Electronic safety device with integrated power monitoring and protection switching function, power monitoring system and method for operating the electronic safety device

Abstract

The invention relates to an electronic safety device (1), to a power monitoring system comprising the safety device, and to a method for operating the safety device. The safety device comprises an input connection (IN) for connecting to a DC voltage network (2), an output connection (OUT) for connecting a DC voltage load (3), a control input (4), a controllable switching device (6), a current measuring device (7) and a voltage measuring device (8) for detecting a current flowing through the safety device and a voltage applied to the safety device, and a control and evaluation device (9) electrically connected to the current measuring device, voltage measuring device and control input, which is configured to calculate a power on the basis of detected current and voltage measured values and to compare this with a reference value defining a power limit value and to switch the switching device to a non-conducting state if the calculated power is greater than the power limit value. The safety device is designed to receive, via its control input, a frequency signal that has a predetermined functional relationship to the reference value and by means of which the reference value can be set.

Description

[0001] Electronic fuse with integrated power monitoring and protective switching function, power monitoring system and method for operating the electronic fuse

[0002] The present invention relates to an electronic fuse with integrated power monitoring and a protective switching function, a power monitoring system comprising the electronic fuse, and a method for operating the electronic fuse. The electronic fuse is electrically connected to a DC voltage network on the input side and to a DC voltage load on the output side, and comprises a controllable switching device for switching off the DC voltage load.

[0003] An electrical supply unit, such as a DC voltage network, is often connected to various consumer branches, each with its own electrical load. 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, an electronic fuse is triggered, i.e. the supply path, usually the current flow, to an electrical consumer electrically connected to the electronic fuse, e.g. a DC load, is interrupted or separated, when at least one physical quantity within the circuit that is to be monitored exceeds a predetermined reference value or limit value. This physical quantity is usually, 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 orThe limit value can, for example, be specified as an adjustable, constant value or can be determined using a predefined tripping characteristic, also known as the tripping curve or shutdown curve. The setting or specification of the respective tripping characteristic is generally carried out by the user of the electrical load to be connected to the electronic fuse, manually on the electronic fuse itself, for example using a potentiometer or a so-called “dual in-line package” (DIP) switch. Furthermore, the setting or specification of the tripping characteristic can also be carried out using a control device electrically connected to the electronic fuse, e.g. a programmable logic controller (PLC), or can be stored in the electronic fuse in the form of internal control logic.

[0005] If the electronic fuse trips and interrupts the circuit, the electronic fuse must typically be returned to its normal operating state, i.e., the conductive state, by acknowledging a fault or resetting a faulty condition. This can be done, for example, by operating a switch or button on the electronic fuse, by using a corresponding signal received via a separate reset input on the electronic fuse, or via a software command.

[0006] With some electrical consumers, e.g. motors, an initially briefly increased inrush current which exceeds the predetermined reference value can occur, particularly when switched on. However, the triggering of an electronic fuse connected to such an electrical consumer, and thus the disconnection of the electrical consumer from the power supply, is not desired in this case. Furthermore, even during ongoing operation of an electrical consumer, the requirements for the power supply to be made available to the electrical consumer can change over time. For example, an increased current flow must be made available to the electrical consumer for a limited time, or the direction of energy flow must be changed, e.g. in an elevator system. If an initially adjustable orIf a predefined triggering characteristic is stored in the electronic fuse, the electronic fuse will trigger based on this triggering characteristic. However, this can also lead to an undesired triggering of the electronic fuse, particularly as a result of a brief overload current, for example, during the previously described switching on of an electrical load connected to the electronic fuse, or as a result of an overload current due to temporally changing energy supply requirements of a respective electrical load connected to the electronic fuse.

[0007] European patent EP 3 949 053 B1 discloses an overcurrent protection device for protecting a load arranged in a direct current network, which is coupled in the direct current network via the overcurrent protection device to a supply rail that can be connected or is connected to a supply potential of the direct current network. The overcurrent protection device is designed to determine a current tripping value based on a detection value of a current flowing through the overcurrent protection device and a current-dependent tripping characteristic curve assigned to the load, to compare this current with a predetermined threshold value, and to trigger the overcurrent protection device or not depending on the result of the comparison. Depending on the current direction, the current is taken into account in the tripping characteristic curve with a first or a second factor. The predetermined threshold value is, for example,determined by tests or numerical determination or chosen so that it is a predetermined percentage above an action value.

[0008] Against the above background, it is an object of the present invention to provide an electronic fuse which enables a flexible adaptation of the switching threshold value or reference value to a DC voltage load electrically connected to the electronic fuse, in particular a dynamic adaptation of the reference value to a time-changing energy requirement of the DC voltage load, and nevertheless ensures a reliable separation of the DC voltage load from the energy supply in the event of a fault-related overload.

[0009] This object is achieved by an object having the features of the independent claims. Advantageous embodiments and

[0010] Further developments are the subject of the further features of the subclaims.

[0011] Accordingly, the solution according to the invention relates to an electronic fuse for protecting a DC load arranged in a DC voltage network, comprising an input terminal designed for electrical connection to a DC voltage network, an output terminal designed for electrical connection of a DC load, a control input, a controllable switching device arranged between the input terminal and the output terminal, a current measuring device designed for detecting a current flowing through the electronic fuse, and a voltage measuring device designed for detecting a voltage applied to the electronic fuse, as well as a control and evaluation device.The control and evaluation device is electrically connected to the current measuring device, the voltage measuring device and the control input and is designed to calculate a power based on a current detected by the current measuring device and a voltage detected by the voltage measuring device and to compare the calculated power with a reference value that defines a power limit, in particular continuously or at predetermined time intervals. Furthermore, the control and evaluation device is designed to cause the switching device to disconnect a connected DC voltage load from the DC voltage network in the event of a calculated power that is greater than the power limit, i.e. to switch the switching device to a non-conductive state. The electronic fuse is characterized, among other things, byin that it is designed to receive, via its control input, a frequency signal which has a predetermined functional relationship to the reference value and by means of which the reference value can be set. The electronic fuse according to the invention advantageously enables the reference value or switching threshold value of the electronic fuse to be set and thus to be adapted flexibly, in particular dynamically, to a time-changing energy requirement of a DC voltage load connected to the electronic fuse and to be supplied with energy. Thus, it is possible, among other things, even during operation of the electronic fuse and a DC voltage load connected to it, to dynamically adapt the reference value to the current conditions, in particular the respective time-dependent energy requirement or current requirement of the respective electrically connected DC voltage load.This is achieved by the electronic fuse being able to receive a frequency signal via its control input, which has a predetermined functional relationship to the reference value defining the power limit. The received frequency signal is processed in the electronic fuse, in particular in its control and evaluation device. As part of this processing, the control and evaluation device can set the reference value using the frequency signal based on an assignment rule defining the predetermined functional relationship and determine the power limit. Such an assignment rule assigns a corresponding reference value to the received frequency signal, in particular depending on one or more parameters, such as the frequency or the pulse width, of the frequency signal, using predefined differentiation criteria.

[0012] The reference value assigned to the received frequency signal defines a power limit that acts as the switching threshold of the electronic fuse. The reference value can optionally also correspond to the power limit, but the reference value does not necessarily have to be a power limit. It can also be, for example, a current limit that is set using the received frequency signal and from which the power limit can be directly derived.

[0013] Based on the recorded current and voltage measurements, the control and evaluation device calculates a corresponding power value, which is compared with the set reference value or the power limit defined thereby. If the control and evaluation device determines that the calculated power value is greater, specifically greater in magnitude, than the power limit, it disconnects the connected DC load from the DC network by appropriately controlling the switching device. This means that it switches the switching device to a non-conductive state. The DC load is then disconnected or switched off from the DC network's power supply.However, if the control and evaluation device determines during the comparison that the calculated power value is not greater, and indeed not greater in magnitude, than the power limit, it does not disconnect the connected DC load from the DC network. Proper operation of the electronic fuse and the connected DC load is therefore maintained. The control and evaluation device waits for the subsequently acquired current and voltage measurements to recalculate a current power value and compare it with the same power limit or with a newly set power limit using a current frequency signal received via the control input.

[0014] In particular, it can be provided that a reference value is already initially specified or preset in the electronic fuse, or that a reference value is prestored in the electronic fuse, e.g., in the form of a triggering characteristic. In this case, the initially specified reference value or the triggering characteristic is included as corresponding information in the predetermined functional relationship and is thus taken into account when setting the reference value using a received frequency signal. Accordingly, the reference value set using the received frequency signal can be, in particular, larger, but also smaller, than an initially specified reference value.

[0015] The power calculation performed by the electronic fuse has the advantage, among other things, that it determines the actual power supplied to a connected DC load, thus eliminating any supply line losses along the DC supply rail on the input side of the electronic fuse. In the optional case where current value monitoring is desired using the electronic fuse, the power limit defined by the reference value can, for example, be converted back to a current limit, or a reference value can be used that corresponds to a current limit. Furthermore, the calculated power can be converted back to the measured current value, and the current value can be compared with the current limit.

[0016] In a further development of the electronic control system, it can be provided that at least one conversion function defining the predetermined functional relationship is stored in the electronic fuse, and the control and evaluation device is configured to set the reference value based on the at least one conversion function by means of a received frequency signal. The at least one conversion function can, in particular, comprise a component that is proportional to a received frequency signal. Such a conversion function can comprise at least one time-dependent component. Viewed very generally, a conversion function defining the predetermined functional relationship is dependent on at least one parameter, e.g.the frequency or pulse width of the respective received frequency signal, which can be constant over time or time-dependent, and can also have an additive constant or an additive, optionally also time-dependent, term. Several conversion functions can also be stored in the electronic fuse, so that the electronic fuse allows different types of adjustment of the reference value, based on different conversion functions, depending on the DC load to be connected to the electronic fuse or depending on the respective received frequency signal.

[0017] As an alternative to a conversion function, according to a further development, it can also be provided that an assignment rule defining the predetermined functional relationship is stored in the electronic fuse in the form of at least one table, and that the at least one table has, in particular, a list with individual frequency signals or individual frequency signal ranges contained therein as well as individual power limit values, wherein each frequency signal or each frequency signal range is assigned exactly one power limit to be set. Thus, by accessing the table, the control and evaluation device can determine the respective power limit value assigned to the received frequency signal according to the table. The table can, for example,comprise a list of individual frequency signals contained therein, the assignment to a specific power limit being based on one or more parameters underlying the frequency signals, such as the frequency and / or the pulse width.

[0018] Furthermore, it can be provided, additionally or alternatively, that the predetermined functional relationship is a proportional relationship and that a first proportionality factor defining the proportional relationship is stored in the control and evaluation device. In this case, the control and evaluation device is configured to set the reference value, in the case of a received temporally constant frequency signal, to a temporally constant power limit value based on the first proportionality factor. The first proportionality factor can in particular be proportional to a previously set reference value, e.g. a reference value defined by a predetermined triggering characteristic, so that the previously set reference value is increased or decreased by a constant factor using the received frequency signal.In addition, a first conversion function defining the proportional relationship can optionally be stored in the control and evaluation device, so that the control and evaluation device is configured to set the reference value based on the first conversion function using the frequency signal. The first conversion function can be represented, for example, by a frequency-dependent function of the adjustable reference value or the power limit value P& (V) = arv + ß, where v denotes the frequency underlying the temporally constant frequency signal, cti denotes the first proportionality factor, and ß is an optional additive constant that can, among other things, also assume the value zero.Additionally or alternatively, if the predetermined functional relationship is a proportional relationship, a second proportionality factor defining the proportional relationship can optionally be stored in the control and evaluation device, wherein the control and evaluation device can be configured to set the reference value, in the case of a received time-dependent frequency signal, to a time-dependent power limit based on the second proportionality factor. The power limit can be temporally variable, in particular stepwise or abruptly, using the received time-dependent frequency signal. The second proportionality factor can correspond to the aforementioned first proportionality factor or differ from the first proportionality factor.This further development of the electronic fuse makes it possible to provide the power limit with an adjustable time dependency. This is particularly advantageous when switching on a connected DC load, such as a motor, which usually results in an overcurrent for a short period of time. The switch-on characteristics of the DC load can thus be taken into account by the adjustable time-dependent power limit. This means that the power limit can be set using the received time-dependent frequency signal either synchronously with the switch-on of the DC load or, preferably, shortly before the DC load is switched on, so that it is always greater than a respective power value that is provided during switch-on of the DC load. Furthermore, the control and evaluation device can, for example,a second conversion function defining the proportional relationship can be stored, so that the control and evaluation device is configured to set the reference value based on this second conversion function using the received time-dependent frequency signal. Such a second conversion function can be represented, in accordance with the previously described first conversion function, e.g., by a frequency-dependent function of the adjustable reference value or the power limit value P& (V (t)) = oi2'v(t) + ß, where v(t) denotes the time-dependent frequency underlying the frequency signal, ß denotes the second proportionality factor, and ß is an optional additive constant which, among other things, can also assume the value zero.In a further development of the electronic fuse, the reference value can be stored in advance in the electronic fuse in the form of a characteristic curve, and the control and evaluation device can be configured to shift the characteristic curve by a temporally constant value proportional to the received frequency signal as a function of a received temporally constant frequency signal, and to set the power limit based on the characteristic curve shifted by the temporally constant value. The characteristic curve is to be understood in particular as a tripping characteristic that is assigned to a respective DC load to be connected or connected to the electronic fuse. According to this embodiment, a so-called "offset shift" of the characteristic curve occurs by a temporally constant value that depends proportionally on the received frequency signal.Based on the shift of the stored characteristic curve, different power limits can be set. In this case, too, a third conversion function can be stored in the control and evaluation device, for example, so that the control and evaluation device is configured to set the reference value based on this third conversion function using a received time-dependent frequency signal. The third conversion function can, for example, be implemented by a frequency-dependent function of the adjustable reference value orof the power limit value PGT (V, t) = XI (t) + ß v, where v denotes the frequency underlying the frequency signal, XI (t) describes the function of the characteristic curve, which can be time-independent or time-dependent, and ß describes an additive constant not equal to the value zero, which, multiplied by the frequency v of the frequency signal, causes a shift of the characteristic curve in the y-direction of a corresponding coordinate system by a constant value.

[0019] In addition or as an alternative to the previously described embodiment, the reference value can be stored in advance in the electronic fuse in the form of a characteristic curve, and the control and evaluation device can be configured to set the reference value to a different power limit value by means of a received frequency signal depending on the direction of energy flow through the electronic fuse, in particular in such a way that, when the direction of energy flow is from the output terminal to the input terminal of the electronic fuse, the control and evaluation device mirrors the characteristic curve stored in the electronic fuse or a characteristic curve shifted by a time-constant value, as described above, on the x-axis depending on the received frequency signal and sets the power limit value based on the correspondingly mirrored characteristic curve. The x-axis is in particular a time axis.For example, in the case of a first frequency signal received by the electronic fuse, the control and evaluation device can set a positive power limit defined by the stored characteristic curve or, if applicable, by a characteristic curve shifted by a constant value, as previously explained. While in the case of a second frequency signal received by the electronic fuse that is different from the first frequency signal, the control and evaluation device can set a negative power limit defined by a mirroring of the stored characteristic curve or by a mirroring of a characteristic curve shifted by a constant value on the x-axis. This can be implemented in different ways, with correspondingly defined differentiation criteria being stored in the control and evaluation device, which are used to set the reference value using the respective received frequency signal.Differentiation criteria can be used, for example, to determine the respective values ​​or value ranges of individual parameters of the received frequency signal. These parameters can be, for example, the frequency and / or the pulse width of the received frequency signal.

[0020] The electronic fuse can further be designed such that the voltage measuring device is configured to detect the voltage along a voltage measuring path and the current measuring device is configured to detect the current along a current measuring path, and the voltage measuring path and the current measuring path are jointly connected to a node. This has the advantage, among other things, that fewer components and / or connecting cables are required, which reduces the circuit complexity compared to a design without a common connection to a node. The present invention also relates to a power monitoring system which comprises an electronic fuse according to one of the previously described embodiments and furthermore a control device, in particular a programmable logic controller (PLC). The electronic fuse furthermore has a control output electrically connected to the control and evaluation device.The control device is electrically connected to both the control input and the control output of the electronic fuse and is configured to receive data, in particular data relating to a detected voltage, a detected current, and a calculated power, from the electronic fuse via the control output and to transmit data and command signals, in particular a frequency signal for setting a reference value, to the electronic fuse via the control input of the electronic fuse. The electronic fuse and the control device of the power monitoring system thus regularly exchange data with each other to ensure proper operation of a DC load connected to the electronic fuse.

[0021] According to a further development of the power monitoring system, the control device can comprise a frequency generator and be configured to generate a first frequency signal for setting the reference value by means of the frequency generator and to transmit this signal to the electronic fuse. The control device can also comprise, in particular, a memory device with program logic stored therein for switching a DC load connected to the electronic fuse on and off, and with characteristic data of this DC load stored therein, in particular a load characteristic curve or tripping characteristic curve. Furthermore, the control device can be configured, in particular, to control the frequency generator to generate the first frequency signal based on the information stored in the memory device.The control of the frequency generator to generate a frequency signal to be transmitted to the electronic fuse is thus based in particular on specific information regarding the DC load connected to the electronic fuse. The reference value is thus set according to the respective specifications of the control device, which are derived from the program logic and the characteristics of the connected DC load.

[0022] Furthermore, the power monitoring system can be further developed in particular such that the electronic fuse is configured to provide a second frequency signal corresponding to the calculated power at the control output, and the control device is configured to receive the provided second frequency signal and to detect the calculated power from it. For example, after the power value has been calculated, the control and evaluation device of the electronic fuse can be configured to calculate the second frequency signal from the calculated power value by using a predetermined functional relationship that is inverse to the predetermined functional relationship, for example, a corresponding inverse conversion function.

[0023] In addition or alternatively, the power monitoring system can be further developed such that the control device is further configured to transmit a reset signal to the electronic fuse in the event of a fault event. This ensures that the electronic fuse can be returned to its operational state after the cause of the fault event has been eliminated.

[0024] Furthermore, the present invention relates to a method for operating an electronic fuse, in particular an electronic fuse according to one of the previously described embodiments, in a DC voltage network. The method comprises the steps of electrically connecting the electronic fuse to the DC voltage network, electrically connecting a DC voltage load to the electronic fuse, and applying a frequency signal to a control input of the electronic fuse. Furthermore, the method comprises detecting a current flowing through the electronic fuse, detecting a voltage applied to the electronic fuse, calculating a power provided by the electronic fuse based on the detected current and the detected voltage, and comparing the calculated power with a reference value that defines a power limit.This reference value is set using the applied frequency signal, which has a predetermined functional relationship to the reference value. If the calculated power exceeds the power limit, the method provides for disconnecting the DC load from the DC network. The DC load is disconnected from the DC network by switching a switching device enclosed by the electrical fuse to the non-conductive state. The received frequency signal thus specifies the value to which the reference value or power limit is set.

[0025] In a further development of the method according to the invention, it can be provided in particular that the frequency signal is applied as a function of specific characteristics of the connected DC voltage load, in particular a load characteristic curve, and that the predetermined functional relationship is stored in the electronic fuse in the form of at least one conversion function. The conversion function can optionally comprise at least a component proportional to a respectively applied frequency signal. As an alternative to such a conversion function, the predetermined functional relationship can also be stored in the electronic fuse as an assignment rule in the form of at least one table. As previously described, the table comprises an assignment between one or more frequency signals, in particular based on one or more parameters underlying the respective frequency signal, to corresponding power limit values.

[0026] According to the method according to the invention, it can be provided, for example, that the applied frequency signal is proportional to the reference value, so that the reference value is set to a temporally constant power limit by means of the frequency signal when the frequency signal is temporally constant, and is set to a time-dependent power limit by means of the frequency signal, in particular a power limit that can be changed step by step or suddenly, when the frequency signal is time-dependent. As already described above with regard to the electronic fuse, in this case a conversion function defining the proportional relationship can be stored in the electronic fuse, based on which the reference value can be set in each case using a corresponding frequency signal.

[0027] In a further development, in addition to or as an alternative to the previously described embodiments, it can be provided that the reference value is stored in advance in the electronic fuse in the form of a characteristic curve, and the applied frequency signal is proportional to a temporally constant value to be added to the characteristic curve, so that the power limit is set based on a characteristic curve shifted by the temporally constant value. The characteristic curve is, in particular, a tripping characteristic that is assigned to a respective DC voltage load to be connected or already connected to the electronic fuse.

[0028] Additionally or alternatively, it can be provided that the reference value is stored in advance in the electronic fuse in the form of a characteristic curve and is set to a different power limit value by means of the applied frequency signal depending on the direction of energy flow through the electronic fuse. With an energy flow direction from the output terminal to the input terminal of the electronic fuse, the characteristic curve stored in the electronic fuse, or a characteristic curve shifted by the time-constant value as described above, can be mirrored on the x-axis depending on the applied frequency signal, and the power limit value can be set based on the correspondingly mirrored characteristic curve.

[0029] Further advantages, features, and possible applications of the present invention will become clear from the following description of embodiments thereof and the accompanying figures. Figure 1 shows a schematic representation of a power monitoring system comprising an electronic fuse according to a first embodiment of the invention.

[0030] Figure 2: two alternative embodiments a) and b) of a circuit device of an electronic fuse according to the invention, each of which is in accordance with Figure 1,

[0031] Figure 3a: a time course of a received frequency signal, a power limit value set by means of the frequency signal and a calculated power value according to a first embodiment of the invention,

[0032] Figure 3b: a time course of a received frequency signal, a power limit value set by means of the frequency signal and an inrush current of a DC load according to a second embodiment of the invention,

[0033] Figure 3c: a time course of two different received frequency signals and two power limit values ​​set by means of the respective frequency signal according to a third embodiment of the invention,

[0034] Figure 3d: a time course of a frequency signal superimposed from two different frequency signals, a characteristic curve and a characteristic curve modified by means of the superimposed frequency signal according to a fourth embodiment of the invention,

[0035] Figure 4: a block diagram of a method for operating the electronic fuse according to Figure 1 according to an embodiment of the invention,

[0036] Figure 5: a diagram illustrating the time course of the method for operating an electronic fuse according to an embodiment of the invention. Figure 1 shows a schematic representation of a power monitoring system 10 comprising an electronic fuse 1 according to a first embodiment of the invention. The power monitoring system 10 shown comprises an electronic fuse 1 according to the invention and a control device 11, which in the embodiment of Figure 1 is designed as a programmable logic controller (PLC), but can also be designed differently in further embodiments.The electronic fuse 1 serves to protect a DC load 3 arranged in a DC voltage network 2 and has at least one input terminal IN designed for electrical connection to the DC voltage network 2, in Figure 1 two input terminals IN already electrically connected to a DC voltage supply rail 2A of the DC voltage network 2, and at least one output terminal OUT designed for electrical connection of a DC load 3, in Figure 1 two output terminals OUT already electrically connected to a load rail 3A with a DC load 3 connected thereto. In addition, the electronic fuse 1 comprises a control input 4 and furthermore in particular a control output 5, wherein the control device 11 of the power monitoring system 10 is electrically connected to the control input 4 and to the control output 5 of the electronic fuse 1.Furthermore, the electronic fuse 1 according to Figure 1 has a controllable switching device 6 arranged between the input terminal IN and the output terminal OUT, which in Figure 1 is designed as an example as a bipolar transistor with a relay 15 and galvanic isolation.

[0037] However, the controllable switching device can also be constructed differently than that shown in Figure 1. For example, Figure 2 shows two respective alternative embodiments of an exemplary controllable switching device of an electronic fuse according to the invention to the switching device 6 according to Figure 1. For example, the switching device 6' shown in Figure 2a) is designed, by way of example, as a bipolar transistor with an insulated gate electrode (so-called "insulated-gate bipolar transistor", IGBT for short) in an anti-serial circuit for energy flow in both directions. Figure 2b) shows a further example of a controllable switching device 6", which is designed as a bipolar transistor with an insulated gate electrode (so-called "insulated-gate bipolar transistor", IGBT for short) in an anti-serial circuit for energy flow in both directions and with additional galvanic isolation.

[0038] In addition, the electronic fuse 1 outlined in Figure 1 has a current measuring device 7, which is designed to detect a current flowing through the electronic fuse 1, and a voltage measuring device 8, which is designed to detect a voltage applied to the electronic fuse 1. As shown by way of example in Figure 1, the voltage measuring device 7 is designed to detect the voltage along a voltage measuring path and the current measuring device 8 is designed to detect the current along a current measuring path. The voltage measuring path and the current measuring path are, for example, connected together at a node X. This has the advantage, among other things, that fewer components and / or connecting cables are required, which leads to less circuitry complexity compared to a design without a common connection at a node.

[0039] In addition, the electronic fuse 1 comprises a control and evaluation device 9, which is electrically connected to the current measuring device 7, the voltage measuring device 8 and the control input 4 and, furthermore, according to Figure 1, in particular also to the control output 5. In Figure 1, the control and evaluation device 9 is optionally designed as a microprocessor. The control and evaluation device 9 is configured to calculate a power based on a current detected by the current measuring device 7 and a voltage detected by the voltage measuring device 8 and to compare this calculated power with a reference value, which defines a power limit and, in the example of Figure 1, corresponds to a power limit, in particular continuously or at predetermined time intervals.A comparison that occurs either continuously or at least at regular intervals enables a constantly updated comparison result and the corresponding measures to be derived from it. Furthermore, the control and evaluation device 9 is configured, in the event of a calculated power that is greater than the power limit, to cause the switching device 6, or a switching device 6', 6" configured according to Figure 2a) or 2b), to disconnect the connected DC load 3 from the DC network 2, i.e., to switch the switching device 6 to the non-conductive state.

[0040] The electronic fuse 1 is further configured to receive, via its control input 4, a frequency signal having a predetermined functional relationship to the reference value, by means of which the reference value can be adjusted. The electronic fuse 1 thus enables the reference value or the switching threshold value of the electronic fuse 1 to be adjusted in such a way that the reference value can be flexibly, in particular dynamically, adapted to a time-varying energy requirement of the DC load 3 connected to the electronic fuse 1 and to be supplied with energy. For example, even during operation of the electronic fuse 1 and the DC load 3 connected to it, it is possible to dynamically adapt the reference value to the current conditions, in particular a respective time-dependent energy requirement or current requirement, of the electrically connected DC load 3.To set the reference value, a frequency signal received by the electronic fuse 1 via its control input 4 is used. The frequency signal has a predetermined functional relationship to the reference value, so that a change in the frequency signal also causes a change in the reference value. The control and evaluation device 9 of the electronic fuse 1 processes the received frequency signal in such a way that it determines the reference value or the power limit defined thereby from the frequency signal based on the predetermined functional relationship, which essentially defines at least one assignment rule between a frequency signal and a reference value, and sets it accordingly. The power limit set using the frequency signal is thus defined as the switching threshold.The reference value can be set either once using a single frequency signal or multiple times, with the reference value being set using a respective received frequency signal in the latter case. To check whether the DC load 3 connected to the electronic fuse is operating within a permissible parameter range, the control and evaluation device 9 of the electronic fuse 1 compares the respectively calculated power value, which is calculated based on the recorded current and voltage measurements, with the set reference value or the power limit value. In the example in Figure 1, this comparison is performed essentially continuously, but in another embodiment, it can also be performed at predetermined time intervals.The smaller these time intervals are selected, the faster a fault based on an inadmissible comparison result can be detected in order to initiate appropriate measures to switch off the connected DC load 3. If the control and evaluation device 9 determines during the comparison that the calculated power value is greater, specifically greater in magnitude, than the determined power limit, this is evaluated as an inadmissible comparison result based on a fault-related exceeding of the power limit, e.g., due to an overcurrent. Therefore, the control and evaluation device 9 disconnects the connected DC load 3 from the DC network 2 by appropriately controlling the switching device 6. This means that the control and evaluation device 9 switches the switching device 6 into a non-conductive state by appropriately controlling it.The DC load 3 is therefore separated from the power supply of the DC network 2 and thus switched off. If, however, the control and evaluation device 9 determines during the comparison that the calculated power value is not greater, and in particular not greater in amount, than the determined power limit, it does not disconnect the connected DC load 3 from the DC network 2. The proper operation of the electronic fuse 1 and the DC load 3 connected to it is therefore maintained. The control and evaluation device 9 waits for the subsequently recorded voltage and current measured values ​​in order to again calculate a current power value and compare this with the power limit. The power limit can either correspond to the previously determined power limit or can be determined using a new orcurrent frequency signal and based on the assignment rule defining the predetermined functional relationship.

[0041] It can be provided that a reference value has already been initially specified or preset or is stored, for example, in the form of a tripping characteristic in the electronic fuse 1, in particular in a memory device of the electronic fuse 1. In this case, the preset reference value or the specified tripping characteristic are included as corresponding information in the predetermined functional relationship and are thus taken into account when setting the reference value or determining the power limit based on a respective received frequency signal. Accordingly, the reference value set using a received frequency signal can in particular be larger, but also smaller, than an initially specified reference value.

[0042] The power calculation performed by the electronic fuse 1 has the advantage, among other things, that the power calculation determines the actual power supplied to a connected DC load 3, so that any supply line losses along the DC supply rail 2A on the input side of the electronic fuse 1 are irrelevant. In the optional case where current value monitoring is desired using the electronic fuse, the power limit defined by the reference value can, for example, also be converted back to a current limit, or a reference value can be used that corresponds to a current limit. Furthermore, the calculated power can be converted back to the recorded current value, and the current value can be compared with the current limit.

[0043] In the exemplary embodiment of Figure 1, the predetermined functional relationship is present, for example, in the form of at least one conversion function that defines an assignment rule corresponding to the predetermined functional relationship and is stored in the electronic fuse 1. According to the exemplary embodiment of Figure 1, several different conversion functions are also stored in the electronic fuse 1, which are used to set the reference value depending on a DC voltage load 3 connected to the electronic fuse 1. The conversion function to be used in each case is optionally determined by the control and evaluation device 9, based on the respective received frequency signal or the respective connected DC voltage load.According to Figure 1, the control and evaluation device 9 is further configured, by way of example, to set the reference value based on the at least one conversion function using the received frequency signal. Although this is not apparent from Figure 1, this conversion function includes, by way of example, at least one component that is proportional to the received frequency signal.

[0044] According to a further embodiment not shown, as an alternative to a conversion function, an assignment rule defining the predetermined functional relationship can also be stored in the electronic fuse in the form of at least one table. This table has, in particular, a list containing individual frequency signals or individual frequency signal ranges, in particular the parameters underlying a respective frequency signal, as well as individual power limit values, wherein each frequency signal or each frequency signal range is assigned precisely one power limit to be set, in particular depending on the respective underlying parameters of a frequency signal. Depending on the received frequency signal, the control and evaluation device can determine the respective power limit value assigned to the received frequency signal according to the table by accessing the table.

[0045] Individual embodiments with regard to the predetermined functional relationship are explained in more detail with regard to Figures 3a, 3b, 3c and 3d.

[0046] The control device 11 of the power monitoring system 10 shown in Figure 1 is electrically connected to the electronic fuse 1, specifically the control and evaluation device 9 of the electronic fuse 1, via the control input 4 and the control output 5 and is in data exchange with the control and evaluation device 9. Accordingly, the control device 11 is designed to receive data, in particular data relating to a detected voltage, a detected current and a calculated power, from the electronic fuse 1 via the control output 5 and to transmit data and command signals, in particular a frequency signal for setting a reference value, to the electronic fuse 1 via the control input.

[0047] As can be seen in Figure 1, the control device 11 comprises, for example, a frequency generator 13 and is configured to generate a first frequency signal for setting the reference value by means of the frequency generator 13 and to transmit this signal to the electronic fuse 1 via its control input 4. Furthermore, the control device 11 has, for example, a memory device 14 with program logic stored therein for switching a DC load 3 connected to the electronic fuse 1 on and off, and with characteristic data of the DC load 3 stored therein, in particular a load characteristic curve or tripping characteristic curve. The program logic thus specifies, in particular, the point in time at which a respective DC load 3 is to be connected to the load bus 3A or disconnected from it.Figure 1 shows a state in which a first DC load 3 is electrically connected to the load rail 3A and a second DC load 3 is not electrically connected to the load rail 3A, represented in Figure 1 by the open switch 16 controlled by the control device 11 according to the dashed line. The control device 11 shown in Figure 1 is further configured, by way of example, to control the frequency generator 11 to generate the first frequency signal based on the information stored in the memory device 14. The reference value is thus set according to Figure 1 in accordance with the specifications of the control device 11, which arise from the program logic and the characteristics of the connected DC load 3.

[0048] The electronic fuse 1 of the power monitoring system 10, sketched in Figure 1, is also designed, by way of example, to provide a second frequency signal corresponding to the calculated power at its control output 5. Accordingly, the control device 11 is designed to receive the provided second frequency signal and to determine the calculated power therefrom. According to Figure 1, the control and evaluation device 9 of the electronic fuse

[0049] I is configured, for example, to calculate and generate a corresponding second frequency signal from the respectively calculated power value. The calculation is carried out based on the predetermined functional relationship in reverse or inverse form by applying the assignment rule defined by the predetermined functional relationship in reverse or inverse form. According to Figure 1, the reference value is set, for example, based on a conversion function using the received frequency signal, so that the conversion function inverse to this conversion function, also called the inverse function, is used by the control and evaluation device 9 to calculate the second frequency signal.However, in an alternative embodiment, a table stored in the electronic fuse could also be used, which table comprises an assignment between one or more frequency signals, in particular based on one or more parameters underlying the respective frequency signal, and corresponding power limit values.

[0050] According to Figure 1, the DC voltage network optionally has a readout function D1, via which the control device 11 can, for example, query the current load status. Based on this information and the second frequency signal received via the control output 5 of the electronic fuse 1, the control device 11 can combine the states of the DC voltage loads connected to the electronic fuse 1 in order, for example, to coordinate and, if necessary, prioritize the energy supply for the DC voltage loads.

[0051] The control device of the performance monitoring system shown in Figure 1

[0052] II is further configured, by way of example, to transmit a reset signal to the electronic fuse 1 in the event of a fault event. This ensures that the electronic fuse 1 can be returned to an operational state once the cause of the fault has been eliminated. Transmitting the reset signal by the control device 11 to the electronic fuse 1 has the advantage that a switch or button on the electronic fuse 1 for manual operation by a user is not required. The control device can, for example, send an automatically generated reset signal to the electronic fuse after a predetermined period of time has elapsed. Alternatively, a corresponding program sequence can be stored in the control device 11, which is executed when faults or errors occur.error events, whereby after evaluating a predetermined event a corresponding reset signal is automatically sent to the electronic fuse 1.

[0053] Figure 3a shows a temporal profile of a received frequency signal Fl, a power limit value P& set using the frequency signal Fl, and a calculated power value Pb according to a first embodiment of the invention. The frequency signal Fl shown is plotted in the upper image of Figure 3a with regard to its amplitude A(t) over time t and represents a temporally constant frequency signal, i.e. its frequency or period is constant over time. If the electronic fuse illustrated, for example, in Figure 1 receives such a temporally constant frequency signal Fl via its control input, a reference value is set using the frequency signal Fl, which is defined by a temporally constant power limit value P&. In the example in Figure 3a, it can be seen that the respective calculated power value Pb is smaller than the set power limit value PGT, the temporal profile of which is shown by a dotted line.Thus, the DC load is not disconnected from the DC network. The adjustability of the reference value or power limit P& is based in this case, for example, on a predetermined functional relationship, which is a proportional relationship. A first proportionality factor ai defining the proportional relationship is stored in the electronic fuse 1, in particular the control and evaluation device, so that the control and evaluation device is configured to adjust the reference value, in the case of the received temporally constant frequency signal Fl, to the temporally constant power limit P& based on the first proportionality factor ai. To adjust the reference value, for example,a first conversion function defining the proportional relationship must be stored in the control and evaluation device, based on which the control and evaluation device can set the power limit value P& using the frequency signal Fl. Such a first conversion function can, for example, be represented by a frequency-dependent function of the adjustable reference value or power limit value Pc (V) = arv + ß. Here, v denotes the frequency underlying the time-constant frequency signal Fl and oii the first proportionality factor and ß is an optional additive constant which, for example, can also take the value zero. The first proportionality factor in this example is a reference value specified initially, e.g.a current or power limit, dependent value and can be mathematically described by ai = a Po, where Po denotes the initially specified reference value and a is a predefined factor, in particular a conversion factor. Thus, an initially specified reference value Po can be increased or decreased by a constant factor using the frequency signal Fl. As an alternative to a frequency-dependent function of the adjustable reference value, it is also conceivable, for example, to use a pulse width-dependent function of the adjustable reference value or power limit as a conversion function, so that the power limit depends on the respective pulse width of the received frequency signal.

[0054] Figure 3b shows a time profile of a received frequency signal F2(t) that is different from that in Figure 1, a time profile of a power limit value P& set using the frequency signal F2(t), and an inrush current I(t) of a DC load according to a second embodiment of the invention. In contrast to the frequency signal F2(t) shown in Figure 3a, it can be seen that the frequency signal F2(t) according to the upper image of Figure 3b is a time-dependent frequency signal, i.e. its frequency changes over time and, in the exemplary embodiment, increases over time at time t1, in this case step by step. The time dependence of the frequency signal F2(t) is transferred to the power limit value P& set using the frequency signal F2(t) based on the correspondingly predetermined functional relationship, as the middle image of Figure 3b shows.At time t2, which, due to an internal processing time of the control and evaluation device, occurs after time ti, a time-dependent power limit P& is established, also referred to as a dynamic switching threshold, which increases over time. This allows the power limit P& to be dynamically adapted to the respective operating and / or switch-on conditions of the DC load to be connected. If the DC load is switched on at time t3 > t2, the power supplied to the DC load is still below the set power limit P& despite an increased inrush current occurring at the beginning of switching on, thanks to the dynamic adjustment of the power limit P&, so that it is not switched off, as indicated in the lower image of Figure 3b.

[0055] The adjustability of the reference value or the dynamic power limit value P& is also based in this case, for example, on a predetermined functional relationship, which is a proportional relationship. A second proportionality factor a.2 defining the proportional relationship is stored in the electronic fuse, in particular in the control and evaluation device, so that the control and evaluation device is configured to set the reference value, in the event of a received time-dependent frequency signal F2(t), to the time-dependent power limit value Por(t) based on the second proportionality factor 012. The power limit value Por(t) can be changed stepwise over time using the received time-dependent frequency signal F2(t), as shown in the example in Figure 3b, or in an alternative embodiment, abruptly. To set the reference value, for example,a second conversion function defining the proportional relationship must be stored in the control and evaluation device, based on which second conversion function the control and evaluation device can set the time-dependent power limit value P& using the frequency signal F2(t). The second conversion function can be represented, for example, by a frequency-dependent function of the adjustable reference value or the power limit value P& (V (t)) = oi2'v(t) + ß, where v(t) denotes the time-dependent frequency underlying the frequency signal F2(t), 012 denotes the second proportionality factor, and ß is an optional additive constant which, among other things, can also have the value zero. The second proportionality factor can either be different from the first proportionality factor or correspond to it, so that the first and second conversion functions are identical, apart from the respective time dependence of the frequency signal F2(t) and the power limit value.The second proportionality factor can also be a value dependent on an initially specified reference value and can be mathematically described, for example, by 012 = a' -Po with the initially specified reference value Po, where a' represents a predefined factor, in particular a conversion factor, which corresponds to the factor a with respect to the first proportionality factor if 012 = ai. Thus, an initially specified reference value Po can be set to a time-dependent power limit value PGT and thus a dynamic switching threshold value using the time-dependent frequency signal F2(t).

[0056] Figure 3c shows a temporal profile of two different received frequency signals F3 and F4 as well as two power limit values ​​respectively set by means of these frequency signals F3, F4 according to a third embodiment of the invention. As can be seen from the upper image of Figure 3c, the two frequency signals F3, F4 are temporally constant frequency signals that differ in their underlying frequency. The frequency signal F4, for example, has a higher frequency than the frequency signal F3. In the embodiment illustrated in Figure 3c, the reference value is stored in advance in the electronic fuse in the form of a characteristic curve Xl(t), which is depicted in the lower image of Figure 3c and corresponds to a load characteristic curve, also called a tripping characteristic curve or tripping curve of the DC load to be connected or connected to the electronic fuse.In this case, the control and evaluation device of the electronic fuse is configured, for example, to shift this characteristic curve XI(t) as a function of a received temporally constant frequency signal, which in Figure 3c corresponds to the frequency signal F4, by a temporally constant value AP proportional to the received frequency signal F4, and to set the power limit value PGT based on the characteristic curve X2(t) shifted by the temporally constant value AP. As can be seen in the lower image of Figure 3c regarding the temporal course of the power limit value, a so-called "offset shift" of the characteristic curve XI(t) relative to the shifted characteristic curve X2(t) occurs by a temporally constant value AP, which depends proportionally on the frequency signal F4.If, for example, the electronic fuse receives a frequency signal F3 according to the embodiment of Figure 3c, the stored characteristic curve XI(t) is used as the reference value based on this. If, on the other hand, the electronic fuse receives a frequency signal F4 according to the embodiment of Figure 3c, the stored characteristic curve X1(t) is shifted by the constant value AP to the characteristic curve X2(t). This occurs because the predetermined functional relationship stored in the electronic fuse for setting the reference value is present, for example, in the form of a third conversion function. The third conversion function can be represented, for example, by a frequency-dependent function of the adjustable reference value or the power limit value P& (V, t) = XI (t) + ß v.Here, v denotes the frequency underlying the respective frequency signal F3, F4, XI (t) describes the function of the characteristic curve, which in this case is time-dependent, and ß describes an additive constant not equal to zero, which, multiplied by the frequency v of the respective frequency signal, causes a corresponding offset shift of the characteristic curve Xl(t) by the constant value AP = ß-v. As an alternative to a third conversion function, a table could also be stored in the electronic fuse, for example, from which an assignment rule between a respective frequency signal and a constant value defining the offset shift of the stored characteristic curve XI (t) emerges.

[0057] Figure 3d shows a temporal progression of a frequency signal composed of two different frequency signals F5 and F6 superimposed, and a temporal progression of a stored characteristic curve, as well as a characteristic curve modified based on the superimposed frequency signal, according to a fourth embodiment of the invention. As can be seen from the upper image of Figure 3d, the two frequency signals F5, F6 of the superimposed frequency signal are each temporally constant frequency signals that differ in their respective pulse widths. For example, the frequency signal F5 has a larger pulse width than the frequency signal F6. In the exemplary embodiment illustrated in Figure 3d, the reference value is stored in advance in the electronic fuse in the form of a characteristic curve Xl(t).The characteristic curve XI (t) is shown as an example in the lower image of Figure 3d and corresponds to a load characteristic curve, also called a tripping characteristic or tripping curve, of the DC load to be connected or connected to the electronic fuse. The control and evaluation device of the electronic fuse is configured, for example, to set the reference value to a different power limit value P& using a received frequency signal—in the example of Figure 3d, the frequency signal superimposed from F5 and F6—depending on the direction of energy flow through the electronic fuse.This can be done in particular in such a way that the control and evaluation device, with an energy flow direction from the output terminal to the input terminal of the electronic fuse, mirrors the characteristic curve XI(t) stored in the electronic fuse, or a characteristic curve shifted by a time-constant value, for example the characteristic curve X2(t) shifted by AP according to Figure 3c, on the x-axis as a function of the received frequency signal and sets the power limit value P& based on the correspondingly mirrored characteristic curve X3(t). The x-axis corresponds to the time axis in Figure 3d. As shown in the lower image of Figure 3d, in addition to the characteristic curve Xl(t), another characteristic curve X3(t) = - (XI(t) -PI) can be seen, which, starting from the characteristic curve Xl(t), is shifted by a constant value PI and then mirrored on the time axis designed as the x-axis.If the electronic fuse receives a frequency signal superimposed from the frequency signals F5 and F6 according to the embodiment shown in Figure 3d, the frequency signals F5, F6 are evaluated separately from one another in the control and evaluation device. In Figure 3d, the characteristic curve XI(t) stored in the electronic fuse is shifted, for example, based on the frequency underlying the frequency signal F5 by the constant value PI, specifically towards smaller values, and is mirrored on the time axis based on the pulse width underlying the frequency signal F6 as a further parameter. The resulting characteristic curve X3(t) is therefore used to set the reference value or power limit using the frequency signal superimposed from F5 and F6.

[0058] To enable this, the control and evaluation device stores correspondingly defined differentiation criteria, which are used to set the reference value using the respective received frequency signal. The differentiation criteria can be, for example, the respective value ranges of individual parameters of the respective received frequency signal. The parameters can be, for example, the frequency and / or the pulse width of the received frequency signal. The differentiation criteria must always be clearly distinguishable from one another and define a predetermined functional relationship, which can be presented in the form of at least one table or other assignment rules.

[0059] For example, a first parameter, e.g., the frequency, of a received frequency signal can be used to set an offset shift of the characteristic curve pre-stored in the electronic fuse, and a second parameter, e.g., the pulse width of the same frequency signal, a superimposed frequency signal, or even another received frequency signal, can be used for an optional mirroring of the characteristic curve on the x-axis or time axis. For example, with regard to optional mirroring, it can be specified that no mirroring should occur for a pulse width of a frequency signal that is greater than a predetermined value, and a mirroring of the characteristic curve on the x-axis should occur for a pulse width of the frequency signal that is less than or equal to the predetermined value.In order to be able to set a reference value by means of a frequency signal using a combination of shifting and mirroring a characteristic curve stored in the electronic fuse, however, differentiation criteria based on two different parameters of a frequency signal are not necessarily required. Such a setting option also exists, for example, when two different frequency signals are received, in particular one after the other, with a short time interval, wherein an offset shift can be set using the first frequency signal and an optional mirroring of the characteristic curve can be set using the second frequency signal. In this case, mutually definable differentiation criteria can be defined based on a single parameter, in particular the frequency or the pulse width, of the respective frequency signals, e.g. two or four different value ranges for the same parameter of the two respective frequency signals.

[0060] Even if this is not shown in Figure 3d, it is also possible, among other things, to mirror a characteristic curve previously stored in the electronic fuse only on the x-axis, without being able to set an additional offset shift. In this case, a corresponding differentiation criterion is defined based on a single parameter of the frequency signal and is stored in the control and evaluation device as information. For example, a frequency signal with a previously defined first value range of the parameter can set a positive power limit value that is defined by the stored characteristic curve, and a frequency signal with a previously defined second value range of the same parameter that is different from the first can set a negative power limit value that is defined by a mirroring of the stored characteristic curve on the x-axis.

[0061] Figure 4 shows a block diagram of a method for operating an electronic fuse, in particular the electronic fuse shown in Figure 1, in a DC voltage network according to one embodiment of the invention. Even if this is not apparent from Figure 4, the electronic fuse is first electrically connected to the DC voltage network and a DC voltage load is electrically connected to the electronic fuse. In addition, a frequency signal is applied to a control input 4 of the electronic fuse. This frequency signal can, for example, be designed according to one of the frequency signals F1, F2(t), F3, F4, F5, F6 shown in Figures 3a, 3b, 3c or 3d. According to Figure 4, in block G1, for example, a frequency-to-digital conversion takes place, i.e. the received frequency signal is converted into a digital signal, and the converted signal is forwarded to block E.In addition, the frequency signal received via control input 4 is fed to an edge detection circuit according to block FEI of Figure 4 and then transmitted to an AND gate symbolized by block H. In block B of Figure 4, a current flowing through the electronic fuse is detected, and in block C, a voltage applied to the electronic fuse is detected. Based on the detected current and the detected voltage, a power provided by the electronic fuse is calculated in block D. In block E, the calculated power is compared with a reference value defining a power limit. This reference value is set using the applied frequency signal, which, according to Figure 4, is transmitted to block E as a converted digital signal, for example, and has a predetermined functional relationship to the reference value.The comparison result is transmitted, as shown in Figure 4, to the AND gate in block H. If the calculated power is greater than the power limit, the DC load is disconnected from the power supply. In this case, a logical AND operation occurs in the AND gate, and the switching device 6 is switched to the non-conductive state by means of a corresponding control command, which is indicated in Figure 4 by the dashed line. In block G2, a digital signal corresponding to the calculated power is converted into a frequency signal corresponding to a previously described second frequency signal, which is transmitted to block FE2, where edge detection takes place. From block FE2, the frequency signal is forwarded to the control output.

[0062] For example, the frequency signal can be applied to the control input 4 depending on specific characteristics of the connected DC voltage load, in particular a load characteristic or tripping characteristic. As already explained above, the predetermined functional relationship can be stored in the electronic fuse in the form of at least one conversion function, wherein the conversion function in particular comprises at least a component proportional to a respective applied frequency signal. Additionally or alternatively, the applied frequency signal can, for example, be proportional to the reference value, so that the reference value is set to a temporally constant power limit value by means of the frequency signal if the frequency signal is temporally constant, such as, for example,illustrated in Figure 3a, and is set by means of the frequency signal to a time-dependent power limit value, in particular a stepwise or abruptly changeable power limit value, if the frequency signal is time-dependent, as illustrated for example in Figure 3b.

[0063] As an alternative to the embodiment described immediately above, the reference value can also be stored in advance in the electronic fuse in the form of a characteristic curve. The applied frequency signal can, in particular, be proportional to a time-constant value to be added to the characteristic curve, so that the power limit is set based on a characteristic curve shifted by the time-constant value. This is illustrated, for example, in Figure 3c.Alternatively or additionally, the reference value can be set to a different power limit value by means of the received frequency signal depending on the direction of energy flow through the electronic fuse, in particular by mirroring the characteristic curve stored in the electronic fuse, or a characteristic curve shifted by a constant value, in the case of an energy flow direction from the output terminal to the input terminal of the electronic fuse depending on the applied frequency signal on the x-axis and setting the power limit value based on the correspondingly mirrored characteristic curve, as illustrated by way of example in Figure 3d.

[0064] Figure 5 shows a diagram of the time course of the method for operating an electronic fuse according to one embodiment of the invention. In Figure 5, the time course shown at the very top represents the frequency signals with amplitude A(t) received at the control input of the electronic fuse over time t. The second time course in Figure 5, viewed from top to bottom, relates to the voltage Uout provided at the output terminal of the electronic fuse. The third time course in Figure 5, viewed from top to bottom, represents the power limit value set using the received frequency signals in the form of a thick solid line and the power value Pb(t) calculated in the form of a dashed-dotted line over time t.The lowest time profile in Figure 5 shows the second frequency signal provided at the control output of the electronic fuse, corresponding to the calculated power Pb(t), which can be received by a control device of a power monitoring system in order to detect the calculated power therefrom.

[0065] According to the embodiment of Figure 5, at time t1, a frequency signal F7 is received at the control input of the electronic fuse, by means of which at time t2, based on a predetermined functional relationship, e.g., according to one of the examples described with reference to Figures 3a to 3d, a corresponding reference value defining a power limit value PGT (F7) is set. At time t2, a voltage U out is provided at the output terminal of the electronic fuse. Using the control and evaluation device, a power value Pb(t) is calculated from the respectively recorded voltage and current measured values ​​and compared with the power limit value P& (F7). Furthermore, a frequency signal Flout corresponding to the calculated power Pb(t) is provided at the control output of the electronic fuse. Between times t2 and t3, a frequency signal F8 different from the frequency signal F7 is received at the control input of the electronic fuse. Using the frequency signal F8, a new corresponding power limit value P& (F8) is set at time t3 based on the predetermined functional relationship.With a slight time delay, during the calculation of the respective power Pb, which is particularly continuous, a larger power value Pb is determined from the correspondingly recorded voltage and current measurements, which lies below the new power limit PGT (F8). A new frequency signal F2 is applied to the control output of the electronic fuse. 0U t, which corresponds to the newly calculated power value Pb. At time U, during the comparison of the calculated power Pb(t4) with the currently available power limit P& (F8), it is determined that the calculated power Pb(t4) is greater than the power limit P& (F8) and is therefore in a range that is not permissible for the operation of the DC load connected to the electronic fuse. A frequency signal F3 corresponding to the calculated power Pb(t4) 0Ut is provided at the control output of the electronic fuse. Since the calculated power Pb(t4) is within an impermissible range, the control and evaluation device, after a predetermined tripping time tA = ts - 14, switches the switching device to the non-conductive state by controlling the switching device, thus disconnecting the DC load from the DC voltage network. The provided voltage U out and the calculated power Pb thus drop to zero at time ts. After time te, the electronic fuse is reset by means of a reset signal F Reset received via its control input and put back into operation by switching the switching device into a conductive state. At time t?, the electronic fuse receives a frequency signal F7 via its control input, by means of which the control and evaluation device of the electronic fuse sets a corresponding power limit value P& (F7) based on the respective predetermined functional relationship at time ts. Likewise, at time ts, a voltage U out is provided at the output terminal of the electronic fuse and the respective measured values ​​of the voltage applied to the electronic fuse and the current flowing through the electronic fuse are recorded and the provided power Pb is calculated from these. A frequency signal Flout corresponding to the calculated power Pb is provided at the control output of the electronic fuse. The calculated power Pb is compared with the currently existing power limit value P& (F7). Since the calculated power Pb is less than the power limit value P& (F7), the electronic fuse and the DC load connected to it remain in operation, i.e. the switching device remains in a conductive state.

[0066] In summary, the present invention relates to an electronic fuse, a power monitoring system comprising the electronic fuse, and a method for operating an electronic fuse, wherein the DC load is switched off when the calculated power supplied by the electronic fuse to the DC load is greater than a power limit defined by a reference value. The invention is characterized in particular in that the reference value can be adjusted by means of a frequency signal received by the electronic fuse, which has a predetermined functional relationship to the reference value.Depending on one or more parameters of a received frequency signal, the power limit can be set using predefined discrimination criteria defined by the predetermined functional relationship in the form of an assignment rule and dynamically adapted to the current conditions, in particular the respective energy demand of the connected DC load. List of reference symbols.

[0067] 1 electronic fuse

[0068] 2 DC voltage network

[0069] 2A DC supply rail

[0070] 3 DC load

[0071] 3A load rail

[0072] 4 Control input

[0073] 5 Control output

[0074] 6, 6', 6" switching device

[0075] 7 Current measuring device

[0076] 8 Voltage measuring device

[0077] 9 Control and evaluation device

[0078] 10 Performance monitoring system

[0079] 11 Control device

[0080] 12 DC power supply

[0081] 13 Frequency generator

[0082] 14 Storage device

[0083] 15 relays

[0084] 16 switches

[0085] IN input connector

[0086] OUT output connector

[0087] X Node

[0088] PGT power limit

[0089] Pb calculated power ai first proportionality factor a.2 second proportionality factor

[0090] XI (t) characteristic curve

[0091] X2(t) characteristic curve (shifted)

[0092] X3(t) characteristic curve (mirrored) ti - ts time

[0093] Fl temporally constant frequency signal

[0094] F2(t) time-dependent frequency signal F3 time-constant frequency signal

[0095] F4 temporally constant frequency signal

[0096] F5 temporally constant frequency signal

[0097] F6 temporally constant frequency signal

[0098] F7, F8 frequency signal

[0099] F l out second frequency signal

[0100] F20ut second frequency signal

[0101] F30ut second frequency signal

[0102] AP, PI time-constant value

[0103] Dl readout function

[0104] B Current detection

[0105] C Voltage detection

[0106] D Performance calculation

[0107] E Compare

[0108] FEI first edge detection

[0109] FE2 second edge detection

[0110] Gl frequency-to-digital conversion

[0111] G2 Digital Frequency Conversion

[0112] H LTD link

Claims

Patent claims 1. Electronic fuse (1) for protecting a DC load (3) arranged in a DC voltage network (2), comprising: - an input terminal (IN) designed for electrical connection to a DC voltage network (2), - an output terminal (OUT) designed for electrically connecting a DC load (3), - a control input (4), - a controllable switching device (6, 6', 6") arranged between the input terminal (IN) and the output terminal (OUT), - a current measuring device (7) designed to detect a current flowing through the electronic fuse (1), - a voltage measuring device (8) which is designed to detect a voltage applied to the electronic fuse (1), and - a control and evaluation device (9) which is electrically connected to the current measuring device (7), the voltage measuring device (8) and the control input (4) and is designed to calculate a power on the basis of a current detected by the current measuring device (7) and a voltage detected by the voltage measuring device (8) and to compare the calculated power with a reference value which defines a power limit value (P&), in particular to compare it continuously or at predetermined time intervals, and in the case of a calculated power which is greater than the power limit value (P&), to cause the switching device (6, 6', 6") to disconnect a connected DC voltage load (3) from the DC voltage network (2), wherein the electronic fuse (1) is designed to output, via its control input (4), a frequency signal (F1, F2(t), F3, F4, F5,F6), by means of which the reference value can be set.

2. Electronic fuse (1) according to claim 1, wherein in the electronic fuse (1) at least one element defining the predetermined functional relationship Conversion function is stored and the control and evaluation device (9) is designed to set the reference value based on the at least one conversion function by means of a received frequency signal (Fl, F2(t), F3, F4, F5, F6), wherein the at least one conversion function in particular comprises a component which is proportional to a received frequency signal (Fl, F2(t), F3, F4, F5, F6).

3. Electronic fuse according to claim 1, wherein an assignment rule defining the predetermined functional relationship is stored in the electronic fuse (1) in the form of at least one table, and the at least one table has, in particular, a list with individual frequency signals or individual frequency signal ranges and individual power limit values ​​(PGT) included therein, wherein each frequency signal or each frequency signal range is assigned exactly one power limit value (P&) to be set.

4. Electronic fuse (1) according to claim 1 or 2, wherein the predetermined functional relationship is a proportional relationship, a first proportionality factor (ai) defining the proportional relationship is stored in the electronic fuse (1), and the control and evaluation device (9) is configured to set the reference value to a time-constant power limit value (P&) in the case of a received time-constant frequency signal (F1) based on the first proportionality factor (ai), and / or a second proportionality factor (θ12) defining the proportional relationship is stored in the electronic fuse (1), and the control and evaluation device (9) is configured to set the reference value to a time-dependent power limit value (Por(t)) in the case of a received time-dependent frequency signal (F2(t)) based on the second proportionality factor (θ12),wherein the power limit value (PGr(t)) can be changed over time, in particular stepwise or abruptly, by means of the received time-dependent frequency signal (F2(t)).

5. Electronic fuse (1) according to claim 1 or 2, wherein the reference value is stored in advance in the electronic fuse (1) in the form of a characteristic curve (XI (t)) and the control and evaluation device (9) is designed to shift the characteristic curve (XI (t)) as a function of a received temporally constant frequency signal (F4) by a temporally constant value (AP) proportional to the received frequency signal (F4) and to set the power limit value (P&) based on the characteristic curve (X2 (t)) shifted by the temporally constant value (AP).

6. Electronic fuse (1) according to claim 1, 2 or 5, wherein the reference value is stored in advance in the electronic fuse (1) in the form of a characteristic curve (X1(t)) and the control and evaluation device (9) is configured to set the reference value by means of a received frequency signal (F5, F6) as a function of the direction of energy flow through the electronic fuse (1) to a respectively different power limit value (P&), in particular in such a way that, with an energy flow direction from the output terminal (OUT) to the input terminal (IN) of the electronic fuse (1), it mirrors the characteristic curve (X1(t)) stored in the electronic fuse (1) or a characteristic curve (X2(t)) shifted by the time-constant value according to claim 5 as a function of the received frequency signal (F5, F6) on the x-axis and sets the power limit value (P&) based on the correspondingly mirrored characteristic curve (X3(t)).

7. Electronic fuse (1) according to one of claims 1 to 6, wherein the voltage measuring device (7) is arranged to detect the voltage along a voltage measuring path and the current measuring device (8) is arranged to detect the current along a current measuring path and the voltage measuring path and the current measuring path are connected together to a node (X).

8. Power monitoring system (10) comprising an electronic fuse (1) according to one of claims 1-7 and a control device (11), in particular a programmable logic controller, wherein the electronic fuse (1) further comprises a control output (5) electrically connected to the control and evaluation device (9) and the Control device (11) is electrically connected to the control input (4) and the control output (5) of the electronic fuse (1), wherein the control device (11) is designed to receive data, in particular data relating to a detected voltage, a detected current and a calculated power, from the electronic fuse (1) via the control output (5) and to transmit data and command signals, in particular a frequency signal (F1, F2(t), F3, F4, F5, F6) for setting a reference value, to the electronic fuse (1) via the control input (4).

9. Power monitoring system (10) according to claim 8, wherein the control device (11) comprises a frequency generator (13) and is configured to generate a first frequency signal (Fl, F2(t), F3, F4, F5, F6) for setting the reference value by means of the frequency generator (13) and to transmit this to the electronic fuse (1), wherein the control device (11) in particular comprises a memory device (14) with program logic stored therein for switching a DC voltage load (3) connected to the electronic fuse (1) on and off and with characteristic data of the DC voltage load (3) stored therein, in particular a load characteristic curve, and is configured in particular to control the frequency generator (13) to generate the first frequency signal (Fl, F2(t), F3, F4, F5, F6) based on the information stored in the memory device (14).

10. Power monitoring system (10) according to claim 8 or 9, wherein the electronic fuse (1) is designed to provide a second frequency signal corresponding to the calculated power at the control output (5), and the control device (11) is designed to receive the provided second frequency signal and to detect the calculated power therefrom.

11. The power monitoring system (10) according to any one of claims 8 to 10, wherein the control device (11) is further configured to transmit a reset signal for resetting the electronic fuse (1) in the event of a fault event of the electronic fuse (1).

12. Method for operating an electronic fuse, in particular an electronic fuse (1) according to one of claims 1-7, in a DC voltage network (2), comprising the steps: - electrical connection of the electronic fuse (1) to the DC voltage network (2), - electrical connection of a DC load (3) to the electronic fuse (1), - applying a frequency signal (Fl, F2(t), F3, F4, F5, F6) to a control input (4) of the electronic fuse (1), - detecting a current (B) flowing through the electronic fuse (1), - detecting a voltage (C) applied to the electronic fuse (1), - Calculating a power provided by the electronic fuse (1) based on the detected current and the detected voltage (D), - comparing the calculated power with a reference value (E) defining a power limit (P&), the reference value being set by means of the applied frequency signal having a predetermined functional relationship to the reference value, - in case of a calculated power greater than the power limit (P&), disconnecting the DC load (3) from the DC network (2).

13. The method according to claim 12, wherein the frequency signal (Fl, F2(t), F3, F4, F5, F6) is applied as a function of specific characteristics of the connected DC voltage load (3), in particular a load characteristic curve, and the predetermined functional relationship is stored in the form of at least one conversion function in the electronic fuse (1), wherein the conversion function in particular comprises at least one component proportional to a respectively applied frequency signal (Fl, F2(t), F3, F4, F5, F6).

14. Method according to claim 12 or 13, wherein the applied frequency signal (Fl, F2(t)) is proportional to the reference value, so that the reference value is set to a time-constant power limit value (P&) by means of the frequency signal (Fl) is set to a time-dependent power limit value (P&), in particular a stepwise or abruptly changeable power limit value (PGT), by means of the frequency signal (F2(t)), if the frequency signal (F2(t)) is time-dependent.

15. Method according to claim 12 or 13, wherein the reference value is stored in advance in the electronic fuse in the form of a characteristic curve (Xl(t)) and the applied frequency signal is proportional to a time-constant value (AP) to be added to the characteristic curve (XI(t)), so that the power limit value (P&) is based on a characteristic curve shifted by the time-constant value (AP) (X2(t)) is set.

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