Onboard electrical system of a vehicle with a DC voltage charging terminal

Abstract

The vehicle onboard power supply (FB) is equipped with a DC voltage charging terminal (DC), a non-configurable battery (AK), a galvanically isolated DC voltage converter (GW) and an electric drive (EA). The battery (AK) is connected to a first side of the DC voltage converter (GW) via a switchable connecting circuit (VS, VS'), to which the DC voltage charging terminal (DC) is connected. The battery (AK) is connected to the electric drive (EA) and the second side of the DC voltage converter (GW) via a drive switch (S3). The connecting circuit (VS, VS') has a direct connection switch (S1, S1'), which connects the battery (AK) to the first side of the DC voltage converter in a switchable manner. The DC voltage charging terminal (DC) is connected to the DC connecting switch (S1, S1') via a charging terminal switch (S2, S2') of the connecting circuit (VS, VS').

Description

Technical Field

[0001] The invention relates to a vehicle-mounted power grid. Background Art

[0002] It is known to equip a vehicle with an electric drive which is powered by a vehicle-side battery. The vehicle is equipped with a charging terminal for charging the battery. Since the electric drive and thus also the battery preferably have a high operating voltage to achieve high power, the vehicle's onboard power system has a high-voltage branch. For example, batteries with a nominal voltage of 400 V are used, these batteries being referred to as high-voltage batteries.

[0003] In addition, there are filter capacitors (also called Cy capacitors) between the high voltage potential of the battery on the one hand and the ground potential on the other hand. The filter capacitors are used to dissipate interference, for example, generated by connected components. These filter capacitors should be taken into account when considering the risk of electric shock. In the publication DE 10 2015 006 208 A1, it is described that the battery can be divided and the parts of the battery can be operated in series, wherein then, with a nominal voltage of 400 V for each part of the battery, a voltage of 800 V can be obtained at the filter capacitor.

[0004] The object is to specify a possibility with which vehicle components can be operated at high voltages in a simple manner without excessively high filter capacitances leading to dangerous electrical shocks in the event of faulty insulation. Summary of the invention

[0005] This object is achieved by means of a vehicle electrical system. Further features, embodiments, properties and advantages are apparent from the further exemplary embodiments, the description and the figures.

[0006] A vehicle electrical system is proposed, which has a DC voltage charging terminal, a non-configurable battery, a galvanically disconnected DC voltage converter and an electric drive. The non-configurable battery has cells that are connected to one another (in series) without switches. This results in a constant nominal voltage and, therefore, also due to the lack of switches, no possibility of setting different nominal voltages (configurations) of the battery by configurable arrangement of the batteries. On the other hand, no additional switches are required for battery configuration. In this case, the galvanically disconnected DC voltage converter makes it possible to separate the DC voltage charging terminal from a plurality of Cy capacitors. This results in only a low Cy capacitance for the DC voltage charging terminal (that is to say a low capacitance between the voltage potential of the battery on the one hand and the ground potential on the other hand).

[0007] It is provided that the DC voltage terminal is connected to the DC voltage converter via a first switch, and the battery is connected to the DC voltage converter via a second switch. In particular, the DC voltage charging terminal and the battery are connected to the same side of the DC voltage converter via respective switches. Each of the two switches has a first side directly connected to the DC voltage converter. The second side of the first switch is connected to the DC voltage charging terminal, and the second side of the second switch is connected to the battery. Therefore, the two switches have a first side, on which the switches are connected to each other (and also to the DC voltage converter), and a second side, which is connected only to the DC voltage charging terminal or only to the battery. The switch between the battery and the DC voltage converter is also referred to as a direct connection switch. The switch between the DC voltage charging terminal and the DC voltage converter can be referred to as a charging terminal switch or can also correspond to the isolating switch described below. A direct connection between a switch and a DC voltage converter is used to represent a connection without a switch, which is a connection without a converter or which has other converters. From the DC voltage converter, a branch can thus be obtained in two paths, wherein the first path leads to the DC voltage charging terminal via the first converter and the second path leads to the battery via the second switch. The switch described here is preferably bipolar and separates the two supply potentials when the switch is open.

[0008] A switchable connection circuit is provided, which is connected to the first side of the DC voltage converter. A DC voltage charging terminal is connected to the connection circuit. The switchable connection circuit also includes a charging terminal switch. The battery is connected to the electric drive and the second side of the DC voltage converter via a drive switch (preferably not part of the connection circuit). In particular, the first path of the drive switch leads to the electric drive, and the second path leads to the second side of the DC voltage converter. From the perspective of the drive switch, a bifurcation is thus obtained in two paths, wherein the first path leads to the electric drive and the second path leads to the second side of the DC voltage converter.

[0009] The connecting circuit has a direct connection switch, which connects the battery to a first side of the DC voltage converter in a switchable manner. The DC voltage charging terminal is connected to the direct connection switch via the charging terminal switch of the connecting circuit. This results in a first connection point, which is connected to the galvanically isolated DC voltage converter in a switchless manner. From this first connection point, a branch via the direct connection switch is derived, via which the battery is connected (to the DC voltage converter), and another branch to the DC voltage charging terminal, wherein the DC voltage charging terminal is connected to the DC voltage converter via the charging terminal switch (in a switchless manner). Connection in a switchless manner does not exclude connection to the converter; possible switching elements in the converter should not be regarded as switches mentioned here in this case.

[0010] A path is derived from the DC voltage converter (or its first side) via the charging terminal switch to the DC voltage charging terminal and via the direct connection switch to the battery. Another path leads from the battery to the DC voltage converter or its second side via the drive switch. The electric drive and, if necessary, other consumers or components of the vehicle's onboard power system are connected to the second side of the DC voltage converter. With the help of the drive switch, the battery can be galvanically isolated from the second side of the DC voltage converter, so that the battery is only galvanically connected to the DC voltage charging terminal via the direct connection switch and the charging terminal switch. In addition, although the second side of the DC voltage converter is connected to the charging terminal in a power-transmitting manner, no galvanic connection (galvanische Verbindung) occurs through this path. For this reason, the DC voltage converter on the one hand and the drive switch on the other hand separate the DC voltage charging terminal from the filter capacitor (for example, the Cy capacitor at the electric drive or other components), which is galvanically connected to the second side of the DC voltage converter.

[0011] In addition, energy can be fed in from the DC voltage charging terminal via a DC voltage converter, while the non-galvanic connection can transfer energy from the DC voltage charging terminal to the battery via a direct connection switch and a charging terminal switch. In a first variant, no other switches are provided between the galvanic-isolating DC voltage converter and the direct connection switch or the charging terminal switch, and in particular no other DC voltage converter is provided. In another variant, it is provided that a non-galvanic-isolating terminal converter (also implemented as a DC voltage converter) is provided between the galvanic-isolating DC voltage converter and the DC voltage charging terminal. The non-galvanic-isolating terminal converter is located between the switch connected downstream of the DC voltage charging terminal and the galvanic-isolating DC voltage converter (or the direct connection switch).

[0012] The charging terminal switch of the connection circuit can be connected to the side of the direct connection switch that is connected to the DC voltage converter.

[0013] It can be provided that the control device (of the vehicle's onboard power system) is connected to the switch in a controlled manner. In DC charging operation (corresponding to DC voltage charging operation), the control device is configured to control the charging terminal switch to be in a closed state, the direct connection switch to be in an open state, and the drive switch to be in a closed state. The control device is therefore constructed to control the second switch to be in a closed state and the first switch to be in an open state when DC charging operation is set. In driving operation, the control device is configured to control the charging terminal switch (corresponding to the second switch) and the direct connection switch (corresponding to the first switch) to be in an open state. In the driving operation state, the drive switch is controlled to be in a closed state. This is set by the control device. The control device is configured to be operated in driving operation and in DC charging operation.

[0014] In a variant, the charging terminal switch of the connecting circuit is connected to the side of the direct connection switch connected to the battery. This corresponds to the first side of the DC voltage converter of the current isolation. The connecting circuit can also have a terminal converter of the current connection. The terminal converter is constructed as a DC voltage converter, but in order to clearly distinguish it from the DC voltage converter of the current isolation, it is only called a terminal converter. Only its function corresponds to the function of the DC voltage converter. The DC voltage charging terminal is connected to the side of the direct connection switch connected to the DC voltage converter via the terminal converter. In this variant, there is an alternative charging terminal switch, which is arranged between the DC voltage charging terminal and the battery and is therefore connected to the side of the direct connection switch away from the DC voltage converter. In the previously shown variant, the charging terminal switch is connected to the side of the direct connection switch facing the DC voltage converter. In the variant described here, there are other connections from the DC voltage charging terminal to the terminal converter via an additional switch (the additional switch is also called an isolating switch). In this case, the terminal converter connects the isolating switch to the galvanically isolated DC voltage converter or its first side. In particular, the terminal converter connects the isolating switch, which leads to the DC voltage charging terminal, to a direct connection switch, which in turn connects the terminal converter to the battery. As a result, a DC voltage can be transferred from the DC voltage charging terminal to the battery via the terminal converter, without resulting in a non-galvanically isolated connection to the Cy capacitor of the electric drive.

[0015] In another charging mode, the charging terminal switch can be closed so that the DC voltage charging terminal is directly connected to the battery via the charging terminal switch (that is, not via the terminal converter), especially not connected to the battery via the direct connection switch. When charging, the drive switch is preferably disconnected so that on the one hand, the current isolation between the Cy capacitor of the electric drive device and the DC voltage charging terminal is obtained by the drive switch and the DC voltage converter of the current isolation. In addition, it is not necessary that the battery must be configured between different nominal voltages, but can have a fixed nominal voltage and can therefore have an unchangeable configuration. Usually, the battery can be charged from the DC voltage charging terminal via the direct connection switch (first switch) (wherein the drive switch is disconnected so as not to connect the Cy capacitor of the electric drive device to the DC voltage charging terminal). In addition, when the direct connection switch is disconnected, the battery can be charged via the DC voltage converter of the current isolation and the drive switch that is then closed. These two possibilities allow adaptation to the operating voltage of the battery that changes with the charge state of the battery. At the same time, it is possible to charge the battery via the DC voltage converter of the current isolation, especially in the case of a low charge state, without having to reconfigure the battery. Furthermore, it is possible to operate other components by means of the second side of the galvanically isolating DC voltage converter; in this case, the switch is driven so that the CY capacitor can be galvanically isolated from the DC voltage charging terminal.

[0016] In this case, the controller can be designed for (at least) two different charging modes, wherein a first charging mode is conducted via a galvanically isolating DC voltage converter and a further mode is conducted via a switch connecting the battery directly to the DC voltage charging terminals. In addition, an AC voltage charging mode can be provided.

[0017] In short, the DC voltage charging terminal is connected to the terminal converter via an isolating switch. The vehicle onboard power system is designed to set the isolating switch in a closed state only in the DC charging mode. If there are multiple DC charging modes, the isolating switch can be closed in one of the charging modes and closed or open in another DC charging mode.

[0018] The galvanic isolation DC voltage converter is preferably set up to convert the first high voltage into the second high voltage. The high voltage applied on the second side of the galvanic isolation DC voltage converter is preferably higher than the other high voltage. In particular, the galvanic isolation DC voltage converter can be set up to increase the voltage from the first side toward the second side. In particular, the galvanic isolation DC voltage converter can be set up to convert the voltage of 400 volts at the first side into the voltage of 800 volts at the second side. These voltage values ​​are purely exemplary and can in particular deviate from the mentioned numerical values ​​by at least 10% or 25%.

[0019] In addition, a single-phase or multi-phase AC voltage charging terminal can be provided. The AC voltage charging terminal of the vehicle's onboard power system is preferably connected to the first side of the current-isolating DC voltage converter via a power factor correction filter of the vehicle's onboard power system. The AC voltage charging terminal is connected to the first connection point or to a direct connection switch, in particular via a power factor correction filter. The AC voltage terminal is therefore connected to the battery via a power factor correction filter and a direct connection switch, which is connected downstream of the power factor correction filter. In addition, if a terminal converter is provided, the AC voltage charging terminal can be connected to the terminal converter via a power factor correction filter, which in turn leads to the DC voltage charging terminal via an isolating switch. When charging is performed with the aid of an AC voltage, the switch that is also provided between the battery and the DC voltage charging terminal is disconnected, preferably exactly the same as the isolating switch mentioned.

[0020] Instead of a power factor correction filter, another rectifying element can also be provided, for example a rectifier without a step-up or step-down function.

[0021] The vehicle onboard power supply system can also have an intermediate circuit capacitor circuit. The intermediate circuit capacitor circuit is connected to the first side of the galvanically isolated DC voltage converter. The intermediate circuit capacitor circuit can have a plurality of capacitors, which are configurable. In other words, the intermediate circuit capacitor circuit can be configurable and have a plurality of capacitors, which can be selectively connected in parallel or in series with one another (by means of a switchable configuration circuit). In this case, the corresponding switches connect the capacitors in parallel in a first configuration state and in series in a second configuration state.

[0022] The electric drive is connected to the second side of the galvanically isolated DC voltage converter. In this case, the second side of the galvanically isolated DC voltage converter can represent the on-board power supply branch to which the electric drive is connected, but the electric drive can also constitute a part of the on-board power supply branch. Alternatively or in combination with the electric drive planning (Antriebplan), one or more other components can be connected to the second side of the galvanically isolated DC voltage converter. In this case, the second side of the galvanically isolated DC voltage converter is connected to at least one other component. These components can be constructed as an electric heating device for the interior space, as a heat cycle (for example, at a power electronics device and / or an electric drive) or an electric heating device for an exhaust gas aftertreatment device. Other components can also be constructed as an electric air conditioning compressor, an inductive charging unit or a low-voltage DC voltage converter. Other components can be connected to the low-voltage DC voltage converter, especially the low-voltage on-board power supply branch can be connected to the low-voltage DC voltage converter. Other components such as previously constructed can be connected to the galvanically isolated DC voltage converter (especially connected to its second side). If a plurality of components are connected to the second side of the galvanically isolating DC voltage converter, these components can be designed identically and as described above, or they can be designed differently, as described above.

[0023] Furthermore, the discharge device can be connected to the second side of the galvanically isolated DC voltage converter. In this case, the discharge device is part of the vehicle electrical system. The discharge device in particular discharges the intermediate circuit capacitor and / or the Cy capacitor (between ground and supply potential). In particular, the discharge circuit can be set up to discharge the capacitance between two supply potentials.

[0024] In addition, in one embodiment, the battery can be arranged in a first housing, the drive switch, direct connection switch and charging terminal switch (if necessary, as well as the isolating switch and terminal converter) can be arranged in a second housing, and the current-isolating DC voltage converter can be arranged in a third housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 and 2 Various possibilities for realizing the onboard electrical system of a vehicle described here are shown by way of example. DETAILED DESCRIPTION

[0026] Figure 1A vehicle onboard power supply system FB is shown with a galvanically isolated DC voltage converter (Gleichspannungswandler) GW. In addition, the vehicle onboard power supply system FB includes a battery AK. The battery AK is connected to the DC voltage converter GW via a direct connection switch S1, in particular to the first side of the DC voltage converter. The battery is also connected to the second side of the galvanically isolated DC voltage converter GW via a drive switch. In addition, other components (symbolically shown as AUX) and an electric drive EA are connected to the second side of the galvanically isolated DC voltage converter GW. The electric drive EA includes an electric motor EM, which is connected to the second side of the galvanically isolated DC voltage converter GW via an inverter. Switches S1 and S2 meet at a first connection point VP. The second connection point VP2 is the point where switches S1 and S2 meet. Switch S1 is therefore connected between the first connection point VP1 and the second connection point VP2.

[0027] The DC voltage charging terminal DC is connected to the first side of the DC voltage converter GW via a switch S2 (and a first connection point VP1). Switches S1 and S2 together form a connecting circuit VS. The galvanically isolated DC voltage converter GW is therefore connected both to the DC voltage charging terminal DC and to the battery AK via a switchable connecting circuit VS.

[0028] Battery switching or configuration can be avoided, in which the DC voltage converter GW is provided with a galvanic isolation (galvanische Trennung) in order to avoid electric shock in the event of an insulation fault. It is further provided that the AC voltage charging terminal AC is connected to the first side of the galvanically isolated DC voltage converter GW via a power factor correction filter LF (for example, constructed as a Vienna filter) in order to thereby also be able to achieve an AC voltage level (Wechselspannungslage). A configurable intermediate circuit capacitor C is connected to the first side of the DC voltage converter GW. The intermediate circuit capacitors C can be connected in parallel or in series with each other in order to thereby set a high total capacitance or a high voltage carrying capacity in a switchable manner. First, the switch S1 is preferably opened and the switch S2 is closed. This is performed when charging is to take place or when the controller C is in a charging mode, in particular a DC voltage charging mode. The controller ST is controlled in a controlled manner with the controller C. Figure 1 The switches S1 to S3 shown in FIG. 1 are connected, in particular also to the switches of the intermediate circuit capacitor circuit C. In FIG.

[0029] The controller ST can open the switch S1 and close the switch S2 in order to prepare for the charging mode. The intermediate circuit capacitor circuits C can then be placed in parallel (by the controller ST), wherein the intermediate circuit capacitors are in this case connected in parallel with one another. It is provided that the DC voltage converter then converts the voltage applied on the first side and passes it to the battery via the switch S3 which is then to be closed. It is therefore provided that after the intermediate circuit capacitor circuits C have been configured in parallel, the switch S3 is closed.

[0030] According to one variant, the vehicle electrical system includes a transmitter SE which can communicate with an (external) DC voltage charging station and is designed to set the voltage of the charging station to a non-variable voltage during charging, for example to substantially 400 V. A galvanically isolated DC voltage converter GW takes over the adaptation of the charging voltage.

[0031] The discharge device EV on the second side of the galvanically isolating DC voltage converter serves for discharging and can be activated in particular after the charging process has been completed.

[0032] Figure 2 Shown with Figure 1 This applies in particular to another vehicle electrical system which corresponds to the components of the components and differs only in the reference numerals with a prime sign. Figure 2 All reference numerals except S2' and VS'.

[0033] Figure 2 A vehicle electrical system FB is shown with a DC voltage charging terminal DC, which is connected to the vehicle electrical system FB via a charging terminal (connected to the vehicle electrical system FB). Figure 1 On the contrary) is directly connected to the battery or the second connection point VP2. Figure 1 In comparison, it is noticeable that there the switch S2 is directly connected to the connection point VP1 and thus indirectly connected to the battery AK via the switch S1, whereas in Figure 2 The middle switch S2' connects the DC voltage charging terminal DC to the second connection point VP2 and thus directly to the battery AK'. Figure 1 The difference between the variants.

[0034] therefore, Figure 2The vehicle on-board power grid FB also includes a switchable connection circuit VS', which includes a charging terminal switch S2', a direct connection switch S1' and a first connection point VP1. The terminal converter (Anschlusswandler) AW is connected to the first connection point, and the terminal converter is connected to the DC voltage terminal DC via an isolating switch S5' (in the absence of other switches). The terminal converter AW is non-galvanically isolated and has the function of a DC voltage converter. The DC voltage charging terminal DC is directly connected to the battery AK' via the switch S2'. The DC voltage charging terminal DC is connected to the second side of the DC voltage converter GW via the switch S5' and the terminal converter AW connected downstream of the switch. The direct connection switch S1' is located between the terminal converter AW and the battery.

[0035] In other respects, Figure 2 The vehicle onboard power system also has an electric drive EA and other components AUX, which are connected to the second side of the DC voltage converter GW and are thus isolated from the battery current as long as the switch S3' is opened. In this case, the switch S3' connects the second side of the galvanically isolated DC voltage converter GW to the battery AK' or to the second connection point VP2. Here, the electric drive also includes an electric motor EM, which is connected to the second side of the galvanically isolated DC voltage converter GW via an inverter IN. The second side of the DC voltage converter GW is therefore connected to the battery via the switch S3', while the connection between the battery and the first side of the DC voltage converter GW can be separated via the direct connection switch S1'. Switch S2' is also used here for separation, in particular for separating the DC voltage charging terminal DC from the battery. However, other connections are obtained from the DC voltage charging terminal DC via the terminal converter AW via the switch S5' to the first side of the DC voltage converter GW. The first side of the DC voltage converter is connected to a configurable intermediate circuit capacitor circuit C. As in Figure 1 As in the example, there are intermediate circuit capacitors here which can be connected in parallel or in series with one another in an operative manner.

[0036] The alternating voltage charging terminal AC is connected to a first side of the DC voltage converter GW via a power factor correction filter LF.

[0037] The controller ST' is used to control Figure 2 The switches shown in and are used to configure the intermediate circuit capacitor circuit C.

[0038] In order to charge the DC voltage with 400 volts in particular, S5' is closed, wherein the terminal converter AW increases the voltage. The terminal converter AW is constructed as a boost converter in this case, which boosts the DC voltage converter GW from the DC voltage charging terminal DC. The switch S2' is disconnected. The switch S1' is closed. During this charging state, the intermediate circuit capacitor circuit is in series mode, that is to say, the capacitors located there are connected in series with each other. Thus, the intermediate circuit capacitor circuit can handle a higher operating voltage than in the case of a parallel configuration. The switch S3 is preferably disconnected. Thus, energy can be introduced into the battery AK' from the DC voltage charging terminal DC via the switch S5', the terminal converter AW and the switch S1'. At the same time, the disconnected switch S3' ensures that the CY capacitor is separated from the battery AK or in particular from the DC voltage charging terminal DC current. In this case, the DC voltage converter GW of the current isolation is used to power the component AUX, and therefore can be constructed with a lower power than the terminal converter.

[0039] In order to travel (Fahren), according to Figure 1 and Figure 2 In a variant of this embodiment, the switch S3 or S3' can be closed, so that the battery AK, AK' can supply power to the electric drive EA.

[0040] exist Figure 1 The charging energy is conducted via the DC voltage converter GW, while Figure 2 In the example of FIG. 1 , it is provided that the terminal converter AW supplies energy from the DC voltage charging terminal DC to the battery AK′; the power transmitted via the DC voltage converter GW is due to Figure 2 The switch S3' is opened and is not transferred to the battery.

Claims

1. A vehicle electrical system (FB), comprising a DC voltage charging terminal (DC), a non-configurable battery (AK), a galvanically isolated DC voltage converter (GW) and an electric drive (EA), wherein the battery (AK) is connected to a first side of the DC voltage converter (GW) via a switchable connecting circuit (VS, VS'), the DC voltage charging terminal (DC) is connected to the switchable connecting circuit, and the battery (AK) is connected to the electric drive (EA) and the DC voltage via a drive switch (S3). The second side of the converter (GW) is connected, wherein the connecting circuit (VS, VS') has a direct connection switch (S1, S1'), which connects the battery (AK) to the first side of the DC voltage converter in a switchable manner, and the DC voltage charging terminal (DC) is connected to the direct connection switch (S1, S1') via the charging terminal switch (S2, S2') of the connecting circuit (VS, VS'), wherein the galvanically isolated DC voltage converter (GW) is configured to convert a first high voltage into a second high voltage.

2. The vehicle onboard power supply (FB) according to claim 1, wherein a charging terminal switch (S2) of the connecting circuit (VS) is connected to the side of the direct connection switch (S1) that is connected to the DC voltage converter (GW).

3. The vehicle onboard power supply (FB) according to claim 2, further comprising a control device, which is connected to the switches (S1, S2, S3) in a control manner, and is configured to control the charging terminal switch (S2) to be in a closed state, the direct connection switch (S1) to be in an open state, and the drive switch (S3) to be in a closed state in DC charging operation, and is configured to control the charging terminal switch (S2) and the direct connection switch (S1) to be in an open state, and to control the drive switch (S3) to be in a closed state in driving operation.

4. A vehicle onboard power system (FB) according to claim 1, wherein the charging terminal switch (S2') of the connecting circuit (VS') is connected to the side of the direct connection switch (S1') connected to the battery (AK), and the connecting circuit (VS') further has a current-connected terminal converter (AW), which is constructed as a DC voltage converter, and the DC voltage charging terminal (DC) is connected to the side of the direct connection switch (S1') connected to the DC voltage converter (GW) via the terminal converter (AW).

5. The vehicle onboard power system (FB) according to claim 4, wherein the vehicle onboard power system comprises a control device, which is connected to the switches (S1', S2', S3') in a control manner, and is configured to control the charging terminal switch (S2') to be in an open state, control the direct connection switch (S1) to be in a closed state, and control the drive switch (S3) to be in an open state during DC charging operation, and is configured to control the charging terminal switch (S2') and the direct connection switch (S1) to be in an open state, and control the drive switch (S3) to be in a closed state during driving operation.

6. A vehicle on-board power system (FB) according to claim 4 or 5, wherein the DC voltage charging terminal (DC) is connected to the terminal converter (AW) via an isolating switch (S5'), wherein the vehicle on-board power system is configured to set the isolating switch (S5') to a closed state only in a DC charging mode.

7. The vehicle onboard power supply (FB) according to claim 1, wherein the high voltage present on the second side of the galvanically isolating DC voltage converter (GW) is the higher of the two high voltages.

8. The vehicle onboard power grid (FB) according to any one of claims 1 to 5, further comprising an AC voltage charging terminal (AC), which is connected to the first side of the current-isolating DC voltage converter via a power factor correction filter (LF) of the vehicle onboard power grid (FB).

9. The vehicle onboard power supply (FB) according to any one of claims 1 to 5, further comprising an intermediate circuit capacitor circuit (C), the intermediate circuit capacitor circuit (C) having a plurality of capacitors which can be selectively connected in parallel or in series with one another.

10. The vehicle onboard power supply (FB) according to claim 1 , wherein at least one further component (AUX) is connected to the second side of the galvanically isolated DC voltage converter (GW), wherein the component is designed as follows: Electrical heating devices for interior spaces, for heat circuits or for exhaust gas aftertreatment devices, Electric air conditioning compressor, Inductive charging unit, or A low-voltage DC voltage converter with a connected low-voltage onboard electrical system branch.

11. The vehicle onboard power supply system (FB) according to claim 1, wherein a discharge device (EV) is connected to the second side of the galvanically isolated DC voltage converter (GW).

12. A vehicle onboard power system (FB) according to any one of claims 1 to 5, wherein the battery (AK) is arranged in a first housing, the drive switch (S3), the direct connection switch (S1, S1') and the charging terminal switch (S2, S2') are arranged in a second housing, and the current-isolating DC voltage converter (GW) is arranged in a third housing.

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