Dynamic adaptation of thermal protection of a matrix light source

Abstract

The invention relates to a method for adapting a thermal protection of a matrix light source of a vehicle lighting module comprising a plurality of individually controllable light elements, the method comprising the following steps:- determining (401) a photometry defining a light intensity value for each light element of the matrix light source;- adapting (402) the thermal protection of the matrix light source as a function of at least one piece of information derived from the determined photometry, an ambient temperature and / or regulatory constraints of a lighting function. FIG. 4

Description

Title of the invention: Dynamic adaptation of the thermal protection of a matrix light source

[0001] The present invention relates to the field of thermal protection of light sources of a lighting module, in particular for automotive lighting. The invention applies in particular, but not exclusively, to pixelated or matrix light sources, known as monolithic.

[0002] It is becoming increasingly common to use semiconductor light sources, such as light-emitting diodes, LEDs, to perform various lighting functions, for example in motor vehicles. The use of these small light sources with high brightness and low power consumption also makes it possible to produce original light contours in a compact system with reduced electrical energy.

[0003] It is now known to arrange several individually controlled light elements, in a matrix, within a single so-called matrix light source, and to integrate such a matrix source into a lighting module for a motor vehicle in order to be able to perform precise lighting functions. It is also possible to perform adaptive lighting functions, i.e. varying according to data from sensors placed in the vehicle, making it possible to adapt the lighting to the environment of the vehicle and / or to the driver's maneuvers.

[0004] Each light element, in operation, has a junction temperature, which corresponds to a temperature at a junction between two layers of semiconductors called a PN junction, well known in the field of lighting. The junction temperature, when it reaches high values, can lead to accelerated aging of the light element, or even to a breakdown of the PN junction leading to a failure of the light element.

[0005] In order to avoid such situations, thermal protection mechanisms for the light elements of a matrix light source are provided. Such thermal protection mechanisms may be based on measuring the junction temperature by means of a temperature sensor, or rather on estimating the junction temperature from a temperature value measured by a sensor located near the light element. When the measured or estimated junction temperature crosses a given threshold, a reduction in the light power of the source may be applied when controlling the light elements, which reduces the lighting power of the lighting module but makes it possible to preserve the light element(s) whose junction temperature has crossed the given threshold.

[0006] A so-called "monolithic" source can have a particularly high density of light elements, which makes it particularly interesting for a plurality of applications. A monolithic source involves a plurality of electroluminescent semiconductor elements with submillimeter dimensions, epitaxially grown directly on a common substrate, the substrate generally being formed of silicon. Unlike sources comprising conventional LED matrices, in which each elementary light element is an electronic component produced individually and mounted on a substrate such as a printed circuit, PCB, a monolithic source is to be considered as a single electronic component, during the production of which several areas of electroluminescent semiconductor junctions are generated on a common substrate, in the form of a matrix.This production technique allows for the production of electroluminescent areas, each acting as an elementary light element, very close to each other. The gaps between the light elements can have submillimeter dimensions. An advantage of this production technique is the high level of pixel density that can result on a single substrate.

[0007] The individual light elements can be individually controlled by a control module capable of receiving from a control module a lighting photometry to be carried out. The individual control can comprise the control of the electrical power supplied to the individual light element, by pulse width modulation, or PWM, for “Pulse Width Modulation” in English. The control module can for example be an integrated circuit of the ASIC type, for “Application Specific Integrated Circuit” in English, which has the advantage of great compactness, and which can be integrated into the monolithic light source.

[0008] The control module may further be capable of implementing a thermal protection mechanism for the monolithic matrix source. However, in the case of a monolithic matrix source, it is not possible to provide a temperature sensor for measuring or estimating the junction temperature of each light element, due to their small sizes and spacing, but also due to their number, which may exceed several thousand or even several tens of thousands of light elements.

[0009] Accordingly, one or more temperature sensors are placed at respective positions around the monolithic source, and a junction temperature at a given position of the source can be deduced from the temperatures measured by the sensor(s), by estimating a thermal resistance between the sensor position and the given position.

[0010] In ASIC type control modules, the thermal protection mechanism is implemented on the basis of thermal protection parameters, stored in a non-volatile memory of the ASIC, and loaded into one or more registers of the ASIC when it is powered on.

[0011] The thermal protection parameters include in particular at least one threshold value, which is compared to a measured temperature value, or to a temperature value obtained from measured temperature values, in order to operate or not a power reduction to protect the monolithic matrix light source.

[0012] Such a threshold value is determined from the thermal resistance between the position of the temperature sensor, or respective positions of temperature sensors, and the given position of the monolithic source for which the junction temperature is estimated. The thermal resistance is representative of the temperature difference between the temperature measured by a sensor and the temperature of the hottest pixel. Thus, the threshold value takes into account the fact that there is a downward shift between the measured temperature and the junction temperature of the hottest pixel.

[0013] However, the thermal protection parameters are defined in a fixed manner in the non-volatile memory of the control module, and the fixed parameters are applied regardless of the lighting photometry performed by the lighting module.

[0014] However, not only does the thermal resistance depend on the photometry produced by the lighting module, which can vary frequently, or even rapidly, but in addition the hottest pixel differs according to the photometry and its evolution, the hottest pixel corresponding to the electroluminescent element for which the junction temperature is the highest among all the respective junction temperatures of the electroluminescent elements of the monolithic source.

[0015] The lighting photometry can in particular vary at a frequency greater than 1 hertz, for example at a frequency of 60 photometries per second.

[0016] Furthermore, the thermal resistance may vary depending on the junction temperature of the hottest pixel, but also depending on environmental conditions such as ambient temperature.

[0017] Thus, a fixed threshold determined from a given thermal resistance value can alternatively underestimate the thermal resistance relative to the hottest point, or overestimate the thermal resistance relative to the hottest point, depending on the situation encountered.

[0018] If the fixed threshold is too low in a given situation, and thus overestimates the thermal resistance, the power reduction is applied too often, which deteriorates the quality of the lighting of the lighting module.

[0019] If the fixed threshold is too high in a given situation, and thus underestimates the thermal resistance, there is a risk of crossing a limit junction temperature for one or more pixels, beyond which the aging of the electro- corresponding luminescent is accelerated.

[0020] For example, in town, when the vehicle speed is low, the lighting beam is wide and the maximum power is low and distributed over the pixel matrix: the thermal resistance is therefore low, which indicates that a fixed threshold overestimates the thermal resistance in this situation. The reduction in light power will thus be carried out when it is not necessary, deteriorating the overall power of the beam.

[0021] On the contrary, on a motorway, the lighting beam is narrow and the maximum power is high, which implies that the thermal resistance is high between the hottest pixel and the temperature sensor(s). In this situation, a fixed threshold risks underestimating the thermal resistance, with a risk of crossing the limit junction temperature for one or more pixels before the thermal protection is activated, accelerating the aging of the monolithic matrix light source.

[0022] In addition, the fixed thermal protection parameters do not allow taking into account the evolution dynamics of the photometry controlled by the control module.

[0023] There is therefore a need for an improved control of the thermal protection of a matrix light source, especially a monolithic one, taking into account the dynamic nature of the parameters that influence the thermal resistance.

[0024] The present invention improves the situation.

[0025] A first aspect of the invention relates to a method for adapting the thermal protection of a matrix light source of an illumination module comprising a plurality of individually controllable light elements, the method comprising the following steps: - determining a photometry defining a luminous intensity value for each light element of the matrix light source; - adaptation of the thermal protection of the matrix light source as a function of at least one piece of information derived from the determined photometry, an ambient temperature and / or regulatory constraints of a lighting function.

[0026] Thus, the thermal protection is adapted from one or more parameters which evolve dynamically and which determine the thermal resistance. The precision associated with the thermal protection is thus improved, avoiding both the aging of the luminous elements of the source, but also an untimely triggering of the thermal protection.

[0027] According to embodiments, the thermal protection may comprise a reduction in light power emitted by the matrix light source as a function of a temperature value obtained from at least one temperature value measured by a sensor arranged in the lighting module.

[0028] Thermal protection thus makes it possible to limit the aging of the light elements of the matrix source.

[0029] In addition, the thermal protection can be determined from at least one thermal protection parameter, and the adaptation of the thermal protection can comprise the modification of at least one thermal protection parameter, called modified thermal protection parameter, among said at least one thermal protection parameter.

[0030] Thus, it is possible to dynamically change the thermal protection parameter(s), which makes it possible to dynamically adapt the conditions of application of the thermal protection, in particular as a function of variations in the thermal resistance.

[0031] In addition, said at least one thermal protection parameter may comprise one or more of the following parameters: - at least one temperature threshold value, in which the reduction of light power of the thermal protection is implemented if the temperature value obtained is higher than the temperature threshold value; - a thermal protection refresh rate, determining a frequency of updating the light power emitted by the matrix source to achieve the reduction in light power; and - a minimum light power level limiting the reduction in light power of the thermal protection.

[0032] It is thus made possible to precisely and dynamically adapt the thermal protection of the matrix light source.

[0033] Additionally or alternatively, the temperature value obtained from said at least one measured temperature value may be determined from several measured temperature values, and may be one of the following values: - the highest temperature value among the measured temperature values; - an average value of the measured temperature values; - the highest temperature value among a first average value of a first set among the measured temperature values ​​and a second average value of a second set among the measured temperature values.

[0034] It is thus made possible to improve the precision associated with the temperature value obtained which can estimate the junction temperature of the hottest pixel.

[0035] According to embodiments, the determined photometry can define a duty cycle value for a pulse width modulation control of each light element of the matrix light source, and said at least one information derived from the determined photometry can comprise one or more of the following derived information: - a maximum value among the values ​​of duty cycles defined by the determined photometry; - an average charge corresponding to an average of the duty cycle values ​​of the determined photometry; - a variation in average charge between the determined photometry and a previous photometry; - a position of a hottest pixel.

[0036] Such derived information directly influences the value of the thermal resistance and its rate of variation, which improves the precision associated with the implementation of thermal protection.

[0037] According to embodiments, the photometry can be determined from at least one input data among the following data: - data from at least one vehicle sensor, capable of obtaining data representative of the vehicle's external environment; - a command to activate and / or deactivate a lighting function received from a central control module of the vehicle; and / or - a steering angle received from the central control module.

[0038] Determining the photometry as a function of such input data makes it possible to perform lighting functions, in an adaptive manner in particular, as a function of the vehicle's environment and / or driver maneuvers.

[0039] According to a first embodiment, the method is implemented by a control module separate from a control module of the matrix light source integrated into the lighting module, the method further comprising the transmission of the determined photometry to the control module, and the adaptation of the thermal protection may comprise the modification, in the control module, of said at least one thermal protection parameter.

[0040] The first embodiment allows adaptation of thermal protection in existing ASIC type control modules, without requiring hardware modification.

[0041] According to a second embodiment, the method is implemented by a control module separate from a control module of the matrix light source integrated into the lighting module, the control module can obtain the temperature value obtained from the measured temperature values ​​and the thermal protection of the matrix light source can comprise the modification of the photometry determined to reduce the light power emitted by the matrix light source, as a function of the temperature value obtained, and further comprising the transmission, by the control module, of the modified photometry to the control module of the matrix light source.

[0042] The second embodiment allows the implementation of more precise and complex thermal protection in the control module, based on a greater number of thermal protection parameters in particular, without constraints linked to existing thermal protections in the light source control modules.

[0043] According to embodiments, the light elements of the matrix light source may be of submillimeter dimensions and may be epitaxially grown directly on a common substrate.

[0044] The present invention is particularly advantageous in the case of such a monolithic matrix light source, in which it is not possible to accurately measure the junction temperature of each light element, and in which it is consequently important to be able to take into account the evolution of the thermal resistance between the hottest pixel and at least one temperature sensor located around the monolithic matrix light source.

[0045] A second aspect of the invention relates to a computer program comprising instructions for implementing the method according to the first aspect of the invention, when these instructions are executed by a processor.

[0046] A third aspect of the invention relates to a control module for a lighting module comprising a matrix light source comprising a plurality of individually controllable light elements, the control module comprising a processor configured to: - determine a photometry defining a luminous intensity value for each luminous element of the matrix light source; - adapt thermal protection of the matrix light source based on at least one piece of information derived from determined photometry, ambient temperature and / or regulatory constraints of a lighting function.

[0047] A fourth aspect of the invention relates to an assembly comprising a control module according to the third aspect of the invention and a lighting module comprising a matrix light source comprising a plurality of light elements individually controllable by a control module of the lighting module.

[0048] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings in which:

[0049] [Fig-1] illustrates a lighting system of a motor vehicle according to modes of realization of the invention;

[0050] [Fig.2] illustrates a lighting module for a motor vehicle according to embodiments of the invention;

[0051] [Fig.3] illustrates an illumination photometry for a matrix light source according to embodiments of the invention;

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058] [Fig.4] is a diagram illustrating the steps of a method of adapting a thermal protection of a matrix light source according to embodiments of the invention; [Fig.5] illustrates a structure of a control module of a matrix light source according to embodiments of the invention. The description focuses on the features that distinguish the lighting system and method from those known in the state of the art. [Fig.l] shows a motor vehicle 100 according to embodiments of the invention. - The vehicle 100 comprises a lighting system comprising several lighting modules 101, one of the lighting modules 101 being shown in [Fig.l]. The lighting system comprises at least one lighting module arranged in a right headlight housing of the vehicle 100 and one lighting module arranged in a left headlight housing of the vehicle 100. The lighting module 101 is capable of performing at least one lighting function, such as: - a low beam function, also called LB for “Low Beam” in English; and / or - a high beam function, also called HB for “High Beam” in English. For example, the lighting module 101 is capable of performing the dipped beam function and the high beam function. Alternatively, a first lighting module is capable of performing the dipped beam function and a second lighting module is capable of performing the high beam function. Furthermore, the lighting module 101 may be capable of performing one or more signaling functions. The lighting module 101 according to the invention comprises a matrix light source, in particular of the monolithic type. The structure of the lighting module 101 and the structure of the matrix source will be described in detail with reference to [Fig.2]. The vehicle 100 further comprises a control module 102, also called a “driver”, capable of determining a lighting photometry, of generating lighting instructions as a function of the determined lighting photometry, and of transmitting the lighting instructions to the lighting module 101, the lighting instructions being able to comprise duty cycle values ​​for PWM control of each pixel of the matrix source. The lighting photometry can thus be considered as an image composed of elements, in which each element corresponds to an electroluminescent element of the matrix source, each element being associated with a light power determining a PWM duty cycle value, or being associated with a PWM duty cycle value.

[0059] The control module 102 can control the lighting module 101, and in particular a control module of the lighting module 101 described below, via a wired communication channel 105, which can be a CAN link for example.

[0060] The control module 102 is capable of determining the photometry at a given frequency, for example at a frequency of several photometries per second, in particular several tens of photometries per second, for example 60 photometries per second.

[0061] The control module 102 can determine the photometry from data from at least one sensor 103 of the vehicle 100, capable of acquiring descriptive data of the external environment of the vehicle. The at least one sensor 103 can for example comprise a camera facing outwards and towards the front of the vehicle 100, in a direction of travel of the vehicle 100, capable of acquiring images representative of the scene facing the vehicle. It is thus made possible to determine the lighting photometry from the scene facing the vehicle, which is advantageous, for example for illuminating a pedestrian, for avoiding dazzling other drivers, for illuminating a traffic sign, etc. Such an adaptive determination of the lighting photometry is well known and is not described further in the present description.

[0062] Alternatively or in a complementary manner, the control module 102 can determine the photometry as a function of input data, such as information or commands from a central control module 104 of the vehicle, also called “body controller” in English. The central control module 104 can in particular transmit a command to activate or deactivate a lighting function, such as the LB or HB function described previously for example, and such commands are taken into account when determining the photometry, so that the photometry performs the required lighting function. The central control module 104 can furthermore transmit information such as the steering wheel angle, information which can be taken into account as input data by the control module 102 when determining the photometry.

[0063] [Fig.2] shows the structure of a lighting module 101 according to rea modes lization of the invention.

[0064] The lighting module 101 comprises a control module 201 of a matrix light source 200 comprising a plurality of individually controllable electroluminescent elements 203, and which can be arranged in a matrix as shown in [Fig.2].

[0065] According to the invention, the matrix light source 200 is of the monolithic type. As described previously, a so-called “monolithic” matrix light source can have a high density of light elements, which makes it particularly interesting for a plurality of applications. A monolithic source involves a plurality of light-emitting semiconductor elements with submillimeter dimensions, epitaxially grown directly on a common substrate, the substrate generally being formed of silicon. In contrast to sources comprising conventional LED matrices, in which each elementary light element is an electronic component produced individually and mounted on a substrate such as a printed circuit board, PCB, a monolithic source is to be considered as a single electronic component, during the production of which several pads of light-emitting semiconductor junctions are generated on a common substrate, in the form of a matrix.This production technique allows for the production of electroluminescent areas, each acting as an elementary light element, very close to each other. The gaps between the light elements can have submillimeter dimensions. An advantage of this production technique is the high level of pixel density that can result on a single substrate.

[0066] Thus, each light element 203 of the monolithic matrix source 200 can be considered as a pixel, and the individual control of each of the pixels makes it possible to carry out the photometry received from the control module 102.

[0067] For this purpose, the control module 201 may be capable of controlling the electrical power delivered to each of the light elements 203, for example by varying the electrical intensity passing through each light element 203, so as to vary the light intensity of each light element 203.

[0068] In order to vary the electrical intensity passing through a light element 203, the control module can control a duty cycle value applied to the electrical intensity delivered by an electrical power source 205, integrated in the lighting module 101 or external to the lighting module 101. The intensity value delivered by the source 205 can thus be subject to pulse width modulation, or PWM, for Pulse Width Modulation in English, well known in the field of lighting.

[0069] Thus, a given photometry can indicate a duty cycle value to be applied to each of the light elements 203 of the monolithic matrix source 200. A light beam performing the photometry is emitted by the monolithic matrix source 200, the beam being projected in front of the vehicle 100 by a projection optic 202 of the lighting module 101.

[0070] The lighting module 101 comprises at least one temperature sensor positioned close to the matrix source 200, and capable of measuring, at a given frequency, a temperature representative of the temperature of the monolithic source 200, in particular representative of the junction temperatures of the light elements 203. As described previously, the measured temperature depends on the position of the temperature sensor, the projected photometry and its evolution dynamics, the position of the hottest pixel, the thermal resistance between the hottest pixel and the temperature sensor, and the ambient temperature. The lighting module 101 may comprise several temperature sensors, in order to improve the accuracy associated with temperature measurements near the matrix source 200.

[0071] In the example of [Fig.2], the lighting module 101 comprises four temperature sensors 204.1 to 204.4 arranged at each corner of the matrix of light elements 200, namely a first temperature sensor 204.1 at the top left of the matrix source 200, a second temperature sensor 204.2 at the top right of the matrix source 200, a third temperature sensor 204.3 at the bottom left of the matrix source 200 and a fourth temperature sensor 204.4 at the bottom right of the matrix source 200. However, no restriction is attached to the number of temperature sensors arranged near the matrix source 200, which can be any integer N greater than or equal to 1.

[0072] Note that the control module 101 may further comprise an ambient temperature sensor, capable of measuring the ambient temperature, not shown in [Fig.2],

[0073] The control module 201 is capable of obtaining the temperature values ​​measured respectively by the temperature sensors 204.1 to 204.4, and the ambient temperature value from the ambient temperature sensor.

[0074] The control module 201 is in particular capable of interrogating the temperature sensors at a given frequency in order to obtain the measured temperature values.

[0075] According to embodiments of the invention, the control module 201 may be of the ASIC type and may be arranged directly on the matrix source 200. In addition, the temperature sensors 204.1 to 204.4 may be arranged on the matrix source 200 itself, in particular on the substrate on which the light elements 203 are epitaxially grown.

[0076] Note that in [Fig.2], for reasons of readability, the matrix source 200 comprises 72 light elements 203 distributed over 9 columns and 8 rows. However, in practice, the matrix source 200 may comprise several hundreds, or even several thousands, or even several tens of thousands of light elements 203.

[0077] [Fig. 3] shows the structure of a photometry 300 determined by the control module 102, according to embodiments of the invention.

[0078] The photometry 300 comprises a set of elements 303 corresponding respectively to the pixels or light elements 203 of the matrix source 200. Thus, the photometry 300 comprises 9 columns and 8 lines of elements 303.

[0079] In [Fig. 3], the more an element 303 is associated with a high duty cycle, therefore with a high light intensity, the more it is grayed out. The white elements 303 can thus be associated with zero duty cycle values, thus corresponding to unlit pixels of the matrix source 200.

[0080] Photometry 300 is a simplified example of photometry that can be determined by the control module 102. In the simplified example of photometry 300, an element 306 is associated with a duty cycle value greater than all the duty cycle values ​​of the other elements 303 of photometry 300. In this case, a light element 206 corresponding to element 306 constitutes the hottest pixel, having the highest junction temperature, in particular if photometry 300 is kept unchanged for a given period. As described previously, the control module 102 can update the photometry commanded to lighting module 101, several times per second, for example sixty times per second.

[0081] The example in [Fig.3] illustrates a simple case of identifying the hottest pixel. In practice, the hottest pixel may however depend on the dynamics of the evolution of the photometry and not on an instantaneous photometry.

[0082] Considering that pixel 206 of [Fig.2] is the hottest pixel, it is understood that the thermal resistance illustrating the temperature difference between the temperatures captured by the temperature sensors 204.1 to 204.4 and the junction temperature of pixel 206, depends on the position of the hottest pixel 206 relative to the temperature sensors 204.1 to 204.4, the overall photometry, the dynamics of the evolution of the photometry and the ambient temperature.

[0083] Thus, for a photometry different from the photometry of [Fig.3], for example with a hottest pixel located in the lower right corner near the fourth sensor 204.4, the thermal resistance between the hottest pixel and the temperature sensors 204.1 to 204.4 will be different from that of the photometry of [Fig.3].

[0084] The invention described below makes it possible to take into account the variability of the thermal resistance in the adaptation of the thermal protection of the matrix source 200.

[0085] [Fig.4] is a diagram illustrating the steps of a method of adapting the thermal protection of a matrix light source, according to embodiments of the invention.

[0086] The method notably comprises steps 401 to 403 implemented by a control module of a matrix light source, such as the control module 102 described with reference to [Fig.l].

[0087] In a first embodiment, a thermal protection mechanism for the matrix source 200 is implemented in the control module 201 of the lighting module 200, the thermal protection mechanism corresponding to steps 404 to 406 described later. In a second embodiment, the thermal protection mechanism thermal protection of the matrix source is implemented by the control module 102 when determining the lighting photometry. However, in these two embodiments, the control module 102 is capable of implementing the adaptation of the thermal protection of the matrix source, which comprises steps 401 to 403 described below.

[0088] The first embodiment is described first in the following. The thermal protection mechanism implemented in the control module 201 is first described, before describing steps 401 to 406 of the method according to the first embodiment.

[0089] The thermal protection mechanism implemented in the control module 201 may be based on at least one thermal protection parameter, which may include: - at least one temperature threshold value; - a refresh rate, or a refresh speed, of the thermal protection, corresponding to a frequency of updating the light power emitted by the matrix source to achieve the reduction in light power. The refresh rate thus indicates a number of intermediate steps to go from an initial emitted light power to a reduced emitted light power within the framework of the thermal protection; - a minimum light power level.

[0090] The thermal protection mechanism may for example be as follows: a temperature value is obtained from the value or values ​​measured by the temperature sensors near the source, and the obtained temperature value is compared to the at least one temperature threshold value (first parameter). Depending on the result of the comparison, a reduction in the light power may or may not be applied, at the given refresh rate (second parameter), when executing the photometry received from the control module 102, by reducing at least some of the duty cycles of the light elements 203 indicated in the received photometry, while ensuring that the light power level after reduction in the light power remains higher than the third parameter. Such a reduction in the light power to protect the matrix source 200 is also called “derating” in English.

[0091] The at least one temperature threshold value may comprise: - a first temperature threshold value, called the low temperature threshold; and - a second temperature threshold value higher than the first temperature threshold value, and called the high temperature threshold.

[0092] The thermal protection mechanism can then be as follows: - if the temperature value obtained from the measured temperature values, is lower than the low temperature threshold, then the duty cycle values ​​indicated by the lighting photometry are applied by the control module, without decreasing any value (without derating); - if the temperature value obtained from the measured temperature values ​​is between the low temperature threshold and the high temperature threshold, the derating protection mechanism is implemented by reducing the light power relative to the photometry transmitted by the control module 102. The reduction in light power can be achieved by reducing the duty cycle for one or more elements 203 of the matrix source 200, the level of reduction being able to be proportional to the difference between the temperature value obtained and the low temperature threshold; - if the temperature value obtained from the measured temperature values ​​is higher than the high temperature threshold, the thermal protection mechanism can interrupt the power supply to the matrix light source 200, in order to avoid damaging one or more light elements, the junction temperature of which can exceed a critical temperature.

[0093] Note that when the lighting module comprises several temperature sensors, for example the four temperature sensors 204.1 to 204.4, the temperature value obtained may be one of the following values: - the highest temperature value among the temperature values ​​measured by temperature sensors 204.1 to 204.4; - the average value of the temperature values ​​measured by the temperature sensors 204.1 to 204.4; - the highest temperature value among a first average value of the temperature values ​​measured by the temperature sensors 204.1 and 204.2 and a second average value of the temperature values ​​measured by the temperature sensors 204.3 and 204.4; - any other temperature value obtained from the temperature values ​​measured by temperature sensors 204.1 to 204.4.

[0094] The second parameter presented previously is a refresh rate, which corresponds to the frequency of updating the light power emitted by the matrix source to achieve the reduction in light power. Such a frequency thus determines the number of intermediate steps in the adaptation of the emitted light power, to go from the initial light power to the light power reduced by the thermal protection.

[0095] The third parameter presented previously is the minimum light power threshold which can define a minimum value for the light power emitted by the matrix light source 203. When applying the reduction of light power, the control module 201 verifies that the reduction in light power achieved by reducing the duty cycle of light elements 203 is not less than the minimum light power threshold, in which case, the reduction in light power is limited so that the light power is not less than the minimum light power threshold. In order to facilitate such a verification, the minimum light power threshold may be a value expressed in percentages, which may be compared to an average duty cycle value applied to the light elements 203 of the matrix source 200 or to a subset of light elements 203 of the matrix source 200. Such a third parameter makes it possible to ensure that the thermal protection is not at the expense of a minimum lighting level, ensuring safety and driving comfort for the driver of the vehicle 100.

[0096] According to the prior art, such thermal protection parameters are defined in a fixed manner in a memory of the control module 201, and are loaded into registers of the control module 201 each time the control module 201 is started.

[0097] The thermal protection mechanism implemented in the control module 201 in the first embodiment has thus been presented, and the remainder of the description presents steps 401 to 406 of the method according to the first embodiment.

[0098] The control module 102 determines, at a step 401, a lighting photometry as a function of at least one input data item, the at least one input data item comprising: - data from at least one sensor 103, such as an image or a series of images representative of the scene facing the vehicle; - a command to activate and / or deactivate a lighting function received from the central control module 104; and / or - a steering angle received from the central control module 104.

[0099] Determining a photometry based on such input data is well known and is not described further.

[0100] In addition or as a variant, the control module 102 can receive an ambient temperature value indicating the ambient temperature outside the vehicle.

[0101] At a step 402, the control module 102 determines at least one adaptation of the thermal protection implemented by the control module 201, from: - at least one piece of information derived from the determined photometry; and / or - regulatory constraints associated with the lighting function to be performed; and / or - the ambient temperature, measured or estimated.

[0102] The at least one piece of information derived from the determined photometry may be one or more of the following pieces of information:

[0103] - a maximum value among the duty cycle values ​​defined by the pho- determined tometry; - an average load corresponding to an average of the cyclic values ​​of the determined photometry; - a position of the hottest pixel estimated from the determined photometry, and optionally from previously determined photometries; - a variation in the average charge between the determined photometry and the previous photometry (resulting from a previous iteration of step 401).

[0104] According to the invention, the adaptation of the thermal protection implemented by the control module 102 comprises the modification of at least one thermal protection parameter. Thus, step 402 according to the first embodiment comprises the modification, by the control module 102, of at least one thermal protection parameter in a register of the control module 201, as a function of the information derived from the photometry, the regulatory constraints of the lighting function and / or the ambient temperature.

[0105] It is thus made possible to dynamically adapt the thermal protection of the matrix source 200 as a function of variables which impact the thermal resistance between the hottest pixel and the temperature sensors, or as a function of regulatory constraints. The disadvantages associated with fixed values ​​of thermal protection parameters are thus overcome.

[0106] Examples of modifications of thermal protection parameters are given below, for illustrative purposes.

[0107] In the case where the determined photometry corresponds to a case of lighting on a motorway, with a narrow beam and high values ​​of duty cycles for a restricted set of pixels, the thermal resistance between the hottest pixel and the temperature sensor(s) may be higher than in a case of driving on the road at moderate speed. In this case, the control module 102 may reduce the first parameter, namely the at least one temperature threshold value, for example the low temperature threshold, beyond which the reduction in light power is triggered by the control module 201.

[0108] On the contrary, in a case of low-speed city traffic, the photometry can define a wide beam with lower values ​​of duty cycles than in the previous case, and the thermal resistance between the hottest pixel and the temperature sensor(s) is lower than in a case of moderate-speed road traffic. In this case, the control module 102 can increase the first parameter, namely the at least one temperature threshold value, for example the low temperature threshold, beyond which the reduction in light power is triggered by the control module 201.

[0109] These two cases make it possible to take into account the evolution of thermal resistance. in setting the first parameter. More generally, the control module 102 can estimate a current value of thermal resistance from the photometry and / or from the ambient temperature, and can determine a modification of the first parameter from the estimated current value of thermal resistance.

[0110] In another case, the control module 102 determines a significant variation in average load, for example greater than a predetermined threshold, between the photometry determined in step 401 and the photometry determined in a previous iteration of step 401. As a reminder, the average load can be determined from an average of the duty cycles of the elements 303 of the determined photometry. If the variation in average load is greater than the predetermined threshold, the control module 102 can increase the second parameter, namely the refresh rate, in the control module 201. Thus, it is made possible to anticipate a rapid variation in temperature due to the significant variation in average load, and to increase the frequency of updating the light power emitted by the matrix source to achieve the reduction in light power.

[0111] In another case, the control module 102 determines a modification of the third parameter as a function of regulatory constraints of the lighting function to be performed. For example, the minimum power level required for the dipped beam function is lower than the minimum power level required for the high beam function. Thus, in the event of deactivation of the high beam function, the control module 102 can decrease the value of the third parameter in the register of the control module 201. Conversely, in the event of activation of the high beam function, the control module 102 can increase the value of the third parameter in the register of the control module 201.

[0112] The cases presented previously are not mutually exclusive but can be combined: the control module 102 can thus modify several thermal protection parameters during the same iteration of step 402.

[0113] At a step 403, the control module 102 transmits the photometry determined at step 401. Steps 401 and 403 can then be repeated: as mentioned previously, the control module 102 can determine several photometries per second, or even several tens per second, and steps 401 to 403 can thus be repeated several times per second. It is thus possible to adapt in real time the thermal protection parameters to changes in photometries and / or ambient temperature and / or regulatory constraints linked to the lighting function to be carried out.

[0114] Thus, the control module 201 can receive: - following step 402, at least one modification of a thermal protection parameter for updating the register corresponding to the thermal protection parameter in the control module 201; - following step 403, the photometry received from the control module 102, for carrying out said photometry by applying the duty cycles indicated by the elements 303 of the photometry, to the corresponding light elements 203 in the matrix source 200, possibly by first applying the thermal protection.

[0115] Thus, in parallel, the control module 201 further implements the thermal protection mechanism of the matrix source 200 in steps 404 to 406 described below.

[0116] In a step 404, the control module 201 receives a measured temperature value for each of the temperature sensors of the lighting module 101. From said at least one measured temperature value, the control module 201 obtains a temperature value for comparison with the first parameter.

[0117] Furthermore, at a step 405, the control module 201 obtains the thermal protection parameter(s), possibly adapted by the control module at step 402, by reading the corresponding registers in the control module 201.

[0118] In a step 406, the control module 201 applies the thermal protection mechanism as a function of the temperature value obtained in step 404 and as a function of the thermal protection parameters, possibly modified following step 402. Step 406 can thus comprise, if the temperature value obtained is greater than the low temperature threshold (first parameter), the reduction of at least one cyclic value of the photometry received following step 403, in order to reduce the light power of the lighting beam, while taking into account the third parameter to ensure the minimum light power level of the lighting beam.

[0119] In the second embodiment, the thermal protection of the matrix source is implemented by the control module 102, when determining the photometry in step 402, and not by the control module 201: steps 404 to 406 are consequently implemented by the control module 102 and not by the control module 201.

[0120] The control module 102 can provide thermal protection for the matrix source 200, based on the same thermal protection parameters as those previously described, but stored and updated in the control module 102.

[0121] In step 401, the control module 102 determines the photometry in a manner identical to step 401 described in the first embodiment.

[0122] Step 402 is a step of adapting the thermal protection of the matrix source 202, as for step 402 previously described in the first embodiment. Thus, in step 402, the control module 102 determines at least one adaptation of the thermal protection implemented by the control module 201, from: - at least one piece of information derived from the determined photometry; and / or - regulatory constraints associated with the lighting function to be performed; and / or - ambient temperature.

[0123] The at least one piece of information derived from the determined photometry may be one or more of the following pieces of information: - a maximum value among the duty cycle values ​​defined by the determined photometry; - the average charge corresponding to the average of the cyclic values ​​of the determined photometry; - the position of the hottest pixel estimated from the determined photometry, and optionally from previously determined photometries; - the variation of the average charge between the determined photometry and the previous photometry (resulting from a previous iteration of step 401).

[0124] According to the second embodiment, the adaptation of the thermal protection implemented by the control module 102 may comprise the modification of at least one thermal protection parameter stored in the control module 102. Thus, step 402 according to the second embodiment comprises the modification, by the control module 102, of at least one thermal protection parameter in a memory of the control module 102, as a function of the information derived from the photometry, the regulatory constraints of the lighting function and / or the ambient temperature, and / or other additional parameters associated with the thermal protection.

[0125] The photometry determined in step 401, possibly adapted as described below, can be transmitted in a step 403 to the control module 201, for execution and control of the power supply of the light elements 203 of the matrix source 200.

[0126] In the second embodiment, the control module 102 implements steps 404 to 406 before transmitting the photometry to step 403.

[0127] In step 404, the control module 102 interrogates the control module 102 in order to obtain: - the temperature value(s) measured by the temperature sensor(s) of the lighting module 101. In this case, step 404 further comprises the control module 102 obtaining a temperature value from the temperature values ​​measured by the temperature sensor(s) of the lighting module 101; or - the temperature value obtained from the temperature values ​​measured by the temperature sensor(s) of the lighting module 101, as previously described.

[0128] In step 405, the control module 102 obtains the protection parameters thermal that it stores in a memory, possibly modified during step 402.

[0129] In step 406, the control module 102 applies the thermal protection mechanism as a function of the temperature value obtained in step 404 and as a function of the thermal protection parameters, possibly modified following step 402. Step 406 can thus comprise, if the temperature value obtained is greater than the low temperature threshold (first parameter), the reduction of at least one cyclic value of the photometry determined in step 401, before transmission to step 403, in order to reduce the light power of the lighting beam, while taking into account the third parameter to ensure the minimum light power level of the lighting beam.

[0130] Thus, in the embodiment, the photometry can be modified upstream, before transmission to the control module 201, in order to apply the thermal protection mechanism of the matrix source 200. The control module 102 can in particular implement a more complex thermal protection mechanism than the control module 201, based for example on more than three parameters, or allowing a finer adaptation, element 303 by element 303, of the photometry to reduce the light power of the lighting beam.

[0131] [Fig.5] illustrates the structure of a control module, such as the control module 102, of a matrix source 200, according to embodiments of the invention.

[0132] The control module 102 comprises a processor 501 configured to communicate unidirectionally or bidirectionally, via one or more buses or via a direct wired connection, with a memory 502 such as a memory of the “Random Access Memory” type, RAM, or a memory of the “Read Only Memory” type, ROM, or any other type of memory (Flash, EEPROM, etc.). Alternatively, the memory 502 comprises several memories of the aforementioned types.

[0133] The memory 502 is capable of storing, permanently or temporarily, at least some of the data used and / or resulting from the implementation of the steps of the method according to the invention illustrated with reference to [Fig.4].

[0134] In particular, the memory 502 may be capable of storing rules for adapting the thermal protection. Such rules may be applied to data (at least one piece of information derived from the photometry during step 402, the ambient temperature, and / or the regulatory constraints associated with the lighting function) to determine the adaptation of the thermal protection, in particular the modification of at least one thermal protection parameter, as previously detailed. Furthermore, in the second embodiment, the memory 502 may store the thermal protection parameters, updated during the iterations of steps 402.

[0135] The processor 501 is capable of executing instructions, stored in the memory 502, for the implementation of steps 401 to 403 in the first embodiment, and steps 401 to 406 in the second embodiment. Alternatively, the processor 501 may be replaced by a microcontroller designed and configured to perform steps 401 to 403 in the first embodiment, and steps 401 to 406 in the second embodiment.

[0136] The control module 102 comprises a first interface 503 capable of communicating with the lighting module 101, in particular with the control module 201, via the wired communication channel 105, to transmit to the control module 201 the photometries at the iterations of the steps 403 described previously.

[0137] The control module 102 comprises a second interface 504 capable of receiving, in the second embodiment, the value obtained from the measured temperature values, or the measured temperatures, from the control module 201. In the second embodiment, the first interface 503 and the second interface 504 may be a single bidirectional interface linked to the wired communication channel 105.

[0138] The control module 102 comprises a third interface 505 capable of communicating with the central control module 104 previously described.

[0139] The control module 102 comprises a fourth interface 506 capable of communicating with the at least one sensor 103 previously described, in particular for receiving images representative of the scene facing the vehicle 100.

[0140] The present invention is not limited to the embodiments described above as examples; it extends to other variants.

Claims

Claims

1. A method for adapting the thermal protection of a light source matrix (200) of a lighting module (101) of a vehicle (100) comprising a plurality of individually controllable light elements (203), the method comprising the following steps: - determination (401) of a photometry (300) defining a luminous intensity value for each light element of the light source matrix; - adaptation (402) of the thermal protection of the light source matrix based on at least one information derived from the determined photometry, an ambient temperature and / or regulatory constraints of an illumination function.

2. A method according to claim 1, wherein said thermal protection comprises a decrease (406) in light power emitted by the matrix light source (200) as a function of a temperature value obtained (404) from at least one temperature value measured by a temperature sensor (204.1-204.4) arranged in the lighting module (101).

3. Method according to claim 2, wherein the thermal protection is determined (406) from at least one thermal protection parameter, and wherein the adaptation (402) of the thermal protection comprises the modification of at least one thermal protection parameter, said modified thermal protection parameter, among said at least one thermal protection parameter.

4. The method of claim 3, wherein said at least one thermal protection parameter comprises one or more of the following parameters: - at least one temperature threshold value, wherein the reduction in light power of the thermal protection is implemented if the obtained temperature value is greater than the temperature threshold value; - a refresh rate of the thermal protection, determining a frequency of updating the light power emitted by the matrix source to achieve the reduction in light power; and - a minimum light power level limiting the reduction in light power of the thermal protection.

5. A method according to one of claims 2 to 4, wherein the temperature value obtained (404) from said at least one measured temperature value is determined from several measured temperature values, and is one of the following values: - the highest temperature value among the measured temperature values; - an average value of the measured temperature values; - the highest temperature value among a first average value of a first set among the measured temperature values ​​and a second average value of a second set among the measured temperature values.

6. Method according to one of the preceding claims, in which the determined photometry (300) defines a duty cycle value for a pulse width modulation control of each light element (203) of the matrix light source (200), and in which said at least one information derived from the determined photometry comprises one or more of the following derived information: - a maximum value among the duty cycle values ​​defined by the determined photometry; - an average charge corresponding to an average of the duty cycle values ​​of the determined photometry; - a variation in average charge between the determined photometry and a previous photometry; - a position of a hottest pixel.

7. Method according to one of the preceding claims, in which the photometry (300) is determined (401) from at least one input data among the following data: - data from at least one sensor (103) of the vehicle, capable of obtaining data representative of the external environment of the vehicle; - a command for activation and / or deactivation of a lighting function received from a central control module (104) of the vehicle (100); and / or - a steering angle received from the central control module.

8. Method according to one of the preceding claims and claim 3, implemented by a control module (102) separate from a control module (201) of the matrix light source (200) integrated into the lighting module (101), the method further comprising the transmission (403) of the determined photometry to the control module, and in which the adaptation (402) of the thermal protection comprises the modification, in the control module, of said at least one thermal protection parameter.

9. Method according to one of claims 2 to 7, implemented by a control module (102) separate from the control module (201) of the matrix light source (200) integrated in the lighting module (101), in which the control module obtains (404) the temperature value obtained from the measured temperature values ​​and in which the thermal protection of the matrix light source comprises the modification of the photometry determined to reduce the light power emitted by the matrix light source, as a function of the temperature value obtained, and further comprising the transmission (403), by the control module, of the modified photometry to the control module of the matrix light source.

10. Method according to one of the preceding claims, in which the light elements (203) of the matrix light source (200) are of submillimeter dimensions and are epitaxially grown directly on a common substrate.

11. Computer program comprising instructions for implementing the method according to one of the preceding claims, when these instructions are executed by a processor (501).

12. Control module (102) of a lighting module (101) of a vehicle (100) comprising a matrix light source (200) comprising a plurality of individually controllable light elements (203), the control module comprising a processor (501) configured to: - determine a photometry defining a light intensity value for each light element of the matrix light source; - adapt a thermal protection of the matrix light source as a function of at least one piece of information derived from the determined photometry, an ambient temperature and / or regulatory constraints of a lighting function.

13. An assembly comprising a control module (102) according to claim 12 and a lighting module (101) comprising a matrix light source (200) comprising a plurality of light elements (203) individually controllable by a control module (201) of the lighting module.

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