Method for operating a lighting device of a motor vehicle and lighting device of a motor vehicle - Patents.com

Abstract

The present invention provides a method for operating a lighting device of a motor vehicle, the method comprising the steps of: preparing a first standby current profile; estimating a first standby power fall-down time associated with the first standby current profile; preparing a second standby current profile; estimating a second standby power fall-down time associated with the second standby current profile; powering a first light module with the first current profile resulting in a total current amount lower than the first standby current amount; and powering a second light module with the second current profile resulting in a total current amount higher than the second standby current amount.

Description

[Technical field]

[0001] The present invention relates to the field of lighting devices for motor vehicles, and more particularly to the temperature control of the light sources contained in these devices. [Background technology]

[0002] Digital lighting devices are increasingly being adopted by automakers in their mid- to high-end products.

[0003] These digital lighting devices typically include solid-state light sources whose operation is highly temperature dependent.

[0004] Temperature control in these devices is a very sensitive aspect and is usually performed by reducing the power, which means reducing the value of the current supplied to the light source, so that the output luminous flux and the operating temperature are reduced accordingly. This causes that to face this overheating problem, the performance of the light source must be too high, so that the operating values ​​can be reduced while still maintaining acceptable values.

[0005] It is very difficult to maintain optimal performance of a headlamp regardless of the driving situation. Very often, one lighting module gets hotter than the others, thus putting the remaining lighting modules at a disadvantage due to the high internal temperature of the HL. This phenomenon is not optimal because, if one light module is subjected to derating, the remaining modules are also affected in order to ensure an acceptable uniformity (even though in fact they have not yet reached the derating threshold).

[0006] This problem has been anticipated before, but solutions have been given for it. Summary of the Invention

[0007] The present invention provides an alternative solution for managing the temperature of light sources in a motor vehicle lighting device by means of a method for operating a motor vehicle lighting device and a motor vehicle lighting device according to the invention. Preferred embodiments of the invention are defined in the respective dependent claims.

[0008] Unless otherwise defined, all terms used herein (including technical and scientific terms) should be interpreted as is customary in the art. Furthermore, general usage terms should also be interpreted as is customary in the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0009] In this text, the term "comprises" and its derivatives (e.g. "comprising") are not to be construed in an exclusive sense, i.e., these terms are not to be interpreted as excluding the possibility that what is being described or defined may include additional elements, steps, etc.

[0010] In a first inventive aspect, the present invention provides a method for operating a lighting device for a motor vehicle comprising at least a first light module and a second light module, each light module comprising a solid-state light source, the method comprising: - preparing a first preliminary current profile for powering a first light module, the first preliminary current profile having a first average luminous flux value; - estimating a first reserve power reduction time associated with a first reserve current profile; - preparing a second preliminary current profile with a second average luminous flux value for powering a second light module; - estimating a second reserve power reduction time associated with the second reserve current profile, the second reserve power reduction time being greater than the first reserve power reduction time; - powering the first light module with a first current profile resulting in a luminous flux average value that is less than 0.96 times the first luminous flux average value; - powering the second light module with a second current profile resulting in a luminous flux average value that is greater than 1.04 times the second luminous flux average value; The present invention provides a method comprising:

[0011] The fact that the estimated second preliminary power-down time is longer than the first preliminary power-down time means that preliminary power-down times are estimated for both optical modules, and the first optical module is the one with the shorter power-down time and the second optical module is the one with the longer power-down time.

[0012] In the current state of the art, the preliminary power-down time of the first module compromises the performance of the entire lighting device, as it causes the second lighting module to undergo power-down even though it may not yet need it. However, in the method of the present invention, the power-down time of the second light module is shorter than the second preliminary power-down time, which causes the power-down time of the first light module to be extended. Thus, the overall power-down time is extended, providing better performance for a longer period while maintaining the uniformity of the luminous flux.

[0013] Due to the large variation in current profile, the difference in power falloff times between the light modules can be compensated for. This method is particularly advantageous when the difference between the estimated power falloff times is large.

[0014] In some specific embodiments, the first current profile and the second current profile include starting with an initial current value and increasing the current value when a predetermined condition is reached.

[0015] In this approach, the first and second current profiles are optimized to provide the minimum current required at each time (with the ability to increase the current if necessary).

[0016] In some particular embodiments, obtaining the initial current value is accomplished by a machine learning algorithm that obtains information from vehicle sensors.

[0017] The machine learning algorithm gets information from various sensors in the vehicle and is trained and tested in a variety of situations to obtain the maximum power reduction time for the less favorable light module.

[0018] This machine learning algorithm may be located in the cloud or embedded in the vehicle's controller.

[0019] In some particular embodiments, the vehicle sensors include at least some of the following: temperature sensors, vehicle speed sensors, global positioning sensors, and radar and / or lidar sensors.

[0020] In some particular embodiments, the predetermined condition includes the fact that the measured flux value is below a corresponding flux threshold value.

[0021] Although the luminous flux value is not the only parameter that gives information about the operation of the lighting device, it is an important parameter: controlling the current value with the luminous flux ensures an acceptable operation of the lighting modules as a whole.

[0022] In some particular embodiments, the invention further comprises the step of obtaining a light source temperature, and the predetermined condition comprises the fact that the light source temperature reaches a predetermined value.

[0023] A different but compatible way of controlling the current is by temperature, which can provide an indirect indication of the luminous flux.

[0024] In some particular embodiments, the predetermined condition includes the fact that a time limit has been reached.

[0025] Another way to control the current is by a timer only, estimating the evolution of the temperature with time. In this case, the current is automatically increased without the need to measure any data. This can be done if the time pattern is well established.

[0026] In some particular embodiments, the step of increasing the current value comprises increasing the current value from a first value to a second value, the second value being greater than the first value but less than 1.1 times the first value, particularly less than 1.05 times the first value, particularly less than 1.03 times the first value.

[0027] In these instances, the current may be increased within a narrow range, so that the current value (and temperature) is kept as low as possible while still providing acceptable performance.

[0028] In some particular embodiments, the method further comprises recording a series of current increments for the predetermined condition.

[0029] This sequence can be useful to avoid successive temperature measurements when using a time sequence pattern.

[0030] In some specific embodiments, the first light module is a low beam module and the second light module is a high beam module, and the low beam module and the high beam module may be activated simultaneously, which has a synergistic effect.

[0031] In some particular embodiments, each step of the method is applied to at least 10% of the light sources in the corresponding light module.

[0032] Incremental current increases may be applied to multiple light sources simultaneously (e.g., to all of the light sources that provide a given functionality), thus providing power savings and uniform performance across multiple elements.

[0033] In some particular embodiments, the method further comprises obtaining a light source temperature, and when the light source temperature reaches a predetermined value, the remaining steps of the method are triggered.

[0034] The system does not need to constantly manage temperature and power reduction times. Creating temperature thresholds helps the system become more relaxed, lowering power consumption.

[0035] In some specific embodiments, the first current profile provides a luminous flux average value that is less than 0.94 times the first luminous flux average value, more particularly less than 0.91 times the first luminous flux average value, and the second current profile in turn provides a luminous flux average value that is greater than 1.06 times the second luminous flux average value, more particularly greater than 1.09 times the first luminous flux average value.

[0036] These values ​​(which may compromise the uniformity of the projected light pattern) result in surprising power decay times. In some cases thermal stabilization may be achieved.

[0037] In some particular embodiments, estimating the first and / or second preliminary power reduction times is performed using an artificial intelligence algorithm that has been previously trained on a training data set. In some particular embodiments, the artificial intelligence algorithm includes a question tree structure with a number of questions, the answers to which result in a final score that is converted into a power reduction time value.

[0038] This type of approach uses a training data set, which is a collection of experimental data on different parameters, such as temperature measurements (external temperature, estimated temperature, from thermistors placed around the luminaire...), vehicle speed, road conditions, weather, day / night, other active lighting functions, thermal control parameters (LED dimming, derating in other modules, fan speed) and physical headlamp parameters. These values ​​are correlated with experimentally known values ​​of the derating time. Using the given parameters, the controller is trained to accurately estimate the derating time. As a result, when faced with real-life situations, the estimation of the actual derating time is as accurate as possible.

[0039] In some particular embodiments, the artificial intelligence algorithm includes a ridge regression algorithm.

[0040] The use of the ridge regression algorithm is advantageous for the following reasons: the data used in this method suffers from multicollinearity: there is a direct link between the behavior of some of the parameters used in the method (e.g., the activated lighting functions, durations, and temperature measurements of each module). Also, the heat in one light module has a direct effect on the evolution of the temperature in other light modules. A lighting pattern may be assembled using various modules. The derating times of the various modules then affect the derating of the lighting functions. In the case of multicollinearity, the least squares estimation method is unbiased but has a high variance and may introduce a significant estimation (prediction) error. The ridge regression algorithm allows to add a degree of bias to the regression estimation method, thereby reducing the standard error.

[0041] In some particular embodiments, the steps of powering the first light module with the first current profile and powering the second light module with the second current profile are not simultaneous, but rather the powering with the first current profile is performed first and then after a time interval the powering with the second current profile is performed next.

[0042] This aids in a more favorable power down time by delaying the action of increasing current until needed.

[0043] In a second aspect, the present invention provides a method for producing a composition comprising: - a first optical module comprising a plurality of solid-state light sources; - a second optical module comprising a plurality of solid-state light sources; - control elements for carrying out the steps of the method according to the first aspect of the invention; The present invention provides a lighting device for an automobile, comprising:

[0044] The term "solid state" refers to light emitted by solid-state electroluminescence (solid-state electroluminescence), which uses semiconductors to convert electrical power into light. Compared to incandescent lighting, solid-state lighting produces less heat and dissipates less energy to produce visible light. The generally small bulk of solid-state electronic lighting devices makes them more resistant to shock and vibration than brittle glass tubes / bulbs or long, thin filament wires. They also eliminate filament evaporation, potentially extending the life of the light-emitting device. Some examples of these types of lighting have semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), or polymer light-emitting diodes (PLEDs) as the light source, rather than electric filaments, plasmas, or gases.

[0045] This lighting device provides the advantageous functionality of efficiently managing the performance of the light source.

[0046] In some particular embodiments, the automotive lighting device further comprises a thermistor intended to measure the temperature of the solid-state light source. [Brief description of the drawings]

[0047] [Figure 1] 1 is a schematic perspective view of a lighting device for a motor vehicle according to the present invention; [Diagram 2] 4 is a graphical illustration of the standard operation of two light modules of a lighting device when the method according to the invention is not applied. [Diagram 3] FIG. 4 shows the evolution of the luminous flux vs. temperature curves of the first and second modules when operating according to the method of the invention. [Figure 4] FIG. 4 illustrates the effect of temperature over time produced by the method described in FIG. 3. [Diagram 5] Diagram showing a specific example of how the system is trained and tested.

[0048] In these figures the following reference symbols are used: [Explanation of symbols]

[0049] 1 First Optical Module 2 Second optical module 3 LED 4. Control Elements 5 Thermistor 6 Temperature Range 7 Temperature Activation Value 10. Lighting Equipment 11 First preliminary curve for the first module 11' Invention curve for the first module 12 First preliminary curve for the second module 12' Inventive curve for the second module 13 First preliminary current profile 14 First Corrected Current Profile 21 First preliminary derating temperature for first module 21' Inventive power reduction time for the first module 22 Second preliminary de-rating temperature for second module 22' Inventive power reduction time for second optical module 23 Second preliminary current profile 24 Second modified current profile 100 Motor Vehicles DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] The exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement and practice the systems and processes herein. It is important to understand that the embodiments may be provided in many alternative forms and should not be construed as being limited to the examples set forth herein.

[0051] Thus, while the embodiments may be modified in various ways and may take various alternative forms, specific embodiments thereof are shown by way of example in the drawings and are described in detail below. There is no intention to limit the invention to the particular forms disclosed. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the appended claims.

[0052] FIG. 1 shows a schematic perspective view of a lighting device for a motor vehicle according to the invention. The lighting device 10 is installed in an automobile 100, a first optical module 1 comprising a number of LEDs 3; a second optical module 2 comprising a number of LEDs 3; - a control element 4; a number of thermistors 5 intended to measure the temperature of various parts of the first and second optical modules; It is equipped with:

[0053] Each of the optical modules is a high-resolution module having a resolution of more than 2000 pixels, although there is no limitation on the technology used to manufacture the projection modules.

[0054] A first example of this matrix configuration includes a monolithic light source. The monolithic light source includes a matrix of monolithic electroluminescent elements arranged in rows and columns. In the monolithic matrix, each electroluminescent element can be grown from a common substrate and is electrically connected to selectively activate either individually or a subset of the electroluminescent elements. The substrate can be made primarily of a semiconductor material. The substrate can also include one or more other materials, such as non-semiconductor materials (metals and insulators). Thus, each electroluminescent element or each group of electroluminescent elements can form a light pixel and thus emit light when the material of the element is powered. Such a monolithic matrix configuration allows the selectively illuminable pixels to be located much closer to each other than a group of conventional light emitting diodes intended to be soldered to a printed circuit board. The monolithic matrix may comprise electroluminescent elements having a major height dimension of approximately 1 micrometer measured perpendicular to the common substrate.

[0055] The monolithic matrix is ​​coupled to a control center to control the generation and / or projection of the pixelated light beam by the matrix arrangement, such that the control center can individually control the light emission of each pixel of the matrix arrangement.

[0056] Alternatively to the one presented above, the matrix arrangement may comprise a primary light source coupled to a matrix of mirrors. A pixelated light source is thus formed by the assembly of at least one primary light source formed by at least one light-emitting diode that emits light and an array of photoelectric elements that directs the light rays from the primary light source by reflection towards the projection optics. The array of photoelectric elements is for example a matrix of micromirrors, also known by the acronym DMD for "Digital Micro-mirror Device". An auxiliary optical element, if appropriate, is able to collect the light rays of the at least one light source so as to concentrate them and direct them towards the surface of the micromirror array.

[0057] Each micromirror can be rotated between two defined positions, a first position where each light ray is reflected towards the projection optical element and a second position where each light ray is reflected in a direction different from the projection optical element. The two defined positions are oriented in the same way for all micromirrors and form a specific angle with respect to a reference plane supporting the matrix of micromirrors, defined by the specifications of the matrix of micromirrors. Such an angle is generally less than 20° and may typically be about 12°. Thus, each micromirror reflecting a part of the light beam incident on the matrix of micromirrors constitutes an elementary light emitter of the pixelated light source. The activation and control of the change in position of each mirror in order to selectively activate this elementary light emitter to emit or not emit an elementary light beam is controlled by a control center.

[0058] In different embodiments, the matrix arrangement may comprise a scanning laser system in which a laser source emits a laser beam towards a scanning element configured to probe a surface of the wavelength converter with the laser beam, an image of which is captured by the projection optics.

[0059] The scanning element's scanning speed can be accomplished at a high enough rate that the human eye does not perceive any displacement of the projected image.

[0060] The synchronous control of the activation of the laser light source and the scanning movement of the beam allows the generation of a matrix of elementary luminescent elements on the surface of the wavelength conversion element that can be selectively activated. The scanning means can be a movable micromirror for scanning the surface of the wavelength conversion element by reflection of the laser beam. The micromirror mentioned as the scanning means is, for example, of the MEMS type, which stands for "Micro-Electro-Mechanical Systems". However, the invention is not limited to such a scanning means, and other types of scanning means can be used, such as a series of mirrors arranged on a rotating element, the rotation of which causes the scanning of the transmission surface by the laser beam.

[0061] In another variation, the light source may be complex and include both at least one segment of a light element (such as a light emitting diode) and a surface portion of a monolithic light source.

[0062] With so many light sources in such close proximity to one another, thermal control is extremely important to ensure good performance and efficiency.

[0063] FIG. 2 shows a graphical illustration of the standard operation of two light modules of a lighting device, when the method according to the invention is not applied.

[0064] According to this figure, the first optical module increases in temperature over time according to a first curve 11. When a first preliminary power-down time 21 is reached, the first optical module reaches a maximum temperature threshold 6 and needs to be power-downed to avoid damage.

[0065] Analogously, the second light module (if installed alone) would increase in temperature over time according to the second curve 12. When the second power-down time 22 was reached, the second light module would have reached the maximum temperature threshold 6 and would need to be power-downed to avoid damage. In reality, since the second light module is installed together with the first light module (which has a shorter power-down time), it would need to be power-downed at the first power-down time, which occurs before the second power-down time, to ensure beam uniformity and to comply with regulations, which do not allow using the high beam module without activating the low beam module.

[0066] FIG. 3 shows the evolution of the luminous flux vs. temperature curves of the first and second modules when operating according to the method of the invention.

[0067] When a predetermined temperature 7 is reached in a first optical module, which follows a reserve current profile 13, the method of the invention is triggered and a first reserve power-down time is estimated. A specific example of this estimation will be illustrated in FIG.

[0068] A second reserve power down time is likewise estimated according to the method when the second module, now following the reserve current profile 23, is triggered.

[0069] In a real scenario, the module with the longer reserve power down time would be considered the second optical module.

[0070] When the method is activated, the current profile of the first light module is switched to a current profile 14 which results in a luminous flux average value that is 0.9 times the luminous flux average value that the first light module had before the method was activated. The current profile of the second light module is now switched to a current profile 24 which results in a luminous flux average value that is 1.1 times the luminous flux average value that the second light module had before the method was activated.

[0071] The current profile of the first module may be ramped down first, and the current profile of the second module may be ramped up when the total luminous flux of the light pattern reaches a prescribed low threshold. Even in this scenario, the power ramp down time is improved.

[0072] These changes have a negative impact on the uniformity of the resulting light pattern, but are implemented to keep the total luminous flux maintained. Such a substantial current drop may significantly extend the power drop time of the second module to achieve thermal stabilization.

[0073] It can be noticed in this figure how the current profile does not imply a constant current value but rather slight variations: a reference value is chosen and then the intensity may be increased slightly to keep the flux average value satisfying the conditions of the method described above.

[0074] FIG. 4 shows the effect of temperature over time produced by the method described in FIG.

[0075] In this graph the temperature over time for both optical modules is shown. The upper part of the graph shows the evolution for the first optical module. If no decision was made (as shown in FIG. 2), the first curve 11 would result in a first power reduction time 21 and the second curve 12 would result in a power reduction time 22.

[0076] However, by deciding to increase or decrease the luminous flux average value in each lighting module, the first module follows the modified curve 11' instead of the first curve 11, and the second module follows the modified curve 12' instead of the second curve 12. The first module reaches the temperature threshold 6 at the modified ramp-down time 21' instead of the first ramp-down time 21, and the second module reaches the temperature threshold 6 at the modified ramp-down time 22' instead of the second ramp-down time 22. Since the ramp-down time of the overall function is the shorter of the first ramp-down time and the second ramp-down time, the first ramp-down time, which is always shorter than the second ramp-down time, determines the ramp-down time of the lighting function. The overall ramp-down time of the lighting function is improved because it is improved from the first ramp-down time 21 to the modified ramp-down time 21'.

[0077] Figure 5 shows a specific example of how the system is trained and tested. Different examples with different training data sets are given. Each example includes a typical driving period during which different parameters are measured over time: temperature measurements (external temperature, estimated temperature, from thermistors placed around the luminaire...), vehicle speed, road conditions, weather, day / night, different active lighting functions, thermal control parameters (LED dimming, power reduction in different modules, fan speed) and physical headlamp parameters. Each of these data sets is associated with known experimental values ​​of the power reduction time. These values ​​are introduced into the system and the controller estimates the power reduction time. The estimated power reduction time is compared to the experimental one and the error is calculated.

[0078] Therefore, each training data set is associated with an error value, and a ridge regression algorithm is used to generate control rules that are applied to the controller to improve the estimation of the power reduction time due to multicollinearity between various values ​​and parameters.

Claims

1. 1. A method for operating a lighting device (10) for a motor vehicle comprising at least a first light module (1) and a second light module (2), each light module comprising a solid-state light source (3), comprising: - preparing a first preliminary current profile (11) with a first luminous flux average value for powering said first light module (1); - estimating a first preliminary power reduction time (21) associated with said first preliminary current profile (11); - preparing a second preliminary current profile (12) with a second average luminous flux value for powering said second light module (2); - estimating a second reserve power reduction time (22) associated with said second reserve current profile, said second reserve power reduction time being longer than said first reserve power reduction time (21); - powering said first light module (2) with a first current profile (11') resulting in a luminous flux average value lower than 0.96 times said first luminous flux average value; - powering said second light module (2) with a second current profile (12') resulting in a luminous flux average value higher than 1.04 times said second luminous flux average value; Equipped with The method, wherein the first current profile (11') and the second current profile (12') include starting with an initial current value and increasing the current value when a predetermined condition is reached.

2. The method of claim 1 , wherein obtaining the initial current value is performed by a machine learning algorithm that obtains information from vehicle sensors.

3. A method as described in claim 1 or 2, further comprising a step of obtaining a temperature of the solid-state light source, and each of the remaining steps of the method is triggered when the temperature of the solid-state light source reaches a predetermined value.

4. The method according to any one of claims 1 to 3, wherein the first current profile (11') results in a luminous flux average value that is lower than 0.94 times the first luminous flux average value.

5. The method according to any one of claims 1 to 4, wherein the second current profile (12') results in a luminous flux average value that is higher than 1.06 times the second luminous flux average value.

6. 6. The method of claim 1, wherein the estimation of the first and / or second reserve power reduction times is performed using an artificial intelligence algorithm that has been previously trained on a training data set.

7. The method of claim 6 , wherein the artificial intelligence algorithm comprises a ridge regression algorithm.

8. 8. The method according to claim 1, wherein the steps of powering the first light module (2) with the first current profile (11') and powering the second light module (2) with the second current profile (12') are not simultaneous, but rather the powering with the first current profile is performed first and then, after a certain time interval, the powering with the second current profile is performed next.

9. 9. The method according to claim 1, wherein the first light module is a low beam module and the second light module is a high beam module.

10. The method according to claim 1 , wherein each step of the method is applied to at least 10% of the solid-state light sources in the corresponding light module.

11. a first optical module (1) comprising a number of solid-state light sources (3), a second optical module (2) comprising a number of solid-state light sources (3), - a control element (4) for carrying out the steps of the method according to any one of claims 1 to 10; A lighting device for a motor vehicle comprising:

12. 12. A lighting device for a motor vehicle according to claim 11, further comprising a thermistor (5) intended to measure the temperature of the solid-state light source.

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