Switch device for electrically activating and deactivating an electric load which can be connected to a DC voltage supply device, and method for operating such a switch device

Abstract

The invention relates to, among others, a switch device (10) for electrically activating and deactivating an electric load (110) which can be connected to a DC voltage supply device (20), having: - a first and a second energy supply connection (11, 12), to which an external DC voltage supply device (120) can be connected, - a first and second output connection (16, 17), to which an electric load (110) can be connected, - a first current path (18) which is electrically connected to the first energy supply connection (11) and the first output connection (16), wherein a parallel circuit (50) is arranged in the first current path (18), said parallel circuit having a first actuatable semiconductor switch (90), a voltage detection device (130), and a mechanical switch contact (82) of a first electromechanical switch (80), and - a control and analysis device (70) which is designed to monitor voltage values supplied by the voltage detection device (130) during operation and detect a malfunction of the first electromechanical switch (80) if the monitored voltage values change in a specified manner.

Description

[0001] Switching device for electrically switching on and off an electrical load connectable to a DC voltage supply device and method for operating such a switching device

[0002] Description

[0003] The invention relates to a switching device for electrically switching on and off an electrical load connectable to a DC voltage supply device and to a method for operating such a switching device.

[0004] Switching devices with a hybrid output stage are known, which comprise a parallel circuit of an electromechanical switch and a semiconductor switch. Typically, a relay or contactor, which can also be referred to as a bypass contactor or relay, is used as the electromechanical switch. Using the hybrid output stage, an electrical load connectable to the switching device can be electrically connected to or disconnected from an external power supply, thereby enabling the electrical load to be switched on or off. Such a switching device, designed for AC operation, is known, for example, from WO 2014 / 032718 A1.

[0005] In a switching device with a hybrid output stage, malfunctions can be caused, for example, by mechanical shock loads resulting from external influences on the switching device causing the mechanical contacts to separate in an uncontrolled manner, resulting in arcs that can destroy the mechanical contacts. There is also a risk that an uncontrolled opening of the mechanical switching contacts could inadvertently disconnect an electrical load connected to the switching device.

[0006] The object of the present invention is to provide a switching device for electrically switching on and off an electrical load that can be connected to a DC voltage supply device, as well as a method that makes it possible to prevent damage to a mechanical switching contact of a hybrid output stage of the switching device and uncontrolled switching off of an electrical load that can be connected to the switching device, in particular in the event of undesired opening or bouncing of the mechanical switching contact.

[0007] A core idea of ​​the invention can be seen in the creation of a switching device for electrically switching on and off an electrical load that can be connected to a DC voltage supply device, wherein the switching device has a hybrid output stage, i.e. a parallel circuit comprising a semiconductor switch and a mechanical switch of an electromechanical switch. The switching device or a control and evaluation device of the switching device is designed to detect, in particular, an uncontrolled opening or bouncing of the electromechanical switch of the hybrid output stage during operation. This can be achieved with the aid of a voltage detection device assigned to the hybrid output stage, which can signal a fault in the electromechanical switch to the control and evaluation device during operation, i.e. when the switching device is switched on.

[0008] The above-mentioned technical problem is solved in particular by the features of claim 1.

[0009] Accordingly, a switching device is provided, in particular for electrically switching on and off an electrical load that can be connected to a DC voltage supply device, which can have the following features:

[0010] - a first and a second power supply connection to which an external DC voltage supply device can be connected,

[0011] - a first and second output terminal to which an electrical load can be connected,

[0012] - a first current path electrically connected to the first power supply terminal and the first output terminal, wherein a parallel circuit is arranged in the first current path, which circuit has a first controllable semiconductor switch, a voltage detection device and a mechanical switching contact of a first electromechanical switch,

[0013] - a second current path electrically connected to the second power supply terminal and the second output terminal,

[0014] - a control and evaluation device connected to the voltage detection device, wherein the control and evaluation device is designed to monitor the voltage values ​​preferably continuously supplied by the voltage detection device during operation and to detect a malfunction of the first electromechanical switch when the monitored voltage values ​​change in a predetermined manner.

[0015] In this way, the control and evaluation device can detect a fault in the electromechanical switch. Depending on the implementation, the switching device could report this condition, for example, to a higher-level device so that appropriate measures can be taken.

[0016] According to an advantageous embodiment, the control and evaluation device can be designed, in particular during a switch-on process, first to switch the first semiconductor switch electrically conductive and to temporarily store a first voltage value supplied by the voltage detection device, and after a predetermined period of time to close the mechanical switching contact of the first electromechanical switch and to temporarily store a second voltage value supplied by the voltage detection device, which is smaller than the first voltage value, and then, ie in particular after successful completion of the switch-on process orDuring operation, the voltage values ​​preferably continuously supplied by the voltage detection device are monitored and a malfunction of the first electromechanical switch is detected if the monitored voltage values ​​exceed the second voltage value, in particular by a predetermined amount. In this way, the control and evaluation device can detect a malfunction of the electromechanical switch.

[0017] A malfunction of the first electromechanical switch occurs in particular when the mechanical switching contact of the first electromechanical switch opens uncontrollably, for example due to vibrations of the switching device.

[0018] Depending on the implementation of the parallel circuit, the first voltage value can be, for example, 2 V and the second voltage value can be approximately 0 V during proper operation.

[0019] Advantageously, the voltage detection device is designed in particular to detect the voltage value of a voltage drop across the parallel circuit and to supply this voltage value to the control and evaluation device for evaluation.

[0020] It should be noted that the term “during operation” refers in particular to the switched-on state of the switching device.

[0021] If the monitored voltage values ​​exceed the second voltage value, the control and evaluation device detects that a fault has occurred in the first electromechanical switch. In particular, if the mechanical switching contact of the first electromechanical switch opens uncontrollably during operation, the monitored voltage value at the parallel circuit will, for example, rise almost back to the first voltage value.

[0022] The control and evaluation device is advantageously designed to detect or record a fault or malfunction of the electromechanical switch when the monitored voltage values ​​exceed the second voltage value by a predetermined amount, which may be less than the first voltage value. According to an advantageous implementation, the control and evaluation device can be designed not only to close the mechanical switching contact of the first electromechanical switch after the predetermined period of time, but also to switch the first semiconductor switch to an electrically blocking state after the mechanical switching contact of the first electromechanical switch has closed. In this case, the control and evaluation device is further designed to switch the first semiconductor switch electrically conductive again during operation when an increase in the monitored voltage value above the second voltage value is detected.

[0023] Thanks to these measures, it is ensured that in the event of an uncontrolled opening of the mechanical switching contact of the first electromechanical switch during operation, the current flowing in the first current path is immediately or without harmful time delay conducted via the first semiconductor switch, i.e. is commutated to the first semiconductor.

[0024] Advantageously, the control and evaluation device can be designed as a microcontroller.

[0025] Conveniently, the first voltage value, the second voltage value, optionally a threshold value corresponding to the defined amount by which the monitored voltage value should exceed the second voltage value in the event of a fault, and / or the predetermined time period can be stored in a memory device, which can be implemented in the control and evaluation device or as a separate memory module. The control and evaluation device can access these values ​​in order to be able to control the switching device in the manner described above.

[0026] According to an exemplary and cost-effective embodiment, the voltage detection device comprises an electrical voltage divider.

[0027] To determine whether a load current is flowing, a current measuring device can be arranged in the first current path or in the second current path and electrically connected to the control and evaluation device. The current measuring device can be designed as a current sensor. To be able to disconnect the electrical load from the DC voltage supply device in the event of a failure or undesired drop in the supply voltage of the switching device, the switching device can, for example, have a detection device, an electrical energy store designed for the device-internal power supply, and a voltage supply device connected to the first and second power supply terminals, which is electrically connected to the electrical energy store and the detection device.The detection device is preferably designed to detect the drop in a DC voltage present at the output of the voltage supply device below a predetermined threshold value, wherein the control and evaluation device is preferably designed to carry out a switch-off process for switching off an electrical load connectable to the first and second output terminals in response to a drop in a DC voltage present at the output of the voltage supply device below the predetermined threshold value detected by the detection device.

[0028] According to an advantageous embodiment, the switching device can have a third and fourth power supply connection to which a power supply device for providing a supply voltage for the switching device can be connected, a detection device, an electrical energy store which is designed for the device-internal power supply, and a voltage supply device connected to the third and fourth power supply connection, which is electrically connected to the electrical energy store and the detection device.The detection device is preferably designed to detect the drop in a DC voltage present at the output of the power supply device below a predetermined threshold value, wherein the control and evaluation device is designed to perform a switch-off process for switching off an electrical load connectable to the first and second output terminals in response to a drop in a DC voltage present at the output of the power supply device below the predetermined threshold value detected by the detection device. The power supply device can have a device for voltage conditioning, for example a voltage converter and / or voltage regulator, and optionally a reverse polarity protection.

[0029] The detection device can, for example, comprise a comparison device, which can be designed as a comparator, for example in the form of a Schmitt trigger. The detection device can be implemented in the control and evaluation device or as a separate component.

[0030] Advantageously, the switching device can have an input terminal configured to apply a control signal, with the detection device being connected on the input side to the input terminal and an output of the power supply device. The control signal can be supplied to the input terminal by a higher-level control device and is monitored by the switching device or, in particular, by the control and evaluation device.

[0031] The detection device is in particular configured such that, when the control signal is applied and when the DC voltage applied to the output of the power supply device falls below the predetermined threshold value, it generates a low level at the output, which signals a faulty power supply device to the control and evaluation device.

[0032] For galvanic isolation, a further mechanical switching contact of at least one electromechanical switch can be connected into the first and / or second current path.

[0033] Preferably, the switching device can have a second semiconductor switch, which can be controlled by the control and evaluation device and is electrically connected in series with the first semiconductor switch. In this case, a semiconductor diode is preferably assigned to each of the first and second semiconductor switches such that, upon appropriate control of the first and second semiconductors, an electrical current can flow to a connected electrical load or to the DC voltage supply device.

[0034] The above-mentioned technical problem is also solved by the method steps of claim 12.

[0035] Accordingly, a method for operating the switching device described above is provided, wherein the method can comprise the following steps: a) connecting an electrical load to the first and second output terminals; b) applying a DC voltage to the first and second power supply terminals; c) providing a supply voltage for the switching device; d) carrying out a switch-on process by the control and evaluation device (70); e) monitoring the voltage values ​​supplied by the voltage detection device during operation by the control and evaluation device; and f) detecting a malfunction of the first electromechanical switch when the monitored voltage values ​​change in a predetermined manner.

[0036] Advantageously, in step d), the switching-on process can be carried out by i) first switching the first semiconductor switch electrically conductive, wherein the first mechanical switching contact is open, and a first voltage value detected by the voltage detection device is temporarily stored, and ii) after a predetermined period of time, the mechanical switching contact of the first electromechanical switch is closed and a second voltage value detected by the voltage detection device, which is less than the first voltage value, is temporarily stored, wherein in step f), a malfunction of the first electromechanical switch is detected if the monitored voltage values ​​exceed the second voltage value, in particular by a predetermined amount. The predetermined amount is preferably less than or equal to the first voltage value.

[0037] Advantageously, the first and / or second semiconductor switch can be designed as an insulated gate bipolar transistor (also called IGBT).

[0038] The invention is explained in more detail below using an exemplary embodiment in conjunction with the accompanying drawings, in which:

[0039] Figure 1 shows an exemplary switching device in which the invention is implemented, and

[0040] Figure 2A shows the time course of an input voltage UB;

[0041] Figure 2B shows the time course of a control signal,

[0042] Figure 2C shows the time course of the switching states of the first shown in Figure 1

[0043] semiconductor switch,

[0044] Figure 2D shows the time course of the switching states of the first mechanical switching contact in Figure 1, and

[0045] Figure 2E shows the time course of the voltage values ​​recorded by the voltage recording device.

[0046] Figure 1 shows the basic circuit of an exemplary switching device 10, with which an electrical load 110 can be electrically switched on and off or electrically connected to or disconnected from a DC voltage supply device 20. For this purpose, the switching device 10 has a first output terminal 16 and a second output terminal 17, to which the electrical load 110 can be connected. Furthermore, the switching device 10 has a first power supply terminal 11 and a second power supply terminal 12, to which the DC voltage supply device 20 can be connected. The DC voltage supply device 20 is designed to apply a DC voltage to the two power supply terminals 11 and 12. In the illustrated embodiment, the DC voltage supply device 20 is designed as a DC supply network.The DC voltage supply device 20 has a first conductor 21, via which a first electrical potential, e.g., a negative electrical potential, can be applied to the power supply connection 11, and a second conductor 22, via which a second electrical potential, e.g., a positive electrical potential, can be applied to the power supply connection 12. Furthermore, the switching device 10 has a first current path 18, which is electrically connected, for example, to the first power supply connection 11 and the first output connection 16. Arranged in the first current path 18 is a parallel circuit 50, which may have a first controllable semiconductor switch 90, a voltage detection device 130, and a mechanical switching contact 82 of a first electromechanical switch 80. The parallel circuit 50 can be referred to as a hybrid output stage.

[0047] The voltage detection device 130 is preferably designed as a voltage divider, which, for example, has four electrical resistors 131 to 134 connected in series. For example, the connection point between the electrical resistors 131 and 132 is electrically connected to an input 70f of the control and evaluation device 70. If the input 70f is an analog input, the control and evaluation device 70 has an A / D converter to convert the analog voltage values ​​supplied by the voltage divider 130 into digital values. In the exemplary switching device 10, the electrical resistor 131 is connected to ground, which in turn is connected to a ground input 70g of the control and evaluation device 70. In this way, a voltage drop across the resistor 131 can be measured by the control and evaluation device 70.For this purpose, the control and evaluation device 70 is preferably floatingly connected to ground via the ground input 70g and is powered via the voltage supply 30, which may include galvanic isolation.

[0048] The semiconductor switch 90 can be designed as a bipolar transistor with an insulated gate electrode. Such a transistor is also referred to as an IGBT transistor. The mechanical switching contact 82, which is connected in parallel to the semiconductor switch 90, preferably belongs to an electromechanical switch 80, which is designed, for example, as a relay. The electromechanical switch 80 has, in a conventional manner, an excitation coil 81 located in a control circuit, which can be connected to an output 70e of a control and evaluation device 70. The mechanical switching contact 82 forms a bypass for the semiconductor switch 90. As shown in Figure 1, in an advantageous implementation, a diode 91 can be connected in parallel to the semiconductor switch 90, which enables a current return flow from the output terminal 16 to the power supply terminal 11.

[0049] The semiconductor switch 90 can be configured, for example, as a normally conducting n-channel transistor whose gate terminal is connected to an output 70i of the control and evaluation device 70. In this case, the cathode of the diode 91 is connected to the collector terminal, and the anode of the diode 91 is connected to the emitter terminal of the semiconductor switch 90. The control and evaluation device 70 can be configured, for example, as a microcontroller. In the exemplary implementation, the collector of the semiconductor switch 90 is connected to the power supply terminal 11, while the emitter terminal of the semiconductor switch 81 is connected to the output terminal 16.

[0050] Optionally, a second controllable semiconductor switch 95 can be provided, which can also be designed, for example, as a normally conducting n-channel transistor and forms a so-called IGBT transistor. The second semiconductor switch 95, if present, is connected anti-serially to the semiconductor switch 90. In the present example, the gate terminal of the semiconductor switch 95 is also connected to an output 70h of the control and evaluation device 70, while the collector terminal can be connected either directly or via a current measuring device 100 to the power supply terminal 16 and further to the ground input 70g of the control and evaluation device. The emitter terminal of the semiconductor switch 95 can be electrically connected to the emitter terminal of the semiconductor switch 90.

[0051] Similar to semiconductor switch 90, semiconductor switch 95 can have a diode 96 connected in parallel to the collector and emitter, the cathode terminal of which is connected to the collector terminal and the anode terminal of which is connected to the emitter terminal of semiconductor switch 95. Diode 96 enables a load current to flow to load 110 when semiconductor switch 90 is electrically conductive and semiconductor switch 95 is electrically blocked. The basic function of semiconductor switch 95 is to enable a current flow in the direction from load 110 to power supply device 20 with the aid of diode 91. For example, load 110 could be an energy storage device that can be discharged with the aid of switching device 10. For this purpose, control and evaluation device 70 is capable of simultaneously switching semiconductor transistor 95 conductive and semiconductor switch 90 off.

[0052] For the sake of simplicity, it is assumed below that the semiconductor switch 95 is not implemented in the switching device 10 or is permanently kept in the electrically blocking state.

[0053] Furthermore, the switching device 10 has a second current path 19 which is electrically connected to the second power supply terminal 12 and the second output terminal 17.

[0054] To detect whether a load current is flowing, a current measuring device 100 can be connected either to the first current path 18 or to the second current path 19. In the illustrated embodiment, the current measuring device 100 is connected to the first current path 18, specifically between the parallel circuit 50 and the output terminal 16. The current measuring device 100 can be designed as a current sensor, as is known per se. An input 70d of the control and evaluation device 70 is connected to an output of the current measuring device 100.As will be explained in more detail below, one task of the control and evaluation device 70 is to specifically put the semiconductor switch 90 and, if present, the semiconductor switch 95 either into a blocking or an electrically conductive state and further to close or open the mechanical switching contact 82 in a predetermined manner and to evaluate the voltage values ​​supplied by the voltage detection device 130, in particular in the switched-on state of the switching device 10, in order to be able to detect a malfunction of the electromechanical switch 80 and in particular an uncontrolled opening of the mechanical switch 82.

[0055] The supply voltage of the switching device 10 can, for example, be obtained from the DC voltage applied to the power supply terminals 11 and 12. Alternatively, and as shown in Figure 1, the supply voltage of the switching device 10 can also be provided via a separate external power supply device 120, which can be connected, for example, via a switch 13 to a third and fourth power supply terminal 13 and 14 of the switching device 10. The power supply device 120 supplies, for example, a DC voltage UB of, for example, 24 V. The supply voltage provided at the power supply terminals 13 and 14 can be fed to an internal voltage supply device 30, which is connected on the input side to the power supply terminals 13 and 14.The voltage supply device 30 can, for example, have a voltage converter and a voltage regulator, which ensure that a predetermined operating voltage for the switching device 10 and its components, such as the control and evaluation device 70, is provided at the output 31 of the voltage supply device 30. In addition, the voltage supply device 30 also supplies the necessary switching energy to control the mechanical switching contact 82. In the present exemplary embodiment, the voltage supply device 30, in particular, supplies switching energy for the excitation coil 81 in order to be able to control the mechanical switching contact 82 accordingly. If the supply voltage of the switching device 10 is obtained from the DC voltage applied to the power supply terminals 11 and 12, the voltage supply device 30 is connected on the input side to the power supply terminals 11 and 12.

[0056] In order to keep the switching device 10 temporarily operational even in the event of a failure of the power supply device 120 or, alternatively, the DC voltage supply device 20, and in particular to be able to perform a targeted switch-off process of the electrical load 110, an electrical energy storage device 40, for example in the form of a capacitor, can be connected to the output 31 of the voltage supply device 30. In this exemplary implementation, the output of the energy storage device 40 is connected, for example, to a supply connection 70a of the control and evaluation device 70.

[0057] In order to monitor the functionality of the power supply device 120, which can be connected to the power supply terminals 13 and 14, a detection device 150 can be provided, which can, in particular, detect the failure of the power supply device 120. The detection device 150 can be implemented, for example, by a comparator, which can be designed as a Schmitt trigger or, in the simplest case, as an AND gate, whose first input is connected to the output 31 of the voltage supply device 30, while the second input of the detection device 150 can be electrically connected to an input terminal 15 of the switching device 10. For galvanic isolation, an optocoupler 160 can be connected between the input terminal 15 and the second input of the detection device 150.An external, preferably binary control signal, which is supplied, for example, by a higher-level control device, can be applied to input terminal 15. The output of detection device 150 is connected to a digital input 70b of control and evaluation device 70. As long as a high-level control signal is present at input terminal 15 and power supply device 120 is electrically connected to power supply terminals 13 and 14 and is functioning properly, detection device 150 signals to control and evaluation device 70 that power supply device 120 is fault-free. It should be noted that detection device 150 can also be an integral component of control and evaluation device 70.In this case, the control and evaluation device 70 has two corresponding inputs which are electrically connected to the output 31 of the voltage supply device 30 and the input terminal 15.

[0058] For example, if a control signal with a high-

[0059] Level, and if the output voltage present at the output 31 of the voltage supply device 30 falls below a predetermined threshold value corresponding to a low level, then the detection device 150 generates, for example, a signal with a low level at its output, which signals a faulty energy supply device 120 to the control and evaluation device 70. In response to this, the control and evaluation device 70 triggers a preferably predetermined switch-off process. The energy stored in the energy storage device 40 is sufficient to carry out the switch-off process for disconnecting the electrical load 110 from the energy supply device 20 by means of the control and evaluation device 70.

[0060] Furthermore, a memory device 60 can be implemented in the switching device 10. The memory device 60 can be electrically connected to the control and evaluation device 70 as a separate memory module. Alternatively, the memory device 60 can also be an integrated component of the control and evaluation device 70. For example, a first voltage value, a second voltage value that is less than the first voltage value, and / or a predetermined amount that is greater than the second voltage value and preferably less than or at most equal to the first voltage value can be stored in the memory device 60.

[0061] For example, the first voltage value is 2 V and the second voltage value is 0 V. The first voltage value is transferred from the voltage detection device 130 to the control and evaluation device 70 when the semiconductor switch 90 is electrically conductive and the mechanical switching contact 82 is open. The second voltage value is transferred from the voltage detection device 130 to the control and evaluation device 70 when the mechanical switching contact 82 is closed, i.e., the excitation coil 81 is energized.

[0062] Optionally, a further mechanical switching contact can be connected in the current path 18 and / or the current measuring path 19. In the illustrated embodiment, a further mechanical switching contact 172 is connected in the current path 18 and a mechanical switching contact 182 is connected in the second current path 19. The two mechanical switching contacts 171 and 182 can be the switching contacts of a common electromechanical switch, or, as shown in Figure 1, of a separate electromechanical switch 180 or 190. The mechanical switching contacts 171 and 182 serve in particular for the galvanic isolation of the electrical load 110. In the exemplary implementation, the two mechanical switching contacts 171 and 182 and also the mechanical switching contact 82 are each designed as normally open contacts. To control the mechanical switches 172 and 182, the control and evaluation device 70 can have two further outputs 70k or70j, via which, for example, the switching energy for an excitation coil 171 of the electromechanical switch 170 or the switching energy for an excitation coil 181 of the electromechanical switch 180 can be supplied from the energy store 40.

[0063] In order to reliably detect the switching state of the electromechanical switch 80 or its mechanical switching contact 82, the electromechanical switch 80 can, for example, have a further mechanical switching contact (not shown) mechanically connected to the switching contact 82, which together can be positively guided. The further mechanical switching contact could be connected to a further input of the control and evaluation device 70. In this way, the control and evaluation device 70 could query the switching state of the further mechanical switching contact of the electromechanical switch 80 in order to detect any malfunction of the mechanical switching contact 82.

[0064] The following explains in more detail the functionality of the exemplary switching device 10, and in particular the function of the switching device 10 for detecting a fault or malfunction of the electromechanical switch 80 during operation, i.e., when the switching device 10 is switched on. Reference is also made to Figures 2A to 2E.

[0065] First, it is assumed that the switching device 10 is to carry out a switch-on process in which the electrical load 110 is electrically connected to the DC voltage supply device 20. It is further assumed that the semiconductor switch 95 is not present or, if present, is electrically blocking during the considered times. Furthermore, it is assumed, by way of example, that at time t0, the control and evaluation device 70 ensures that the semiconductor switch 90 is electrically blocking, the mechanical switching contact 82 is opened and, if present, the mechanical switching contacts 172 and 182 are also opened, as shown in Figure 1. These switching states can also be seen, at least in part, in Figures 2C and 2d. The control and evaluation device 70 preferably achieves this by not energizing the excitation coil 81 and, if present, also the excitation coils 171 and 181, i.e.are not connected to the voltage supply device 30 or the energy storage device 40. It should be noted that the control and evaluation device 70 is preferably designed to control the two electromechanical switches 170 and 180 synchronously.

[0066] A switch-on process is initiated, for example, by applying a supply voltage to the power supply terminals 13 and 14 at time t1 by means of the DC voltage source 120, as shown in Figure 2A. If the switching device 10 is also optionally to monitor the supply voltage present at the power supply terminals 13 and 14, a high level can also be applied to the input terminal 15 as a control signal at time t1, as shown in Figure 2B. The control signal is preferably monitored by the detection device 150 or the control and evaluation device 70. In addition, the control and evaluation device 70 causes the mechanical switching contacts 172 and 182, if present, to be closed by energizing the excitation coils 170 and 180, preferably synchronously, by means of the voltage supply device 30 or the energy storage device 40.At this moment, the electrical potential of the conductor 21 is applied to the output terminal 17 via the current path 19.

[0067] The energy storage device 40 is now charged via the voltage supply device 30, and the detection device 150, embodied, for example, as an AND gate, delivers a high level to the input 70b of the control and evaluation device 70. This signal signals the control and evaluation device 70 that the supply voltage UB is properly present at the input terminals 13 and 14 and that the control signal is present at the input terminal 15. The control signal is implemented, for example, by a high-level signal.

[0068] The control and evaluation device 70 is designed to first switch the first semiconductor switch 90 electrically conductive during the switch-on process at time t2, see Figure 2C, and to temporarily store a first voltage value supplied by the voltage detection device 130 to the input 70d, and after a predetermined time period t3-t2, ie at time t3, to close the mechanical switching contact 82 of the first electromechanical switch 80, see Figure 2D, and to temporarily store a second voltage value supplied by the voltage detection device 130 to the input 70d, which is smaller than the first voltage value.According to an exemplary implementation, at time t2, at which the semiconductor switch 90 is switched electrically conductive, a voltage of, for example, 2 V drops across the electrical resistor 131 of the voltage divider 130, which corresponds to the first voltage value, while at time t3, at which the mechanical switching contact 82 is closed in the error-free case, a voltage of, for example, approximately 0 V drops across the voltage divider 130 or across the electrical resistor 131, which corresponds to the second voltage value. From this predetermined voltage change, which is shown as an example in Figure 2E, the control and evaluation device 70 concludes that the switch-on process has been carried out successfully, i.e., error-free. At the same time, the optionally present current measuring device 100 signals at the input 70e of the control and evaluation device 70 that a load current is flowing.

[0069] During operation, ie, after completion of the switch-on process, the semiconductor switch 90 can be kept electrically conductive or switched to an electrically blocking state. Figure 2C shows, by way of example, that the semiconductor 90 is permanently in the electrically conductive switching state during operation.

[0070] Thanks to this exemplary measure, the robustness of the switching device 10 can be improved precisely because, in the event of a fault, which occurs, for example, due to the uncontrolled opening or bouncing of the mechanical switching contact 82, no change in state occurs at the load 110. If a fault occurs, the load current is immediately commutated to the semiconductor switch 90. In other words, if the semiconductor 90 is permanently kept in the electrically conductive switching state during operation, the availability of the DC switching device 10 can be increased and the electrical load 110 can continue to operate, or it can be switched off by means of the semiconductor switch 90 by the semiconductor switch 90 being specifically switched to the electrically blocking state by the control and evaluation device 70.

[0071] If the switch-on process is successfully completed at time t3, as described above, the control and evaluation device 70 begins to monitor the voltage values ​​supplied by the voltage detection device 130 to the input 70d. The control and evaluation device 70 is designed to detect a malfunction of the first electromechanical switch 80 or the mechanical switching contact 82 when the monitored voltage values ​​change in a predetermined manner. Preferably, the control and evaluation device 70 detects a malfunction of the first electromechanical switch 80 or the mechanical switching contact 82 when the monitored voltage values ​​exceed the second voltage value, i.e. 0V, in particular by a predetermined amount. The predetermined amount lies, for example, between the first and second voltage values, i.e., according to the exemplary implementation, between 0V and 2V.In Figure 2E, a voltage value supplied by voltage divider 130 to input 70f at time tx, which exceeds the second voltage value by a predetermined amount, is shown in dotted lines. The control and evaluation device 70 detects this voltage change at input 70f and concludes, for example by means of a plausibility check, that a fault has occurred with respect to the electromechanical switch 80 or the switching contact 82, in particular an uncontrolled opening of the mechanical switching contact 82. In response to this, the control and evaluation device 70 can, for example, cause the switching device 10 to perform a switch-off process to disconnect the electrical load 110 from the DC voltage supply device 20 and / or to generate a fault message, which is transmitted, for example, to a higher-level controller communicatively connected to the switching device 10.The control and evaluation device 70 is further configured to perform a switch-off operation to electrically disconnect the electrical load 110 from the DC voltage power supply device 20. For this purpose, the control and evaluation device 70 can, in a manner known per se, switch the semiconductor switch 90, if it has been controlled into the electrically blocking state during operation, back into the electrically conductive state and then, according to the exemplary implementation, transfer the excitation coil 81 and, if present, the excitation coils 171 and 181 to the de-energized state, so that the mechanical switching contact 82 and, if present, the mechanical switching contacts 172 and 182 open.

[0072] In addition to the function of being able to detect and recognize a fault with regard to the electromechanical switch 80, the switching device 10 is preferably designed to monitor the supply voltage required to supply the switching device 10 during operation with the aid of the detection device 150 in order to be able to detect a voltage failure and, if necessary, carry out a switching-off process.

[0073] Now assume that a control signal is present at input 15 and, during proper operation, for example, at time t4, the power supply device 120 fails or the supply voltage UB supplied by the power supply device 120 at the power supply terminals 13 and 14 drops below a predetermined threshold value corresponding to a low level. This is shown in Figure 2A. If, in response to this, the voltage present at the output 31 of the voltage supply device 30 drops to zero or below the predetermined threshold value, this voltage drop is detected by the detection device 150 and reported to the control and evaluation device 70. In this case, for example, the detection device 150 generates a low level at its output, which signals a faulty power supply device 120 to the control and evaluation device 70.The detection device 150, embodied, for example, as a Schmitt trigger, can signal a corresponding voltage drop by a level change on the output side of the control and evaluation device 70. In response to the failure of the power supply voltage at the power supply terminals 13 and 14 or in response to a corresponding voltage drop at the output 31 of the power supply device 30, the control and evaluation device 70 causes the switching device 10 to perform a switch-off process using the energy stored in the energy storage device 40, which can correspond to the previously described switch-off process during normal operation. The exemplary switch-off process is shown in Figures 2A to 2D.

[0074] Similarly, the power supply device 20 can be monitored by the switching device 10 for proper operation if the internal power supply of the switching device 20 is obtained from the DC voltage provided by the power supply device 20 at the terminals 11 and 12. In this case, the power supply terminals 11 and 12 are connected to the power supply terminals 13 and 14 or the inputs of the voltage supply device 30. In this case, no power supply device is connected to the power supply voltage terminals 13 and 14.

[0075] Now assume that a control signal is present at input 15 and, during proper operation, the power supply device 20 fails at time t4, or the supply voltage UB supplied by the power supply device 20 at the power supply terminals 11 and 12 drops below a predetermined threshold corresponding to a low level. If, in response to this, the voltage present at the output 31 of the voltage supply device 30 drops to zero or below the predetermined threshold, this voltage drop is detected by the detection device 150 and reported to the control and evaluation device 70. For example, in this case, the detection device 150 generates a low level at its output, which signals a faulty power supply device 20 to the control and evaluation device 70.The detection device 150, which is designed, for example, as a Schmitt trigger, can signal a corresponding voltage drop by a level change on the output side of the control and evaluation device 70. In response to the failure of the power supply voltage at the power supply terminals 11 and 12 or in response to a corresponding voltage drop at the output 31 of the power supply device 30, the control and evaluation device 70 causes the switching device 10 to perform a switch-off process using the energy stored in the energy storage device 40, which can correspond to the previously described switch-off process during normal operation.

[0076] The switching-off process can be carried out by the switching device 10 without disruption, in particular because the electrical energy storage device 40 supplies the necessary energy to supply the control and evaluation device 70 as well as the corresponding semiconductor switches and electromechanical switches with energy if the device supply of the switching device 10 via the DC voltage supply device 20 connected to the first and second energy supply connection 11, 12 or via the energy supply device 120 connected to the third and fourth energy supply connection 13, 14 collapses or fails completely.

Claims

Patent claims 1. Switching device (10) for electrically switching on and off an electrical load (110) connectable to a DC voltage supply device (20), comprising: - a first and a second power supply connection (11, 12) to which an external DC voltage supply device (120) can be connected, - a first and second output terminal (16, 17) to which an electrical load (110) can be connected, - a first current path (18) which is electrically connected to the first power supply terminal (11) and the first output terminal (16), wherein a parallel circuit (50) is arranged in the first current path (18), which parallel circuit has a first controllable semiconductor switch (90), a voltage detection device (130) and a mechanical switching contact (82) of a first electromechanical switch (80), - a second current path (19) electrically connected to the second power supply terminal (12) and the second output terminal (17), - a control and evaluation device (70) connected to the voltage detection device (130), wherein the control and evaluation device (70) is designed to monitor the voltage values ​​supplied by the voltage detection device (130) during operation and to detect a malfunction of the first electromechanical switch (80) when the monitored voltage values ​​change in a predetermined manner.

2. Switching device according to claim 1, wherein the control and evaluation device (70) is designed to first switch the first semiconductor switch (90) electrically conductive during a switch-on process and to temporarily store a first voltage value supplied by the voltage detection device (130), and after a predetermined period of time, to close the mechanical switching contact (82) of the first electromechanical switch (80) and to temporarily store a second voltage value supplied by the voltage detection device (130) which is smaller than the first voltage value, and then to monitor the voltage values ​​supplied by the voltage detection device (130) and to detect a malfunction of the first electromechanical switch (80) when the monitored voltage values ​​exceed the second voltage value.

3. Switching device according to claim 1 or 2, wherein the voltage detection device (130) comprises an electrical voltage divider.

4. Switching device according to one of the preceding claims, further comprising a current measuring device (100) which is connected into the first current path (18) or into the second current path (19) and is electrically connected to the control and evaluation device (70).

5. Switching device according to one of the preceding claims, further comprising: a detection device (150), an electrical energy storage device (40) which is designed for the device-internal energy supply, a voltage supply device (30) which is connected to the first and second energy supply terminals (11, 12) and is electrically connected to the electrical energy storage device (40) and the detection device (150), wherein the detection device (150) is designed to detect the drop in a DC voltage applied to the output (31) of the voltage supply device (30) below a predetermined threshold value, wherein the control and evaluation device (70) is designed to, in response to a detected drop in a DC voltage applied to the output (31) of the power supply device (30), below the predetermined threshold value to carry out a switching-off operation for switching off an electrical load (110) connectable to the first and second output terminals (16, 17).

6. Switching device according to one of claims 1 to 4, further comprising: a third and fourth power supply connection (13, 14), to which a power supply device (120) for providing a supply voltage for the switching device (10) can be connected, a detection device (150), an electrical energy storage device (40) which is designed for the device-internal power supply, a voltage supply device (30) connected to the third and fourth power supply connection (13, 14) and electrically connected to the electrical energy storage device (40) and the detection device (150), wherein the detection device (150) is designed to detect the drop in a DC voltage present at the output (31) of the voltage supply device (30) below a predetermined threshold value, wherein the control and evaluation device (70) is designed toin response to a drop in a DC voltage present at the output (31) of the voltage supply device (30) below the predetermined threshold value detected by the detection device (150), to carry out a switch-off operation for switching off an electrical load (110) connectable to the first and second output terminals (16, 17).

7. Switching device according to claim 5 or 6, wherein the detection device (150) comprises a comparison device.

8. Switching device according to one of claims 5 to 7, further comprising an input terminal (15) which is designed to apply a control signal, wherein the detection device (150) is connected on the input side to the input terminal (15) and an output (31) of the voltage supply device (30).

9. Switching device according to one of claims 5 to 8, wherein the detection device (150) has a comparator and is implemented in the control and evaluation device (70) or as a separate component.

10. Switching device according to one of the preceding claims, wherein a further mechanical switching contact (172, 182) of at least one electromechanical switch (170, 180) is connected into the first and / or second current path (18, 19).

11. Switching device according to one of the preceding claims, wherein a second semiconductor switch (95) controllable by the control and evaluation device (70) is electrically connected anti-serially to the first semiconductor switch (90).

12. A method for operating a switching device (10) according to one of the preceding claims, wherein the method comprises the following steps: a) connecting an electrical load (110) to the first and second output terminals (16, 17); b) applying a DC voltage to the first and second power supply terminals (11, 12); c) providing a supply voltage for the switching device (10); d) carrying out a switch-on process by the control and evaluation device (70); e) monitoring the voltage values ​​supplied by the voltage detection device (130) during operation by the control and evaluation device (70); and f) detecting a malfunction of the first electromechanical switch (80) when the monitored voltage values ​​change in a predetermined manner.

13. The method according to claim 12, wherein in step d) the switching-on process is carried out by i) firstly switching the first semiconductor switch (90) electrically conductive, wherein the first mechanical switching contact (82) is opened, and a a first voltage value detected by the voltage detection device (130) is temporarily stored, and ii) after a predetermined period of time, the mechanical switching contact (82) of the first electromechanical switch (80) is closed and a second voltage value detected by the voltage detection device (130), which is smaller than the first voltage value, is temporarily stored, wherein in step f) a malfunction of the first electromechanical switch (80) is detected if the monitored voltage values ​​exceed the second voltage value.

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