EP1264380A1

EP1264380A1 - Error recognition device for a multi-voltage vehicle electrical system

Info

Publication number: EP1264380A1
Application number: EP01994596A
Authority: EP
Inventors: Michael Horbelt; Joerg Jehlicka; Andre Owerfeldt
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-12-08
Filing date: 2001-12-06
Publication date: 2002-12-11
Also published as: WO2002047234A1; AU2002224745A1; JP2004515999A; US20030011248A1; DE10061047A1

Abstract

Disclosed is a device for recognizing errors in a multi-voltage vehicle electrical system, comprising at least one detection unit which detects a supply potential (U0) impinged upon a power distributor (16) for the power supply of electrical loads (22). Said power distributor supplies power to at least one electrical load (22) via an output (9). Another detection device which detects the output potential (U1) at the output (9) is also provided. Error recognition means (24) generate an error signal (26) if the output potential (U1) differs from the supply potential (U0) to a specific extent.

Description

Device for fault detection in a multi-voltage electrical system

State of the art

The invention relates to a device for error detection in a multi-voltage electrical system according to the preamble of the independent claim. In electrical systems with a large number of electrical consumers, for example in motor vehicle electrical systems, there is the problem that a 12 V voltage is no longer sufficient to supply energy. Since some of the consumers should be supplied with a voltage higher than 12V, multi-voltage electrical systems are known that have two different voltage levels, such as a first voltage level that is at + 12V relative to ground and a second voltage level at + 36V, these voltages each having the nominal voltages are. The connection between the two voltage levels is established with the help of a DC voltage converter.

Such a multi-voltage electrical system in a motor vehicle is described in DE-A 198 45 569. The electrical energy is generated in this electrical system using a three-phase generator that is driven by the vehicle engine and delivers an output voltage of 42V (charging voltage). With this charging voltage, a 36V (nominal voltage) battery loaded. A 12 V battery with a charging voltage of 14 V is supplied via a DC voltage converter. The electrical consumers can be connected to the two batteries via suitable switches, the 12V battery supplying the conventional electrical system consumers, for example incandescent lamps, while the 36V battery is used to supply high-performance consumers, for example window heaters. In the known electrical system, the negative connections of the two batteries are each at the same ground potential. Measures to prevent a short circuit between the 12V or 14V voltage level and the 36V or 42V voltage level are not addressed in the prior art.

The object of the invention is to enable error detection, in particular short-circuit detection, as far as possible without additional intervention in existing signal power distributors. This object is solved by the features of the independent claim.

Advantages of the invention

The device according to the invention for fault detection in a multi-voltage electrical system comprises a detection device which detects a supply potential with which a power distributor for supplying energy is supplied and which supplies at least one electrical load with energy via an output. Furthermore, a further detection device is provided which detects the output potential at the output. Error detection means are provided which generate an error signal if the output potential deviates from the supply potential by a certain value. In particular, by comparing the supply voltage and the output voltage, a high-resistance short circuit between a first voltage level can also be found (for example 42V) and a second voltage level (for example 14V) can be recognized. The voltage evaluation also significantly reduces the effort for the measurement value acquisition, since in contrast to a current measurement the wiring harness does not have to be opened. Furthermore, a special measuring resistor does not have to be provided for every consumer. In addition, in contrast to a current measurement, you do not have to rely on the flow of a reverse current.

In an expedient development, the device for error detection in a multi-voltage on-board network detects further output potentials, with which further loads are supplied with energy by the power distributor, for comparison with the supply potential. The output signals of the corresponding error detection are OR-linked. If an output potential now exceeds the supply potential, this indicates a short circuit. In this case, a corresponding error signal is generated, which can be evaluated to initiate countermeasures. This OR connection reduces the wiring effort. Only one signal line can be used for the forwarding of the error signal, for example to a higher-level power distributor. The hardware expenditure is minimized.

In an expedient development, the device for error detection comprises a power supply for the error detection means. Thus, a comparator can be used as error detection means, which carries out the potential comparison. To reduce the quiescent current consumption, a switching means is provided which activates or deactivates the energy supply. This switching means can be activated via the same signal line via which the error signal is also discharged. In this way, during the start-up phase (desired start of the power vehicle) an activation signal to start the device for error detection. If the device for error detection reaches its normal operating state, this external activation signal is no longer necessary. The corresponding supply line can then be used for other purposes. This arrangement further simplifies the construction of the device for error detection.

In an expedient development, it is provided that at least one further device for fault detection monitors the output potential of a further power distributor. The output error signal is hard-wired or linked to the error signal of the first device for error detection for forwarding to a higher-level evaluation unit.

According to an expedient development, the error signal is binary. If the output potential exceeds the supply potential by a certain value for the first time, the signal changes from the logical 1 state to the logical 0 state. When the signal state changes, a timer is started for a specifiable period of time. If, after this period of time has elapsed, the error signal is still at a level that is characteristic of the error state, countermeasures are only then initiated. This initial masking out of the error detection for a predefinable period of time means that short-term voltage peaks, combined with possible retention processes by electrical consumers, do not trigger an error handling routine. This improves error detection.

Further expedient further developments result from further dependent claims and from the description. drawing

An embodiment of the device for error detection in a multi-voltage electrical system is shown in the figures and is described in more detail below.

FIG. 1 shows a structural arrangement of the device for error detection in a multi-voltage electrical system, FIG. 2 shows a precise illustration of the device for error detection, and FIG. 3 shows possible interconnections in several devices for error detection.

Description of the embodiment

A 14V signal power distributor 16 is supplied with a supply potential UO via a 14V supply voltage input 17. The 14 V supply voltage input 17 is connected on the one hand to a DC / DC converter 7 and to the positive pole of a first battery 14. The first battery 14 is also connected to ground 15. Several components are shown in the 14V signal power distributor 16 as examples. A voltage limiter 11 is used for overvoltage protection. A 14 V load 22 can be connected to the supply potential via a switching means 18. An output potential U1 of the first output 9 can be tapped at the associated first output 9, via which the 14 V load is supplied. The 14V load 22 is connected to ground 15. A second load 22b is secured by a fuse 13. Another 14V load 22c can be controlled via a relay 12. The 14V signal power distributor 16 exchanges data via a bus system 20. The output potential U1 at the first output 9 is fed to an error detection 10, as is the supply potential UO. A comparator 24 is arranged in the error detection 10 and compares the supply potential UO and the output potential U1 and generates an error signal 26 as a function of the comparison. This error signal 26 is fed to a 42V signal power distributor 28 via a signal line. This contains a time monitor 25, which evaluates the incoming error signal 26 only after a period of time for a characteristic error state. The output signal of the time monitor 25 is fed to a microcontroller 31 which, depending on this output signal, initiates possible countermeasures, for example in connection with a data exchange via the bus system 20. The time monitor 25 can also be implemented directly by the microcontroller 31, for example. A short circuit resistor 19 is intended to symbolize a possible short circuit to be detected between the 14 V voltage level and the 42 V voltage level. The 42V

Signal power distributor 28 further comprises two switching means 21, which could be activated, for example, via the microcontroller 31. The 42V signal power distributor 28 is supplied with 42V on the input side via the 42V supply input 5. A 42V load 23 can each be supplied with energy via the switching means 21. The 42V supply voltage is made available in connection with a second battery 6 and a generator 8 connected in parallel thereto and is connected to the 14V voltage level via the DC / DC converter 7.

The error detection 10 is shown in more detail in FIG. The error detection 10 is supplied with the supply potential UO via the input 17 and the first output potential U1 via the input 9. The two inputs 9, 17 are coupled to a first diode 30, which is polarized in such a way that, at a more positive supply potential U0 than the first output potential U1, the first diode 30 is polarized in the reverse direction. The supply potential U0 reaches a switching unit 33 or the emitter-collector path of a trans stors 34 on the one hand to a supply voltage generator 39. This comprises a third resistor 40, via which the supply potential UO is connected to a parallel connection of a first capacitor 42, a diode 44 and a second capacitor 46, connected to ground. The internal supply voltage VCC is provided as the output variable of the supply voltage generator 39. Furthermore, a voltage divider, consisting of a first resistor 36 and a second resistor 38, is provided, via which the supply potential UO is divided down into the operating voltage range of a first comparator 54. Thus, a voltage proportional to the supply potential UO is present at the non-inverting input of the first comparator 54 and - connected in parallel to this - at a non-inverting input of a second comparator 62. The output potential U1 of the first output 9 is divided down into the operating voltage range of the first comparator 54 via a further voltage divider, consisting of a fourth resistor 48 and a fifth resistor 50. A voltage proportional to the output potential U1 of the first output is thus applied to the inverting input of the first comparator 54. The second output potential U2 is fed via a further input to the error detection 10 and a further voltage divider, consisting of a sixth resistor 56 and a seventh resistor 58, is divided down into the operation of the voltage range of the second comparator 62, so that at the inverting input of the second comparator 62 a voltage proportional to the second output potential U2 of the second output is present. Capacitors 52, 60 are connected between the inverting and non-inverting inputs of the comparators 54, 62 for filtering transients. If one of the output potentials U1, U2 rises above the supply potential UO, at least one of the comparators 54, 62 inputs Error signal 26 from the state Logical 0 corresponds. In the example, the comparators 54, 62 are designed as open-collector comparators, which pull the output of the comparators 54, 62 to ground potential when the supply potential UO is exceeded by one of the output potentials U1, U2. The outputs of the two comparators 54, 62 are connected to one another in an electrically conductive manner, so that a hard-wired logic-or link (wired-or) is implemented in connection with the open collector outputs. The output signals of the comparators 54, 62 linked in this way are led out of the error detection 10 via the error signal 26. The corresponding signal line, on the other hand, is used as an input which is electrically conductively connected to the base of the transistor 34 in order to control the switching unit 33.

According to FIG. 3, two 14V signal power distributors 16a, 16b are now provided, each of which takes over the energy supply for 8 loads, 22a.1-8, 22b.1-8. Each of these MV signal power distributors 16a, 16b is assigned an error detection 10a, 10b, each of which evaluates the output potentials U1 to U8 for error detection. Furthermore, these error detections 10a, 10b are each supplied with the supply potential U0 of 14V (terminal 30) and the ground potential 15 (terminal 31). The error signals 26a, 26b of the error detections 10a, 10b are connected to one another in an electrically conductive manner and are supplied to the 42V signal power distributor 28 as an error signal 26. This is supplied with 42V and activates a 42V load (not shown) via the 42V output 29, which can also be controlled externally by another switching means if necessary. The lightning symbolizes a short circuit to be detected between the 42V consumer level and the 14V consumer level.

Initially, the error detection device is in idle mode. Here, the switching unit 33 is transistor 34 controlled so that no electrically conductive connection between the 14V

Supply voltage input 17 and the input of the supply voltage generator 39. The line via which the error signal 26 is communicated in the normal state is correspondingly high-impedance. The microcontroller 31 of the 42V signal power distributor 28 now generates a corresponding command signal for the control unit 27 in connection with a corresponding activation command, which was communicated via the bus system 20 or was detected by the 42V signal power distributor 28 itself. The control unit 27 then brings the line 26 to an operational level, whereby the transistor 34 of the switching unit 33 is switched to the on state. This also activates the supply voltage generator 39, which then provides an internal supply voltage VCC of, for example, 5V at its output for the two comparators 54, 62. Thus, the comparators 54, 62 are also ready for operation as error detection means.

The first comparator 54 compares whether the first output potential U1 exceeds the supply potential UO by a certain value, for example by 0.7V. This value corresponds to the voltage drop across the inverse diode of the semiconductor 18 in the reverse direction. This value can be set accordingly via the voltage dividers formed by resistors 36, 38 and 48, 50. These voltage dividers also serve to bring the voltages UO, Ul to be detected into the operating range of the comparator 54. The outputs of the comparators 54, 62 are designed as open collector outputs. If the first output potential U1 exceeds the supply potential UO by the predeterminable value, the output of the first comparator 54 changes its state from logic 1 to logic 0. In the state logic 0, the output of the comparator 54 is grounded. pulled, even if the output of the second comparator 62 still has a value of logic 1. As a result, the error signal 26 changes the state from logic 1 to logic 0. A possible short circuit between the 14 V voltage level and the 42 V voltage level is thus detected, since, in the normal case, the output potential Ul of the 14 V load 22 is always lower than the potential of the MV Supply input 17. Exceeding the supply potential UO could only be possible with the short-circuit mentioned.

For further evaluation, the error signal 26 is fed to the 42V signal power distributor 28. The time monitor 25 detects the edge change occurring in the event of an error from the logic 1 signal state to logic 0 and then starts a timer for, for example, 5 ms to 1 s. An error signal of logic 0 which lies within this time period and indicates an error is still ignored by the microcontroller 31. This suppresses in particular surge peaks that could occur, for example, when the 14 V loads 22 are switched on / off. However, if the error signal 26 still has a characteristic error state after this predeterminable time period, ie if it is still at the logical 0 value, the microcontroller 31 detects a possible short circuit. The microcontroller 31 then initiates diagnostic and troubleshooting measures. For example, provision could be made to display a corresponding error message via the bus system 20. To protect consumers 22, 23, it could also be provided to switch off the source and / or consumers 22, 23. These consumers could also be switched off one after the other for diagnosis. If the first output potential Ul then falls below the supply potential U0 again, the error signal 26 changes its logic state from 0 to 1 and signal Based on the microcontroller 31, the error was successfully eliminated. The microcontroller 31 stores which load 23 was last activated and thus presumably caused the short circuit. This is output in a diagnostic cycle.

In principle, the circuit shown in FIG. 2 can be used to compare any number of output potentials Ul to Un with the corresponding supply potential UO of the signal power distributor 16. If one of the output potentials Ul to Un exceeds the supply potential UO, the error signal 26 assumes the state which is characteristic of an error (logic 0). A corresponding cascaded arrangement is shown in FIG. 3. Each 14V signal power distributor 16a, 16b is assigned an error detection 10a, 10b, which is constructed as described in FIG. Each output potential Ul to Un is thus monitored by comparison with the supply potential UO. The respective error signals 26a, 26b are electrically conductively linked and fed to the 42V signal power distributor 28 for evaluation according to FIG. 1.

The error detection 10 is designed as a separate unit. The existing 14V

Signal power distributors 16a, 16b are kept unchanged and retrofitted by the corresponding error detections 10a, 10b. The outputs of the 14V loads 22 can be tapped very easily on the wiring harness of the 14V load circuits (for example by insulation displacement connections, branch connectors, intermediate plugs). The supply potential U0 should preferably be tapped in the immediate vicinity of the input 17. In principle, however, it would also be possible to integrate the error detection 10 into the corresponding signal power distributor 16. The diodes 30, 32 arranged between the output potentials U1, U2 and the supply potential UO are intended to serve as an additional protection if, for example, no inverse diode of a switching means 12 is provided, via which a reverse current could otherwise flow briefly in the event of a fault. This would protect the affected consumers 22, in particular in the event of a low-resistance short circuit.

The device for fault detection is particularly suitable for a multi-voltage electrical system, since there is a relatively high risk of a short circuit. Such multi-voltage electrical systems are particularly intended for applications in motor vehicles.

Claims

claims

1. Device for fault detection in a multi-voltage on-board network, comprising a detection device (10) that detects a supply potential (UO) with which a power distributor (16) is applied, which has at least one electrical load (22) via at least one output (9) Energy is supplied with a further detection device (10), which detects the output potential (Ul) at the output (9), with error detection means (24), which generate an error signal (26) when the output potential (Ul) from the supply potential (UO) deviates by a certain value.

2. Device according to claim 1, characterized in that at least one energy supply (39) is provided for the error detection means (24).

3. Device according to one of the preceding claims, characterized in that at least one switching means (33, 34) is provided which activates or deactivates the energy supply (39).

4. Device according to one of the preceding claims, characterized in that the error signal (26) one Power distributor (28) is fed for further error evaluation.

5. Device according to one of the preceding claims, characterized in that a monitoring device (25, 31) is provided which evaluates the error signal (26) to determine whether it assumes a characteristic of an error case after a predeterminable period of time.

6. Device according to one of the preceding claims, characterized in that the monitoring device (25, 31) initiates countermeasures for fault diagnosis and / or rectification if the fault signal (26) assumes a characteristic value for the fault in the predeterminable period of time.

7. Device according to one of the preceding claims, characterized in that electrical loads (23, 22) are switched off as countermeasures.

8. Device according to one of the preceding claims, characterized in that a comparator (54, 62) is provided as error detection means.

9. Device according to one of the preceding claims, characterized in that a diode (30, 32) is arranged between supply potential (UO) and output potential (U1).

10.Device according to one of the preceding claims, characterized in that at least one further output potential (U2) of a further output (9) is fed to an error detection means (62) for comparison with the supply potential (UO).

11. Device according to one of the preceding claims, characterized in that the outputs of the at least two comparators (54, 62) are electrically conductively connected to one another.

12.Device according to one of the preceding claims, characterized in that the switching unit (33) is controlled via the same line via which the error signal (26) is conducted.