DE102021003831A1 - On-board electrical system for a vehicle, vehicle with an on-board electrical system and method for operating an on-board electrical system for a vehicle - Google Patents

Abstract

The invention relates to an on-board electrical system (1) for a vehicle (2), comprising a battery (3) with two electrical battery potential contacts and a vehicle-side DC charging connection (4) with two electrical charging potential contacts. According to the invention, a DC-DC converter (5) is provided, the first electrical battery potential contact can be or is electrically coupled to a first electrical potential contact on an output side of the DC-DC converter (5), wherein the second electrical battery potential contact can be electrically coupled or is coupled to the second electrical charging potential contact, the respective electrical charging potential contact having a respective electrical potential contact on an input side of the DC-DC converter (5) can be electrically coupled or is coupled, a second electrical potential contact on the output side of the DC-DC converter (5) being connected to the first electrical potential contact of the egg input side of the DC-DC converter (5) can be electrically coupled or is coupled, with the electrical potential contacts on the input side of the DC-DC converter (5) being electrically coupled to one electrical connection contact of a first capacitor (C1), and the electrical potential contacts on the output side of the DC-DC converter (5) having are each electrically coupled or coupled to an electrical connection contact of a second capacitor (C2).

Description

The invention relates to an on-board electrical system for a vehicle according to the features of the preamble of claim 1, a vehicle with an on-board electrical system and a method for operating an on-board electrical system for a vehicle.

Are from the prior art, as in the DE 10 2017 213 682 A1 described, a battery charging device for a motor vehicle, a method for operating a motor vehicle-side battery charging device, a high-voltage electrical system and a use of a battery charging device is known. The battery charging device is designed to be arranged in the motor vehicle. It comprises a first stage, which has a power correction filter, and a second stage, which has an inverter. The first stage is electrically connected to the second stage via an intermediate point. The intermediate point is electrically connected directly to a feed connection for DC voltage, which is set up for direct electrical coupling to a high-voltage vehicle electrical system of the motor vehicle.

The object of the invention is to provide an on-board electrical system for a vehicle that is improved compared to the prior art, a vehicle with an on-board electrical system that is improved compared to the prior art, and a method for operating an on-board electrical system for a vehicle that is improved compared to the prior art to specify.

The object is achieved according to the invention by an on-board electrical system for a vehicle having the features of claim 1, a vehicle with an on-board electrical system having the features of claim 9 and a method for operating an on-board electrical system for a vehicle having the features of claim 10.

Advantageous configurations of the invention are the subject matter of the dependent claims.

An on-board electrical system, in particular a high-voltage on-board electrical system, for a vehicle, in particular for an electric vehicle or hybrid vehicle, includes a battery, in particular a high-voltage battery, with two electrical battery potential contacts and a vehicle-side DC charging connection with two electrical charging potential contacts.

The term "high voltage" is to be understood in particular as an electrical direct voltage which is in particular greater than approximately 60 volts. In particular, the term “high voltage” must be interpreted in accordance with the ECE R 100 standard.

According to the invention, a DC-DC converter, also referred to as a DC-DC converter, is provided, the first electrical battery potential contact being electrically coupleable or coupled to a first electrical potential contact on an output side of the DC-DC converter, the second electrical battery potential contact being electrically coupleable or coupled to the second electrical charge potential contact is, wherein the respective electric charge potential contact can be electrically coupled or is coupled to a respective electric potential contact on an input side of the DC-DC converter, wherein a second electric potential contact on the output side of the DC-DC converter can be electrically coupled or is coupled to the first electric potential contact on the input side of the DC-DC converter, wherein the electric potential contacts the input side of the DC-DC converter, each with an electrical connection contact of a first Kond ensators are electrically coupled, and the electrical potential contacts of the output side of the DC-DC converter can be electrically coupled or are coupled to one electrical connection contact of a second capacitor.

A vehicle according to the invention includes such an on-board electrical system.

The solution according to the invention enables the battery to be electrically charged by means of a direct current energy source external to the vehicle, in particular a direct current charging station, which is connected to the direct current charging connection on the vehicle and whose charging voltage is lower than a nominal battery voltage. For example, the battery has a nominal battery voltage of 800V. So far it has not been possible, or only with complex additional measures, to charge such a battery with a high nominal battery voltage of, for example, 800 V at a vehicle-external direct current energy source with a lower charging voltage of, for example, 400 V or 500 V. The previously known additional measures require a large number of additional components and are therefore expensive, require a larger installation space and are associated with a higher weight. This problem is solved by the solution according to the invention, in which case the DC-DC converter and advantageously also at least one of the capacitors are already provided in conventional on-board electrical systems, for example for AC charging of the battery from an AC energy source, and by the circuitry described and, if necessary, a different design the capacity of one of the capacitors or both capacitors now also for such electric direct current charging gears where the charging voltage is lower than the nominal battery voltage.

The on-board electrical system, in particular a high-voltage on-board electrical system, therefore advantageously has integrated downward charging compatibility. When electrically charging the battery with a high nominal battery voltage of 800 V, for example, at an external direct current energy source, in particular a direct current charging station, with a lower charging voltage of 400 V, for example, half of the charging power flows directly from the direct current charging station into the battery. The DC charging station provides exactly half of the charging voltage required for the battery. The remaining part of the charging power is supplied to the battery via the DC/DC converter. The maximum charging power is therefore twice as high as the power of the DC-DC converter. The DC-DC converter converts the voltage by a factor of 1, i. H. an input voltage corresponds to an output voltage due to galvanic isolation to a higher potential level, so that the total is the nominal battery voltage.

The voltage divider is advantageously connected to capacitances, i. H. realized with capacitors that already exist as part of an on-board charging device for electrically charging the battery at an AC energy source, in particular AC charging station, and are only newly designed. The second capacitor is part of an EMC filter, for example, and stores the energy of the "upper half of the voltage". The first capacitor is, for example, a component of an input intermediate circuit of the first DC-DC converter and stores the "lower half" of the voltage level of the nominal battery voltage of, for example, 800 V. The solution described thus advantageously uses already existing Cx capacitances of the on-board charging device, in particular for the first capacitor and/or or for the second capacitor, which are simply redesigned, for example.

In one possible embodiment, the DC-DC converter is a component of the already mentioned on-board charging device for electrically charging the battery using an AC power source external to the vehicle. This vehicle-mounted charging device, also referred to as an on-board charger, is thus provided in particular for converting an alternating current and/or an alternating voltage from such an external vehicle alternating current energy source into a direct current or a direct voltage. As already mentioned, the DC-DC converter is therefore advantageously part of the vehicle's on-board electrical system anyway, so that no additional components are required in this regard. In order to also use this DC-DC converter for electrically charging the battery using a DC energy source whose charging voltage is lower than the nominal battery voltage, the circuitry described above is used.

In an advantageous embodiment, the first capacitor and/or the second capacitor is/are a component of the on-board charging device for electrically charging the battery using an AC power source external to the vehicle. The second capacitor is, for example, part of an EMC filter (EMC=Electromagnetic Compatibility). As a result, no additional components are required in this regard either. If necessary, only a different design of the first and/or second capacitor with regard to its/its capacity is required.

In one possible embodiment, the first capacitor and the second capacitor have the same capacitance. The voltage of the vehicle-external direct current energy source, in particular direct current charging station, is then exactly half the nominal battery voltage during the charging process. In addition, half of the charging power flows through the DC-DC converter. Thus, the charging power can be twice as large as a component power of the DC-DC converter. This variant is therefore particularly suitable for charging at a vehicle-external DC energy source whose charging voltage is half the nominal battery voltage, ie 400 V or at least 400 V for a nominal battery voltage of 800 V, for example.

In one possible embodiment, the first capacitor has a larger capacitance than the second capacitor. As a result, depending on the voltage level of the battery and the vehicle-external direct current energy source, the charging power can be further increased with the first direct current converter remaining unchanged. This embodiment is therefore particularly suitable for charging at a vehicle-external direct current energy source, the charging voltage of which is greater than half the nominal battery voltage and less than the nominal battery voltage of 800 V, for example.

In one possible embodiment, the DC-DC converter is designed as a bidirectional DC-DC converter. It advantageously has no diodes on its secondary side, but advantageously semiconductor switches. It therefore enables simpler pre-charging, for example of at least one high-voltage intermediate circuit. Furthermore, can bidirectional AC charging with an AC voltage at an AC energy source, in particular an AC charging station, and bidirectional DC charging at a DC energy source, in particular a DC charging station, with a low charging voltage, in particular with half the nominal battery voltage, with the nominal battery voltage being 800 V and the charging voltage being 400 V, for example, will be realized.

In one possible embodiment, the DC-DC converter is designed as a DC-DC converter with a short-circuit function. This variant of the DC-DC converter is cheaper than the bidirectional DC-DC converter. It includes diodes on its secondary side.

In one possible embodiment, the first electrical battery potential contact can be electrically coupled or is coupled to the first electrical charging potential contact. This also enables the battery to be electrically charged by means of an external direct current energy source connected to the vehicle's direct current charging connection, in particular a direct current charging station, whose charging voltage is equal to or greater than the battery's nominal voltage, for example at an external direct current energy source with a charging voltage of 800 V, the Battery, as mentioned above, for example, has a nominal battery voltage of 800 V.

In one possible embodiment, the second electrical potential contact on the output side of the DC-DC converter can be electrically coupled or is coupled to the second electrical battery potential contact. This also enables the battery to be electrically charged by means of an AC energy source external to the vehicle, in particular an AC charging station.

In a method according to the invention for operating such an on-board electrical system, the first electrical battery potential contact is electrically coupled to the first electrical potential contact on the output side of the DC-DC converter for electrically charging the battery using an on-board direct current charging connection connected to the vehicle-external direct current energy source, the charging voltage of which is lower than a nominal battery voltage of the battery , the second electrical battery potential contact is electrically coupled to the second electrical charging potential contact, the respective electrical charging potential contact is electrically coupled to the respective electrical potential contact on the input side of the DC-DC converter, and the second electrical potential contact on the output side of the DC-DC converter is electrically coupled to the first electrical potential contact on the input side of the DC-DC converter. Furthermore, the respective electrical potential contact on the output side of the DC-DC converter is advantageously electrically coupled to the respective electrical connection contact of the second capacitor if this respective coupling is not permanently connected anyway, i. H. if this respective coupling is switchable.

Alternatively or additionally, the first electrical battery potential contact is electrically coupled to the first electrical charging potential contact and the second electrical battery potential contact is electrically coupled to the second electrical charging potential contact for electrically charging the battery using an external vehicle direct current energy source connected to the vehicle-side direct current charging connection, the charging voltage of which is equal to or greater than the nominal battery voltage of the battery electrical charging potential contact electrically coupled. It can be provided that the respective electrical potential contact on the output side of the DC-DC converter is electrically coupled to the respective electrical connection contact of the second capacitor if this respective coupling is not permanently connected anyway, i. H. if this respective coupling can be switched, or it can be provided that this does not take place.

Alternatively or additionally, the first electrical battery potential contact is electrically coupled to the first electrical potential contact on the output side of the DC-DC converter and the second electrical potential contact on the output side of the DC-DC converter is electrically coupled to the second electrical battery potential contact for electrically charging the battery using an AC power source external to the vehicle. It can be provided that the respective electrical potential contact on the output side of the DC-DC converter is electrically coupled to the respective electrical connection contact of the second capacitor if this respective coupling is not permanently connected anyway, i. H. if this respective coupling can be switched, or it can be provided that this does not take place.

The method according to the invention, in combination with the above-described on-board electrical system, for whose operation it is intended, advantageously enables the battery to be electrically charged at a direct current energy source, in particular a direct current charging station whose charging voltage is lower than the nominal battery voltage, the battery is electrically charged at a direct current energy source , in particular DC charging station tion, the charging voltage of which corresponds to the nominal battery voltage, and the electrical charging of the battery at an AC power source, in particular an AC charging station. This achieves a very high level of flexibility with regard to charging options for charging the battery electrically.

The on-board electrical system also includes, for example, at least one electric drive unit or several such electric drive units for driving the vehicle, for example at least one front electric drive unit, in particular on or in the area of a front axle of the vehicle, and/or at least one rear electric drive unit, in particular on or in Area of a rear axle of the vehicle. When the vehicle is being driven, the respective electric drive unit is supplied with electric energy by the battery.

The configuration of the on-board electrical system described advantageously makes it possible to disconnect the electric drive units from the electric energy supply during electric charging processes, in particular during electric charging of the battery at an electric DC energy source with a high charging voltage, which corresponds in particular to the nominal battery voltage of, for example, 800 V. in particular from the battery and advantageously also from the respective energy source used for charging, in particular direct current energy source, to be separated, in particular to be galvanically separated. As a result, Y capacitors of the electric drive units, also referred to as Cy capacitors or Y capacitors, remain discharged. These Y-capacitors therefore no longer contribute to the overall capacitance of the on-board electrical system. As a result, Y-capacitors with large capacities can be installed without exceeding the permissible limit. As a result, safety limit values of the Y-capacitors or Y-capacitors of the vehicle with regard to their energy content can be complied with and, in particular, EMC requirements (EMC=electromagnetic compatibility) of the vehicle and in particular of the on-board electrical system can be complied with. The effect of Y-capacitors in the area of electromagnetic compatibility, in particular radio interference suppression, is known to the person skilled in the art, so that no further separate explanations are required in this regard. In addition, reference is made to the relevant standards, such as Directive 2013/30/EU on electromagnetic compatibility, EM 61000 and others.

For reasons of electrical safety, electrical energy stored in all of the Y capacitors should not exceed a predeterminable maximum value. Such a value is, for example, 0.2 J. This regularly leads to a constructive design such that the capacitance values of the Y capacitors on the vehicle side are generally selected to be smaller than is required for proper electromagnetic compatibility, in particular with regard to the electrical Components that are connected to the electrical system would be necessary. Among other things, it has turned out to be problematic if the vehicle is to be charged by means of a direct voltage from a direct current charging station, ie by means of a direct current energy source. In such a case
the total capacity of Y-capacitors provided on the vehicle proves to be a hindrance, because these Y-capacitors can also cause a leakage current, which can lead to a fault being triggered on the charging station side and/or can exceed a permissible value for the leakage currents in electrical systems overall, as is the case, for example, in the standard is also specified, for example in the standard DIN EN 61800 or the like. Basically, this problem can only be solved by reducing the capacitance values of the Y-capacitors provided in the vehicle, whereby it should be noted, however, that this can significantly increase the cost of the filter units.

In addition, it is particularly when charging by means of a DC voltage, i. H. by means of a DC power source, requires that an energy content of all effective Y-capacitors does not exceed a predetermined total energy content. A maximum value of 0.2 J is currently provided for this, which should not be exceeded. Due to the large number of electrical components in the vehicle and the increasing performance, for example in the case of high-voltage components, the total capacity of the existing Y-capacitors is increasing, which means that the energy content stored there also increases in accordance with the increasing total capacity. It should also be noted that the energy content of the Y-capacitors is particularly critical, particularly in the high-voltage range, especially since it should be noted that the electrical energy stored in the Y-capacitors is quadratically dependent on the electrical voltage of the Y-capacitors. This makes it particularly difficult to meet the requirements with regard to the maximum energy content in relation to the respective high-voltage potential, especially in the high-voltage area. Especially in the case of vehicles, it has proven to be problematic to meet both requirements with regard to electromagnetic compatibility and requirements with regard to electrical safety with regard to the energy of the Y capacitors at the same time.

These problems are eliminated by the on-board electrical system described here, because this on-board electrical system advantageously allows various operating modes of the vehicle to be optimized for relevant requirements. This enables the Y-capacitors of the individual functions to be designed taking into account the vehicle states to be assumed in each case.

Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

• 1 schematisch ein Fahrzeug mit einer ersten Ausführungsform eines elektrischen Bordnetzes,
• 2 schematisch einen Gleichspannungswandler mit Kurzschlussfunktion,
• 3 schematisch einen bidirektionaler Gleichspannungswandler,
• 4 schematisch die erste Ausführungsform des elektrischen Bordnetzes während eines Betriebszustands Fahren,
• 5 schematisch die erste Ausführungsform des elektrischen Bordnetzes während eines Betriebszustands Laden an einer Gleichstromenergiequelle mit einer hohen Ladespannung,
• 6 schematisch die erste Ausführungsform des elektrischen Bordnetzes während eines Betriebszustands Laden an einer Gleichstromenergiequelle mit einer niedrigen Ladespannung,
• 7 schematisch die erste Ausführungsform des elektrischen Bordnetzes während eines Betriebszustands Laden an einer Wechselstromenergiequelle,
• 8 schematisch die erste Ausführungsform des elektrischen Bordnetzes während eines Vorladens für den Betriebszustand Fahren,
• 9 schematisch die erste Ausführungsform des elektrischen Bordnetzes während eines Vorladens für den Betriebszustand Laden an einer Gleichstromenergiequelle mit einer hohen Ladespannung,
• 10 schematisch die erste Ausführungsform des elektrischen Bordnetzes während eines Vorladens für den Betriebszustand Laden an einer Gleichstromenergiequelle mit einer niedrigen Ladespannung bei Verwendung des Gleichspannungswandlers mit Kurzschlussfunktion,
• 11 schematisch die erste Ausführungsform des elektrischen Bordnetzes während eines Vorladens für den Betriebszustand Laden an einer Gleichstromenergiequelle mit einer niedrigen Ladespannung bei Verwendung des bidirektionalen Gleichspannungswandlers, und
• 12 schematisch ein Fahrzeug mit einer zweiten Ausführungsform eines elektrischen Bordnetzes.

show:

• 1 schematically a vehicle with a first embodiment of an electrical system,
• 2 schematic of a DC-DC converter with short-circuit function,
• 3 schematic of a bidirectional DC-DC converter,
• 4 schematically the first embodiment of the electrical system during an operating state driving,
• 5 Schematically the first embodiment of the on-board electrical system during an operating state of charging at a direct current energy source with a high charging voltage,
• 6 Schematically the first embodiment of the on-board electrical system during an operating state of charging at a direct current energy source with a low charging voltage,
• 7 Schematically the first embodiment of the on-board electrical system during an operating state of charging at an AC energy source,
• 8th Schematically the first embodiment of the on-board electrical system during pre-charging for the driving operating state,
• 9 Schematically the first embodiment of the on-board electrical system during pre-charging for the charging operating state at a direct current energy source with a high charging voltage,
• 10 Schematically the first embodiment of the on-board electrical system during pre-charging for the charging operating state at a DC energy source with a low charging voltage when using the DC-DC converter with a short-circuit function,
• 11 schematically shows the first embodiment of the on-board electrical system during pre-charging for the charging operating state at a DC energy source with a low charging voltage when using the bidirectional DC-DC converter, and
• 12 schematically a vehicle with a second embodiment of an electrical system.

Corresponding parts are provided with the same reference symbols in all figures.

The following are based on the 1 until 12 a vehicle electrical system 1 designed in particular as a high-voltage vehicle electrical system for a vehicle 2 designed in particular as an electric vehicle or hybrid vehicle and a vehicle 2 with such a vehicle electrical system 1 and a method for operating such a vehicle electrical system 1 are described.

For reasons of clarity, only the on-board electrical system 1, which is designed in particular as a high-voltage on-board electrical system, is shown with its components of the vehicle 2.

In order to charge a battery 3 of the vehicle 2 with a high nominal battery voltage of 800 V, for example, with direct current, it has hitherto been necessary to connect it to a direct current charging station that is designed for the voltage level of the battery 3 . This is not the case across the board. Consequently, it is advantageous in such vehicles 2 to allow direct current charging capability at direct current charging stations with a lower charging voltage, for example up to a maximum of 500 V, which are available in larger numbers. An additional component in the form of a so-called boost converter, for example, has hitherto been used, particularly when downward compatibility with medium charging power is sufficient or the functionality is not required across the board. However, this is expensive and difficult.

The solution described below solves this problem in that an on-board charging device 6 with boost functionality advantageously takes over the functionality of the boost converter with a small number of additional components and with higher charging power, while at the same time offering other advantages, in particular a reduction in Cy capacitances in the case of direct current charging remain. Furthermore, pre-charging methods for various operating states are presented and described below.

The electrical system 1 is a direct current network. It therefore has an electrical plus potential and an electrical minus potential, referred to below as the first electrical potential P1 and the second electrical potential P2. In the embodiments shown here, for example, the first electrical potential P1 is the electri cal plus potential and the second electric potential P2 the electric minus potential. However, it can also be provided that the first electrical potential P1 is the electrical minus potential and the second electrical potential P2 is the electrical plus potential.

The on-board electrical system 1 includes the battery 3, in particular a high-voltage battery, with two electrical battery potential contacts, d. H. with a first electrical battery potential contact for the first electrical potential P1, for example the electrical positive potential, and a second electrical battery potential contact for the second electrical potential P2, for example the electrical negative potential. The battery 3 has a nominal battery voltage of 800 V, for example.

Furthermore, the on-board electrical system 1 includes a vehicle-side DC charging connection 4. A vehicle-external DC energy source, in particular a vehicle-external DC charging station, can be connected to this vehicle-side DC charging connection 4 for electrically charging the battery 3. The off-vehicle DC charging port 4 includes two electrical charging potential contacts, i. H. a first electrical charge potential contact for the first electrical potential P1, for example the electrical plus potential, and a second electrical charge potential contact for the second electrical potential P2, for example the electrical minus potential.

In order to enable battery 3 to be electrically charged by means of an external direct current energy source connected to the vehicle's direct current charging connection 4, in particular a direct current charging station, the charging voltage of which is lower than the nominal battery voltage of the battery 3, for example at an external direct current energy source with a charging voltage of 400 V or 500 V the battery 3, as mentioned above, has a nominal battery voltage of 800 V, for example, it is provided that the on-board electrical system 1 has a DC-DC converter 5, also referred to below as the first DC-DC converter 5.

This first DC-DC converter 5 comprises an input side with two electrical potential contacts, i. H. with a first electrical potential contact for the first electrical potential P1, for example the electrical plus potential, and a second electrical potential contact for the second electrical potential P2, for example the electrical minus potential, and an output side with two electrical potential contacts, d. H. with a first electrical potential contact for the first electrical potential P1, for example the electrical positive potential, and a second electrical potential contact for the second electrical potential P2, for example the electrical negative potential.

The first electrical battery potential contact can be or is electrically coupled to the first electrical potential contact on the output side of the first DC-DC converter 5, the second electrical battery potential contact can be electrically coupled or is coupled to the second electrical charge potential contact, the respective electrical charge potential contact is connected to the respective electrical potential contact on the input side of the first DC-DC converter 5 can be electrically coupled or is coupled, the second electrical potential contact on the output side of the first DC-DC converter 5 can be electrically coupled or is coupled to the first electrical potential contact on the input side of the first DC-DC converter 5, the electrical potential contacts on the input side of the first DC-DC converter 5 are each equipped with an electrical connection contact first capacitor C1 electrically coupled and the electrical potential contacts of the output The sides of the first DC voltage converter 5 can each be electrically coupled or are coupled to an electrical connection contact of a second capacitor C2. In the first embodiment according to the 1 and 3 until 11 Both electrical potential contacts of the output side of the first DC voltage converter 5 are electrically coupled in each case to an electrical connection contact of the second capacitor C2. In the second embodiment according to 12 one of the electrical potential contacts on the output side of the first DC voltage converter 5 is permanently electrically coupled to one of the electrical connection contacts of the second capacitor C2 and the other electrical potential contact on the output side of the first DC voltage converter 5 can be coupled to the other electrical connection contact of the second capacitor C2, i.e. can be switched either to to couple or to decouple.

This makes it possible in the method for operating the on-board electrical system 1 to charge the battery 3 electrically using a vehicle-external direct current energy source which is connected to the direct current charging connection 4 on the vehicle and whose charging voltage is lower than the nominal battery voltage of the battery 3 by, as in 6 shown, the first electrical battery potential contact is electrically coupled to the first electrical potential contact of the output side of the first DC-DC converter 5, the second electrical battery potential contact is electrically coupled to the second electrical charging potential contact, the respective electrical charging potential contact to the respective electrical potential contact of the one output side of the first DC voltage converter 5 is electrically coupled and the second electrical potential contact of the output side of the first DC voltage converter 5 is electrically coupled to the first electrical potential contact of the input side of the first DC voltage converter 5 . Furthermore, the respective electrical potential contact on the output side of the first DC voltage converter 5 is advantageously also electrically coupled to the respective electrical connection contact of the second capacitor C2 if this respective coupling is not, as in the first embodiment according to FIGS 1 and 3 until 11 , Is already firmly connected, but as in the second embodiment according to 12 provided for one of the two electrical potential contacts on the output side of the first DC voltage converter 5 and the corresponding electrical connection contact of the second capacitor C2, can be switched. i.e. according to this second embodiment 12 this electrical potential contact on the output side of the first DC voltage converter 5 is advantageously also coupled to the corresponding electrical connection contact of the second capacitor C2 by appropriate switching. The other electrical potential contact on the output side of the first DC voltage converter 5 is already permanently connected here to the corresponding electrical connection contact of the second capacitor C2.

The first capacitor C1 and the second capacitor C2 have the same capacitance, for example. The voltage of the vehicle-external DC energy source is then exactly half the nominal battery voltage during the charging process. In addition, half of the charging power flows via the first DC-DC converter 5. The charging power can thus be twice as high as a component power of the first DC-DC converter 5. This embodiment is therefore particularly suitable for charging at a DC power source external to the vehicle, the charging voltage of which is half the nominal battery voltage , with a nominal battery voltage of 800 V, for example, is 400 V or at least 400 V.

Alternatively, it can be provided, for example, that the first capacitor C1 has a greater capacitance than the second capacitor C2. As a result, depending on the voltage level of the battery 3 and the vehicle-external direct current energy source, the charging power can be further increased with the first direct current converter 5 remaining unchanged. This variant is therefore particularly suitable for charging at a vehicle-external direct current energy source, the charging voltage of which is greater than half the nominal battery voltage and less than the nominal battery voltage of 800 V, for example.

In order to also enable electrical charging of the battery 3 by means of an external direct current energy source connected to the vehicle's direct current charging connection 4, in particular a direct current charging station, whose charging voltage is equal to or greater than the nominal battery voltage of the battery 3, for example at an external direct current energy source with a charging voltage of 800 V , wherein the battery 3, as mentioned above, has, for example, a nominal battery voltage of 800 V, it is additionally provided that the first electrical battery potential contact can be electrically coupled or is coupled to the first electrical charging potential contact.

This makes it possible in the method for operating the on-board electrical system 1 to charge the battery 3 electrically by means of a vehicle-external direct current energy source which is connected to the direct current charging connection 4 on the vehicle and whose charging voltage is equal to or greater than the nominal battery voltage of the battery 3 by, as in 5 shown, the first battery electrical potential contact is electrically coupled to the first charging potential electrical contact and the second battery electrical potential contact is electrically coupled to the second charging potential electrical contact. Furthermore, it can also be provided here that the respective electrical potential contact on the output side of the first DC voltage converter 5 is also electrically coupled to the respective electrical connection contact of the second capacitor C2 if this respective coupling is not permanently connected anyway, but at least for one of the two electrical potential contacts of the output side of the first DC voltage converter 5 and the corresponding electrical connection contact of the second capacitor C2, can be switched, or it can be provided that this does not take place.

In order to also enable electrical charging of the battery 3 by means of an AC energy source external to the vehicle, in particular an AC charging station, the vehicle 2, in particular its electrical system 1, comprises an on-board charging device 6 for charging the battery 3 electrically by means of such an AC energy source external to the vehicle. The first DC-DC converter 5 in the illustrated embodiments is part of this charging device 6 in the vehicle. The first capacitor C1 and/or the second capacitor C2 can also be a part of this charging device 6 in the vehicle. The second capacitor C2 is, for example, a component of a first EMC filter 7, which is in particular a component of this vehicle-mounted charging device 6, as in the example of the first Embodiment of the electrical system 1 according to 1 and 3 until 11 shown. According to the second embodiment 12 this first EMC filter 7 is not part of the on-board charging device 6. The second capacitor C2 is additionally provided here, i.e. it is not part of the first EMC filter 7 here, but is also a part of the on-board charging device 6.

In order to enable this electrical charging of the battery 3 by means of an AC energy source external to the vehicle, it is provided that the second electrical potential contact on the output side of the first DC voltage converter 5 can be electrically coupled or is coupled to the second electrical battery potential contact. Furthermore, it can also be provided here that the respective electrical potential contact on the output side of the first DC voltage converter 5 is also electrically coupled to the respective electrical connection contact of the second capacitor C2 if this respective coupling is not permanently connected anyway, but at least for one of the two electrical potential contacts of the output side of the first DC voltage converter 5 and the corresponding electrical connection contact of the second capacitor C2 can be switched, or it can be provided that this does not occur.

This makes it possible in the method for operating the on-board electrical system 1 to charge the battery 3 electrically using an AC power source external to the vehicle by, as in FIG 7 shown, the first electrical battery potential contact is electrically coupled to the first electrical potential contact of the output side of the first DC-DC converter 5 and the second electrical potential contact of the output side of the first DC-DC converter 5 is electrically coupled to the second electrical battery potential contact.

For charging the battery 3, the on-vehicle charging device 6 further includes a power factor correction filter 9, and in the first embodiment according to FIGS 1 and 3 until 11 and an AC EMC filter 10. Here, the power factor correction filter 9 is disposed between the input side of the first DC-DC converter 5 and an on-vehicle AC charging port 11 for connecting the on-vehicle AC power source, and the AC EMC filter 10, if present, is between the power factor correction filter 9 and the vehicle-side AC charging connector 11 are arranged.

As already mentioned, the on-board charging device 6 in the first embodiment of the on-board electrical system 1 according to FIG 1 and 3 until 11 the first EMC filter 7, which is arranged on the output side of the first DC-DC converter 5. Also in the second embodiment of the electrical system 1 according to 12 the first EMC filter 7 is provided, here outside of the vehicle-side charging device 6, but also on an output side of the first DC-DC converter 5. Thus, the respective electrical battery potential contact is not direct, but via the first EMC filter 7 with the respective electrical potential contact of the output side of the first DC-DC converter 5 can be electrically coupled or coupled.

In addition, in the illustrated embodiments, a second EMC filter 8 is provided in each case, which is arranged in front of the input side of the first DC-DC converter 5 and in particular outside of the vehicle-side charging device 6, in particular between the vehicle-side DC charging connection 4 and the input side of the first DC-DC converter 5. The respective electrical The charging potential contact is or will thus be electrically coupled via this second EMC filter 8 to the respective electrical potential contact on the input side of the first DC voltage converter 5 .

The first DC-DC converter 5 is designed, for example, as a DC-DC converter with a short-circuit function, as shown in FIG 2 shown, or formed as a bidirectional DC-DC converter, as in 3 shown. The first DC converter 5 designed as a DC converter with a short-circuit function is less expensive. It includes diodes D on its secondary side. The first DC-DC converter 5, designed as a bidirectional DC-DC converter, has no diodes D on its secondary side. The diodes D of the DC-DC converter with a short-circuit function are replaced here by semiconductor switches HL. It therefore enables simpler pre-charging, for example of at least one high-voltage intermediate circuit.

The on-board electrical system 1 also has, for example, at least one electric drive unit 12, 13 for driving the vehicle 2, in the embodiments shown here two such electric drive units 12, 13, for example a front electric drive unit 12 and a rear electric drive unit 13. The electric drive units 12, 13 can be coupled to the battery 3 or are coupled.

Furthermore, the on-board electrical system 1 has, for example, at least one secondary electrical consumer 14, 15, shown here Example two electrical auxiliary consumers 14, 15, for example an electric refrigerant compressor and an electric heating unit. The respective electrical auxiliary consumers 14, 15 can be coupled or coupled to the battery 3, in the example shown here via a distribution unit 16, also referred to as a Y-splice. The electrical auxiliary consumers 14, 15 are also referred to as electrical auxiliary units.

In addition, the vehicle electrical system 1, which is designed in particular as a high-voltage vehicle electrical system, includes a second DC-DC converter 17 and a vehicle electrical system connection 18 for connection to a further electrical system of the vehicle 2, not shown here, in particular a low-voltage vehicle electrical system, for example a 12V vehicle electrical system. The second DC-DC converter 17 and via this the vehicle electrical system connection 18 can be or is coupled to the electrical battery potential contacts of the battery 3, ie an input side of the second DC-DC converter 17 can be or is coupled to the electrical battery potential contacts of the battery 3, and an output side of the second DC-DC converter 17 is connected to coupled to the vehicle electrical system connection 18 . The input side of the second DC-DC converter 17 can be coupled directly to the electrical battery potential contacts of the battery 3, as in the first embodiment according to FIGS 1 and 3 until 11 , or via the first EMI filter 7 as in the second embodiment according to FIG 12 .

The on-board electrical system 1 also includes ten switching units S1 to S10, in particular to enable the charging variants described above for charging the battery 3 and also driving operation of the vehicle 2, for which the respective electric drive unit 12, 13 is supplied with electrical energy by the battery 3 and, for example, also to enable a pre-charging, which is described in more detail below, in particular of at least one high-voltage intermediate circuit. The operating states described in more detail below, in particular the different operating states for charging, the operating state driving and the different variants of pre-charging, advantageously belong to the method for operating the on-board electrical system 1, i. H. they are performed using this method.

The arrangement of the ten switching units S1 to S10 in the first specific embodiment of the on-board electrical system 1 according to FIGS 1 and 3 until 11 and how it works is described. Then the arrangement of these ten switching units S1 to S10 in the second embodiment of the electrical system 1 according to FIG 12 and how it works is described.

• Die Batterie 3 ist über ein erstes Potentialleitungspaar L1 mit den elektrischen Nebenverbrauchern 14, 15 verbunden, insbesondere über die Verteileinheit 16. Von diesem ersten Potentialleitungspaar L1 zweigt ein zweites Potentialleitungspaar L2 zum fahrzeugseitigen Gleichstromladeanschluss 4 ab, ein drittes Potentialleitungspaar L3 zur Ausgangsseite des ersten Gleichspannungswandlers 5, insbesondere zur Ausgangsseite der diesen ersten Gleichspannungswandler 5 umfassenden fahrzeugseitigen Ladevorrichtung 6, ab, und ein drittes Potentialleitungspaar L3 zum zweiten Gleichspannungswandler 17 und somit zum Bordnetzanschluss 18 für das insbesondere als Niedervoltbordnetz ausgebildete weitere elektrische Bordnetz ab.

The first is the arrangement of the ten switching units S1 to S10 in the first embodiment of the electrical system 1 according to FIG 1 and 3 until 11 and how it works:

• The battery 3 is connected to the electrical auxiliary consumers 14, 15 via a first pair of potential lines L1, in particular via the distribution unit 16. A second pair of potential lines L2 branches off from this first pair of potential lines L1 to the DC charging connection 4 on the vehicle side, and a third pair of potential lines L3 to the output side of the first DC-DC converter 5 , in particular to the output side of the vehicle-side charging device 6 comprising this first DC-DC converter 5, and a third potential line pair L3 to the second DC-DC converter 17 and thus to the vehicle electrical system connection 18 for the further electrical system, which is designed in particular as a low-voltage vehicle electrical system.

A fifth potential line pair L5 branches off from the second potential line pair L2 to the input side of the first DC voltage converter 5 and thus to the charging device 6 on the vehicle side that includes it.

The battery 3 is connected to the electric drive units 12, 13 via a sixth potential line pair L6

The first and second switching units S1, S2 are each arranged in a potential line between the respective electrical battery potential contact of the battery 3 and the respective electrical charging potential contact of the vehicle-side DC charging connection 4, in the example shown in the second potential line pair L2 seen from the vehicle-side DC charging connection 4 before the branch of the fifth potential line pair L5. In this case, the first and second switching units S1, S2 are designed together, for example, as a two-pole combined switching and safety device.

The third and fourth switching units S3, S4 are each arranged in a potential line between the respective electrical battery potential contact and the electrical drive units 12, 13. For this purpose, in the illustrated first embodiment according to the 1 and 3 until 11 separate connections are provided on the battery 3, which, however, each also form one of the electrical battery potential contacts of the battery 3. From these separate connections, the sepa rate sixth potential line pair L6 to the electric drive units 12, 13. The third and fourth switching units S3, S4 are also designed, for example, together as a two-pole combined switching and safety device.

The fifth and sixth switching units S5, S6 are each designed as changeover switches. They are each arranged in a potential line leading to the respective electrical potential contact on the input side of the first DC voltage converter 5, in particular before the first capacitor C1, i. H. the first capacitor C1 is arranged between the fifth or sixth switching unit S5, S6 and the respective electrical potential contact on the input side of the first DC voltage converter 5 between these two potential lines. Depending on the switching position of these switching units S5, S6, which are designed as changeover switches, either the vehicle-side DC charging connection 4 or the vehicle-side AC charging connection 11 can be electrically coupled to the input side of the first DC-DC converter 5 via the fifth and sixth switching unit S5, S6. For this purpose, the fifth and sixth switching units S5, S6 each have a switching contact electrically coupled to a potential line leading to the vehicle-side DC charging connection 4 and a switching contact electrically coupled to a potential line leading to the vehicle-side AC charging connection 11, between which by means of the respective fifth and sixth switching unit designed as a changeover switch S5, S6 can be switched. In the example shown, the switching contacts electrically coupled to the potential line leading to the DC charging connection 4 on the vehicle side are coupled to the potential lines of the fifth potential line pair L5; H. they form the end in the direction of the input side of the first DC-DC converter 5.

The fifth and sixth switching unit S5, S6 are arranged in particular in the charging device 6 on the vehicle. For example, the power factor correction filter 9 and, if present, the AC EMC filter 10 form a first stage and the first DC-DC converter 5 and, if present, the first EMC filter 7 form a second stage of the on-board charging device 6. The fifth and sixth switching unit S5 , S6 are then arranged between the first and second stages of the on-vehicle charging device 6 . By means of the fifth and sixth switching unit S5, S6 designed as a changeover switch, depending on the switching position, either the first stage of the on-board charging device 6, in particular its power factor correction filter 9, can be electrically coupled to the second stage of the on-board charging device 6 if the fifth and sixth switching unit S5, S6 are switched in the direction of the power factor correction filter 9, or the vehicle-side DC charging port 4 can be electrically coupled to the second stage of the vehicle-side charging device 6 when the fifth and sixth switching units S5, S6 are switched in the direction of the vehicle-side DC charging port 4.

The seventh and eighth switching units S7, S8 are each arranged in a potential line, which runs from the respective electrical battery potential contact of the battery 3 to the electrical auxiliary consumers 14, 15, to the output side of the first DC-DC converter 5, and thus in particular to the output of the on-board charging device 6 and its output side of the first DC-DC converter 5 downstream first EMC filter 7, and to the second DC-DC converter 17 and via this to the vehicle electrical system connection 18 for the other electrical vehicle electrical system, in particular the low-voltage vehicle electrical system. They are thus arranged in the example shown in the first pair of potential lines L1, in particular between the branch of the second pair of potential lines L2 and the branch of the third pair of potential lines L3. At least one of these two switching units S7, S8, in the example shown the eighth switching unit S8 in the potential line carrying the second electrical potential P2, is designed, for example, as shown, as a bidirectional semiconductor fuse, in particular with a freewheeling diode, or, for example, as a contactor or designed as a contactor with a fuse.

The ninth switching unit S9 is designed as a changeover switch. It is arranged in the potential line carrying the second electrical potential P2 on the output side of the first DC-DC converter 5 after the second capacitor C2, in the example shown also after the first EMC filter 7 comprising this second capacitor C2, and before the potential line branch leading to the battery 3. It is thus arranged in the potential line of the third potential line pair L3 carrying the second electrical potential P2 between the output side of the first DC voltage converter 5 after the second capacitor C2 and before the branch to the first potential line pair L1.

Via this ninth switching unit S9 designed as a changeover switch, this potential line carrying the second electrical potential P2 is on the output side of the first DC-DC converter 5 after the second capacitor C2, in the example shown also after the first EMC filter 7 comprising this second capacitor C2, depending on the Switching position of the ninth switching unit S9 either with the potential line carrying the second electrical potential P2 to the battery 3 electrically can be coupled, in the example shown via the branch to the first pair of potential lines L1 and the potential line of the first pair of potential lines L1 carrying the second electrical potential P2 to the battery 3, or can be electrically coupled to a bypass line BL which, with a corresponding switching position of the fifth switching unit S5, to the electrical potential contact of the first electrical potential P1 of the input side of the first DC voltage converter 5 leads.

In the example shown, this bypass line BL is electrically coupled to the potential line of the second potential line pair L2 carrying the first electrical potential P1, in the example shown between the branch to the first potential line pair L1 and the branch to the fifth potential line pair L5. As a result, when the ninth switching unit S9 and the fifth switching unit S5 are in the appropriate switching position, the electrical contact between the second electrical potential P2 carrying potential line on the output side of the first DC-DC converter 5 and the first electrical potential P1 potential line on the input side of the first DC-DC converter 5 can be produced.

The tenth switching unit S10 is arranged in the potential line leading from the vehicle-side direct current charging connection 4 to the battery 3 and carrying the first electrical potential P1, in this case therefore in the corresponding potential line of the second potential line pair L2, viewed from the vehicle-side direct current charging connection 4 after the branch of the bypass line BL and before the Branch of the first potential line pair L1.

The electrical system 1 has in the illustrated embodiment according to 1 and 3 until 11 also three fuses Si1 to Si3. The first fuse Si1 is in one of the potential lines, here in the potential line carrying the first potential P1, of the first potential line pair L1, in the example shown between the branch of the second potential line pair L2 and the seventh switching unit S7. The second fuse Si2 is arranged in the bypass line BL, ie between the ninth switching unit S9 and the potential line of the second potential line pair L2 carrying the first electrical potential P1. The third fuse Si3 is arranged in one of the potential lines, here in the potential line carrying the second electrical potential P2, of the fifth potential line pair L5, in the example shown between the branch to the second potential line pair L2 and the second EMC filter 8.

4 shows the first embodiment of the electrical system 1 during a driving operating state, ie while the vehicle 2 is being driven. For this purpose, the first and second switching units S1, S2 are open, the third and fourth switching units S3, S4 are closed, the fifth and sixth switching unit S5, S6 switched in the direction of the power factor correction filter 9, the seventh and eighth switching unit S7, S8 closed, the ninth switching unit S9 switched in the direction of the bypass line BL and the tenth switching unit S10 opened.

5 shows the first embodiment of the on-board electrical system 1 during an operating state of charging from a DC energy source with a high charging voltage, in particular with a charging voltage of 800 V, for example, corresponding to the nominal voltage of the battery 3. For this purpose, the first and second switching units S1, S2 are closed, the third and fourth switching unit S3, S4 opened, the fifth and sixth switching unit S5, S6 switched in the direction of the power factor correction filter 9, the seventh and eighth switching unit S7, S8 closed, the ninth switching unit S9 in the direction of the potential line of the first potential line pair L1 carrying the second electrical potential P2 switched and the tenth switching unit S10 closed.

Since the third and fourth switching units S3, S4 are open, Y capacitors, also referred to as Cy capacitors or Y capacitors, of the electric drive units 12, 13 remain discharged. These Y-capacitors therefore no longer contribute to the overall capacitance of the on-board electrical system 1 . As a result, Y-capacitors with large capacities can be installed without exceeding the permissible limit. As a result, safety limit values of the Y-capacitors or Y-capacitors of the vehicle 2 with regard to their energy content can be complied with and, in particular, EMC requirements (EMC=electromagnetic compatibility) of the vehicle 2 and in particular of the on-board electrical system 1 can be complied with. The effect of Y-capacitors in the area of electromagnetic compatibility, in particular radio interference suppression, is known to the person skilled in the art, so that no further separate explanations are required in this regard. In addition, reference is made to the relevant standards, such as Directive 2013/30/EU on electromagnetic compatibility, EM 61000 and others.

For reasons of electrical safety, a stored in all Y-capacitors electrical energy does not exceed a specified maximum value. Such a value is, for example, 0.2 J. This regularly leads to a constructive design such that the capacitance values of the Y capacitors on the vehicle side are generally selected to be smaller than is required for proper electromagnetic compatibility, in particular with regard to the electrical Components that are connected to the electrical system 1 would be necessary. Among other things, it has proven to be problematic if the vehicle 2 is to be charged by means of an AC voltage from an AC charging station, ie by means of an AC energy source. In such a case
the total capacity of Y-capacitors provided on the vehicle proves to be a hindrance, because these Y-capacitors can also cause a leakage current, which can lead to a fault being triggered on the charging station side and/or can exceed a permissible value for the leakage currents in electrical systems overall, as is the case, for example, in the standard is also specified, for example in the standard DIN EN 61800 or the like. Basically, this problem can only be solved by reducing the capacitance values of the Y-capacitors provided in the vehicle 2, whereby it should be noted, however, that this can significantly increase the cost of the filter units.

In addition, it is necessary, particularly when charging by means of a DC voltage, ie by means of a DC energy source, that the energy content of all active Y capacitors does not exceed a predetermined total energy content. A maximum value of 0.2 J is currently provided for this, which should not be exceeded. Due to the large number of electrical components of the vehicle 2, as well as an electrically contacted charging station when charging, and the increasing performance, for example
high-voltage components, the total capacity of the existing Y-capacitors is increasing, which means that the energy content stored there also increases in accordance with the increasing total capacity. It should also be noted that the energy content of the Y-capacitors is particularly critical, particularly in the high-voltage range, especially since it should be noted that the electrical energy stored in the Y-capacitors is quadratically dependent on the electrical voltage of the Y-capacitors. This makes it particularly difficult to meet the requirements with regard to the maximum energy content in relation to the respective high-voltage potential, especially in the high-voltage area. Especially in the case of vehicles 2, it has proven to be problematic to meet both requirements with regard to electromagnetic compatibility and requirements with regard to electrical safety with regard to the energy of the Y capacitors at the same time.

These problems are eliminated by the on-board electrical system 1 described here, because this on-board electrical system 1, in particular through the various switching options, allows various operating modes of the vehicle 2 to be optimized for relevant requirements. This enables the Y-capacitors of the individual functions to be designed taking into account the vehicle states to be assumed in each case.

6 shows the first embodiment of the on-board electrical system 1 during an operating state of charging at a direct current energy source, in particular a direct current charging station, with a low charging voltage, in particular with half the nominal battery voltage. For example, the nominal battery voltage is 800 V and the charging voltage is 400 V. For this purpose, the first and second switching units S1, S2 are closed, the third and fourth switching units S3, S4 are open, the fifth and sixth switching units S5, S6 are switched in the direction of the DC charging connection 4 on the vehicle side, the seventh and eighth switching unit S7, S8 closed, the ninth switching unit S9 switched in the direction of the bypass line BL and the tenth switching unit S10 opened. As a result, the charging voltage of 400 V, for example, and thus half the nominal battery voltage of 800 V, for example, is present between the potential lines of the second pair of potential lines L2 and thus also between the potential lines of the fifth pair of potential lines L5; V, the nominal battery voltage of 800 V, for example, is present between the output of the vehicle-side charging device 6 carrying the first electrical potential P1 and the potential line of the second potential line pair L2 carrying the second electrical potential P2, and between the potential lines of the first potential line pair L1 there is the electrical battery potential contacts the nominal battery voltage of 800 V, for example.

7 FIG. 1 shows the first embodiment of the on-board electrical system 1 during an operating state of charging at an AC energy source. For this purpose, the first and second switching unit S1, S2 are open, the third and fourth switching unit S3, S4 are open, the fifth and sixth switching unit S5, S6 are switched in the direction of the power factor correction filter 9, the seventh and eighth switching unit S7, S8 are closed, the ninth switching unit S9 in the direction of the potential line of the first potential line carrying the second electrical potential P2 tion pair L1 switched and opened the tenth switching unit S10.

The third and fourth switching unit S3, S4 can thus remain open during all charging processes. This enables reduced energy consumption in the additional on-board electrical system, which is designed in particular as a low-voltage on-board electrical system, since the controller, d. H. in particular control units of the electric drive units 12, 13 do not have to be operated. This is particularly advantageous for long charging operations, such as charging from an AC power source.

The following are based on the 8th until 11 Pre-charging processes for various operating states of the first embodiment of the on-board electrical system 1 and the switching positions of the switching units S1 to S10 that are present for this are described. The respective pre-charging process is carried out in particular immediately, that is to say directly in time before the start of the respective operating state. It serves in particular to pre-charge the on-board electrical system 1 designed in particular as a high-voltage on-board electrical system or at least components thereof and/or to pre-charge at least one high-voltage intermediate circuit of the on-board electrical system 1 and/or the respective charging station.

8th shows the first embodiment of the on-board electrical system 1 during pre-charging for the driving operating state. A current flow that is present in this case is shown by means of solid arrows VP. In this pre-charging process for the driving operating state, the first and second switching units S1, S2 are open, the third and fourth switching units S3, S4 are open, the fifth and sixth switching units S5, S6 are switched in the direction of the power factor correction filter 9, the seventh and eighth switching units S7, S8 is open, the ninth switching unit S9 is switched in the direction of the potential line of the first potential line pair L1 carrying the second electrical potential P2 or, as shown here, in the direction of the bypass line BL, and the tenth switching unit S10 is open. In this case, the pre-charging takes place via the second direct-current converter 17, which can be designed as a low-voltage DC-DC converter, so that the switching units S7 and S8 can be switched when the battery voltage is reached. A pre-charging circuit 19 is provided in the area of the third and fourth switching unit S3, S4 in order to allow the flow of current for pre-charging the electric drive units 12, 13 past the third and fourth switching unit S3, S4. The precharging of the electric drive units 12, 13 is therefore carried out here by means of the battery 3, in particular designed as a high-voltage battery, and the precharging of the electrical auxiliary consumers 14, 15 and the vehicle-side charging device 6 or at least one or more of their components is carried out by means of electrical energy from the low-voltage vehicle electrical system in particular trained further electrical system of the vehicle 2, in particular by means of the second DC voltage converter 17.

9 shows the first embodiment of the on-board electrical system 1 during pre-charging for the charging operating state at a direct current energy source, in particular a direct current charging station, with a high charging voltage, in particular with a charging voltage of 800 V, for example, corresponding to the nominal voltage of the battery 3. The present one is indicated by solid arrows VP Current flow shown. During this precharging process, the first and second switching units S1, S2 are open, the third and fourth switching units S3, S4 are open, the fifth and sixth switching units S5, S6 are switched in the direction of the power factor correction filter 9, the seventh and eighth switching units S7, S8 are open, the ninth switching unit S9 is switched in the direction of the bypass line BL and the tenth switching unit S10 is opened. The pre-charging of the electrical auxiliary consumers 14, 15 and the on-board charging device 6 or at least one or more of their components is carried out here by means of electrical energy from the additional on-board electrical system of the vehicle 2, which is designed in particular as a low-voltage on-board electrical system, in particular by means of the second DC-DC converter 17 battery voltage level, contactors S7 and S8 are closed.
In this case, the charging station charges the wiring harness from the charging station to the first and second switching unit S1, S2. If the battery voltage level is reached, the switching units S1, S2 and S10 are closed.

10 shows the first embodiment of the on-board electrical system 1 when using the in 2 shown as a DC-DC converter with short-circuit function designed first DC-DC converter 5 during a pre-charging for the charging operating state at a DC energy source, in particular DC charging station, with a low charging voltage, in particular with half the nominal battery voltage. For example, the nominal battery voltage is 800 V and the charging voltage is 400 V. The current flow that is present is shown by means of solid arrows VP and dashed arrows GP.

The pre-charging is done here by short-circuiting the secondary side of the isolated first DC-DC converter 5. The following describes a procedure for setting a bulk capacitance 20 to a predetermined value at the center tap of the on-board loader Preload value of 400 V, for example. The specified value corresponds in particular to the charging voltage of the DC charging station.

The first and second switching unit S1, S2 are initially open.
The third and fourth switching units S3, S4 are open and remain open.
The fifth and sixth switching units S5, S6 are switched in the direction of the DC charging connection 4 on the vehicle and remain switched in this way.
The seventh and eighth switching unit S7, S8 are initially open.
The tenth switching unit S10 is open and remains open.
The ninth switching unit S9 at the output of the first DC-DC converter 5 is switched in the direction of the bypass line BL.
The on-board charging device 6 short-circuits the secondary side of the first DC-DC converter 5 .
The second DC-DC converter 17 boosts the bulk capacitance 20 to the specified value of 400 V, for example, using electrical energy from the additional on-board electrical system designed in particular as a low-voltage vehicle electrical system, ie pre-charges the bulk capacitance 20 to the specified value of 400 V, for example. As shown, the first capacitor C1 on the primary side of the first DC voltage converter 5 is charged via the freewheeling diode of the eighth switching unit S8.
The short circuit in the secondary side of the on-board charging device 6, in particular the first DC-DC converter 5, is opened again. The second DC-DC converter 17 charges the auxiliary electrical consumers 14, 15 to the nominal battery voltage of, for example, 800 V, in particular by means of electrical energy from the additional on-board electrical system, which is designed in particular as a low-voltage vehicle electrical system.
The seventh and eighth switching unit S7, S8 are closed.
The first and second switching unit S1, S2 are closed and the charging process can be started.

11 shows the alternative to 10, i.e . H. the first embodiment of the on-board electrical system 1 when using the in 3 shown as a bidirectional DC-DC converter designed first DC-DC converter 5 during pre-charging for the charging operating state at a DC energy source, in particular DC charging station, with a low charging voltage, in particular with half the nominal battery voltage. For example, the nominal battery voltage is 800 V and the charging voltage is 400 V. The current flow that is present is shown by means of solid arrows VP and dashed arrows GP.

The pre-charging takes place here by means of the first DC-DC converter 5 designed as a bidirectional, isolated DC-DC converter. A sequence is described below for pre-charging the bulk capacitance 20 to a predetermined value of 400 V, for example, at the DC-charging station. The specified value corresponds in particular to the charging voltage of the DC charging station.

The first and second switching unit S1, S2 are initially open.
The third and fourth switching units S3, S4 are open and remain open.
The fifth and sixth switching units S5, S6 are switched in the direction of the DC charging connection 4 on the vehicle and remain switched in this way.
The seventh and eighth switching unit S7, S8 are initially open.
The tenth switching unit S10 is open and remains open.
The ninth switching unit S9 at the output of the first DC voltage converter 5 is switched in the direction of the potential line of the first potential line pair L1 carrying the second electrical potential P2.
The second DC-DC converter 17 boosts the bulk capacitance 20 to the specified value of 400 V, for example, using electrical energy from the additional on-board electrical system designed in particular as a low-voltage vehicle electrical system, ie pre-charges the bulk capacitance 20 to the specified value of 400 V, for example.
The first DC-DC converter 5 of the on-board charging unit 6, designed as a bidirectional DC-DC converter, pre-charges the primary side of the first DC-DC converter 5 and the EMC filters 7, 8.
The ninth switching unit S9 at the output of the first DC-DC converter 5 is switched in the direction of the bypass line BL. As a result, the Cy capacitances already mentioned above are recharged.
The second DC-DC converter 17 charges the auxiliary electrical consumers 14, 15 to the nominal battery voltage of, for example, 800 V, in particular by means of electrical energy from the additional on-board electrical system, which is designed in particular as a low-voltage vehicle electrical system.
The seventh and eighth switching unit S7, S8 are closed.

The first and second switching unit S1, S2 are closed and the charging process can be started.

The on-board electrical system 1, in particular the high-voltage on-board electrical system, of the solution described therefore advantageously has integrated downward charging compatibility, with the first DC voltage converter 5 advantageously being bidirectional is led. The solution described thus makes it possible to charge a vehicle 2, in particular the battery 3 of the vehicle 2, which has a high nominal battery voltage of 800 V, for example, at a direct current energy source, in particular a direct current charging station, with a low charging voltage, in particular with half the nominal battery voltage, for example 400 V. This is advantageously done by means of the charging device 6 on the vehicle that is present anyway, which was previously only provided for AC charging and is now advantageously expanded to include a charging pump function. In this case, half of the charging power flows directly from the DC charging station into the battery 3. The DC charging station provides exactly half of the required charging voltage of the battery 3.

The remaining part of the charging power is supplied to the charging device 6 of the battery 3 on the vehicle side via the first DC voltage converter 5 . The maximum charging power is therefore twice as high as the power of the first DC-DC converter 5 in the on-board charging device 6.

The first DC-DC converter 5 in the on-board charging device 6 converts the voltage by a factor of 1, i. H. an input voltage corresponds to an output voltage due to galvanic isolation to a higher potential level, so that the total is the nominal battery voltage.

The voltage divider is advantageously connected to capacitances, i. H. realized with capacitors C1, C2, which are already present as part of the on-board charging device 6 and are only newly designed. The second capacitor C2 is, for example, part of the first EMC filter 7 and stores the energy of the “upper half of the voltage”. The first capacitor C1 is, for example, part of an input intermediate circuit of the first DC-DC converter 5 and stores the "lower half" of the voltage level of the nominal battery voltage of 800 V, for example.

If the capacitances of the two capacitors C1, C2 are designed to be the same, the voltage of the direct-current charging station is exactly half the nominal battery voltage during this direct-current charging process. In addition, half of the charging power flows via the first DC-DC converter 5. The charging power can therefore be twice the component power of the first DC-DC converter 5.

Depending on the voltage level of the battery 3 and the charging station, the charging power can be further increased with the same first DC-DC converter 5 by designing the capacitance of the first capacitor C1 to be larger than the capacitance of the second capacitor C2.

Compared to other solutions, a number of additionally required components can be reduced. This is achieved through optimized integration into the on-board electrical system 1.

The solution described enables the vehicle 2, in particular the battery 3 of the vehicle 2, to be charged at a direct current energy source, in particular a direct current charging station, with a low charging voltage, in particular with half the nominal battery voltage, with the nominal battery voltage being 800 V and the charging voltage being 400 V, for example , can be realized with very little additional installation space.

The solution described advantageously uses already existing Cx capacitances of the charging device 6 on the vehicle side, in particular for the first capacitor C1 and/or for the second capacitor C2, which, for example, are merely redesigned.

The solution described enables, in particular, a reduction in the Cy capacities during DC charging of the vehicle 2, in particular the battery 3 of the vehicle 2, with a high charging voltage of, for example, 800 V, which corresponds in particular to the nominal battery voltage, since advantageously, in particular, the electric drive units 12, 13 and thus their Cy capacitances are switched off during this DC charging.

Due to the advantageous bidirectional design of the first DC-DC converter 5 according to 3 A simple pre-charge, bidirectional AC charging with an AC voltage at an AC energy source, in particular AC charging station, and bidirectional DC charging at a DC energy source, in particular DC charging station, with a low charging voltage, in particular with half the nominal battery voltage, for example with the nominal battery voltage being 800 V and the charging voltage 400 V can be realized.

The arrangement of the ten switching units S1 to S10 in the second specific embodiment of the on-board electrical system 1 is explained below 12 described.

In this second embodiment of the electrical system 1 according to 12 A first pair of potential lines L1 is provided as a connection between the various components of the vehicle electrical system 1 . It extends from the electr technical auxiliary consumers 14, 15, in particular from their distribution unit 16, to the on-board charging device 6, more precisely to between its first and second stage, the first stage here comprising the power factor correction filter 9 and the second stage comprising the first DC-DC converter 5.

A second potential line pair L2 to the battery 3 branches off from this first potential line pair L1. A third potential line pair L3 branches off from the first potential line pair L1 to the DC charging connection 4 on the vehicle side. A fourth potential line pair L4 branches off from the first potential line pair L1 to the output side of the first DC-DC converter 5, in particular to the output side of the on-board charging device 6 comprising this first DC-DC converter 5, with here after this branch in the direction of the on-board charging device 6 and before the on-board charging device 6, i.e. H. outside of the on-board charging device 6, the first EMC filter 7 is arranged. A fifth potential line pair L5 branches off from the first potential line pair L1 to the electric drive units 12, 13.

From the fourth potential line pair L4 branches, in the example shown after the first EMC filter 7, i. H. between this and the output side of the on-board charging device 6, a sixth potential line pair L6 to the second DC-DC converter 17 and thus to the on-board power supply connection 18 for the further electrical on-board power supply designed in particular as a low-voltage on-board power supply.

The first and second switching units S1, S2 are arranged in the first pair of potential lines L1 between the branch of the second pair of potential lines L2 to the battery 3 and the branch of the third pair of potential lines L3 to the DC charging connection 4 on the vehicle. In this case, the first and second switching units S1, S2 are designed together, for example, as a two-pole combined switching and safety device.

The third and fourth switching units S3, S4 are arranged in the first potential line pair L1 between the branch of the second potential line pair L2 to the battery 3 and the branch of the fifth potential line pair L5 to the electric drive units 12, 13. The third and fourth switching units S3, S4 are also designed together, for example, as a two-pole combined switching and safety device.

The fifth and sixth switching units S5, S6 are each designed as changeover switches. They are each arranged in a potential line leading to the respective electrical potential contact on the input side of the first DC voltage converter 5, in particular before the first capacitor C1, i. H. the first capacitor C1 is arranged between the fifth or sixth switching unit S5, S6 and the respective electrical potential contact on the input side of the first DC voltage converter 5 between these two potential lines. Depending on the switching position of these switching units S5, S6 designed as changeover switches, the vehicle-side DC charging connection 4 or the vehicle-side AC charging connection 11 can be electrically coupled to the input side of the first DC-DC converter 5 via the fifth and sixth switching unit S5, S6. For this purpose, the fifth and sixth switching units S5, S6 each have a switching contact electrically coupled to a potential line leading to the vehicle-side DC charging connection 4 and a switching contact electrically coupled to a potential line leading to the vehicle-side AC charging connection 11, between which by means of the respective fifth and sixth switching unit designed as a changeover switch S5, S6 can be switched. In the example shown, the switching contacts electrically coupled to the potential line leading to the DC charging connection 4 on the vehicle side are coupled to the potential lines of the first potential line pair L1; H. they form the end in the direction of the input side of the first DC-DC converter 5.

The fifth and sixth switching unit S5, S6 are arranged in particular in the charging device 6 on the vehicle. As already mentioned, in the example shown, according to 12 the power factor correction filter 9 is the first stage and the first DC/DC converter 5 is the second stage of the on-vehicle charging device 6. The fifth and sixth switching units S5, S6 are then arranged between the first and second stages of the on-vehicle charging device 6. By means of the fifth and sixth switching unit S5, S6 designed as a changeover switch, depending on the switching position, either the first stage of the on-board charging device 6, in particular its power factor correction filter 9, can be electrically coupled to the second stage of the on-board charging device 6 if the fifth and sixth switching unit S5, S6 are switched in the direction of the power factor correction filter 9, or the vehicle-side DC charging port 4 can be electrically coupled to the second stage of the vehicle-side charging device 6 when the fifth and sixth switching units S5, S6 are switched in the direction of the vehicle-side DC charging port 4.

The seventh and eighth switching units S7, S8 are in the first potential line pair L1 between the branch of the third potential line pair L3 arranged to the vehicle-side direct current charging connection 4 and the fifth and sixth switching unit S5, S6. You only need a low current carrying capacity.

The ninth switching unit S9 is designed as a changeover switch. In the embodiment according to FIG 12 before the second capacitor C2. Depending on the switching position, this ninth switching unit S9 is either switched to one terminal of the second capacitor C2, which is connected with its other terminal to the other output of the first DC-DC converter 5 carrying the first electrical potential P1, or to the potential line carrying the second electrical potential P2 of the fourth potential line pair L4.

This potential line of the fourth potential line pair L4, which carries the second electrical potential P2, is also connected to the potential line of the first potential line pair L1, which carries the second electrical potential P2.

If the ninth switching unit S9 is switched to the connection of the second capacitor C2, this second capacitor C2 is also connected via this ninth switching unit S9 and the fifth switching unit S5, with the corresponding switching position of this fifth switching unit S5, to the input of the first one carrying the first potential P1 DC converter 5 connected.

The tenth switching unit S10 is arranged in one of the potential lines, in the example shown in the potential line carrying the first potential, of the first pair of potential lines L1, in the example shown between the branch of the fourth pair of potential lines L4 and the electrical auxiliary consumers 14, 15, in particular their distribution unit 16. This tenth switching unit S10 is designed, for example, as a bidirectional semiconductor fuse, in particular with a freewheeling diode, or, for example, as a contactor or as a contactor with a fuse.

The on-board electrical system 1 has in the illustrated second embodiment according to 12 also a fuse Si1. This fuse Si1 is arranged in one of the potential lines, here in the potential line carrying the first potential P1, of the first potential line pair L1, in the example shown between the seventh and eighth switching units S7, S8 and the second EMC filter 8.

This second embodiment simplifies battery protection, since no additional protection is required for the operation of the secondary electrical consumers 14, 15.

Furthermore, in this second embodiment, the tenth switching unit S10 of the first embodiment, which is additionally provided there in one of the potential lines between the vehicle-side DC charging connection 4 and the battery 3, can be omitted.

Furthermore, in this second embodiment, a capacitor of the first EMC filter 7 is not used as the second capacitor C2, but rather an additional capacitor is provided as the second capacitor C2 on the output side of the on-board charging device 6, in particular on the output side of the first DC-DC converter 5 to produce the voltage divider between the first capacitor C1, which is in particular an intermediate circuit capacitance, and the second capacitor C2.

In this second embodiment, the electrical auxiliary consumers 14, 15 can be charged with a high charging voltage, in particular with a charging voltage corresponding to the nominal voltage of the battery 3 of, for example, 800 V, be operated electrically isolated from the DC charging station. As a result, Cy capacitances of the electrical drive units 12, 13 and the secondary electrical consumers 14, 15 do not have to be taken into account for the charging path.

Since the secondary electrical consumers 14, 15 are operated via the third and fourth switching units S3, S4 in this second embodiment, a contactor/fuse combination that has to separate the battery current can be saved.

During the driving mode, i. H. while the vehicle 2 is being driven, in this second embodiment the first and second switching units S1, S2 are open and the third, fourth and tenth switching units S3, S4, S10 are closed. The seventh and eighth switching unit S7, S8 are open, for example. The fifth and sixth switching units S5, S6 are connected, for example, in the direction of the DC charging connection 4 on the vehicle. The ninth switching unit S9 is, for example, connected to the second capacitor C2, i. H. on its connection.

During the charging operating state at a direct current energy source, in particular a direct current charging station, with a high charging voltage, in particular with one of the rated voltage the charging voltage corresponding to the battery 3 of, for example, 800 V, the first and second switching units S1, S2 are closed. The third and fourth switching unit S3, S4 are advantageously open. For example, the seventh and eighth switching unit S7, S8 are closed, the fifth and sixth switching unit S5, S6 are switched in the direction of the vehicle-side DC charging connection 4, the ninth switching unit S9 is connected to the potential line of the fourth potential line pair L4, which carries the second electrical potential P2, and the tenth switching unit S10 closed. As already mentioned above, the electrical auxiliary consumers 14, 15 can be operated electrically isolated from the DC charging station during this charging process by means of the first DC voltage converter 5 of the on-board charging device 6. As a result, Cy capacitances of the electrical drive units 12, 13 and the secondary electrical consumers 14, 15 do not have to be taken into account for the charging path.

During the operating state of charging at a direct current energy source, in particular a direct current charging station, with a low charging voltage, in particular with half the nominal battery voltage, with the nominal battery voltage being 800 V and the charging voltage being 400 V, for example, the first and second switching units S1, S2 are open, the third and fourth switching unit S3, S4 closed, the fifth and sixth switching unit S5, S6 switched in the direction of the vehicle-side DC charging connection 4, the seventh and eighth switching unit S7, S8 closed, the ninth switching unit S9 to the second capacitor C2, d. H. connected to its connection, and the tenth switching unit S10 is advantageously closed, in order thereby to also supply the secondary electrical consumers 14, 15.

During the operating state of charging at an AC energy source, in particular an AC charging station, the first and second switching units S1, S2 are open, the third and fourth switching units S3, S4 are closed, the fifth and sixth switching units S5, S6 in the direction of the power factor correction filter 9 and thus in the direction of the AC charging connection 11 on the vehicle side is switched, the seventh and eighth switching unit S7, S8 is opened, for example, the ninth switching unit S9 is connected to the potential line of the fourth potential line pair L4 that carries the second electrical potential P2, and the tenth switching unit S10 is advantageously closed, in order to also switch the electrical auxiliary consumers 14, 15 to supply.

Reference List

1

electrical system

2

vehicle

3

battery

4

DC charging port

5

first DC converter

6

loading device

7

first EMC filter

8th

second EMC filter

9

power factor correction filter

10

AC EMC Filter

11

AC charging port

12, 13

drive unit

14, 15

secondary consumers

16

distribution unit

17

second DC converter

18

on-board power supply

19

precharge circuit

20

bulk capacity

BL

bypass line

C1

first capacitor

C2

second condenser

D

diode

gp

dashed arrow

HL

semiconductor switch

L1 to L6

potential wire pair

S1 to S10

switching unit

Si1 to Si3

fuse

VP

solid arrow

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102017213682 A1 [0002]

Claims (10)

On-board electrical system (1) for a vehicle (2), comprising a battery (3) with two electrical battery potential contacts and a vehicle-side DC charging connection (4) with two electrical charging potential contacts, characterized in that - a DC-DC converter (5) is provided, - the first electrical battery potential contact can be or is electrically coupled to a first electrical potential contact on an output side of the DC-DC converter (5), - the second electrical battery potential contact can be electrically coupled or is coupled to the second electrical charging potential contact, - the respective electrical charging potential contact has a respective electrical potential contact to an input side of the DC-DC converter (5) can be electrically coupled or is coupled, - a second electrical potential contact on the output side of the DC voltage converter (5) with the first electrical potential contact on the input side of the DC voltage voltage converter (5) can be or is electrically coupled, - the electrical potential contacts on the input side of the DC-DC converter (5) are each electrically coupled with an electrical connection contact of a first capacitor (C1), and - the electrical potential contacts on the output side of the DC-DC converter (5) each with an electrical connection contact of a second capacitor (C2) can be electrically coupled or are coupled. Electrical system (1) after claim 1 , characterized in that the DC-DC converter (5) is part of an on-board charging device (6) for electrically charging the battery (3) by means of an AC power source external to the vehicle. Electrical system (1) after claim 2 , characterized in that the first capacitor (C1) and / or the second capacitor (C2) is a component of the vehicle-side charging device (6) for electrically charging the battery (3) by means of an external vehicle AC power source are / is. Vehicle electrical system (1) according to one of the preceding claims, characterized in that the second capacitor (C2) is part of an EMC filter (7). Vehicle electrical system (1) according to one of the preceding claims, characterized in that the first capacitor (C1) and the second capacitor (C2) have the same capacitance or the first capacitor (C1) has a greater capacitance than the second capacitor (C2) . Vehicle electrical system (1) according to one of the preceding claims, characterized in that the DC voltage converter (5) is designed as a bidirectional DC voltage converter or as a DC voltage converter with a short-circuit function. Vehicle electrical system (1) according to one of the preceding claims, characterized in that the first electrical battery potential contact can be or is electrically coupled to the first electrical charging potential contact. Vehicle electrical system (1) according to one of the preceding claims, characterized in that the second electrical potential contact on the output side of the DC voltage converter (5) can be or is electrically coupled to the second electrical battery potential contact. Vehicle (2) comprising an on-board electrical system (1) according to one of the preceding claims. Method for operating an on-board electrical system (1) according to one of Claims 1 until 8th , characterized in that - for electrical charging of the battery (3) by means of an external vehicle direct current energy source connected to the vehicle-side direct current charging connection (4), the charging voltage of which is lower than a nominal battery voltage of the battery (3), the first electrical battery potential contact with the first electrical potential contact on the output side of the DC-DC converter (5) is electrically coupled, the second electric battery potential contact is electrically coupled to the second electric charging potential contact, the respective electric charging potential contact is electrically coupled to the respective electric potential contact on the input side of the DC-DC converter (5), and the second electric potential contact is connected to the output side of the DC-DC converter (5) is electrically coupled to the first electrical potential contact of the input side of the DC-DC converter (5), and / or - for electrically charging the Batt Series (3) by means of a vehicle-external direct current energy source connected to the direct current charging connection (4) on the vehicle, the charging voltage of which is equal to or greater than the nominal battery voltage of the battery (3), the first electrical battery potential contact is electrically coupled to the first electrical charging potential contact and the second electrical battery potential contact is electrically coupled to it is electrically coupled to the second electrical charge potential contact, and/or - for electrical charging of the battery (3) by means of an AC energy source external to the vehicle, the first electrical battery potential contact is electrically coupled to the first electrical potential contact on the output side of the DC-DC converter (5) and the second electrical potential contact is electrically coupled to the output side of the DC voltage converter (5) is electrically coupled to the second electrical battery potential contact.

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