Switching unit

Abstract

The invention relates to a switching unit (14) having a load connection (12) and an earth connection (16), between which a switching element (20) is connected, and having a semiconductor switch (24) comprising two connections (26) and a control input (38). One connection (26) is connected to the earth connection (16) and the other is connected to a signal contact (28), and the control input (38) is connected to the load connection (12). The invention also relates to an electrical circuit (2).

Description

[0001] Description

[0002] switching unit

[0003] The invention relates to a switching unit with a load terminal and a ground terminal, between which a switching element is connected. Furthermore, the invention relates to an electrical circuit.

[0004] Systems, such as industrial plants, typically have one or more actuators used to perform an activity. In an industrial plant, for example, the actuator is used to create and / or process a workpiece. To ensure that the actuator operates according to the desired function, a controller is provided to adjust the actuator's power supply. In the simplest case, this consists of a switching element that is operated by the controller. The switching element switches the actuator on and off. For this purpose, the switching element is integrated into an electrical supply line of the actuator.

[0005] If functions are carried out using the actuator that could endanger other machines and / or operating personnel, it is necessary to provide functional safety. In an emergency, the intended function of the actuator must be terminated and a safe state must be assumed. This usually requires that the power supply to the actuator is stopped and therefore the switching element is open. It is also necessary, for example, during maintenance of the actuator that it is not operated, i.e. that the switching element is open. In both application cases, it must therefore be ensured that the actuator is not energized in order to rule out further hazards. For this purpose, it is in principle possible to measure the electrical current currently carried via the supply line.However, these typically carry comparatively high electrical currents and / or voltages, making such a measuring device relatively expensive. Furthermore, if the actuator is damaged and the voltage is reflected back into the supply line, the measuring device could be damaged. Therefore, it would be impossible to reliably determine whether the actuator is actually no longer receiving power.

[0006] To check whether the actuator is currently receiving power, the switching state of the switching element can also be checked. The switching element is typically a mechanical switch with two contacts that can move relative to each other, one of which is usually connected to a movable contact bridge. If the switching element is electrically conductive, the contacts are mechanically in contact with each other, and the electrical current used to power the actuator is conducted through these contacts. To open the switching element, the contacts are spaced apart, which requires the contact bridge to be moved.

[0007] An auxiliary contact is typically connected to the contact bridge. When the contact bridge is moved, the auxiliary contact is released from another auxiliary contact, interrupting the flow of current through an auxiliary circuit into which the auxiliary contacts are inserted. By checking whether a current is flowing in the auxiliary circuit, it is possible to determine whether the switching element is open or closed. The auxiliary circuit can be used to conduct a reduced electrical current and / or apply a reduced electrical voltage, thus simplifying testing of the auxiliary circuit. The auxiliary circuit can also be galvanically isolated from the supply line, further increasing safety.

[0008] This type of checking the switching state of the switching element requires the use of a comparatively complex mechanical switch, which at least additionally has the two auxiliary contacts. The use of a semiconductor switch, however, is not possible, as it cannot open two separate circuits simultaneously. Due to the use of the mechanical switch, an arc can form upon opening, which could, for example, lead to the contact being welded shut, making it impossible to open it again. Manufacturing costs are also comparatively high.

[0009] The invention is based on the object of specifying a particularly suitable switching unit and a particularly suitable circuit, wherein manufacturing costs are advantageously reduced and wherein, in particular, safety is increased.

[0010] With regard to the switching unit, this object is achieved according to the invention by the features of claim 1 and with regard to the circuit by the features of claim 10. Advantageous further developments and refinements are the subject of the dependent claims.

[0011] The switching unit is, for example, a component of a system by means of which a specific function is performed. In particular, the system is an industrial system and is used, for example, for the production and / or processing of a specific workpiece. For this purpose, the system has, in particular, an actuator. The actuator is, for example, an electric motor, which is, for example, a rotating electric motor or a linear motor. Alternatively, the actuator is, for example, an electrically operated valve. In another alternative, the system is, for example, a communications system or a data center.

[0012] The switching unit is suitable, in particular designed, for interrupting or creating an electrical current flow. The electrical current that is normally carried and in particular corresponds to the rated current is preferably between 0.5 A and 200 A, between 1 A and 100 A, or between 10 A and 50 A. Preferably, a rated voltage of the switching unit, which is applied to it in particular when the switching unit is not electrically non-conductive, is greater than 10 V, 20 V, or 100 V and, for example, less than 10 kV, 5 kV, or 1 kV. In particular, the electrical voltage is a direct voltage or an alternating voltage.

[0013] The switching unit has a load terminal and a ground terminal, between which a switching element is connected. If the switching element is electrically conductive, i.e. closed, the load terminal and the ground terminal are in low-resistance contact with each other. If the switching element is open, and therefore in the electrically non-conductive state, however, the load terminal and the ground terminal are only connected to each other with high-resistance, so that an electrical current cannot flow between them. The ground terminal is suitable, in particular provided and configured, that a ground potential is applied to it. The load terminal, on the other hand, is suitable, in particular provided and configured, that a load is connected to it. In the assembled state, the load terminal is electrically connected to a voltage source via the load.When the switching element is electrically conductive, i.e., closed, current is supplied to the load. If, however, the switching element is open, current is supplied to the load.

[0014] For example, the switching element is a mechanical switch, such as a relay. Preferably, however, the switching element is designed as a semiconductor switch and, in particular, has a comparatively high current-carrying capacity. The switching element is expediently a field-effect transistor, preferably a MOSFET, IGBT, or GTO.

[0015] The switching unit further comprises a semiconductor switch that is separate from the switching element. In other words, the semiconductor switch is a component separate from the switching element, and the semiconductor switch is provided by a semiconductor component. The semiconductor switch has two terminals that are connected to one another with low resistance when the semiconductor switch is electrically conductive. If, however, the semiconductor switch is open, the two terminals are connected to one another with high resistance. The semiconductor switch also has a control input. By applying a specific electrical potential to the control input, it is possible to set the semiconductor switch to the electrically conductive or electrically non-conductive state. The semiconductor switch is expediently a transistor.At least the semiconductor switch preferably has a lower current carrying capacity than the switching element, so that manufacturing costs are reduced.

[0016] One terminal of the semiconductor switch is connected to the ground terminal. The other terminal is connected to a signal contact of the switching unit. Preferably, the terminal is directly electrically contacted with the signal contact without one or more electrical / electronic components being arranged between them, which are, for example, at least partially electrically connected in series and / or parallel. If the semiconductor switch is electrically conductive, the signal contact is at the same electrical potential as the ground terminal, i.e. in particular electrically connected to ground, or at least at an electrical potential that is determined by ground. If the semiconductor switch is open, however, the electrical potential to which the signal contact is connected is different from ground and / or in particular independent of it.

[0017] The control input of the semiconductor switch is connected to the load terminal. For example, the control input is electrically connected directly to the load terminal, or additional electrical / electronic components are arranged between them. At the very least, the electrical potential at the control input depends on the electrical potential at the load terminal.

[0018] If the switching element is thus electrically closed, the load terminal is at the same electrical potential as the ground terminal. As a result, an electrical potential corresponding to the ground terminal is present at the control input, and the semiconductor switch is particularly designed such that it is then open. The electrical potential of the signal contact is therefore different from ground. If, on the other hand, the switching element is not electrically conductive, the electrical potential present at the load terminal is different from the electrical potential present at the ground terminal. The electrical potential present at the control input is therefore also changed. The semiconductor switch is particularly designed such that it is then electrically conductive. As a result, ground is then present at the signal contact as the electrical potential, or at least these correspond to one another.

[0019] In summary, the circuitry makes it possible to determine whether the switching element is in an electrically conductive or non-conductive state based on the electrical potential applied to the signal contact. This increases safety. The requirements for the switching element are comparatively low, thus reducing manufacturing costs. Furthermore, it is possible to use a semiconductor as the switching element, which further reduces manufacturing costs.

[0020] The switching unit suitably comprises a housing into which one or more terminals are incorporated. One of the terminals is expediently electrically connected to the ground connection and the other to the load connection. This allows the corresponding electrical potentials to be detected from outside the housing, facilitating assembly. Alternatively, or in combination with this, the signal contact, for example, can be perceived at least indirectly from outside the housing.

[0021] For example, the switching element is designed as a mechanical switch that can only be operated manually. Alternatively, the switching element has, for example, a control input via which the switching unit is actuated. The switching state of the switching element is expediently changed depending on an electrical potential applied to the control input. This makes it possible to adjust the electrical current flow between the load terminal and the ground terminal remotely from the switching unit, particularly within the context of process control. The switching element is preferably a semiconductor.In a further development, the switching unit is, for example, a component of a circuit breaker, wherein the switching element is actuated in particular as a function of a fault, such as an overcurrent, a short-circuit current, an overvoltage or another malfunction, for example of the possible load.

[0022] Preferably, the signal contact is guided against a first resistor. In this case, a further electrical component is arranged between the signal contact and the first resistor, or the signal contact is electrically connected directly to the first resistor. The first resistor ensures, in particular, that the electrical current carried by the semiconductor switch is comparatively low when the switch is electrically conductive. This increases safety and reduces electrical losses. Furthermore, this further reduces the load on the switching element, allowing it to be designed comparatively cost-effectively.

[0023] For example, the first resistor is connected to a supply terminal. In the assembled state / when the switching unit is in use, an electrical potential is preferably applied to the supply terminal, which electrical potential is suitably constant over time. In this case, the electrical voltage applied, in particular, between the ground terminal and the supply terminal is less than 50 V, 20 V, 10 V, or 5 V. This further reduces the requirements for the first resistor, the signal contact, and the semiconductor switch, which means that manufacturing costs can be reduced. The switching unit expediently comprises a terminal that is electrically connected to the supply terminal and, in particular, is incorporated into the housing, if present. This makes it possible to apply the corresponding electrical potential to the supply terminal from outside the housing.

[0024] Preferably, a control unit is provided which is electrically connected to the supply connection. This means that it is also operated based on the electrical potential present there. This reduces the risk of errors and enables operation of the control unit regardless of the electrical voltage present between the ground connection and the load connection. The switching element is preferably actuated by means of the control unit. In an alternative to this, the first resistor is connected to the load connection via a second resistor. This eliminates the need for a separate supply connection, which simplifies assembly. This also reduces manufacturing costs. When the semiconductor switch is open, the electrical potential present at the signal contact corresponds to the electrical potential present at the load connection.The two resistors ensure that the electrical current flowing from the load terminal via the semiconductor switch to the ground terminal is comparatively low, thus reducing the load on the semiconductor switch. This also ensures that no unwanted current is applied to any load connected to the load terminal when the switching element is open. The series connection of the two resistors reduces the requirements for the individual resistors, allowing them to be designed to be comparatively small and cost-effective.

[0025] Preferably, the second resistor is connected to the ground terminal via a Zener diode. The reverse bias of the Zener diode is expediently directed away from the ground terminal. The Zener diode is thus connected in parallel to the series circuit containing the first resistor and the semiconductor switch. In particular, the Zener diode is also electrically connected in parallel to the series circuit containing the second resistor and the switching element. The Zener diode prevents, in particular, the formation of an overvoltage that could lead to the destruction of the switching element or semiconductor switch. The second resistor ensures that the maximum electrical current flowing through the Zener diode is comparatively low, so that a comparatively cost-effective component can be used here too.

[0026] Preferably, the first resistor is connected to a third resistor. In this case, the first resistor is expediently electrically connected directly to the third resistor. The third resistor, in turn, is connected to the load terminal via a first diode. Furthermore, the third resistor is connected to the control input via a fourth resistor and a second diode. Expediently, the two diodes and the fourth resistor are electrically connected in series. The reverse direction of the two diodes is in particular opposite to one another, and the reverse direction of the second diode is directed from the control input to the fourth resistor. In particular, the two diodes are structurally identical to one another, which reduces manufacturing costs. This also improves the functioning of the switching unit. Preferably, the two diodes are thermally connected to one another and expediently arranged next to one another.Thus, the two diodes essentially always exhibit the same behavior. For example, the first resistor is connected to the supply terminal, so that the third resistor is also connected to the supply terminal. Alternatively, the second resistor is present, and the third resistor is also connected to the second resistor.

[0027] By means of the fourth resistor and the third resistor, it is possible to set the voltage level that leads to an actuation, preferably switching on, of the semiconductor switch. In other words, the third, fourth and first resistors act in particular in the manner of a voltage divider. In summary, it is thus possible to realize that the semiconductor is actuated even if an electrical voltage other than 0 V is applied across the switching element. Thus, the switching element can also have a comparatively high internal resistance, or it can be operated in a current-limited mode. However, the signal contact reliably signals that electrical current is flowing. Only when the electrical voltage applied across the switching element increases further does the electrical potential applied at the signal contact change.

[0028] For example, only a single switching element is present, which is preferably designed to be bidirectional. Alternatively, the switching element is only unidirectional, and it is therefore only possible to use the switching unit for unidirectional operation. In a further development, a second switching element is present, which is expediently structurally identical to the switching element. The second switching element is connected between the ground connection and a second load connection. The third resistor is connected to the second load connection via a third diode. The blocking direction of the third diode is directed away from the second load connection. The signal contact thus also signals the switching state of the second switching element.

[0029] For example, the two load connections are separate from each other. Alternatively, the two load connections are electrically connected to each other with low resistance. These are preferably formed by a common (mechanical) terminal or the like, which is incorporated, for example, into the housing of the switching unit. The two switching elements are preferably each unidirectional and arranged opposite one another between the ground connection and the respective load connection. Consequently, the switching unit is capable of bidirectional operation, even if the two switching elements are only unidirectional. Due to the third diode, it is possible to use only the single semiconductor switch, which is why manufacturing costs are comparatively low.

[0030] In an alternative embodiment, for example, the third diode is not present, but the second switching element is. In this case, the switching unit is in particular designed to be at least partially mirrored. For example, a further semiconductor switch is expediently present, which is assigned to the second switching element. The further semiconductor switch, which is suitably structurally identical to the semiconductor switch, is connected in particular to the further load connection via its control input, and the two connections of the further semiconductor switch are connected to the ground connection and a further signal contact. This is preferably connected to a further first resistor, which is connected, for example, to the possible supply connection. Alternatively, the further first resistor is connected, for example, to the second load connection via a further second resistor.Conveniently, a further Zener diode is provided, via which the further second resistor is connected to the ground terminal. Alternatively, or in combination with this, the further first resistor is connected to a further third resistor, which is connected via a further first diode to the second load terminal and via a further fourth resistor and a further second diode to the control input of the further semiconductor switch.

[0031] For example, the load terminal is electrically connected to the ground terminal solely by means of the switching element. Alternatively, the switching element is bridged by means of a fourth resistor, such that the ground terminal is also electrically contacted with the load terminal by means of the fourth resistor. In this case, the resistance value of the fourth resistor is comparatively high, such that an electrical current flowing through the fourth resistor is comparatively low or negligible. The individual components of the switching unit, in particular any first, second and / or third resistor, are expediently designed such that the switching of the switching element already occurs at a comparatively low electrical voltage applied to the switching element.If the switching unit and any circuit in which the switching unit is used, or at least any load, are functioning properly, there is always an electrical potential at the control input, which is why the electrical potential at the signal contact corresponds to ground.

[0032] However, if ground is present as an electrical potential at the load terminal, for example, due to a broken wire, the semiconductor switch is open, so that the electrical potential at the signal contact does not correspond to ground. If, for example, a changed electrical voltage is present at the load terminal due to a cross-circuit / short circuit between conductors, this can also be read at the signal contact by selecting the appropriate resistors. In other words, the switching unit signals / checks whether the short circuit between conductors / short circuit is present.

[0033] The signal contact is connected to an LED, for example. The LED (light-emitting diode) is expediently incorporated into a housing of the switching unit so that the LED is also visible from outside the switching unit. If the first resistor is present, the LED is expediently connected between the first resistor and the semiconductor switch, with one contact of the LED being electrically connected to the signal contact. The other contact of the LED, however, is electrically connected to the first resistor. Thus, the signal contact is routed via the LED to the first resistor.

[0034] Alternatively or in combination, the switching unit preferably comprises any control unit which is guided against the signal contact. In particular, the control unit is electrically connected directly to the signal contact. During operation, the control unit checks whether the switching element is electrically conductive or electrically non-conductive. The control unit is particularly suitable, preferably provided and configured for this purpose. Suitably, the control unit is signal-connected to a communication input of the switching unit which is suitable, in particular provided and configured, for connection to a higher-level controller. Via the communication input, communication with the controller is carried out, in particular by means of the control unit, and in particular, it is communicated whether the switching element is closed or open.Alternatively, or in combination with this, the switching element is also operated by the control unit. This allows the control unit to directly check whether the switching element has been activated correctly or whether, for example, the switching element is malfunctioning. For example, the control unit can be discrete or comprise an integrated circuit.

[0035] The circuit has a voltage source that includes two power connections. In this case, an alternating voltage or preferably a direct voltage is provided by means of the voltage source, which is thus applied between the two power connections. In particular, the direct voltage provided is greater than 100 V. In addition, the circuit has a load, which is formed, for example, by an actuator. The circuit also includes a switching unit with a load connection and a ground connection, between which a switching element is connected. The switching unit further includes a semiconductor switch that has two connections and a control input. One connection is connected to the ground connection and the other to a signal contact, and the control input is connected to the load connection.

[0036] One of the power connections of the voltage source is electrically connected to ground, in particular directly. The other power connection of the voltage source, on the other hand, is connected to the load. The load, in turn, is connected to the load connection. One of the power connections is therefore electrically connected via the load to the load connection of the switching unit. For example, only the load is present, or there are other loads that are, for example, electrically connected in parallel and / or in series with the load. The ground connection of the switching unit is electrically connected to ground. When the switching element is closed, an electrical current flows and the load is operated. If, on the other hand, the switching element is open, the electrical current flow through the switching unit is prevented and the load is not operated.The circuit is, for example, a component of a system, such as an industrial plant or a telecommunications system. In particular, the switching unit serves, at least in part, to provide functional safety in the circuit.

[0037] The further developments and advantages explained in connection with the switching unit can also be transferred to the electrical circuit and vice versa.

[0038] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In the drawings:

[0039] Fig. 1 shows schematically a circuit with a load and a switching unit, and

[0040] Fig. 2 - 4 show a simplified circuit diagram of a variant of the switching unit. Corresponding parts are provided with the same reference numerals in all figures.

[0041] Figure 1 shows a simplified schematic of an electrical circuit 2 that is part of an industrial plant. The electrical circuit 2 comprises a load 4, which is a component of an actuator (not shown in detail). During operation, the actuator processes / creates a workpiece, and in the example shown, the load 4 is an electric motor. To operate the load 4, the electrical circuit 2 comprises a voltage source 6 that has two power connections 8. The voltage source 6 is provided by a rectifier, and an electrical direct voltage of several hundred volts is applied between the power connections 8.

[0042] One of the power connections 8 is electrically connected to ground 10, namely directly electrically connected to ground 10. The other power connection 8 is connected to the load 4. The load 4 is further connected to a load connection 12 of a switching unit 14, so that the load 4 is electrically connected between the load connection 12 and one of the power connections 8. The switching unit 14 further comprises a ground connection 16, which is directly electrically connected to ground 10. Thus, the ground connection 16 has the same electrical potential as one of the power connections 8. The load connection 12 and the ground connection 16 comprise terminals (not shown in detail) which are incorporated into a housing 18 of the switching unit 14.

[0043] A switching element 20, which is configured as a MOSFET and is arranged in the housing 18, is connected between the load terminal 12 and the ground terminal 16. If the switching element 20 is controlled in such a way that it is electrically conductive, the load terminal 12 and the ground terminal 16 are connected with low resistance. As a result, an electrical current can flow from one of the power terminals 8 via the load 4 and the switching unit 14 to ground 10. As a result, the load 4 is operated. If, however, the switching element 20 is controlled in such a way that it is electrically non-conductive, the current flow is interrupted, and the load 4 is not operated. The switching element 10 is controlled by means of a control unit 22, which is also arranged in the housing 18. The control unit 22 is connected for signaling purposes to a communication input (not shown), which is also incorporated in the housing 18.The control unit 22 is connected via the communication input to a higher-level controller of the circuit 2 (not shown in detail), which operates the actuator. The controller specifies whether the load 4 should be operated or not, and the control unit 22 controls the switching element 20 accordingly, i.e., opens or closes it. For this purpose, the control unit 22 applies a corresponding electrical potential to a control input of the switching element 20. However, it is possible that due to a malfunction, for example, material fatigue or aging, the switching state of the switching element 20 does not match the specification.

[0044] To check the actual switching state of the switching element 20, the switching unit 14 therefore comprises a semiconductor switch 24, which is designed as a transistor. The semiconductor switch 24 has two terminals 26, one of which is connected to the ground terminal 16. This terminal 26 is directly electrically connected to the ground terminal 16 and thus always has ground 10 as the electrical potential. The other terminal 26 is connected to a signal contact 28 and is directly electrically connected thereto. The signal contact 28, in turn, is directly electrically connected to the control unit 22, which has an integrated circuit (not shown in detail).

[0045] The signal contact 28 is further guided against a first resistor 30 and is electrically connected thereto for this purpose. The first resistor 30, in turn, is guided against a supply connection 32 and is electrically connected thereto. The supply connection 32 is thus connected to one of the connections 26 of the semiconductor switch 24 via the first resistor 30 and the signal contact 28. The supply connection 32 comprises a terminal (not shown in detail), which is introduced into the housing 18 and is electrically connected by means of a line to a second current connection 34 of a second voltage source 36. The second voltage source 36 has a total of two second current connections 34, with the remaining current connection 34 being electrically connected directly to ground 10. In this case, an electrical direct voltage of 12 V is provided by means of the second voltage source 34, which is present between the two second current connections 34.

[0046] The control unit 22 is also electrically contacted with the supply connection 32 and the ground connection 16, so that the control unit 22 is electrically supplied by means of the second voltage source 36.

[0047] The semiconductor switch 24 further has a control input 38, wherein, depending on the electrical potential applied to the control input 38, the two terminals 26 are electrically connected either with low or high resistance. In other words, the semiconductor switch 24 is opened or closed depending on the applied electrical potential. The control input 38 is routed to the load terminal 12 via a second diode 40, a fourth resistor 42, and a first diode 44 and is electrically connected directly to the load terminal 12.

[0048] The two diodes 40, 44 are structurally identical and mechanically arranged directly next to one another, so that they are thermally coupled. Thus, the two diodes 40, 44 have the same temperature and therefore essentially always exhibit the same behavior. The reverse bias of the two diodes 40, 44 differs from one another, with the reverse bias of the second diode 40 directed away from the control input 38. In contrast, the reverse bias of the first diode 44 is directed away from the load terminal 12. The switching unit 14 further comprises a third resistor 46, by means of which the first resistor 30 is connected to the first diode 44 and the fourth resistor 42.

[0049] If the switching element 20 is placed in the electrically conductive state by means of the control unit 22, the electrical potential at the load terminal 12 is essentially ground 10. A correction only occurs due to the internal resistance of the switching element 20, which is comparatively low. As a result, an electrical current flows from the one second current terminal 34, predominantly via the third resistor 46, the first diode 44, and the switching element 20 to ground 10. The dimensioning of the second resistor 46 ensures that only comparatively small electrical currents flow, so that electrical loss is low. At least essentially no current flows via the fourth resistor 42 and the second diode 40, and the electrical potential at the control input 38 is essentially ground 10, with a correction due to the fourth resistor 44. As a result, the semiconductor switch 24 is open.Therefore, the signal contact 28 has the electrical potential of the associated second power terminal 34 as its electrical potential, with correction being possible due to the first resistor 30. At least the electrical potential is different from ground 10.

[0050] If the switching element 20 is open, the electrical current flow from the associated second current terminal 34 to ground 10 is not possible via the switching element 20, which is why the electrical potential at the control input 38 is increased. This essentially corresponds to that of the associated second current terminal 34, with a correction being made due to the second diode 40, the fourth resistor 42, and the third resistor 46. The first diode 44 ensures that the voltage source 6 has no influence on the switching state of the semiconductor switch 40. Due to the increased electrical potential present at the control input 38, the semiconductor switch 24 is closed, so that the two terminals 26 are connected to one another with low resistance.As a result, an electrical current flows from the associated second power terminal 34 via the supply terminal 32, the first resistor 30, the semiconductor switch 24, and the ground terminal 16 to ground 10. By appropriately selecting the first resistor 30, it is ensured that the electrical current flowing here is also comparatively low. However, because the semiconductor switch 24 is closed, the electrical potential of the signal contact 28 is equal to ground 10, with a possible slight correction due to the internal resistance of the semiconductor switch 24. The dimensioning of the resistors 30, 46, 42 is such that, on the one hand, the flowing electrical currents are always comparatively low. On the other hand, they are selected such that the electrical potential of the signal contact 28 changes depending on whether the switching element 20 is electrically conductive or electrically non-conductive.

[0051] The switching state of switching element 20 is set during operation using the control unit 22. Subsequently, the electrical potential present at signal contact 28 is detected and used to check whether the switching state of switching element 20 corresponds to the setting. If a discrepancy exists, a warning message is output via the communication input, and switching element 20 is switched to the electrically non-conductive state. This attempts to shut down load 4 and transfer it to a safe state.

[0052] Figure 2 shows a modification of the switching unit 14. The switching element 20, which is connected between the ground connection 16 and the load connection 12, has not been changed. The semiconductor switch 24 with the two connections 26 is also still present, one of which is electrically contacted with the ground connection 26. The other connection 26 is electrically contacted via the signal contact 28 with the first resistor 30, which is also still connected to the first diode 44 and the fourth resistor 42 via the third resistor 46. The fourth resistor 42 is also connected between the first diode 44 and the second diode 40, which is electrically connected to the control input 38. The first diode 44 is also still connected to the load connection 12. The control unit 22 and the housing 18 are also still present, although these are not shown in detail here.

[0053] In contrast to the previous embodiment, the supply connection 32 is no longer present. Instead, the first resistor 30 is connected to the load connection 12 via a second resistor 48. In this case, the third resistor 46 is connected between the second resistor 48 and the fourth resistor 42. When the switching element 20 is open, an electrical potential is applied to the control input 38 that corresponds to the electrical potential of the power connection 8 assigned to the load connection 16, with a correction being made based on the load 4, the second resistor 48, the third resistor 46, and the fourth resistor 42. The resistors 42, 46, 48 are selected such that overloading of the semiconductor switch 24 is excluded, and in this case the semiconductor switch 24 is closed.When the semiconductor switch 24 is closed, the electrical current flows from the load terminal 12 via the second resistor 48, the first resistor 30 to the ground terminal 16. Due to the electrically conductive semiconductor switch 24, the electrical potential of the signal contact 28 is also essentially equal to ground 10. Thus, the functioning of this switching unit 14 essentially corresponds to that of the previous variant, wherein the supply terminal 32 is not present, which is why the second voltage source 36 is not required.

[0054] Additionally, a Zener diode 49 is provided, by means of which the second resistor 48 is connected to the ground terminal 16. The blocking direction of the Zener diode 49 is directed toward the ground terminal 16. The Zener diode 49 ensures that the electrical voltage applied to the semiconductor switch 24 is limited, so that the electrical potential applied to the signal contact 28 is also limited. This prevents destruction of the control unit 22 in the event of a malfunction of the load 4.

[0055] Figure 3 shows a further modification of the switching unit 14, which has all the components of the variant shown in Figure 1. In addition, a second switching element 50 is provided, which is structurally identical to the switching element 20. The second switching element 50 is connected between a second load terminal 52 and the ground terminal 16. In this case, the forward direction of the two switching elements 20, 50 is different, so that the switching unit 14, in contrast to the variant shown in Figure 1, is bidirectional. Furthermore, a third diode 54 is provided, with the third resistor 46 being connected to the second load terminal 52 via the third diode 54. The fourth resistor 42 is connected to the second load terminal 52 via the third diode 54, and the reverse direction of the third diodes 54 is directed away from the second load terminal 52.

[0056] Thus, depending on the current direction or to which load terminal 12, 52 the load 4 is connected, the semiconductor switch 24 is always reliably actuated when the two switching elements 20, 50 are open, so that the electrical potential applied to the signal contact 28 is changed.

[0057] In addition, an LED 56 is connected between the signal contact 28 and the first resistor 30. The signal contact 28 is connected to the LED 56. If the semiconductor switch 24 is electrically conductive, the LED 56 is energized, causing it to illuminate. If the semiconductor switch 24 is open, the LED 56 is not illuminated. Thus, the switching state of the two switching elements 20, 50 is also signaled by the LED 56. The LED 56 is inserted into an opening in the housing 18, so that the switching state is visible from outside the housing 18.

[0058] Figure 4 shows a further variant of the switching unit 14. This variant essentially corresponds to the embodiment shown in Figure 2, although it is largely a mirror image. This variant thus has all the components of the embodiment shown in Figure 2, with the additional second switching element 50 being present, which is connected between the ground connection 16 and the second load connection 52. There is also a further semiconductor switch 58 which is structurally identical to the semiconductor switch 24. This thus also has the two connections 26, one of which is electrically connected to the ground connection 16. The other connection 26 is electrically contacted with the second load connection 52 via a further signal contact 60 having a further first resistor 62, which is structurally identical to the first resistor 30, and a further second resistor 64, which is structurally identical to the second resistor 48.

[0059] The control input 38 of the further semiconductor switch 58 is electrically contacted with the second load terminal 52 via a further second diode 66, a further fourth resistor 68 and a further first diode 70.

[0060] These are each identical in construction to the second diode 40, the fourth resistor 42, and the first diode 44. A further third resistor 72 is also present, which is identical in construction to the third resistor 46 and whose arrangement corresponds to the arrangement of the third resistor 46. A further Zener diode 74 is also present, by means of which the further second resistor 46 is connected to the ground connection 16. In summary, this arrangement essentially corresponds to the bidirectional variant of Figure 2. In addition, the two switching elements 20, 50 are bridged by identical fourth resistors 76. The two fourth resistors 76 are designed with high resistance to keep power loss low.

[0061] The operation of the switching unit 14 essentially corresponds to the variant shown in Figure 2, and when the two switching elements 20, 50 are open, the electrical potential applied to the signal contacts 28, 60 is increased. If a cross-circuit / conductor short circuit occurs, the electrical potential at one of the two load connections 12, 52 is at least slightly different than the other. As a result, an electrical current flow between the two load connections 12, 52 is possible, namely via the fourth resistors 46. As a result, the electrical potential applied to the control inputs 28 is reduced, so that the semiconductor switches 24, 58 are placed in the electrically non-conductive state. Thus, the electrical potential applied to the signal contacts 28, 60 is increased, which is detected by the control unit 22. This variant of the switching unit 14 is thus capable of detecting a cross-circuit / conductor short circuit.The design of the individual electrical components of the switching unit 14 is adapted accordingly.

[0062] The invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived therefrom by those skilled in the art without departing from the subject matter of the invention. In particular, all individual features described in connection with the individual exemplary embodiments can also be combined with one another in other ways without departing from the subject matter of the invention. List of reference symbols

[0063] 2 circuits

[0064] 4 Last

[0065] 6 Voltage source

[0066] 8 Power connection

[0067] 10 Mass

[0068] 12 Load connection

[0069] 14 Switching unit

[0070] 16 Ground connection

[0071] 18 housings

[0072] 20 switching element

[0073] 22 Control unit

[0074] 24 semiconductor switches

[0075] 26 connection

[0076] 28 Signal contact

[0077] 30 first resistance

[0078] 32 supply connection

[0079] 34 second power connection

[0080] 36 second voltage source

[0081] 38 Control input

[0082] 40 second diode

[0083] 42 fourth resistance

[0084] 44 first diode

[0085] 46 third resistance

[0086] 48 second resistance

[0087] 49 Zener diode

[0088] 50 second switching element

[0089] 52 second load connection

[0090] 54 third diode

[0091] 56 LED

[0092] 58 additional semiconductor switches

[0093] 60 further signal contact 62 further first resistor

[0094] 64 further second resistance

[0095] 66 further second diode

[0096] 68 further fourth resistor 70 further first diode

[0097] 72 further third resistance

[0098] 74 additional Zener diodes

[0099] 76 fourth resistance

Claims

Claims 1. Switching unit (14) with a load terminal (12) and a ground terminal (16), between which a switching element (20) is connected, and with a semiconductor switch (24) which has two terminals (26) and a control input (38), wherein one terminal (26) is guided against the ground terminal (16) and the other against a signal contact (28), and wherein the control input (38) is guided against the load terminal (12).

2. Switching unit (14) according to claim 1, characterized in that the signal contact (28) is guided against a first resistor (30).

3. Switching unit (14) according to claim 2, characterized in that the first resistor (30) is connected to a supply terminal (32).

4. Switching unit (14) according to claim 2, characterized in that the first resistor (30) is connected to the load terminal (12) via a second resistor (48).

5. Switching unit (14) according to claim 4, characterized in that the second resistor (48) is connected to the ground terminal (16) via a Zener diode (49).

6. Switching unit (14) according to one of claims 2 to 5, characterized in that the first resistor (30) is connected to a third resistor (46) which is connected via a first diode (44) to the load terminal (12) and via a fourth resistor (42) and a second diode (40) is connected to the control input (38).

7. Switching unit (14) according to claim 6, characterized by a second switching element (50) which is connected between the ground terminal (16) and a second load terminal (52), wherein the third resistor (46) is connected to the second load terminal (52) via a third diode (54).

8. Switching unit (14) according to one of claims 1 to 7, characterized in that the switching element (20) is bridged by means of a fourth resistor (76).

9. Switching unit (14) according to one of claims 1 to 8, characterized in that the signal contact (28) is connected to an LED (56) and / or to a control unit (20).

10. Circuit (2) with a load (4), with a voltage source (6) which has two current connections (8), and with a switching unit (14) according to one of claims 1 to 9, wherein one of the current connections (8) is electrically connected to ground (10) and the other current connection (8) is led to the load (4), which is led to the load connection (12), wherein the ground connection (16) is electrically connected to ground (10).

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