Vehicle On-Board Electrical Network Switch for Motor Vehicles, On-Board Electrical Network for Motor Vehicles and Method for Operating an On-Board Electrical Network Switch for Motor Vehicles

Abstract

Motor vehicle on-board electrical network switch having at least two inputs for a respective one of at least two on-board power supplies, at least one output for a load of the motor vehicle, at least two switches, a first switch being disposed between a first of the inputs and a common node, and a second switch being disposed between a second of the inputs and the common node, and the output being electrically connected to the common node, wherein the switches are formed as semiconductor switches and are respectively connected with their body diodes in forward direction towards the common node, characterized in that a monitoring circuit monitors a first voltage at the first input and/or a second voltage at the second input and/or a voltage at the common node, and in that the monitoring circuit causes an opening signal for simultaneous opening of both switches depending on an amount of at least one of the monitored voltages.

Claims

1-15. (canceled)

16. Motor vehicle on-board electrical network switch comprising: at least two inputs for respectively one of at least two on-board power supplies; at least one output for a load of the motor vehicle; a first switch disposed between a first of the inputs and a common node; a second switch disposed between a second of said inputs and said common node; wherein the at least one output is electrically connected to the common node, wherein the first and second switches are semiconductor switches and are respectively connected with their body diodes in forward direction towards the common node, wherein a monitoring circuit monitors a first voltage at the first input and/or a second voltage at the second input and/or a voltage at the common node, and in that the monitoring circuit triggers an opening signal for simultaneous opening of both switches as a function of a magnitude of at least one of the monitored voltages.

17. Motor vehicle on-board electrical network switch according to claim 16, wherein the monitoring circuit triggers the opening signal when at least one of the voltages falls below a limit value.

18. Motor vehicle on-board electrical network switch according to claim 16, wherein the monitoring circuit triggers the opening signal in the event of a short circuit at at least one of the inputs.

19. Motor vehicle on-board electrical network switch according to claim 16, wherein the monitoring circuit compares at least one of the voltages with a comparison potential, in particular a ground potential.

20. Motor vehicle on-board electrical network switch according to claim 16, wherein the monitoring circuit evaluates a respective state of a part of the vehicle electrical network at the first input and of a part of the vehicle electrical network at the second input immediately after the opening signal is triggered and, depending on the evaluation, triggers a closing signal for one, preferably only the first or only the second switch.

21. Motor vehicle on-board electrical network switch according to claim 20, wherein the monitoring circuit evaluates a mains impedance and/or a voltage and/or an impulse response at the part of the vehicle electrical network at the first input and the part of the vehicle electrical network at the second input.

22. Motor vehicle on-board electrical network switch according to claim 16, wherein the semiconductor switches are dimensioned in such a way that a voltage drop at a respective body diode after the switch is opened is less than 1 V, preferably less than 0.7 V.

23. Motor vehicle on-board electrical network switch according to claim 16, wherein the monitoring circuit is configured to trigger the closing signal within 100 ms, preferably 40 ms, after the opening signal.

24. Motor vehicle on-board electrical network switch according to claim 16, wherein after opening of the switches, the output is conductively connected to the first and second inputs via the respective body diodes, and the body diodes enable a current flow from the respective input to the output.

25. Motor vehicle on-board electrical network switch according to claim 16, wherein after opening of the switches, the output is conductively connected to the first and the second input via the respective body diodes and the body diodes block a current flow from the output to the respective input.

26. Motor vehicle on-board electrical network switch according to claim 16, wherein at least one of the semiconductor switches is connected with a variable switching characteristic, in particular in that the switching characteristic is dependent on a load at the output.

27. Motor vehicle on-board electrical network switch according to claim 16, wherein a safety-relevant load is connected to the output.

28. Motor vehicle on-board electrical network switch according to claim 16, wherein the output is short-circuited to the common node.

29. Motor vehicle electrical network comprising: a motor vehicle on-board electrical network switch according to claim 16; a first on-board electrical power supply connected to the first input; a second on-board electrical power supply connected to the second input; and a safety-relevant load connected to the output.

30. Method of operating a motor vehicle on-board electrical network switch according to claim 16, comprising: monitoring a first voltage at the first input and/or a second voltage at the second input and/or a voltage at the common node and, depending on a magnitude of at least one of the monitored voltages, both switches are opened simultaneously, wherein, after the simultaneous opening of the two switches, the body diodes of the two switches connect a respective potential of the on-board electrical network to the output in the forward direction, wherein, after the simultaneous opening of the two switches, the electrical state of the two on-board power supplies is evaluated and, depending on the evaluation, one of the two switches is closed.

Description

[0053] In the following, the subject matter is explained in more detail with reference to a drawing showing embodiments. In the drawing show:

[0054] FIG. 1a block diagram according to an embodiment;

[0055] FIGS. 2a, b voltage curves at the common node;

[0056] FIGS. 3 a-f switching states of a motor vehicle on-board electrical network switch according to embodiments.

[0057] FIG. 1 shows a motor vehicle on-board electrical network switch 2 in a motor vehicle on-board electrical network. The motor vehicle on-board electrical network switch 2 has two switches 4, 6. The first switch 4 is connected to a first vehicle electrical network power supply 16 via an input contact 10. The second switch 6 is connected to a second on-board electrical network 20 via an input contact 8. The switches 4, 6 are short-circuited to each other within the vehicle electrical network switch 2 via a common node 12. The node 12 is connected to an output contact 14.

[0058] The input contacts 8, 10 and the output contact 14 can be formed as connection lugs, connection terminals, plug-in contacts, crimp contacts, connection bolts, welding lugs, soldering lugs or the like.

[0059] The first on-board electrical network 16 is, for example, a DC/DC converter connected at its high-side potential 16a to the input contact 10.

[0060] The second on-board electrical network 20 is, for example, a battery connected on its B+ potential 20a to the input contact 8 and connected on its B- contact 20b to ground 22.

[0061] The second on-board electrical network 20 supplies an on-board electrical network 24, for example. The first on-board electrical network 16 can also supply an on-board electrical network, but this is not shown.

[0062] A load 25 is connected to the output contact 14. The load 25 is, for example, a safety-relevant load.

[0063] The switches 4, 6 in the motor vehicle on-board electrical network switch 2 each comprise a switching element 4b, 6b and a body diode 4a, 6a. The switches 4, 6 are, for example, semiconductor switches, in particular high-power semiconductor switches, for example MOSFETs, IGBTs or the like.

[0064] In FIG. 1, it can be seen that the body diodes 4a, 6a are each switched in the forward direction from an input contact 8, 10 toward the common node 12.

[0065] The switching elements 4b, 6b can be controlled via a switching signal (not shown). Such actuation can be performed, for example, via a monitoring circuit 26. The switches 4a, 4b may be Normally Opened (NO), for example, and an open signal may be a decrease in a switching signal level. The switching elements 4b, 6b may also be Normally Closed (NC) and an open signal may be an increase in a switching signal level.

[0066] The monitoring circuit 26 is connected to the common node 12 via a sense line 26a and may, for example, measure the potential of the common node 12 with respect to ground 22. In addition, the monitoring circuit 26 is connected to the respective on-board power supplies at the on-board power supplies 16, 20 via sensing lines 26b, c. The sensing lines 26b, c can be used to determine a condition of the respective on-board electrical network, such as an impedance, an impulse response, a resistance to ground, or the like.

[0067] With the aid of the motor vehicle on-board electrical network switch 2 shown, it is possible to connect the safety-relevant load 25 redundantly and permanently to at least one of the on-board power supplies 16, 20, even in the event of a fault.

[0068] Such a fault case is shown in FIG. 2a. FIG. 2a shows exemplarily and purely schematically a voltage curve 28 at the common node 12. A standard voltage 32 is present at the common node 12 in the normal case. In the normal case, the switching elements 4b, 6b are closed. The standard voltage 32 results from the respective higher potential of one of the two on-board power supplies 16, 20.

[0069] In the event of a fault, the edge 30 in the voltage 28 drops steeply. This can occur, for example, at time 36. The steeply falling edge 30 causes the voltage 28 to fall below a lower limit value 34. In conventional circuits, it takes until time 38 for the faulty on-board electrical network 16, 20 to be disconnected from the common node. In this case, time point 38 may be, for example, 40 to 100 ms after time point 36. The interval between the time points 36, 38 is above the maximum permissible duration of a voltage dip below the limit value 34 for a safety-relevant load, e.g. 0.5 ms.

[0070] By falling below the lower limit value 34 for more than 0.5 ms, a fault of the safety-relevant load 25 can no longer be excluded.

[0071] This can be remedied by a motor vehicle on-board electrical network switch 2 in which a voltage curve 40 as shown in FIG. 2b can be implemented. FIG. 2b is described in connection with FIGS. 3a to f.

[0072] In FIG. 3a, it can be seen that the switching elements 4b, 6b are closed. This is the normal state. The standard voltage 32 flows from the on-board power supplies 16, 20 via the switching elements 4b, 6b and the common node 12 to the load 25.

[0073] FIG. 3b shows that a fault, for example a short circuit 42, 44, can occur on the side of one of the two on-board power supplies 16, 20, starting from the input contacts 8, 10. In such a case, the edge 30 of the voltage 40 drops steeply. This steep slope 30 can be detected via the monitoring circuit 26. This detection can be completed very quickly after the time 36 at the time 37. In this case, both switching elements 4b, 6b are opened immediately by the monitoring circuit 26. In particular, time point 37 is at most 0.5 ms after time point 36. Since it is not known which of the short circuits 42, 44 has occurred, both switching elements 4a, 6a are initially opened.

[0074] FIG. 3c shows an example in which a short circuit 42 has occurred on the side of the on-board electrical network 20. After both switching elements 4b, 6b have been opened by the monitoring circuit 26, as shown in FIG. 3c, a current flow 46 can still flow from the positive pole 16a of the on-board electrical network 16 via the body diode 4a to the load 25. This is shown in FIG. 2b. There it can be seen that after the falling edge 30 at time 37, the voltage 40 stabilizes again. The voltage 40 is 0.7 to 1 V below the standard voltage 32, which is due to the voltage drop across the body diode 4a.

[0075] In the period between times 36, 38, the monitoring circuit 26 can measure and evaluate where the fault is via the sensing lines 26b, c in the respective on-board power supplies 16, 20.

[0076] In FIG. 3d, it is shown that the fault has been sensed on the side of the on-board electrical network 20. In this case, the switching element 4b is closed. As can be seen in FIG. 3d, the current flow 48 occurs via the switching element 4b.

[0077] In FIG. 3b, it can be seen that this results in an increase in voltage 40 to standard voltage 32 at time 38, i.e. when it has been determined where the fault is located. In FIG. 3b it can be seen that at no time did the voltage fall below the limit 34.

[0078] FIG. 3e shows a case in which the short circuit 44 has occurred on the side of the on-board electrical network 16. This short circuit 44 also leads to a falling edge 30 and immediate opening of the switching elements 4b, 6b. Since the on-board electrical network 20 is still operating fault-free, this leads to a current flow 46 across the body diode 6a, as shown in FIG. 3e. The voltage waveform is as shown in FIG. 2b.

[0079] As described for FIG. 3c, the monitoring circuit 26 is used to measure into the two on-board circuits beyond the input contacts 8, 10 and to evaluate on which side the fault lies.

[0080] If the fault is on the side of the on-board electrical network 16, the switching element 6b can be closed again, as shown in FIG. 3f. This is time 38. A current flow 48 takes place from the on-board electrical network 20 via the switching element 6b to the load 25. Here, too, it is ensured that at no time does the voltage fall below the limit value 34.

[0081] With the aid of the arrangement shown, it is possible to design a redundant on-board electrical network in such a way that a voltage drop below a critical limit value for safety-relevant loads is avoided.