On-board electrical system for an electrically powered motor vehicle

Abstract

On-board electrical system (2) for an electrically powered motor vehicle, comprising - a high-voltage electrical system (2a) with a traction battery (4) which has at least a first energy storage block (6) and a second energy storage block (8), - a DC-DC converter device (36) which has a first output (42) for providing a low-voltage voltage for a low-voltage consumer (46), in particular a safety-relevant one, of a low-voltage network (2b) and a second output (48) for providing a low-voltage voltage for the low-voltage consumer (46), and which includes at least one input (52, 72) for supplying the voltage to the first energy storage block (6) and at least one input (54, 74) for supplying the voltage to the second energy storage block (8), - wherein the first output (42) and the second output (48) are each coupled to one of the inputs (52, 72) for the first energy storage block (6) as well as to one of the inputs (54, 74) for the second energy storage block (8).

Description

[0001] The invention relates to an on-board power system for an electrically powered motor vehicle. Furthermore, the invention relates to an electrically powered motor vehicle with such an on-board power system.

[0002] An electrically powered motor vehicle typically has an on-board electrical system with a traction battery (high-voltage battery, HV battery). An electrically powered motor vehicle is understood to mean, in particular, an electric vehicle that stores the energy required for propulsion solely in the traction battery (BEV, battery electric vehicle), an electric vehicle with a range extender (REEV, range extended electric vehicle), a hybrid vehicle (HEV, hybrid electric vehicle), a plug-in hybrid vehicle (PHEV, plug-in hybrid electric vehicle), and / or a fuel cell vehicle (FCEV, fuel cell electric vehicle), which temporarily stores the electrical energy generated by a fuel cell in the traction battery.

[0003] The traction battery provides a high voltage for a part of the vehicle's electrical system known as the high-voltage network or high-voltage on-board network, i.e., a voltage greater than 60 V. Thus, the traction battery can be used to supply energy to a high-voltage consumer, such as an electric motor for driving the vehicle.

[0004] For example, the vehicle electrical system additionally has a part referred to as a low-voltage network or low-voltage vehicle electrical system with a voltage that is less than 60 V, in particular equal to 12 V or 24 V, into which one or more safety-relevant low-voltage consumers are connected.

[0005] In particular, a "safety-relevant load" is defined as a load that fulfills a function to protect, in particular the safety and integrity of, the motor vehicle, its occupants, and / or other road users. Such safety-relevant loads are assigned to a risk class, for example, according to ISO 26262 (more generally, IEC 61508).

[0006] Safety-relevant consumers must be distinguished from convenience consumers, which fulfill one or more convenience functions. For example, a seat adjustment or an audio system is a convenience consumer. To ensure a correspondingly low failure probability of a safety-relevant consumer, it is advisable for these to have a redundant power supply. Such a redundant power supply for safety-relevant low-voltage consumers is relevant, for example, for autonomous or semi-autonomous operation of the vehicle or for a so-called X-by-wire system, such as steer-by-wire.

[0007] EP 3 912 843 A1 discloses a system for a vehicle. This system comprises a first and a second high-voltage battery unit. These are coupled to two DC-DC converters for the redundant provision of a low-voltage supply.

[0008] DE 10 2020 211 218 A1 discloses a battery comprising at least one battery cell and two DC / DC converters. The lower-power DC / DC converter is used, for example, only in standby mode to supply power to loads.

[0009] The invention is based on the object of providing a suitable on-board power supply. In particular, it is intended to provide a redundant power supply for a safety-relevant low-voltage consumer in a reliable manner. Furthermore, an electrically powered motor vehicle with such an on-board power supply is to be specified.

[0010] With regard to the electrical system, this object is achieved according to the invention by the features of claim 1. With regard to the electrically powered motor vehicle, this object is achieved according to the invention by the features of claim 9. Advantageous embodiments and further developments are the subject of the dependent claims. The statements made in connection with the electrical system also apply mutatis mutandis to the electrically powered motor vehicle, and vice versa.

[0011] The electrical and / or electronic on-board power system is intended and configured for an electrically powered motor vehicle. For this purpose, the on-board power system comprises a high-voltage battery, also known as a traction battery, which provides a voltage greater than 60 V, for example, 400 V or 800 V, for a high-voltage on-board power system. The traction battery comprises at least a first energy storage block (first energy storage bank) and a second energy storage block (second energy storage bank).

[0012] Each of the energy storage blocks has at least one battery cell, in particular a lithium-ion battery cell. Suitably, the respective energy storage block comprises more than one, in particular a plurality of battery cells, which are connected in series and / or parallel to one another. For example, the battery cells are combined to form one or more than one (cell) module. Preferably, the first and second energy storage blocks are constructed identically, i.e., have the same number of battery cells that are interconnected in the same way. Thus, the first and second energy storage blocks provide the same voltage. Preferably, each of the energy storage blocks provides a voltage greater than 60V.

[0013] The on-board electrical system further comprises a DC-DC converter device. This comprises a first output, in particular designed as an output stage, for a low-voltage consumer of a low-voltage on-board electrical system, in particular a safety-relevant one, and a second output, in particular designed as an output stage, for the low-voltage consumer. A low-voltage voltage, i.e., a voltage of less than 60 V, in particular 12 V, 24 V, or 48 V, is expediently provided at the first output and the second output. The low-voltage consumer is thus redundant, i.e., can be supplied with electrical energy via both the first output and the second output. As a result, the low-voltage consumer, which is particularly safety-relevant, can be operated comparatively safely using the DC-DC converter device.

[0014] Furthermore, the DC-DC converter device comprises at least one input, in particular an input stage, for the first energy storage block and at least one (further) input, in particular an input stage, for the second energy storage block. In summary, the DC-DC converter device comprises at least two inputs for the energy storage blocks of the traction battery. In particular, the first energy storage block and the second energy storage block are connected to the respective inputs.

[0015] In summary, the high-voltage on-board network (high-voltage network) and the low-voltage on-board network (low-voltage network) are connected to each other using the DC-DC converter device.

[0016] The first output and the second output are each coupled to the input (or to one of the at least one inputs) for the first energy storage block as well as to the input (or to one of the at least one inputs) for the second energy storage block, in particular in terms of voltage conversion and / or power transmission.

[0017] In particular, the DC-DC converter device is designed such that the low-voltage supply at the first output can be effected by converting the voltage, in particular reducing the voltage, of the first energy storage block and additionally or alternatively by converting the voltage of the second energy storage block. Analogously, the DC-DC converter device is designed such that the low-voltage supply at the second output can be effected by converting the voltage, in particular reducing the voltage of the first energy storage block and additionally or alternatively by converting the voltage of the second energy storage block.Thus, in the event of a fault in one of the energy storage blocks, for example, a short circuit in one of its battery cells, the voltage for the low-voltage consumer can be provided by converting the voltage of the other energy storage block. This ensures particularly safe operation of the low-voltage consumer, even in the event of a fault in one of the energy storage blocks.

[0018] For example, the DC-DC converter device is designed as a so-called multi-input / multi-output DC-DC converter, which comprises the two outputs as well as the inputs for the energy storage blocks. According to an advantageous embodiment, the DC-DC converter device has a first DC-DC converter unit and a second DC-DC converter unit, preferably separate from the first DC-DC converter unit. The first DC-DC converter unit comprises the first output, an input (hereinafter also referred to as the first input) for the first energy storage block, and an input (hereinafter also referred to as the second input) for the second energy storage block. Thus, the first energy storage block is electrically connected to the first input, and the second energy storage block is electrically connected to the second input.In summary, the first DC-DC converter unit has two inputs, in particular each designed as input stages, namely the first and the second input.

[0019] The second DC-DC converter unit comprises the second output, an input for the first energy storage block—referred to here and below as the third input for the purpose of better differentiation—and an input for the second energy storage block—referred to here and below as the fourth input for the purpose of better differentiation. Thus, the first energy storage block is electrically connected to the third input, and the second energy storage block is electrically connected to the fourth input. In summary, the second DC-DC converter unit has two inputs, in particular designed as input stages, namely the third and fourth inputs.

[0020] In particular, the first and second DC-DC converter units each form a multi-input DC-DC converter.

[0021] When configuring the DC-DC converter device with the first DC-DC converter unit and the second DC-DC converter unit, operation of the low-voltage load using the other DC-DC converter unit is advantageously enabled even in the event of a defect or failure of one of the two DC-DC converter units. This advantageously enables comparatively safe and reliable operation of the low-voltage load, particularly the safety-relevant one.

[0022] In summary, the first and second DC-DC converter units each have an input for the first energy storage block and an input for the second energy storage block. Thus, even in the event of a fault or defect in one of the energy storage blocks, the low-voltage consumer can be operated redundantly using both DC-DC converter units and the other energy storage block.

[0023] According to an advantageous embodiment, the low-voltage electrical system, i.e., the part of the electrical system whose output is electrically connected to the DC-DC converter device, is battery-free. In other words, no battery, in particular no starter battery, for example no lithium-ion battery or lead battery, is connected to the low-voltage electrical system. The supply of the (low-voltage) consumer(s) of the low-voltage electrical system, i.e., the consumer(s) connected to the low-voltage electrical system, is provided solely from the high-voltage electrical system via the DC-DC converter device. Due to the (multiply) redundant power supply of the low-voltage consumer via the DC-DC converter device, such a battery is not necessary and is expediently not installed, thus saving costs and correspondingly providing more installation space.

[0024] According to a practical embodiment, the first output is connected to a first connection for the low-voltage consumer. The second output is connected to a second connection for the low-voltage consumer, separate from the first connection. In particular, the first connection is not electrically connected to the second connection. The low-voltage consumer can therefore be connected to two separate connections for its power supply. In this way, in the event of a fault in a section of the low-voltage vehicle electrical system that is electrically connected to one of the connections, the low-voltage consumer can be operated using the other connection and the DC-DC converter device.

[0025] This also applies analogously to a fault in the communications network, especially the bus system such as CAN. In summary, comparatively safe operation of the low-voltage consumer is achieved even in the event of a fault in the low-voltage network.

[0026] The (traction) battery expediently has a first main contactor and / or a second main contactor, by means of which the energy storage blocks can be separated from a positive battery terminal or from a negative battery terminal. In this way, in the event of a fault in the high-voltage electrical system, in particular a fault in a high-voltage consumer and / or the traction battery, their energy storage banks can be disconnected from the rest of the high-voltage electrical system. For example, an additional isolating element for protection, in particular a pyro-fuse or a fuse, is provided so that in the event of a fault, in particular a short circuit, the traction battery—even if the main contactor is welded shut—can be separated from the rest of the high-voltage electrical system.

[0027] According to an advantageous embodiment of the vehicle electrical system, the first main contactor is connected between the first energy storage block and the input(s) of the DC-DC converter device for the first energy storage block. Preferably, a series circuit comprising a first precharging contactor and a precharging resistor is connected in parallel with the first main contactor. Additionally or alternatively, the second main contactor is connected between the second energy storage block and the input(s) of the DC-DC converter device for the second energy storage block. Preferably, a series circuit comprising a second precharging contactor and a precharging resistor is connected in parallel with the second main contactor.

[0028] In other words, the first energy storage block can be connected to the corresponding input(s) of the DC-DC converter device by means of the first main contactor and / or the first pre-charging contactor. Additionally or alternatively, the second energy storage block can be connected to the corresponding input(s) of the DC-DC converter device by means of the second main contactor and / or the second pre-charging contactor.

[0029] Using the pre-charging contactor(s), the DC-DC converter device, in particular its capacitive components, can be pre-charged so that damage due to a comparatively high inrush current is avoided.

[0030] Alternatively, if the DC-DC converter device is designed in such a way that pre-charging is not necessary, for example, it has only comparatively small capacities or these can be switched off, the first energy storage block and the second energy storage block are connected directly to the respective input.

[0031] According to an advantageous development, the on-board electrical system has a third DC-DC converter unit, in particular designed as a multi-output DC-DC converter. This is particularly preferably separate from the DC-DC converter device, i.e. structurally distinct from it. The traction battery, preferably the energy storage blocks, in particular connected in series with one another, are connected to its input, which is designed in particular as an input stage. The traction battery is preferably connected directly to the input, in particular not via one of the or both main contactors, or merely via an isolating element, for example a fuse. Furthermore, the third DC-DC converter unit comprises two outputs for the low-voltage on-board electrical system, whereby these outputs are referred to here and below as the third output and the fourth output for the purpose of better differentiation.The input of the third DC-DC converter unit is coupled to both outputs in terms of voltage conversion and / or power transmission, so that even if one of these two outputs is defective, a voltage can be provided at the other output.

[0032] At most, the third output is electrically connected to the first connection for the low-voltage consumer and the fourth output is electrically connected to the second connection for the low-voltage consumer.

[0033] The third DC-DC converter unit makes it possible to feed electrical energy into the low-voltage network even in the event of a fault in the high-voltage on-board network, in which the traction battery is disconnected from the rest of the high-voltage on-board network by the main contactor(s) blocking the current.

[0034] The third DC-DC converter unit is preferably designed and configured for the transmission of comparatively low power levels. For this purpose, the maximum output power of the third DC-DC converter unit is smaller, in particular by a factor of 10 to 50, than that of the DC-DC converter device, in particular than that of the first DC-DC converter unit and / or second DC-DC converter unit. In this case, the third DC-DC converter unit serves only to supply the low-voltage load with a quiescent current, for example, to prevent the memory of the low-voltage load from being erased.

[0035] In a suitable embodiment, the first energy storage block and the second energy storage block are electrically separable from one another. For this purpose, a switch, in particular a relay or a circuit breaker, is expediently connected between the energy storage blocks, which are connected in series in a suitable manner. If the traction battery comprises additional energy storage blocks, these are particularly preferably also separable from one another, from the first and / or the second energy storage block.

[0036] Consequently, by means of this separation, in particular by means of a current-blocking circuit of the switch, in the event of a defect in one of the energy storage blocks, for example in the event of a short circuit in one of its battery cells, an impairment of the other energy storage block and / or a propagation of the error / defect to it can be advantageously avoided.

[0037] A further aspect of the invention relates to an electrically driven motor vehicle with an on-board network which is designed according to one of the variants presented above.

[0038] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In the drawings: Fig. 1 shows a block diagram of an on-board electrical system for an electrically powered motor vehicle according to a first embodiment, wherein a traction battery comprises a first and a second energy storage block, wherein the first energy storage block is connected by means of a contactor to an input of a first DC-DC converter unit of a DC-DC converter device and to an input of a second DC-DC converter unit of the DC-DC converter device, wherein the second energy storage block is connected by means of a further contactor to a further input of the first DC-DC converter unit and to a further input of the second DC-DC converter unit, and wherein the outputs of the DC-DC converter units for a low-voltage consumer are each coupled to their inputs, Fig. 2 the vehicle electrical system according to a second embodiment, wherein the energy storage blocks are directly connected to the inputs of the first and second DC-DC converter units, and Fig. 3 the vehicle electrical system according to a third embodiment, wherein the DC-DC converter device is designed as a multi-input-multi-output DC-DC converter.

[0039] Corresponding parts and sizes are always provided with the same reference symbols in all figures.

[0040] In the Fig. 1 schematically shows an on-board electrical system 2 for an electrically powered motor vehicle. This comprises a high-voltage on-board electrical system 2a and a low-voltage on-board electrical system 2b. A traction battery 4 of the on-board electrical system 2 comprises a first energy storage block 6 and a second energy storage block 8, wherein the two energy storage blocks 6, 8 are connected in series with one another, for example, according to this embodiment. Each of the energy storage blocks 6, 8 comprises a plurality of battery cells 10 that are connected in series and / or parallel to one another. For the sake of better clarity, only two battery cells 10 connected in series per energy storage block 6, 8 are shown in all figures by way of example. The two energy storage blocks 6, 8 preferably provide the same voltage.

[0041] The traction battery 4 provides a high-voltage voltage, i.e., a voltage greater than 60V, in particular 800V, at its battery terminals 12a, 12b. A first main contactor 14 is connected between the first energy storage block 6 and one of the battery terminals, namely the positive battery terminal 12a. Similarly, a second main contactor 16 is connected between the second energy storage block 8 and a second of the battery terminals, namely the negative battery terminal 12b. The battery terminals 12a, 12b can be switched off, i.e., electrically separated, from the energy storage blocks 6, 8 using the two main contactors 14, 16, particularly in the event of a fault in the high-voltage on-board electrical system 2a.

[0042] The traction battery 4 is further configured such that only the voltage provided by the first energy storage block 6, or only the voltage provided by the second energy storage block 8, or the voltage of the two energy storage blocks 6, 8 connected in series, i.e., the sum of their voltages, is applied to the battery terminals 12a, 12b. Three switches are provided for this purpose: a first switch 18, a second switch 20, and a third switch 22. The first switch 18 is connected between the two energy storage blocks 6, 8. Thus, the first energy storage block 6 can be electrically separated from the second energy storage block 8 using the first switch 18. The first switch 18 is configured, for example, as a contactor or a circuit breaker.In this way, the first and second energy storage blocks 6,8 can be electrically separated from one another in the event of a fault in one of these energy storage blocks, so that an influence on the intact energy storage block 6,8 or a propagation of the defect to the intact energy storage block 6,8 is avoided.

[0043] The second switch 20 is connected in a current path that runs between a node point arranged between the first energy storage block 6 and the first contactor 14 and a node point arranged between the second energy storage block 8 and the first switch 18.

[0044] The third switch 22 is connected in a current path that runs between a node point arranged between the second energy storage block 8 and the second contactor 16 and a node point arranged between the first energy storage block 6 and the first switch 18.

[0045] To disconnect the first energy storage block 6, particularly in the event of a fault / defect, the first switch 18 and the third switch 22 are switched to block current, and the second switch 20 is switched to conduct current. To disconnect the second energy storage block 8, particularly in the event of a fault / defect, the first switch 18 and the second switch 20 are switched to block current, and the third switch 22 is switched to conduct current. The voltage of the energy storage block 6 or 8 that is not switched off is then supplied to the DC-DC converter device 36.

[0046] A current-blocking circuit of the second switch 20 and the third switch 22 and a current-conducting circuit of the first switch 18 causes the energy storage blocks 6, 8 to be connected in series between the two battery terminals 12a, 12b.

[0047] A high-voltage consumer 24, for example, an inverter with an electric motor connected to it for driving the vehicle, is connected to the two battery terminals 12a, 12b. Furthermore, a charging device 26 for charging the traction battery 4 is electrically connected to the battery terminals 12a, 12b.

[0048] A fuse 32, in particular an active fuse, is connected between the first battery terminal 12a and the high-voltage consumer 24 or the charging device 26, and a further fuse 34 is connected between the second battery terminal 12b and the high-voltage consumer 24 or the charging device 26.

[0049] A DC-DC converter device 36 is connected in the vehicle electrical system 2. This comprises a first DC-DC converter unit 38 and a second DC-DC converter unit 40, each of which is designed as a multi-input DC-DC converter. The first DC-DC converter unit 38 comprises a (first) output 42, which is electrically connected to a first terminal 44 for a safety-relevant low-voltage consumer 46. The second DC-DC converter unit 40 comprises a (second) output 48, which is electrically connected to a second terminal 50 for the safety-relevant low-voltage consumer 46.

[0050] The first and second terminals 44, 50, in particular their positive terminal points 44a, 50a, are not electrically coupled to each other. Only their negative terminal points 44b, 50b are connected to reference potential, in particular to the potential of the vehicle chassis. Thus, the low-voltage consumer 46 can be supplied with power via the two separate terminals 44, 50.

[0051] The first DC-DC converter unit 38 comprises a (first) input 52 for the first energy storage block 6 and a (second) input 54 for the second energy storage block 8. The first output 44 is coupled to both the first input 52 and the second input 54 for voltage conversion or power transmission purposes. Thus, using the first DC-DC converter unit 38, both the voltage provided by the first energy storage block 6 and the voltage provided by the second energy storage block 8 can be converted, in particular reduced, and the converted voltage can be provided at the second output 48.

[0052] Here, a first negative connection point 56 of the first energy storage block 6 is connected directly to the first input 52. A second, positive connection point 58 of the first energy storage block 6 can be connected to the first input 52 by means of the first main contactor 14 and / or by means of a pre-charging circuit connected in parallel to the first main contactor, comprising a first pre-charging contactor 60 and a first pre-charging resistor 62 connected in series with the first main contactor. In summary, the first main contactor for disconnecting the traction battery from the rest of the high-voltage on-board network 2a, and a first pre-charging contactor 60 connected in parallel to the first main contactor 14 and the first pre-charging resistor 62 are connected between the first energy storage block 6, in particular between its first connection point 58, and the first input 52.

[0053] Advantageously, single-pole disconnection is achieved here, so that additional protective measures such as a fuse can be omitted and / or safety requirements are not inherited from the traction battery 4. This results in a comparatively cost-effective design of the on-board electrical system 2.

[0054] A first, positive connection point 64 of the second energy storage block 8 is connected directly to the second input 54. A second, negative connection point 66 of the second energy storage block 8 can be connected to the second input 54 via the second main contactor 16 and / or via a pre-charging circuit connected in parallel to the second main contactor 14, comprising a second pre-charging contactor 68 and a second pre-charging resistor 70 connected in series with the second main contactor 14. In summary, the second main contactor for disconnecting the traction battery 4 from the rest of the high-voltage on-board network 2a, a second pre-charging contactor 68 connected in parallel to the second main contactor 16, and the second pre-charging resistor 70 are connected between the second energy storage block 8, in particular between its second connection point 66, and the second input 54.

[0055] The second DC-DC converter unit 40 comprises a (third) input 72 for the first energy storage block 6 and a (fourth) input 74 for the second energy storage block 8. The second output 48 is coupled to both the third input 72 and the fourth input 74 for voltage conversion or power transmission purposes. Thus, using the second DC-DC converter unit 40, both the voltage provided by the first energy storage block 6 and the voltage provided by the second energy storage block 8 can be converted, in particular reduced, and the converted voltage can be provided at the second output 48.

[0056] Here, the first negative connection point 56 of the first energy storage block 6 is connected directly to the third input 72. The second, positive connection point 58 of the first energy storage block 6 can be connected to the third input 72 in an analogous manner using the first main contactor 14 and / or using the (first) precharging circuit connected in parallel to the first main contactor 14 with the first precharging contactor 60 and the first precharging resistor 62.

[0057] The first, positive connection point 64 of the second energy storage block 8 is connected directly to the fourth input 74. The second, negative connection point 66 of the second energy storage block 8 can be connected to the second input 74 via the second main contactor 16 and / or via the (second) precharging circuit connected in parallel to the second main contactor 16, which includes the second precharging contactor 68 and the second precharging resistor 70.

[0058] The first DC-DC converter unit 38 can be precharged using the first precharge circuit. The second DC-DC converter unit 40 can be precharged using the second precharge circuit. This prevents damage, particularly to the respective DC-DC converter unit 38 or 40, during commissioning due to a comparatively large (inrush) current.

[0059] In summary, the DC-DC converter device 36 is supplied with both the voltage of the first energy storage block 6 and the voltage of the second energy storage block 8 on the input side, i.e., the high-voltage side. The DC-DC converter device 36 converts the voltage of the first energy storage block 6 and / or the voltage of the second energy storage block 8 and provides the converted voltage, i.e., the low-voltage voltage, at the first output 42 and, redundantly thereto, at the second output 48 for the safety-relevant low-voltage consumer 46.

[0060] The low-voltage electrical system 2b does not have a battery, in particular a starter battery. In other words, the low-voltage electrical system 2b is battery-free. Due to the redundant supply of the low-voltage consumer 46 via the DC-DC converter device 36, such a battery is not necessary.

[0061] Optionally, a capacitor 76, in particular a supercapacitor, is connected to the first terminal 44 and / or a further capacitor 78 is connected to the second terminal 50. The respective capacitor 76 or 78 serves as an intermediate energy store, provided that the safety-relevant low-voltage consumer 46 (or a further low-voltage consumer not shown) feeds energy into the low-voltage vehicle electrical system 2b. Furthermore, the respective capacitor 76 or 78 serves as a buffer in the event of a short circuit in one of the energy storage blocks 6, 8 - in particular for the period until the affected battery cells 10 have recovered, or the respective energy storage block 6 or 8 is switched off - provided that the affected energy storage block 6 or 8 cannot be switched off sufficiently quickly. In contrast to a battery, in particular a starter battery, in which an (electro-)chemical storage of energy takes place, in the (super)capacitor 76 or78 provides electrostatic energy storage. This results in the capacitor 76 or 78 being able to hold and / or buffer comparatively high voltages.

[0062] The vehicle electrical system 2 further comprises a third DC-DC converter unit 80, to whose (fifth) input 82 the traction battery 4 is connected. The second connection point 58 of the first energy storage block 6 and the second connection point 66 of the second energy storage block 8 are connected, in particular directly, to the fifth input 82.

[0063] The third DC-DC converter unit 80 comprises a (third) output 84 and a further (fourth) output 86. The third output 84 is connected to the positive connection point 44a of the first connection 44 and to the positive connection point 50a of the second connection 50. The fourth output 86 is connected to the negative connection point 44b of the first connection 44 and to the negative connection point 50b of the second connection 50. The third DC-DC converter unit 80 serves, in particular, solely to provide a quiescent current for the low-voltage consumer(s) 46. This third DC-DC converter unit 80 is therefore expediently only active when the vehicle is inactive. In particular, no safety requirements apply. Consequently, one iron core, in particular a common iron core for the two outputs 84, 86, and the galvanically connected outputs 84, 86 can serve the two (low-voltage) connections.

[0064] According to a variant not shown in detail, the third output 84 is electrically connected to the first terminal 44, and the fourth output 86 is electrically connected to the second terminal 50. The third DC-DC converter unit 80 is thus designed, in particular, as a multi-output DC-DC converter. Its input 82 is coupled to both outputs 84, 86 for voltage conversion and / or power transmission.

[0065] The third DC-DC converter unit 80 serves to provide a quiescent current for the low-voltage consumer(s) 46. For this purpose, the maximum output power of the third DC-DC converter unit 80 is smaller, for example by a factor of 10 to 50, than that of the first DC-DC converter unit 38 and / or the second DC-DC converter unit 40.

[0066] In the Fig. 2 shows a second, alternative design of the on-board network 2. With the exception of what is shown below, the statements regarding the on-board network 2 apply according to Fig. 1 in an analogous manner.

[0067] In this second embodiment of the vehicle electrical system 2, the second, positive connection point 58 of the first energy storage block 6 is directly connected to the first input 52 and to the third input 72. Furthermore, the second, negative connection point 66 of the second energy storage block 8 is directly connected to the second input 54 and to the fourth input 74.

[0068] In summary, the first energy storage block 6 is directly connected to the first and third inputs 52 and 72, thus the first main contactor 14 and the first precharging circuit are not connected between the first energy storage block 6 and these inputs 52, 72. Likewise, the second energy storage block 8 is directly connected to the second and fourth inputs 54 and 74, thus the second main contactor 16 and the second precharging circuit are not connected between the second energy storage block 8 and these inputs 54, 74.

[0069] This type of connection is particularly suitable for a DC-DC converter device 36 or for a first DC-DC converter unit 38 and a second DC-DC converter unit 40, the capacitances of which are comparatively small or can even be switched off, so that a (switch-on) current is avoided or is only small.

[0070] In summary, the design of the on-board network 2 according to the Fig. 2 a probability of failure of the safety-relevant consumer 46 is advantageously comparatively low.

[0071] In the Fig. 3 shows a second, alternative design of the on-board network 2. With the exception of the one shown below, the statements regarding the on-board network 2 apply according to Fig. 2 in an analogous manner.

[0072] The DC-DC converter device 36 is designed here as a multi-input / multi-output DC-DC converter. This therefore comprises the two outputs 42 and 48 as well as the first input 52 for the first energy storage block 6 and the second input 54 for the second energy storage block 8. The first input 52 and the second input 54 are coupled to each other for voltage conversion purposes, both to the first output 42 and to the second output 48. Thus, the voltage provided by the first energy storage block 6 can be reduced using the DC-DC converter device 36, and the reduced voltage can be provided at the first output 42, the second output 48, or both outputs. In addition, the voltage provided by the second energy storage block 8 can be reduced using the DC-DC converter device 36, and the reduced voltage can be provided at the first output 42, the second output 48, or both outputs 42, 48.

[0073] According to the not further illustrated configurations of the on-board network 2 according to the Fig. 1 to 3, the traction battery 4 has more than two energy storage blocks, for example, four or six energy storage blocks. The energy storage blocks are expediently connected in series. When the DC-DC converter device 36 is configured as a multi-input / multi-output DC-DC converter, it expediently comprises an input for each of the energy storage blocks, wherein the inputs are coupled to both the first and second outputs 42, 48 for voltage conversion purposes.In the embodiment of the DC-DC converter device 36 with the two DC-DC converter units 38, 40 designed as multi-input DC-DC converters, each of the DC-DC converter units 38, 40 preferably has an input for each of the energy storage blocks, wherein the output 42 of the first DC-DC converter unit 38 is preferably coupled to all of its inputs for voltage conversion purposes, and wherein the output 48 of the second DC-DC converter unit 40 is preferably coupled to all of its inputs for voltage conversion purposes. In all of these embodiments (not shown in further detail), a switch 18, 20, 22, in particular a relay or a circuit breaker, is preferably connected between the energy storage blocks to separate the energy storage blocks in the event of a short circuit.

[0074] In a manner not shown in detail, an electrically powered motor vehicle comprises the on-board network according to one of the Fig. 1 to 3. List of reference symbols 2 On-board network 2a High-voltage electrical system 2b Low-voltage network 4 Traction battery 6 first energy storage block 8 second energy storage block 10 battery cells 12a,b Battery connection 14 first main contactor 16 second main contactor 18 first switch 20 second switch 22 third switch 24 high-voltage consumers 26 Charging device 32 fuse 34 Security 36 DC-DC converter device 38 first DC-DC converter unit 40 second DC-DC converter unit 42 Output of the first DC-DC converter unit 44 first connection for the low-voltage consumer 44a positive connection point of the first terminal 44b negative terminal of the first terminal 46 low-voltage consumers 48 Output of the second DC-DC converter unit 50 second connection for the low-voltage consumer 50a positive connection point of the second terminal 50b negative terminal of the second terminal 52 Input of the first DC-DC converter unit 54 Input of the first DC-DC converter unit 56 Connection point of the first energy storage block 58 Connection point of the first energy storage block 60 first pre-charging contactor 62 first precharge resistor 64 Connection point of the second energy storage block 66 Connection point of the second energy storage block 68 second pre-charging contactor 70 second precharge resistor 72 Input of the second DC-DC converter unit 74 Input of the second DC-DC converter unit 76 Capacitor 78 Capacitor 80 third DC-DC converter unit 82 Input of the third DC-DC converter unit 84 Output of the third DC-DC converter unit 86 Output of the third DC-DC converter unit

Claims

[1] On-board network (2) for an electrically powered motor vehicle, comprising - a high-voltage vehicle electrical system (2a) with a traction battery (4) which has at least a first energy storage block (6) and a second energy storage block (8), - a DC-DC converter device (36) which has a first output (42) for providing a low-voltage voltage for a, in particular safety-relevant, low-voltage consumer (46) of a low-voltage network (2b) and a second output (48) for providing a low-voltage voltage for the low-voltage consumer (46), and which comprises at least one input (52, 72) for supplying the voltage of the first energy storage block (6) and at least one input (54, 74) for supplying the voltage of the second energy storage block (8), - wherein the first output (42) and the second output (48) are each coupled to one of the inputs (52, 72) for the first energy storage block (6) and to one of the inputs (54, 74) for the second energy storage block (8). [2] On-board network (2) according to claim 1, characterized by , - that the DC-DC converter device (36) comprises a first DC-DC converter unit (38) with the first output (42), with a first input (52) to which the first energy storage block (6) is connected, and with a second input (54) to which the second energy storage block (8) is connected, and - that the DC-DC converter device (36) comprises a second DC-DC converter unit (40) with the second output (48), with a third input (72) to which the first energy storage block (6) is connected, and with a fourth input (74) to which the second energy storage block (8) is connected. [3] On-board network (2) according to claim 1 or 2, characterized by that the low-voltage network (2b) is battery-free. [4] On-board network (2) according to one of claims 1 to 3, characterized by that the first output (42) is connected to a first terminal (44) for the low-voltage consumer (46), and that the second output (48) is connected to a second terminal (50) for the low-voltage consumer (46) that is separate from the first terminal. [5] On-board network (2) according to one of claims 1 to 4, characterized by , - that between the first energy storage block (6) and the or each input (52, 72) for the first energy storage block (6) a first main contactor (14) for disconnecting the traction battery (4) from the high-voltage vehicle electrical system (2a) and / or a first pre-charging contactor (60) connected in parallel to the first main contactor (14) and a first pre-charging resistor (62) is connected, and / or - that a second main contactor (16) and / or a second pre-charging contactor (68) connected in parallel to the second main contactor (16) and a second pre-charging resistor (70) are connected between the second energy storage block (8) and the or each input (54, 74) for the second energy storage block (8). [6] On-board network (2) according to one of claims 4 or 5, characterized by a third DC-DC converter unit (80), to whose input (82) the traction battery (4) is connected, wherein the third DC-DC converter unit (80) has a third output (84) and a fourth output (86), wherein the third output (84) is connected to the first terminal (44) and the fourth output (86) is connected to the second terminal (50). [7] On-board network (2) according to claim 6, characterized bythat the maximum output power of the third DC-DC converter unit (80) is smaller, in particular by a factor of 10 to 50, than that of the DC-DC converter device (36), in particular of the first DC-DC converter unit (38) and / or the second DC-DC converter unit (40). [8] On-board network (2) according to one of claims 1 to 7, characterized by that the first energy storage block (6) and the second energy storage block (8) are electrically separable from one another. [9] Motor vehicle with an on-board network (2) according to one of claims 1 to 8.

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