Method for operating a vehicle's low-voltage electrical system

Abstract

Method for operating a low-voltage electrical system (1) of a vehicle, wherein, upon detection of energy feedback into the low-voltage electrical system (1), caused by an electrical energy consumer (V1) connected to an electrical power distributor (2) and configured as a rack and pinion actuator of a steering system of the vehicle, as a tailgate actuator of the vehicle, or as a windshield wiper actuator of the vehicle, at least one electrical energy consumer (V2, V3) connected to the same electrical power distributor (2) is switched on by means of this electrical power distributor (2), wherein the at least one electrical energy consumer (V2, V3) is switched on by means of an electronic logic within the electrical power distributor (2) upon detection of energy feedback into the low-voltage electrical system (1).wherein the energy feedback is detected by means of a reverse electrical current flow and an electrical overvoltage (Uu), wherein the overvoltage (Uu) is determined by a central voltage measurement (U1) at the electrical power distributor (2), wherein a comfort consumer is switched on as an electrical energy consumer (V2, V3), wherein the switching on of the at least one electrical energy consumer (V2, V3) is effected by means of at least one semiconductor switch (S1, S2, S3) in the electrical power distributor (2), and wherein the at least one switched-on electrical energy consumer (V2, V3) is switched off again after the energy feedback into the electrical low-voltage on-board network (1) has ended.

Description

The invention relates to a method for operating a low-voltage electrical system of a vehicle according to the features of the preamble of claim 1.As described in DE 10 2018 201 546 A1, a device for protecting a load in an on-board power supply of a motor vehicle is known from the prior art. The device comprises a switching means for supplying the load with electrical energy, a controller for controlling the switching means and detection means for detecting the characteristic variables current and voltage. The controller controls the switching means as a function of the characteristic variables, wherein at least one overvoltage protection is provided.The object of the invention is to specify a method for operating an electrical low-voltage on-board system of a vehicle which is improved compared with the prior art.The object is achieved according to the invention by a method for operating an electrical low-voltage vehicle electrical system having the features of claim 1.Advantageous embodiments of the invention are the subject matter of the dependent claims.In a method for operating an electrical low-voltage on-board system of a vehicle, according to the invention, when energy feedback is detected into the electrical low-voltage on-board system, at least one electrical energy consumer or a plurality of electrical energy consumers are connected by means of an electrical power distributor, in particular by means of electronic logic within the electrical power distributor, in particular by means of logic within the electrical power distributor implemented by means of electronic logic modules. This connection is effected in particular in addition to at least one or more already active electrical energy consumers, in particular in addition to the at least one electrical energy consumer which causes the energy feedback. It is provided in particular that the electrical energy consumer causing the energy feedback and the at least one or the plurality of electrical energy consumers to be connected or connected are connected to the electrical power distributor, i.e. to the same electrical power distributor.The term "low voltage" is understood in particular to mean a voltage of up to 48 V, for example 12 V or 16 V or 24 V or 48 V.The at least one electrical load that causes the energy recovery is in particular an electromechanical load that generates electrical energy when braking or stopping a respectively connected mechanical load. This is referred to as regeneration or recuperation. Since the electrical energy flows back into the low-voltage electrical system, this is called energy recovery. The above-mentioned detected energy recovery is thus based in particular on this regeneration or recuperation. In particular, the regeneration or recuperation of at least one electrical load embodied as an electromechanical load is thus detected. Examples of such loads or electromechanical loads are a steering system of the vehicle, in particular a rack actuator of the steering system, a tailgate actuator of the vehicle and / or a windshield wiper actuator of the vehicle.The at least one or respective electrical load which is connected is in particular an electrical load which is not provided exclusively as an energy sink for the energy recovery in the vehicle, but rather a functional component which is provided for another function in the vehicle and is additionally used as an energy sink when the energy recovery is detected by its connection. The at least one or respective electrical energy consumer which is connected is thus in particular a comfort consumer or a safety consumer of the vehicle. Comfort consumers are advantageously connected.Comfort consumers are, for example, a seat heater, a seat ventilation, an electric heater, an electric air-conditioning device and / or a passenger compartment ventilation.Safety consumers are, for example, an electric steering assistance device of the vehicle, an electric brake assistance device of the vehicle and / or a driver assistance device of the vehicle.The at least one or respective electrical load which is connected is advantageously a predefined electrical load, for example a comfort load, the connection of which has no safety-relevant influence and advantageously also has no disturbing influence and / or influence which is noticeable to vehicle occupants. Suitable in particular are heating consumers, for example a seat heater or window heater, in particular electrical consumers, which during short-lasting operating times, in particular for the operating time required for the method of, for example, less than one second, have no effect noticeable by vehicle occupants.The at least one electrical load causing the energy recovery may be a safety load or a comfort load.The energy feedback is detected in particular on the basis of a reverse electric current flow and / or on the basis of an electrical overvoltage, in particular on the basis of a voltage rise of an on-board power supply voltage of the electrical low-voltage on-board power supply system, which reaches or exceeds a predefined voltage limit value and / or a predefined voltage rise limit value. The overvoltage is in particular an on-board electrical system voltage of the low-voltage electrical system that deviates upward from a normal on-board electrical system voltage.It is provided in particular that the overvoltage is determined by a central voltage measurement at the electrical power distributor.It is provided in particular that the described connection of the electrical load does not take place until the electrical overvoltage is detected, i.e. in particular only when the electrical overvoltage, i.e. the vehicle electrical system voltage deviating upward from the normal vehicle electrical system voltage, reaches or exceeds the predefined voltage limit value and / or the predefined voltage rise limit value. The predefined voltage limit value is in particular a predefined safety limit, in particular a safety limit according to ISO26262. The safety limit is in particular a requirement of functional safety with respect to an overvoltage limit.The at least one electrical energy consumer is connected in particular by means of at least one semiconductor switch, also referred to as eUse, in the electrical power distributor. The connection of a plurality of electrical energy consumers is accordingly respectively effected by means of at least one semiconductor switch in the electrical power distributor.In one possible embodiment, the at least one or respective connected electrical energy consumer is switched off again after the energy feedback into the electrical low-voltage on-board electrical system has ended.As already described above, the electrical low-voltage on-board electrical system supplies, in particular, both comfort consumers and safety consumers. The safety consumers are in particular systems with safety requirements for the energy supply. The comfort consumers are in particular systems which only contain comfort functions.It is provided in particular that the vehicle also has an electrical high-voltage on-board electrical system and the electrical low-voltage on-board electrical system has at least one DC voltage converter for supplying energy to the electrical low-voltage on-board electrical system from the electrical high-voltage on-board electrical system. In addition, the electrical low-voltage on-board electrical system can have, for example, one low-voltage battery or a plurality of low-voltage batteries for providing energy. Alternatively, however, the electrical low-voltage on-board electrical system may also not have a low-voltage battery, but rather may be supplied with energy only by the electrical high-voltage on-board electrical system.The power distribution, in particular the current distribution of DC-DC converters and / or low-voltage batteries to the safety consumers and comfort consumers, takes place via the electrical power distributor or a plurality of such electrical power distributors. The respective electrical power distributor is designed in particular as an intelligent electrical power distributor. The electrical power distributor contains, in particular at outputs to the loads, i.e. to the comfort consumers and safety consumers, the semiconductor switches, also referred to as eFus.The eFus in the electrical power distributors are installed primarily for two reasons. Freedom from reaction is to be ensured, i.e. if an electrical load has a fault, for example a short circuit, then this fault must not have an interfering effect on the safety loads. Furthermore, line protection is to be ensured. A short circuit on a line must be switched off before the line becomes too warm and a risk of fire could thus arise.As already described above, the energy recovery, which is detected, is caused in particular by regeneration or recuperation of at least one electromechanical safety or comfort consumer, which generates electrical energy when braking or stopping the respectively connected mechanical load.There has been the problem up to now that in certain cases less electrical energy can be drawn in the electrical low-voltage on-board system than is fed back into the electrical low-voltage on-board system by recuperation or regeneration. This results in a strong and fast voltage rise in the electrical low-voltage on-board electrical system and finally an overvoltage. Further consequences can be a surge arrester of the electrical loads connected to the electrical low-voltage on-board electrical system or a destruction of an input circuit or a further logic of the components. The result is a loss of functions, in particular also of safety functions.The surge arrester is effected in particular as soon as a fault tolerance time is exceeded, i.e. a time in which safety limits may be exceeded before a risk according to ISO26262 occurs. Safety limits are functional safety requirements that require safety-relevant systems from the low-voltage electrical system, typically undervoltage and overvoltage limits.The described situation can occur, for example, if the low-voltage battery is not available for absorbing the electrical energy fed back into the electrical low-voltage on-board system, for example if the low-voltage battery is already fully charged and then, in particular, a charging circuit breaker is opened, or if no low-voltage battery is installed in the electrical low-voltage on-board system, i.e. if the electrical low-voltage on-board system is designed as a batteryless on-board system or sub-board system, or if the low-voltage battery is defective or has failed, i.e. in particular in the event of a fault in the low-voltage battery.Furthermore, this situation can occur, for example, if the DC-to-DC converter cannot transfer the electrical energy fed back into the electrical low-voltage on-board system or cannot transfer it fast enough from the electrical low-voltage on-board system into the electrical high-voltage on-board system, for example if the DC-to-DC converter has failed, i.e. in the event of a fault in the DC-to-DC converter, or on account of conflicting safety requirements with respect to the operating mode of the DC converter, so that boost converter operation of the DC converter is not possible in the present scenario, or if too few other electrical loads, in particular those which do not feed back, are already active in order to absorb energy and, for example, consume it.The solution described prevents the occurrence of this situation in the manner described above, i.e. by the connection of at least one electrical energy consumer by means of the electrical power distributor. For the described solution, the already existing hardware is thus advantageously used, in particular the electrical power distributor including the eFus and already present electrical loads. The method described represents in particular an implementation of a load fast-connection. The energy-regenerative component, i.e. the electrical load causing the energy feedback, and the energy-regenerative energy-consuming load, i.e. the electrical load which is connected by the electrical power distributor, are supplied in particular by the same electrical power distributor. As a result, the overvoltage at the point of origin can be detected.The following procedure is provided in particular for the method for operating the electrical low-voltage vehicle electrical system of the vehicle:In a normal operating case of the electrical low-voltage vehicle electrical system, there is no undervoltage and no overvoltage. The supply of the electrical low-voltage vehicle electrical system is effected in particular via the DC-DC converter, which is in normal operation and supplies all activated electrical loads, in particular all static loads. If dynamic loads occur, for example short peak currents due to a rapid steering or braking intervention, the low-voltage battery takes over this portion of the electrical energy supply, for example.If energy regenerations occur in the normal operating case, in particular short currents, for example as a result of a rapid steering or braking intervention, the already active electrical loads and / or an energy store, in particular the low-voltage battery, absorb this energy. In other words, in the normal operating case, sufficient energy sinks are already available, for example, by energy stores, in particular the low-voltage battery, and / or by already active electrical loads, in order to absorb these energy feedbacks and thus to avoid an overvoltage. The direct supply of the electrical loads takes place via one or more electrical power distributors which supply both comfort loads and safety loads.The above-described connection of the electrical load by the electrical energy distributor is carried out in an overvoltage operating case. In this overvoltage operating case, an energy feedback into the electrical low-voltage onboard electrical system occurs, for example, by a dynamic steering maneuver and an energy feedback thereby of the electrical load embodied as an electrical steering assistance device. For the reasons mentioned above, in particular because of a fault or already fully charged state, the energy store, in particular the low-voltage battery, does not take part in operation or is not present in the electrical low-voltage on-board electrical system, and sufficient electrical loads are already activated, i.e. there are not sufficient energy sinks present to absorb the energy feedback. As a result, the energy feedback into the electrical low-voltage on-board electrical system leads to an energy surplus and thus to an overvoltage.Thus, in the method described here, in particular when the energy feedback into the electrical low-voltage on-board electrical system is detected, at least one electrical energy consumer is then connected by means of the electrical power distributor, i.e. the load fast connection is engaged at this time.In this case, it is provided in particular that the reverse current flow is detected by a current measurement in the energy-feeding path and the overvoltage is detected by a central voltage measurement at the electrical power distributor. If the overvoltage at this central voltage measurement reaches or exceeds the predefined voltage limit value, in particular the predefined safety limit, and / or the predefined voltage rise limit value, at least one electrical load or a plurality of electrical loads are connected, in particular by logic implemented by means of electronic logic modules, in particular by means of the electrical energy distributor. Advantageously, predefined electrical consumers are used for this purpose, for example comfort consumers whose connection has no safety-relevant influence and advantageously also has no disturbing influence and / or influence noticeable to vehicle occupants.The connection is effected by the eFus, i.e. in particular by the semiconductor switches which are activated directly in the electrical power distributor for the connection of the respective electrical load.The goal of the rapid load connection is to bring the vehicle electrical system voltage in the low-voltage vehicle electrical system back into a predefined normal range within the fault tolerance time. Optionally, the subsequent disconnection of the loads activated by the rapid load connection, i.e. the connected electrical loads, can take place.The described solution makes it possible in particular to avoid overvoltage in the electrical low-voltage on-board electrical system caused by energy feedback if the latter has a low energy absorption capacity before the at least one electrical load is connected.The described solution furthermore makes it possible to avoid additional costs, additional weight, additional installation space and any possible risk to safety goals by installing additional components that are not required in the described solution.The described solution also enables synergistic use of already implemented components, in particular eFus, and electrical loads.The described solution enables a prevention of over-voltages or a failure in the electrical low-voltage onboard network and a protection and a robustness increase of the electrical low-voltage onboard network, in particular compliance with the safety limits.In the described solution, the detection, in particular of the overvoltage, and the consumption control by switching on the at least one or respective electrical load are locally close and thus prevent the overvoltage from propagating into the remaining electrical low-voltage vehicle electrical system. This allows short time intervals for fault detection and fault response. This allows the overvoltage robustness of other components to be shortened over time, which can save costs.The described solution enables a reduction of current consumption requirements in the electrical low-voltage on-board system. No energy storage device has to be provided, in particular also no low-voltage battery. This makes it possible to save costs, weight and installation space.The solution described makes it possible to dispense with bidirectionally current-carrying semiconductors in the conduction path from the regenerative component to energy sinks outside the power distributor. This makes it possible to save costs, weight and installation space.The described solution has advantages in particular over alternative solution options in which additional current sinks, for example artificial loads and / or other energy stores, are installed in the electrical low-voltage on-board system, i.e. components which are provided exclusively as an energy sink for the energy recovery in the vehicle and are not provided for any other function in the vehicle. These alternative solution options have the disadvantage, compared to the described solution, that these additional components create fault paths and thus reduce the functional safety in the electrical low-voltage on-board network. In addition, additional components with the dedicated purpose of consuming excess electric energy generate heat at the site of construction. This heat must additionally be removed and may result in a limited function of the surrounding logic. Additional energy stores are large cost drivers and result in increased installation space and weight requirements.Exemplary embodiments of the invention are explained in more detail below with reference to drawings.The following are shown: FIG. 1 schematically shows an electrical low-voltage on-board system of a vehicle in a normal operating case, FIG. 2 schematically shows the electrical low-voltage on-board electrical system in an overvoltage operating case, and FIG. 3 schematically shows a temporal profile of an on-board power supply voltage of the electrical low-voltage on-board power supply system.Corresponding parts are provided with the same reference numerals in all figures.With reference to FIGS. 1, 2 to 3, a method for operating an electrical low-voltage on-board electrical system 1 of a vehicle is described below. In this method, it is provided, in particular in an overvoltage operating case illustrated in FIG. 2 and described in more detail below, that, in the event of a detected energy feedback into the electrical low-voltage on-board electrical system 1, at least one electrical energy consumer V 2, V 3 or a plurality of electrical energy consumers V 2, V 3 are connected by means of an electrical power distributor 2, in particular by means of an electronic logic within the electrical power distributor 2.This connection is effected in particular in addition to at least one or more already active electrical energy consumers V 1, in particular in addition to the at least one electrical energy consumer V 1, which causes the energy feedback. It is provided in particular that the electrical energy consumer V 1 causing the energy feedback and the at least one or more electrical energy consumers V 2, V 3 to be connected or connected are connected to the electrical power distributor 2, i.e. to the same electrical power distributor 2, as shown in FIGS. 1 and 2.The at least one electrical load V 1, which causes the energy recovery, is in particular an electromechanical load, which generates electrical energy when braking or stopping a respectively connected mechanical load. This is referred to as regeneration or recuperation. Since the electrical energy flows back into the electrical low-voltage on-board electrical system 1, this is called energy recovery.The electrical consumers V 1, V 2, V 3 can each be comfort consumers or safety consumers.The energy feedback is detected in particular on the basis of a reverse electric current flow and / or on the basis of an electric overvoltage Uu, in particular on the basis of a voltage rise of an on-board power supply system voltage U of the electric low-voltage on-board power supply system 1, which reaches or exceeds a predefined voltage limit value Umax. The overvoltage Uu is in particular an on-board power supply voltage U of the electrical low-voltage on-board power supply system 1 deviating upward from a normal on-board power supply voltage Un.It is provided in particular that the overvoltage Uu is determined by a central voltage measurement U 1 at the electrical power distributor 2.The at least one electrical energy consumer V 2, V 3 is connected in particular by means of at least one semiconductor switch S 1, S 2, S 3, also referred to as eUse S 1, S 2, S 3, in the electrical power distributor 2.In one possible embodiment, the at least one or respective connected electrical energy consumer V 2, V 3 is switched off again after the energy feedback into the electrical low-voltage on-board electrical system 1 has ended.The electrical low-voltage on-board electrical system 1 supplies, in particular, both comfort consumers and safety consumers. In the illustrated schematic example, the first electrical load V 1 is a steering assistance device and the second and third electrical loads V 2, V 3 are each a seat heater. The steering assistance device is, for example, a safety consumer. The seat heating devices are, for example, comfort consumers. Safety consumers are in particular systems with safety requirements for the energy supply. The comfort consumers are in particular systems which only contain comfort functions.In the example shown, the vehicle also has an electrical high-voltage on-board electrical system 3. The electrical low-voltage on-board electrical system 1 is connected to the electrical high-voltage on-board electrical system 3 by means of a DC-DC converter 4 for its electrical energy supply. In addition, the low-voltage electric system 1 may include, for example, a low-voltage battery 5 as shown in FIG. 1.The power distribution, in particular the current distribution of DC-DC converter 4 and / or low-voltage battery 5 to the safety consumers and comfort consumers, takes place via electrical power distributor 2. The electrical power distributor 2 contains, in particular at outputs to the loads, i.e. to the comfort consumers and safety consumers, the semiconductor switches S 1, S 2, S 3, also referred to as eFu S 1, S 2, S 3.There has been the problem up to now that in certain cases less electrical energy can be drawn in the electrical low-voltage on-board electrical system 1 than is fed back into the electrical low-voltage on-board electrical system 1 by recuperation or regeneration. This results in a strong and fast voltage rise in the electrical low-voltage on-board electrical system 1 and finally the overvoltage Uu. Further consequences can be a surge arrester of the electrical loads V 1, V 2, V 3 connected to the electrical low-voltage on-board electrical system 1 or a destruction of an input circuit or a further logic of the components. The result is a loss of functions, in particular also of safety functions.The surge arrester is effected in particular as soon as a fault tolerance time tF is exceeded, i.e. a time in which safety limits may be exceeded before a risk according to ISO26262 occurs. Safety limits are functional safety requirements that safety-relevant systems demand from the low-voltage electrical system 1, typically undervoltage and overvoltage limits.The described situation can occur, for example, if the low-voltage battery 5, as shown in FIG. 2, is not available for absorbing the electrical energy fed back into the electrical low-voltage on-board electrical system 1, for example if the low-voltage battery 5 is already fully charged and then, in particular, a charging circuit breaker is open, or if no low-voltage battery 5 is installed in the electrical low-voltage on-board electrical system 1, i.e. if the electrical low-voltage on-board electrical system 1 is designed as a batteryless on-board electrical system or sub-board electrical system, or if the low-voltage battery 5 has failed or failed, i.e. in particular in the event of a fault in the low-voltage battery 5.Furthermore, this situation can occur, for example, if the DC-to-DC converter 4 cannot transfer the electrical energy fed back into the low-voltage electrical system 1 or cannot transfer it fast enough from the low-voltage electrical system 1 into the high-voltage electrical system 3, for example if the DC-to-DC converter 4 has failed or has failed, i.e. in the event of a fault in the DC-to-DC converter 4, or on account of conflicting safety requirements with respect to the operating mode of the DC converter 4, so that in the present scenario a step-up converter operation of the DC converter 4 is not possible, or if too few other electrical loads V 2, V 3, in particular not feeding back, are already active in order to absorb energy and, for example, to consume it.The solution described here prevents the occurrence of this situation in the manner described above, i.e. by the connection of at least one electrical energy consumer V 2, V 3 by means of the electrical power distributor 2.The method described represents in particular an implementation of a load fast-addition circuit LS. The energy-feeding component, i.e. the electrical load V 1 causing the energy feedback and the load consuming the feedback energy, i.e. the at least one electrical load V 2, V 3 which is connected by the electrical power distributor 2, are supplied in particular by the same electrical power distributor 2. As a result, the overvoltage Uu at the point of origin can be detected.The following procedure is provided in particular for the method for operating the electrical low-voltage vehicle electrical system 1 of the vehicle:In a normal operating case of the electrical low-voltage on-board electrical system 1 shown in FIG. 1, there is no undervoltage and no overvoltage Uu. The supply of the electrical low-voltage vehicle electrical system 1 is effected in particular via the DC-DC converter 4, which is in normal operation and supplies all activated electrical loads V 1, in particular all static loads. In the example shown, only the first electrical load V 1 is activated. If dynamic loads occur, for example short peak currents due to a rapid steering or braking intervention, the low-voltage battery 5, for example, takes over this portion of the electrical energy supply.If energy regenerations occur in the normal operating case, in particular short currents, for example as a result of a rapid steering or braking intervention, the already active electrical loads V 1 and / or an energy store, in particular the low-voltage battery 5, absorb this energy. That is to say, in the normal operating case, sufficient energy sinks are already available, for example by energy stores, in particular the low-voltage battery 5, and / or by already active electrical loads V 1, in order to absorb these energy feedbacks and thus to avoid an overvoltage Uu. The direct supply of the electrical consumers V 1, V 2, V 3 takes place via one or more electrical power distributors 2, which supply both comfort consumers and safety consumers.The above-described connection of the at least one electrical load V 2, V 3 by the electrical energy distributor 2 is carried out in the overvoltage operating case illustrated in FIG. 2. In this overvoltage operating case, an energy feedback into the electrical low-voltage on-board electrical system 1 occurs, for example, by a dynamic steering maneuver and an energy feedback, thereby occurring, of the first electrical load V 1 embodied as an electrical steering assistance device. For the reasons mentioned above, in particular because of a fault or already fully charged state, the energy store, in particular the low-voltage battery 5, does not participate in operation, as schematically illustrated in FIG. 2, or is not present in the electrical low-voltage on-board electrical system 1, and sufficient electrical loads V 2, V 3 are not already activated, i.e. there are not sufficient energy sinks present to absorb the energy feedback. As a result, the energy feedback into the electrical low-voltage on-board electrical system 1 leads to an energy surplus and thus to an overvoltage Uu.Thus, in the method described here, in particular when energy feedback is detected into the electrical low-voltage on-board electrical system 1, at least one electrical energy consumer V 2, V 3 is then connected in, in the example shown, the second and third electrical energy consumers V 2, V 3 by means of the electrical power distributor 2, i.e. the load fast connection LS is engaged at this point in time.In this case, it is provided in particular that the reverse current flow is detected by a current measurement I 1 in the energy-feeding path and the overvoltage Uu is detected by the central voltage measurement U 1 at the electrical power distributor 2. If the overvoltage Uu reaches or exceeds the predefined voltage limit value Umax, in particular the predefined safety limit, at least one electrical load V 2, V 3 is connected, in particular by logic implemented by means of electronic logic modules, in particular by means of the electrical energy distributor 2, or a plurality of electrical loads V 2, V 3 are connected, as shown in FIG. 2. Advantageously, predefined electrical consumers V 2, V 3 are used for this purpose, for example comfort consumers whose connection has no safety-relevant influence and advantageously also has no disturbing influence and / or influence noticeable to vehicle occupants.The connection is effected by the eFu S 2, S 3, in the present case by the second and third eUse S 2, S 3, which are activated directly in the electrical power distributor 2 for the connection of the respective electrical load V 2, V 3.The goal of the load fast-connection LS is to bring the vehicle electrical system voltage U in the low-voltage vehicle electrical system 1 back into a predefined normal range within the fault tolerance time tF.The curve of the vehicle electrical system voltage U over time t in this overvoltage operating case is schematically illustrated in FIG. 3. When the energy recovery occurs E, the vehicle electrical system voltage U rises rapidly and exceeds the permitted maximum value, i.e. the predefined voltage limit value Umax. Within the fault tolerance time tF, the load fast access circuit LS engages, in the example shown, after a detection delay. The load fast-connection circuit LS limits the voltage rise, so that the further voltage rise does not take place, and returns the vehicle electrical system voltage U into the permitted range.Optionally, the subsequent disconnection of the loads activated by the load quick connection LS, i.e. the connected electrical loads V 2, V 3, can take place.List of reference characters1 Low-voltage on-board electrical system 2 Power distributor 3 High-voltage on-board electrical system 4 Direct voltage converter 5 Low-voltage battery E Entry of energy feedback I 1 Current measurement LS Rapid load connection S 1, S 2, S 3 Semiconductor switch, eUse t Time tF Fault tolerance time U On-board electrical system voltage U 1 Voltage measurement Umax Voltage limit value Un Normal electrical system voltage Uu Overvoltage V 1, V 2, V 3 Electrical energy consumersReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2018 201 546 A1

[0002]

Claims

Method for operating an electrical low-voltage on-board electrical system (1) of a vehicle, characterized in that, when energy recovery into the electrical low-voltage on-board electrical system (1) is detected, at least one electrical energy consumer (V2, V3) is connected by means of an electrical power distributor (2).Method according to Claim 1, characterized in that the at least one electrical energy consumer (V2, V3) is connected by means of electronic logic within the electrical power distributor (2) when energy feedback into the electrical low-voltage on-board electrical system (1) is detected.Method according to one of the preceding claims, characterized in that the energy feedback is detected on the basis of a reverse electrical current flow and / or on the basis of an electrical overvoltage (Uu).Method according to Claim 3, characterized in that the overvoltage (Uu) is determined by a central voltage measurement (U1) at the electrical power distributor (2).Method according to one of the preceding claims, characterized in that a comfort consumer is connected as an electrical energy consumer (V2, V3).Method according to one of the preceding claims, characterized in that the at least one electrical energy consumer (V2, V3) is connected by means of at least one semiconductor switch (S1, S2, S3) in the electrical power distributor (2).Method according to one of the preceding claims, characterized in that the at least one connected electrical energy consumer (V2, V3) is switched off again after the energy feedback into the electrical low-voltage on-board electrical system (1) has ended.

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