-limiting element in a second branch. The second branch is arranged parallel to the first branch.

[0026] In at least one embodiment according to the first aspect, the plurality of electrical one-way elements each comprise at least one diode or are each formed by at least one diode. In particular, the first electrical one-way element comprises at least one first diode and / or the second electrical one-way element comprises at least one second diode. The at least one first diode and the at least one second diode can be identical or different. The anode of the at least one first diode is connected to the reference potential terminal. The cathode of the at least one second diode is likewise connected to the reference potential terminal.

[0027] In at least one embodiment according to the first aspect, the fuse circuit has a first voltage limiting element and a second voltage limiting element, and the first terminals of the diode half-bridge circuits are connected to a first terminal of the current limiting circuit via the first voltage limiting element, and / or the second terminals of the diode half-bridge circuits are connected to a second terminal of the current limiting circuit via the second voltage limiting element. The first and second voltage limiting elements are each configured to conduct when a threshold voltage or a breakdown voltage is exceeded, and not to conduct or virtually not to conduct when the threshold voltage or the breakdown voltage is undershot.

[0028] The diode half-bridge circuits form a network that allows multiple low-voltage conductors to be protected to be connected to the first voltage-limiting element and the second voltage-limiting element, respectively. Multiple low-voltage conductors can thus be protected with the first and second voltage-limiting elements. This results in cost and space advantages, as diodes are cheaper and smaller than voltage-limiting elements, especially when designed for multiple amperes or several hundred amperes of peak load.

[0029] In at least one embodiment according to the first aspect, the first voltage limiting element and / or the second voltage limiting element each comprises a suppressor diode and / or a varistor and / or a protective diode and / or a Zener diode and / or a thyristor circuit and / or a gas discharge tube and / or a spark gap and / or a DIAC, or is formed by one or more such components. The aforementioned components can also form the voltage limiting element in any desired combination. The suppressor diode can also be referred to as a transient voltage suppressor (TVS). According to a second aspect, the invention is characterized by a vehicle electrical system.The vehicle electrical system comprises a vehicle electrical system with a high-voltage electrical system, which is arranged at least partially in a predetermined high-voltage range, and a low-voltage electrical system, wherein one or more low-voltage conductors lead out of the high-voltage range, and the low-voltage conductors are designed to lead out a low-voltage signal potential and / or a low-voltage supply potential from the high-voltage range, at least during fault-free operation. Furthermore, the vehicle electrical system has a fuse circuit according to the first aspect, wherein at least some of the low-voltage conductors are each connected to one of the LV potential terminals, and the reference potential terminal is connected to the protective conductor potential (GND) of the vehicle.

[0030] Advantageous embodiments of the safety circuit according to the first aspect also apply to the second aspect.

[0031] In at least one advantageous embodiment according to the second aspect, the high-voltage vehicle electrical system comprises a positive high-voltage potential and a negative high-voltage potential, and the positive high-voltage potential is connected to the protective conductor potential of the vehicle via a first capacitance and the negative high-voltage potential is connected to the protective conductor potential of the vehicle via a second capacitance.

[0032] Embodiments of the invention are explained in more detail below with reference to the schematic drawings.

[0033] They show:

[0034] Figure 1 A vehicle electrical system with an exemplary design of a safety circuit for a vehicle electrical system,

[0035] Figure 2 shows a current flow in the vehicle electrical system in the event of a faulty introduction of a positive high-voltage potential into a low-voltage conductor which extends from a high-voltage area of ​​the vehicle electrical system and

[0036] Figure 3 illustrates the respective current flow in the vehicle electrical system when a negative high-voltage potential is incorrectly introduced into a low-voltage conductor extending from the high-voltage area of ​​the vehicle electrical system. In the figures, the same reference numerals are used for elements with essentially the same function; however, these elements do not necessarily have to be identical in every detail.

[0037] In embodiments described herein or shown in the drawings, any direct electrical connection or coupling, i.e., any connection or coupling without additional intervening elements, may also be implemented by an indirect connection or coupling, i.e., a connection or coupling with one or more intervening elements, or vice versa, as long as the general purpose of the connection or coupling, for example, transmitting a certain type of signal or transmitting a certain type of information, is substantially maintained.

[0038] Figure 1 shows a vehicle electrical system FBS with an exemplary embodiment of a fuse circuit S1 for a vehicle electrical system FB. The vehicle electrical system FB has a high-voltage electrical system (HV electrical system) HV and a low-voltage electrical system (LV electrical system) LV. The LV electrical system is coupled to the HV electrical system HV, for example, via a galvanically isolated voltage converter (not shown in the figures).

[0039] The LV electrical system can comprise a 12 V, 13 V, 14 V, 24 V, 42 V, or 48 V network. The high-voltage range (HVB) includes at least one circuit with a nominal voltage of more than 60 V, or at least 200 V, or at least 400 V, or at least 800 V.

[0040] The high-voltage electrical system (HV) is arranged at least partially within a predefined high-voltage area (HVB). ​​The high-voltage area (HVB) is enclosed, for example, by a housing (G). In particular, the housing (G) can completely enclose the high-voltage area (HVB) (if necessary, with a closable opening for maintenance in the high-voltage area (HVB).

[0041] The HV on-board electrical system HV has a positive high-voltage potential HV'+ and a negative high-voltage potential HV'-. Between the positive high-voltage potential HV'+ and the negative high-voltage potential HV'+, for example, at least one first capacitance Cy+ and at least one second capacitance Cy- are arranged. The at least one first capacitance Cy+ and the at least one second capacitance Cy- are each connected to one another via a connection point VP, which in turn is connected to a protective conductor potential GND. The protective conductor potential GND can correspond to a vehicle ground or a chassis potential. The at least one first capacitance Cy+ and the at least one second capacitance Cy- serve in particular to suppress common-mode interference and preferably each have Y capacitors.

[0042] In the high-voltage area HVB, one or more low-voltage components NV are arranged, for example a control, monitoring and / or sensor component.

[0043] From this or the low-voltage components NV, one or more low-voltage conductors L1, ..., L4 lead out of the high-voltage area HVB, in particular from the housing G. Four low-voltage conductors L1, ..., L4 are shown as examples in Figure 1. The low-voltage conductors L3, L4 are used, for example, as communication signal conductors, e.g. for a two-wire data transmission connection with symmetrical or asymmetrical signal routing for communication between the one or more low-voltage components NV arranged in the high-voltage area HVB and further low-voltage components arranged outside the high-voltage area. For example, one of the low-voltage components NV comprises a transmission component designed to transmit data according to a CAN communication protocol.One or more of the low-voltage conductors L1, L2 are used, for example, as low-voltage potential conductors, for example as terminal 30, or as safety signal conductors, for example as interlock signal conductors.

[0044] The low-voltage conductors L1, ..., L4 thus carry low-voltage signal potentials and / or low-voltage supply potentials, for example +12 V or +5 V and ground, at least in fault-free operation, and conduct these out of the high-voltage area HVB.

[0045] In the event of a fault, in particular when an insulation fault occurs, symbolized by the resistances RF, RF', one of the low-voltage conductors L1, ..., L4 is connected to one of the HV potentials HV-, HV+. As a result, this low-voltage conductor L1, ..., L4 carries an HV potential HV-, HV+. Depending on the insulation fault (high-resistance or low-resistance), the HV potentials HV+, HV- can be equal to or at least approximately equal to the high-voltage potentials HV'+, HV'- of the high-voltage vehicle electrical system or at least have a potential whose voltage compared to the protective conductor potential GND is greater than a specified limit voltage for normal operation of the low-voltage conductors L1, ..., L4 (for example > 60 V DC).

[0046] A large amount of energy can be stored in the at least one first capacitor Cy+ and the at least one second capacitor Cy-, or in the Y-suppression capacitors. This energy can penetrate the low-voltage electrical system LV due to an insulation fault between one of the high-voltage potentials HV'+, HV'- of the high-voltage electrical system and one of the low-voltage conductors L1, ..., L4. This amount of energy, if "absorbed" by a person, can be at least dangerous, if not fatal.

[0047] The energy can be dissipated using the safety circuit Sl.

[0048] For this purpose, the fuse circuit S1 comprises one or more diode half-bridge circuits, each comprising a first diode D11, ..., D14 and a second diode D21, ..., D24, which are connected in series. Each diode half-bridge circuit has a center terminal M1, ..., M4, a first terminal connected to the cathode of the first diode D11, ..., D14, and a second terminal connected to the anode of the second diode D21, ..., D24.

[0049] The center terminals M1, ..., M4 are each connected to one of the low-voltage conductors L1, ..., L4, which lead out of the high-voltage range (HV), via LV potential terminals. The first and second terminals of the diode half-bridge circuits are connected to a reference potential terminal via a current-limiting circuit CL, which has a current-limiting element R and several electrical one-way elements DCL1, DCL2. This reference potential terminal, in turn, is connected to the vehicle's protective conductor potential GND.

[0050] The current limiting circuit CL preferably has a first electrical one-way element DCL1 and a second electrical one-way element DCL2. The first electrical one-way element DCL1 is arranged in a first branch and the second electrical one-way element DCL2 is arranged in series with the current limiting element R in a second branch, and the second branch is arranged in parallel with the first branch. The current limiting element R preferably comprises a resistor, in particular an ohmic resistor. The current limiting element R is formed, for example, by one or more resistance components. The parallel connection of the two branches is arranged between a first terminal of the current limiting circuit CL and the reference potential terminal. A second terminal of the current limiting circuit CL is arranged in the second branch between the current limiting element R and the second electrical one-way element DCL2.

[0051] The electrical one-way elements DCL1, DCL2 are designed to allow current to pass in one direction and block current in the other direction. For example, each electrical one-way element DCL1, DCL2 has at least one diode or is formed by at least one diode.

[0052] Via the current-limiting element R of the current-limiting circuit CL, both the positive HV potential HV+, which is incorrectly introduced into the low-voltage conductors L1, ..., L4, or the low-voltage potential connections, and the negative HV potential HV-, which is incorrectly introduced into the low-voltage conductors L1, ..., L4, or the low-voltage potential connections, are diverted to the protective conductor potential GND. Therefore, only one current-limiting element R, specifically only one resistor, is required.

[0053] In an optional embodiment, the first terminals of the diode half-bridge circuits are connected to the first terminal of the current limiting circuit CL via a first voltage limiting element TVS1 and / or the second terminals of the diode half-bridge circuits are connected to the second terminal of the current limiting circuit CL via a second voltage limiting element TVS2.

[0054] The voltage limiting elements can also be referred to as overvoltage elements. The respective voltage limiting element is designed to conduct when a threshold voltage or breakdown voltage is exceeded, and to not conduct or to conduct almost entirely when the threshold voltage or breakdown voltage is undershot.

[0055] The limit voltage of the first and second voltage limiting elements TVS1, TVS2 is in particular below the nominal voltage between the positive high-voltage potential HV'+ and the negative high-voltage potential HV'- of the high-voltage vehicle electrical system and preferably below a danger threshold, in particular 60 V. The limit voltage of the voltage limiting elements can be between 10 V and 50 V, in particular between 35 V and 45 V.

[0056] For example, the two voltage limiting elements TVS1, TVS2 each have a suppressor diode.

[0057] The first electrical one-way element DCL1 and the second electrical one-way element DCL2 are preferably directly connected to the current-limiting element R. They force the fault current triggered by the fault, in particular by the insulation fault, to flow through the voltage-limiting elements TVS1, TVS2. They thus prevent the fault current from (partially) bypassing the current-limiting element R, which would cause high peak currents that would be critical / damaging to the components of the fuse circuit S1.

[0058] In an optional embodiment, a first device and / or second device is provided, which is designed to detect a current flow through the first voltage limiting element TVS1 or the second voltage limiting element TVS2, respectively. For example, an evaluation device is provided which compares the current flow with a limit value (approximately 1 mA or 10 pA) and, if the limit value is exceeded, emits an error signal and / or causes the high-voltage vehicle electrical system HV to be disconnected, for example by controlling a disconnector in the high-voltage vehicle electrical system HV or in a line that carries at least one of the high-voltage potentials HV'+, HV'- of the high-voltage vehicle electrical system HV and, if necessary, disconnects the high-voltage area HVB with other components or connections of the vehicle electrical system shown when controlled (preferably across all poles).

[0059] Figure 2 shows a current flow in the vehicle electrical system FB when a positive high-voltage potential HV+ is incorrectly introduced into a first low-voltage conductor L1, which extends from the high-voltage area HVB of the vehicle electrical system FB. The current flows from the first capacitance Cy+ from the high-voltage area HVB through the first diode D11 of the diode half-bridge circuit, whose center connection M1 is connected to the first low-voltage conductor L1 via the associated LV potential connection, via the first voltage limiting element TVS1 into the current limiting element R and the second electrical one-way element DCL2 in the direction of the reference potential. Figure 3 shows a current flow in the vehicle electrical system FB when a negative high-voltage potential HV- is incorrectly introduced into the first low-voltage conductor L1, which extends from a high-voltage area HVB of the vehicle electrical system.The fault current flows from the safety conductor potential GND through the first electrical one-way element DCL1 via the current limiting element R and the second voltage limiting element TVS through the second diode D21 of the diode half-bridge circuit, whose center terminal M1 is connected to the low-voltage conductor L1 via the associated LV potential terminal, into the second capacitance Cy- in the high-voltage range HVB.

[0060] The special design of the current limiting circuit CL enables the current limitation for the diodes D11, ..., D14, D21, ..., D24 of the diode half-bridge circuits and for the voltage limiting elements TVS1, TVS2 to be achieved with just one current limiting element R, in particular just with a single resistor formed by one or more resistive components. Advantageously, this allows for space and cost savings compared to solutions that use a current limiting element R for each voltage limiting element TVS1, TVS2. The savings are considerable, since the resistor(s) must be designed for large pulse currents in order to meet the required safety requirements.

[0061] The description of the subject matter presented here is not limited to the individual specific embodiments. Features of different embodiments may be combined with one another—where technically feasible—to form further embodiments. For example, variations or modifications described with respect to one of the embodiments may also be applicable to other embodiments, unless otherwise stated.

[0062] D11 , D14 first diodes of the diode half-bridge circuit

[0063] D21 , D24 second diodes of the diode half-bridge circuit

[0064] M1, M4 center connection

[0065] NV low-voltage component

[0066] LV low-voltage electrical system

[0067] HV high-voltage electrical system

[0068] HVB high-voltage range

[0069] G Housing

[0070] GND protective conductor potential

[0071] HV+ positive high voltage potential

[0072] HV- negative high voltage potential

[0073] RF, RF' insulation resistance

[0074] Cy+ first capacity

[0075] Cy- second capacity

[0076] VP connection point

[0077] L1 , L4 low-voltage conductor

[0078] CL current limiting circuit

[0079] DCL1 , DCL2 electrical one-way element

[0080] R current limiting element

[0081] TVS1 , TVS2 voltage limiting element

Claims

Patent claims 1. Safety circuit (SI) for a vehicle electrical system (FB), where - the vehicle electrical system (FB) comprises a high-voltage electrical system, HV electrical system, (HV) which is arranged at least partially in a predetermined high-voltage area (HVB), and a low-voltage electrical system, LV electrical system, (LV) and one or more low-voltage conductors (L1, ... L4) lead out of the high-voltage area (HVB), - the low-voltage conductors (L1, ..., L4) are designed to derive a low-voltage signal potential and / or a low-voltage supply potential from the high-voltage range (HVB), at least in fault-free operation, - the safety circuit (Sl) has a reference potential connection for connection to a protective conductor potential (GND) of the vehicle, - the safety circuit (S1) comprises one or more diode half-bridge circuits, each having a first diode (D11, ..., D14) and a second diode (D21, ..., D24) connected in series, - the respective diode half-bridge circuit has a center terminal (M1, ..., M4), a first terminal connected to the cathode of the first diode (D11, ..., D14), and a second terminal connected to the anode of the second diode (D21, ..., D24), - the safety circuit (Sl) has one or more LV potential terminals for connecting the respective center terminals (M) to one of the low-voltage conductors (L1, ... L4), - the safety circuit (S1) has a current limiting circuit (CL) and the first terminals and the second terminals of the diode half-bridge circuits are connected to the reference potential terminal via the current limiting circuit (CL), which has a current limiting element (R) and a plurality of electrical one-way elements (DCL1, DCL2), so that in the event of a fault in which at least one of the low-voltage conductors (L1, ..., L4) conducts a positive high-voltage potential (HV+) or a negative high-voltage potential (HV-) out of the high-voltage area (HVB), a fault current flowing via the low-voltage conductor (L1, ..., L4) is diverted to the reference potential terminal.

2. Safety circuit (Sl) according to claim 1, wherein the current limiting element (R) has or is formed by a resistor, in particular an ohmic resistor.

3. Fuse circuit (S1) according to claim 1 or 2, wherein the plurality of electrical one-way elements (DCL1, DCL2) comprise a first electrical one-way element (DCL1) and a second one-way electrical element (DCL2), wherein the first one-way electrical element (DCL1) is arranged in a first branch and the second one-way electrical element (DCL2) is arranged in series with the current limiting element (R) in a second branch, and the second branch is arranged in parallel with the first branch.

4. Fuse circuit (S1) according to one of the preceding claims, wherein the plurality of electrical one-way elements (DCL1, DCL2) each have at least one diode or are formed by at least one diode.

5. Fuse circuit (Sl) according to one of the preceding claims, wherein the fuse circuit (Sl) has a first voltage limiting element (TVS1) and a second voltage limiting element (TVS2) and the first terminals of the diode half-bridge circuits are connected to a first terminal of the current limiting circuit (CL) via the first voltage limiting element (TVS1) and / or the second terminals of the diode half-bridge circuits are connected to a second terminal of the current limiting circuit (CL) via the second voltage limiting element (TVS2).

6. Fuse circuit (S1) according to claim 5, wherein the first voltage limiting element (TVS1) and / or the second voltage limiting element (TVS2) comprises a suppressor diode and / or a varistor and / or a protective diode and / or a Zener diode and / or a thyristor circuit or is formed by one or more such components.

7. Vehicle electrical system (FBS) comprising - a vehicle electrical system (FB) with a high-voltage electrical system, HV electrical system, (HV) which is arranged at least partially in a predetermined high-voltage range (HVB), and a low-voltage electrical system, LV electrical system, (LV), wherein one or more low-voltage conductors (L1, ... L4) lead out of the high-voltage range (HVB) and the low-voltage conductors (L1, ... , L4) are designed to lead out a low-voltage signal potential and / or a low-voltage supply potential from the high-voltage range (HVB), at least in fault-free operation, - a safety circuit (S1) according to one of the preceding claims 1 to 6, wherein at least some of the low-voltage conductors (L1, ..., L4) are each connected to one of the LV- Potential terminals are connected and the reference potential terminal is connected to the protective conductor potential (GND) of the vehicle.

8. Vehicle electrical system (FBS) according to claim 7, wherein the high-voltage electrical system (HV) comprises a positive high-voltage potential (HV'+) and a negative high-voltage potential (HV-), and the positive high-voltage potential (HV'+) is connected to the protective conductor potential of the vehicle via a first capacitance (Cy+) and the negative high-voltage potential (HV-) is connected to the protective conductor potential of the vehicle via a second capacitance (Cy-).

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