On-board electrical system for a vehicle

Abstract

Vehicle electrical system, including: - a high-voltage on-board electrical system (12), - a low-voltage on-board electrical system (14), - a voltage transformer unit (16) connecting the high-voltage on-board area (12) with the low-voltage on-board area (14), - at least one high-voltage consumer (20, 22) connected to the high-voltage on-board area (12) via a high-voltage fuse / switch unit (eF1, eF2), - at least one low-voltage consumer (24, 26) connected to the low-voltage on-board area (14) via a low-voltage fuse / switch unit (eF3, eF4), - at least one protective capacitor (C) assigned to the low-voltage on-board area (14).

Description

[0001] The present invention relates to an on-board electrical system for a vehicle, in particular a vehicle which can be operated electrically or partially electrically.

[0002] In vehicles, such as fully electric or partially electric vehicles, the electrical system can be configured to include a high-voltage section and a low-voltage section coupled to the high-voltage section. Electrical consumers requiring a higher voltage, such as steering or brake actuators, can be assigned to the high-voltage section. Electrical consumers requiring a lower voltage, such as sensors, can be assigned to the low-voltage section.

[0003] Connecting lines connecting electrical energy consumers to the respective vehicle electrical system areas can be arranged in a common line assembly, for example a common cable harness or the like, and thus be in direct physical contact with each other.

[0004] If a short circuit occurs in such a contact area between connecting lines assigned to different vehicle electrical system areas, an excessively high voltage arises very quickly in the area of ​​the connecting lines involved in the short circuit or in the area of ​​a consumer of electrical energy connected to the low-voltage vehicle electrical system area via one of these connecting lines, which can lead to damage to this consumer before a fuse unit assigned to the connecting line involved in the short circuit or to the consumer of electrical energy connected to the high-voltage vehicle electrical system area can trip on the high-voltage vehicle electrical system side.

[0005] The object of the present invention is to provide an on-board voltage network for a vehicle in which, in particular, consumers of electrical energy assigned to a low-voltage on-board area are reliably protected against an overvoltage occurring in the event of a short circuit.

[0006] According to the invention, this problem is solved by an on-board voltage network for a vehicle, comprising: - a high-voltage electrical system area, - a low-voltage on-board electrical system area, - a voltage converter unit connecting the high-voltage vehicle electrical system with the low-voltage vehicle electrical system, - at least one high-voltage consumer connected to the high-voltage vehicle electrical system via a high-voltage fuse / switch unit, - at least one low-voltage consumer connected to the low-voltage vehicle electrical system via a low-voltage fuse / switch unit, - at least one protective capacitor assigned to the low-voltage on-board electrical system.

[0007] The at least one protective capacitor integrated into the low-voltage electrical system acts as a phase shifter when a short circuit occurs between the low-voltage and high-voltage electrical systems. This shift causes a phase shift between the short-circuit current and the short-circuit voltage, particularly in the low-voltage system. The voltage rise is delayed relative to the current rise, so the voltage rise lags behind the current rise. This allows a high-voltage fuse / switch unit in the high-voltage system to trip, disconnecting the high-voltage load involved in the short circuit from the high-voltage system before the short-circuit voltage in the low-voltage system can damage it.

[0008] To reliably prevent an excessively strong or rapid voltage increase in the low-voltage vehicle electrical system in the event of a short circuit, it is proposed that the at least one protective capacitor in the low-voltage vehicle electrical system be connected in parallel to at least one low-voltage consumer, preferably to each low-voltage consumer.

[0009] To ensure reliable and reproducible disconnection and connection in the high-voltage on-board electrical system area, at least one, preferably every, high-voltage fuse / switch unit assigned to a high-voltage consumer can include an eFUSE fuse unit.

[0010] Reliable and reproducible disconnection and connection of one or more low-voltage consumers can be achieved in the low-voltage on-board electrical system if at least one, preferably each, low-voltage fuse / switch unit assigned to a low-voltage consumer includes an eFUSE fuse unit.

[0011] In order to reliably prevent excessive voltage rises in the low-voltage electrical system, ensuring an energy flow into or through the at least one protective capacitor, it is proposed that the at least one protective capacitor be designed such that, in the event of a short circuit between a high-voltage load and a low-voltage load, a short-circuit current via the high-voltage fuse / switch unit associated with the high-voltage load involved in the short circuit exceeds a high-voltage electrical system current threshold before a short-circuit voltage applied to the low-voltage load involved in the short circuit exceeds a low-voltage electrical system voltage threshold.

[0012] The nominal voltage of the high-voltage electrical system can be in the range of 48V. The nominal voltage of the low-voltage electrical system can be in the range of 12V.

[0013] In order to avoid damage, particularly in the area of ​​electrical energy consumers in the two vehicle electrical system areas, caused by the short-circuit current or short-circuit voltage in the event of a short circuit, it is proposed that the high-voltage vehicle electrical system current threshold be in the range of 40A to 60A, preferably around 50A, and / or that the low-voltage vehicle electrical system voltage threshold be in the range of 20V to 30V, preferably around 24V.

[0014] For a compact design of the on-board voltage network according to the invention, at least one high-voltage connecting line coupling a high-voltage consumer to the high-voltage on-board area and at least one low-voltage connecting line coupling a low-voltage consumer to the low-voltage on-board area can be arranged in a common line assembly, for example a common cable harness, and / or can be arranged in contact with each other at least in certain areas.

[0015] The voltage converter unit can include a DC / DC converter.

[0016] Since voltage fluctuations generally occur when converting a voltage to a different voltage level in such a DC / DC converter, it is further suggested that a smoothing capacitor be associated with the DC / DC converter.

[0017] To ensure a sufficiently large current flow to the at least one protective capacitor in the event of a short circuit, it is proposed that the capacitance of the at least one protective capacitor be greater than the capacitance of the at least one smoothing capacitor. This avoids the need for an excessively large smoothing capacitor.

[0018] In order to provide the respective nominal voltage in the two vehicle electrical system sections within the vehicle electrical system according to the invention, a high-voltage source can be assigned to the high-voltage section. The supply voltage provided by the high-voltage source, which essentially corresponds to the nominal voltage of the high-voltage section, can then be converted to the lower voltage level of the low-voltage section in the voltage converter unit.

[0019] In order to be able to charge the high-voltage source, designed for example as a battery or accumulator, for supplying the high-voltage and low-voltage vehicle electrical systems, it is proposed that the high-voltage source be rechargeable from an external power grid and / or by means of a vehicle generator and / or by means of a vehicle electric motor that can be operated as a generator.

[0020] To avoid an overload in the area of ​​a low-voltage fuse / switch unit due to the short-circuit current flowing towards the at least one protective capacitor in the event of a short circuit, it is proposed that at least one protective diode connected in parallel to at least one, preferably each, low-voltage fuse / switch unit be provided.

[0021] The invention further relates to a vehicle with an on-board voltage network constructed according to the invention.

[0022] The present invention is described in detail below with reference to the accompanying figures. These show: Fig. 1. A basic circuit diagram of an on-board voltage network for a vehicle; Fig. 2. A basic circuit diagram of a fuse / switch unit of the vehicle's electrical system. Fig. 1; Fig. 3 in its upper part the voltage curve in an on-board voltage network when a short circuit occurs for an on-board voltage network without a protective capacitor and for an on-board voltage network with a protective capacitor and in its lower part the current curve in the on-board voltage network when a short circuit occurs for an on-board voltage network without a protective capacitor and for an on-board voltage network with a protective capacitor.

[0023] The Fig. Figure 1 shows a schematic representation of a vehicle electrical system, generally designated 10. The electrical system 10 comprises a high-voltage section 12, which is designed, for example, for a nominal voltage of 48 V. The electrical system 10 also includes a low-voltage section 14, which is designed, for example, for a nominal voltage of 12 V. The high-voltage section 12 and the low-voltage section 14 are coupled to each other via a voltage converter unit 16, which includes a DC / DC converter. The nominal voltage of, for example, 48 V, provided in the high-voltage section 12 by a high-voltage source 18, is converted by the voltage converter unit 16 into the nominal voltage of the low-voltage section 14, i.e., for example, 12 V.Since voltage fluctuations can occur in the DC / DC converter during this process, a smoothing capacitor 36 coupled to ground can be assigned to the voltage converter unit, which essentially smooths the voltage provided by the DC / DC converter on the side of the low-voltage on-board area 14.

[0024] Several electrical energy consumers are assigned to the high-voltage electrical system section 12; in the illustrated example, two consumers 20 and 22. Similarly, several electrical energy consumers are assigned to the low-voltage electrical system section 14; in the illustrated example, two consumers 24 and 26. The consumers 20 and 22 assigned to the high-voltage electrical system section 12 are generally electrical energy consumers that require a higher voltage to operate than the consumers 24 and 26 assigned to the low-voltage electrical system section 14. For example, the consumers 20 and 22 assigned to or connected to the high-voltage electrical system section 12 can include actuators or their electric motors, which are used to operate system components of a vehicle, such as the steering system or the like.The consumers 24, 26 assigned to the low-voltage on-board area 14 can, for example, include various sensors or lighting fixtures.

[0025] In order to connect the various consumers 20, 22, 24, 26 to the vehicle electrical system 10, i.e. the high-voltage vehicle electrical system area 12 or the low-voltage vehicle electrical system area 14, or to disconnect them in a defined manner, for example in the event of a short circuit or a defect, high-voltage fuse / switch units eF1, eF2, and low-voltage fuse / switch units eF3, eF4 are provided for the consumers 20, 22, 24, 26. These high-voltage fuse / switch units eF1, eF2 and low-voltage fuse / switch units eF3, eF4 can be designed as so-called eFUSE fuse units, which are designed as semiconductor switches, for example MOSFET switches, to interrupt the line connection to a respective associated consumer of electrical energy, for example in the event of an excessively high current, or to restore the connection when such a defect is no longer present.Furthermore, the high-voltage fuse / switch units eF1, eF2 and the low-voltage fuse / switch units eF3, eF4 can be used to connect the connected loads 20, 22, 24, 26 to the high-voltage electrical system section 12 or the low-voltage electrical system section 14, respectively, when these loads are to be activated or operated. Conversely, they can be used to disconnect them from the respective electrical system section 12 or 14 when such operation is not required. The high-voltage fuse / switch units eF1, eF2 and the low-voltage fuse / switch units eF3, eF4 can thus be designed to function both as a fuse and as a switch. For example, one or all of these fuse / switch units can be integrated into a microprocessor or a corresponding electronic component.

[0026] In Fig. Figure 2 illustrates the basic structure of such an eFUSE fuse unit using the low-voltage fuse / switch unit eF3 as an example. This unit comprises one or more semiconductor switches 38 designed as MOSFET switches, which can be switched to conducting or non-conducting states by appropriate control at the gate region. A diode 40, or a diode function, is integrated into such a semiconductor switch 38. This diode fundamentally prevents current flow towards the respective associated electrical energy consumer (in the case of the low-voltage fuse / switch unit eF3, the consumer 24), but allows current flow in the opposite direction, i.e., towards the low-voltage vehicle electrical system 14.

[0027] In Fig. Figure 1 illustrates, using the two consumers 22 and 24 as examples, that a high-voltage connecting line 28 or a low-voltage connecting line 30, respectively, which connects to the high-voltage electrical system 12 or the low-voltage electrical system 14 via the respective associated fuse / switch unit eF2 or eF3, can be part of a common cable assembly 32. Such a cable assembly 32 can, for example, be designed as a wiring harness in which a multitude of lines, in particular several such connecting lines leading to electrical energy consumers from both the high-voltage electrical system 12 and the low-voltage electrical system 14, are combined. Since the connecting lines 28 and 30 combined in such a cable assembly 32 are positioned very close to each other, there is a possibility that these connecting lines 28 and 30 may touch each other, at least partially.Due to such contact between the various vehicle electrical system areas 12, 14 and the connecting lines 28, 30, there is also the possibility that a short circuit may occur in such a line assembly 32 through a direct electrically conductive connection between the high-voltage vehicle electrical system area 12 and the low-voltage vehicle electrical system area 14 via connecting lines 28, 30 touching each other.

[0028] The Fig. Figure 3 illustrates how the short-circuit current and short-circuit voltage develop in the vehicle electrical system 10 when such a short circuit occurs. It is assumed that such a short circuit occurs between connecting lines 28 and 30 at time t0. Before this short circuit occurs at time t0, the voltage U applied to the load 24 via connecting line 30 is essentially constant at the nominal voltage of the low-voltage vehicle electrical system 14. The electric current I flowing in connecting line 28 via the high-voltage fuse / switch unit eF2 and connecting line 28 or the load 22 is at a substantially constant value, which is necessary for the proper operation of the load 28.

[0029] When a short circuit occurs, the short-circuit current flowing via the high-voltage fuse / switch unit eF2 and the connecting line 28 into the connecting line 30 and thus into the low-voltage on-board area 14 increases according to curve K1. Fig. 3. Along with this increase in current, the short-circuit voltage U applied to the consumer 24 via the connecting line 30 in the low-voltage on-board electrical system area 14 increases according to curve K2. This is clearly visible in Fig. 3. Due, among other things, to the inductances of the connecting lines 28 and 30, the short-circuit voltage rises significantly faster than the short-circuit current. This results in a low-voltage on-board voltage threshold Us being exceeded at time t1, which is significantly before time t2, at which the short-circuit current, which also flows through the high-voltage fuse / switch unit eF2, exceeds a high-voltage on-board current threshold I. S exceeds. This high-voltage on-board area current threshold Is defines the current which leads to the tripping of the high-voltage fuse / switch unit eF2 in its function as a fuse and thus to the disconnection of the connecting line 28 and the consumer 22 from the high-voltage on-board area 12.

[0030] Exceeding the low-voltage on-board voltage threshold Us, which may be around 24V, for example, before the high-voltage fuse / switch unit eF2 trips and the current flow is interrupted via the short circuit between the connecting lines 20, 30, can lead to damage to the consumer 24 which is subjected to the voltage exceeding the low-voltage on-board voltage threshold Us.

[0031] To prevent this, a protective capacitor C is provided in the vehicle electrical system 10 in connection with the low-voltage electrical system section 14, or connected in parallel to the various consumers 24, 26. Since, regardless of whether the low-voltage fuse / switch unit eF3 associated with the low-voltage connecting line 30 or the consumer 24 is switched on to connect the consumer 24 to the low-voltage electrical system 14, or is open (i.e., in a non-conductive state) to deactivate the consumer 24, a current flow from the low-voltage connecting line 30 into the low-voltage electrical system section 14 to the protective capacitor C is possible via the integrated diode 40, the protective capacitor C is charged by the short-circuit current flowing through the short circuit in the area of ​​the cable assembly 32.This leads to a phase shift between the short-circuit current and the short-circuit voltage occurring particularly in the area of ​​connecting line 30, in that the current flowing to charge the protective capacitor C leads the voltage rise. This is shown in . Fig. 3. This is illustrated using curves K3 and K4. It is clearly visible that the short-circuit current already exceeds the high-voltage on-board voltage threshold Is at time t3, while the low-voltage on-board voltage threshold Us is only exceeded later at time t4, or would only be exceeded if the current flow continued.

[0032] However, exceeding the high-voltage on-board current threshold Is leads to the tripping of the high-voltage fuse / switch unit eF2 at time t3, thus disconnecting the connecting line and therefore also the short circuit from the high-voltage on-board area 12. This prevents a further voltage increase in the low-voltage on-board area 14, in particular in the low-voltage connecting line 30 and thus at the consumer 24, before the potentially critical low-voltage on-board voltage threshold Us, which could damage the consumer 24, is reached.

[0033] To prevent potential damage to the low-voltage fuse / switch unit eF3, particularly to the integrated diode 40, which could occur due to the comparatively high current when the short-circuit current is discharged via the unit, a protective diode 34 is connected in parallel to the low-voltage fuse / switch unit eF3. This protective diode 34 allows current to flow from the connecting line 30 into the low-voltage on-board area 14 to the protective capacitor C, but blocks current flow in the opposite direction, thus relieving the low-voltage fuse / switch unit eF3 in the event of a short circuit.

[0034] To ensure that diverting the short-circuit current to the protective capacitor C creates a phase shift between the short-circuit current and the short-circuit voltage sufficient to trigger the high-voltage fuse / switch unit eF2 before reaching the low-voltage electrical system voltage threshold Us, the protective capacitor C must have a capacitance sufficient to guarantee that it is not fully charged before the high-voltage electrical system current threshold Is is exceeded or the low-voltage electrical system voltage threshold Us is reached. This may require providing several such protective capacitors C for the low-voltage electrical system 14 and connecting them, for example, in parallel to each other. The capacitance of the protective capacitor C must be...the total capacitance of all protective capacitors C is designed to be greater than the capacitance of the smoothing capacitor 36 or, if several such smoothing capacitors 36 are provided, the total capacitance of all smoothing capacitors 36.

[0035] Finally, it should be noted that for several or all of the connecting lines, for example those grouped into a cable assembly 32, particularly in the low-voltage electrical system section 14, such protective measures may be provided to protect the respective low-voltage loads from overvoltage occurring in the event of a short circuit. In particular, it may be provided that a protective diode is connected in parallel to the respective low-voltage fuse / switch unit for several or each low-voltage load. It should also be noted that, in addition to the high-voltage electrical system section 12 and the low-voltage electrical system section 14, the electrical system 10 may also include an electrical system section in which one or more traction motors of a fully electric or partially electric vehicle are powered by a traction battery.

Claims

[1] Vehicle electrical system, comprising: - a high-voltage on-board electrical system (12), - a low-voltage on-board electrical system (14), - a voltage transformer unit (16) connecting the high-voltage on-board area (12) with the low-voltage on-board area (14), - at least one high-voltage consumer (20, 22) connected to the high-voltage on-board area (12) via a high-voltage fuse / switch unit (eF1, eF2), - at least one low-voltage consumer (24, 26) connected to the low-voltage on-board area (14) via a low-voltage fuse / switch unit (eF3, eF4), - at least one protective capacitor (C) assigned to the low-voltage on-board area (14). [2] On-board voltage network according to claim 1, characterized by, that the at least one protective capacitor (C) in the low-voltage on-board area (14) is connected in parallel to at least one low-voltage consumer (24, 26), preferably to each low-voltage consumer (24, 26). [3] On-board voltage network according to claim 1 or 2, characterized by , that at least one, preferably each, high-voltage fuse / switch unit (eF1, eF2) provided for use with a high-voltage consumer (20, 22) includes an eFUSE fuse unit. [4] On-board voltage network according to one of claims 1-3, characterized by , that at least one, preferably each, low-voltage fuse / switch unit (eF3, eF4) provided for use with a low-voltage consumer (24, 26) includes an eFUSE fuse unit. [5] On-board voltage network according to one of claims 1-4, characterized by, that the at least one protective capacitor (C) is designed such that, in the event of a short circuit occurring between a high-voltage load (22) and a low-voltage load (24), a short-circuit current via the high-voltage fuse / switch unit (eF2) associated with the high-voltage load (22) involved in the short circuit exceeds a high-voltage on-board area current threshold (I) s ) before a short-circuit voltage applied to the low-voltage consumer (24) involved in the short circuit exceeds a low-voltage on-board area voltage threshold (Us). [6] On-board voltage network according to one of claims 1-5, characterized by , that the nominal voltage of the high-voltage vehicle electrical system (12) is in the range of 48V, or / and that the nominal voltage of the low-voltage vehicle electrical system (14) is in the range of 12V. [7] On-board voltage network according to claim 5 and claim 6, characterized by, that the high-voltage on-board current threshold (Is) is in the range of 40A to 60A, preferably at about 50A, and / or that the low-voltage on-board voltage threshold (Us) is in the range of 20V to 30V, preferably at about 24V. [8] On-board voltage network according to one of claims 1-7, characterized by , that at least one high-voltage connecting line (28) coupling a high-voltage consumer (22) to the high-voltage vehicle electrical system (12) and at least one low-voltage connecting line (30) coupling a low-voltage consumer (24) to the low-voltage vehicle electrical system (14) are arranged in a common line assembly (32) and / or are in contact with each other at least in some areas. [9] On-board voltage network according to one of claims 1-8, characterized by , that the voltage converter unit (16) includes a DC / DC converter (DC / DC). [10] On-board voltage network according to claim 9, characterized by, that at least one smoothing capacitor (36) is assigned to the DC / DC converter (DC / DC). [11] On-board voltage network according to claim 10, characterized by , that the capacitance of the at least one protective capacitor (C) is greater than the capacitance of the at least one smoothing capacitor (36). [12] On-board voltage network according to one of claims 1-11, characterized by , that a high voltage source (18) is assigned to the high voltage on-board area (12). [13] On-board voltage network according to claims 1-12, characterized by , that the high voltage source (18) can be charged from an external voltage network and / or by means of a vehicle generator and / or by means of a vehicle electric motor that can be operated as a generator. [14] On-board voltage network according to claims 1-13, characterized by , that at least one protection diode (34) connected in parallel to at least one, preferably each, low-voltage fuse / switch unit (eF3, eF4) is provided. [15] Vehicle comprising an on-board electrical system (10) according to any one of claims 1-14.

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