DE102024001258B4 - Method for operating a vehicle electrical system and vehicle electrical system - Google Patents

Abstract

The invention relates to a method for operating a vehicle electrical system arrangement (1) for a vehicle.
According to the invention, the on-board electrical system (1) is operated in a normal operating mode as long as a DC-DC converter (5) can supply all activated low-voltage consumers (7.1 to 7.n) of a low-voltage on-board electrical system (6) with electrical energy, wherein in normal operating mode a charging switch (10) and a discharging switch (11) are closed between the low-voltage on-board electrical system (6) and battery cells (9) of a low-voltage battery (8) and the DC-DC converter (5) regulates an on-board voltage (U2) such that it is higher than a predetermined minimum on-board voltage (U_min) and higher than or equal to a battery voltage (U1) and is at most as high as a predetermined maximum battery voltage (U_bat_max), wherein if an overload of the DC-DC converter (5) occurs in normal operating mode, the system switches to an operating mode with higher DC-DC converter power by opening the charging switch (10) and the DC voltage converter (5) sets or regulates the on-board voltage (U2) to a voltage value (Uh) that is higher than the specified maximum battery voltage (U_bat_max) and is at most as high as a specified maximum on-board voltage (U_max).
The invention further relates to an on-board electrical system arrangement (1) for a vehicle that can be operated by means of the method.

Description

The invention relates to a method for operating a vehicle electrical system arrangement according to the features of the preamble of claim 1 and a vehicle electrical system arrangement.

From the state of the art, as in the DE 10 2015 108 116 A1 A vehicle system with accumulator amplification and bypass control is described. The vehicle system has a DC/DC converter bus that is adapted to operate at a first voltage setpoint. The vehicle system further has a low-voltage accumulator bus that is adapted to operate at a second voltage setpoint that differs from the first voltage setpoint.

In the DE 10 2021 128 806 A1 This document describes an electrical system for a motor vehicle and a method for providing energy within that system. The electrical system comprises a rechargeable low-voltage battery, which can be electrically connected to a load via a first switching device, a capacitor, which is electrically connected in parallel to the load, and a first switching device that has a first operating mode and a second operating mode. In the first operating mode, the rechargeable low-voltage battery is electrically connected to both the load and the capacitor to supply them with a voltage. In the second operating mode, the rechargeable low-voltage battery is electrically disconnected from both the load and the capacitor. The first switching device is configured to detect a current flowing through it and to trigger a switch from the first to the second operating mode when the detected current exceeds a predetermined value.

From the US 2021 / 0 354 577 A1 A DC-DC converter control system is known. A method for controlling the output voltage of a DC-DC converter includes sensing a voltage from the bus of an electric vehicle, increasing a command voltage signal from the sensed voltage to a nominal voltage during a first period, increasing the command voltage signal from the nominal voltage to a desired voltage during a second period that is longer than the first period, and generating a voltage output based on the command voltage signal.

In the DE 10 2011 083 010 A1 A control device for a DC-DC converter of an electric drive system and a method for operating a DC-DC converter are described. The control device for driving the DC-DC converter comprises a voltage control device designed to regulate the output voltage of the DC-DC converter as its controlled variable, and a current control device designed to regulate the output current of the DC-DC converter as its controlled variable. The control device is designed to receive an operating selection signal and, depending on the operating selection signal, to adjust the voltage control device such that it limits the output voltage of the DC-DC converter to a predetermined constant maximum voltage, and to adjust the current control device such that the difference between a predetermined target output voltage and the output voltage of the DC-DC converter is used as the control deviation.

From the US 2021 / 0 031 748 A1 A vehicle control device is known, comprising a controller that switches a vehicle between an HEV driving mode and an EV driving mode. When the output current of a DC-DC converter becomes equal to or higher than a threshold value, the controller reduces the output current by decreasing the output voltage of the DC-DC converter through power regulation. The controller switches between a normal setting, in which the power regulation threshold is set to a reference threshold, and a boost setting, in which the threshold is set to a boost threshold higher than the reference threshold. The controller prevents the boost setting when the boosting power margin becomes equal to or lower than a first power margin value in the HEV driving mode, and when the boosting power margin becomes equal to or lower than a second power margin value in the EV driving mode.

The invention is based on the objective of providing a method for operating a vehicle electrical system arrangement that is improved compared to the prior art, and a vehicle electrical system arrangement that is improved compared to the prior art.

The problem is solved according to the invention by a method for operating a vehicle electrical system arrangement with the features of claim 1 and a vehicle electrical system arrangement with the features of claim 5.

Advantageous embodiments of the invention are the subject of the dependent claims.

In a method for operating a vehicle electrical system, wherein the vehicle electrical system comprises a high-voltage electrical system and a low-voltage electrical system connected to the high-voltage electrical system via a DC-DC converter, with low-voltage electrical consumers, and wherein battery cells of a low-voltage battery can be electrically coupled or connected to the low-voltage electrical system via a switching unit comprising a charging switch for charging the low-voltage battery via the DC-DC converter and a discharge switch for supplying electrical energy to the low-voltage electrical consumers via the low-voltage battery, the invention provides that the vehicle electrical system is operated in a normal operating mode as long as the DC-DC converter can supply all activated low-voltage electrical consumers with electrical energy.

In this normal operating mode, the charging and discharging switches are closed, and the DC-DC converter regulates the on-board voltage in the low-voltage electrical system such that the on-board voltage is higher than a predefined minimum voltage of the low-voltage electrical system and higher than or equal to the battery voltage of the low-voltage battery, and at most equal to a predefined maximum voltage of the low-voltage battery. The DC-DC converter only regulates the on-board voltage of the low-voltage electrical system so that it equals the battery voltage of the low-voltage battery if this battery voltage is equal to the predefined maximum voltage of the low-voltage battery. In this case, the DC-DC converter thus regulates the on-board voltage of the low-voltage electrical system so that the on-board voltage of the low-voltage electrical system is equal to the battery voltage of the low-voltage battery and equal to the predefined maximum voltage of the low-voltage battery.

The DC/DC converter regulates the on-board voltage in the low-voltage on-board network, in particular so that the battery voltage of the low-voltage battery is kept within a specified nominal voltage range.

If the DC-DC converter is overloaded during normal operation, it switches to a higher DC-DC converter operating mode, also known as PowerBoost mode. In this mode, the charging switch opens, and the DC-DC converter adjusts or regulates the low-voltage electrical system voltage to a value higher than the preset maximum battery voltage and no higher than the preset maximum voltage of the low-voltage electrical system. The discharge switch remains closed. This allows the low-voltage battery to continue buffering dynamic electrical loads or, in the event of a fault, such as a DC-DC converter failure, to continue supplying power to the low-voltage electrical system. Opening the charging switch prevents the low-voltage battery from being charged with a voltage higher than its preset maximum voltage. The low-voltage battery is then no longer charged.

For example, it is provided that the occurrence of the overload of the DC-DC converter is detected by a control and/or regulation unit and/or that the charging switch and/or the discharging switch is actuated by the control and/or regulation unit and/or that the DC-DC converter is controlled and/or regulated by the control and/or regulation unit.

The specified minimum and maximum on-board voltages are determined, in particular, by the voltage limits of the low-voltage electrical consumers. The specified maximum on-board voltage is higher than the specified maximum battery voltage.

It is specifically designed that the system switches back from the operating mode with higher DC-DC converter power to the normal operating mode when the DC-DC converter is no longer fully loaded and the operating mode with higher DC-DC converter power is no longer required, and/or when the state of charge of the low-voltage battery falls below a predetermined minimum state of charge threshold. This means that the charging switch closes again, the discharging switch remains closed, and the DC-DC converter regulates the on-board voltage in the low-voltage electrical system so that the on-board voltage is higher than the predetermined minimum on-board voltage of the low-voltage electrical system and is higher than or equal to the battery voltage of the low-voltage battery, and is at most as high as the predetermined maximum battery voltage of the low-voltage battery.

An on-board electrical system arrangement according to the invention for a vehicle can be operated using this method. It is particularly provided that the on-board electrical system arrangement comprises the high-voltage on-board electrical system, the DC-DC converter, the low-voltage on-board electrical system connected to the high-voltage on-board electrical system via the DC-DC converter and including the low-voltage electrical consumers, the low-voltage battery, and the switching unit with the charging switch for charging the low-voltage battery via the DC-DC converter. The unit includes a switch and a discharge switch for supplying electrical energy to low-voltage electrical consumers via the low-voltage battery. The battery cells of the low-voltage battery can be electrically connected to, or are already connected to, the low-voltage vehicle electrical system via the switching unit.

The electrical system can be operated in normal mode as long as the DC-DC converter can supply all activated low-voltage electrical consumers with electrical energy. In normal mode, the charging and discharging switches are closed, and the DC-DC converter regulates the on-board voltage in the low-voltage system such that the on-board voltage is higher than the specified minimum voltage of the low-voltage system and higher than or equal to the battery voltage of the low-voltage battery, and at most as high as the specified maximum voltage of the low-voltage battery. The DC-DC converter only regulates the on-board voltage of the low-voltage system so that it is equal to the battery voltage of the low-voltage battery if this battery voltage is equal to the specified maximum voltage of the low-voltage battery. In this case, the DC/DC converter regulates the on-board voltage of the low-voltage on-board network so that the on-board voltage of the low-voltage on-board network is equal to the battery voltage of the low-voltage battery and equal to the specified maximum battery voltage of the low-voltage battery.

The DC/DC converter regulates the on-board voltage in the low-voltage on-board network, in particular so that the battery voltage of the low-voltage battery is kept within a specified nominal voltage range.

If the DC-DC converter becomes overloaded during normal operation, it can be switched to a higher DC-DC converter operating mode, also known as PowerBoost mode. This is achieved by opening the charging switch and adjusting or regulating the on-board voltage in the low-voltage electrical system to a voltage higher than the specified maximum battery voltage and not exceeding the specified maximum voltage of the low-voltage electrical system. The discharge switch remains closed during this process. This allows the low-voltage battery to continue buffering dynamic electrical loads or, in the event of a fault, such as a DC-DC converter failure, to continue supplying power to the low-voltage electrical system. Opening the charging switch prevents the low-voltage battery from being charged at a voltage higher than its specified maximum voltage. The low-voltage battery will then no longer be charged.

The on-board electrical system includes, in particular, the control and/or regulation unit, which is designed to detect the occurrence of an overload of the DC-DC converter and/or to actuate the charging switch and/or the discharging switch and/or to control and/or regulate the DC-DC converter.

The control and/or regulation unit is, for example, a component of an on-board network management system, the DC-DC converter, the low-voltage battery, or another component, in particular a software component, of the vehicle.

The specified minimum and maximum on-board voltages are determined primarily by the voltage limits of the low-voltage electrical consumers. The specified maximum on-board voltage is higher than the specified maximum battery voltage.

The on-board electrical system is specifically designed to switch back from the operating mode with higher DC power to the normal operating mode when the DC power converter is no longer fully utilized and the operating mode with higher DC power is no longer required, and/or when the state of charge of the low-voltage battery falls below the specified minimum state of charge limit.

In one possible embodiment, the switching unit is arranged in the low-voltage battery, in particular within a battery housing of the low-voltage battery. In another possible embodiment, the switching unit is arranged outside the low-voltage battery. For example, it is then arranged in a power distribution unit or designed as such a power distribution unit.
A vehicle according to the invention has this on-board electrical system arrangement.

The described solution enables an increase in the power output of the low-voltage electrical system. This solves the problem that, previously, in certain situations, only some of the low-voltage electrical consumers, especially only some of the comfort consumers in the low-voltage electrical system, could be supplied with electrical energy by the DC-DC converter, as the electrical output of the DC-DC converter was insufficient in these situations. To solve this problem, the electrical output of the DC-DC converter could be increased. The existing transformer could be enlarged or an additional DC-DC converter installed. However, both solutions would require more space, increase weight, and raise costs. Furthermore, with high-power DC-DC converters, the current cannot be arbitrarily high to avoid excessive wiring costs, particularly those resulting from large cross-sections.

Another option would be to accept functional limitations, particularly regarding the vehicle's comfort features, in the event of a power supply shortage. However, this would entail a corresponding reduction in comfort.

The solution described here solves this problem while simultaneously avoiding the disadvantages of other possible solutions. As described above, this is achieved by switching to a higher DC-DC converter operating mode when an overload occurs during normal operation. In this mode, the charging switch opens, and the DC-DC converter adjusts or regulates the on-board voltage in the low-voltage electrical system to a voltage value that is higher than the specified maximum battery voltage and at most equal to the specified maximum voltage of the low-voltage electrical system.

By opening the charging switch in the operating mode with higher DC-DC converter power, the DC-DC converter can provide a higher voltage, independent of the low-voltage battery. This is because, with the charging switch open, the DC-DC converter's voltage setting is no longer dependent on the battery voltage, and in particular, the battery's maximum voltage does not need to be maintained. Due to the higher on-board voltage, more power is available to the low-voltage electrical system at the same current, allowing more low-voltage electrical consumers to be activated. This means, for example, that a vehicle user can activate more electrical functions simultaneously.

The higher on-board voltage is made possible because the low-voltage electrical consumers can be operated within a voltage range from the specified minimum on-board voltage to the specified maximum on-board voltage, where the specified maximum on-board voltage is higher than the specified maximum voltage of the low-voltage battery. This means that previously, the voltage setting of the DC-DC converter for the low-voltage on-board system was limited by the specified maximum battery voltage. By opening the charging switch, the DC-DC converter can now set the higher voltage value, as opening the charging switch prevents the low-voltage battery from being subjected to this higher voltage, which is higher than the specified maximum battery voltage and at most equal to the specified maximum on-board voltage, and which could damage the low-voltage battery.

The discharge switch remains closed in the operating mode with higher DC-DC converter power, allowing the low-voltage battery to continue buffering dynamic electrical loads or, in the event of a fault, such as a DC-DC converter failure, to continue supplying power to the low-voltage electrical system. If the low-voltage battery is deeply discharged or there is no overload in the low-voltage electrical system, the operating mode with higher DC-DC converter power can be deactivated and the discharge switch closed again.

For example, the charging and discharging switches are already integrated into a conventional low-voltage battery, so no significant additional space or weight is required. Alternatively, low-voltage batteries without integrated charging and discharging switches can also be used for the described solution. This can be achieved, for example, by integrating the switching unit with the charging and discharging switches into a power distribution unit or another intermediate unit connected between the low-voltage battery and the vehicle's low-voltage electrical system.

The described solution allows the vehicle user to activate more comfort functions in the low-voltage electrical system, thus avoiding any reduction in comfort. This solution eliminates the need for a larger or additional DC-DC converter, resulting in significant savings in cost, weight, and installation space.

The switching unit is designed such that the low-voltage battery can only be charged via the closed charging switch and only discharged via the closed discharge switch; that is, the corresponding current flow direction via the charging switch and the discharge switch is ensured. This can be achieved, for example, by designing the charging switch and/or the discharge switch as a semiconductor switch and/or by using a semiconductor, in particular a diode, between the charging switch and the low-voltage electrical system and/or between the battery cells and the charging switch and/or by using a semiconductor, in particular a diode, between the discharge switch and the low-voltage electrical system. and/or between the battery cells and the discharge switch.

The voltage value, which is higher than the specified maximum battery voltage and at most as high as the specified maximum voltage of the low-voltage electrical system, can be a fixed value or, for example, be set depending on the situation. For instance, this voltage value is set to be higher than the specified maximum battery voltage but lower than the specified maximum voltage of the low-voltage electrical system. This provides a safety margin, particularly a small one, which prevents the low-voltage electrical system from failing in the event of overvoltage phenomena. The voltage value is thus set lower than the specified maximum voltage of the low-voltage electrical system to ensure this safety margin.

In the context of this application, the term "high voltage" is understood to mean, in particular, a voltage of 48 V or higher. Accordingly, a high-voltage electrical system is understood to mean, in particular, an electrical system with a nominal voltage, especially a high-voltage electrical system, of 48 V or higher, for example, 400 V or 800 V. Similarly, a high-voltage battery in the context of this application is understood to mean, in particular, a battery with a nominal voltage of 48 V or higher, for example, 400 V or 800 V. The nominal voltage, especially the high-voltage electrical system, of the high-voltage electrical system, and thus the nominal voltage of the high-voltage battery in the context of this application, can therefore also be a higher low-voltage voltage. It is, in particular, higher than the electrical system voltage in the low-voltage electrical system and, in particular, at least as high as the specified maximum electrical system voltage of the low-voltage electrical system, and, in particular, higher than the specified maximum electrical system voltage of the low-voltage electrical system.

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

• 1 schematisch eine aus dem Stand der Technik bekannte Ausführungsform einer Bordnetzanordnung für ein Fahrzeug,
• 2 schematisch eine erfindungsgemäße Ausführungsform einer Bordnetzanordnung für ein Fahrzeug,
• 3 schematisch eine weitere erfindungsgemäße Ausführungsform einer Bordnetzanordnung für ein Fahrzeug,
• 4 schematisch einen Betrieb der erfindungsgemäßen Bordnetzanordnung in einem Normalbetriebsmodus, und
• 5 schematisch einen Betrieb der erfindungsgemäßen Bordnetzanordnung in einem Betriebsmodus mit höherer Gleichspannungswandlerleistung.

This shows:

• 1 schematically, an embodiment of a vehicle electrical system arrangement known from the prior art,
• 2 schematically a model of an embodiment of a vehicle electrical system arrangement according to the invention,
• 3 schematically a further embodiment of a vehicle electrical system arrangement according to the invention,
• 4 schematically depicts the operation of the on-board network arrangement according to the invention in a normal operating mode, and
• 5 schematically, an operation of the on-board network arrangement according to the invention in an operating mode with higher DC voltage converter power.

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

Based on the 1 to 5 The following describes a vehicle electrical system arrangement 1 and a method for its operation. 1 an embodiment of the on-board network arrangement 1 known from the prior art, which 2 and 3 Two exemplary embodiments of the invention are shown and the 4 and 5 Two operating modes of the on-board power supply arrangement 1 are shown as examples, using the example in 2 The first embodiment of the invention is illustrated. These operating modes also apply in the same way to the embodiment shown in 3 second embodiment of the on-board network arrangement according to the invention 1.

Each of the illustrated embodiments of the electrical system arrangement 1 comprises a high-voltage electrical system 2, a high-voltage battery 4 electrically connected or connectable to the high-voltage electrical system 2, in particular via contactors 3, a DC/DC converter 5, also referred to as a DC/DC converter, a low-voltage electrical system 6 connected to the high-voltage electrical system 2 via the DC/DC converter 5, with low-voltage electrical loads 7.1 to 7.n, and a low-voltage battery 8 with battery cells 9 connected electrically in series and/or parallel. The high-voltage electrical system 2, the high-voltage battery 4, and the low-voltage electrical loads 7.1 to 7.n are in the 2 to 5 Not shown, but also present in these embodiments of the on-board electrical system arrangement 1. The low-voltage electrical consumers 7.1 to 7.n include, for example, an electric steering system, an electric braking system, at least one seat heater and/or other low-voltage electrical consumers, in particular comfort consumers.

The high-voltage electrical system 2, for example, has a nominal high-voltage electrical system voltage of 48V or higher, for example 800V or 400V.

The low-voltage electrical system 6, for example, has a nominal low-voltage electrical system voltage of 12 V. The actual electrical system voltage supplied by the DC-DC converter 5 is... However, U2 of the low-voltage electrical system 6 can deviate downwards or upwards from this low-voltage electrical system nominal voltage, i.e. be smaller or larger than the low-voltage electrical system nominal voltage.

The DC/DC converter 5 converts the on-board voltage of the high-voltage on-board network 2, in particular from the high-voltage battery 4, into the on-board voltage U2 of the low-voltage on-board network 6.

The DC-DC converter 5 is primarily responsible for supplying a static electrical load in the low-voltage electrical system 6 and also for charging the low-voltage battery 8, more precisely its battery cells 9. The low-voltage battery 8 primarily supplies only dynamic loads, such as short-term high current demands from the electric power steering or the electric braking system, and also ensures that, in cases where the DC-DC converter 5 cannot guarantee an electrical supply, at least all safety-relevant low-voltage electrical consumers 7.1 to 7.n continue to be supplied with electrical energy. This function is specifically assigned an ASIL level (Automotive Safety Integrity Level), i.e., a safety requirement level for safety-related systems in motor vehicles specified by ISO 26262, for reasons of functional safety. One possible reason that could lead to the failure of the DC-DC converter 5 is, for example, a high-voltage safety problem, which leads to the opening of the contactors 3 in the high-voltage battery 4 and thus to the immediate failure of the DC-DC converter 5.

The following describes an operating mode for the system known from the prior art and exemplified in 1 The embodiment of the on-board power supply arrangement 1 shown is described. This operating mode corresponds, at least with regard to voltage regulation of the on-board power supply voltage U2 of the low-voltage on-board power supply 6, to a normal operating mode for the embodiments of the on-board power supply arrangement 1 according to the invention, which are described below. 2 and 3 These are examples. 4 This normal operating mode is shown by way of example in the embodiment of the on-board power supply arrangement 1 according to 2 As mentioned, this normal operating mode also applies equally to the in 3 Exemplary embodiment of the on-board network arrangement 1.

To prevent the low-voltage battery 8 from being discharged during vehicle operation or to keep it within its nominal voltage range, the DC/DC converter 5 provides a suitable voltage, which ensures that in static load operation no current flows from the low-voltage battery 8, but rather the low-voltage battery 8 is charged and all low-voltage electrical consumers 7.1 to 7.n are supplied.

Depending on the state of charge of the low-voltage battery 8 and other factors, the low-voltage battery 8 supplies a battery voltage U1 as a DC voltage. In the low-voltage electrical system 6, the voltage must remain between a predetermined minimum electrical system voltage U_min and a predetermined maximum electrical system voltage U_max during static load operation so that all low-voltage electrical consumers 7.1 to 7.n in the low-voltage electrical system 6 can be supplied. The predetermined minimum electrical system voltage U_min and the predetermined maximum electrical system voltage U_max are, or are, specified in particular depending on predetermined voltage limits of the low-voltage electrical consumers 7.1 to 7.n. This specification is made, for example, by relevant standards.

The DC-DC converter 5 regulates the on-board voltage U2 of the low-voltage on-board network 6 so that the voltage range limited by the specified minimum on-board voltage U_min and the specified maximum on-board voltage U_max is maintained, and is guided by the battery voltage U1. By consistently maintaining a slightly higher voltage compared to the battery voltage U1, it is ensured that the low-voltage battery 8 is not discharged during static load operation and can be kept at a specified state of charge. However, a specified maximum battery voltage U_bat_max of the low-voltage battery 8 must not be exceeded to prevent overcharging. This specified maximum battery voltage U_bat_max is lower than the specified maximum on-board voltage U_max.

In this operating mode, which, at least with regard to the voltage regulation of the on-board voltage U2 of the low-voltage on-board network 6, corresponds to the normal operating mode for the embodiments of the on-board network arrangement 1 according to the invention, the DC-DC converter 5 regulates the on-board voltage U2 in the low-voltage on-board network 6 such that the on-board voltage U2 is higher than the predetermined minimum on-board voltage U_min of the low-voltage on-board network 6 and is higher than or equal to the battery voltage U1 of the low-voltage battery 8, and is at most as high as the predetermined maximum battery voltage U_bat_max of the low-voltage battery 8. The DC-DC converter 5 regulates the on-board voltage U2 of the low-voltage on-board network 6 so that it is equal to the battery voltage U1 of the low-voltage battery 8 only if the battery voltage U1 of the low-voltage battery 8 is equal to the predetermined maximum battery voltage U_bat_max of the low-voltage battery 8. The given maximum battery voltage U_bat_max of the low-voltage battery 8 is used. In this case, the DC-DC converter 5 regulates the on-board voltage U2 of the low-voltage on-board network 6 so that the on-board voltage U2 of the low-voltage on-board network 6 is equal to the battery voltage U1 of the low-voltage battery 8 and equal to the given maximum battery voltage U_bat_max of the low-voltage battery 8.

Therefore: $$\text{U}2>\text{U}\_\text{min}$$ and $$\text{U}2\ge \text{U}1$$ and $$\text{U}2\le \text{U}\_\text{bat}\_\text{max}$$ where $$\text{U}2=\text{U}1\text{ und U}2=\text{U}\_\text{bat}\_\text{max}$$ only applies if $$\text{U}1=\text{U}\_\text{bat}\_\text{max}$$

Overcharging the low-voltage battery 8 can lead to a reduction in its service life, poses a risk of battery damage and represents a safety risk for vehicle occupants, as there is, for example, the risk of a so-called thermal runaway in a low-voltage battery 8 designed as a lithium battery.

The described operating mode is problematic in certain situations where the power output of the DC-DC converter 5 is insufficient to supply all low-voltage electrical consumers 7.1 to 7.n in the low-voltage on-board network 6 with electrical energy, so that only a portion of the low-voltage electrical consumers 7.1 to 7.n, in particular the comfort consumers, can be supplied using this operating mode.

To solve this problem, the electrical power of the DC-DC converter 5 could be increased, or an additional DC-DC converter could be installed. However, both solutions would require more installation space, increase weight, and raise costs. Furthermore, with high-power DC-DC converters 5, the current cannot be arbitrarily high to avoid excessive costs in the wiring harness, particularly those caused by large cross-sections.

Another option would be to accept functional limitations, particularly regarding the vehicle's comfort features, in the event of a power supply shortage. However, this would entail a corresponding reduction in comfort.

The solution described below solves this problem while simultaneously avoiding the disadvantages of the other solutions mentioned above.

This is achieved by, in the event of an overload of the DC-DC converter 5 in the 4 normal operating mode shown in a 5 The operating mode shown, with higher DC-DC converter power, is switched. This operating mode with higher DC-DC converter power is also referred to as PowerBoost mode.

The solution described here allows for savings in installation space, weight and costs, as well as an increase in usable comfort functions.

The solution described here is based on the understanding that a higher on-board voltage U2, within the voltage range from the specified minimum on-board voltage U_min to the specified maximum on-board voltage U_max of the low-voltage on-board network 6, allows more low-voltage electrical consumers 7.1 to 7.n, in particular more comfort consumers, to be supplied, since the maximum available power that the DC-DC converter 5 can deliver is increased at the same current.

Since, in the previous operating mode of the on-board network arrangement 1 according to 1 and also in the normal operating mode of the embodiments of the on-board network arrangement 1 according to the 2 and 3 Since the on-board voltage U2 in the low-voltage on-board network 6 depends on the battery voltage U1 of the low-voltage battery 8 and cannot be chosen arbitrarily, a change in the design of the on-board network arrangement 1 and, in the case of overload of the DC voltage converter 5, a change in the operating mode are required.

The modification of the design of the on-board electrical system 1 concerns the provision of a charging switch 10 for charging the low-voltage battery 8, more precisely its battery cells 9, via the DC-DC converter 5, and a discharge switch 11 for supplying electrical energy to the low-voltage consumers 7.1 to 7.n from the low-voltage battery 8. Thus, a switching unit 12 comprising the charging switch 10 and the discharge switch 11 serves as the input circuit for the low-voltage battery 8. provided, via which the battery cells 9 of the low-voltage battery 8 can be electrically connected or coupled to the low-voltage on-board network 6.

In the embodiment according to 2 The switching unit 12 is arranged in the low-voltage battery 8, in particular within a battery housing of the low-voltage battery 8. In the embodiment according to 3 The switching unit 12 is arranged outside the low-voltage battery 8, between the low-voltage electrical system 6 and the low-voltage battery 8. For example, it is then arranged in a power distribution unit 13 or designed as such a power distribution unit 13. In both embodiments, the switching unit 12 is arranged between the low-voltage electrical system 6 and the battery cells 9 of the low-voltage battery 8.

The change in operating mode in the event of an overload of the DC-DC converter 5 concerns the switching already mentioned above when an overload of the DC-DC converter 5 occurs in the 4 normal operating mode shown in the 5 The operating mode shown uses higher DC-DC converter power.

• Die Bordnetzanordnung 1 wird im in 4 gezeigten Normalbetriebsmodus betrieben, solange der Gleichspannungswandler 5 alle aktivierten Niedervoltverbraucher 7.1 bis 7.n mit elektrischer Energie versorgen kann. In diesem Normalbetriebsmodus sind der Ladeschalter 10 und der Entladeschalter 11 geschlossen und der Gleichspannungswandler 5 regelt die Bordnetzspannung U2 im Niedervoltbordnetz 6 wie oben beschrieben, d. h. insbesondere derart, dass die Bordnetzspannung U2 höher ist als die vorgegebene Bordnetzmindestspannung U_min des Niedervoltbordnetzes 6 und höher ist als die Batteriespannung U1 der Niedervoltbatterie 8 oder gleich dieser Batteriespannung U1 ist und maximal so hoch ist wie die vorgegebene Batteriemaximalspannung U_bat_max der Niedervoltbatterie 8.

The operating mode of the on-board power supply arrangement 1 according to the 2 and 3 is therefore as follows:

• The on-board network arrangement 1 is shown in the 4 The normal operating mode shown is operated as long as the DC-DC converter 5 can supply all activated low-voltage consumers 7.1 to 7.n with electrical energy. In this normal operating mode, the charging switch 10 and the discharging switch 11 are closed, and the DC-DC converter 5 regulates the on-board voltage U2 in the low-voltage on-board network 6 as described above, i.e., in particular, such that the on-board voltage U2 is higher than the specified minimum on-board voltage U_min of the low-voltage on-board network 6 and is higher than or equal to the battery voltage U1 of the low-voltage battery 8 and is at most as high as the specified maximum battery voltage U_bat_max of the low-voltage battery 8.

The DC-DC converter 5 regulates the on-board voltage U2 of the low-voltage on-board network 6 so that it is equal to the battery voltage U1 of the low-voltage battery 8 only if the battery voltage U1 of the low-voltage battery 8 is equal to the specified maximum battery voltage U_bat_max of the low-voltage battery 8. In this case, the DC-DC converter 5 thus regulates the on-board voltage U2 of the low-voltage on-board network 6 so that the on-board voltage U2 of the low-voltage on-board network 6 is equal to the battery voltage U1 of the low-voltage battery 8 and equal to the specified maximum battery voltage U_bat_max of the low-voltage battery 8.

Therefore, the following applies in normal operating mode: $$\text{U}2>\text{U}\_\text{min}$$ and $$\text{U}2\ge \text{U}1$$ and $$\text{U}2\le \text{U}\_\text{bat}\_\text{max}$$ where $$\text{U}2=\text{U}1\text{ und U}2=\text{U}\_\text{bat}\_\text{max}$$ only applies if $$\text{U}1=\text{U}\_\text{bat}\_\text{max}$$

The DC/DC converter 5 regulates the on-board voltage U2 in the low-voltage on-board network 6, in particular so that the battery voltage U1 of the low-voltage battery 8 is kept within a specified nominal voltage range.

If an overload occurs in the DC-DC converter 5 during normal operating mode, i.e., if the DC-DC converter 5 cannot fully supply the low-voltage electrical system 6 due to overload, the following occurs in the 5 The operating mode shown, with higher DC-DC converter power, is switched by opening the charging switch 10 and the DC-DC converter 5 setting or regulating the on-board voltage U2 in the low-voltage on-board network 6 to a voltage value Uh that is higher than the specified maximum battery voltage U_bat_max and at most as high as the specified maximum on-board voltage U_max of the low-voltage on-board network 6. The specified maximum on-board voltage U_max is the highest voltage at which all low-voltage electrical consumers 7.1 to 7.n may be operated.

Therefore, the following applies in operating mode with higher DC-DC converter power: $$\text{U}2=\text{Uh}$$ where $$\text{U}\_\text{bat}\_\text{max}<\text{Uh}\le \text{U}\_\text{max}$$

This allows the DC/DC converter to supply 5 additional electrical loads in the low-voltage electrical system 6, thus enabling the vehicle user to activate more electrical functions.

The discharge switch 11 remains closed. This allows the low-voltage battery 8 to continue to be charged. buffer dynamic electrical loads or, in the event of faults, for example in the event of a failure of the DC voltage converter 5, continue to supply the low-voltage on-board network 6.

Opening the charging switch 10 prevents the low-voltage battery 8 from being charged with a voltage Uh that exceeds the specified maximum battery voltage U_bat_max. The low-voltage battery 8 is then no longer charged, but remains available for safety-critical situations or dynamic maneuvers and can still supply current through the closed discharge switch 11.

In this operating mode with higher DC-DC converter power, the regulation of the on-board voltage U2 is thus independent of the low-voltage battery 8 and its limitations, in particular independent of its specified maximum battery voltage U_bat_max, by opening the charging switch 10. This allows the voltage to be increased without risking the dangers to the low-voltage battery 8 described above in the event of excessive voltage. The discharge switch 11, which remains closed, ensures that the low-voltage battery 8 can still buffer dynamic loads and supply the low-voltage on-board network 6 in cases where, for example, the DC-DC converter 5 fails.

For example, the charging switch 10 and the discharging switch 11 are already integrated into a conventional low-voltage battery 8, so that the described solution does not require any significant additional installation space or weight. Alternatively, low-voltage batteries 8 that do not have the charging switch 10 and the discharging switch 11 can also be used for the described solution, for example, by integrating the switching unit 12 with the charging switch 10 and the discharging switch 11 into a power distribution unit 13 connected between the low-voltage battery 8 and the low-voltage electrical system 6, or into another intermediate unit, as shown in 3 shown.

The described solution allows the vehicle user to activate more comfort functions in the low-voltage electrical system 6, thus avoiding any reduction in comfort. This solution eliminates the need for a larger or additional DC-DC converter, resulting in significant savings in cost, weight, and installation space.

It is specifically intended that the operating mode with higher DC-DC converter power will be terminated, i.e., from the in 5 The operating mode shown with higher DC-DC converter power is shown in the 4 The normal operating mode described above is reverted to when the DC-DC converter 5 is no longer fully loaded and the operating mode with higher DC-DC converter power is no longer required, and/or when the state of charge of the low-voltage battery 8 falls below a predefined minimum state of charge threshold, i.e., when the low-voltage battery 8 has been sufficiently discharged, for example, due to several dynamic maneuvers. As soon as one of these scenarios occurs, the charging switch 10 is closed again and the operating mode with higher DC-DC converter power is terminated. The low-voltage battery 8 is then charged again as usual, as described above for the normal operating mode, by adjusting the voltage accordingly.

For example, it is provided that the occurrence of an overload of the DC-DC converter 5 is detected by a control and/or regulation unit (not shown here), and/or that the charging switch 10 and/or the discharging switch 11 are actuated by the control and/or regulation unit, and/or that the DC-DC converter 5 is controlled and/or regulated by the control and/or regulation unit. The control and/or regulation unit is, for example, a component of an on-board power supply management system, the DC-DC converter 5, the low-voltage battery 8, or another component, in particular a software component, of the vehicle.

Reference symbol list

1

On-board electrical system arrangement

2

High-voltage electrical system

3

Schütz

4

High-voltage battery

5

DC/DC converter

6

Low-voltage electrical system

7.1 to 7.n

Low-voltage consumers

8

Low-voltage battery

9

Battery cells

10

charging switch

11

discharge switch

12

Switching unit

13

Power distribution unit

Claims (10)

A method for operating an electrical system arrangement (1) for a vehicle, wherein the electrical system arrangement (1) comprises a high-voltage electrical system (2) and a low-voltage electrical system (6) connected to the high-voltage electrical system (2) via a DC-DC converter (5) with low-voltage electrical consumers (7.1 to 7.n), and wherein battery cells (9) of a low-voltage battery (8) can be electrically coupled or connected to the low-voltage electrical system (6) via a switching unit (12) comprising a charging switch (10) for charging the low-voltage battery (8) via the DC-DC converter (5) and a discharging switch (11) for supplying electrical energy to the low-voltage consumers (7.1 to 7.n) by the low-voltage battery (8), characterized in that the electrical system arrangement (1) is operated in a normal operating mode as long as the DC-DC converter (5) can supply all activated low-voltage consumers (7.1 to 7.n) with electrical energy, wherein in the normal operating mode the The charging switch (10) and the discharging switch (11) are closed, and the DC-DC converter (5) regulates the on-board voltage (U2) in the low-voltage on-board network (6) such that the on-board voltage (U2) is: - higher than a predetermined minimum on-board voltage (U_min) of the low-voltage on-board network (6), and - higher than or equal to a battery voltage (U1) of the low-voltage battery (8), and - at most as high as a predetermined maximum battery voltage (U_bat_max) of the low-voltage battery (8), whereby in the event of an overload of the DC-DC converter (5) in normal operating mode, the system switches to an operating mode with higher DC-DC converter power by opening the charging switch (10) and the DC-DC converter (5) sets or regulates the on-board voltage (U2) in the low-voltage on-board network (6) to a voltage value (Uh) that is higher than the predetermined maximum battery voltage. (U_bat_max) and is at most as high as a specified maximum on-board voltage (U_max) of the low-voltage on-board network (6). Procedure according to Claim 1 , characterized in that the occurrence of the overload of the DC voltage converter (5) is determined by a control and/or regulation unit and/or that the charging switch (10) and/or the discharging switch (11) are actuated by the control and/or regulation unit and/or that the DC voltage converter (5) is controlled and/or regulated by the control and/or regulation unit. Method according to one of the preceding claims, characterized in that the specified minimum on-board voltage (U_min) and the specified maximum on-board voltage (U_max) are specified or are specified depending on specified voltage limits of the low-voltage consumers (7.1 to 7.n). Method according to one of the preceding claims, characterized in that the system switches from the operating mode with higher DC-DC converter power back to the normal operating mode when the DC-DC converter (5) is no longer fully utilized and the operating mode with higher DC-DC converter power is no longer required, and/or when the state of charge of the low-voltage battery (8) falls below a predetermined minimum state of charge threshold. On-board electrical system arrangement (1) for a vehicle, operable by means of a method according to one of the preceding claims, comprising: - the high-voltage on-board electrical system (2), - the DC-DC converter (5), - the low-voltage on-board electrical system (6) connected to the high-voltage on-board electrical system (2) via the DC-DC converter (5) with the low-voltage consumers (7.1 to 7.n), - the low-voltage battery (8), and - the switching unit (12) with the charging switch (10) for charging the low-voltage battery (8) via the DC-DC converter (5) and the discharging switch (11) for supplying electrical energy to the low-voltage consumers (7.1 to 7.n) by the low-voltage battery (8), wherein the battery cells (9) of the low-voltage battery (8) can be electrically coupled to or are coupled to the low-voltage on-board electrical system (6) via the switching unit (12), wherein the on-board electrical system arrangement (1) can be operated in normal operating mode as long as the DC-DC converter (5) supplies all activated low-voltage consumers (7.1 to 7.n) can supply electrical energy, wherein in normal operating mode the charging switch (10) and the discharging switch (11) are closed and the DC-DC converter (5) regulates the on-board voltage (U2) in the low-voltage on-board network (6) such that the on-board voltage (U2) is - higher than the specified minimum on-board voltage (U_min) of the low-voltage on-board network (6), and - higher than or equal to the battery voltage (U1) of the low-voltage battery (8), and - at most as high as the specified maximum battery voltage (U_bat_max) of the low-voltage battery (8), wherein in the event of an overload of the DC-DC converter (5) in normal operating mode it is possible to switch to the operating mode with higher DC-DC converter power. by opening the charging switch (10) and adjusting or regulating the on-board voltage (U2) in the low-voltage on-board network (6) to the voltage value (Uh) which is higher than the specified maximum battery voltage (U_bat_max) and is at most as high as the specified maximum on-board voltage (U_max) of the low-voltage on-board network (6) by the DC voltage converter (5). On-board electrical system arrangement (1) according to Claim 5 , characterized by the control and/or regulation unit, which is designed to detect the occurrence of the overload of the DC voltage converter (5) and/or to actuate the charging switch (10) and/or the discharging switch (11) and/or to control and/or regulate the DC voltage converter (5). On-board electrical system arrangement (1) according to Claim 6 , characterized in that the control and/or regulation unit is a component of an on-board network management system, the DC voltage converter (5) or the low-voltage battery (8). On-board electrical system arrangement (1) according to one of the Claims 5 until 7 , characterized in that the specified minimum on-board voltage (U_min) and the specified maximum on-board voltage (U_max) are specified depending on the specified voltage limits of the low-voltage consumers (7.1 to 7.n). On-board electrical system arrangement (1) according to one of the Claims 5 until 8 , designed to switch back from the operating mode with higher DC power to the normal operating mode when the DC power converter (5) is no longer fully utilized and the operating mode with higher DC power is no longer required, and/or when the state of charge of the low-voltage battery (8) falls below the specified minimum state of charge limit. On-board electrical system arrangement (1) according to one of the Claims 5 until 9 , characterized in that the switching unit (12) is arranged in the low-voltage battery (8).