On-board electrical system and methods for operating an on-board electrical system

Abstract

The invention relates to an on-board electrical system (1), wherein the on-board electrical system (1) comprises at least one basic on-board electrical system (2) which has a first voltage supply (7), wherein the on-board electrical system (1) has at least two decoupled on-board electrical system paths (3, 4), each of which is connected to the basic on-board electrical system (2) via a DC / DC converter (5, 6), wherein the DC / DC converters (5, 6) each have at least one control unit (10, 11) configured to generate a target output voltage or a target output current for the on-board electrical system paths (3, 4), wherein at least one control unit (10, 11) of an on-board electrical system path (3, 4) is configured to superimpose an AC voltage signal with a predetermined frequency on the target output voltage or the target output current in a test cycle, wherein the other on-board electrical system path (4, 3) is configured to control the voltage and / or current in the other on-board electrical system path (4, 3). to capture, wherein at least one control unit (10, 11) is designed in such a way,to subject the voltage signal and / or the current signal in the other vehicle electrical system path (4, 3) to a frequency analysis, wherein the at least one control unit (10, 11) is configured to generate an error signal if a frequency component greater than a threshold value for the specified frequency is detected in the voltage signal and / or current signal, and an associated method.

Description

[0001] The invention relates to an on-board power supply and a method for operating an on-board power supply, wherein the on-board power supply is in particular an on-board power supply for a motor vehicle.

[0002] A generic vehicle electrical system is known from DE 10 2015 200 121 A1. This system includes at least one component that is assigned to multiple vehicle electrical system paths and is designed to perform diagnostics on these paths. It is further proposed that the diagnostics be performed using the DC / DC converters, specifically based on the output voltages of the DC / DC converter, which are the input voltages of the vehicle electrical system path. Depending on the design of the vehicle electrical system paths, and in particular the components located within them, such diagnostics are often complex and can lead to incorrect diagnoses.

[0003] The invention is therefore based on the technical problem of improving a generic vehicle electrical system in such a way as to improve the diagnosis of galvanic faults in particular, and of providing a corresponding method.

[0004] The solution to the technical problem is achieved by a vehicle electrical system with the features of claim 1 and a method with the features of claim 9. Further advantageous embodiments of the invention are set forth in the dependent claims.

[0005] The vehicle electrical system comprises at least one basic electrical system with a primary power supply. Furthermore, the electrical system comprises at least two decoupled electrical system paths, each connected to the basic electrical system via a DC / DC converter. Each DC / DC converter has at least one control unit configured to generate a target output voltage or current for the respective electrical system path. At least one control unit of a DC / DC converter in one of the electrical system paths is configured to superimpose an AC voltage signal with a predefined frequency onto the target output voltage or current during a test cycle. The other electrical system path is configured to detect the voltage and / or current in the other electrical system path (i.e., its own voltage and / or current).

[0006] Furthermore, at least one control unit is configured to perform a frequency analysis of the voltage signal and / or the current signal in the other vehicle electrical system path. This control unit is also configured to generate an error signal if a frequency component exceeding a threshold value for the specified frequency is detected in the voltage signal and / or current signal. This allows for the highly reliable detection of unwanted galvanic coupling or connection between the vehicle electrical system paths, preventing them from functioning without feedback. Preferably, all control units of all DC / DC converters are configured to perform a test cycle, particularly since this does not require additional hardware. However, it is also possible to configure the system so that only a single control unit can perform the test cycle.Preferably, the AC voltage signal is a voltage signal superimposed on the target output voltage, with the current being measured in the other electrical system path. The frequency analysis can be performed by the control unit of the DC / DC converter in the electrical system path where the current (and / or voltage) is measured, and the result is then transmitted to the control unit that performed the test cycle with the AC voltage signal. Alternatively, this control unit can also perform the frequency analysis on the measured values ​​of the other electrical system path.

[0007] It should be noted that the detection of faults in the decoupling is very robust and better than pure voltage or current considerations, especially when very dynamic consumers are arranged in the vehicle electrical system paths.

[0008] In principle, frequency analysis can also be performed using a bandpass filter. However, a Fast Fourier Transform is preferred for frequency analysis.

[0009] In another embodiment, the first power supply is a high-voltage battery and the DC / DC converters are designed as galvanically isolated DC / DC converters. The vehicle electrical system paths are then preferably low-voltage electrical systems.

[0010] In another embodiment, at least one DC / DC converter is designed as a bidirectional DC / DC converter, so that, for example, an intermediate circuit capacitor in the basic on-board network can be pre-charged from a vehicle network path.

[0011] In another embodiment, the amplitude of the AC voltage signal is between 1 and 10% of the target output signal, preferably between 2 and 5%. This avoids feedback effects on consumers in the vehicle electrical system that are sensitive to voltage fluctuations.

[0012] The specified frequency is preferably between 1 and 100 Hz. In another embodiment, the specified frequency is selected depending on the switching frequencies used (DC / DC converter or load). The specified frequency is chosen, in particular, such that it is not a multiple of a switching frequency. Alternatively, the specified frequency is a prime number, e.g., 19 Hz.

[0013] In another embodiment, a voltage source, preferably designed as a battery, is arranged in each of the vehicle electrical system paths.

[0014] Regarding the procedural details, full reference is made to the preceding statements.

[0015] The invention is explained in more detail below with reference to a preferred embodiment. The single figure shows a schematic block diagram of an on-board electrical system.

[0016] In the Fig.Figure 1 shows a schematic block diagram of an on-board electrical system 1, which comprises a base on-board electrical system 2 and at least two on-board electrical system paths 3, 4. The on-board electrical system paths 3, 4 are each connected to the base on-board electrical system 2 via DC / DC converters 5, 6. The base on-board electrical system 2 has a first voltage source 7, which is, for example, a high-voltage battery with a voltage greater than 60 V. For example, the voltage is between 380 and 800 V. A load 8 and an intermediate circuit capacitor 9 are also schematically arranged. The DC / DC converters 5, 6 each have a control unit 10, 11, wherein the control units 10, 11 are interconnected via a bus system 12 or a direct data line. The on-board electrical system paths 3, 4 are preferably low-voltage electrical systems and have a nominal voltage of 12 V. Furthermore, the vehicle electrical system paths 3, 4 have at least one electrical consumer 13, 14, which are preferably safety-relevant.Furthermore, the vehicle electrical system paths 3 and 4 each have their own voltage source 15 and 16, as well as a voltage measuring device 17 and 18 and a current measuring device 19 and 20. The two vehicle electrical system paths 3 and 4 are decoupled from each other without feedback via the DC / DC converters 5 and 6, meaning that voltage fluctuations in one path have no effect on the other. However, this is no longer guaranteed if there is a faulty galvanic coupling between the two paths 3 and 4. To detect such galvanic coupling and, if necessary, to take countermeasures at an early stage, the control unit 10 and / or the control unit 11 can superimpose an AC voltage signal onto an output signal during a test cycle.

[0017] The following explains this test procedure, assuming that the control unit 10 generates the AC voltage signal and superimposes it on its target output voltage. The AC voltage signal has a predefined frequency f and is, for example, a sine wave. This results in an AC component with frequency f also appearing in the current of the vehicle electrical system path 3. With intact decoupling of the vehicle electrical system paths 3 and 4, this AC voltage signal in vehicle electrical system path 3 has no effect on vehicle electrical system path 4. Therefore, in the test cycle, the current in vehicle electrical system path 4 is measured and subjected to a frequency analysis, in particular a Fast Fourier Transform is performed. If frequency components at the predefined frequency f are then present in the current of vehicle electrical system path 4, this indicates a faulty galvanic connection.The frequency analysis can, for example, be performed in control unit 11 and the result transmitted to control unit 10 via bus system 12. The specified frequency f of control unit 11 can be known in advance. Alternatively, control unit 11 or another unit transmits the measured values ​​for the current in the vehicle electrical system path 4 to control unit 10, which then performs the frequency analysis. Reference symbol list 1 On-board electrical system 2 Basic electrical system 3, 4 On-board power supply path 5, 6 DC / DC converters 7 Voltage source 8 consumers 9 Intermediate circuit capacitor 10, 11 Control unit 12 bus system 13, 14 Consumers 15, 16 Voltage source 17, 18 Voltage measuring device 19, 20 Current measuring device QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2015 200 121 A1

[0002]

Claims

[1] On-board electrical system (1), wherein the on-board electrical system (1) comprises at least one basic on-board electrical system (2) which has a first voltage supply (7), wherein the on-board electrical system (1) has at least two decoupled on-board electrical system paths (3, 4) which are each connected to the basic on-board electrical system (2) via a DC / DC converter (5, 6), wherein the DC / DC converters (5, 6) each have at least one control unit (10, 11) which is configured to generate a target output voltage or a target output current for the on-board electrical system paths (3, 4), characterized by, that at least one control unit (10, 11) of a vehicle electrical system path (3, 4) is configured to superimpose an AC voltage signal with a predetermined frequency on the target output voltage or target output current in a test cycle, wherein the other vehicle electrical system path (4, 3) is configured to detect the voltage and / or current in the other vehicle electrical system path (4, 3), wherein at least one control unit (10, 11) is configured to subject the voltage signal and / or current signal in the other vehicle electrical system path (4, 3) to a frequency analysis, and wherein the at least one control unit (10, 11) is configured to generate an error signal if a frequency component greater than a threshold value for the predetermined frequency is detected in the voltage signal and / or current signal. [2] On-board electrical system according to claim 1, characterized by that the frequency analysis is a Fast Fourier Transform. [3] On-board electrical system according to claim 1 or 2, characterized by, that the first voltage supply (7) is a high-voltage battery and the DC / DC converters (5, 6) are designed as galvanically isolated DC / DC converters. [4] On-board electrical system according to any of the preceding claims, characterized by , that at least one DC / DC converter (5, 6) is designed as a bidirectional DC / DC converter. [5] On-board electrical system according to any of the preceding claims, characterized by , that the amplitude of the AC voltage signal is between 1 - 10% of the target output signal. [6] On-board electrical system according to any of the preceding claims, characterized by , that the specified frequency lies between 1 - 100 Hz. [7] On-board electrical system according to claim 6, characterized by , that the specified frequency is chosen depending on the switching frequencies used in the on-board network paths (3, 4) or has a prime number value. [8] On-board electrical system according to one of the preceding claims, characterized by, that in each of the vehicle electrical system paths (3, 4) a voltage source (1,5 16) is arranged. [9] Method for operating an on-board network, wherein the on-board network (1) comprises at least one basic on-board network (2) with a first voltage supply (7) and at least two decoupled on-board network paths (3, 4), each of which is connected to the basic on-board network (2) via a DC / DC converter (5, 6), wherein the DC / DC converters (5, 6) each comprise at least one control unit (10, 11) which generates a target output voltage or a target output current for the on-board network paths (3, 4), characterized by, that at least one control unit (10, 11) of a DC / DC converter (5, 6) of a vehicle electrical system path (3, 4) superimposes an AC voltage signal with a predetermined frequency on the target output voltage or the target output current in a test cycle, wherein the voltage and / or current are recorded in the other vehicle electrical system path (4, 3), wherein at least one control unit (10, 11) subjects the voltage signal and / or the current signal in the other vehicle electrical system path (4, 3) to a frequency analysis, wherein an error signal is generated if a frequency component greater than a threshold value for the predetermined frequency is detected in the voltage signal and / or current signal. [10] Method according to claim 9, characterized by that the frequency analysis is a Fast Fourier Transform.

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