Method for limiting load current

Abstract

A method for limiting a load current in a supply line, the supply line supplying a first load with a current, is described, the method having the steps of: - specifying a first time interval and a second time interval, (S1), wherein the first time interval starts after a switching-on time (TO) of the first load to the supply line and the second time interval starts later than the first time interval; - limiting the load current to a first value (II) within the first time interval and the second time interval, (S2); - limiting the load current (S3) to a second value (I2) at least at the end (T3) of the second time interval, wherein the second value (I2) is smaller than the first value (II).

Description

Technical Field

[0001] The present invention relates to a method for limiting load current in a power supply line that supplies current to a first load. Background Technology

[0002] In a vehicle's electric onboard electrical network, resistance exists due to factors such as wiring or contacts. If current flows through this resistance, a voltage drop occurs across it, reducing the available terminal voltage for the consumer or load. This voltage drop also increases with the level of current flowing through these resistors. Due to the required power and relatively low voltage in the onboard electrical network, a very large current flows, making this effect significant for the function of connected electrical loads such as electrical assemblies. If an excessively low voltage is applied to the connection terminals of such an assembly due to a voltage drop across at least part of the power supply line, it may be impossible to maintain all functions, or performance may be limited. Depending on the type of assembly and the programmed scenario, the performance of such an assembly (e.g., an electrically operated brake) may then be reduced, or the assembly may be deactivated using appropriate warnings, or transitioned to a recovery stage via a redundant system. Summary of the Invention

[0003] To limit such voltage fluctuations caused by resistance in the power supply line, a system is established that includes a current limiting device, which in this case functions directly to reduce the current consumption of the power consumer. This, in several cases, prevents a transition to a recovery stage of the second assembly supplied with the same leads as the load itself or the receiver. However, this subsequently results in reduced performance of such an assembly.

[0004] The present invention discloses a method, an apparatus, a computer program, and a machine-readable storage medium for limiting load current in a power supply line.

[0005] This invention is based on the understanding that it is more advantageous to incorporate a current limiting device into the entire system so that, even if this results in a power loss in the primary equipment, the additional functions provided by the secondary connected equipment are maintained. For example, maintaining the anti-lock braking system (ABS) for an extended period during braking may be more important than the maximum braking force, since the brakes are already locked at 40% braking force under normal conditions.

[0006] According to one aspect, a method for limiting load current in a power supply line is disclosed, wherein the power supply line supplies current to a first load. In one step of the method, a first time interval and a second time interval are defined, wherein the first time interval begins after the moment the first load is switched on to the power supply line, and the second time interval begins later than the first time interval.

[0007] In other steps, the load current is limited to a first maximum value within the first and second time intervals.

[0008] In other steps, at least at the end of the second time interval, the load current is limited to a second maximum value, which is less than the first maximum value.

[0009] Throughout the description of the invention, a sequence of method steps has been shown to facilitate understanding of the method. However, those skilled in the art will recognize that many of these method steps can be traversed in a different order, and that these method steps lead to the same or corresponding results. In this sense, the order of the method steps can be changed accordingly.

[0010] The advantage of limiting the load current to a first value within the first and second time intervals after the first load (which is then connected to the power supply line) is that the voltage drop across at least a portion of the power supply line can be limited. This is because a voltage drop, caused by the current, can occur both within the power supply line itself and at the contact points due to the resistance in the leads from the power supply line to the first load. By limiting this current, it is prevented that the terminal voltage across the first load and other loads can drop below the resulting voltage value. This is because the voltage drop across the resistance of the leads must be subtracted from the supply voltage (e.g., from the current source), and this voltage drop then becomes a terminal voltage and is no longer used by, for example, the first load.

[0011] Therefore, it is possible to limit the load current to a minimum terminal voltage, which the first load requires to provide at least one basic function. Here, the first load can also be understood as a system with multiple loads. This can be particularly significant for the braking system of an electrically driven vehicle, as braking systems are typically designed such that a small fraction of their performance is sufficient to apply full braking power under normal conditions. This could mean that, for example, a wheel might become stuck under braking conditions due to this small fraction of performance. By utilizing the limitation of the load current to a minimum terminal voltage, it is also possible to provide a minimum terminal voltage to ensure the function of other assemblies, which are also powered by the power supply line.

[0012] By limiting the load current to a second value less than the first value at least at the end of the second time interval, it is possible to further limit the load current during the second time period after the load is connected to the power supply line, so as to provide a terminal voltage higher than the aforementioned minimum terminal voltage at the first load. This may be particularly advantageous when other assemblies also supplied with power by the power supply line require a terminal voltage higher than the minimum terminal voltage in order to provide their function beyond a certain period of time.

[0013] Therefore, during the first time interval, for example for the first load, a maximum load current of a level that may be required, at a first value, can be provided, wherein other equipment (as secondary loads) also maintains its function during the first time interval, and this is ensured by additionally limiting the load current during the second time interval, even if this impairs the performance of the first load during the second time interval. This is because by limiting the current to a lower value, the first load can also draw only a lower load current from the power supply line.

[0014] According to the construction scheme of this method, the second time interval should directly follow the first time interval.

[0015] Between the first and second time intervals, a time interval can also be set such that the constraint shifts from the first value to the second value. Depending on the system architecture for the constraint at the first or second value, a corresponding transition time may be required. Similarly, other time intervals can be set at the moment the first load is applied and after the start of the first time interval.

[0016] Other construction schemes based on this method suggest that, by using the load current characteristic curve, the first value of the load current is determined based on the terminal voltage of the first load.

[0017] By using this load current characteristic curve, which defines the relationship between the load current and the terminal voltage across the first load, it can be ensured that the load current is limited so widely that the voltage generated at the electrical connection of the first load is not lower than a minimum value.

[0018] This safety measure ensures that at least other equipment connected to the vehicle's electrical grid retains its functionality in the event of a malfunction, such as the failure of the first load, because it maintains the corresponding minimum voltage, which would otherwise pull the entire vehicle's electrical grid to an excessively low voltage.

[0019] Other construction schemes of this method suggest determining the terminal voltage of the load current characteristic curve in the first and / or second time interval. If the load current continues to be limited to the first value in the second time interval, the terminal voltage must also be determined in the second time interval. If the load current is limited to a second value less than the first value in the second time interval, a recovery solution for limiting the load current is achieved by limiting the load current to the first value in the second time interval, which improves the safety of the entire system.

[0020] Other construction schemes of this method suggest determining the terminal voltage outside of the first and second time intervals. This achieves the goal of providing the terminal voltage value of the first load before connecting it to the power supply line, thus enabling current load limitation for a short period after the first load is connected to the power supply line.

[0021] Other construction schemes of this method suggest that, based on the terminal voltage on the first load or the second load, the first value of the load current is limited by controlling the level of the load current value.

[0022] Other construction schemes based on this method suggest determining a second value for the load current by using the resistance value of at least a portion of the power supply line.

[0023] At least a portion of the power supply line can have this resistance value determined in a separate resistance measurement. This resistance can be generated by the resistance of the power supply line itself, as this value may increase during the operation of such a vehicle, for example, due to corrosion. In addition, this resistance is derived from the transition resistance (Uebergangswiderstaende) (primarily at the contacts), which may increase during operation, for example, due to corrosion.

[0024] Unless otherwise explicitly stated, the resistance of such a power supply line is understood here as encompassing all resistances that generate a terminal voltage at the end of a power supply line connected to a load, in the sense that such resistance is considered a single value. That is, this also includes contact resistance and grounding connections.

[0025] If the resistance value of the power supply line is known, for example, from previous measurements, then Ohm's law can be used to determine the maximum possible current in order to ensure the corresponding minimum terminal voltage at the first load.

[0026] Since other equipment or loads also connected to the power supply line can maintain their function during the period including the first and second time intervals, the minimum terminal voltage is guaranteed by the current being correspondingly limited at the end of the second time interval. This minimum terminal voltage is necessary for such equipment to continuously maintain its function.

[0027] Here, for example, the first time interval can be chosen to be very short, or the value can also determine the load current within the first time interval as follows: the current is limited to the value within the first time interval.

[0028] Other construction schemes of this method suggest determining the resistance value of at least a portion of the power supply line, independent of the method used to limit the load current. This, for example, achieves that, during a first time interval—that is, immediately after, for example, the first load is connected to the power supply line—the load current can be limited to a determined first value for the load current.

[0029] According to the construction scheme of this method, during the first and second time intervals, the load current is limited to a second value for the load current, wherein the second value is determined by means of the resistance value described above for at least a portion of the power supply line.

[0030] In this way, a certain minimum terminal voltage is maintained both in the first time interval and in the second time interval.

[0031] According to the proposed construction scheme of this method, at the beginning of the second time interval, the load current is limited to a first value, and during the second time interval, the load current is limited to a second value by means of a predefined change process of the load current.

[0032] This change process can be linear, progressive, decreasing, monotonically decreasing, or switching, that is, controlled by transitions during the change process. Therefore, in the second time interval, a higher load current is also provided, for example, during the second time interval of the first load, enabling the delivery of higher power. For an electrically driven braking system, this may mean that the braking power during the second time interval is higher than the braking power after the end of the second time interval.

[0033] According to other construction schemes of this method, the load current during the second time interval is limited by utilizing a pre-given rated voltage variation process and the terminal voltage measured on the first load in the first and / or second time intervals. In this construction scheme, it is therefore unnecessary to know the resistance value, as a portion of the voltage can drop across that resistance value based on the load current, thus providing a reduced terminal voltage. By determining the voltage, such as the terminal voltage on the first load, compared to the rated voltage or the rated voltage variation process, a second value of the load current can be determined, for example, using a control circuit, to limit it to that value. Therefore, the pre-given rated voltage variation process can be very closely adapted to the possible rated voltages in different time windows, and thus, for example, provides the maximum possible current for the first load, which, due to the current voltage measurement, can take into account the current state of the vehicle electrical network. At the end of the second time interval T3, this rated voltage variation process can pre-given a rated voltage of level U2 so that the continued operation of the second load can be achieved as described above.

[0034] In this way, it is achieved that the resistance value of the power supply line does not need to be determined in advance, and the load current is really limited only in terms of its level and the available second time interval as much as is required to guarantee the minimum terminal voltage (rated voltage).

[0035] Therefore, it is achieved that, during the second time interval, the maximum load current can be provided to the first load under given boundary conditions of the required terminal voltage. By limiting the load current during the second time interval, other assemblies or second loads that temporarily require the first terminal voltage or persistently require a second terminal voltage higher than the first terminal voltage can be operated continuously. Nevertheless, a load current is also provided to the first load during the second time interval that enables higher performance.

[0036] In addition, given the lead resistance, this can be taken into account in determining the second value of the load current based on the terminal voltage, so as to optimize the adjustment method of the current limit for the load current based on the terminal voltage compared with the rated voltage.

[0037] Other construction schemes of this method suggest that no load current limitation is performed before the first time interval or during the startup time interval between the first and second time intervals. For example, voltage measurement can be performed during this startup time interval, or there can be a dead time for electronic circuitry to limit the load current.

[0038] Other construction schemes of this method suggest that parameters related to the correction speed of voltage regulation are determined by using the measured first voltage value and the rated voltage value, as well as a pre-given second time interval.

[0039] This allows the determination of a second value for the load current based on the measured voltage to be optimally suited to a given system. Here, the possibly known resistance value of the power supply line can also be considered.

[0040] Other construction schemes based on this method suggest that the power supply line supplies current to the first load and the second load, and determines a second value of the load current based on the minimum terminal voltage of the second load.

[0041] By considering the minimum terminal voltage of the second load, the second load can operate at least after the end of the second time interval. If the first load requires a lower minimum voltage for basic function than the second load, the second load can operate further after the end of the second time interval. Here, the second load can be configured such that it provides the function of the second load for a finite time within either the first or second time interval.

[0042] After a predetermined time and based on the voltage supplied to the second load, the second load can be configured to set the function and be put back into operation only via a reset process, which may require an unacceptable duration. The duration of function setting or the voltage supplied to the first or second load may be different for the first or second load. The first time interval and / or the second time interval may be defined by a period in which the second load remains operational under the second terminal voltage; or by a time range in which the reset process must not be triggered before the time range has elapsed.

[0043] Other construction schemes based on this method suggest that when the load current level reaches a first and / or a second value of the load current, control signals for operating at least partially automated vehicles and / or alarm signals for warning vehicle occupants are issued.

[0044] Other construction schemes of this method suggest that when the load current level reaches or exceeds a first and / or second value of the load current for a specified duration, a control signal for operating at least partially automated vehicles and / or an alarm signal for warning vehicle occupants are issued. Here, the specified duration also includes the minimum possible time interval during which a single value is exceeded.

[0045] Since reaching the load current corresponding to the first value and / or that level means that the function of the first or second load may be at least partially limited, this could result in a certain driving maneuver no longer being performed in at least partially automated vehicles, or the driver having to manually operate the vehicle again. If full functionality is subsequently restored due to a brief period of limited functionality, then a warning to the vehicle driver may be sufficient.

[0046] An apparatus is disclosed that is configured to perform the method described above. Using this apparatus, the method can be quickly and easily integrated into different, larger units. Such larger units can be at least partially automated vehicles, or they can be driver assistance systems used in vehicles.

[0047] The described method for limiting load current in power supply lines can be used in many applications, particularly in all applications where electro-hydraulic braking systems are used. In this context, "vehicle" is generally understood to mean automobiles, including at least partially automated vehicles or vehicles with driver assistance systems, and especially to mean motorcycles, construction machinery, agricultural vehicles, and others. However, vehicles also typically include mobile platforms, mobile multi-sensor robots, such as robotic vacuum cleaners or lawnmowers, mobile multi-sensor monitoring systems, production machines, personal assistants, or access control systems. Furthermore, the method can also be used in non-mobile machines, for example, those with electro-hydraulic braking systems.

[0048] A computer program is disclosed, comprising instructions that, when executed by a computer, cause the computer to perform the method described above. Using this computer program, the method can be easily integrated into different systems.

[0049] A machine-readable storage medium is disclosed on which the computer program product described above is stored. Using this machine-readable storage medium, the computer program described above can be easily transported. Attached Figure Description

[0050] about Figures 1 to 3 Embodiments of the invention are shown and described in more detail below.

[0051] Figure 1 The rated voltage and time interval of this method are shown;

[0052] Figure 2 An example is shown for a restricted load current variation process within the time interval of this method;

[0053] Figure 3An exemplary process of the change in the load current characteristic curve is shown;

[0054] Figure 4 An exemplary process of terminal voltage variation during a time interval is shown; and

[0055] Figure 5 The steps of a method for limiting load current are shown. Detailed Implementation

[0056] exist Figure 1 The diagram illustrates, exemplarily, the rated voltage at different time intervals after the load is connected to the power supply line. At time point T0, the first load is connected to the power supply line, and the startup time interval may follow from time point T0 until T1, during which current limiting may be absent or not shown here. Alternatively, the startup time interval may be omitted entirely.

[0057] The first time interval begins at time point T1 and, for example, can end at time point T2. Figure 1 In this process, the second time interval directly follows the first time interval, with the second time interval ending at time point T3. The time interval between T2' and T3 can be set as a safety lead for the compensation process or for a time interval in which the terminal voltage is adjusted from U1 to U2 based on the adjustment of the current according to the terminal voltage.

[0058] The first rated voltage U1 is less than the second rated voltage U2 and extends from T1 to T3. The second rated voltage U2 begins at time T3. These voltages and time intervals may be given based on technical specifications or requirements for, for example, a complete set of equipment corresponding to a first load connected to the power supply line as a second load and thus having the same power supply line.

[0059] In the first embodiment, the terminal voltage of the first load is maintained below the second rated voltage U2 and above the first rated voltage U1 for a finite time interval between T1 and T3. Therefore, the load current of the power supply line supplying current to the first load is limited.

[0060] A first time interval from T1 to T2 and a second time interval from T2 to T3 are defined as S1, wherein the first time interval begins directly after the connection time T1 of the first load to the power supply line. Alternatively, the defined start interval between the load connection time and the start of the first time interval at T1 can also be between T0 and T1. Here, the second time interval begins later at time T2 than the first time interval begins at time T1. Figure 1In this context, the second time interval directly follows the first time interval at time point T2.

[0061] Figure 2 The variation of the load current 24 during a first time interval and a second time interval before the load is connected to the power supply line is shown. This load current 24 is limited according to this method, and is, for example, the value of the load current I0, to a first value I1, S2. Here, the load current characteristic curve 30 ( Figure 3 Based on the terminal voltage of the first load, determine the first value I1 of the load current.

[0062] exist Figure 3 An exemplary load current characteristic curve is drafted for determining the required current limit based on the terminal voltage U of the first load. The maximum current I0 can be supplied by the power supply line as long as the terminal voltage U of the first load is greater than the second rated voltage U2. Once the measurement of the terminal voltage U determines that it is lower than the second rated voltage U2, the load current is reduced, for example, to a first value I1 of the load current according to characteristic curve 30, in order to ensure a terminal voltage U at the level of the first rated voltage U1 on the first load.

[0063] The load current in the power supply line of the first load is limited by S3 during the second time interval such that, at least at the end of the second time interval T3, the load current is not higher than the second value I2, where the second value I2 is less than the first value I1 of the load current.

[0064] According to one embodiment, the terminal voltage U is determined during a first and / or second time interval, and a second value I2 of the load current is determined by a resistance value, specifically by the resistance value of at least a portion of the power supply line. The resistance value of at least a portion of the power supply line can be determined using a method independent of the load current limitation. Here, according to Ohm's law, the second current I2 is calculated from the determined or measured terminal voltage using this resistance value. Since the load current is further limited from the first value I1 to the second value I2, possible changes in the terminal voltage can cause... Figure 4 The terminal voltage change process 46 is shown. Here, the terminal voltage change is such that voltage-time ranges 42, 44, which might cause the equipment to shut down, are avoided. During the period following the second time interval, a terminal voltage U is thus generated for the first load, which is greater than the value U2, and therefore other equipment electrically connected to the power supply line can operate continuously, as described above.

[0065] According to other embodiments, the load current is limited to a second value I2 determined such that, during the first and second time intervals, as in Figure 2 The process of load current change in the power supply line is simulated as described in section 22.

[0066] According to other embodiments, the load current can be limited to a first value I1 at the beginning of the second time interval T2, and during the second time interval, according to a predetermined change process, the load current can be limited to a second value I2 at the end of the second time interval T3. This is in Figure 2 The variation of the load current in the first and second time intervals is illustrated using processes 24 and 26, wherein, in process 26, a primarily linear variation is selected in the second time interval. However, the variation of the load current in the second time interval can also have other shapes, such as those illustrated, for example, by process 24, which also has a transition at time point T2.

[0067] According to other embodiments, the load current is limited to a second value I2 during the second time interval. This second value I2 is not calculated by resistance measurement as shown above, but is determined by an adjustment method during the second time interval using a pre-given rated voltage (e.g., a first rated voltage U1) and a terminal voltage U measured on the first load during the first and / or second time intervals. For this purpose, the terminal voltage U is repeatedly measured at least during the second time interval so that the load current is limited to a corresponding value according to the adjustment method, such that during the second time interval, the terminal voltage U on the first load is greater than the first rated voltage U1, and at the end of the second time interval, the load current is limited to the second value I2, such that the terminal voltage U on the first load is greater than the second rated voltage U2.

[0068] exist Figure 5 In the above, the method steps S1 to S3 described above were drafted.

Claims

1. A method for limiting load current in a power supply line, the power supply line supplying current to a first load and a second load, the method comprising the steps of: - Define a first time interval and a second time interval, wherein the first time interval begins after the connection time (T0) from the first load to the power supply line, and the second time interval begins later than the first time interval; - During the first time interval and the second time interval, the load current is limited to a first value (I1) such that it is not lower than the minimum terminal voltage required by the first load to provide at least one basic function, wherein the first value (I1) for the load current is determined based on the terminal voltage of the first load using the load current characteristic curve. - At least at the end of the second time interval (T3), the load current is limited to a second value (I2) less than the first value (I1), such that a terminal voltage higher than the minimum terminal voltage is provided at the first load. in, The second value (I2) of the load current is determined based on the terminal voltage of the second load.

2. The method according to claim 1, wherein, The terminal voltage is determined during the first time interval and / or the second time interval.

3. The method according to claim 1, wherein, The second value for the load current is determined by the resistance value of at least a portion of the power supply line.

4. The method according to any one of claims 1-3, wherein, The load current is limited to the second value (I2) during the first time interval and the second time interval.

5. The method according to any one of claims 1-3, wherein, At the beginning of the second time interval, the load current is limited to the first value (I1), and during the second time interval, the load current is limited to the second value (I2) by means of a predetermined change process.

6. The method according to any one of claims 1-3, wherein, During the second time interval, the load current is limited by a predetermined rated voltage variation process and the terminal voltage measured on the first load during the first time interval and / or the second time interval, according to the adjustment method.

7. The method according to any one of claims 1-3, wherein, When the level of the load current reaches the first value (I1) and / or the second value (I2) of the load current, a control signal for operating at least partially automated vehicles and / or an alarm signal for warning vehicle occupants are issued.

8. A computer program product comprising a computer program having instructions that, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 7.

9. An apparatus for limiting load current in a power supply line, comprising the computer program product according to claim 8.

10. A machine-readable storage medium having a computer program having instructions that, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 7.

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