Device and method for supplying power to an on-board electrical system of a motor vehicle

Abstract

The invention proposes a device and a method for supplying power to an on-board electrical system of a motor vehicle, comprising at least one conductive connection (16) between at least two on-board electrical subsystems (20, 24) with a voltage level (U1, U2), wherein at least one connector (27) is provided, via which at least one energy store (70) can be connected to the conductive connection (16), wherein at least two converters (6, 7) are provided, at least one of the converters (6) being connected to the conductive connection (16), the other converter (7) being connected to the connector (27) for the energy store (70), and wherein both converters (6, 7) are connected to a terminal (56) designed to supply power to at least one load with a lower voltage level (Ul) which is lower than the voltage level (U1, U2) of the on-board electrical subsystems (20, 24).

Description

[0001] R. 418487

[0002] - 1 -

[0003] Description

[0004] Device and method for supplying a vehicle electrical system

[0005] The invention relates to a device and a method for supplying an on-board network of a motor vehicle according to the preamble of the independent claims.

[0006] State of the art

[0007] From EP 3137342 B1, a device for supplying power to at least one consumer is known. A multifunction module includes two switching devices connected in series. A connection for a DC-DC converter is provided between the two switching devices, and an energy storage device can be connected to the other connection of this converter.

[0008] The invention is based on the objective of providing a device and a method with which different operating conditions can be reliably covered. This objective is achieved by a device and a method according to the features of the independent claims.

[0009] Disclosure of the invention

[0010] The device and method according to the features of the independent claims enable the coverage of different operating modes. Specifically, by providing two suitably connected converters, these can be used equally well in both normal and special operation. This reduces the number of components used exclusively for infrequent operating modes. In particular, a separate pre-charging circuit or an additional connecting converter, especially for the initial charging of an energy storage device, can be dispensed with. Furthermore, the proposed solution allows the connection of an energy storage device with a variable voltage level, especially in the case of supercapacitors, without additional effort. Pre-charging of the R. 418487

[0011] - 2 -

[0012] The energy storage system can be discharged upon delivery without additional components. Similarly, discharging the energy storage system is also possible, particularly during decommissioning or scrapping.

[0013] In a suitable further development, at least one switching device is arranged between the connection for the energy storage device and the conductive connection and / or between the converter connected to the connection for the energy storage device and the conductive connection. This eliminates the need for a separate switch, for example, one integrated into the energy storage module itself, thus further reducing the susceptibility to faults in the arrangement. This is particularly important in applications characterized by high availability.

[0014] In a suitable further development, at least one input is provided for connecting an external source with a source voltage, wherein the input is connected to at least one of the converters, in particular to the converter that is connected to the conductive link. This allows for flexible supply of the vehicle electrical system from an external source. A high-performance supply of the vehicle electrical system from a voltage source with limited power is also possible, for example, for vehicle production, during workshop visits, or during vehicle presentations.

[0015] In a suitable further development, at least one switching device for controlling the input is arranged between the input for connecting an external source and the conductive connection and / or between the input for connecting an external source and the converter connected to the conductive connection. This allows for safe and reliable switching of the external source to and from the vehicle.

[0016] In a suitable further development, the converters are controlled in normal operation such that both converters transform the voltage level of the sub-networks into the lower voltage level at the terminal to supply at least one consumer. This allows for an even distribution of the converters' power as well as a redundant supply to the terminal. R. 418487

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[0018] In a suitable advanced configuration, the source voltage supplied via the input is converted by the two converters and fed to the energy storage device in a special operating mode for charging the energy storage system. The converters also used for normal operation serve for commissioning and, in particular, for the initial charging of the energy storage device.

[0019] In a suitable further development, in a special operation for charging the energy storage device, the converter connected to the input for the external source is initially operated in buck mode, and the converter connected to the connection for the energy storage device is operated in boost mode, wherein the converter connected to the input, preferably in constant current mode, changes its output voltage to the lower voltage level. This allows the empty energy storage device to be brought to a higher voltage level in a first step.

[0020] In a suitable further development, it is provided in a further step that the converter connected to the input is / are operated in a voltage control mode, in particular to achieve a constant output voltage at the level of the lower voltage level, and / or the converter connected to the energy storage device is / are operated in a boost mode, in particular to increase the voltage at the connection for the energy storage device from the lower voltage level to the voltage level of the sub-networks.

[0021] This allows the energy storage device to be charged further. At the same time, at least one consumer could already be supplied with the lower voltage level.

[0022] In a suitable further development, it is provided that, in a special operation for charging the energy storage device, the energy storage device is connected to at least one of the sub-networks upon reaching a certain output voltage, in particular by closing at least one switching module and / or at least one circuit breaker. This allows the on-board network to be put into operation. In the event of a power supply failure at the input, the on-board network can be supported by the at least partially charged energy storage device and, if necessary, shut down in a controlled manner. R. 418487

[0023] - 4 -

[0024] In a suitable further development, when at least one voltage limit is reached at the connection for the energy storage device, at least one of the converters is connected to at least one of the sub-networks. This ensures normal operation after the energy storage device has started up or been charged.

[0025] In a suitable further development, to stabilize the voltage of at least one of the sub-networks, the two converters are controlled in such a way that the voltage at the connection for the energy storage device is converted to the lower voltage level and then to the voltage level of the sub-networks. This allows short-term power dips to be buffered. Premature degradation of the consumers or the shutdown of consumers can be avoided.

[0026] In a suitable further development, at least one or more switching modules are provided for coupling and isolating the two sub-networks. A fault in one of the sub-networks does not affect the other sub-network. Furthermore, the power supply to a particularly safety-relevant load can be reliably maintained via the conductive connection. By providing multiple switching modules, reliable isolation or coupling of the sub-networks can be achieved even if one of the switching modules fails. It is particularly advantageous to provide at least one load break switch, via which at least one preferably safety-relevant load can be connected to the conductive connection. This load can then be supplied from both sub-networks, further increasing the availability of the power supply. By providing additional switching devices or...Circuit breakers can protect the components of the vehicle electrical system from overcurrents or overvoltages, etc., in the event of a fault.

[0027] In a suitable further development, at least one supply circuit is required to supply the control for at least one switching module and / or at least one protective switch and / or at least one switching device and / or at least one load break switch and / or at least one protective switch and / or at least one converter and / or at least one control unit, R. 418487

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[0029] In particular, microcontrollers are intended for their control, and the power supply circuit can be connected to the input and / or to the energy storage device, especially via a protection circuit. This ensures the power supply to the power supply circuit, particularly during commissioning of the energy storage device and in special operating conditions.

[0030] Furthermore, a method for the safe supply of an on-board network of a motor vehicle according to the features of the independent claim is also shown with the advantages already mentioned.

[0031] Further appropriate development results from the dependent claims, the figures presented, and their description.

[0032] Brief description of the drawing

[0033] They show

[0034] Figure 1 shows a topology with an integrated energy distribution module.

[0035] Figure 2 shows the device according to Figure 1 in normal operation,

[0036] Figure 3 shows the device according to Figure 1 in a special operation, in particular during the manufacture of a motor vehicle or the commissioning of an energy storage device in a first step,

[0037] Figure 4 shows the device according to Figure 3 in the special operation according to a second step,

[0038] Figure 5 shows the device according to Figure 3 in the special operation according to a third step,

[0039] Figure 6 shows the device according to Figure 1 in a further special operation, in particular during commissioning via a low-voltage source as well as R. 418487

[0040] - 6 -

[0041] Figure 7 shows the device according to Figure 1 in a further special operation, in particular a voltage support from the energy storage device.

[0042] embodiment of the invention

[0043] Figure 1 shows a vehicle topology with a highly available electrical system comprising at least two sub-systems 20 and 24. One sub-system 20 operates at a voltage level U1, for example, 48 V, while the other sub-system 24 operates at a different voltage level U2, also for example, 48 V. Sub-system 20 can be coupled via a DC / DC converter 2 to another sub-system, for example, a high-voltage electrical system with an associated energy storage device. The other sub-system 24 can be coupled via a further DC / DC converter 4 to yet another sub-system, for example, a high-voltage electrical system with an associated energy storage device, such as that of an electric vehicle. Consumers 31 and 32, which are supplied with energy via the respective sub-systems 20 and 24, are shown as examples.

[0044] The two sub-systems 20, 24 are connected to each other via at least one power distribution module 10. For this purpose, the power distribution module 10 has at least one connection 21 for the first sub-system 20 and at least one further connection 25 for the second sub-system 24. The two sub-systems 20, 24 are connected to each other via a conductive connection 16. In the embodiment according to Figure 1, the electrically conductive connection 16 between the two sub-systems 20, 24 can be interrupted via at least one switching module 12, particularly in the event of a fault.

[0045] In the exemplary embodiment, a further switching module 14 is provided for the possible interruption or coupling of the two sub-networks 20, 24. The two switching modules 12, 14 are coupled to each other via a conductive connection 16, while the other output of each switching module 12, 14 is connected to the respective terminals 21, 25 for the respective sub-networks 20, 24. One switching module 12 is arranged between the terminal 21 for the sub-network 20 and the conductive connection 16. The further switching module 14 is R. 418487

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[0047] The switching modules are arranged between the additional connection 25 for the additional sub-network 24 and the conductive connection 16. Alternatively, both switching modules 12 and 14, or only one switching module 12 or 14, could be omitted. However, a redundant design of the switching modules 12 and 14, each connected in series, ensures reliable isolation of the two sub-networks 20 and 24 in the event of a fault in at least one of the switching modules 12 and 14. The switching modules 12 and 14 can, in turn, consist of several switching elements to minimize failures. However, this is not mandatory. The switching modules 12 and 14 can, for example, be designed as MOSFETs or similar devices.

[0048] In the embodiment shown in Figure 1, the power supply module 10 comprises at least one connection 27 for at least one energy storage device 70. The energy storage device 70 can be part of an energy storage module 8, which includes further components. The voltage Ile of the energy storage device 70 is applied to the connection 27. In this embodiment, the energy storage module 8 includes at least one sensing device 72, which is connected in series between the energy storage device 70 and the connection 27. The sensing device 72 can, for example, be a resistor. The two potentials of the resistor can be tapped via an instrumentation amplifier 74, the output of which is, for example, supplied to an energy storage management system 76. Alternatively, the potentials at the two connections of the energy storage device 70, or its voltage level Ile, can also be supplied to the energy storage management system 76 for voltage tapping.The energy storage management system 76 serves to monitor, and optionally also to determine, further parameters of the energy storage system 70, such as the state of charge (SOC), state of health (SOH), or similar parameters. The energy storage module 8 can, via a computing device 78, for example a microcontroller, transmit or receive the data or control parameters of the energy storage system 70, as recorded or determined by the energy storage management system 76, to other control units and evaluation devices via a bus system 80. The energy storage system 70 is preferably a power storage device that provides electrical energy for short periods to cover certain power peaks. This can, for example, be at least one capacitor, in particular a capacitor. 418487.

[0049] - 8 -

[0050] so-called DLC (double layer capacitor), buffer capacitor (so-called powercap) or other suitable electrical storage devices.

[0051] A switching device 17 is arranged between the terminal 27 for the energy storage module 8 and the conductive connection 16. The terminal 27 for the energy storage module 8 is connected to both the switching device 17 and a converter 7, optionally via a switching device 41, in particular a circuit breaker (for example, a residual current circuit breaker, for example implemented as a SmartFET) as provided in Figure 1.

[0052] In the embodiment shown in Figure 1, the energy distribution module 10 comprises an input 44, particularly for an external energy source. An external energy source, such as a charging station, with a voltage level or source voltage Lid can be connected via the input 44. The input 44 can be connected to the electrically conductive connection 16 via at least one switching device 40, 58, 60. In the embodiment shown, two switching devices 58, 60 are arranged between the input 44 and the electrically conductive connection 16. A circuit breaker 40 can optionally be arranged between the two switching devices 58, 60 and the electrically conductive connection 16.This circuit breaker 40 can be designed as a fail-safe circuit breaker, for example in the form of a so-called smartFET, which, at the 48 V voltage level U1, U2, is characterized by a lower current-carrying capacity than in a conventional 12 V vehicle electrical system. The input 44 is also connected to a current transformer 6. The connection to the current transformer 6 is made between the circuit breaker 40 and the other switching device 60.

[0053] Furthermore, the voltage level or source voltage Lid at input 44 can be supplied via a protection circuit 46 to a power supply circuit 48, which supplies, for example, logic components or control circuits, etc., of the switching modules 12, 14 or further switching devices 17, 18, 40, 41, 58, 60, 62 or the converters 6, 7, control devices such as microcontrollers or similar, etc., with electrical energy. A diode 50 is arranged between the protection circuit 46 and the power supply circuit 48 by way of example. R. 418487

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[0055] Protection circuit 46 is preferably supplied redundantly to achieve high availability. The potential of terminal 21 is fed to the logic supply 48 via a diode 51. The potential of the other terminal 25 is also fed to the power supply circuit 48 via another diode 52. Furthermore, the potential of terminal 27 for the energy storage device 8 is fed to the power supply circuit 48 via another diode 53. Thus, the power supply circuit 48 can be supplied with energy via the sub-system 20, the other sub-system 24, terminal 27 of the energy storage device 70, or input 44. This increases the availability of the power supply circuit 48.

[0056] Furthermore, the energy distribution module 10 comprises at least one terminal 56. An electrical load (not shown) can be supplied with a lower voltage level III via terminal 56. This lower voltage level III is preferably a voltage level lower than the voltage levels U1 and U2 of the two sub-networks 20 and 24. Particularly preferably, it is a lower voltage level III of 12 V. Terminal 56 is optionally electrically connected to both the first converter 6 and the second converter 7 via at least one switch 62.

[0057] Furthermore, the power distribution module 10 includes unspecified terminals for supplying additional consumers 33, in particular safety-related consumers such as brakes, steering, or similar components, which are supplied from both sub-networks 20, 24. The safety-related consumer(s) 33 can therefore be electrically connected to the conductive connection 16. The respective consumers 33 can be controlled via corresponding load break switches 18. The load break switches 18 can be components of the power distribution module 10. The safety-related consumers 33 are preferably connected to the conductive connection 16 between the two switching modules 12, 14, so that a disconnection of at least one of the sub-networks 20, 24, which is faulty, does not impair the supply to the preferably safety-related consumer 33.The load break switch 18 can switch individual consumers 33 or individual groups of consumers on or off. R. 418487.

[0058] - 10 -

[0059] The converters 6, 7 are preferably bidirectional converters, preferably DC-DC converters. The converters 6, 7 may optionally be multi-phase. The direction can be selected separately for each of the converters 6, 7. For example, the converter 6, 7 can be configured as a two-phase bidirectional buck converter and / or boost converter. For the converters 6, 7, the target voltage and / or the target current and / or the direction of the voltage conversion, the activation of the converters 6, 7, or similar parameters can be specified. The converters 6, 7 can thus be operated in voltage-regulated mode or in current-regulated mode, essentially as a constant current source.

[0060] The two converters 6, 7 are essentially connected in parallel. At least one terminal of one converter 6 and one terminal of the other converter 7 are connected together and, according to the embodiment shown in Figure 1, supply terminal 56 with the lower voltage level III. The other terminal of converter 6 is connected – optionally via a switch 40 – to the conductive connection 16. The other terminal of converter 7 is also connected – optionally via further switching devices 41, 17 – to the conductive connection 16. The other terminal of converter 6 can be connected to input 44. The other terminal of converter 7 can be connected to terminal 27 for the energy storage device 70. This connection, along with the provision of two converters 6, 7, increases the flexibility of the arrangement for different operating modes. At the same time, the converters 6, 7 are also used in normal operation.

[0061] In Figure 2, the current flows indicated by thicker arrows occur during normal operation. During normal operation, the two switching modules 12 and 14 are closed. The sub-networks 20 and 24 with identical voltage levels U1 and U2 are not isolated from each other, as both sub-networks 20 and 24 are functioning correctly. The load break switch 18 is closed to supply the load 33. The switching device 17 for establishing the connection between the conductive connection 16 and the converter 7 is closed. The switch 41, the optional circuit breaker, is closed. The switch 40, the optional circuit breaker 40, is closed. The two switching devices 58 and 60 control the input 44R. 418487

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[0063] are open, as no external charging occurs via input 44. At least one of the switching devices 58, 60 should be open. The switch 62 for controlling the load connected to terminal 56 is closed. In normal operation, the two converters 6, 7 are used in buck converter mode to provide the total current of the converters 6, 7 at terminal 56 for corresponding loads that are supplied with the lower voltage level III. The two converters 6, 7 convert the current flowing from the two sub-networks 20, 24 from a voltage level U1 or U2, in particular 48 V, to the lower voltage level III, preferably 12 V. Due to the low currents on the higher 48 V side of the on-board network 20, 24 compared to the low-voltage network (12 V), losses through the circuit breakers 40, 41 are low. Preferably, both converters 6,7 are driven with a phase shift (for example, by 180° phase shift).On the U1, U2 side of the converters 6,7, AC-side coupling can be implemented to optimize EMC behavior. Depending on the voltage level Ile of the energy storage device 70, it can be charged.

[0064] Figures 3-5 show the various steps 1-3 in the manufacture of the motor vehicle and in the commissioning of the energy storage device 70. In the manufacture of the vehicle and in the commissioning of the energy storage device 70, an empty energy storage device 70 and a power source connected to input 44 are assumed. The supply circuit 48 is powered from this source via the overvoltage protection circuit 46. A microcontroller, which is not shown separately, is also powered in this way as a possible control unit. In a first step according to Figure 3, the two switching modules 12 and 14 are open, and the two switching devices 58 and 60, as well as the additional protective switch 41, are closed. The switching device 17 for the energy storage device 70 and the switch 62 for controlling terminal 56 are open. The control unit can now control the converter 6 in buck-shift mode and the additional converter 7 in boost-shift mode.In principle, this allows the energy storage device 70 to be charged via the two converters 6 and 7 by the source connected to input 44 with the voltage level or source voltage Lid, for example 48 V. Since the voltage Ile at the storage device 70 is initially around 0 V, the converter 6 increases the output voltage in constant current operation from 0 V to its target voltage, the lower voltage level III, for example R. 418487.

[0065] - 12 -

[0066] 12 V. The further converter 7 passes the output voltage of the converter 6 unchanged to the energy storage device 70 for charging.

[0067] Figure 4 shows the next step, in which the energy storage device 70 is charged from the lower voltage level III (12 V) to a higher voltage (e.g., greater than 24 V). Once the energy storage device 70 has been charged to the lower voltage level III (12 V), the converter 6 operates in voltage regulation mode. The converter 6 converts the input voltage, or the source voltage Lid, into the desired constant lower output voltage III. The other converter 7 operates in boost mode to further charge the energy storage device 70. If required, loads can already be connected to terminal 56 and supplied by the lower voltage level III. For this purpose, the switch 62 is closed to control terminal 56.

[0068] Figure 5 shows the third step, in which the two sub-networks 20 and 24 are connected and, if necessary, supported by the energy storage device 8. If the voltage Ile at the energy storage device 70 exceeds a lower operating voltage limit llg of the sub-networks 20 and 24, the system 20 and 24 can be put into operation by closing or gradually closing the switching modules 12 and 14, or by closing the load break switch(es) 18 to supply the consumers 33. In the event of a sudden failure of the source at input 44, the system 20 and 24 can be supported by the at least partially charged energy storage device 70 and shut down in a controlled manner. Switches 40 and 17 typically have an inverse diode. This allows current to flow into the conductive connection 16 even when the switch is open. To avoid higher losses, the switch 17, 40 is closed by the PC or by a hardware circuit in the event of current flowing through the diode.With proper operation, the switches could be returned to normal operation as shown in Figure 2.

[0069] Figure 6 shows the possibility of supplying input 44 with a source with a lower voltage level, for example with Ud of 12 V, to start up the energy storage device 70. The steps shown above can also be carried out with power limitations from a source with a lower RV. 418487

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[0071] Voltage level lid possible. This might be necessary, for example, for emergency access, or to establish charging capability from an external 12 V source such as another vehicle or a USB-C PD source. In this case, the additional converter 7 remains permanently in boost mode and attempts to stabilize the voltage Ile at the energy storage device 70 to the desired voltage level U1, U2 of the sub-networks 20, 24, in particular 48 V. Here, the switching device 17, as well as the two switching devices 58, 60, and the switching device 41, are closed. The supply circuit 48 is supplied via the additional converter 7.

[0072] Figure 7 shows the special operating mode in which the energy storage device 70 supports or boosts the on-board voltage in U1, U2 of the sub-on-board networks 20, 24. Short power dips at input 44 (which is supplied by a voltage source with a lower voltage level, Ul, in particular 12 V) can be buffered by the energy storage device 70. The energy management system can react to a general power limitation at input 44 by degrading the loads. This means that non-safety-related loads 31, 32 can have their power consumption reduced or be switched off completely.

[0073] An overload at input 44 (for example, operation beyond the power adjustment range) can be prevented by reducing the setpoint current limit of the additional converter 7. Depending on the operating condition, such as an emergency opening of the vehicle, the energy storage device 70 does not need to be charged to the full voltage Ue (for example, U1, U2 of 48 V), but only to a voltage level or charging level required for the application. In this case, after reaching the required charging level, the system can switch to the mode or special operation "U1, U2 or 48 V boosting from the energy storage device 70". Here, the voltage Ue at the energy storage device 70 is converted to the voltage level U1, U2 or 48 V in reverse operation of the two converters 6, 7.

[0074] The flexible interconnection of the two converters 6, 7 allows many applications to be covered by switching between the above configurations. The special case "U1, U2 or 48 V boosting from the energy storage 70"R. 418487

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[0076] The special "Workshop Mode" can be used to discharge the energy storage unit 70 (for example, before replacement or scrapping). After an accident and as part of a risk reduction maneuver, this special mode can be used to draw the maximum energy from the energy storage unit 70 at a lower power output (for example, for emergency functions such as hazard warning lights, eCall, etc.). The special "Connecting the sub-networks 20, 24 and supports from the energy storage unit 70" special mode can also be used for vehicle presentations or in workshops, particularly during vehicle production, to cover the average power demand with a limited external source (lower voltage range Ud=UI, for example, only 12 V or a power-limited source of voltage U1, U2) and to buffer all dynamic processes with the energy storage unit 70. A particular advantage is that in the event of a failure orDisconnecting the external source at input 44 provides sufficient energy for a controlled shutdown or pause of the vehicle electrical system. Furthermore, it is particularly advantageous that the charging processes of the energy storage unit 70, with its flexible voltage level, can be carried out by converters 6, 7 that are otherwise required during normal operation without significant additional effort. Because the energy storage unit 70 is delivered empty, it is possible to operate it without an internal disconnect switch (within the energy storage module 8). The coupling switch 17 for the energy storage unit 70, along with other high-availability switches, is located within the energy distribution module 10. Eliminating the disconnect switch for the energy storage unit 70 within the energy storage module 8 removes a significant potential source of error that would otherwise compromise the safety objective of a reliable power supply.

[0077] Another function of the power distribution module 10 is the supply of power to safety-relevant consumers 33. For example, the power distribution module 10 can supply safety-relevant consumers 33 such as the brakes and steering. A central vehicle computer and, for example, ADAS sensors (sensors for driver assistance functions) can also be connected to the power distribution module 10. Other consumers at this primary level can include wipers and lights. By connecting to the power distribution module 10, these safety-relevant consumers 33, which have redundancy requirements, are supplied in such a way that a single fault does not lead to a complete failure. R.418487

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[0079] their supply can be ensured. This is guaranteed by the coupling of the two sub-networks 20, 24, so that in the event of a single fault, the supply is always provided by one of these two sub-networks 20, 24. High-performance consumers, such as fans or pumps, can also be supplied via the power distribution module 10. The safety-relevant consumers 33 can preferably be designed with functional redundancy.

Claims

R. 418487 - 16 - Claims 1. Device for supplying an on-board electrical system of a motor vehicle, comprising at least one conductive connection (16) between at least two sub-on-board electrical systems (20, 24) with a voltage level (U1, U2), wherein at least one connection (27) is provided via which at least one energy storage device (70) can be connected to the conductive connection (16), wherein at least two converters (6, 7) are provided, wherein at least one of the converters (6) is connected to the conductive connection (16), wherein the other converter (7) is connected to the connection (27) for the energy storage device (70), and wherein both converters (6, 7) are connected to a terminal (56) which is configured to supply at least one consumer with a lower voltage level (III), which is lower than the voltage level (U1, U2) of the sub-on-board electrical systems (20, 24).

2. Device according to claim 1, characterized in that at least one switching means (17) is arranged between the connection (27) for the energy storage device (70) and the conductive connection (16) and / or between the converter (7) connected to the connection (27) for the energy storage device (70) and the conductive connection (16).

3. Device according to one of the preceding claims, characterized in that at least one input (44) is provided for connecting an external source with a source voltage (Lid), wherein the input (44) is connected to at least one of the converters (6,7), in particular to the converter (6) that is connected to the conductive connection (16).

4. Device according to one of the preceding claims, characterized in that at least one switching means (58, 60) for controlling the input (44) is arranged between the input (44) for connecting an external source and the conductive connection (16) and / or between the input (44) for connecting an external source and the converter (6) that can be connected to the conductive connection (16).

5. Device according to one of the preceding claims, characterized in that the converters (6, 7) are controlled in normal operation such that R. 418487 - 17 - that both converters (6,7) convert the voltage level (U1, U2) of the sub-networks (20,24) into the lower voltage level (III) at terminal (56) to supply at least one consumer.

6. Device according to one of the preceding claims, characterized in that in a special operation for charging the energy storage device (70) the source voltage (Lid) supplied via the input (44) is converted via the two converters (6,7) and supplied to the energy storage device (8).

7. Device according to one of the preceding claims, characterized in that in a special operation for charging the energy storage device (70) the converter (6) connected to the input (44) is initially operated in a buck-shift operation and the converter (7) connected to the terminal (27) is operated in a boost-shift operation, wherein the converter (6) connected to the input (44), preferably in a constant current operation, changes its output voltage to the lower voltage level (III).

8. Device according to one of the preceding claims, characterized in that in a special operation for charging the energy storage device (70), the converter (6) connected to the input (44) is operated in a voltage control mode, in particular to achieve a constant output voltage at the level of the lower voltage level (III), and / or the converter (7) connected to the energy storage device (8) is operated in a boost mode, in particular to increase the voltage (Ile) at the connection (27) for the energy storage device (70) from the lower voltage level (III) to the voltage level (U1, U2) of the sub-networks (20, 24).

9. Device according to one of the preceding claims, characterized in that in a special operation for charging the energy storage device (70) in a further step upon reaching a certain output voltage (11g) of the energy storage device (70) the energy storage device (70) is connected to at least one of the sub-networks (20, 24), in particular by closing at least one switching module (12, 14) and / or at least one protective switch (40).

10. Device according to one of the preceding claims, characterized in that upon reaching at least one limit value (11g) by the R. 418487 - 18 - Voltage (lie) at the connection (27) for the energy storage (70) at least one of the converters (6,7) is connected to at least one of the subnetworks (20,24).

11. Device according to one of the preceding claims, characterized in that, for voltage support of at least one of the sub-networks (20,24), the two converters (6,7) are controlled such that the voltage (Ile) at the connection (27) for the energy storage device (70) is converted into the lower voltage level (III) and subsequently into the voltage level (U1, U2) of the sub-networks (20,24).

12. Device according to one of the preceding claims, characterized in that at least one switching module (12) is provided for coupling and disconnecting the two sub-networks (20, 24) and / or that at least one first switching module (12) and at least one second switching module (14) are provided for coupling and / or disconnecting the two sub-networks (20, 24), wherein the two switching modules (12, 14) are connected in series via the conductive connection (16), and / or that at least one load break switch (18) is provided, via which at least one, preferably safety-relevant, load (33) can be connected to the conductive connection (16), and / or that at least one switch (62) for controlling the terminal (56) is connected to the two converters (6, 7) and to the terminal (56), and / or that at least one circuit breaker (40, 41) is arranged between the conductive connection (16) and at least one of the converters (6, 7).

13. Device according to one of the preceding claims, characterized in that at least one supply circuit (48) is provided for supplying the control for at least one switching module (12, 14) and / or at least one protective switch (40, 41) and / or at least one switching device (17, 58, 60, 62) and / or at least one load break switch (18) and / or at least one converter (6, 7) and / or at least one control unit, in particular a microcontroller, for controlling them, wherein the supply circuit (48) can be connected to the input (44) and / or to the energy storage device (70), in particular via a protection circuit (46).

14. Method for supplying an on-board electrical system of a motor vehicle, comprising at least one conductive connection (16) between at least two R. 418487 - 19 - Sub-networks (20, 24) with a voltage level (U1, U2), wherein at least one connection (27) is provided via which at least one energy storage device (70) can be connected to the conductive connection (16), wherein at least two converters (6, 7) are provided, wherein at least one of the converters (6) is connected to the conductive connection (16), wherein the other converter (7) is connected to the connection (27) for the energy storage device (70), and wherein both converters (6, 7) are connected to a terminal (56), wherein both converters (6, 7) supply at least one consumer with a lower voltage level (III) which is lower than the voltage level (U1, U2) of the sub-networks (20, 24).

15. Method according to the preceding method claim, characterized in that the converters (6,7) are controlled in normal operation such that both convert the voltage level (U1, U2) of the sub-networks (20,24) into the lower voltage level (III) at terminal (56) to supply at least one consumer, and wherein in a special operation for charging the energy storage device (70) the two converters (6,7) convert the source voltage (Lid) supplied via an input (44) and thus charge the energy storage device (70).

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