Discreetly constructed overcurrent protection device, corresponding control unit and motor vehicle with it

Abstract

The invention relates to an overcurrent protection device (4) constructed with a discrete circuit. In this device, a measuring resistor and a main path transistor (T1) for switching the interruption of the main current path are arranged in a main current path. The discrete circuit also includes a comparator circuit for comparing a voltage drop (USh1-USh2) across the measuring resistor (RM) with a predetermined voltage threshold by means of a first comparator (K1). An output of the first comparator (K1) is connected to the main path transistor (T1) to switch it off when the voltage threshold is exceeded.The comparator circuit is also configured as a memory circuit for a detected overcurrent condition and, upon exceeding the voltage threshold, applies a voltage signal above the voltage threshold to a measuring input of the first comparator (K1), regardless of whether the overcurrent condition continues, thus keeping the main path transistor (T1) switched off. The invention also relates to a control unit (4) with such an overcurrent protection device (4) and a motor vehicle (1) equipped therewith.

Description

[0001] The present invention relates to an overcurrent protection device and a corresponding control unit, in particular for a motor vehicle. The invention also relates to a motor vehicle equipped therewith.

[0002] Electrical and electronic components are used in numerous applications and for a wide variety of devices and functions today. At the same time, increasingly stringent safety requirements are being placed on them. For example, overloading of components or parts must be prevented and / or a high level of functional safety must be achieved. This should also be achieved at the lowest possible cost. However, existing approaches or components for such safeguards are often expensive and cannot be qualified for high levels of functional safety, such as ASIL D, without further measures or additional effort. Therefore, there is still a need for corresponding improvements.

[0003] For example, CN 221 652 232 U deals with an overcurrent protection circuit with an output control circuit and a self-locking overcurrent protection circuit connected in series, the latter also being connected to a reset circuit and a monitoring circuit.

[0004] DE 40 00 820 A1 describes a circuit arrangement for switching an electrical load on and off. The circuit arrangement comprises a controllable switching element whose control terminal is connected to a drive circuit and through which the load current flows. Furthermore, the circuit arrangement includes a detector circuit that switches off the load in the event of a fault when a limit value of the load current is exceeded. The control terminal, or a signal corresponding to the control terminal signal, and a terminal of the switching element leading to the load are each connected to the input of a driver, which, in the event of a fault, controls a switching element that interrupts the load current circuit.

[0005] DE 102018 209 681 A1 describes a self-holding comparator circuit comprising an input, a comparator, and a transistor circuit arranged between the supply voltage, ground, and the comparator output. The transistor circuit is connected to at least one comparator input in such a way that, when the comparator output is activated, the level of the inverting comparator input is lowered and / or the level of the non-inverting comparator input is raised, regardless of the at least one input.

[0006] German patent application DE 10 2016 114 740 B3 describes an electronic fuse for an electrical load in the electrical system of a motor vehicle. The electronic fuse comprises an input-side shunt resistor and a controllable switching element. The controllable switching element is coupled on its input side to an output of the shunt resistor, which is coupled on its output side to an output of the electronic fuse that can be connected to the electrical load, and which has a control input. Furthermore, the electronic fuse includes a voltage detector configured to provide a control signal to the control input for switching off the electrical load when the voltage drop across the shunt resistor exceeds a threshold value. Additionally, a hold-open element is provided, which is coupled to the voltage detector and configured to hold the control signal in a switch-off state when the controllable switching element has switched off the electrical load.

[0007] EP 2 720 053 A2 describes a fail-safe connection with several semiconductor switches of different sizes, connected in series between a power source and a load. The connection also includes a built-in test circuit for detecting an overvoltage condition across at least one of the sizes. The test circuit opens or closes this size according to a voltage measured across at least one of the semiconductor switches.

[0008] German patent application DE 10 2021 130 379 A1 addresses the problem that, with the increasing use of autonomous vehicles and drive-by-wire control systems in motor vehicles, high reliability of motion-related systems is crucial, but it is not practical to bring the large number of existing legacy systems up to the required level of robustness. Against this background, the patent describes an electrical vehicle system that provides power from two DC power sources, each connected to a separate group of integrity-protected (ASIL) loads. A third group of non-ASIL loads is connected to both power sources via a controllable isolator with a first and second transistor array. The connection through the isolator also links each ASIL group to the other DC power source.A control circuit contains a multitude of drivers for controlling the transistor arrays. This control circuit is configured to terminate the control of at least one of the transistor arrays when a fault condition is detected in which the current flow in at least one of the transistor arrays exceeds a threshold value.

[0009] One potential problem against which protection is often desired is overcurrents, i.e., currents that are undesirably or faultily so large that they can lead to problems, damage, or overloads. CN 107 528 297 A describes an overcurrent protection circuit for this purpose. In this circuit, a voltage measured across a shunt is amplified and applied an additional predetermined offset voltage. The output of a corresponding amplifier is then compared to a predetermined reference voltage, which is higher than the offset voltage, to output a current-sensing signal if the amplifier's output voltage is greater than the reference voltage.A circuit for detecting amplifier failure compares the amplifier's output voltage with a predetermined second reference voltage that is greater than zero and less than the offset voltage in order to output a corresponding signal that may indicate a failure of the amplifier.

[0010] As a further example, KR 2019 0 017 298 A describes a power converter unit with a multitude of switches for performing voltage conversion in both directions between a low-voltage battery and a high-voltage battery. In this unit, the current flowing into the power converter unit is compared with a reference current to determine whether an overcurrent has occurred. If so, all switches are closed and the current flow is blocked. If not all switches of the power converter unit have closed in response to an overcurrent, a corresponding protective circuit stops the operation of the entire power converter unit.

[0011] Despite these approaches, there remains a need for cost-effective protective devices for various situations and requirements.

[0012] The object of the present invention is to realize a cost-effective overcurrent protection system with which a high level of functional safety can be achieved.

[0013] This problem is solved by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the dependent claims, the description, and the figures. Features, advantages, and possible embodiments set forth in the description for one of the subject matter of the independent claims are to be regarded, at least analogously, as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.

[0014] The overcurrent protection device according to the invention can be arranged between a DC voltage source and a load to be supplied electrically, i.e., with DC voltage or DC current. Such a load can be a functional device, such as a control unit, a microcontroller, an inverter, or the like. The overcurrent protection device according to the invention comprises a discrete circuit with an input for connecting the voltage source, an output for connecting the load, and a main current path running from the input to the output. The discrete circuit includes an input-side voltmeter for measuring or monitoring a voltage drop across a shunt, i.e., a measuring resistor, arranged in the main current path. Thus, a current flowing in the main current path can be monitored. The discrete circuit also includes an output from the voltmeter.The transistor, referred to here as the main path transistor, is located in the main current path and measures the measuring resistor. This main path transistor allows the main current path to be switched or controllably interrupted. In other words, the main path transistor can be switched off to interrupt the main current path and switched on to remove the interruption, thus allowing current to flow along the main current path from the input to the output.

[0015] The discrete circuit also includes a comparator circuit arranged outside the main current path or in parallel to the main current path for comparing—directly or indirectly—the voltage drop measured across the measuring resistor with a predefined voltage threshold. The voltage threshold can be set or predefined, for example, by means of appropriate discrete resistors, such as a voltage divider supplied with an input voltage. The voltage drop measured in the main current path, or a corresponding voltage signal, can thus be applied to a measuring input of the comparator circuit, or to the first comparator of the comparator circuit. The use of a voltage signal corresponding to the measured voltage drop...Indirectly comparing the measured voltage drop with the voltage threshold can, for example, mean that the measured voltage drop is first amplified. A voltage corresponding to the voltage threshold, i.e., a corresponding voltage signal, can be applied to another input, which is referred to here as the reference input of the comparator circuit or the first comparator of the comparator circuit. The respective comparison result can then be present at an output of the first comparator – depending on the ratio of the measured voltage drop or the corresponding voltage signal to the voltage threshold, for example, in the form of a high signal or high voltage level, or a low signal or low voltage level, i.e., a relatively high or a relatively low voltage.

[0016] According to the invention, in the discrete circuit, a voltage signal corresponding to the voltage drop measured in the main current path or across the measuring resistor is applied to the measuring input of the first comparator of the comparator circuit. The output of the first comparator, for example, a corresponding intermediate output of the comparator circuit, is connected to the main path transistor in order to switch it off when the voltage threshold is exceeded, thereby interrupting the main current path. The output signal or voltage signal present at the output of the first comparator can, in particular, be applied to a gate of the main path transistor. The main path transistor can, for example, be a PMOS. Thus, when the voltage threshold is exceeded, the first comparator can output a high signal, which allows the main path transistor to be switched off.

[0017] According to the invention, the comparator circuit also functions as a memory or storage circuit for a detected overcurrent or a corresponding overcurrent state. Such an overcurrent state can exist at least when, or precisely when, an overcurrent flows in the main current path or would flow if the main current path were uninterrupted. For this purpose, upon exceeding the voltage threshold, i.e., upon a detected overcurrent or overcurrent state, the comparator circuit continuously applies a voltage above the voltage threshold—that is, a voltage signal above the voltage threshold, which can also be referred to here as a storage voltage or storage signal—to the measuring input of the first comparator, thus switching off or keeping off the main path transistor. This applies regardless of whether the overcurrent state continues to exist.This allows the measurement input of the first comparator to be continuously maintained at a voltage level that ensures the continuous interruption of the main current path. This prevents the main current path transistor from immediately switching on again after its initial off state. Therefore, continuous and thus particularly safe and reliable protection of any load connected to the output of the overcurrent protection device is guaranteed.

[0018] The fact that the comparator circuit permanently applies the voltage signal above the voltage threshold to the measurement input of the first comparator can mean that this voltage signal remains applied to the measurement input until further notice, for example, until a control or switching operation cancels it. It may therefore still be possible, for example, after successfully resolving the cause of the overcurrent condition, to permanently switch the main path transistor back to conducting, thus returning the comparator circuit to a state in which the measurement input of the first comparator is no longer subjected to, or fixed in, the voltage signal above the voltage threshold. This is described in more detail elsewhere.

[0019] In a first embodiment of the present invention, the comparator circuit also comprises a second comparator connected downstream of the first comparator and a controllable or switchable voltage divider arranged between the first and second comparator. Upon detection of a voltage threshold being exceeded, this voltage divider is switched to a state by a corresponding output signal at the output of the first comparator, which signals the threshold being exceeded. In this state, the second comparator provides an output signal that then causes the voltage signal above the voltage threshold, i.e., the storage signal or storage voltage, to be applied to the measuring input of the first comparator.By changing the output signal, i.e., the output voltage of the first comparator, upon detecting an overcurrent, a voltage signal applied to a measurement input of the second comparator can be modified. The second comparator can then compare this signal with a predefined reference voltage or signal. The reference voltage can be defined or set, for example, by another voltage divider, particularly a static one, which can be supplied with a corresponding input voltage. The output signal of the second comparator can be, but does not necessarily have to be, the voltage signal above the threshold, which is then applied to the measurement input of the first comparator.The embodiment of the present invention proposed here represents a simple, cost-effective and practical way to implement the storage functionality of the comparator circuit within the framework of the discrete circuit.

[0020] Additionally or alternatively, in a second embodiment of the present invention, the overcurrent protection device, and in particular its discrete circuitry, also includes a control device for the controlled switching of the main path transistor. The control device can thus be configured to switch the main current path back and forth between a conducting and a blocked state in a controlled manner. For example, the control device can be a microcontroller or include a microcontroller. The control device can enable the main current path to be permanently switched back to conducting after a detected overcurrent. Since this can be done electronically, a simple and quick reset of the overcurrent protection device, and in particular also of the comparator circuit, is possible. In particular, no component, such as a conventional fuse or the like, needs to be replaced.This allows the overcurrent protection device to be used cost-effectively and flexibly. In particular, the control unit can ensure that the voltage signal exceeding the voltage threshold is no longer present at the measuring input of the first comparator. This allows the main current path or the main current path transistor to be permanently switched on again, and the comparator circuit to be ready to detect the next overcurrent or overcurrent condition.

[0021] In this second embodiment of the present invention, the control unit, or an output of the control unit, is connected to the measuring input of the first comparator via a capacitor. This enables edge-triggered switching, i.e., edge-triggered switching on and off, for activating and deactivating the overcurrent protection, i.e., blocking the main current path. The control unit can apply a rising voltage edge, i.e., a rising AC signal to block the main path transistor, and a falling voltage edge, i.e., a falling AC signal to switch the main path transistor on, to the measuring input of the first comparator via the capacitor. The falling voltage edge thus pulls the measuring input of the first comparator to a voltage level, i.e., potential, below the voltage threshold.This accordingly changes the output signal of the first comparator. According to the mechanism described elsewhere, this can then also change the output signal of the second comparator. This, in turn, can stop the continuous application of the voltage signal above the voltage threshold to the measuring input of the first comparator. Thus, the comparator circuit is reset even after the end of the falling or negative voltage edge, and—provided there is no longer an overcurrent condition—the main current path is not immediately interrupted again. The further development of the present invention proposed here can enable simple and effective controlled switching of the comparator circuit or the overcurrent protection device.

[0022] The present invention enables the cost-effective and relatively simple implementation of overcurrent monitoring, for example, protected according to ASIL D. In particular, the discrete circuit can be built using standard components, eliminating the need for an eFuse, i.e., an integrated circuit or chip functioning as an electronic fuse. Currently available eFuses of this type are comparatively expensive and generally not qualified for high functional safety levels, such as ASIL D, without additional measures. Furthermore, certain other potential requirements cannot be practically implemented with conventional eFuses, such as edge-triggered switching of the comparator circuit or the main path transistor between an activated / conducting state and a deactivated / blocking state.The overcurrent protection device according to the invention can therefore be used particularly beneficially, for example in the automotive sector, i.e. in a control unit for a motor vehicle or the like, since functional safety requirements up to ASIL D are increasingly being placed on the automotive sector and costs are always an important factor.

[0023] For the purposes of the present invention, the arrangement of a particular component between two other components or locations means that the component is electrically positioned or connected between them. A conductor or current path can then lead from one of the other components or locations to the component in question and from there to the other component or location. Therefore, the arrangement of a component between two other components or locations does not necessarily mean that the component is spatially or geometrically positioned between the other components or locations.

[0024] The terms voltage and voltage signal can, in this context, be understood as essentially synonymous.

[0025] A voltage applied to a particular point or component, or a voltage signal applied to or directed at a point or component, can, for example, be understood relative to an earth or ground potential, or have an earth or ground potential as a second voltage pole.

[0026] In a possible further development of the present invention, the discrete circuit also includes a differential amplifier for amplifying the voltage drop measured across the measuring resistor. This differential amplifier is connected between the main current path and the measuring input of the first comparator. In other words, the voltage drop measured across the measuring resistor or in the main current path can be amplified by means of the differential amplifier, and a correspondingly amplified voltage signal, corresponding to the measured voltage drop, can be fed to the measuring input of the first comparator. This allows even relatively small measured voltage drops to be used for the reliable detection of overcurrents. This means that a particularly low-resistance measuring resistor can be used, which can make the overcurrent protection device particularly efficient.Furthermore, amplifying the measured voltage drop can enable improved robustness of overcurrent detection and a simplified design of the first comparator.

[0027] In a possible embodiment of the present invention, the switchable voltage divider comprises at least a first voltage divider resistor, a second voltage divider resistor arranged in series therewith, and a voltage divider transistor. The voltage divider transistor is arranged in series with the first voltage divider resistor and in parallel with the second voltage divider resistor. The voltage divider transistor can be switched by the output signal of the first comparator in order to change the output signal, i.e., the comparison result of the second comparator. For example, the voltage divider transistor can be a PNP transistor, and the output of the first comparator can be connected to the base of the voltage divider transistor. The second comparator then compares the voltage applied to its measuring input, i.e., the voltage signal.The voltage level at a point between the first and second voltage divider resistors is determined by the predefined reference voltage applied to its reference input. Upon detection of an overcurrent, the first comparator can output a correspondingly high voltage signal, which can then switch off the voltage divider transistor. This allows the voltage between the first and second voltage divider resistors to be adjusted so that, depending on the design of the reference voltage, the second comparator, or the overall memory circuit, it falls above or below the reference voltage. Before an overcurrent is detected, the voltage divider transistor may be conducting.To avoid excessive current flow and thus energy consumption, the voltage divider transistor can be connected in series with another resistor, which can then also be connected in parallel with the second voltage divider resistor. The proposed further development of the present invention can offer a simple and effective way to implement the switchable or controllable voltage divider using discrete components, thus enabling the storage circuit, i.e., the storage functionality of the comparator circuit, to be implemented simply and with minimal effort.

[0028] In a possible embodiment of the present invention, the output of the second comparator is connected to a transistor, referred to here as a storage transistor, arranged between it and the measuring input of the first comparator. For example, this storage transistor can be a PMOS, and the output of the second comparator can then be connected to the gate of the storage transistor. At a terminal of the storage transistor opposite the measuring input, in particular the drain, the voltage signal above the voltage threshold is present, especially permanently, i.e., even before or regardless of whether an overcurrent condition is detected. The storage transistor is switched off before the occurrence or detection of an overcurrent.In an overcurrent state, i.e., in an initially fault-free state, the first comparator is blocked. It is then switched on upon detection of the overcurrent state by the corresponding output signal of the second comparator. This applies the voltage above the voltage threshold, i.e., the corresponding voltage signal, to the measurement input of the first comparator. For this purpose, the terminal of the storage circuit transistor facing the measurement input, particularly its source, can be connected to the measurement input of the first comparator. Because the storage circuit transistor is blocked in the fault-free normal state, i.e., before an overcurrent is detected, the comparator is not affected by the voltage signal above the voltage threshold, and the power consumption of the comparator circuit remains relatively low.In particular, this means that the second comparator does not necessarily need to deliver an output signal above the voltage threshold in the event of a detected overcurrent protection event. This simplifies the design of the second comparator.

[0029] In a further possible embodiment of the present invention, the overcurrent protection device, in particular its discrete circuit, also comprises a test circuit or test function for testing the functionality of the overcurrent protection device's function of interrupting the main current path in the event of an overcurrent condition, i.e., an overcurrent flowing into the main current path via the input of the overcurrent protection device. The test circuit comprises a control device, in particular the one mentioned elsewhere, a resistor, which is referred to here as the test circuit resistor, and a transistor, which is switchable by means of the control device and which is referred to here as the test circuit transistor. The test circuit resistor and the test circuit transistor are connected in series in a test circuit path.A test circuit branch is arranged, running from an output point of the main current path located at the end of the main path transistor to a ground or earth potential point. For controlled switching of the test circuit transistor between a blocked and a conducting state, a corresponding test output of the control unit can, for example, be connected to the gate of the test circuit transistor. The test circuit transistor can then be switched to conduction by the control unit to simulate a short circuit, which leads to an overcurrent in the main current path. However, current limiting can be achieved by means of the test circuit resistor. For this purpose, the test circuit resistor can be of a higher resistance than the measuring resistor. By appropriately designing the components, it can be ensured, in particular, that the test circuit can be used even at different temperatures or...Reliable testing is possible across a realistic temperature range, even under aging or time-related drift in component properties, particularly resistors, or across relevant tolerances. When the test circuit transistor is switched back to blocking mode by the control unit, the simulated short circuit is cleared and the overcurrent condition is thus terminated. Such an electronically controlled test circuit allows for a particularly high level of functional safety to be achieved in a comparatively simple and cost-effective manner.

[0030] An alternative overcurrent protection device is designed as an overcurrent protection device for arrangement between a DC voltage source and a load to be electrically supplied by it, comprising a discrete circuit with an input for connecting the DC voltage source, an output for connecting the load and a main current path running from the input to the output, wherein the discrete circuit includes an input-side voltmeter for monitoring a voltage drop across a measuring resistor arranged in the main current path, a main path transistor arranged on the output side of the measuring resistor in the main current path by means of which the main current path can be switched to interrupt it, and a Schmitt trigger circuit arranged outside the main current path for comparing the voltage drop across the measuring resistor with a predetermined voltage threshold.In the discrete circuit, a voltage measurement signal corresponding to the voltage drop across the measuring resistor is applied to a positive input of the Schmitt trigger, the output of the Schmitt trigger is connected to the main path transistor to switch it off when the predetermined voltage threshold is exceeded, and the Schmitt trigger circuit is also configured as a memory circuit for an overcurrent condition detected by exceeding the voltage threshold, and for this purpose, upon exceeding the voltage threshold, regardless of whether the overcurrent condition continues to exist, it permanently applies a voltage signal above the predetermined voltage threshold to the positive input of the Schmitt trigger, so that the main path transistor remains off.

[0031] The measuring resistor can have a low resistance. This means that the measuring resistor has little current-limiting effect and does not lead to a significant additional energy consumption of the overcurrent protection device.

[0032] The main path transistor is a transistor located on the output side of the measuring resistor, also within the main current path. This main path transistor allows the main current path to be switched or controllably interrupted. In other words, the main path transistor can be switched off to interrupt the main current path and switched on to remove the interruption, thus allowing current to flow along the main current path from the input to the output.

[0033] The Schmitt trigger circuit, located outside the main current path, serves to compare—directly or indirectly—the monitored (i.e., measured) voltage drop across the measuring resistor with a predefined voltage threshold, i.e., a predetermined voltage threshold value or reference voltage. The voltage threshold can be set or defined, for example, using appropriate discrete resistors, such as a voltage divider. For instance, a voltage signal corresponding to the measured voltage drop can be applied to a positive input of a Schmitt trigger in the circuit, and a voltage signal corresponding to the predefined voltage threshold can be applied to the negative input of the Schmitt trigger.An indirect comparison of the voltage drop measured across the measuring resistor with the voltage threshold can mean, for example, that not a voltage signal directly corresponding to the measured voltage drop, but rather a corresponding voltage signal, or one generated from it (e.g., by amplification), is applied to the positive input of the Schmitt trigger. The voltage signal corresponding to the measured voltage drop can also be referred to as the voltage measurement signal. A voltage signal corresponding to each comparison result can then be present at the output of the Schmitt trigger.

[0034] The discrete circuit of the overcurrent protection device is configured to output a voltage measurement signal, corresponding to the voltage drop measured across the measuring resistor, to the positive input of the Schmitt trigger. The output of the Schmitt trigger is connected to the main path transistor. Since the voltage signal at the output of the Schmitt trigger depends on the comparison result, the main path transistor can be switched off when the voltage measurement signal exceeds or is greater than the predefined voltage threshold. The voltage signal at the output of the Schmitt trigger can therefore also be referred to as the trigger voltage signal. The main path transistor can, for example, be a PMOS (P-channel MOSFET), in which case the output of the Schmitt trigger can be connected to the gate, i.e., the gate electrode, of the main path transistor.

[0035] As soon as the voltage measurement signal falls below the predefined voltage threshold, the trigger voltage signal at the output of the Schmitt trigger would also switch, for example from high to low, immediately switching the main path transistor back on. If a problem or overcurrent condition that initially led to the main path transistor being switched off is still unresolved or present, this could result in unwanted switching of the main path transistor back and forth. To prevent this, the Schmitt trigger circuit is also configured as a memory circuit for an overcurrent condition detected by exceeding the voltage threshold. For this purpose, the Schmitt trigger circuit...The discrete circuit, upon exceeding the voltage threshold, continuously applies a voltage signal above the predefined voltage threshold—that is, a corresponding voltage level—to the positive input of the Schmitt trigger, thus keeping the main path transistor switched off. This voltage signal above the predefined voltage threshold can also be referred to as the storage voltage signal. To apply this storage voltage signal to the positive input of the Schmitt trigger upon exceeding the voltage threshold, the Schmitt trigger circuit, or the discrete circuit, can, for example, include a suitably configured (i.e., dimensioned and arranged) voltage divider connected to the positive input of the Schmitt trigger. This is described in more detail elsewhere.

[0036] An overcurrent condition can exist at least when, or precisely when, an overcurrent flows in the main current path, or would flow if the main current path were uninterrupted. An overcurrent can be a current greater than a specified maximum permissible current. Its magnitude can depend on the specific application, for example, the load connected to the overcurrent protection device. Prolonged or continuous flow of such an overcurrent could, for instance, lead to damage to at least one component of the connected load. This can be reliably prevented by the memory function of the discrete circuit or the Schmitt trigger circuit. Thus, continuous and particularly safe and reliable protection of the load connected to the output of the overcurrent protection device can be enabled or ensured. Furthermore, the overcurrent protection device can be designed to be particularly cost-effective.This can have a significant impact, especially when the overcurrent protection device is used in series production, for example in the mass production of motor vehicles.

[0037] The discrete circuit or overcurrent protection device can be built using standard components, eliminating the need for an e-fuse (an integrated circuit or chip functioning as an electronic fuse). Currently available e-fuses are relatively expensive and generally not qualified for high functional safety levels, such as ASIL D, without further modifications. Furthermore, certain other potential requirements cannot be practically implemented with conventional e-fuses, such as edge-triggered switching of the Schmitt trigger circuit or the main path transistor between an activated (conducting) state and a deactivated (blocked) state, whereas this is possible with the present circuit.

[0038] To allow the load to be supplied from the voltage source again via the overcurrent protection device after the voltage threshold has been exceeded and the responsible overcurrent condition has been rectified, the device can be configured to selectively disconnect the storage voltage signal at the positive input of the Schmitt trigger. This is described in more detail elsewhere.

[0039] In a possible further embodiment of the present alternative overcurrent protection device, the discrete circuit includes a voltage divider, which serves to set or provide the specified voltage threshold and is therefore also referred to here as a reference voltage divider. This reference voltage divider comprises two resistors connected in series, which are referred to here as threshold resistors. A point located between these two threshold resistors is connected to the negative input of the Schmitt trigger. In other words, a signal or voltage tap is located on an electrical line between the two threshold resistors, which applies the voltage present there to the negative input of the Schmitt trigger.Such a voltage divider consisting of two simple resistors can, by appropriately dimensioning the resistors, set or provide the specified voltage threshold and can be constructed in a particularly simple and cost-effective manner.

[0040] In a possible further development of the existing alternative overcurrent protection device, a voltage signal applied to the input of the overcurrent protection device, i.e., a specific input voltage, is applied to the input of the reference voltage divider. One output of the reference voltage divider is connected to a ground point. The voltage signal applied to the input of the overcurrent protection device, i.e., the input voltage, can be, in particular, the voltage immediately before the measuring resistor. The predefined voltage threshold can be generated from the input voltage using the reference voltage divider. For this purpose, the two threshold resistors are connected in series between the input of the overcurrent protection device and the ground point. This design eliminates the need for a separate voltage source to provide the predefined voltage threshold.This allows the overcurrent protection device to be designed in a particularly simple and cost-effective, yet effective and efficient manner.

[0041] In another possible embodiment of the present alternative overcurrent protection device, the discrete circuit, or Schmitt trigger circuit, includes a voltage divider connected to the positive input of the Schmitt trigger. This voltage divider can be constructed using an arrangement of several resistors. Specifically, the voltage divider here comprises two resistors connected in series with the positive input of the Schmitt trigger, referred to as series resistors, and an additional resistor. This additional resistor is located in a current path leading from the positive input of the Schmitt trigger to its output. Accordingly, this additional resistor is, in a sense, connected in parallel with the Schmitt trigger and is therefore also referred to here as a parallel resistor. The Schmitt trigger functionality of the Schmitt trigger circuit is realized primarily through this parallel resistor.The two series resistors become particularly relevant when an overcurrent occurs or is measured. A voltage signal corresponding to the voltage drop measured across the measuring resistor can be applied to one input of the voltage divider, i.e., to a point before the two series resistors opposite the positive input of the Schmitt trigger. When an overcurrent occurs or is measured, the output of the Schmitt trigger, or the Schmitt trigger circuit, goes high, i.e., to a high voltage level, which switches off the main path transistor. The input of the voltage divider then goes low, i.e., to a low voltage level, because the current flow in the main current path is interrupted. The voltage divider then consists of the two series resistors and the parallel resistor, so that the positive input of the Schmitt trigger is at a higher voltage level.The voltage level remains at the negative input of the Schmitt trigger, i.e., at the specified voltage threshold. Using the voltage divider proposed here, a voltage above the specified voltage threshold can be maintained at the positive input of the Schmitt trigger immediately after the main path transistor is switched off by a corresponding trigger voltage signal. Otherwise, switching off the main path transistor would prevent current from flowing through the main current path, so no voltage drop would be measured across the measuring resistor. This would result in a voltage level below the specified voltage threshold at the positive input of the Schmitt trigger. Consequently, the output of the Schmitt trigger, i.e., the trigger voltage signal, would be switched to low, thus activating (unblocking) the main path transistor.The voltage divider proposed here can therefore be used to implement the overcurrent storage function. This is particularly simple and cost-effective in this case.

[0042] In another possible embodiment of the present alternative overcurrent protection device, the discrete circuit includes a differential amplifier for amplifying the voltage drop measured across the measuring resistor. For this purpose, a first measuring voltage tap, located in or branching off from the measuring resistor on the input side of the main current path, can be connected to a first input of the differential amplifier. A second measuring voltage tap, located in or branching off from the main current path between the measuring resistor and the main path transistor, can be connected to the second input of the differential amplifier. The output of the differential amplifier can be connected, at least indirectly, to the positive input of the Schmitt trigger. In particular, the series resistors mentioned elsewhere can be arranged between the output of the differential amplifier and the positive input of the Schmitt trigger.Using the differential amplifier proposed here, the voltage drop measured across the measuring resistor or in the main current path can be amplified, and a correspondingly amplified voltage signal—the voltage measurement signal—can be fed to the positive input of the Schmitt trigger. This allows even relatively small measured voltage drops to be used for the reliable detection of overcurrents. Consequently, a particularly low-resistance measuring resistor can be used, making the overcurrent protection device especially efficient. Furthermore, amplifying the measured voltage drop with the differential amplifier improves the robustness of the overcurrent detection and simplifies the design of the Schmitt trigger.

[0043] In another possible embodiment of the present alternative overcurrent protection device, the overcurrent protection device also includes a control unit for the controlled switching of the main path transistor, at least indirectly. The control unit can therefore be configured to switch the main path transistor back to conducting after it has been switched off by a corresponding trigger voltage signal—contrary to its storage function—or to switch the main current transistor back and forth between a conducting and a blocked state in a controlled manner. For example, the control unit can be, or include, a suitably configured microcontroller. The control unit can enable the main current transistor or the main current path to be permanently switched back to conducting after a detected overcurrent or overcurrent condition.Since this can be done electronically, a simple and quick reset of the overcurrent protection device, and especially of the Schmitt trigger circuit and its memory function, is possible. In particular, no component, such as a conventional fuse, needs to be replaced. This allows for cost-effective and flexible use of the overcurrent protection device. Specifically, the control unit can ensure that the memory voltage signal, which is above the predefined voltage threshold, is no longer present at the positive input of the Schmitt trigger. This allows the output of the Schmitt trigger to be pulled low, which in turn switches the main path transistor to conduct. The discrete circuit, or overcurrent protection device, is then ready to detect the next overcurrent or overcurrent condition.

[0044] In a possible further development of the present alternative overcurrent protection device, an output of the control unit is connected to a point between the two series resistors of the voltage divider described elsewhere, which is connected to the positive input of the Schmitt trigger. As a further component of the discrete circuit, a capacitor is arranged beyond this point, between it and a ground potential point. Using the control unit, a negative or falling voltage signal can then be generated at a corresponding output of the control unit. In particular, the point located between the two series resistors, to which the output of the control unit is at least indirectly connected, can thus be pulled to ground potential or to 0 V.The voltage divider connected to the input of the Schmitt trigger is then formed, if necessary, only by the series resistor located closer to the positive input of the Schmitt trigger and the parallel resistor. As a result, the voltage level at the positive input of the Schmitt trigger changes, specifically falling below the predefined voltage threshold, i.e., the voltage level at the negative input of the Schmitt trigger. This also changes the voltage signal at the output of the Schmitt trigger accordingly, and the main path transistor is switched on again.

[0045] The control unit can then be deactivated, for example, to save energy and allow for renewed overcurrent detection by the discrete circuit, or for the main path transistor to be switched off. Similarly, a positive or rising voltage signal can be generated at the output of the control unit if needed. This allows the voltage level at the positive input of the Schmitt trigger to be raised above the predefined voltage threshold, thereby switching off the main path transistor. This allows the output of the overcurrent protection device, and thus any connected load, to be de-energized or disconnected from current without the need for additional devices, switches, or similar components.This ensures, for example, that the area is safe from contact, thus enabling a correspondingly simple and safe exchange of the load or the like.

[0046] In a possible further development of the existing alternative overcurrent protection device, a capacitor is connected between the output of the control unit and the point between the two series resistors. This enables edge-triggering, i.e., an edge-triggered switching function for activating and deactivating the overcurrent protection, i.e., blocking the main path transistor. The control unit can, via the edge-trigger capacitor, apply, for example, a falling voltage edge (i.e., a falling AC signal) to the positive input of the Schmitt trigger to unlock the main path transistor, thus causing it to switch on. The falling voltage edge can therefore pull the positive input of the Schmitt trigger to a voltage level (potential) below the specified voltage threshold.As described elsewhere, this changes the trigger voltage signal at the output of the Schmitt trigger, thereby switching the main path transistor into conduction. Thus, the discrete circuit or overcurrent protection device is reset even after the end of the falling or negative voltage edge, and—provided there is no longer an overcurrent condition—the transistor is not immediately switched off again, i.e., the main current path is not interrupted.

[0047] Conversely, applying a positive voltage level to the output of the control device can, if necessary, cause a rising or positive voltage edge to pass through the edge-trigger capacitor. This allows the positive input of the Schmitt trigger to be pulled above the predefined voltage threshold, thereby ultimately switching off the main path transistor. This state can then be maintained by the memory circuit or memory function described elsewhere, for example, until a falling or negative voltage edge is generated by the control device and applied to the positive input of the Schmitt trigger to switch the main path transistor back on.The edge-trigger transistor proposed here, i.e., the corresponding edge control of the overcurrent protection device, enables simple, effective, and particularly efficient controlled switching of the overcurrent protection device.

[0048] In another possible embodiment of the present alternative overcurrent protection device, the device also includes a test circuit or test function for testing the functionality of the overcurrent protection device's function of interrupting the main current path in the event of an overcurrent condition. The test circuit comprises a control unit and a test circuit path or test circuit branch. The control unit can, in particular, be the control unit for controlled switching of the main path transistor mentioned elsewhere. The test circuit path branches off from the main current path at the output side of the main path transistor and leads to a ground potential point.The test circuit path includes a current-limiting resistor, referred to here as the test circuit resistor, and, between this resistor and ground, a transistor, referred to here as the test circuit transistor, which can be switched by the control unit. In other words, an output of the control unit, referred to here as the test output, is connected to the test circuit transistor, specifically to its gate. The test circuit transistor can, for example, be an NMOS (N-channel MOSFET).

[0049] In a normal or continuous operating state of the overcurrent protection device, the control unit or its test output can be deactivated, and the test circuit transistor can be blocked. This avoids or minimizes additional current or energy consumption by the overcurrent protection device due to the test circuit. The control unit can be configured to switch the test circuit transistor on by means of a corresponding voltage signal or voltage level at the test output to test the overcurrent protection function of the device. This can cause a sufficiently large current flow in the main current path, which should be detected by the overcurrent protection device as an overcurrent. If this occurs, the main path transistor can then be blocked, as described elsewhere, thus interrupting the current flowing through the test circuit path. This can be detected if necessary.The control unit can, for example, then or after a predetermined time period deactivate the test output or block the test circuit transistor. If the test circuit transistor is blocked again by the control unit, the simulated short circuit can be cleared and the overcurrent condition thus terminated. The control unit can also be configured to output or display a corresponding test result signal depending on the respective test result, i.e., depending on whether the main current path has been interrupted as intended or not.

[0050] By switching the test circuit transistor to conduct, a short circuit can be simulated, while the test circuit resistor can be used to limit the current and prevent damage. For this purpose, the test circuit resistor can be of a higher resistance than the measuring resistor.

[0051] By appropriately designing the components or parts, it can be ensured that reliable testing is possible using the test circuit even at different temperatures or over a temperature range realistic in the respective application, as well as in the event of aging or drift in the properties of the components or parts over time, especially the resistors, or across corresponding tolerances.

[0052] The electronically controlled test circuit proposed here allows a particularly high level of functional safety to be achieved in a comparatively simple and cost-effective manner.

[0053] The present invention also relates to a control unit, which is intended for use in a motor vehicle. The control unit, as intended, comprises the overcurrent protection device according to the invention. For example, the control unit can be configured to control a function or feature of a motor vehicle, such as an inverter or the like. This can represent a particularly useful application, since the automotive sector demands both high safety standards and consistently strives for cost-effectiveness. Depending on the specific purpose or application, the control unit can include further components, such as a control circuit or control logic.Control electronics, a data processing device, for example with a process device such as a microchip or microprocessor or microcontroller or the like, and a computer-readable data storage device coupled thereto, and / or the like.

[0054] The present invention also relates to a motor vehicle equipped with the control unit according to the invention for controlling at least one device or function of the motor vehicle. The motor vehicle according to the invention can, in particular, be the motor vehicle mentioned in connection with the overcurrent protection device according to the invention and / or in connection with the control unit according to the invention, or correspond to it.

[0055] Further features of the invention may become apparent from the following description of the figures and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0056] Specific details are explained below with reference to the figures. They show: Fig. 1 a schematic representation of a motor vehicle with a control unit with an overcurrent protection device according to an exemplary embodiment; Fig. 2 a schematic representation of a motor vehicle with a control unit having an overcurrent protection device according to an alternative, unclaimed embodiment.

[0057] Fig. Figure 1 shows a partial schematic representation of a motor vehicle 1, which has a battery 2 for supplying electrical power to, for example, an inverter 3. The inverter 3, in turn, can supply, for example, an electric drive motor of the motor vehicle 1 or the like. The power supply to the inverter 3 can be controlled by a corresponding control unit. However, in current control unit development for the automotive sector, functional safety requirements up to ASIL D are increasingly demanded. These requirements can relate to various functions within a control unit, such as overcurrent detection, in order to prevent overloading a core component of the inverter 3 in the event of, for example, a short circuit, or to avoid an unsafe state of the inverter 3.

[0058] To meet these requirements, an overcurrent protection device 4 is connected between battery 2 and inverter 3, particularly as part of the corresponding control unit. The overcurrent protection device 4 has an input 5, to which battery 2 is connected, and an output 6, to which inverter 3 is connected. A main current path runs from input 5 to output 6 within the overcurrent protection device 4. A measuring resistor RM and, at its output, a main path transistor T1 are arranged in this main current path. Here, the main path transistor T1 is implemented as a PMOS transistor, with its source connected to the measuring resistor RM and its drain to output 6. However, other types of transistors can also be used.

[0059] In normal operation, battery 2 supplies an input voltage Uin at input 5, i.e., at the beginning of the main current path, and the main path transistor T1 is closed, i.e., conducting. Therefore, a current then flows through the measuring resistor RM and through the main path transistor T1 to output 6.

[0060] In the overcurrent protection device 4, a voltage drop across the measuring resistor RM is monitored, i.e., continuously measured during operation. For this purpose, a first measuring voltage signal USh1 is tapped from the measuring resistor RM at the input side, and a second measuring voltage signal USh2 is tapped between the measuring resistor RM and the main path transistor T1. To amplify the corresponding voltage drop, the overcurrent protection device 4 includes a differential amplifier D, to which the measuring voltage signals USh1 and USh2 are fed at the input side. Furthermore, the overcurrent protection device 4 includes a comparator circuit with a first comparator K1 and a second comparator K2 connected downstream. Here, a voltage signal, amplified by the differential amplifier D and corresponding to the voltage drop across the measuring resistor RM, is applied to a measuring input of the first comparator K1. The comparator K1 also has a reference input.A voltage signal corresponding to a predefined voltage threshold is permanently applied to this point. A static voltage divider consisting of a first threshold resistor RS1 and a second threshold resistor RS2 connected in series is used to set or provide this voltage threshold. This static voltage divider is supplied with an input voltage Uin and its output is grounded or connected to a ground potential. The voltage signal, or voltage threshold, for the reference input of the first comparator K1 is then tapped between the first threshold resistor RS1 and the second threshold resistor RS2.

[0061] In normal, fault-free operation, i.e., outside of an overcurrent state, the voltage signal at the measurement input of the first comparator can be below the voltage threshold. In this case, comparator K1 can output a correspondingly low first comparator voltage UK1, i.e., a low signal. The output of the first comparator K1 is connected to the gate of the main path transistor T1 and thus serves to control it.

[0062] Furthermore, the output of the first comparator K1 is connected to a storage circuit or a storage circuit part of the comparator circuit, which includes a switchable or controllable voltage divider and the second comparator K2 with corresponding supply.

[0063] If the voltage drop across the measuring resistor RM, or the corresponding voltage signal at the output of the differential amplifier D, exceeds the voltage threshold freely defined by the appropriate setting of the threshold resistors RS1 and RS2, the comparison result of the first comparator K1 changes. This increases the first comparator voltage UK1, setting it to a high signal. As a result, the main path transistor T1 is either opened or closed, thus interrupting the main current path.

[0064] To prevent the main path transistor T1 from being immediately closed again, i.e., switched to conducting, the comparator circuit is not only set up as a comparison component, but is also used by the aforementioned memory circuit as a memory for a detected overcurrent, i.e. to maintain the interruption of the main current path.

[0065] The controllable voltage divider of the memory circuit comprises a first voltage divider resistor RSP1 and a second voltage divider resistor RSP2 connected in series with it. Furthermore, the controllable voltage divider includes another branch connected in series with the first voltage divider resistor RSP1 and in parallel with the second voltage divider resistor RSP2. This branch contains a third voltage divider resistor RSP3 and a voltage divider transistor T4 connected in series with it. Here, voltage divider transistor T4 is implemented as a PNP transistor. Its base is connected to the output of the first comparator K1. The emitter of voltage divider transistor T4 is connected to the third voltage divider resistor RSP3, while the collector of voltage divider transistor T4, as well as one output terminal of the second voltage divider resistor RSP2, is at ground potential.On the input side, the controllable or switchable voltage divider, i.e., a terminal of the first voltage divider resistor RSP1 opposite the second voltage divider resistor RSP2, is permanently supplied with the input voltage Uin. A voltage signal for a measurement input of the second comparator K2 is tapped at a point between the voltage divider resistors RSP1, RSP2, and RSP3. The second comparator K2 also has a reference input to which a predefined reference voltage signal is permanently applied. To define or adjust this reference voltage signal for the reference input of the second comparator K2, a further voltage divider consisting of a third voltage divider resistor RS3 and a fourth voltage divider resistor RS4 is provided.

[0066] When the main path transistor T1 is switched off (i.e., due to an overcurrent), the correspondingly high first comparator voltage UK1 is applied to the base of the voltage divider transistor T4, which is thereby switched off. This switching of the voltage divider transistor T4 changes the voltage divider ratio at the tap point for the voltage signal supplied to the measurement input of the second comparator K2. Specifically, the voltage at the tap point, and thus also at the measurement input of the second comparator K2, increases to such an extent that it exceeds the reference voltage applied to the positive reference input of the second comparator K2. This, in turn, changes the second comparator voltage UK2 at the output of the second comparator K2, specifically towards a low signal. The second comparator voltage UK2 then controls, or switches, a storage circuit transistor T3.For this purpose, the output of the second comparator K2 is connected to the gate of the memory circuit transistor T3. The drain of the memory circuit transistor T3 is permanently supplied by an input voltage Uin that is above the voltage threshold at the reference input of the first comparator K1. In the normal, fault-free state, the memory circuit transistor T3 is off, so its output (source) does not affect the first comparator K1.

[0067] The change in the second comparator voltage UK2, caused by the overcurrent as described, switches the storage circuit transistor T3 into conduction. This means that, until the storage circuit transistor T3 switches off again, the voltage signal above the voltage threshold from the input or drain of the storage circuit transistor T3 is permanently present at the measurement input of the first comparator K1, regardless of whether the overcurrent state persists. The storage circuit transistor T3 thus manipulates the measurement input of the first comparator K1, thereby permanently defining the first comparator voltage UK1 at the output of the first comparator K1, i.e., keeping it at the high signal. This can be considered a storage of the overcurrent state, since the main path transistor T1 remains permanently switched off. Effectively, the storage circuit can function as a discretely constructed latch.

[0068] The overcurrent protection device 4 also features an edge-triggered switching function. For this purpose, the overcurrent protection device 4 includes a corresponding control unit, implemented here as a microcontroller 7. The microcontroller 7 has a first output, to which a capacitor C is connected. One side of the capacitor C facing away from the microcontroller 7 is connected to the measuring input of the first comparator K1. If the microcontroller 7 now outputs a high signal or a high level, i.e., a correspondingly high DC voltage signal, via the first output, this is filtered by the capacitor C so that only an AC signal, namely a corresponding positive or rising voltage edge, is supplied as the switching voltage signal Uena from the output of the capacitor C to the measuring input of the first comparator K1.Due to this rising voltage edge, the voltage threshold applied to the reference input of the first comparator K1 is exceeded at its measuring input, and the same mechanism for the occurrence of an overcurrent is triggered as described above, so that the circuit is switched off, i.e., the main path transistor T1 is blocked and thus the main current path is interrupted.

[0069] To reactivate the circuit, i.e., to close the main path transistor T1 and thus end the interruption of the main current path, the high level at the first output of microcontroller 7 can be reduced, thus stopping the output of the corresponding DC voltage signal. In this case, capacitor C only allows a corresponding negative or falling voltage edge to pass, so that the measurement input of the first comparator K1 falls again below the voltage threshold defined by the static voltage divider, resulting in the corresponding inverse switching voltage signal Uena. This ultimately closes the main path transistor T1, i.e., switches it on. The on / off function can be used to...The microcontroller 7 can therefore reset the overcurrent protection device 4 after blocking the main current path due to an overcurrent, or the main current path can be interrupted or switched on, i.e., made conductive, even without an overcurrent condition.

[0070] To ensure the functionality of the overcurrent protection device 4, the overcurrent protection device 4 also includes or implements a test circuit. This includes a current-limiting test circuit resistor RT and a test circuit transistor T2. One terminal of the test circuit resistor RT is connected to a point on the main current path located between the main path transistor T1 and the output 6, and the other terminal is connected to the drain of the test circuit transistor T2. The source terminal of the test circuit transistor T2 is connected to ground potential. The gate of the test circuit transistor T2 is connected to a second output of the microcontroller 7.The microcontroller 7 can use this second output to apply a test voltage signal Utest to the gate of the test circuit transistor T2, thus switching it on when needed, i.e., for testing. Outside of such testing, the test circuit transistor T2 can be permanently off. The microcontroller 7 can therefore switch on the test circuit transistor T2, simulating a short circuit. It can then be checked whether the main path transistor T1 opens as intended, thus interrupting the main current path and confirming that the overcurrent protection device 4 is functioning correctly.

[0071] When the overcurrent protection device 4 is used in the motor vehicle 1, such testing can be carried out in every operating cycle, for example, every time the motor vehicle 1 is started up, i.e., every terminal 15 event, and / or every time the motor vehicle 1 is switched off. This allows the requirements regarding functional safety, for example up to ASIL D, to be met.

[0072] The overcurrent protection device can also be used to implement four additional functions. For example, by appropriately controlling the main path transistor T1 – within the relevant design or component limits – any application current can be used to supply a load connected to output 6, in this case, inverter 3.

[0073] The ones mentioned in various places, or mentioned in various places in Fig. The input voltages Uin listed in section 1 can be the same, i.e., identical. Likewise, different input voltages Uin can be used at some or all of the points marked Uin in the overcurrent protection device 4.

[0074] Fig. Figure 2 shows a partial schematic representation of an alternative embodiment of a motor vehicle 1, which has a battery 2 for the electrical supply of, for example, an inverter 3. In this embodiment, the overcurrent protection device 4 comprises a Schmitt trigger circuit with a Schmitt trigger 9, as well as a reference voltage divider and a storage voltage divider.

[0075] The reference voltage divider consists of a first threshold resistor RN1 and a second threshold resistor RN2. The reference voltage divider is supplied with the input voltage Uin via the first threshold resistor RN1. A node located between the two threshold resistors RN1 and RN2 is connected to a negative input of the Schmitt trigger 9. The second threshold resistor RN2 is connected to a ground point on the output side. Using the reference voltage divider, a predefined voltage threshold can be generated from the input voltage Uin and applied to the negative input of the Schmitt trigger 9.

[0076] The storage voltage divider consists of a first voltage divider resistor RS10, a second voltage divider resistor RS20, and a third voltage divider resistor RS30. The first voltage divider resistor RS10 and the second voltage divider resistor RS20 are connected in series between an output of the differential amplifier D and a positive input of the Schmitt trigger 9 and can therefore also be referred to as series resistors. The third voltage divider resistor RS30 is connected in parallel with the Schmitt trigger 9, i.e., as a parallel resistor in a path leading from the positive input of the Schmitt trigger 9 to its output. The output of the Schmitt trigger 9 is connected to the gate of the main path transistor T1. Thus, a trigger voltage signal UT can be applied from the output of the Schmitt trigger 9 to the gate of the main path transistor T1 to switch it on or off depending on the situation.

[0077] If the voltage signal corresponding to the voltage drop measured across the measuring resistor RM at the positive input of the Schmitt trigger 9 exceeds the predetermined voltage threshold applied to its negative input, the main path transistor T1 is switched off by the correspondingly high trigger voltage signal UT.

[0078] To enable the main path transistor T1 to be switched on again when needed or after a corresponding overcurrent condition has been rectified, the overcurrent protection device 4 also includes a corresponding control circuit. This includes a control unit, which in this case is implemented as a microcontroller 7. An output of the microcontroller 7 is connected via a slope-detection capacitor CF to a point located between the first voltage divider resistor RS10 and the second voltage divider resistor RS20. Thus, a switching voltage signal Uena can be applied to this point by means of the microcontroller 7, which, depending on the slope direction, changes the trigger voltage signal UT and thus ultimately switches the main path transistor T1.A capacitor, referred to here as switching capacitor CS, is also arranged between the corresponding point between the first voltage divider resistor RS10 and the second voltage divider resistor RS20 and a ground potential point.

[0079] Furthermore, this embodiment of the overcurrent protection device 4 also includes a test circuit. This comprises a corresponding circuit or function of the microcontroller 7 and a test circuit path or branch branching off from the main current path between the main path transistor T1 and the output 6. A test circuit resistor RT and a test circuit transistor T2 are arranged within this test circuit. Here, the test circuit transistor T2 is configured as an NMOS, with its drain connected to the test circuit resistor RT and its source to a ground point. The gate of the test circuit transistor T2 is connected to a test output of the microcontroller 7. Via this test output, the microcontroller 7 can apply a test voltage signal UTest to the gate of the test circuit transistor T2, thereby switching it on. This simulates a short circuit and leads to an overcurrent in the main current path.This allows for targeted testing to determine whether the Schmitt trigger circuit effectively blocks the main path transistor T1 and thus interrupts the main current path.

[0080] The circuit described here can be implemented with the components used for any input voltage, for example up to 40 V. Furthermore, any application current can be realized using the main path transistor T1.

[0081] Depending on the respective safety requirements or a respective safety concept, the overcurrent protection device 4 can, for example, be tested for classification according to ASIL D during one, in particular every, commissioning of the motor vehicle 1, i.e. at each terminal 15 event, and / or each, in particular every, switching off of the motor vehicle 1.

[0082] Overall, the examples described show how a discretely designed overcurrent monitoring system with enabling and ASIL D test functions can be implemented and applied. Reference symbol list 1 motor vehicle 2 batteries 3 Inverter 4 Overcurrent protection device 5 Entrance 6 Exit 7 microcontrollers 9 Schmitt triggers C capacitor CF edge control capacitor CS switching capacitor D Differential amplifier K1 first comparator K2 second comparator RM measuring resistor RN1 first threshold resistance RN2 second threshold resistor RS1 first threshold resistor RS2 second threshold resistor RS3 third threshold resistor RS4 fourth threshold resistor RS10 first voltage divider resistor RS20 second voltage divider resistor RS30 third voltage divider resistor RSP1 first voltage divider resistor RSP2 second threshold resistor RSP3 third threshold resistor RT test circuit resistor T1 Main path transistor T2 test circuit transistor T3 storage circuit transistor T4 voltage divider transistor Uin input voltage USh1 first measurement voltage signal USh2 second measurement voltage signal UK1 first comparator voltage UK2 second comparator voltage Uena switching voltage signal UT trigger voltage signal Utest test voltage signal QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CN 221 652 232 U

[0003] DE 40 00 820 A1

[0004] DE 102018 209 681 A1

[0005] DE 10 2016 114 740 B3

[0006] EP 2 720 053 A2

[0007] DE 10 2021 130 379 A1

[0008] CN 107 528 297 A

[0009] KR 2019 0 017 298 A

[0010]

Claims

[1] Overcurrent protection device (4) for arrangement between a DC voltage source (2) and a load (3) to be supplied electrically therewith, comprising a discrete circuit with an input (5) for connecting the voltage source (2), an output (6) for connecting the load (3) and a main current path running from the input (5) to the output (6), wherein the discrete circuit - an input-side voltmeter for monitoring a voltage drop (USh1-USh2) across a measuring resistor (RM) arranged in the main current path, - a main path transistor (T1) arranged on the output side of the measuring resistor (RM) in the main current path, by means of which the main current path can be switched and interrupted, - comprising a comparator circuit arranged outside the main current path for comparing the measured voltage drop with a predetermined voltage threshold, wherein - in the discrete circuit, a voltage measurement signal corresponding to the measured voltage drop is applied to a measurement input of a first comparator (K1) of the comparator circuit, - an output of the first comparator (K1) is connected to the main path transistor (T1) to switch it off when the voltage threshold is exceeded, and - the comparator circuit is also set up as a storage circuit for a detected overcurrent condition and, for this purpose, upon exceeding the voltage threshold, permanently applies a voltage signal above the voltage threshold to the measuring input of the first comparator (K1), regardless of whether the overcurrent condition continues to exist, so that the main path transistor (T1) remains switched off and a) The comparator circuit comprises a second comparator (K2) connected downstream of the first comparator (K1) and a switchable voltage divider (RSP1, RSP2, RSP3, T4) arranged between the first comparator (K1) and the second comparator (K2), which, upon detection of a voltage threshold being exceeded, is switched by a corresponding output signal (UK1) at the output of the first comparator (K1) to a state in which the second comparator (K2) provides an output signal (UK2) which then causes the voltage signal above the voltage threshold to be applied to the measuring input of the first comparator (K1) and / or b) the overcurrent protection device (4) includes a control device (7) for controlled switching of the main path transistor (T1) and the control device (7) is connected to the measuring input of the first comparator (K1) via a capacitor (C). [2] Overcurrent protection device (4) according to claim 1,characterized by , that the discrete circuit includes a differential amplifier (D) for amplifying the measured voltage drop, which is connected between the main current path and the measurement input of the first comparator (K1). [3] Overcurrent protection device (4) according to one of the preceding claims including variant a), characterized by, that the switchable voltage divider (RSP1, RSP2, RSP3, T4) comprises a first voltage divider resistor (RSP1), a second voltage divider resistor (RSP2) arranged in series with it, and a voltage divider transistor (T4) arranged in series with the first voltage divider resistor (RSP1) and in parallel with the second voltage divider resistor (RSP2), and which can be switched by the output signal (UK1) of the first comparator (K1) in order to change the output signal (UK2) of the second comparator (K2), wherein the second comparator (K2) compares the voltage applied between the first voltage divider resistor (RSP1) and the second voltage divider resistor (RSP2) with a predetermined reference voltage. [4] Overcurrent protection device (4) according to claim 3, characterized by, that the output of the second comparator (K2) is connected to a storage circuit transistor (T3) arranged between it and the measuring input of the first comparator (K1), at whose terminal the voltage signal above the voltage threshold is applied and which is blocked before the detection of an overcurrent condition and is then switched to conducting by the corresponding output signal (UK2) of the second comparator (K2), so that the voltage signal above the voltage threshold is applied to the measuring input of the first comparator (K1). [5] Overcurrent protection device (4) according to any one of the preceding claims, characterized by, that the overcurrent protection device (4) comprises a test circuit for testing the functionality of the overcurrent protection device (4) for interrupting the main current path in the event of an overcurrent condition, wherein the test circuit comprises a control device (7), a test circuit resistor (RT) and a test circuit transistor (T2) that can be switched by means of the control device (7), wherein the test circuit resistor (RT) and the test circuit transistor (T2) are arranged in series in a test circuit path that runs from a point of the main current path located on the output side of the main path transistor (T1) to a ground potential point. [6] Control unit (4), in particular for a motor vehicle (1), comprising an overcurrent protection device (4) according to one of the preceding claims. [7] Motor vehicle (1) comprising a control unit (4) according to claim 6 for controlling at least one device (3) or function of the motor vehicle (1).

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