MEMS RELAY WITH SAFETY FUNCTION

Abstract

A micromechanical electrically actuable switch. The switch has a first relay with a first operating contact, and a second relay with a second operating contact. The first operating contact and the second operating contact are arranged in series in a common load path. The switch further includes a detection device for detecting a switching state of the first operating contact, and a control circuit for registering the switching state of the first operating contact and for switching on the electrically actuable switch. The control circuit is configured, upon a switch-on signal, to switch on the first relay and the second relay in a first case, in which the switching state of the first operating contact is open, and to not switch on at least the second relay in a second case, in which the switching state of the first operating contact is closed.

Claims

1. A micromechanical electrically actuable switch, comprising: a first relay with a first operating contact; a second relay with a second operating contact, the first operating contact and the second operating contact being arranged in series in a common load path; a detection device configured to detect a switching state of the first operating contact; a control circuit configured to register the switching state of the first operating contact and to switch on the electrically actuable switch, and the control circuit being configured to, upon a switch-on signal: switch on the first relay and the second relay in a first case, in which the switching state of the first operating contact is open, and to not switch on at least the second relay in a second case, in which the switching state of the first operating contact is closed.

2. The micromechanical electrically actuable switch as recited in claim 1, wherein the first operating contact can be actuated by a first actuator and a first resetting spring and the second operating contact can be actuated by a second actuator and a second resetting spring.

3. The micromechanical electrically actuable switch as recited in claim 2, wherein the first actuator and the second actuator are configured as a capacitive drive.

4. The micromechanical electrically actuable switch as recited claim 1, wherein the second operating contact has a shorter operate time than the first operating contact, and the first operating contact has a shorter release time than the second operating contact.

5. The micromechanical electrically actuable switch as recited in claim 2, wherein the second resetting spring has a higher spring constant than the first resetting spring.

6. The micromechanical electrically actuable switch as recited in claim 2, wherein the first actuator has a first drive electrode, the second actuator has a second drive electrode, and the second drive electrode is larger than the first drive electrode.

7. The micromechanical electrically actuable switch as recited in claim 1, wherein, in the switching state closed, the second operating contact has a greater electrical conductivity than the first operating contact.

8. The micromechanical electrically actuable switch as recited in claim 1, wherein the detection device is configured for capacitive detection of the switching state of at least the first operating contact and has a detection electrode.

9. The micromechanical electrically actuable switch as recited in claim 1, wherein the control circuit is configured to output an error signal relating to an error of the first relay in the second case.

10. The micromechanical electrically actuable switch as recited in claim 1, wherein the first relay is integrated with the second relay in a common MEMS relay module on a common micromechanical substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows a schematic representation of a MEMS relay according to an example embodiment of the present invention, with a safety function.

[0027] FIG. 2 shows a schematic circuit diagram of a MEMS relay according to an example embodiment of the present invention, with a safety function.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0028] FIG. 1 shows an exemplary layout of the relay according to the present invention. A control circuit 7 and a MEMS relay module 8 with two relays are arranged in a housing 6. The two relays are connected in series. In a first relay 10, a smaller drive electrode 130 is provided for a first capacitively operating actuator 13. A first resetting spring 12 in the first relay is somewhat harder. The remaining surface near to the first drive electrode is used for a detection electrode 15. A position of the movable element of the first operating contact is detected capacitively by the detection electrode and the switching state is determined from this.

[0029] In a second relay 20, which serves as security in case the first relay fails, a second drive electrode 240, which is relatively large compared to the first drive electrode, is provided for a second actuator 24. If both drive electrodes are connected at the same time, the second relay closes first and is therefore not under load as a result of the connection procedure. In the second relay, a second resetting spring 22 is configured to be somewhat softer than the first resetting spring 12. If both drive electrodes are disconnected at the same time, the first relay opens first and is, in turn, under further load as a result of the disconnection procedure. If the first relay fails, i.e. the first operating contact remains in the switching state closed and therefore remains in the always-on state, this is identified by the control circuit through analysis of the signal of the detection electrode and the control circuit ensures that, from now on, the second relay always remains open. (Only a selection of individual electrical connections is shown in the figure).

[0030] FIG. 2 shows a schematic circuit diagram of a MEMS relay according to the present invention, with a safety function. This shows an electrically actuable switch having a first relay 10 with a first operating contact 11, having a second relay 20 with a second operating contact 21, a detection device 15 for detecting a switching state of the first operating contact and a control circuit 7 for registering the switching state of the first operating contact and for switching on the electrically actuable switch. The first operating contact and the second operating contact are arranged in series in a common load path 100. The control circuit is designed, upon a switch-on signal 50, to switch on the first relay and the second relay in a first case, in which the switching state of the first operating contact is open, and to not switch on at least the second relay in a second case, in which the switching state of the first operating contact is closed. To this end, the control circuit outputs a first relay switching signal 30 and a second relay switching signal 40.

[0031] In an alternative exemplary embodiment (not depicted), a common relay switching signal is provided for both relays.

[0032] In an alternative exemplary embodiment (not depicted), a further detection device for also detecting a switching state of the second operating contact is further provided. In this example, the control circuit is also designed accordingly for registering the switching state of the second operating contact. [0033] List of reference signs: [0034] 10 First relay [0035] 11 First operating contact [0036] 12 First resetting spring [0037] 13 First actuator [0038] 15 Detection device [0039] 20 Second relay [0040] 21 Second operating contact [0041] 22 Second resetting spring [0042] 24 Second actuator [0043] 30 First relay switching signal [0044] 40 Second relay switching signal [0045] 50 Switch-on signal [0046] 6 Housing [0047] 7 Control circuit [0048] 8 MEMS relay module [0049] 100 Load path [0050] 130 First drive electrode [0051] 150 Detection electrode [0052] 240 Second drive electrode