Switch device for electrically activating and deactivating an electric load which can be connected to a DC voltage supply device

Abstract

The invention relates to a switch device (10) for electrically activating and deactivating an electric load (110) which can be connected to a DC voltage supply device (20). The switch device (10) has a first current path (18), in which a parallel circuit (150) is connected, consisting of a first actuatable semiconductor switch (81) and a first mechanical switch contact (82); a second actuatable semiconductor switch (90), which is serially connected to a second mechanical switch contact (91) designed as a changeover contact; a second current path (19); a current measuring device (100); and a control and analysis device (70). During the operation of the switch device (10), the control and analysis device (70) is designed to electrically connect the first current path (18) to the second current path (19) by means of the second semiconductor switch (90) and the second mechanical switch contact (91) if a short-circuit current has been detected by the current measuring device (100).

Description

[0001] Switching device for electrically switching on and off an electrical load that can be connected to a DC voltage supply device

[0002] Description

[0003] The invention relates to a switching device for electrically switching on and off an electrical load that can be connected to a DC voltage supply device.

[0004] Switching devices include, among other things, hybrid output stages, which may include a parallel circuit of an electromechanical and an electronic switch, particularly a semiconductor switch. Using the hybrid output stage, an electrical load connectable to the switching device can be electrically connected to or electrically disconnected from an external power supply, thereby enabling the electrical load to be switched on or off. Such a switching device is known, for example, from WO 2014 / 032718 A1.

[0005] One of the problems with switching devices with hybrid output stages is that a short circuit can destroy the switching device and / or the connected electrical load, or proper operation is no longer possible. This is especially the case if the electrical load is connected to a DC power supply, such as a DC grid, via such a 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, which can protect the switching device from a short circuit during operation.

[0007] A core idea of ​​the invention can be seen in the creation of a switching device with a hybrid output stage that has short-circuit functionality. The switching device can, for example, have a first current path into which a parallel circuit comprising a first controllable semiconductor switch and a first controllable mechanical switching contact is connected, a second controllable semiconductor switch that is connected in series with a second controllable mechanical switching contact that is designed as a changeover contact, a second current path, a current measuring device, and a control and evaluation device. The control and evaluation device is designed to electrically connect the first current path to the second current path during operation of the switching device by means of the second semiconductor switch and the second mechanical switching contact when a short-circuit current is detected by the current measuring device.In this way, the switching device can be protected, in particular, against a short circuit that occurs on or in a connected electrical load or in a line to the electrical load. Such a switching device can also be referred to as a short-circuit-proof switching device.

[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 a DC voltage supply device can be connected, which can in particular provide a supply voltage for an electrical load,

[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 the first current path comprises a parallel circuit comprising a first controllable semiconductor switch and a first controllable mechanical switching contact,

[0013] - a second controllable semiconductor switch, which is connected in series with a second controllable mechanical switching contact, which is designed as a changeover contact, - an electrical precharge resistor, which can be connected in series with the second semiconductor switch by means of the second mechanical switching contact and together with the second semiconductor switch in parallel to form the parallel circuit,

[0014] - a second current path electrically connected to the second

[0015] power supply terminal and the second output terminal, wherein the second semiconductor switch is electrically connectable to the second current path via the second mechanical switching contact,

[0016] - a current measuring device connected in the first or second current path,

[0017] - a control and evaluation device connected to an output of the current measuring device, wherein the control and evaluation device is designed, in particular during a switch-on process, i) to switch the first semiconductor switch to be electrically blocking and the second semiconductor switch to be electrically conducting, wherein the first mechanical switching contact is opened and the second semiconductor switch is electrically connected in series with the pre-charging resistor by means of the second mechanical switching contact, ii) to subsequently switch the first semiconductor switch to be conductive and the second semiconductor switch to be electrically blocking, and iii) to subsequently close the first mechanical switching contact and to connect the second semiconductor switch to the second current path by means of the second mechanical switching contact, wherein the second time is after the first time and the third time is after the second time,and iv) subsequently switching the second semiconductor switch electrically conductive again when the current measured by the current measuring device reaches or exceeds a first predetermined value. The first predetermined current value is, in particular, set such that it corresponds to a short-circuit current.

[0018] In other words, the control and evaluation device executes steps i) to iv) sequentially. Advantageously, the control and evaluation device can be configured to simultaneously switch the first semiconductor switch to the electrically blocking state and the second semiconductor switch to the electrically conducting state in step i), or to switch the second semiconductor switch to the conducting state after it has switched the first semiconductor switch to the blocking state.

[0019] Preferably, the first and second mechanical switching contacts are designed as positively guided contacts of an electromechanical switch. The electromechanical switch can be designed, for example, as a relay. Alternatively, the two mechanical switching contacts can each be arranged in a separate electromechanical switch.

[0020] The current measuring device may expediently comprise a current sensor.

[0021] Advantageously, the control and evaluation device can be configured to switch the first semiconductor switch on and to switch the second semiconductor switch off in step ii) when the current measured by the current measuring device reaches a second predetermined value or lies within a tolerance range defined with respect to the second predetermined value, wherein the second predetermined current value is lower than the first predetermined current value. The second predetermined current value is preferably defined such that it corresponds, for example, to the rated current of the first semiconductor switch.

[0022] Alternatively, the control and evaluation device can be configured to execute step ii) after a predetermined period of time, which is initiated in step i), has elapsed. In both cases, it is ensured that step ii) is only executed when the current flowing in the first current path can no longer damage the first semiconductor switch.

[0023] In order 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 which is designed for the device-internal energy supply, and a voltage supply device connected to the first and second energy supply connection, which is electrically connected to the electrical energy store and the detection device, wherein the detection device is designed to detect the drop in a DC voltage applied to the output of the voltage supply device below a predetermined threshold value, wherein the control and evaluation device is designed toin response to a drop in a DC voltage applied to the output of the power supply device below the predetermined threshold value, detected by the detection device, to carry out a switching-off operation for switching off an electrical load connectable to the first and second output terminals.

[0024] 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, wherein the detection device is designed to detect the drop in a DC voltage applied to the output of the voltage supply device below a predetermined threshold value, wherein the control and evaluation device is designed toin response to a drop in a DC voltage applied to the output of the power supply device below the predetermined threshold value, detected by the detection device, to carry out a switching-off operation for switching off an electrical load connectable to the first and second output terminals.

[0025] The power supply device may include a voltage conditioning device, for example, a voltage converter and / or voltage regulator, and optionally reverse polarity protection. The detection device may, for example, include a comparison device, which may be designed as a comparator, for example, in the form of a Schmitt trigger.

[0026] 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 by the control and evaluation device.

[0027] 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.

[0028] Advantageously, the first and / or second semiconductor switch can be designed as an insulated gate bipolar transistor (also called IGBT) or as a metal oxide semiconductor field effect transistor (also known as MOSFET).

[0029] The switching device can, for example, have a memory device that is electrically connected to the control and evaluation device. The first and / or second predetermined current value and / or the tolerance range defined with respect to the second predetermined current value can be stored in the memory device. The memory device can also be an integral part of the control and evaluation device.

[0030] Conveniently, an electrical fuse can be assigned to the first current path or the second current path. The fuse can be connected externally to the first or second power supply connection or arranged internally in the switching device.

[0031] The invention will be explained in more detail below using an exemplary embodiment in conjunction with the accompanying drawings. Figure 1 shows an exemplary switching device in which the invention is implemented, and

[0032] Figure 2A shows the time course of an input voltage UB;

[0033] Figure 2B shows the time course of a control signal,

[0034] Figure 2C shows the time course of the switching states of the second semiconductor switch shown in Figure 1,

[0035] Figure 2D shows the time course of the switching states of the first semiconductor switch shown in Figure 1,

[0036] Figure 2E shows the time course of the switching states of the first mechanical switch shown in Figure 1,

[0037] Figure 2F shows the time course of the switching states of the second mechanical switch shown in Figure 1.

[0038] 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 terminal 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 terminal 12. Furthermore, the switching device 10 has a first current path 18, which is electrically connected, for example, to the first power supply terminal 11 and the first output terminal 16. Arranged in the first current path 18 is a parallel circuit 150, which can have a first controllable semiconductor switch 81 and a first controllable mechanical switching contact 82. The semiconductor switch 81 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 arranged parallel to the semiconductor switch 81, 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 85 located in a control circuit, which can be connected to an output 76 of the control and evaluation device 70. The mechanical switching contact 82 forms a bypass for the semiconductor switch 81. As shown in Figure 1, in an advantageous implementation, a semiconductor diode 86 can be connected in parallel to the semiconductor switch 81, which enables a current return flow from the output terminal 16 to the power supply terminal 11.

[0039] The semiconductor switch 81 can be configured, for example, as a normally conducting n-channel transistor whose gate terminal is connected to an output 74 of a control and evaluation device 70. The control and evaluation device 70 can be configured, for example, as a microcontroller. In the exemplary implementation, the collector of the semiconductor switch 81 is connected to the power supply terminal 11, while the emitter terminal of the semiconductor switch 81 is connected to the output terminal 16.

[0040] Furthermore, a second controllable semiconductor switch 90 is provided, which can also be designed, for example, as a normally conducting n-channel transistor and forms a so-called IGBT transistor. In the present example, the gate terminal of the semiconductor switch 90 is also connected to an output 73 of the control and evaluation device 70, while the collector terminal is electrically connectable to the power supply terminal 11 and the emitter terminal is electrically connectable to the output terminal 16 or a second current path 19. Similar to the semiconductor switch 81, the semiconductor switch 98 can have a semiconductor diode 96 connected in parallel to the collector and emitter, which allows a reverse current to flow from the load 110 to the power supply terminal 11. The semiconductor switch 90 is connected in series with a second mechanical switching contact 91, which is designed as a changeover contact.According to an advantageous embodiment, the two mechanical switching contacts 82 and 91 are part of the electromechanical switch 80. They are advantageously designed to be positively guided. It is conceivable that the two mechanical switching contacts 82 and 91 each belong to a separate electromechanical switch, which can be controlled via the control and evaluation device 70.

[0041] In order to limit the currents flowing when a capacitive load is switched on, a suitably dimensioned electrical precharging resistor 92 is provided, which can be connected in series with the semiconductor switch 90 by means of the mechanical switching contact 91. In this switching state, the second semiconductor switch 90, which is connected in series with the electrical precharging resistor 92, is then connected in parallel with the parallel circuit 150.

[0042] Furthermore, the switching device 10 has the second current path 19, which is electrically connected to the second power supply terminal 12 and the second output terminal 17. According to an advantageous implementation, the semiconductor switch 90 is electrically connectable to the second current path 19 via the mechanical switching contact 91.

[0043] In order to detect a short-circuit current, in particular, a current measuring device 100 is 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 150 and the output terminal 16. The current measuring device 100 can be designed as a current sensor, as is known per se. An input 72 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 place the two semiconductor switches 81 and 90 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 connect the mechanical switching contact 91 in a targeted manner to the precharging resistor 92 or the second current path 19.

[0044] As further shown in Figure 1, an electrical fuse 140 can be provided, which can be connected externally, for example, between the conductor 22 and the supply connection 11 as an external fuse. However, it is also conceivable that the fuse is connected as a device-internal component in the first current path 18 or second current path 19.

[0045] 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 LTB 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 for controlling the mechanical switching contacts 82 and 91. In the present exemplary embodiment, the voltage supply device 30, in particular, supplies switching energy for the excitation coil 85 in order to be able to control the mechanical switching contacts 82 and 91 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.

[0046] 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 78 of the control and evaluation device 70.

[0047] 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 50 can be provided, which can detect, in particular, the failure of the power supply device 120 or a drop in the voltage supplied by the power supply device 120 below a predetermined threshold value. The detection device 50 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 50 can be electrically connected to an input terminal 15 of the switching device 10. An external, preferably binary control signal, which is supplied, for example, by a higher-level control device, can be applied to the input terminal 15.The control signal preferably serves as a reference value with a predetermined threshold. The output of the detection device 50 is connected to a digital input 71 of the control and evaluation device 70. As long as a high-level control signal is present at the input terminal 15 and the power supply device 120 is electrically connected to the power supply terminals 13 and 14 and is operating properly, the detection device 50 signals to the control and evaluation device 70 that the power supply device 120 is fault-free. It should be noted that the detection device 50 can also be an integral component of the 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 and the input terminal 15.

[0048] For example, if a high-level control signal is present at the detection device 50 and the output voltage present at the output 31 of the voltage supply device 30, which is also present at the detection device 50, falls below a predetermined threshold corresponding to a low level, then the detection device 50 generates, for example, a low-level signal at its output, which signals a faulty power supply device 120 to the control and evaluation device 70. In response to this, the control and evaluation device 70 triggers a preferably predetermined shutdown process. The energy stored in the energy storage device 40 is sufficient to carry out the shutdown process for disconnecting the electrical load 110 from the power supply device 20 by means of the control and evaluation device 70.The predetermined threshold value above which the detection device 50 detects a low level at the input depends in particular on its implementation and dimensioning.

[0049] 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 predetermined current value corresponding to the rated current of the electrical fuse 140 can be stored in the memory device 60, from which, for example, a short-circuit current can be derived, upon the occurrence of which the semiconductor switch 90 must be switched electrically conductive. Furthermore, a further predetermined current value corresponding to the rated current of the semiconductor switch 81 can be stored in the memory device 60. 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 131 is connected to the current path 18, and a mechanical switching contact 132 is connected to the second current path 19. The two mechanical switching contacts 131 and 132 can, for example, be positively guided switching contacts of a single electromechanical switch 130, which, in a conventional manner, has an excitation coil 133 located in a control circuit. The two mechanical switching contacts 131 and 132 can also each be integrated into a separate electromechanical switch. The mechanical switching contacts 131 and 132 serve, in particular, to galvanically isolate the electrical load 110. In the exemplary implementation, the two mechanical switching contacts 131 and 132 and also the mechanical switching contact 82 are each designed as normally open contacts.To control the mechanical switches 131 and 132, the control and evaluation device 70 can have a further output 75, via which, for example, the switching energy for the excitation coil 133 can be supplied from the energy storage device 40.

[0050] The following explains in more detail the functionality of the exemplary switching device 10, and in particular the short-circuit function of the switching device 10 during operation, i.e., in the switched-on state. Reference is also made to Figures 2A to 2F.

[0051] First, it is assumed that the switching device 10 is to carry out a switching-on process in which the electrical load 110 is electrically connected to the DC voltage supply device 20.

[0052] Furthermore, it is assumed, by way of example, that at time t0, the control and evaluation device 70 ensures that the semiconductor switches 81 and 90 are electrically blocked and the mechanical switching contacts 82, 91, 131, and 132 assume the switching state shown in Figure 1. This can also be partially seen in Figures 2C to 2F. The control and evaluation device 70 preferably achieves this by not energizing the excitation coils 85 and 133, i.e., by not connecting them to the voltage supply device 30 or the energy storage device 40.

[0053] A switch-on process is preferably initiated by applying a supply voltage to the power supply terminals 13 and 14 at time t0 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 t0, as shown in Figure 2B. The control signal is preferably monitored by the detection device 50. In addition, the control and evaluation device 70 causes the mechanical switching contacts 131 and 132 to be closed by energizing the excitation coil 133 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.

[0054] The energy storage device 40 is now charged via the voltage supply device 30 and the detection device 50, which is designed, for example, as an AND gate, supplies a high level to the input 71 of the control and evaluation device 70, which signals to the control and evaluation device 70 that the supply voltage UB is correctly applied to the inputs 13 and 14 and the control signal is applied to the input terminal 15.

[0055] In order to be able to precharge the electrical load 110, the control and evaluation device 70 causes the switching device 10 to switch the semiconductor switch 90 to be electrically conductive at a time t1, as shown in Figure 2C, while the semiconductor switch 81 is blocked or is controlled or held in a blocking manner by the control and evaluation device 70. It should be noted that, depending on the implementation, a first time period t1-t0 can be stored in the data memory 60, which indicates when the semiconductor switch 90 is to be switched to be electrically conductive after the control signal is applied to the input terminal 15. For this purpose, the control and evaluation device 70 can have a timer that is triggered by the application of the control signal to the input terminal 15, wherein the control and evaluation device 70 switches the semiconductor switch 90 to be electrically conductive after the first time period has elapsed.At this moment, the electrical potential of conductor 22 is applied to output terminal 16 via semiconductor switch 90 and precharging resistor 92, allowing a precharging current to flow through load 110 and current path 19 via semiconductor switch 90 and precharging resistor 92. It should be noted that the timer (not shown) can also be implemented as a separate component that is electrically connected to control and evaluation device 70.

[0056] At a later time t2, the control and evaluation device 70 causes the switching device 10 to turn on the semiconductor switch 81 and turn off the semiconductor switch 90. Depending on the implementation, a second time period t2-t1 can be stored in the data memory 60, which indicates when the semiconductor switch 81 is to be turned on and the semiconductor switch 90 is to be turned off. For example, the timer is triggered at the time t1 at which the semiconductor switch 90 is turned on, and the control and evaluation device 70 turns on the semiconductor switch 81 and turns off the semiconductor switch 90 after the second time period has elapsed.

[0057] The time t2 at which the control and evaluation device 70 ensures that the semiconductor switch 81 is electrically conductive and the semiconductor switch 90 is electrically blocked can also be determined with the aid of the current sensor 100. The current value that triggers the corresponding control process can be determined, for example, by the rated current of the semiconductor switch 81 or the rated current of the fuse 140. This predetermined current value can in turn be stored in the memory device 60. As soon as the current measuring device 100 measures a current that corresponds to the stored predetermined current value, i.e. reaches this or lies within a predetermined tolerance range with regard to this current value, the control and evaluation device 70 responds and causes the switching device 10 to switch the semiconductor switch 81 conductive and the semiconductor switch 90 electrically blocking.The current value that determines time t2 must be dimensioned such that no overload of the semiconductor switch 81 and the fuse 140 can occur at the switch-on time. The corresponding switching states of the semiconductor switches 81 and 90 are shown as examples in Figures 2C and 2D at time t2.

[0058] At a later time t3, the control and evaluation device 70 causes the switching device 10 to close the mechanical switching contact 82 in order to relieve the load on the semiconductor switch 81 in a manner known per se. This can, in particular, reduce the power loss in the switching device 10, whereby a larger proportion of energy can be made available to the electrical load 110. At the same time, i.e. also at time t3, the mechanical switching contact 91 acting as a changeover contact is switched, so that the emitter terminal of the semiconductor switch 90 is now electrically connected to the current path 19 and thus to the output terminal 17. The time period t3-t2 can in turn be stored as a predetermined time value in the data memory 60. The control and evaluation device 70 is designed to access the values ​​stored in the memory device 60 and use them accordingly.

[0059] According to an exemplary implementation, the timer is started at time t2, at which the semiconductor switch 81 is electrically switched on, wherein after the expiration of the predetermined time period t3-t2, i.e., at time t3, the control and evaluation device 70 ensures that the mechanical switching contact 82 is closed and the mechanical switching contact 91 is electrically connected to the current path 19. According to the exemplary implementation, this can be achieved by the control and evaluation device 70 ensuring that the excitation coil 85 is energized via the energy storage device 40, whereby the two mechanical switching contacts 82 and 91 are switched.

[0060] The switch-on process is now complete, and the switching device 10 connects the electrical load 110 to the DC voltage supply network 20 during proper operation. The control and evaluation device 70 is preferably designed to monitor the switching device for a short-circuit current with the aid of the current measuring device 100 after the proper switch-on process has been completed, in order to take appropriate safety precautions if a short-circuit current has been measured by the current measuring device 100. Accordingly, a current value that signals a short circuit can be stored in the memory device 60.

[0061] Now assume that at any time after time t3, current measuring device 100 measures a current, for example, in current path 18, whose value signals a short circuit to control and evaluation device 70. In response to this, control and evaluation device 70 causes switching device 10 to make semiconductor switch 90 electrically conductive again. Since mechanical switching contact 91 is still electrically connected to current path 19, the two conductors 21 and 22 of DC voltage supply device 20 are short-circuited at this moment, thus protecting electrical load 110 from damage.

[0062] Thanks to the special short-circuit protection, a short circuit that may occur can be kept away from the electrical load at any time during operation of the switching device 10. This is achieved in particular by the fact that, in the event of a short circuit, current commutation occurs from current path 18 via the semiconductor switch 90 and the mechanical switching contact 91 to current path 19.

[0063] It should be noted that during proper operation, the semiconductor switch 81 does not need to be kept in the electrically conductive state. Rather, it can be switched to the electrically blocking state at any time by the control and evaluation device 70.

[0064] The control and evaluation device 70 is further designed to carry out a known switching-off process in order to electrically disconnect the electrical load 110 from the DC voltage power supply device 20. For this purpose, the control and evaluation device 17 can, in a manner known per se, switch the semiconductor switch 81, 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 coils 85 and 133 to the de-energized state so that the mechanical switching contacts 82 and, if present, the mechanical switching contacts 131 and 132 open, wherein, according to the exemplary embodiment, the precharging resistor 92 is then electrically connected to the collector of the semiconductor switch 90.It should be noted that the mechanical switching contacts 131 and 132 are advantageously opened only during currentless operation of the switching device 10, ie at the earliest from time t6, in order to prevent damage to the switching contacts 131 and 132 as a result of arcing.

[0065] In addition to the short-circuit functionality, the switching device 10 is preferably designed to monitor the supply voltage required to supply the switching device 10 during operation and, if necessary, to carry out a switching-off process.

[0066] Now assume that the control signal is still present at input 15 and that, during proper operation, at time t4, the power supply device 120 fails or the supply voltage UB supplied by the power supply device 120 drops at the power supply terminals 13 and 14. 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, which is defined by the high level of the control signal present at the input terminal 15, this voltage drop is detected by the detection device 50 and reported to the control and evaluation device 70. The detection device 50, designed, for example, as a Schmitt trigger, can signal a corresponding voltage drop below the predetermined threshold value by an output-side level change of the control and evaluation device 70.The predetermined threshold value is determined in particular by the implementation and dimensioning of the detection device 50. In particular, the predetermined threshold value determines when the detection device 50 detects a low level at its corresponding input. 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 proper operation. The exemplary switch-off process is shown in Figures 2A to 2F.

[0067] 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 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.

[0068] Now assume that the control signal is still present at input 15 and that, during proper operation, the power supply device 20 fails at time t4, or the supply voltage UB supplied by the power supply device 20 drops at the power supply terminals 11 and 12. 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 50 and reported to the control and evaluation device 70. For example, in this case, the detection device 50 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 50, 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. The predetermined threshold value is determined in particular by the implementation and dimensioning of the detection device 50. In particular, the predetermined threshold value specifies when the detection device 50 detects a low level at its corresponding input. 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 proper operation.

[0069] 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 a DC voltage supply device (20) 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 the first current path (18) has a parallel circuit (150) comprising a first controllable semiconductor switch (81) and a first mechanical switching contact (82), - a second controllable semiconductor switch (90) connected in series with a second mechanical switching contact (91) designed as a changeover contact, - an electrical pre-charging resistor (92) which is connected in series with the second semiconductor switch by means of the second mechanical switching contact (91) (90) and can be connected together with the second semiconductor switch (90) in parallel to the parallel circuit (150), - a second current path (19) which is electrically connected to the second power supply terminal (12) and the second output terminal (17), wherein the second semiconductor switch (90) is connected via the second mechanical switching contact (91) is electrically connectable to the second current path (19), - a current measuring device (100) connected in the first or second current path (18, 19), - a control and evaluation device (70) which is connected to an output of the current measuring device (100), wherein the control and evaluation device (70) is designed to i) electrically block the first semiconductor switch (81) and to switch the second to switch the semiconductor switch (90) electrically conductive, wherein the first mechanical switching contact (82) is open and the second semiconductor switch (90) is electrically connected in series with the precharging resistor (92) by means of the second mechanical switching contact (91), ii) subsequently switch the first semiconductor switch (81) conductive and switch the second semiconductor switch (90) electrically blocking, and iii) subsequently close the first mechanical switching contact (82) and connect the second semiconductor switch (90) to the second current path (19) by means of the second mechanical switching contact (91), wherein the second time is after the first time and the third time is after the second time, and iv) subsequently switch the second semiconductor switch (90) electrically conductive again when the current measured by the current measuring device (100) reaches or exceeds a first predetermined value.

2. Switching device according to claim 1, wherein the control and evaluation device (70) is designed to switch the first semiconductor switch (81) on and to switch the second semiconductor switch (90) off in step ii) when the current measured by the current measuring device (100) reaches a second predetermined value or lies within a tolerance range defined with respect to the second predetermined value, wherein the second predetermined current value is lower than the first predetermined current value.

3. Switching device according to claim 1, wherein the control and evaluation device (70) is designed to carry out step ii) after a predetermined period of time has elapsed.

4. Switching device according to one of the preceding claims, further comprising: a detection device (50), an electrical energy storage device (40) which is designed for the device-internal energy supply, a voltage supply device (30) connected to the first and second energy supply terminals (11, 12) and electrically connected to the electrical energy store (40) and the detection device (50), wherein the detection device (50) 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 carry out a switch-off process for switching off an electrical load (110) connectable to the first and second output terminals (16, 17) 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.

5. Switching device according to one of claims 1 to 3, 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 (50), 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 (50), wherein the detection device (50) 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 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 (50), a switch-off process for, Switching off an electrical load (110) connectable to the first and second output terminals (16, 17).

6. Switching device according to claim 4 or 5, wherein the detection device (50) comprises a comparison device.

7. Switching device according to one of claims 4 to 6, further comprising an input terminal (15) which is designed to apply a control signal, wherein the detection device (50) is connected on the input side to the input terminal (15) and an output (31) of the voltage supply device (30).

8. Switching device according to one of the preceding claims, wherein a further mechanical switching contact (131, 132) of at least one electromechanical switch (130) is connected into the first and / or second current path (18, 19).

9. Switching device according to one of the preceding claims, wherein the current measuring device (100) comprises a current sensor.

10. Switching device according to one of the preceding claims, wherein the first and / or second semiconductor switch (81, 90) is an insulated gate bipolar transistor.

11. Switching device according to one of the preceding claims, wherein the first and second mechanical switching contacts (82, 91) are arranged in a common electromechanical switch (85), or wherein the first mechanical switching contact (82) and the second mechanical switching contact (91) are each arranged in a separate electromechanical switch (85, 95).

12. Switching device according to one of the preceding claims, further comprising a memory device (60) which is electrically connected to the control and evaluation device (70), wherein a current threshold value corresponding to a short-circuit current is stored in the memory device (60).

13. Switching device according to one of the preceding claims, wherein a fuse (140) is assigned to the first current path (18) or the second current path (19).

14. Switching device according to one of the preceding claims, wherein the control and evaluation device (70) is designed to control a switching-off process for electrically isolating the electrical load (110) connected to the first and second output terminals (16, 17) from the DC voltage supply device (20) connected to the first and second power supply terminals (11, 12).

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