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 diode half-bridge circuit having a first diode (D11,..., D14) and a second diode (D21,..., D24) connected in series. Each diode half-bridge circuit has a midpoint connection (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). Each diode half-bridge circuit is connectable via its respective midpoint connection (M1,..., M4) to one of a plurality of low-voltage lines (L1,..., L4) leading from a high-voltage region (HVB) of the vehicle electrical system. The safety circuit (SI) comprises a current-limiting circuit (CL), and the first and second terminals of the diode half-bridge circuits are connected to a reference potential terminal via the current-limiting circuit (CL), the current-limiting circuit (CL) having a current-limiting element (R) and a plurality of electrical one-way elements (DCL1, DCL2), such that, in the event of a fault, a fault current flowing via the low-voltage line (L1,..., L4) when at least one of the low-voltage lines (L1,..., L4) leads a positive high-voltage potential (HV+) or a negative high-voltage potential (HV-) from the high-voltage region (HVB) is led to the reference potential terminal.

Description

Technical Field

[0001] The present invention relates to a protection circuit for a vehicle electrical system and a vehicle on-board electrical system arrangement having the protection circuit. Background Technology

[0002] It is known that vehicles are equipped with electric drive systems or other electrical components. To achieve high power, especially for traction, high voltages, such as 400 volts or higher, are used, which is the opposite of the usual 12-volt electrical system and may pose a danger to human health.

[0003] Therefore, vehicles with high-voltage electrical systems (i.e., high-voltage electrical systems - HV electrical systems) are equipped with insulation that isolates the HV electrical system from the rest of the electrical systems and from ground potential, especially from the vehicle chassis.

[0004] In addition, the vehicle includes control signals or sensor signals, or low-voltage power supply signals that are opposite to the high-voltage potential and are not specifically designed to prevent contact.

[0005] Because faults in insulation can lead to contact voltages that are harmful or even fatal to humans, additional protective measures are needed.

[0006] One object of the present invention is to provide a protection circuit that achieves improved protection against dangerous contact voltages with less space requirements and lower cost.

[0007] This task is accomplished through the features of the independent claim. Advantageous embodiments are specified in the dependent claims. Summary of the Invention

[0008] According to the first aspect, this task is solved by a protection 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 a portion of the high-voltage electrical system is arranged in a predetermined high-voltage area. One or more low-voltage conductors are led out from the high-voltage area. The low-voltage conductors specifically connect low-voltage components arranged in the high-voltage area to other low-voltage components arranged outside the high-voltage area. The low-voltage conductors are configured to lead low-voltage signal potentials and / or low-voltage supply potentials (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, particularly control signals, monitoring signals, sensor signals, etc.

[0009] The high-pressure area is particularly a closed or confined high-pressure area, or an enclosed space. The high-pressure area is, for example, surrounded by a shell.

[0010] The protection circuit has a reference potential terminal for connection to the vehicle's protective ground potential. This protective ground potential may specifically correspond to the vehicle ground potential or chassis potential.

[0011] The protection circuit includes one or more diode half-bridge circuits, each having a first diode and a second diode connected in series. Each diode half-bridge circuit has a midpoint connection, 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 protection circuit includes one or more LV potential connections for connecting each midpoint connection to one of the low-voltage conductors leading from the high-voltage region. The protection circuit includes a current-limiting circuit. The first and second terminals of each diode half-bridge circuit are connected to a reference potential terminal via the current-limiting circuit, which has a current-limiting element and multiple unidirectional elements, so that in the event of a fault, when at least one of the low-voltage conductors leads a positive or negative high-voltage potential from the high-voltage region, the fault current flowing through the low-voltage conductor is diverted via the reference potential terminal. The fault current is caused by the fault, particularly an insulation fault.

[0012] In the case of multiple diode half-bridge circuits, they are connected in parallel. Here, the cathodes of the first diodes are connected to each other, and the anodes of the second diodes are connected to each other. The diodes of each diode half-bridge circuit are connected in the same conduction direction.

[0013] The number of diode half-bridge circuits corresponds in particular to the number of low-voltage wires leading out from the high-voltage region, such that each diode half-bridge circuit is individually connected to one of the low-voltage wires.

[0014] The current-limiting circuit has a first connection terminal and a second connection terminal. The cathode of the first diode is connected to the first connection terminal of the current-limiting circuit, and the anode of the second diode is connected to the second connection terminal of the current-limiting circuit. The current-limiting element is preferably designed for high-current pulses because very high voltage peaks may occur on the current-limiting element.

[0015] The protection circuit has a first voltage limiting element and a second voltage limiting element. The first terminal of the diode half-bridge circuit is connected to the first connection terminal of the current limiting circuit via the first voltage limiting element, and / or the second terminal of the diode half-bridge circuit is connected to the second connection terminal of the current limiting circuit via the second voltage limiting element.

[0016] The protection circuit is particularly effective as a fault protection measure, limiting the contact voltage on the accessible terminals of voltage level A to less than 60 V DC voltage.

[0017] This invention is based on the understanding that low-voltage signal conductors and / or low-voltage potential conductors existing in high-voltage areas with high potential, and these conductors extending from high-voltage areas, are not specially protected and therefore pose a related danger in fault conditions, especially in the event of an insulation fault. The protection circuit provides special protection for the low-voltage conductors extending from the high-voltage area.

[0018] The special construction of the current-limiting circuit and its unidirectional electrical element allows the fault current to be diverted via the reference potential terminal with only one current-limiting element. That is, regardless of the polarity of the high-voltage potential present on the corresponding low-voltage conductor, the fault current is diverted via this single current-limiting element.

[0019] In this way, the protection circuit is configured to direct current to the protective grounding potential via the current limiting circuit when either of the two high-voltage potentials is introduced into at least one low-voltage conductor.

[0020] Especially in the event of a fault, the fault current flowing in the affected low-voltage conductor due to the discharge of existing capacitors located in the high-voltage area between the positive HV potential and the protective grounding potential and between the negative HV potential and the protective grounding potential can be led to the protective grounding terminal or the protective grounding potential via the protection circuit.

[0021] In at least one advantageous embodiment according to the first aspect, the current-limiting element comprises a resistor, or the current-limiting element is composed of a resistor. The resistor is preferably an ohmic resistor. The current-limiting element may be composed of one or more resistive components. The resistive components may be connected in series. In particular, multiple resistive components can be used to absorb / drain more potentially hazardous energy and / or improve tolerance to voltage surges of higher amplitude / peak value, such as 1,000 Vpeak instead of only 500 Vpeak.

[0022] In at least one embodiment according to the first aspect, the plurality of unidirectional electrical elements includes a first unidirectional electrical element and a second unidirectional electrical element. The first unidirectional electrical element is arranged in a first branch, and the second unidirectional electrical element is arranged in series with the current-limiting element in a second branch. The second branch is connected in parallel to the first branch.

[0023] In at least one embodiment according to the first aspect, each of the plurality of unidirectional electrical elements includes at least one diode, or is composed of at least one diode. Specifically, the first unidirectional electrical element includes at least one first diode, and / or the second unidirectional electrical element includes at least one second diode. The at least one first diode and the at least one second diode may be configured to be the same 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 also connected to the reference potential terminal.

[0024] In at least one embodiment according to the first aspect, the protection circuit has a first voltage-limiting element and a second voltage-limiting element, and a first terminal of the diode half-bridge circuit is connected to a first connection terminal of the current-limiting circuit via the first voltage-limiting element, and / or a second terminal of the diode half-bridge circuit is connected to a second connection terminal of the current-limiting circuit via the second voltage-limiting element. The first and second voltage-limiting elements are respectively configured to conduct when a threshold voltage or breakdown voltage is exceeded, and to not conduct or barely conduct when the voltage is below the threshold voltage or breakdown voltage.

[0025] The diode half-bridge circuit forms a network that allows multiple low-voltage wires to be protected to be connected to the first and second voltage-limiting elements, respectively. Thus, multiple low-voltage wires can be protected by the first and second voltage-limiting elements. This results in advantages in cost and installation space, as diodes are cheaper and smaller than voltage-limiting elements, especially when designed for peak loads of several or hundreds of amperes.

[0026] In at least one embodiment according to the first aspect, the first voltage-limiting element and / or the second voltage-limiting element respectively comprise a suppression diode and / or a varistor and / or a protection diode and / or a Zener diode and / or a silicon controlled rectifier circuit and / or a gas discharge tube and / or a spark gap and / or a DIAC, or are composed of one or more such components. The components may also be arranged in any combination to form the voltage-limiting element. The suppression diode may also be referred to as a transient voltage suppressor (TVS).

[0027] According to a second aspect, the present invention is characterized by a vehicle on-board electrical system arrangement. The vehicle on-board electrical system arrangement includes a vehicle electrical system having a high-voltage electrical system and a low-voltage electrical system at least partially arranged in a predetermined high-voltage area, wherein one or more low-voltage conductors are led out from the high-voltage area, and the low-voltage conductors are configured to respectively lead out a low-voltage signal potential and / or a low-voltage supply potential from the high-voltage area, at least during fault-free operation. Furthermore, the vehicle on-board electrical system arrangement has a protection circuit according to a first aspect, wherein at least a portion of the low-voltage conductors are respectively connected to one of the LV potentials, and the reference potential terminal is connected to the vehicle's protective ground potential (GND).

[0028] The advantageous implementation of the protection circuit according to the first aspect also applies to the second aspect.

[0029] In at least one advantageous embodiment according to the second aspect, the high-voltage electrical system includes a positive high-voltage potential and a negative high-voltage potential, wherein the positive high-voltage potential is connected to the vehicle's protective ground potential via a first capacitor, and the negative high-voltage potential is connected to the vehicle's protective ground potential via a second capacitor. Attached Figure Description

[0030] The embodiments of the present invention will be described in more detail below with reference to the schematic diagrams.

[0031] It is shown that: Figure 1 An exemplary embodiment of a vehicle on-board electrical system arrangement having a protection circuit for the vehicle electrical system. Figure 2 When a low-voltage conductor extending from the high-voltage area of ​​the vehicle's electrical system is mistakenly introduced into the positive high-voltage potential, the current flow in the vehicle's electrical system, and Figure 3 When a low-voltage conductor extending from the high-voltage area of ​​the vehicle's electrical system is mistakenly introduced into the negative high-voltage potential, the corresponding current flows in the vehicle's electrical system. Detailed Implementation

[0032] In the accompanying drawings, the same reference numerals are used for elements that have essentially the same function, but these elements do not necessarily have to be exactly the same in all details.

[0033] For the embodiments described herein or shown in the accompanying drawings, any direct electrical connection or coupling, i.e. any connection or coupling without any additional intermediate elements, can also be achieved by an indirect connection or coupling, i.e. a connection or coupling with one or more intermediate elements, and vice versa, as long as the general purpose of the connection or coupling, such as the transmission of a certain type of signal or the transmission of a certain type of information, is substantially maintained.

[0034] Figure 1 An exemplary embodiment of a vehicle on-board electrical system arrangement FBS is shown, having a protection circuit SI for a vehicle electrical system FB. The vehicle electrical system FB has a high-voltage electrical system (HV) HV and a low-voltage electrical system (LV) LV. The LV electrical system is coupled to the HV electrical system HV, for example, via an electrically isolated voltage converter (not shown in the figures).

[0035] The LV electrical system may include a 12 V, 13 V, 14 V, or 24 V, or 42 V, or 48 V network. The high-voltage area HVB includes at least one circuit with a rated voltage greater than 60 V, or at least 200 V, or at least 400 V, or at least 800 V.

[0036] The HV electrical system is at least partially arranged in a predetermined high-voltage area HVB. The high-voltage area HVB is, for example, surrounded by a housing G. In particular, the housing G may completely surround the high-voltage area HVB (with, if necessary, a closable opening for maintenance within the high-voltage area HVB).

[0037] The HV electrical system 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 capacitor Cy+ and at least one second capacitor Cy- are arranged. The at least one first capacitor Cy+ and the at least one second capacitor Cy- are connected to each other via a connection point VP, which is in turn connected to the protective ground potential GND. The protective ground potential GND may correspond to the vehicle ground potential or the chassis potential. The at least one first capacitor Cy+ and the at least one second capacitor Cy- are particularly used to suppress common-mode interference, and preferably each includes a Y capacitor.

[0038] One or more low-voltage components NV, such as control components, monitoring components and / or sensor components, are arranged in the high-voltage area HVB.

[0039] One or more low-voltage wires L1, ..., L4 are led out from the one or more low-voltage components NV, leaving the high-voltage area HVB, and specifically leaving the housing G. Figure 1The diagram exemplarily illustrates four low-voltage conductors L1, ..., L4. The low-voltage conductors L3 and L4 serve, for example, as communication signal conductors, such as for two-wire data transmission connections with symmetrical or asymmetrical signal transmission, for communication between one or more low-voltage components NV located within the high-voltage region HVB and other low-voltage components located outside the high-voltage region. For example, one of the low-voltage components NV includes a transmission component configured to transmit data according to the CAN communication protocol. One or more low-voltage conductors L1 and L2 serve, for example, as low-voltage potential conductors, such as as terminal 30, or as safety signal conductors, such as as interlock signal conductors.

[0040] Therefore, the low-voltage conductors L1, ..., L4 carry low-voltage signal potentials and / or low-voltage power supply potentials, such as +12 V or +5 V and ground, at least during fault-free operation, and are led out from the high-voltage area HVB.

[0041] In fault conditions, particularly in the event of an insulation fault, the resistance RF, RF' is represented by, for example, one of the low-voltage conductors L1, ..., L4 connected to one of the HV potentials HV-, HV+. Thus, the low-voltage conductor L1, ..., L4 carries the HV potentials HV-, HV+. Depending on the insulation fault condition (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 electrical system, or at least have a potential relative to the protective earth potential GND that is greater than a predetermined threshold voltage (e.g., > 60 V DC voltage) for the normal operation of the low-voltage conductors L1, ..., L4.

[0042] A significant amount of energy can be stored in the at least one first capacitor Cy+ and the at least one second capacitor Cy- or Y- anti-interference capacitor. Due to insulation failure, this energy can enter the LV electrical system LV from one of the HV potentials HV'+ and HV'- of the high-voltage electrical system via one of the low-voltage conductors L1, ..., L4. If this energy is "absorbed" by the human body, it is at least dangerous, and could even be fatal.

[0043] This energy can be diverted through the protection circuit SI.

[0044] Therefore, the protection circuit SI includes one or more diode half-bridge circuits, each diode half-bridge circuit having a first diode D11, ..., D14 and a second diode D21, ..., D24 connected in series. Each of the diode half-bridge circuits has a first terminal connected to the midpoint of M1, ..., M4, connected to the cathode of the first diode D11, ..., D14, and a second terminal connected to the anode of the second diode D21, ..., D24.

[0045] The midpoint connections M1, ..., M4 are respectively connected to one of the low-voltage conductors L1, ..., L4 drawn from the high-voltage region (HV) via LV potential connections. The first and second terminals of the diode half-bridge circuit are connected to the reference potential terminal via a current-limiting circuit CL, which has a current-limiting element R and multiple unidirectional electrical elements DCL1, DCL2. The reference potential terminal is connected to the vehicle's protective ground potential GND.

[0046] Preferably, the current-limiting circuit CL has a first unidirectional element DCL1 and a second unidirectional element DCL2. The first unidirectional element DCL1 is arranged in a first branch, and the second unidirectional element DCL2 is arranged in series with the current-limiting element R in a second branch, with the second branch connected in parallel to the first branch. The current-limiting element R preferably includes a resistor, particularly an ohmic resistor. The current-limiting element R is, for example, composed of one or more resistive components. The parallel circuit of the two branches is arranged between the first connection terminal of the current-limiting circuit CL and the reference potential terminal. The second connection terminal of the current-limiting circuit CL is arranged in the second branch, located between the current-limiting element R and the second unidirectional element DCL2.

[0047] The unidirectional electrical elements DCL1 and DCL2 are configured to allow current to flow in one direction and block it in the other. Each of the unidirectional electrical elements DCL1 and DCL2 has, for example, at least one diode, or is composed of at least one diode.

[0048] The positive HV potential HV+ and the negative HV potential HV- mistakenly introduced into the low-voltage conductors L1, ..., L4 or LV potential connection via the current-limiting element R of the current-limiting circuit CL are both led to the protective ground potential GND. Therefore, only one current-limiting element R is needed, and in particular, only one resistor is needed.

[0049] In one alternative embodiment, the first terminal of the diode half-bridge circuit is connected to the first connection terminal of the current limiting circuit CL via a first voltage limiting element TVS1, and / or the second terminal of the diode half-bridge circuit is connected to the second connection terminal of the current limiting circuit CL via a second voltage limiting element TVS2.

[0050] The voltage limiting element can also be called an overvoltage element. Each of the voltage limiting elements is configured to conduct when the threshold voltage or breakdown voltage is exceeded, and not conduct or hardly conduct when the threshold voltage or breakdown voltage is below the threshold voltage or breakdown voltage.

[0051] The threshold voltages of the first and second voltage limiting elements TVS1 and TVS2 are particularly lower than the rated voltage between the positive high voltage potential HV'+ and the negative high voltage potential HV'- in the high voltage electrical system, and preferably lower than the danger threshold, particularly 60 V. The threshold voltages of the voltage limiting elements can be between 10 V and 50 V, particularly between 35 V and 45 V.

[0052] The two voltage limiting elements, TVS1 and TVS2, each have, for example, suppression diodes.

[0053] The first unidirectional element DCL1 and the second unidirectional element DCL2 are preferably directly connected to the current-limiting element R. They force fault currents triggered by faults, particularly insulation faults, to flow through the voltage-limiting elements TVS1 and TVS2. Thus, they prevent fault currents from (partially) bypassing the current-limiting element R, which would otherwise result in high peak currents that would be critical / harmful to the components of the protection circuit SI.

[0054] In one alternative embodiment, a first and / or second device is provided, configured to detect current flow through the first voltage-limiting element TVS1 or the second voltage-limiting element TVS2. For example, an evaluation device is provided that compares the current flow to a threshold (e.g., 1 mA or 10 µA) and outputs a fault signal and / or causes the high-voltage electrical system HV to disconnect, for example, by controlling a disconnect switch in the high-voltage electrical system HV, or controlling a disconnect switch in at least one high-voltage potential HV'+, HV'- line carrying the high-voltage electrical system HV, and disconnecting the high-voltage region HVB of the vehicle electrical system from other components or connections (preferably all poles disconnected) during control.

[0055] Figure 2 This diagram illustrates the current flow in the vehicle electrical system FB when a positive high-voltage potential HV+ is incorrectly introduced into the first low-voltage conductor L1 extending from the high-voltage region HVB of the vehicle electrical system FB. The current flows out of the high-voltage region HVB from the first capacitor Cy+, through the first diode D11 of the diode half-bridge circuit, whose midpoint connection M1 is connected to the first low-voltage conductor L1 via the corresponding LV potential connection, then through the first voltage-limiting element TVS1 into the current-limiting element R, and finally through the second unidirectional element DCL2 to the reference potential.

[0056] Figure 3The diagram illustrates the current flow in the vehicle electrical system FB when a faulty low-voltage conductor L1 extending from the high-voltage region HVB of the vehicle electrical system is introduced at a negative high-voltage potential HV-. The fault current flows from the protective ground potential GND, through the first unidirectional element DCL1, the current-limiting element R, and the second voltage-limiting element TVS, through the second diode D21 of the diode half-bridge circuit. The midpoint connection M1 of this diode half-bridge circuit is connected to the low-voltage conductor L1 via the corresponding LV potential connection, and flows into the second capacitor Cy- in the high-voltage region HVB.

[0057] The special construction of the current-limiting circuit CL allows current limiting for diodes D11, ..., D14, D21, ..., D24 in the diode half-bridge circuit, and for voltage-limiting elements TVS1 and TVS2, to be achieved using only a single current-limiting element R, specifically a single resistor consisting of one or more resistive components. Advantageously, this saves installation space and cost compared to a solution using a separate current-limiting element R for each voltage-limiting element TVS1 and TVS2. This saving is significant because one or more resistors must be designed for large pulse currents to meet the required safety standards.

[0058] The description of the subject matter herein is not limited to the various specific embodiments. Features of different embodiments may be combined with each other within a technically reasonable scope to form further embodiments. For example, variations or modifications described with respect to one embodiment may also be applied to other embodiments, unless otherwise stated.

[0059] List of reference numerals D11, ..., D14 are the first diodes in the diode half-bridge circuit. The second diode in the diode half-bridge circuit, D21, ..., D24. Connect the midpoints of M1, ..., M4 NV low-voltage components LV low-voltage electrical system HV High Voltage Electrical System HVB High Voltage Area G housing GND protective grounding potential HV+ positive high voltage potential HV - Negative high voltage potential RF, RF' insulation resistance Cy+ First capacitor Cy- Second capacitor VP connection point L1, ..., L4 low-voltage conductors CL current limiting circuit DCL1, DCL2 unidirectional elements R Current limiting element TVS1, TVS2 voltage limiting components

Claims

1. A protection circuit (SI) for a vehicle electrical system (FB), wherein: - The vehicle electrical system (FB) has a high-voltage electrical system, an HV electrical system (HV), and a low-voltage electrical system, an LV electrical system (LV), which are at least partially arranged in a predetermined high-voltage area (HVB), and one or more low-voltage conductors (L1, ..., L4) are led out from the high-voltage area (HVB); - The low-voltage conductors (L1, ..., L4) are configured to conduct low-voltage signal potentials and / or low-voltage power supply potentials from the high-voltage zone (HVB) at least during fault-free operation. - The protection circuit (SI) has a reference potential terminal for connection to the vehicle's protective ground potential (GND); - The protection circuit (SI) includes one or more diode half-bridge circuits, each diode half-bridge circuit having a first diode (D11, ..., D14) and a second diode (D21, ..., D24) connected in series. - Each diode half-bridge circuit has a midpoint 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 protection circuit (SI) has one or more LV potential connections for connecting each of the midpoint terminals (M) to a low-voltage conductor (L1, ..., L4); - The protection circuit (SI) has a current limiting circuit (CL), and the first and second terminals of each of the diode half-bridge circuits are connected to the reference potential terminal via the current limiting circuit (CL). The current limiting circuit (CL) includes a current limiting element (R) and a plurality of unidirectional elements (DCL1, DCL2), such that in the event of a fault, when at least one of the low-voltage conductors (L1, ..., L4) carries a positive high-voltage potential (HV+) or a negative high-voltage potential (HV) from the high-voltage region (HVB), the current limiting circuit is connected to the reference potential terminal. When the fault current flows through the low-voltage conductors (L1, ..., L4), it is guided to the reference potential terminal.

2. The protection circuit (SI) according to claim 1, wherein, The current-limiting element (R) includes a resistor, preferably an ohmic resistor, or is composed of such a resistor.

3. The protection circuit (SI) according to claim 1 or 2, wherein, The plurality of unidirectional elements (DCL1, DCL2) includes a first unidirectional element (DCL1) and a second unidirectional element (DCL2). The first unidirectional element (DCL1) is disposed in the first branch, and the second unidirectional element (DCL2) is disposed in series with the current limiting element (R) in the second branch, and the second branch is disposed in parallel with the first branch.

4. The protection circuit (SI) according to any one of the preceding claims, wherein, The plurality of unidirectional elements (DCL1, DCL2) each include at least one diode, or are each composed of at least one diode.

5. The protection circuit (SI) according to any one of the preceding claims, wherein, The protection circuit (SI) has a first voltage limiting element (TVS1) and a second voltage limiting element (TVS2), and the first terminal of the diode half-bridge circuit is connected to the first connection terminal of the current limiting circuit (CL) via the first voltage limiting element (TVS1) and / or the second terminal of the diode half-bridge circuit is connected to the second connection terminal of the current limiting circuit (CL) via the second voltage limiting element (TVS2).

6. The protection circuit (SI) according to claim 5, wherein, The first voltage limiting element (TVS1) and / or the second voltage limiting element (TVS2) include a transient voltage suppression diode and / or a varistor and / or a protection diode and / or a Zener diode and / or a thyristor circuit, or are composed of one or more of the above devices.

7. A vehicle onboard electrical system layout (FBS), comprising: - A vehicle electrical system (FB) having a high-voltage electrical system, an HV electrical system (HV), and a low-voltage electrical system and an LV electrical system (LV) at least partially disposed within a predetermined high-voltage zone (HVB), wherein one or more low-voltage conductors (L1, ..., L4) are led out from the high-voltage zone (HVB), and the low-voltage conductors (L1, ..., L4) are configured to conduct low-voltage signal potentials and / or low-voltage power supply potentials from the high-voltage zone (HVB) respectively, at least during fault-free operation; - The protection circuit (SI) as described in any one of claims 1 to 6, wherein at least a portion of the low-voltage conductors (L1, ..., L4) are respectively connected to one of the LV potential connections, and the reference potential terminal is connected to the vehicle's protective ground potential (GND).

8. The vehicle onboard electrical system layout (FBS) according to claim 7, wherein, The high-voltage electrical system (HV) includes a positive high-voltage potential (HV'+) and a negative high-voltage potential (HV'). The positive high voltage potential (HV'+) is connected to the vehicle's protective ground potential via the first capacitor (Cy+), and the negative high voltage potential (HV') is... ) via the second capacitor (Cy Connect to the vehicle's protective grounding potential.

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