Method for determining current-voltage characteristics of a lighting device, control device, lighting device and motor vehicle

Abstract

Method for determining several current-voltage characteristics (18), each of which is assigned to one of several lighting units (11) of a lighting device (2) of a motor vehicle (1), wherein, in order to determine the current-voltage characteristics (18), either an electric current with changing current intensities is applied to each of the lighting units (11), wherein for each current intensity a corresponding voltage intensity of the resulting electric voltage is recorded, or an electric voltage with changing voltage intensities is applied, wherein for each voltage intensity a corresponding current intensity of the resulting electric current is recorded, wherein, in order to determine the current-voltage characteristics (18) of at least two of the lighting units (11), either the current with oppositely changing current intensities or the voltage with oppositely changing voltage intensities is applied simultaneously.

Description

The present invention relates to a method for determining several current-voltage characteristics, each of which is assigned to one of several lighting units of a lighting device of a motor vehicle, wherein, in order to determine the current-voltage characteristics, either an electric current with changing current intensities is applied to the lighting units, wherein for each current intensity an associated voltage intensity of the resulting electric voltage is detected, or an electric voltage with changing voltage intensities is applied, wherein for each voltage intensity an associated current intensity of the resulting electric current is detected. Lighting systems, particularly headlights, in modern motor vehicles typically include drivers or control units that control individual lighting units to generate different lighting modes or functions, producing varying levels of brightness and / or illumination areas. This often involves comparing the current and voltage values ​​of the respective lighting units with stored current-voltage characteristic curves. This serves to detect faults, for example, because the failure of individual lighting units or light sources within the units can lead to a deviation between the measured values ​​and the values ​​expected based on the current-voltage characteristic curve. To obtain the current-voltage characteristics, a learning process is often performed during the commissioning of the respective lighting device. In this process, the lighting units are subjected to different currents to determine these characteristics, and the corresponding voltage is recorded. The resulting pairs of values ​​each comprise a value for the current and a value for the corresponding voltage. These pairs of values ​​can be used to determine the characteristics or as the characteristics themselves. Such a procedure is described in DE 10 2023 107 021 B3. Further technological background to the invention can be found in DE 10 2091 124 560 A1, DE 10 2018 202 265 A1, and DE 10 2022 115 951 A1. The present invention aims to provide an improved concept in connection with the learning process described above. According to the invention, this problem is solved in a method of the type mentioned at the outset by simultaneously applying either the current with opposing current intensities or the voltage with opposing voltage intensities to at least two of the lighting units in order to determine their current-voltage characteristics. Consequently, the present invention comprises two embodiments. In the first embodiment according to the invention, an electric current with opposing current intensities is applied to the lighting units to determine the current-voltage characteristics, and the corresponding voltage of the resulting electric current is recorded for each current intensity. In the second embodiment according to the invention, an electric voltage with opposing voltage intensities is applied to the lighting units to determine the current-voltage characteristics, and the corresponding current of the resulting electric current is recorded for each voltage intensity. Where specific reference is made below to one of these two embodiments according to the invention, the aspects explained accordingly apply equally and analogously to the other embodiment. The inventive method results in a reduction of the time required for the learning process. The application of the respective current or voltage to the lighting units does not occur sequentially, but rather simultaneously for at least two of the lighting units. Furthermore, excessively high power values ​​are avoided with regard to the total power dissipated by the lighting units during the learning process, since opposing values ​​are provided for the simultaneous generation of the current or voltage levels in at least two of the lighting units.This is particularly advantageous because a control device by means of which the learning process is carried out or the current or voltage is generated is typically limited in terms of the power that can be implemented, so that the risk of excessive power occurring, which could arise due to the simultaneous application of the current or voltage to the lighting units, is avoided or reduced. It is provided that the respective current or voltage is applied simultaneously to at least two of the lighting units to determine the current-voltage characteristics. Thus, at least one time interval can be provided during the learning process, during which the respective current or voltage is applied to both one of the lighting units and at least one other lighting unit. Preferably, the respective current or voltage is applied simultaneously to exactly two of the lighting units, particularly since the risk of exceeding the maximum permissible power increases when more than two lighting units are affected.However, it is also conceivable that the respective current or voltage is applied to more than two of the lighting units simultaneously, whereby the respective current or voltage levels are applied to at least two of these lighting units with opposingly changing values. Furthermore, it is provided that the current or voltage values ​​of at least two of the lighting units, which are simultaneously supplied with the respective current or voltage, behave in opposite directions. Thus, the current or voltage values ​​present at at least one of the first lighting units can increase over time, while the current or voltage values ​​present at at least one of the second lighting units decrease over time, or vice versa. This opposing behavior can occur at least during the time interval in which the learning process is carried out. The values ​​increasing over time can, in particular, increase monotonically, and the values ​​decreasing over time can, in particular, decrease monotonically.Especially with continuously changing values, a difference quotient and / or gradient of the values ​​increasing over time can be positive, and a difference quotient and / or gradient of the values ​​decreasing over time can be negative. To determine the current-voltage characteristic curves, an electric current or voltage is applied to the respective lighting units, with the current or voltage values ​​changing successively. For several of these values, and especially for each one, a value is read back or measured that corresponds to the other quantity, i.e., the resulting voltage or current that occurs at that particular current or voltage. This allows for the generation of multiple pairs of values, particularly numerical pairs, which indicate the corresponding voltage value for each current value, or vice versa. The measured values ​​themselves can be used to represent the current-voltage characteristic curve. The current-voltage characteristic curve can also be determined from these values.A function term, such as a linear, exponential, or spline function, can be approximated to the values, for example, by means of a regression analysis, in particular a fit. The characteristic curves can be saved and stored, for example, on a storage medium of a control device, and retrieved as needed, especially for carrying out the error detection described above. Consequently, determining the current-voltage characteristics is preferably carried out during the initial commissioning of the lighting system. Alternatively, or in addition, it is conceivable that determining the current-voltage characteristics is carried out during maintenance of the lighting system or, more generally, the vehicle, particularly if it is expected that the current-voltage characteristics could change during the service life of the lighting system. The lighting units preferably each comprise at least one light source. It is conceivable that light with variable brightness and / or variable color can be generated by means of the at least one light source. Different operating power levels are implemented by means of the respective light source when generating different brightness levels. The at least one light source can be at least one light-emitting diode (LED), which can in particular also be at least one organic light-emitting diode (OLED). The at least one LED can be at least one single-color or multi-color LED. Preferably, the lighting units each comprise several separate light sources, in particular between five and several thousand. In a simple case, the entirety of several light sources is understood as at least one of the lighting units. It is also conceivable that at least one of the lighting units comprises further components and optionally forms a structural unit. For example, at least one of the lighting units can have a mounting plate that supports the at least one light source. The mounting plate can be a printed circuit board that serves for the electrical contacting of the at least one light source. An electrical connection to the control device and / or a current and / or voltage source can be established by means of the electrical contacting. Several mounting plates can be arranged next to each other, for example within a plane. The light sources can be arranged behind a transparent disc of a housing of the lighting device. Preferably, the lighting units comprise several light sources connected in series. Particularly in such a configuration, a fault, such as the failure of at least one of the light sources, causes a change in the voltage present at a given current, or vice versa, which can be determined, especially theoretically. Thus, for fault detection, the respective current-voltage characteristic curve can be used to check whether a deviation between the actual voltage or current values ​​and the values ​​expected according to the characteristic curve is at least as large as this change. In this case, a malfunction in the affected lighting unit can be assumed. The number of failed light sources can also be determined based on the actual voltage. Preferably, the current or voltage levels change incrementally and / or continuously, or in other words, uniformly, when the current or voltage is applied simultaneously to at least two of the lighting units. Thus, the applied current or voltage levels can change from a maximum value to a minimum value or vice versa. This change can have a constant rate of change, so that, in the case of incremental change, equal change steps are provided, or, in the case of continuous change, a linear change profile is provided. With regard to incremental change, a corresponding value for the resulting voltage or current level can be recorded for each step. The number of steps can be between five and 100, for example, ten.Regarding the continuous change, a corresponding value for the resulting voltage or current can be recorded at discrete points in time, and continuous recording of these values ​​is also conceivable. It is conceivable that, when the current or voltage is applied simultaneously to at least two of the lighting units, the current or voltage changes in such a way that a value, particularly one that is constant over time, relating to the sum of the power dissipated by the lighting units does not exceed a predetermined limit for this sum. The sum of the powers can therefore be at least substantially constant over time. The constant sum can correspond to the limit or to a value that is less than the limit. In particular, the sum can be a maximum of 90% of the limit. Preferably, the current or voltage is applied simultaneously to at least two of the lighting units by means of a generating unit. This unit can be or include the control unit, which in particular implements the driver of the lighting device. The generating unit can be connected to a current and / or voltage source, such as a vehicle battery, like a high-voltage or low-voltage battery. Specific current or voltage levels can be selectively applied to the respective lighting units by means of the generating or control unit. It is conceivable that the limit corresponds to a power limit of the generating unit. The generating unit can therefore be configured to convert power with a maximum power value, where the maximum power value is the power limit. The lighting system can implement several lighting functions. These lighting functions can be designed for specific situations. For example, it is conceivable that, based on control commands generated during vehicle operation, at least one of the lighting functions is selected and then implemented. The lighting functions could include position lights, daytime running lights, turn signals, low beams, high beams, taillights, brake lights, and / or reversing lights. It is also conceivable that at least one of the lighting units could implement a lighting function specifically designed for that unit. Preferably, it is provided that only certain combinations of lighting functions can be implemented during the operation of the motor vehicle. It is conceivable that, during normal operation, not all intended lighting functions are ever implemented simultaneously, particularly since certain lighting functions are mutually exclusive, such as the low beam and high beam functions. The maximum power limit can be defined as the power dissipated when implementing the combination of lighting functions that delivers the maximum power across all possible combinations. The maximum power limit of the generating unit, i.e., the maximum power, is therefore the maximum power dissipated during normal operation of the lighting system. Normal operation can be understood as driving.The maximum power output is therefore preferably lower than a theoretical maximum power output that can be generated by the lighting device, for example in the case of maximum power generation by all light sources or lighting units. Furthermore, the present invention relates to a control device, the object of which is achieved in that the control device is configured to generate control signals for carrying out the method according to the preceding description. All advantages, features, and aspects explained in connection with the method according to the invention are equally transferable to the control device according to the invention and vice versa. The control device can be a driver of the lighting device. The control device can comprise a computer-readable storage medium and a processing device, the storage medium comprising instructions implementing software which, when executed by the processing device configured as a computer, cause it to perform the steps of the procedure according to the preceding description. The control unit is configured to generate and output control signals, whereby the control signals specifically cause the application of current or voltage to the lighting units and the reading back of the resulting voltage or current values. The current-voltage characteristics determined in this process can be stored by the control unit, particularly by the storage medium, especially as lookup tables. The control unit can also be configured to perform the steps for fault detection described above. Furthermore, the present invention relates to a lighting device for a motor vehicle, comprising several lighting units and at least one control device according to the preceding descriptions. All advantages, features, and aspects explained in connection with the method and / or the control device according to the invention are equally transferable to the lighting device according to the invention, and vice versa. The lighting device can be a headlight. For example, the vehicle may be equipped with two headlights, one positioned at the front left and one at the front right. Alternatively, the headlight can be an illuminated front panel mounted on the front of the vehicle, extending at least substantially across its entire width. The headlight can perform at least some of the aforementioned lighting functions, such as generating a position light (especially white), daytime running light (especially white), flashing light (especially yellow, orange, or red), low beam headlight (especially white), and / or high beam headlight (especially white). The lighting device can be a rear light. Thus, two rear lights can be provided on the motor vehicle, one of which can be located at the rear left and one at the rear right. At least some of the aforementioned lighting functions can be implemented by means of the rear light, for example, to produce a position or tail light, in particular red, and / or a brake light, in particular red, and / or a reversing light, in particular white, and / or a flashing light, in particular yellow, orange, or red. The lighting device can be a side light. For example, two side lights can be provided on the motor vehicle, one on the left side and one on the right. At least some of the aforementioned lighting functions can be achieved by means of the side light, such as producing a position light, particularly white, and / or a flashing light, particularly yellow, orange, or red. The lighting device may comprise a housing within which the lighting units or the components of the lighting units are arranged. The housing may be transparent on at least one side or may have a transparent panel, so that the light generated by the lighting units exits through this side onto the respective lighting unit. Finally, the present invention relates to a motor vehicle comprising at least one control device according to the above descriptions and / or at least one lighting device according to the preceding descriptions. All advantages, features, and aspects explained in connection with the inventive method and / or the inventive control device and / or the inventive lighting device are equally transferable to the motor vehicle according to the invention, and vice versa. The vehicle may be equipped with a control unit configured to generate control commands, particularly those aimed at implementing the aforementioned lighting functions, and to output these commands to the control device, which is, in particular, the driver of the respective lighting device. The control commands may be generated by a user- or driver-side control system and / or by a vehicle control system, especially one that enables autonomous driving. Further advantages, features, and details of the present invention will become apparent from the exemplary embodiments described below and from the figures. These show schematically: Fig. 1: a schematic diagram of a motor vehicle according to an exemplary embodiment, comprising several lighting devices according to the invention, each with a control device according to the invention, each with reference to this motor vehicle, a method according to the invention according to an exemplary embodiment is explained; Fig. 2: a front view of one of the lighting devices of the motor vehicle of Fig. 1; Fig. 3: a schematic diagram of the lighting device of Fig. 2; Fig. 4: a diagram illustrating the application of electric current to the lighting units of the lighting devices as provided for in the method according to the invention; and Fig.5 : a diagram illustrating current-voltage characteristics of the lighting units determined within the framework of the method according to the invention. Fig. 1 shows a schematic diagram of a motor vehicle 1 according to an embodiment of the invention, comprising several lighting devices 2 according to the invention, each according to an embodiment, wherein a method according to the invention is carried out in the motor vehicle 1 and by means of the lighting devices 2 according to an embodiment. Two of the lighting devices 2 each realize a front headlight 3, two of the lighting devices 2 each realize a rear headlight 4, and two of the lighting devices 2 each realize a side light 5. Aspects relating to the lighting device 2 that is the front headlight 3 arranged at the front left of the motor vehicle 1 are explained below. Everything explained below regarding this lighting device 2 applies in principle equally to the other lighting devices 2. Fig. 2 shows a view from the front and Fig.3 a schematic diagram of this lighting device 2 or of the section of the motor vehicle 1 which carries this front headlight 3. The motor vehicle 1 comprises a control unit 6, by means of which control commands for controlling the operation of the lighting devices 2 are generated. The control commands are generated by the driver or within the framework of a vehicle control system that enables autonomous driving operation of the motor vehicle 1. The control commands are received and evaluated by a control device 8 of the respective lighting device 2 according to the invention and provided in an exemplary embodiment, wherein the control device 8 implements a driver of the respective lighting device 2. The transmission of the control commands from the control unit 6 to the respective control device 8 takes place via a vehicle bus 7 designed as a CAN bus. The control commands are directed towards the implementation of lighting functions by means of the lighting devices 2. The front headlights 3 can be used to implement position light, daytime running light, turn signal, low beam, and high beam functions. The rear headlights 4 can be used to implement tail light, brake light, reversing light, and turn signal functions. The side lights 5 can be used to implement position light and turn signal functions. The lighting device 2 comprises a housing 9 in which its components are arranged. The housing 9 has a transparent disc 10 on one side, through which the light generated by the lighting device 2 exits. Lighting units 11 of the lighting device 2 are arranged inside the housing 9. Each lighting unit 11 has a carrier plate 12, which supports several light sources 13 connected in series. The carrier plate 12 is a circuit board that connects the respective light sources 13 to the control device 8, whereby components of the control device 8 can also be arranged on the carrier plate 12, in particular on the side of the respective carrier plate 12 facing away from the light sources 13. Light of different brightness and different colors can be generated by means of the light sources 13. The light sources 13 are each designed as a light-emitting diode (LED).The support plates 12 or the lighting units 11 are mosaic-like and arranged within one plane (see Fig. 2) behind the transparent disc 10. The control unit 8 is designed to generate control signals based on the control commands generated by the control unit 6. These signals ensure that the desired brightness and color are implemented to realize the respective lighting function. Specifically, the control signals ensure that the respective lighting unit 11 receives the electrical current corresponding to the desired brightness. The current and voltage required for this by the light sources 13 are supplied by a current and voltage source 14, which is designed to be a vehicle battery. To generate the control signals, the control device 8 comprises a computer-readable storage medium 15 and a processing device 16, wherein the storage medium 15 comprises software instructions 17 which, when executed by the processing device 16 (designed as a computer), cause the processing device 16 to generate the corresponding control signals. Furthermore, the instructions 17 executed by the processing device 16 cause control signals to be generated that initiate the execution of the steps of the method according to the invention, which will be explained in detail later. Another aspect to be implemented by means of the control device 8 is fault identification during the intended operation of the lighting device 2, i.e., during the operation of the motor vehicle 1, concerning the identification of lighting units 11 with failed light sources 13. For this purpose, a corresponding current-voltage characteristic curve 18 is stored in the storage medium 15 for each of the lighting units 11, which relates to the proper or fault-free operation of the respective lighting unit 11. The current-voltage characteristic curve 18 assigns values ​​for current intensities present at the respective lighting unit 11 to values ​​for voltage intensities resulting from fault-free operation.Instructions 17 are used to check whether there is currently a deviation between the actual values, particularly those measured, concerning the current and voltage present at the respective lighting unit 11 and the values ​​that would be expected according to the current-voltage characteristic curve 18 assigned to that lighting unit 11. If so, a fault or failure of one of the light sources 13 is inferred. In this case, the control unit 8 issues an error message to the driver, prompting them, for example, to visit a workshop. The steps of the inventive method according to the exemplary embodiment are explained below, wherein the method is aimed at performing a learning process for the control device 8 during initial commissioning of the lighting device 2 or the motor vehicle 1, or during maintenance of the lighting device 2. This learning process is aimed at determining the current-voltage characteristics 18, which are then stored and saved by the storage medium 15. The control unit 8 is configured to generate the control signals during the learning process such that an electric current with varying intensities is applied to the respective lighting unit 11, whereby a corresponding or resulting voltage is measured for each current intensity. This process is explained with reference to Fig. 4, which shows a diagram of these values. The abscissa 19 of the diagram shows the time during the learning process. The ordinate 20 shows, with respect to the bars in the diagram, the value or numerical value of the current and, with respect to the crosses x and circles o in the diagram, the value or numerical value of the corresponding voltage. The bars show the intended current profile for two of the lighting units 11. The bars with hatching consisting exclusively of parallel and non-intersecting lines refer to the first lighting unit 11, and the bars with hatching with intersecting lines refer to the second lighting unit 11. The resulting voltages for the first lighting unit 11 are marked by circles o, and for the second lighting unit 11 by crosses x. These resulting voltages are measured during the learning process. Although the bars assigned to the first and second lighting units 11 are drawn in pairs directly adjacent to each other, the current with its changing intensities is applied to these two lighting units 11 simultaneously, such that the intensities of these lighting units 11 change in opposite directions. Specifically, the intensities for the first lighting unit 11 decrease stepwise and uniformly, whereas the intensities for the second lighting unit 11 increase stepwise and uniformly. Uniformly means that the stepwise changes in the intensities are of the same magnitude. Regarding simultaneity, it is also conceivable that at least one other of the lighting units 11 is energized during this time period and thus simultaneously for the purpose of determining the corresponding current-voltage characteristic curve 18. The resulting current-voltage characteristic curves 18 of these two lighting units 11 are shown in Fig. 5, which depicts a diagram of these current-voltage characteristic curves 18. The abscissa 21 represents the current value, and the ordinate 22 represents the corresponding voltage value. The pairs of numbers or values ​​23 obtained during the learning process each comprise a value for the current and a value for the resulting voltage. These pairs of values ​​23 are marked in Fig. 5, analogous to Fig. 4, by means of circles o and crosses x. Further aspects of the counter-current supply to the lighting units 11 are explained below with reference to Fig. 4. This supply is such that the sum of the power dissipated by the lighting units 11 does not exceed a predetermined limit. A corresponding current value is indicated in Fig. 4 by a dashed horizontal line 24. This sum remains constant during the learning process. A corresponding current value is indicated in Fig. 4 by a solid horizontal line 25. With regard to the limit value, it is provided that the lighting units are powered by a generating unit 26, which in this case is the control unit 8, whereby the limit value is a maximum power limit of the generating unit 26, i.e. the maximum power that can be converted by the generating unit 26. Another relevant aspect in this regard is that only certain combinations of lighting functions can be implemented during the operation of the vehicle 1. Thus, during the intended operation of the vehicle 1 or the lighting devices 2, not all conceivable lighting functions are ever implemented simultaneously, since the simultaneous implementation of certain lighting functions is not practical or may even be impossible, as is the case, for example, with the low beam and high beam functions. Against this background, the maximum power output is defined as the total power output of the lighting device 2 that occurs when implementing the combination of lighting functions that delivers the highest possible power output across all possible combinations. Reference is now made again to Fig. 5. Although the value pairs 23 can themselves be used as the current-voltage characteristic curves 18, these are determined here using the value pairs 23. For this purpose, a function term, in this case an example of a linear function, is approximated to the value pairs 23 of each of the lighting units 11 by means of a regression analysis or a fit, whereby the mathematical relationship of these lines, i.e. the function term together with the determined fit parameters, is stored as the current-voltage characteristic curves 18. In the previously described embodiment, the current is provided as the variable parameter for the operation of the lighting units 11, which can be controlled by the control device 8, and the corresponding voltage is automatically determined accordingly. However, the reverse case is also conceivable within the scope of the present invention, in which the voltage is provided as the parameter controllable by the control device 8 and the corresponding current is automatically determined accordingly. In this case, the word "voltage" should be replaced by "current" and vice versa in the preceding description.

Claims

Method for determining several current-voltage characteristics (18), each of which is assigned to one of several lighting units (11) of a lighting device (2) of a motor vehicle (1), wherein, in order to determine the current-voltage characteristics (18), either an electric current with changing current intensities is applied to each of the lighting units (11), wherein for each current intensity an associated voltage intensity of the resulting electric voltage is recorded, or an electric voltage with changing voltage intensities is applied, wherein for each voltage intensity an associated current intensity of the resulting electric current is recorded, characterized in that, in order to determine the current-voltage characteristics (18), at least two of the lighting units (11) are simultaneously subjected to either the current with opposing current intensities or the voltage with opposing voltage intensities. Method according to claim 1, characterized in that the determination of the current-voltage characteristics (18) is carried out as part of an initial commissioning or maintenance of the lighting device (2). Method according to claim 1 or 2, characterized in that the lighting units (11) each comprise several separate light sources (13), which are in particular light-emitting diodes. Method according to claim 3, characterized in that the lighting units (11) comprise several light sources (13) connected in series. Method according to one of the preceding claims, characterized in that the current or voltage intensities change stepwise and / or continuously when the current or voltage is applied simultaneously to at least two of the luminaire units (11). Method according to one of the preceding claims, characterized in that the current or voltage intensities change when the current or voltage is applied simultaneously to the at least two of the luminaire units (11) such that a value relating to the sum of the powers converted by means of the luminaire units (11) thereby does not exceed a predetermined limit value for this sum. Method according to claim 6, characterized in that the limit value corresponds to a power limit of a generating device (26) by means of which the simultaneous application of current or voltage to the at least two of the lighting units (11) takes place. Method according to one of the preceding claims, characterized in that several lighting functions can be implemented by means of the lighting device (2). Method according to claims 7 and 8, characterized in that only certain combinations of lighting functions can be realized during the operation of the motor vehicle (1), wherein the upper power limit is defined by the fact that it indicates the power that is implemented when realizing the combination of lighting functions in which the maximum power is implemented with respect to all possible combinations. Control device (8) which is configured to generate control signals for carrying out the method according to one of the preceding claims. Lighting device (2) for a motor vehicle (1), comprising several lighting units (11) and at least one control device (8) according to claim 10. Lighting device (2) according to claim 11, characterized in that it is a front headlight (3) or a rear headlight (4) or a side light (5). Motor vehicle (1) comprising at least one control device (8) according to claim 10 and / or at least one lighting device (2) according to claim 11 or 12 .

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