Switch unit

Abstract

The invention relates to a switching unit (14), comprising: a load connection (12) and a zero potential connection (16), between which a switching element (20) is connected; a semiconductor switch (24) having two terminals (26) and a control input (38). Wherein one connection (26) is guided to the zero potential connection (16) and the other connection is guided to the signal contact (28), and the control input (38) is guided to the load connection (12). The invention also relates to a current circuit (2).

Description

Technical Field

[0001] This invention relates to a switching unit having a load terminal and a zero-potential terminal, with a switching element connected between them. The invention also relates to a current loop. Background Technology

[0002] Facilities, such as industrial facilities, typically have one or more actuators used to perform tasks. In industrial facilities, actuators are used, for example, to create and / or process workpieces. To ensure the actuator operates as desired, a control unit is provided for adjusting the power supply to the actuator. In the simplest case, a switching element operated by the control unit is present. Here, the actuator is switched on and off using the switching element. For this purpose, the switching element is introduced into the actuator's power supply line.

[0003] If the function performed by an actuator may endanger other machines and / or operators, functional safety is necessary. Thus, in an emergency, the actuator's intended function should be terminated, and a safe state should be established. This often requires de-energizing the actuator, thereby disconnecting the switching elements. For example, when performing maintenance on the actuator, it is also necessary to disable it, i.e., disconnect the switching elements. Therefore, in both applications, it is essential to ensure that the actuator is not energized to eliminate any further risks.

[0004] Therefore, in principle, the current guided by the supply line would be measured. However, this supply line often carries relatively high current and / or voltage, making such measuring equipment relatively expensive. Furthermore, the measuring equipment may also be damaged when the actuator fails and reacts against the supply line. In this case, it is impossible to reliably determine whether the actuator is truly no longer being powered.

[0005] To verify whether the actuator is currently energized, the switching state of the switching element may also be checked. As a switching element, a mechanical switch is often used, which has two movable contacts, one of which is typically connected to a contact bridge supported in a movable manner. When the switching element is conductive, the contacts are mechanically pressed together, and current for energizing the actuator is guided through the contacts. To disconnect the switching element, the contacts are spaced apart, for which the contact bridge moves.

[0006] An auxiliary contact is typically connected at the contact bridge. When the contact bridge moves, this auxiliary contact disengages from another auxiliary contact, interrupting the current flow in the auxiliary current loop introduced by the auxiliary contact. By checking whether current flows in the auxiliary current loop, it is possible to determine whether the switching element is open or closed. Here, the checking of the auxiliary current loop is simplified because the current guided by the auxiliary loop is relatively small and / or the voltage present is relatively small. Furthermore, the auxiliary loop may also be electrically isolated from the power supply line, further enhancing safety.

[0007] In verifying the switching state of such switching elements, a relatively complex mechanical switch is required, which has at least two additional auxiliary contacts. Conversely, the application of semiconductor switches is not feasible because it is impossible to simultaneously disconnect two independent current loops. The use of mechanical switches makes it possible for an electric arc to form upon disconnection, which could cause the contacts to fuse, preventing them from disconnecting again. Manufacturing costs are also relatively high. Summary of the Invention

[0008] The objective of this invention is to provide a particularly suitable switching unit and a particularly suitable current loop, wherein manufacturing costs are advantageously reduced and, in particular, safety is improved.

[0009] Regarding the switching unit, this task is solved by the features of claim 1; regarding the current loop, this task is solved by the features of claim 10. Advantageous improvements and designs are the subject of the dependent claims.

[0010] A switching unit is, for example, a component of a facility used to perform a specific function. In particular, this facility is an industrial facility and is used, for example, to manufacture and / or process specific workpieces. For this purpose, the facility particularly has an actuator. The actuator can be, for example, an electric motor, such as a rotary electric motor or a linear motor. Alternatively, the actuator can be, for example, an electrically operated valve. In another alternative, the facility can be, for example, a communication facility or a computing center.

[0011] Here, the switching unit is suitable, and particularly configured, for interrupting or establishing current flow. Here, the current driven under normal conditions, and particularly equivalent 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, the rated voltage of the switching unit (especially the rated voltage present at the switching unit when it is not in a non-conductive state) 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 voltage is either DC or AC.

[0012] The switching unit has a load terminal and a zero-potential terminal, with a switching element connected between them. When the switching element is conductive, i.e., closed, the load terminal and the zero-potential terminal are in low-ohmic contact with each other. Conversely, when the switching element is open, i.e., non-conductive, the load terminal and the zero-potential terminal are only connected in high ohms, making it impossible for current to flow between them. Here, the zero-potential terminal is suitable, especially configured and arranged to have a ground potential on it. Conversely, the load terminal is suitable, especially configured and arranged to connect to a load. In the assembled state, the load terminal is electrically connected to a voltage source via the load. Here, when the switching element is conductive, i.e., closed, the load is energized. Conversely, if the switching element is open, the energization of the load is interrupted.

[0013] For example, the switching element is a mechanical switch, such as a relay. However, preferably, the switching element is designed as a semiconductor switch, and in particular, has a relatively high current-carrying capacity. Suitably, the switching element is a field-effect transistor, preferably a MOSFET, IGBT, or GTO.

[0014] The switching unit also includes a semiconductor switch independent of the switching element. In other words, the semiconductor switch is a component independent of the switching element, and it is provided by means of a semiconductor element. The semiconductor switch has two terminals, which are connected to each other at a low ohm when the semiconductor switch is conducting. Conversely, if the semiconductor switch is off, the two terminals are connected to each other at a high ohm. Furthermore, the semiconductor switch also has a control input terminal. Here, by means of a specific potential present at the control input terminal, the semiconductor switch can be placed in a conducting or non-conducting state. Suitably, the semiconductor switch is a transistor. At least, the current-carrying capacity of the semiconductor switch is preferably lower than that of the switching element, thereby reducing manufacturing costs.

[0015] One terminal of the semiconductor switch is directed to a zero-potential terminal. The other terminal is directed to a signal contact of the switching unit. Preferably, this terminal is in direct electrical contact with the signal contact, and there are no one or more electrical / electronic components arranged between them, for example, in at least partially in series and / or in parallel with each other. When the semiconductor switch is conducting, the signal contact is at the same potential as the zero-potential terminal, i.e., specifically at zero potential in electrical terms, or at least at a potential determined by means of zero potential. Conversely, when the semiconductor switch is off, the potential of the signal contact is different from and / or particularly unrelated to zero potential.

[0016] The control input of the semiconductor switch is directed to the load terminal. Here, for example, the control input may be directly electrically connected to the load terminal, or another electrical / electronic component may be arranged between them. At a minimum, the potential at the control input is related to the potential at the load terminal.

[0017] Therefore, if the switching element is electrically closed, the load terminal has the same potential as the zero-potential terminal. As a result, a potential corresponding to the zero-potential terminal exists at the control input, and the semiconductor switch is specifically configured to subsequently be open. Thus, the potential of the signal contact differs from the zero potential. Conversely, if the switching element is not conductive, the potential at the load terminal differs from the potential at the zero-potential terminal. Thus, the potential at the control input also changes. Here, the semiconductor switch is specifically designed to subsequently be conductive. Therefore, a zero potential exists at the signal contact, or at least corresponds to a zero potential.

[0018] In summary, this interconnection enables the determination of whether a switching element is conductive or non-conductive based on the potential present at the signal contact, thus improving safety. The requirements for the switching element are relatively low, thereby reducing manufacturing costs. Furthermore, the use of semiconductors as the switching element further reduces manufacturing costs.

[0019] Suitablely, the switching unit includes a housing into which one or more terminal clips are introduced. Here, one terminal clip is suitably electrically connected to a zero-potential terminal, and another terminal clip is electrically connected to a load terminal, thereby enabling connection of the corresponding potential from outside the housing, thus simplifying assembly. Alternatively or in combination, for example, signal contacts can be sensed at least indirectly from outside the housing.

[0020] For example, the switching element is configured as a mechanical switch, which can only be operated manually. Alternatively, the switching element may have a drive input via which the switching unit is operated. Suitablely, the switching state of the switching element depends on a change in the potential present at the drive input. Thus, it is possible to adjust the current flow between the load terminal and the zero-potential terminal remotely from the switching unit, especially within the framework of process control. Preferably, the switching element is a semiconductor. In an improved embodiment, the switching unit is, for example, part of a protective switch, wherein the switching element operates particularly dependent on fault conditions (e.g., overcurrent, short-circuit current, overvoltage, or other faults, such as possible load failure).

[0021] Preferably, the signal contact is directed to a first resistor. Here, in particular, an additional electrical component is arranged between the signal contact and the first resistor, or the signal contact is directly electrically connected to the first resistor. This first resistor, in particular, ensures that the current directed by the semiconductor switch is relatively small when the semiconductor switch is conducting. Therefore, safety is improved and electrical losses are reduced. Furthermore, this method further reduces the load on the switching element, allowing the switching element to be designed relatively inexpensively.

[0022] For example, a first resistor is directed to a power supply terminal. In the assembled state / when using the switching unit, preferably, the potential present at the power supply terminal is suitably kept constant over time. Here, in particular, the voltage between the zero-potential terminal and the power supply terminal is less than 50 V, 20 V, 10 V, or 5 V, thus further reducing the requirements for the first resistor, signal contacts, and semiconductor switches, thereby lowering manufacturing costs. Suitably, the switching unit includes a terminal clamp electrically connected to the power supply terminal and, in particular, introduced into a possible housing. Therefore, a corresponding potential can be applied to the power supply terminal from outside the housing.

[0023] Preferably, a control unit is provided that is electrically connected to the power supply terminal. This control unit also operates based on the potential present there. This reduces susceptibility to failure and makes it possible for the control unit to operate independently of the voltage between the zero-potential terminal and the load terminal. Preferably, the switching element is operated by means of the control unit.

[0024] In an alternative solution, the first resistor is connected to the load terminal via the second resistor. This eliminates the need for a separate power supply terminal, simplifying assembly and reducing manufacturing costs. When the semiconductor switch is open, the potential at the signal contact corresponds to the potential at the load terminal. These two resistors ensure that the current flowing from the load terminal to the zero-potential terminal via the semiconductor switch is relatively small, thus reducing the load on the semiconductor switch. This also ensures that when the switching element is open, it does not unintentionally energize any potential load connected to the load terminal. Because the two resistors are connected in series, the requirements for individual resistors are reduced, allowing these resistors to be designed to be relatively small and inexpensive.

[0025] Preferably, the second resistor is guided to the zero-potential terminal via a Zener diode. Here, the Zener diode is suitably positioned away from the zero-potential terminal. In this configuration, the Zener diode is connected in parallel with a series circuit consisting of the first resistor and a semiconductor switch. Furthermore, the Zener diode is connected in electrical parallel with a series circuit consisting of the second resistor and a switching element. The Zener diode, in particular, prevents the formation of overvoltages that could damage the switching element or semiconductor switch. Here, the second resistor ensures that the maximum current flowing through the Zener diode is relatively small, thus allowing the use of relatively low-cost components.

[0026] Preferably, the first resistor is connected to the third resistor. Suitablely, the first resistor can be directly electrically connected to the third resistor. The third resistor is then connected to the load terminal via a first diode. Furthermore, the third resistor is connected to the control input terminal via a fourth resistor and a second diode.

[0027] Here, the two diodes and the fourth resistor are preferably connected in series. The cutoff directions of the two diodes are, in particular, opposite to each other, with the cutoff direction of the second diode pointing from the control input terminal toward the fourth resistor. Specifically, the two diodes are structurally identical, thus reducing manufacturing costs. This also improves the functionality of the switching unit. Preferably, the two diodes are thermally connected to each other and are suitably arranged side-by-side. In this way, the two diodes essentially always have the same behavior. Here, for example, the first resistor is directed to the power supply terminal, thereby causing the third resistor to also be directed to the power supply terminal. Alternatively, a second resistor is present, and the third resistor is also directed to the second resistor.

[0028] By using the fourth and third resistors, the voltage level that causes the semiconductor switch to be operated (preferably turned on) can be adjusted. In other words, the third, fourth, and first resistors act primarily as voltage dividers. In short, this allows for semiconductor operation even when a voltage other than 0 V exists on the switching element. Therefore, a relatively high internal resistance can exist in the switching element, or the switching element can operate in a current-limiting mode. However, the presence of current flow is reliably indicated by a signal at the signal contact. The potential at the signal contact only changes as the voltage applied via the switching element increases further.

[0029] For example, there is only one switching element, which is preferably designed to be bidirectional. Alternatively, the switching element is unidirectional, meaning the switching unit can only be used for unidirectional operation. In an improved embodiment, a second switching element is provided, preferably with the same structure as the first switching element. The second switching element is connected between the zero-potential terminal and the second load terminal. Here, a third resistor is guided to the second load terminal via a third diode. The cutoff direction of the third diode points away from the second load terminal. Thus, the switching state of the second switching element is also indicated by a signal contact.

[0030] For example, these two load terminals are independent of each other. Alternatively, these two load terminals may be in low-ohmic electrical contact with each other. Preferably, these load terminals are formed by means of a common (mechanical) clamp or similar structure, for example, introduced into a possible housing of the switching unit. Here, both switching elements are preferably constructed to be unidirectional and arranged opposite to each other between the zero-potential terminal and their respective load terminals. Therefore, even though the two switching elements are designed to be unidirectional only, the switching unit still has the ability to operate bidirectionally. Here, due to the presence of a third diode, it is possible to use only a single semiconductor switch, thus resulting in relatively low manufacturing costs.

[0031] In an alternative design, for example, a third diode is absent, but a second switching element is present. Here, the switching unit is designed to be at least partially mirror-image. Therefore, it is suitable to have an additional semiconductor switch associated with the second switching element. This additional semiconductor switch (suitably having the same structure as the semiconductor switch) is directed to an additional load terminal via its control input, and its two terminals are directed to a zero-potential terminal and an additional signal contact. Preferably, this additional signal contact is directed to an additional first resistor, which, for example, is directed to a possible power supply terminal. Alternatively, for example, the additional first resistor is directed to the second load terminal via an additional second resistor. Suitablely, an additional Zener diode is present, and the additional second resistor is directed to the zero-potential terminal via this additional Zener diode. Alternatively, or in combination, the additional first resistor is directed to an additional third resistor, which is directed to the second load terminal via the additional first diode and to the control input of the additional semiconductor switch via an additional fourth resistor and an additional second diode.

[0032] For example, the load terminal is electrically connected to the zero-potential terminal only by means of a switching element. Alternatively, the switching element is bridged by a fourth resistor, so that the zero-potential terminal is also electrically contacted with the load terminal by means of the fourth resistor. Here, the resistance of the fourth resistor is relatively high, so that the current flowing through the fourth resistor is relatively small or negligible. The various components of the switching unit (especially the possible first, second, and / or third resistors) are suitably constructed such that the switching element is switched when the voltage present at the switching element is relatively low. If the switching unit and the possible current loop using the switching unit, or at least the possible load, function as intended, a potential is always present at the control input, thus making the potential present at the signal contact correspond to zero potential.

[0033] However, if there is zero potential at the load terminals, for example due to a broken circuit, the semiconductor switch is open, causing the potential at the signal contacts to not correspond to zero potential. For example, if the voltage at the load terminals changes due to a cross-short circuit / conductor short circuit, this change can also be detected at the signal contacts by using a corresponding selected resistor. In other words, the presence of a conductor short circuit / cross-short circuit is indicated / checked by the switching unit.

[0034] The signal contact is connected, for example, to an LED. Suitably, the LED (“light-emitting diode”) is incorporated into the housing of the switching unit so that it is visible from outside the switching unit. If a first resistor is present, the LED is suitably connected between the first resistor and the semiconductor switch, wherein suitably, one contact of the LED is in electrical contact with the signal contact, while the other contact of the LED is in electrical contact with the first resistor. In this way, the signal contact is guided to the first resistor via the LED.

[0035] Alternatively or in combination, the switching unit preferably includes a control unit that is directed to the signal contacts. In particular, the control unit is directly electrically connected to the signal contacts. During operation, the control unit checks whether the switching element is conductive or non-conductive. The control unit is particularly suitable for, and preferably configured for, this purpose. Suitablely, the control unit is connected to a communication input of the switching unit via signal technology, which is suitable for, and preferably configured for, connecting to a higher-level control unit. Here, in particular, communication with the control unit is performed via the communication input by means of the control unit, and especially to convey whether the switching element is closed or open. Alternatively or in combination, the control unit also operates the switching element. In this way, the control unit can directly check whether the drive of the switching element is correctly implemented, or, for example, whether the switching element is faulty. For example, the control unit is discretely configured or, for example, has an integrated current loop.

[0036] The current loop has a voltage source comprising two current terminals. Here, an AC voltage, or preferably a DC voltage, is provided by the voltage source and is thus present between the two current terminals. In particular, the provided DC voltage is greater than 100 V. Furthermore, the current loop also has a load, such as a load formed by an actuator. The current loop also includes a switching unit having a load terminal and a zero-potential terminal, with a switching element connected between them. The switching unit also includes a semiconductor switch having two terminals and a control input. One terminal is directed to the zero-potential terminal, and the other terminal is directed to a signal contact, and the control input is directed to the load terminal.

[0037] One current terminal of the voltage source is electrically connected to zero potential, particularly directly, while another current terminal of the voltage source is directed to the load, which in turn is directed to the load terminal. Thus, one current terminal is electrically connected to the load terminal of the switching unit via the load. Here, for example, only the load is present, or for example, there are other loads connected in parallel and / or in series with the load. The zero-potential terminal of the switching unit is electrically connected to zero potential. Therefore, when the switching element is closed, current flows, and the load operates. Conversely, if the switching element is open, the current flow through the switching unit is interrupted, and the load does not operate. The current loop is, for example, a component of a facility (such as an industrial or telecommunications facility). In particular, the switching unit is at least partially used to provide functional safety in the current loop.

[0038] The improvements and advantages described in the explanation of the switching unit are also applied to the current loop in a meaningful way, and vice versa. Attached Figure Description

[0039] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the drawings: Figure 1 A schematic diagram illustrates a current loop with a load and a switching unit; and Figures 2 to 4 Simplified circuit diagrams are shown for each variant of the switching unit.

[0040] Corresponding parts are labeled with the same reference numerals in all figures. Detailed Implementation

[0041] Figure 1 The simplified schematic diagram illustrates a current loop 2, which is a component of an industrial facility. Current loop 2 includes a load 4, which is part of an actuator (not shown). During operation, the actuator processes / creates a workpiece, and in the example shown, load 4 is an electric motor. To operate load 4, current loop 2 includes a voltage source 6 with two current terminals 8. Voltage source 6 is provided by means of a rectifier, and a DC voltage of several hundred volts exists between the current terminals 8.

[0042] One current terminal 8 is directed to zero potential 10, i.e., directly electrically connected to zero potential 10. The other current terminal 8 is directed to load 4. Load 4 is also directed to load terminal 12 of the switching unit 14, thereby electrically connecting load 4 between load terminal 12 and current terminal 8. The switching unit 14 also includes a zero potential terminal 16, which is directly electrically connected to zero potential 10. In this respect, the zero potential terminal 16 has the same potential as one of the current terminals 8. Load terminal 12 and zero potential terminal 16 include terminal clips (not shown in detail) introduced into the housing 18 of the switching unit 14.

[0043] A switching element 20, designed as a MOSFET, is disposed within the housing 18 and connected between the load terminal 12 and the zero-potential terminal 16. When the switching element 20 is driven to conduct, the load terminal 12 and the zero-potential terminal 16 are connected at a low ohm. Therefore, current flows from one of the current terminals 8 through the load 4 and the switching unit 14 to the zero-potential terminal 10, resulting in the operation of the load 4. Conversely, if the switching element 20 is driven to deconduct, the current flow is interrupted, and the load 4 does not operate.

[0044] The control of the switching element 10 is performed by a control unit 22, which is also arranged in the housing 18. The control unit 22 is connected via signal technology to a communication input terminal (not shown) also introduced into the housing 18. The control unit 22 is connected via the communication input terminal to an upper-level control unit (not shown in detail) of the current loop 2, thereby enabling the actuator to operate. Here, the control unit determines whether the load 4 should operate, and the control unit 22 accordingly controls the switching element 20, i.e., opens or closes the switching element. For this purpose, the control unit 22 applies a corresponding potential to the control input terminal of the switching element 20. However, due to malfunctions, such as material fatigue or aging, the switching state of the switching element 20 may not be consistent with the preset state.

[0045] To verify the actual switching state of the switching element 20, the switching unit 14 therefore includes 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 zero-potential terminal 16. Here, this terminal 26 is in direct electrical contact with the zero-potential terminal 16, thus always having zero potential 10 as its potential. The other terminal 26 is connected directly to and electrically to a signal contact 28. The signal contact 28 is in turn directly connected to a control unit 22, which has an integrated current loop (not shown in detail).

[0046] Furthermore, signal contact 28 is also guided to and directly electrically connected to first resistor 30. First resistor 30 is in turn guided to and directly electrically connected to power supply terminal 32. Thus, power supply terminal 32 is connected to one of the terminals 26 of semiconductor switch 24 via first resistor 30 and signal contact 28. Power supply terminal 32 includes a terminal clip (not shown in detail) that is inserted into housing 18 and electrically connected via a line to the second current terminal 34 of second voltage source 36. Second voltage source 36 has a total of two second current terminals 34, with the remaining current terminal 34 directly electrically connected to zero potential 10. Here, a 12 V DC voltage is provided between the two second current terminals 34 by means of second voltage source 34.

[0047] Here, the control unit 22 is also electrically connected to the power supply terminal 32 and the zero potential terminal 16, so that the control unit 22 is powered by the second voltage source 36.

[0048] The semiconductor switch 24 also has a control input terminal 38, wherein, depending on the potential present at the control input terminal 38, the two terminals 26 are either electrically connected at a low ohm or at a high ohm. In other words, depending on the present potential, the semiconductor switch 24 is either open or closed. The control input terminal 38 is guided to and directly electrically connected to the load terminal 12 via the second diode 40, the fourth resistor 42, and the first diode 44.

[0049] Two diodes 40 and 44 are identical in structure and are mechanically arranged side-by-side, thus thermally coupling them together. Consequently, the two diodes 40 and 44 have the same temperature and therefore exhibit essentially the same behavior. Here, the cutoff directions of the two diodes 40 and 44 are different, with the cutoff direction of the second diode 40 pointing away from the control input terminal 38. Conversely, the cutoff direction of the first diode 44 points away from the load terminal 12. The switching unit 14 also includes a third resistor 46, by which the first resistor 30 is directed to the first diode 44 and the fourth resistor 42.

[0050] If the switching element 20 is placed in a conductive state by means of the control unit 22, then a essentially zero potential 10 exists at the load terminal 12. A relatively small correction occurs only due to the internal resistance of the switching element 20. As a result, current flows from one of the second current terminals 34, preferably via the third resistor 46, the first diode 44, and the switching element 20, to the zero potential 10. Here, due to the design specifications of the second resistor 46, only a relatively small current flows, resulting in less electrical loss. At least, there is essentially no current flowing through the fourth resistor 42 and the second diode 40, and the potential at the control input terminal 38 is essentially the zero potential 10, which is corrected due to the fourth resistor 44. As a result, the semiconductor switch 24 is in an open state. Therefore, the potential of the signal contact 28 is the potential of the associated second current terminal 34, which may be corrected due to the first resistor 30. At least, this potential differs from the zero potential 10.

[0051] If the switching element 20 is open, the current flow from the associated second current terminal 34 to the zero potential 10 cannot pass through the switching element 20, thus raising the potential at the control input terminal 38. This potential essentially corresponds to the associated second current terminal 34, with corrections due to the second diode 40, the fourth resistor 42, and the third resistor 46. Here, the first diode 44 ensures that the voltage source 6 does not affect the switching state of the semiconductor switch 40. Due to the potential rise at the control input terminal 38, the semiconductor switch 24 closes, thereby connecting the two terminals 26 to each other at a low ohm. As a result, current flows from the associated second current terminal 34 to the zero potential 10 via the power supply terminal 32, the first resistor 30, the semiconductor switch 24, and the zero potential terminal 16. Here, by appropriately selecting the first resistor 30, it is ensured that the current flowing through this point is also relatively small. However, since the semiconductor switch 24 is closed, the potential of the signal contact 28 is the same as the zero potential 10, with slight corrections due to the internal resistance of the semiconductor switch 24 if necessary.

[0052] Here, the specifications of resistors 30, 46, and 42 are designed such that, on the one hand, the current flowing through them is always relatively small; on the other hand, these resistors are selected so that the potential change of the signal contact 28 depends on whether the switching element 20 is in a conductive or non-conductive state.

[0053] During operation, the switching state of the switching element 20 is set using the control unit 22. Then, the potential at the signal contact 28 is detected, and the switching state of the switching element 20 is checked against the set value based on this potential. If a discrepancy exists, a warning message is issued via the communication input, and the switching element 20 is placed in a non-conductive state. At this point, an attempt is made to stop the load 4 and transfer it to a safe state.

[0054] Figure 2 A modified version of the switching unit 14 is shown. The switching element 20 connected between the zero-potential terminal 16 and the load terminal 12 remains unchanged. Furthermore, a semiconductor switch 24 with two terminals 26 is also present, one of which is electrically contacted with the zero-potential terminal 26. The other terminal 26 is electrically contacted via a signal contact 28 with a first resistor 30, which is also guided to a first diode 44 and a fourth resistor 42 via a third resistor 46. The fourth resistor 42 is similarly connected between the first diode 44 and a second diode 40, which is electrically connected to the control input terminal 38. Furthermore, the first diode 44 is also guided to the load terminal 12. Additionally, a control unit 22 and a housing 18 are present, but they are not shown in detail.

[0055] Unlike the aforementioned design, the power supply terminal 32 is no longer present. Instead, the first resistor 30 is guided to the load terminal 12 via the second resistor 48. Here, the third resistor 46 is connected between the second resistor 48 and the fourth resistor 42. When the switching element 20 is open, the potential at the control input terminal 38 corresponds to the potential of the current terminal 8 associated with the load terminal 16, which is corrected by the load 4, the second resistor 48, the third resistor 46, and the fourth resistor 42. Here, resistors 42, 46, and 48 are selected such that overload of the semiconductor switch 24 is prevented, and in this case, the semiconductor switch 24 is closed. When the semiconductor switch 24 is closed, current flows from the load terminal 12 through the second resistor 48 and the first resistor 30 to the zero potential terminal 16. Since the semiconductor switch 24 is conductive, the potential of the signal contact 28 is also essentially equal to the zero potential 10. In this respect, the functionality of the switching unit 14 is basically consistent with the aforementioned variant, but it does not have a power supply terminal 32, so there is no need for a second voltage source 36.

[0056] In addition, a Zener diode 49 is provided to guide the second resistor 48 to the zero-potential terminal 16. The Zener diode 49 is pointed in the cutoff direction toward the zero-potential terminal 16. The Zener diode 49 ensures that the voltage at the semiconductor switch 24 is limited, thereby limiting the potential at the signal contact 28. This prevents damage to the control unit 22 in the event of a load 4 failure.

[0057] Figure 3 The diagram shows an additional modification to the switching unit 14, which has... Figure 1 All components of the variant shown are included. Additionally, a second switching element 50 with the same structure as switching element 20 is present. The second switching element 50 is connected between the load terminal 52 and the zero-potential terminal 16. Here, the two switching elements 20 and 50 have different conduction directions, thus differing from... Figure 1 In the variant shown, the switching unit 14 is designed to be bidirectional. Furthermore, a third diode 54 is present, through which the third resistor 46 is directed to the second load terminal 52. Here, a fourth resistor 42 is directed to the second load terminal 52 via the third diode 54, and the cutoff direction of the third diode 54 points away from the second load terminal 52.

[0058] Therefore, depending on the direction of the current or which load terminals 12 and 52 the load 4 is connected to, the semiconductor switch 24 is always reliably operated when the two switching elements 20 and 50 are open, thereby causing a change in the potential present at the signal contact 28.

[0059] Furthermore, an LED 56 is connected between the signal contact 28 and the first resistor 30. Here, the signal contact 28 is directed to the LED 56. If the semiconductor switch 24 is in a conductive state, the LED 56 is energized, thereby lighting it. If the semiconductor switch 24 is in an open state, the LED 56 is not lit. In this way, the LED 56 also indicates the switching state of the two switching elements 20 and 50 by means of a signal. Here, the LED 56 is placed in the opening of the housing 18, so that the switching state can be seen from outside the housing 18.

[0060] Figure 4 Another variant of the switching unit 14 is shown. This variant is essentially the same as... Figure 2 The embodiment shown is corresponding, but it is mostly mirrored. In this respect, this variant has... Figure 2All components of the embodiment shown herein additionally include a second switching element 50 connected between the zero-potential terminal 16 and the second load terminal 52. Furthermore, there is an additional semiconductor switch 58 with the same structure as semiconductor switch 24. This additional semiconductor switch also has two terminals 26, one of which is electrically connected to the zero-potential terminal 16. The other terminal 26 is electrically contacted via an additional signal contact 60 to an additional first resistor 62 (which has the same structure as first resistor 30), and via an additional second resistor 64 (which has the same structure as second resistor 48) to the second load terminal 52.

[0061] The control input terminal 38 of the additional semiconductor switch 58 is electrically contacted with the second load terminal 52 via an additional second diode 66, an additional fourth resistor 68, and an additional first diode 70, which have the same structure as the second diode 40, the fourth resistor 42, and the first diode 44, respectively. Furthermore, there is an additional third resistor 72, which has the same structure as the third resistor 46, and its arrangement corresponds to that of the third resistor 46. Additionally, there is an additional Zener diode 74 used to guide the additional second resistor 46 to the zero-potential terminal 16. In summary, this arrangement is essentially the same as... Figure 2 The variant of the bidirectional design shown corresponds accordingly. Additionally, the two switching elements 20, 50 are bridged by a fourth resistor 76, which is identical in construction to each other. These two fourth resistors 76 are designed to be high-ohm, thereby maintaining low power loss.

[0062] The functionality of the switching unit 14 is basically corresponding to Figure 2 The variant shown in the diagram, where the potential at signal contacts 28 and 60 increases when both switching elements 20 and 50 are open, indicates a potential increase. If a cross-short circuit / conductor short circuit exists, the potential at one of the two load terminals 12 and 52 will change at least slightly relative to the other. Therefore, current may flow between the two load terminals 12 and 52, i.e., current may flow through the fourth resistor 46. As a result, the potential at control input 28 decreases, causing semiconductor switches 24 and 58 to be in a non-conductive state. This results in a potential increase at signal contacts 28 and 60, which is detected by the control unit 22. Thus, this variant of the switching unit 14 is capable of detecting cross-short circuits / line short circuits. The design of the various electrical components of the switching unit 14 is adjusted accordingly.

[0063] This invention is not limited to the embodiments described above. Rather, other variations of the invention can be derived by those skilled in the art without departing from its subject matter. In particular, all the individual features described in connection with the various embodiments can be combined with each other in other ways without departing from the subject matter of the invention.

[0064] List of reference numerals

[0065] 2 Current loop

[0066] 4. Load

[0067] 6. Voltage source

[0068] 8 Current terminals

[0069] 10 Zero potential

[0070] 12 Load terminals

[0071] 14 Switching Unit

[0072] 16 Zero Potential Terminals

[0073] 18. Shell

[0074] 20 Switching elements

[0075] 22 Control Unit

[0076] 24 Semiconductor Switches

[0077] 26 terminals

[0078] 28 signal contacts

[0079] 30 First Resistor

[0080] 32 power supply terminals

[0081] 34 Second Current Terminal

[0082] 36 Second voltage source

[0083] 38 Control Input Terminal

[0084] 40 Second Diode

[0085] 42 Fourth Resistor

[0086] 44 First Diode

[0087] 46 Third Resistor

[0088] 48 Second Resistor

[0089] 49 Zener diode

[0090] 50 Second Switching Element

[0091] 52 Second load terminal

[0092] 54 Third Diode

[0093] 56 LED

[0094] 58 Other semiconductor switches

[0095] 60 Other signal contacts

[0096] 62. Another first resistor

[0097] 64. Another second resistor

[0098] 66. Another second diode

[0099] 68. The other fourth resistor

[0100] 70. Another first diode

[0101] 72. An additional third resistor

[0102] 74 Other Zener diodes

[0103] 76 Fourth Resistor

Claims

1. A switching unit (14), the switching unit having: a load terminal (12) and a zero potential terminal (16), a switching element (20) connected between the load terminal and the zero potential terminal; a semiconductor switch (24), the semiconductor switch having two terminals (26) and a control input terminal (38), wherein, One terminal (26) is directed to the zero potential terminal (16), and another terminal is directed to the signal contact (28), wherein the control input terminal (38) is directed to the load terminal (12).

2. The switching unit (14) according to claim 1. Its features are, The signal contact (28) is directed to the first resistor (30).

3. The switching unit (14) according to claim 2. Its features are, The first resistor (30) is directed to the power supply terminal (32).

4. The switching unit (14) according to claim 2. Its features are, The first resistor (30) is led to the load terminal (12) via the second resistor (48).

5. The switching unit (14) according to claim 4. Its features are, The second resistor (48) is guided to the zero potential terminal (16) via a Zener diode (49).

6. The switching unit (14) according to any one of claims 2 to 5. Its features are, The first resistor (30) is directed to the third resistor (46), which is directed to the load terminal (12) via the first diode (44) and to the control input terminal (38) via the fourth resistor (42) and the second diode (40).

7. The switching unit (14) according to claim 6. Its features A second switching element (50) is connected between the zero potential terminal (16) and the second load terminal (52), wherein the third resistor (46) is guided to the second load terminal (52) via a third diode (54).

8. The switching unit (14) according to any one of claims 1 to 7. Its features are, The switching element (20) is connected by means of a fourth resistor (76).

9. The switching unit (14) according to any one of claims 1 to 8. Its features are, The signal contact (28) is connected to the LED (56) and / or directed to the control unit (20).

10. A current loop (2), the current loop comprising: a load (4), a voltage source (6) having two current terminals (8), and a switching unit (14) according to any one of claims 1 to 9, wherein, One current terminal (8) is electrically connected to zero potential (10), and another current terminal (8) is directed to the load (4), which is directed to the load terminal (12), wherein the zero potential terminal (16) is electrically connected to zero potential (10).

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