Electronic fuse for preventing an undesired permanent disconnection of electrical loads in the event of overload behaviour

Abstract

The invention relates to an electronic fuse (1) comprising a controllable switching device (5), a measuring device (6) for detecting a measurement signal, and a control and evaluation device (8) having trigger information (A) stored therein and defining a switching threshold value of the switching device. The control and evaluation device is designed to compare the measurement signal with the trigger information and to switch the switching device into a non-conductive state at least twice in the event of a comparison result resulting from the comparison, in which the measurement signal is greater than the switching threshold value, and to switch it back into a conductive state after a predetermined first time period has elapsed. The fuse comprises an event counter (9) for counting each comparison event, in which the measurement signal is greater than the switching threshold value, as an event. The control and evaluation device is designed to switch the switching device into the non-conducting state without subsequently switching the switching device into the conducting state again if a predetermined number (X) of events has been counted.

Description

[0001] Electronic fuse to prevent unwanted permanent shutdown of electrical consumers in case of overload behavior

[0002] The present invention relates to an electronic fuse for preventing an undesired permanent shutdown of electrical consumers in the event of overload behavior and to a method for operating a corresponding electronic fuse in an electrical circuit, wherein the electronic fuse is electrically connected on the input side to a power supply and on the output side to at least one electrical consumer and comprises a controllable switching device for switching off the at least one electrical consumer.

[0003] An electrical supply unit is often connected to various consumer branches, each with different electrical loads connected to it. These electrical loads can each have different power requirements. As is well known, overcurrent protection devices such as circuit breakers or electronic fuses with predetermined tripping characteristics are usually used. In the event of a fault, particularly a detected short circuit or a detected overcurrent with associated overload, these devices ensure that the respective electrical load affected by the fault is disconnected from the circuit, thus preventing any danger to people, the environment, and / or machinery.

[0004] Typically, the electronic fuse is triggered, i.e. the supply path, usually the current flow, to a consumer electrically connected to the electronic fuse is interrupted or separated, when at least one physical quantity within the circuit to be monitored by measurement exceeds a predetermined reference value or limit value.

[0005] Typically, this physical quantity is, for example, the current flowing through the electronic fuse or the voltage applied to the electronic fuse. However, a physical quantity related to the current or voltage, such as the power supplied, can also be used as the physical quantity to be monitored. The reference value or limit value can, for example, be specified as an adjustable, constant value or determined using a predetermined, adjustable tripping characteristic, also known as the tripping curve or shutdown curve. The setting of the respective tripping characteristic can, for example, be carried out by means of a control device electrically connected to the electronic fuse, e.g.a programmable logic controller (PLC), or manually on the electronic fuse itself or stored in the electronic fuse in the form of internal control logic.

[0006] When an electronic fuse is triggered, the electronic fuse is usually reset to its normal operating state, i.e., to the conductive state, by acknowledging a fault or resetting a faulty state. Resetting is generally accomplished by pressing a switch or button on the electronic fuse, by means of a corresponding signal received via a separate reset input on the electronic fuse, or via a software command. For example, if several devices in the protected circuit are switched on and the total load exceeds the respective tripping curve of the electronic fuse, the electronic fuse is triggered and disconnects the relevant consumer or load branch.In some cases, the electronic fuse can only be reset during a service call, even if the problem is only temporary, such as a motor starting up and a resulting brief overload. This leads to downtime for any electrical devices connected to the affected electronic fuse, as well as labor and associated costs.

[0007] Particularly in electrical systems that include a large number of electrical consumers connected to an electrical supply unit and a large number of electronic fuses, shutting down individual consumer branches due to transient overcurrents can be problematic. If the operation of such an electrical system is disrupted by shutting down individual consumer branches to such an extent that the entire electrical system can no longer continue operating in a reasonable manner, the electrical system must ultimately be shut down, even though the transient overcurrents may not be problematic.

[0008] The document EP 2 320 535 A1 describes, among other things, a current-limiting circuit breaker which is intended to be installed in a circuit between a feed of an input circuit breaker and at least one outgoing circuit equipped with an outgoing circuit breaker and / or contactor for limiting a current flowing through the circuit. The circuit breaker comprises switching means connected in series with the circuit, which are connected to a control unit for opening the circuit upon initial detection of a short-circuit current and for automatically closing the circuit after a preset period of time. Furthermore, the circuit breaker comprises a voltage-dependent resistance element, in particular a varistor, connected in parallel with the switching means for dissipating the energy stored in the circuit when the switching means are in the open state.In addition, the circuit breaker comprises isolating means arranged between an input line and the switching means and connected to the control unit. The control unit is designed to disconnect the circuit after a second detection of the short circuit. Thus, EP 2 320 535 A1 provides for automatic switching on or closing of the circuit after a predetermined period of time following an initial detection of a short-circuit current and a subsequent opening of the circuit. The predetermined period of time is generally based on the time required to isolate the short circuit or an output affected by the short circuit using a partial circuit breaker. If the short circuit can be successfully isolated, operation can continue without major restrictions.However, if the short circuit cannot be isolated and the short-circuit current is therefore detected a second time, the circuit is shut down or disconnected again by opening the isolating means. However, EP 2 320 535 A1 does not provide for a further automatic switching on or closing of the circuit. Instead, the short circuit is rectified and the circuit breaker is then activated by appropriate steps.

[0009] The document EP 2 785 626 B1 relates to a method for resetting a safety brake of a traveling body of an elevator system that has been released for braking, and to a safety device in an elevator system. The safety device is controlled by control devices that can trigger the safety device based on critical or non-critical events. The control devices have a function for automatically resetting the safety brake if an event assessed as non-critical is specified as the reason for triggering the safety brake. The safety brake is reset by executing predefined reset steps of the traveling body. Automatically switching on an electrical circuit twice after a critical event occurs is not mentioned.

[0010] At least one object of the present invention is to provide an improved electronic fuse compared to the prior art, in particular EP 2 320 535 A1, with which premature, unintentional and in particular permanent shutdown of an electrical load or load branch affected by an overcurrent can be avoided, but without endangering safety. A further object of the invention can be seen in providing an improved electronic fuse that can be automatically switched on again after a brief overcurrent or a brief load peak without external intervention, and in particular several times in succession. Furthermore, it is a particular object of the invention to provide an improved electronic fuse by means of which the charging of large capacities is possible.Whether a large capacitance is present depends on several parameters, in particular the respective maximum current of a power supply connected to the electronic fuse and a respective series resistor, and therefore cannot be defined generally, but only individually for a particular circuit. At least one of the stated objects is achieved by an object having the features of the independent claims. Advantageous embodiments and further developments are the subject of the further features of the subclaims.

[0011] Accordingly, at least one solution according to the invention relates to an electronic fuse comprising an input terminal designed for electrical connection to a power supply, an output terminal designed for electrical connection to an electrical consumer, an electrical line running between the input terminal and the output terminal, and a controllable switching device arranged in the electrical line.The electronic fuse further comprises a measuring device configured to detect a measurement signal representing a current flowing through the electronic fuse and / or a voltage applied to the electronic fuse's input side. It also includes a control and evaluation device electrically connected to the measuring device and the switching device, in which trigger information defining a switching threshold value of the switching device is stored. The control and evaluation device is configured to compare the measurement signal detected by the measuring device with the trigger information.In addition, the control and evaluation device is configured to switch the switching device to a non-conductive state at least twice in the event of a comparison result resulting from the comparison in which the measurement signal is greater than the switching threshold value, and to subsequently switch the switching device back to a conductive state after a predetermined first period of time has elapsed. The electronic fuse further comprises an event counter electrically connected to the control and evaluation device, which is configured to count each comparison result in which the measurement signal is greater than the switching threshold value as an event.The control and evaluation device is further configured to switch the switching device into the non-conductive state without subsequently switching the switching device back into the conductive state when a predetermined number of events have been counted by means of the event counter. The electronic fuse described above enables repeated automatic switching on in the form of switching the switching device into the conductive state or closing the circuit after the circuit has been interrupted due to a previously detected measurement signal which is greater than the switching threshold value and has thus occupied a range which is impermissible for the operation of the electronic fuse, namely by switching the switching device into a non-conductive state. Such a measurement signal, which is greater in magnitude than the switching threshold value, is detected within the electronic fuse in particular as a fault orOverload is interpreted and can, for example, represent an overcurrent, an overvoltage or a physical quantity that can be derived from a current signal and / or a voltage signal, such as a power that exceeds a power limit value designed as a switching threshold. According to the electronic fuse described above, premature and unwanted permanent disconnection of the circuit can therefore advantageously be avoided by the electronic fuse carrying out a limited number of switching-on attempts. This is particularly advantageous in the case of short-term overcurrents or load peaks, such as those that can occur when a motor starts up or when a machine is switched on or started up, which then drop again after a short time to a current value that is below the corresponding switching threshold, i.e. within the permissible range for the operation of the electronic fuse.Instead of switching off after the first detection of an overcurrent, the electronic fuse determines during one of its switch-on attempts that there is no longer an overcurrent and that the current value is within the permissible range. Accordingly, the electronic fuse then remains switched on, and the switching device remains in a conductive state after the switch-on attempt. Permanent disconnection of the circuit, however, only occurs when a predetermined number of switch-on attempts have been made by the electronic fuse, all of which were unsuccessful, i.e., the measurement signal recorded during each switch-on attempt was greater, in absolute terms, than the corresponding switching threshold value and thus outside the permissible range.The predetermined plurality is preferably adjustable so that it can be adapted to the respective circumstances, in particular to the electrical consumer connected to the electronic fuse.

[0012] Within the scope of the invention, a permanent disconnection of the circuit means that the electronic fuse can no longer be switched on automatically after the current flow has been interrupted by switching the switching device to the non-conductive state. Instead, the electronic fuse must first be reset. Such a reset of the electronic fuse can only be achieved by external intervention, for example, by actuating a switch or button on the electronic fuse, by means of a corresponding signal received via a separate reset input of the electronic fuse, or even via a software command.

[0013] A permanent separation of the circuit, and thus a triggering of the switching device or a switching of the switching device into the non-conductive state without the switching device then being switched back into the conductive state, is brought about by the electronic fuse when a predetermined number of comparison results have been determined in which the recorded measurement signal is in each case greater than the switching threshold. Accordingly, a maximum number of switch-on attempts can be specified which are to be carried out before a permanent separation of the circuit occurs. This maximum number of switch-on attempts to be carried out is always derived directly from the predetermined number of maximum events of the respective comparison results to be counted by the event counter, in each of which the measurement signal is in each case greater than the switching threshold. By specifying this predetermined number of events orThe repeated attempts to switch on the electronic fuse prevent the electronic fuse from being in a type of continuous loop in the event of an actual fault and associated measurement signals that are permanently greater than the switching threshold and thus outside the permissible range for operating the electronic fuse. A continuous loop, in which the steps of switching the switching device to the non-conductive state when a measurement signal is detected that is greater than the switching threshold, and of switching the switching device to conductive after the initial time period has elapsed, are repeated again and again, has the disadvantage that these steps cannot be interrupted or ended by the electronic fuse itself, but only by external intervention.Depending on when this external intervention occurs, this may lead to longer downtimes of the electronic fuse and the electrical consumers connected to it and to associated technical problems in connection with the electrical consumers connected to the electronic fuse.

[0014] Preventing, and in particular interrupting, such a continuous loop is achieved according to the invention in that the electronic fuse comprises an event counter. This event counter is configured to count each individual comparison result in which the detected measurement signal is greater than the switching threshold and is thus in a range that is not permitted for the operation of the electronic fuse as an event. The control and evaluation device can, for example, be configured to activate the event counter following the first switching of the switching device to the non-conductive state due to a first comparison result in which the detected measurement signal is greater than the switching threshold. In this case, the event counter counts the second comparison result in absolute terms, in which the detected measurement signal is greater than the switching threshold, as its first counted event.Alternatively, the event counter can also be activated immediately when the electronic fuse is switched on, so that it counts the absolute first comparison result in which the recorded measurement signal is greater than the switching threshold as its first event.

[0015] For example, the event counter can be set to the predetermined plurality of events. In this case, the event counter can be designed, for example, to decrease or reduce this predetermined plurality by the value 1 after each individual event detected until the event counter has expired, i.e. until the event counter has counted down to the value zero. Alternatively, the event counter can be designed, for example, to count up each individual event by the value 1, starting from the number zero, until a number of events corresponding to the predetermined plurality is reached. In both cases, the event counter can further be designed, in particular, to send a signal to the control and evaluation device as soon as it has counted a number of events corresponding to the predetermined plurality. I.e.The event counter can send a corresponding signal to the control and evaluation device when the event counter has expired, either by counting down to zero or by counting up to the predetermined number of events. The control and evaluation device, which is designed to receive signals from the event counter, then permanently deactivates the electronic fuse upon receipt of such a predetermined signal. To do this, it switches the switching device to the non-conductive state, as already described, without subsequently switching the switching device back to the conductive state.

[0016] The switching device of the electronic fuse can be designed in various ways. For example, the switching device can comprise at least one controllable semiconductor switch. Alternatively, the switching device can comprise at least one electromechanical switch, e.g., a relay. To enable interruption of the current flow or switching off of the electronic fuse even in the event of a large difference between the switching threshold value and the measurement signal, e.g., in the event of large overcurrents or overvoltages, the switching device can comprise, for example, a field-effect transistor (FET). A respective switching threshold value S is to be understood in particular as a value with corresponding tolerance limits. The control and evaluation device is designed to control the switching device. For example, the control and evaluation device can be designed as a microcontroller or comprise a microcontroller.The measuring device can, for example, comprise a current measuring path or a voltage measuring path. In a further development of the electronic fuse described above, the control and evaluation device can further be configured to reset the event counter to the value zero if a number of events that is less than the predetermined plurality has been counted by means of the event counter and, after the expiration of a predetermined second time period since the switching device was previously switched to the conductive state, no further events have been counted. In addition, it can be provided, in particular, that the predetermined second time period is at least as long as the predetermined first time period that has elapsed until the switching device was previously switched to the conductive state.The event counter can therefore always be reset to the value zero if the control and evaluation device does not detect any event or no further event of a comparison result for which the detected measurement signal is greater than the switching threshold value within the second time period, whereby the second time period begins to run when the switching device is switched on, i.e. when the switching device is switched to the conductive state. The electronic fuse therefore remains in an switched state in this case. In order to reset the event counter, the control and evaluation device can in particular send a corresponding signal, e.g. a reset signal, to the event counter. The second time period can, for example, be specified or set in advance depending on the application.

[0017] According to a further development, it can be provided that the respectively predetermined first time period depends on the respectively immediately preceding comparison result in which the measurement signal is greater than the switching threshold, in particular the magnitude of the difference between the measurement signal and the switching threshold resulting from the comparison result. A respective switching of the switching device to the conductive state after a previous switching of the switching device to the non-conductive state or a triggering of the switching device can thus be adapted to the respective prevailing circumstances. The respectively predetermined first time period can optionally have a functional relationship to the magnitude of the exceedance of the switching threshold. Furthermore, the respectively predetermined first time period can in particular be stored in the control and evaluation device.For example, the respective predetermined first time period can be stored in the control and evaluation device as a function that depends on the magnitude of the difference between the detected measurement signal and the switching threshold, or, for example, in the form of a table in which a range of a magnitude of the difference between the detected measurement signal and the switching threshold is assigned to a respective predetermined first time period. Alternatively, the respective predetermined first time period can also be preset, for example, from outside the electronic fuse, e.g., manually adjustable on the electronic fuse or preset or predefined by a control device connected to the electronic fuse, such as a programmable logic controller (PLC).

[0018] As an alternative to the aforementioned further development of the invention, the respective predetermined first time period can also be set to a fixed value, i.e., a value that is independent of the magnitude of the difference between the detected measurement signal and the switching threshold. This fixed value of the first time period can, for example, be stored in the control and evaluation device or, alternatively, can be specified from outside the electronic fuse, e.g., manually adjustable on the electronic fuse or can be specified or preset by a control device connected to the electronic fuse, e.g., a PLC.

[0019] In combination with this, or alternatively, it can be provided that the triggering information comprises at least one triggering characteristic, in particular a current characteristic, or at least one limit value, in particular a voltage limit value and / or a current limit value, and / or that the triggering information is predeterminable, in particular adjustable. In particular, the triggering information can be dependent on the electrical load to be connected or connected to the electronic fuse.

[0020] At least one of the above-described objects of the present invention is further achieved by a method for operating an electronic fuse in an electrical circuit in a predetermined operating mode, wherein the electronic fuse is electrically connected on the input side to a power supply and on the output side to at least one electrical load, and comprises a switching device arranged in series with the electrical circuit. The method comprises the steps:

[0021] - detecting a measuring signal representing a current flowing through the electronic fuse and / or a voltage applied to the electronic fuse by means of a measuring device included in the electronic fuse,

[0022] - comparing the recorded measurement signal with triggering information stored in the electronic fuse, which defines a switching threshold value of the switching device,

[0023] - performing at least twice the steps of switching the switching device into a non-conductive state in the case of a comparison result resulting from the comparison in which the measurement signal is greater than the switching threshold value, and subsequently switching the switching device into a conductive state after expiry of a respective predetermined first time period,

[0024] - counting each comparison result where the measurement signal is greater than the switching threshold as an event using an event counter included in the electronic fuse, and

[0025] - Switching the switching device to the non-conductive state without subsequently switching the switching device back to the conductive state when the event counter has counted a predetermined number of events.

[0026] The method relates in particular to a method for operating an electronic fuse according to one of the previously described embodiments. The operation of the electronic fuse in a predetermined operating mode results from the aforementioned steps of switching the switching device into a non-conductive state at least twice in the case of a comparison result in which the measurement signal is greater than the switching threshold value, counting such comparison results in which the measurement signal is respectively greater than the switching threshold value as a respective event, and a so-called final or last switching of the switching device into the non-conductive state without subsequently switching the switching device on again. These steps defining the predetermined operating mode can in particular comprise a modified so-calledDescribe hiccup mode, which will be explained in more detail with reference to Figure 1.

[0027] According to a further development of the method according to the invention, this may further comprise resetting the event counter to the value zero if the event counter has counted a number of events which is less than the predetermined plurality and the event counter has not counted any further events after the expiration of a predetermined second time period since the previous switching of the switching device into the conductive state.

[0028] Within the scope of the method according to the invention, it can also be provided in particular that the event counter is activated by a first switching of the switching device into the non-conductive state as a result of a first comparison result in which the measurement signal is greater than the switching threshold value, and the predetermined plurality of events to be counted is specified to the event counter.

[0029] Furthermore, in combination or as an alternative to the aforementioned embodiments of the method according to the invention, it can be provided that the electronic fuse is reset as a result of the switching device being switched to the non-conductive state after a number of counted events corresponding to the predetermined plurality, in particular by means of a manually operable switch arranged on the electronic fuse, by means of a signal received via a reset input of the electronic fuse, or by means of a software instruction within the electronic fuse. This makes it possible for the electronic fuse to be reset to an operational state after a permanent shutdown as a result of a number of counted events corresponding to the predetermined plurality.Advantageously, this only occurs after the cause of the recurring comparison result—that the measurement signal is greater than the threshold value and thus outside the permissible range—has been eliminated. Further advantages, features, and possible applications of the present invention will become clear from the following description of embodiments thereof and the accompanying figures. They show:

[0030] Figure 1: a sketch of an electronic fuse arranged in a circuit according to an embodiment of the invention,

[0031] Figure 2: a time course of a complete switch-off sequence of the switching device of an electronic fuse according to an embodiment of the invention, and

[0032] Figure 3: a schematic diagram of an alternative embodiment compared to the internal structure of the electronic fuse according to Fig. 1.

[0033] Figure 1 shows a sketch of an electronic fuse 1 arranged in an electrical circuit according to an embodiment of the invention. The electronic fuse 1 shown has an input terminal IN, which is designed for electrical connection to a power supply 2, and an output terminal OUT, which is designed for electrical connection to an electrical consumer 3 or an electrical load. The power supply 2 is in particular a power supply or a voltage supply. The electrical consumer 3 is thus protected by the electronic fuse 1 and can, for example, be a technical system or a component, e.g. a machine, of a technical system. The electronic fuse 1 comprises a controllable switching device 5, which, according to Figure 1, is arranged in an electrical line 4 that runs between the input terminal IN and the output terminal OUT.In addition, the electronic fuse 1 outlined in Figure 1 comprises a measuring device 6, also arranged in the electrical line 4, which is designed to detect a measurement signal representing a current flowing through the electronic fuse 1 and / or a voltage applied to the input side of the electronic fuse 1. For example, the measurement signal can be a current signal, a voltage signal, or a power signal.

[0034] Furthermore, the electronic fuse 1 comprises a control and evaluation device 8 which is electrically connected to the measuring device 6 and the switching device 5 and which is designed as a microcontroller in the exemplary embodiment in Figure 1. Tripping information A defining a switching threshold value of the switching device 5 is stored in the control and evaluation device 8, in particular in a memory device 10 according to Figure 1 included in the control and evaluation device 8. The tripping information A stored in the electronic fuse 1 can, for example, comprise at least one tripping characteristic curve, in particular a current characteristic curve, or at least one limit value, in particular a voltage limit value and / or a current limit value. Additionally or alternatively, the tripping information A can be predefined, in particular adjustable. Furthermore, the tripping information A can comprise tripping times which are dependent on a respective detected measurement signal.

[0035] The control and evaluation device 8 of the electronic fuse 1 is configured to compare a measurement signal detected by the measuring device 6 with the stored triggering information A, in particular with the switching threshold defined by the triggering information A. Furthermore, the control and evaluation device 8 is configured to switch the switching device 5 at least twice to a non-conductive state in the event of a comparison result resulting from the comparison in which the measurement signal is greater than the switching threshold, specifically greater in magnitude, and thus to trigger it, and to subsequently switch the switching device 5 back to a conductive state after a respective predetermined first time period has elapsed.To control the switching device 5, the electronic fuse 1 can optionally have a control circuit that is electrically connected to the control and evaluation device 8 and the switching device 5 and, in particular, is connected between the control and evaluation device 8 and the switching device 5. For the sake of clarity, the control circuit is not shown in Figure 1. Such a control 11 is shown, for example, in the embodiment according to Figure 3, which is an alternative to the internal structure of the electronic fuse according to Figure 1.

[0036] The switching device 5 according to Figure 1 is embodied, for example, as a metal-oxide-semiconductor field-effect transistor (MOSFET), with a current measurement integrated into a MOSFET chip. In an alternative embodiment, the switching device can, for example, comprise an electromechanical switch, e.g., a relay, as a disconnector, or can be embodied, for example, as a contactless thermal switching device, a so-called BTS.

[0037] The measuring device 6 sketched in Fig. 1, which can preferably measure both currents and voltages, is divided into two measuring devices 6a and 6b in the embodiment shown in Fig. 3. The voltage measurement 6a is performed, for example, via a voltage divider. The current measurement is performed, for example, in a switching device 5 designed as a MOSFET, using an additional circuit 6b or can be constructed discretely.

[0038] For example, the measuring device 6a for measuring the voltage of the electronic fuse 1 can have a voltage divider and two voltage measuring paths (not shown for reasons of clarity), which are used to detect which voltage is applied to the electronic fuse 1, i.e. which voltage is applied in particular on the input side, and depending on a further alternative embodiment, possibly also on the output side of the electronic fuse 1. Based on these detected voltage values, the electronic fuse 1 can accordingly also receive important information about the type of load. Based on the tripping information A, in particular e.g. a tripping characteristic curve, the electronic fuse 1 can then switch off the path, i.e. switch the switching device 5 to the non-conductive state.As previously described, the tripping characteristic is in particular a current characteristic, so that the tripping behavior depends significantly on the current value, which is detected via the additional circuit 6b according to the embodiment shown in Fig. 3. As can be seen from Figure 1, the electronic fuse 1 further comprises an event counter 9 electrically connected to the control and evaluation device 8. According to the exemplary embodiment shown in Figure 1, the control and evaluation device 8 also has the event counter 9, although in a further embodiment the event counter 9 can also be designed, for example, as a separate component of the electronic fuse 1 that is electrically connected to the control and evaluation device 8. This is designed to count each comparison result determined during the comparison, in which the measurement signal is greater, specifically greater in terms of amount, than the switching threshold value, as an event.This means that the event counter 9 counts every event in which the detected measurement signal lies within an impermissible range. The impermissible range is defined by the detected measurement signal lying outside the permissible value range specified by the trigger information A. In particular, the event counter 9 can thus count every exceedance of the switching threshold as an event. An event counted by the event counter is counted as an event regardless of how long a respective comparison result, in which the measurement signal is greater in magnitude than the switching threshold, exists until the switching device switches to the non-conductive state, and thus regardless of a respective trigger time.

[0039] The control and evaluation device 8 of the electronic fuse 1 is further configured to switch the switching device 5 into a non-conductive state, i.e. to trigger the switching device 5 without subsequently switching it back into the conductive state, when a predetermined number X of events have been counted by the event counter 9 and thus, since activation of the event counter 9, a comparison result has been determined X times in which the detected measurement signal is greater in magnitude than the switching threshold value. Accordingly, a permanent disconnection of the circuit, and thus a switching off of the electronic fuse 1, is carried out. Further switching on as a result of the permanent disconnection can only occur by resetting the electronic fuse 1 by means of external intervention.For example, such a reset can be effected by means of a manually operable switch arranged on the electronic fuse 1, by means of a signal received via a reset input of the electronic fuse or by means of a software instruction within the electronic fuse.

[0040] The electronic fuse 1 shown in Figure 1 operates in a predetermined operating mode, specifically based on a modified form of so-called hiccup mode. Hiccup mode is known as a special form of overload protection for power supplies. In hiccup mode, the power supply to a power supply is briefly switched off in order to cyclically restart the power supply or cyclically switch the power on again and again to check whether the overload has been rectified. However, the cyclical start attempts are repeated until the error is eliminated or the overload is remedied. In contrast to such a continuous loop, the operation of the electronic fuse according to the invention terminates this continuous loop when a predetermined number of repeatedly recurring individual overloads have been detected.In other words, the electronic fuse according to the invention only performs a limited number of start-up or switch-on attempts, with this number being predetermined and adjustable. If this limited number of switch-on attempts is unsuccessful, i.e., the fault or overload persists, the electronic fuse automatically switches itself off. To switch the electronic fuse on again, the electronic fuse must first be reset from outside the electronic fuse.

[0041] The modified hiccup mode used in the operation of the electronic fuse as a predetermined operating mode can be summarized as follows according to an exemplary embodiment:

[0042] - Activating an event counter with a predetermined number X of maximum events to be counted, in particular after the switching device is switched into the non-conductive state for the first time, ie after the electronic fuse has been triggered due to the detection of an overload,

[0043] - after a predetermined first period of time during which the electronic fuse is switched off, carrying out a switch-on attempt and switching on the

[0044] Switching device,

[0045] - upon detection of a renewed overload, switching the switching device into the non-conductive state, i.e. triggering of the electronic fuse, and counting of a first event by the event counter, in particular incrementing the event counter,

[0046] - Repeat the last two steps until:

[0047] 1) the event counter has counted the predetermined number X of events, for example when the event counter has expired,

[0048] -> whereupon the electronic fuse is permanently switched off; or

[0049] 2) the event counter has counted a number of events that is less than the predetermined plurality X, and the event counter has not counted any further events,

[0050] -> whereupon the electronic fuse remains switched on and the event counter is reset to zero after a predetermined second period of time.

[0051] The detection of an overload corresponds to the acquisition of a measurement signal whose magnitude is greater than the respective switching threshold defined by the trigger information. As an alternative to the previously mentioned example sequence, the activation of the event counter can also coincide with the activation of the electronic fuse. In this case, the event counter counts the initial detection of an overload as an event. The predetermined maximum number of events to be counted by the event counter until a permanent shutdown of the electronic fuse occurs should therefore be set or determined depending on the time of activation of the event counter. Figure 2 shows an example of a time course of a complete

[0052] Switching-off sequence of the switching device of an electronic fuse according to an embodiment of the invention, wherein a first detected measurement signal MSI and a second detected measurement signal MS2 are sketched as a function of time. The measurement signals MSI, MS2 can in principle be present, for example, in the form of a current signal, a voltage signal, or even a power signal. In the example shown in Figure 2, the measurement signals MSI, MS2 are, for example, current signals. The measurement signals MSI, MS2 are detected by the measuring device of the electronic fuse and compared with the tripping information, which defines a predetermined corresponding switching threshold value S. The switching threshold value S is to be understood in particular as a value with corresponding tolerance limits. In Figure 2, the switching threshold value S is, for example, a current limit value that is predetermined based on a tripping characteristic curve embodied as tripping information.

[0053] If it is determined during the comparison that the respective measured signal MSI, MS2 is greater than the switching threshold S, as is the case in Figure 2, the switching device is controlled to switch to the non-conductive state in such a way that the electronic fuse is triggered after the expiry of a respective triggering time tA, tA specified by the triggering information 1is switched off. Accordingly, the respective measuring signal MSI, MS2 drops to the value zero. After a predetermined time period TI, T1 ', which begins when the electronic fuse is switched off, the switching device is switched back to the conductive state by means of a corresponding control. In the example shown, the measuring signals MSI, MS2 are still greater than the switching threshold value S, so that the switching device is switched back to the non-conductive state, i.e. the electronic fuse is triggered, after the respective triggering time tA, tA 1, occurs. The measurement signals MSI, MS2 thus drop back to the value zero. Once again, the switching device is switched back to the conductive state after the respective predetermined time period TI, T1' has elapsed. Since the error or disturbance underlying the increased measurement signals MSI, MS2 has not been remedied in the example in Figure 2, but is permanently present in the example in Figure 2, these steps are repeated until a predetermined plurality X of events relating to a comparison result in which the respectively detected measurement signal MSI, MS2 is greater than the switching threshold value S has been counted by means of the event counter.

[0054] In the present example of Figure 2, the event counter is activated after the first detection of a comparison result in which the respective detected measurement signal MSI, MS2 is greater than the switching threshold value S. With the activation of the event counter, the previously described modified hiccup mode begins, in which an attempt is made to switch the electronic fuse on again X times before the electronic fuse switches to the permanently switched off state. Accordingly, the event counter counts the second detection of a comparison result in which the respective detected measurement signal MSI, MS2 is greater than the switching threshold value S as its first event. As can be seen from the exemplary Figure 2, the predetermined plurality X of events in Figure 2 corresponds, for example, to the number five, but can also correspond to any other integer, in particular a number greater than or at least equal to two.After the event counter in the example in Figure 2 has counted the fifth event and thus for the sixth time a comparison result is available in which the respective measurement signal MSI, MS2 is greater than the switching threshold value S, the electronic fuse switches off permanently by transferring the switching device to the non-conductive state without switching the switching device on again. Subsequently, the electronic fuse can only be switched on again by means of external intervention by resetting the electronic fuse, as already mentioned. The event counter can in particular be set up to send a signal to the control and evaluation device of the electronic fuse as soon as it has counted a number of events corresponding to the predetermined plurality.Applied to the aforementioned example, the event counter can therefore inform the control and evaluation device via signal transmission that it has counted five events corresponding to the predetermined plurality, so that the control and evaluation device then initiates permanent shutdown. In the example shown in Figure 2, the second measurement signal MS2 corresponds to 1.5 times the switching threshold value S, while the first measurement signal MSI corresponds to 1.1 times the switching threshold value S. Accordingly, the difference in magnitude between the second measurement signal MS2 and the switching threshold value S is greater than the difference in magnitude between the first measurement signal MSI and the switching threshold value S.As outlined by way of example in Figure 2, the respective predetermined first time period TI, TT depends on the respective comparison result that occurred immediately beforehand, in which the respective measurement signal MSI, MS2 is greater than the switching threshold value S, and specifically on the absolute value of the difference between the respective measurement signal MSI, MS2 and the switching threshold value S resulting from the comparison result. The predetermined time period TI, T1 ' is provided in particular for recovering and / or cooling the electronic fuse and the respective electrical load connected to it from the overload. According to Figure 2, the predetermined first time period TI is set to 5 seconds by way of example for the previously recorded measurement signal MSI. The predetermined first time period T1' for the previously recorded measurement signal MS2, in contrast, is set to 3 seconds by way of example.Furthermore, the respective tripping times tA, t\ of the electronic fuse, which are included in the respective tripping information stored in the electronic fuse, also differ. While the second measurement signal MS2 is assigned a tripping time of, for example, 2 seconds, the first measurement signal MSI is assigned a tripping time of, for example, 4 seconds. With a predetermined plurality of, for example, five events counted by means of the event counter and correspondingly five attempts to switch on the electronic fuse as a result of the event counter being triggered and activated for the first time, according to the above example, the total time duration for switching off the electronic fuse results, which is made up of six times the respective tripping time tA, FA of the electronic fuse and five times the respective predetermined first time duration TI, T1 '.This total time for switching off the electronic fuse amounts to T when the first measurement signal MSI is present. ges = 6 • 4s + 5 • 5s = 49 seconds and in the presence of the second measurement signal MS2 on T ges = 6 • 2s + 5 • 3s = 27 seconds. In general, the total time required to switch off the electronic fuse, ie the total maximum switch-off time T ges the electronic fuse in modified hiccup mode, determined by: T ges= (X + 1) • tA + X • TI, where tA denotes the respective triggering time according to the stored triggering information and TI denotes the respective predetermined first time period. However, this formula only applies if the event counter is activated after the electronic fuse is triggered for the first time. Alternatively, if the event counter is activated when the electronic fuse is switched on, so that it counts the first comparison result in which the respective measurement signal MSI, MS2 is greater than the switching threshold as an event, the following formula is: T ges = X • tA + (X-1) • TI.

[0055] As an alternative to the time course shown in Figure 2, it may also be the case that a fault that occurred in the meantime or a briefly increased measurement signal, for example, a brief overcurrent that occurred when switching on the load connected to the electronic fuse, has been rectified. Thus, the electronic fuse is not permanently switched off, since the electronic fuse has counted a number of events using the event counter that is less than the predetermined number X.The control and evaluation device of the electronic fuse is then particularly configured to reset the event counter to the value zero if, in addition to the requirement that a number of events less than the predetermined plurality X has been counted by the event counter, no further events have been counted after a predetermined second period of time has elapsed since the switching device was previously switched to the conductive state. This means that the control and evaluation device waits for a predetermined second period of time after it has switched the switching device to the conductive state and, after this second period of time has elapsed, resets the event counter to the value zero if the event counter has not counted any further events within the second period of time.The predetermined second time period can optionally be at least as long as the predetermined first time period that elapsed until the switching device was previously switched to the conductive state. Accordingly, a method for operating the electronic fuse in a predetermined operating mode, in particular in the previously described modified so-called hiccup mode, can comprise resetting the event counter to the value zero if the event counter has counted a number of events that is less than the predetermined plurality X and, after the expiration of the predetermined second time period since the switching device was previously switched to the conductive state, the event counter has not counted any further events in which the switching threshold has been exceeded.

[0056] In summary, the present invention relates to an electronic fuse and a method for operating an electronic fuse in a predetermined operating mode, in particular in the modified hiccup mode described above, wherein the electronic fuse enables multiple, but at least two, re-activation after a previously occurring fault. If the fault is present only for such a limited time that the respective detected measurement signals are no longer greater in magnitude than a respective switching threshold defined by triggering information after (Xl) attempts to re-activate at the latest, and thus only a maximum of (Xl) events have been counted, the electronic fuse remains activated. The event counter can then optionally be reset to the value zero, as explained above.On the other hand, the electronic fuse causes a permanent shutdown and thus a switching of the switching device into the non-conductive state, without then switching the switching device into the conductive state again, if the fault that has occurred is still present after (Xl) attempts to switch on, ie if the respective measured signal is still greater in magnitude than the respective.

[0057] Switching threshold value. In this case, a plurality of X events are counted by the event counter, whereupon the switching device is transferred to the non-conductive state for a final time and the electronic fuse is permanently switched off until it can be reset by external intervention. An unwanted permanent switch-off of the electronic fuse and the electrical loads connected to it, for example in the event of brief overload peaks, can thus be avoided. In contrast to the hiccup mode known from power supplies, however, the electronic fuse only carries out a limited number of switch-on attempts before it switches to permanent shutdown.

[0058] List of reference symbols

[0059] 1 electronic fuse

[0060] 2 Energy supply

[0061] 3 electrical consumers

[0062] 4 electrical cable

[0063] 5 Switching device

[0064] 6 Measuring device

[0065] 8 Control and evaluation device

[0066] 9 Event counter

[0067] 10 Storage device

[0068] 11 Control

[0069] IN input connector

[0070] OUT output connector

[0071] A trigger information

[0072] X predetermined plurality of events

[0073] T 1 , T 1 ' predetermined first time period tA, t'A tripping time

[0074] Ttotal maximum shutdown time

Claims

Patent claims 1. Electronic security device (1), comprising: - an input terminal designed for electrical connection to a power supply (2), - an output terminal designed for electrically connecting an electrical consumer (3), - an electrical line (4) running between the input terminal and the output terminal, - a controllable switching device (5) arranged in the electrical line (4), - a measuring device (6) designed to detect a measuring signal (MSI, MS2) representing a current flowing through the electronic fuse (1) and / or a voltage applied to the electronic fuse on the input side, - a control and evaluation device (8) electrically connected to the measuring device (6) and the switching device (5), in which a trigger information (A) defining a switching threshold value (S) of the switching device (5) is stored, wherein the control and evaluation device (8) is designed to - to compare the measurement signal (MSI, MS2) detected by the measuring device (6) with the trigger information (A), and - to switch the switching device (5) at least twice in the event of a comparison result resulting from the comparison in which the measurement signal (MSI, MS2) is greater than the switching threshold value (S), and to subsequently switch the switching device (5) back to a conducting state after a predetermined first time period (TI, T1') has elapsed, wherein the electronic fuse (1) further comprises an event counter (9) electrically connected to the control and evaluation device (8) and designed to count each comparison result in which the measurement signal (MSI, MS2) is greater than the switching threshold value (S) as an event, and the control and evaluation device (8) is further configured to switch the switching device (5) into the non-conductive state without subsequently switching the switching device (5) back into the conductive state when a predetermined plurality (X) of events has been counted by means of the event counter (9).

2. Electronic fuse (1) according to claim 1, wherein the control and evaluation device (8) is further configured to reset the event counter (9) to the value zero if a number of events which is less than the predetermined plurality (X) has been counted by means of the event counter (9) and after the expiration of a predetermined second time period since the previous switching of the switching device (5) into the conductive state, no further event has been counted.

3. Electronic fuse (1) according to claim 2, wherein the predetermined second time period is at least as long as the predetermined first time period (TI, TI ') which has elapsed until the previous switching of the switching device (5) into the conductive state.

4. Electronic fuse (1) according to one of claims 1 to 3, wherein the respective predetermined first time period (TI, T1 ') is dependent on the respective immediately previously occurring comparison result in which the measurement signal (MSI, MS2) is greater than the switching threshold value (S), in particular the magnitude of the difference resulting from the comparison result between the measurement signal (MSI, MS2) and the switching threshold value (S).

5. Electronic fuse (1) according to one of claims 1 to 4, wherein the triggering information (A) comprises at least one triggering characteristic, in particular a current characteristic, or at least one limit value, in particular a voltage limit value and / or a current limit value, and / or the triggering information (A) is predeterminable, in particular adjustable.

6. Electronic fuse (1) according to one of claims 1 to 5, wherein the event counter (9) is further designed to send a signal to the control and evaluation device (8) as soon as it has counted a number of events corresponding to the predetermined plurality (X).

7. A method for operating an electronic fuse (1) in an electrical circuit in a predetermined operating mode, wherein the electronic fuse (1) is electrically connected on the input side to a power supply (2) and on the output side to at least one electrical consumer (3) and comprises a switching device (5) arranged in series with the electrical circuit, comprising the steps: - detecting a measuring signal (MSI, MS2) representing a current flowing through the electronic fuse (1) and / or a voltage applied to the electronic fuse (1) by means of a measuring device (6) included in the electronic fuse (1), - comparing the measuring signal (MSI, MS2) with a triggering information (A) stored in the electronic fuse (1), which defines a switching threshold value (S) of the switching device (5), - at least twice carrying out the steps of each switching the switching device (5) into the non-conductive state in the case of a comparison result resulting from the comparison in which the measurement signal (MS1, MS2) is greater than the switching threshold value (S), and then switching the switching device (5) into a conductive state after expiry of a respective predetermined first time period (TI, T1 '), - counting each comparison result in which the measurement signal (MSI, MS2) is greater than the switching threshold value (S) as an event by means of an event counter (9) included in the electronic fuse (1), and - Switching the switching device (5) into the non-conductive state without subsequently switching the switching device (5) into the conductive state again when the event counter (9) has counted a predetermined plurality (X) of events.

8. The method according to claim 7, further comprising resetting the event counter (9) to the value zero when the event counter (9) has a number of events which are smaller than the predetermined plurality (X) and the event counter (9) has not counted any further events after the expiry of a predetermined second period of time since the previous switching of the switching device (5) into the conductive state.

9. The method according to claim 7 or 8, wherein the event counter (9) is activated by a first switching of the switching device (5) into the non-conductive state as a result of a first comparison result in which the measurement signal (MSI, MS2) is greater than the switching threshold value (S), and the predetermined plurality (X) of events to be counted is specified to the event counter (9).

10. The method according to one of claims 7 to 9, wherein the electronic fuse (1) is reset as a result of the switching of the switching device (5) into the non-conductive state after a number of counted events corresponding to the predetermined plurality (X), in particular by means of a manually operable switch arranged on the electronic fuse (1), by means of a signal received via a reset input of the electronic fuse (1) or by means of a software instruction within the electronic fuse (1).

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