WO2018122067A1 - Information management in a light module for a motor vehicle - Google Patents

Abstract

The aim of the invention is to recover the BIN information or other information identifying properties of light sources comprising a semiconductor element in a light module for a motor vehicle by means of a unique electronic circuit in which the light sources and devices that provide the information relating thereto are implemented. The invention allows the reduction of the wiring between a power supply device and a printed circuit board housing the electronic circuit according to the invention, since the information required for the configuration of the power supply device is actively recovered on the actual power supply line of the light sources.

Description

 INFORMATION MANAGEMENT IN A VEHICLE LUMINOUS UNIT

 AUTOMOBILE

The invention relates to the field of lighting projectors, particularly for a motor vehicle. The invention relates in particular to a light module for such a projector, the module being equipped with light sources with semiconductor element, the provision of parameters, for example BIN information or their temperature, is necessary for the configuration. of the projector. A light-emitting diode, LED, is an electronic component capable of emitting light when traversed by an electric current. The luminous intensity emitted by an LED is generally dependent on the intensity of the electric current flowing through it. Among others, an LED is characterized by a threshold value of current intensity. This maximum forward current is generally decreasing at increasing temperature. Similarly, when an LED emits light, there is observed at its terminals a voltage drop equal to its forward voltage ("forward voltage"). In the automotive field, LED technology is increasingly being used for various light signaling solutions. The LEDs are used to ensure light functions such as daytime running lights, signal lights, etc. LED components from the same production process can nevertheless have characteristics (transmission capacity, direct voltage,. ..) different. In order to group together components with similar characteristics, the LEDs produced are sorted into groups, also called BIN, each BIN grouping together LEDs with similar characteristics.

It is known in the art to use a control circuit for controlling the power supply of a set or group of LEDs. The circuit defines the voltage or current applied to a load-mounted branch including the group of LEDs connected in series. In the field of lighting devices for motor vehicles, it is particularly important to be able to ensure a constant brightness in order to guarantee the safety of vehicle users and road traffic actors. In order to provide a constant power supply, known control circuits use

FIRE I LLE OF REM PLACEM ENT (RULE 26) different types of converters, DC / DC, linear, resistive, etc., to convert the DC voltage supplied for example by a car battery into a DC charging voltage, depending on the number of LEDs powered. The electric current to be supplied depends, among other things, on the BIN of the LEDs to be powered. This is why, according to known assembly methods, it is necessary to obtain the BIN information corresponding to the LEDs used, in order to correctly program or adjust the control circuit used to supply the LEDs with electric current. Similarly, the direct current of an LED depends on its semiconducting junction temperature. In known manner, the BIN information is coded using a resistance of a predetermined value, arranged on the printed circuit that supports the LEDs in question, in isolation from the load branch which groups the light sources. An indication of the temperature of the LEDs can in known manner be obtained by placing a thermistor element on a printed circuit in physical proximity of the LEDs, the voltage drop across which is measurable. The power control circuit of these LEDs is connected by connection wires dedicated to the printed circuit supporting the LEDs to obtain the value of the resistance in question, and to deduce the BIN information and the information on the temperature. With the increasing number of light functions implemented by LEDs, the number of connection cables connecting the power supply control circuit (s) to the printed circuits supporting the LEDs in question is therefore rapidly increasing in order to relay the BIN information. , temperature and others as required. This generates on the one hand significant costs in the production of projectors for motor vehicles, and on the other important design constraints, since the limited space in which all the modules of a light device must be housed is seen restricted by this wiring.

The invention aims to overcome at least one of the problems posed by the prior art. More specifically, the invention aims to provide a light module comprising LED light sources, which reduces the required wiring between the module and its power supply control circuit.

The subject of the invention is a light module for a motor vehicle, comprising a device for controlling the power supply of light sources, and an electronic circuit connected by at least two terminals to the device. piloting. The circuit comprises a first branch comprising at least one of the light sources. The module is remarkable in that the electronic circuit comprises a second branch connected in parallel with the first branch, the second branch comprising at least one state device whose electrical characteristics are representative of at least one property of the source or sources. bright of the first branch. In addition, the electronic circuit is configured to supply electrical power to either the first or the second branch, depending on the voltage applied across the circuit. The power steering device comprises:

a control device configured to control a converter circuit so as to selectively provide different levels of electrical voltage across said electronic circuit, and

 a reading device configured to read a voltage value representative of the or at least one of the properties of the light sources across said electronic circuit.

Preferably, the electronic circuit may comprise at least two state devices whose electrical characteristics are representative of two distinct properties of the light source (s), the at least two state devices being connected in parallel, and the electronic circuit being able to be configured to supply electrical power to only one of the state devices for a given electrical voltage applied across the circuit.

The light sources may preferably be light-emitting diodes, LEDs, which are traversed by an electric current if and only if a voltage greater than a threshold value Vthreshold is applied to their terminals. The light sources may include electroluminescent semiconductor elements. These may be laser diodes. Preferably, the electronic circuit can be configured so that one of the state devices of the second branch is exclusively supplied with electric current only after a passage of the electrical voltage applied across its terminals. value equivalent to the mass at a non-zero value less than the threshold value Vthreshold. The electronic circuit may preferably comprise a capacitance which, when charged, makes it possible to supply electrical power to one of the state devices of the second branch, even when the electrical voltage supplied by the control device of the supply is substantially zero.

One of the state devices may preferably comprise a resistor Rbin whose ohmic value is representative of the BIN value of the light sources. Preferably, one of the state devices may comprise an Rntc thermistor, whose resistance value is variable and representative of the temperature of the light source or sources.

Said electronic circuit may preferentially be arranged on a remote printed circuit with respect to the power control device.

The controller may preferably provide a pulse width modulation signal, PWM, having a duty cycle of less than 100%, said signal being applied to the converter circuit, in order to apply different voltage levels across the electronic circuit. .

Preferably, the control device may comprise a microcontroller element and / or a sequencer. The invention also relates to a method for controlling the power supply of light sources of a motor vehicle by means of a light module. The method is remarkable in that the light module is in accordance with the invention and in that the method comprises the following steps:

a) applying a voltage of a first intensity across the electronic circuit using the converter circuit, and reading, with the aid of the reading device, a first property of the light source or sources of the first branch of the electric circuit ;

b) apply a voltage of a second intensity across the electronic circuit to turn on the light sources. Preferably, the method may comprise the following additional step:

c) applying a voltage of a third intensity across the electronic circuit using the converter circuit, and reading, with the aid of the reading device, a second property of the light source or sources of the first branch of the electric circuit.

Steps b) and c) can preferably be repeated one after the other so, preferably periodically.

Preferably, the first and third intensity voltage may be equal.

Preferably, the first and third intensity voltage may be less than a predetermined voltage Vthreshold, and the second intensity voltage may be greater than or equal to Vthreshold.

The light sources may preferably be light-emitting diodes and the first leg may have a forward voltage equal to the threshold, beyond which all light sources emit light.

Preferably, the read parameters can be stored in a memory element and / or used to configure the power control device.

Step b) of the method may preferably correspond to the active phase of the cycle of a pulse width modulation signal, PWM, generated by the control device, said signal being applied to the converter circuit. Preferably, steps a) and c) of the method can correspond to inactive phases of the PWM signal cycle.

By using the measures proposed by the present invention, it becomes possible to reduce the wiring between a device for controlling the power supply of light sources, and a printed circuit housing said light sources, with respect to techniques known in the art. In a known manner, a first wiring is necessary to guarantee the supply of the light sources, and a second dedicated wiring is necessary to recover the BIN information from the light sources, which are, for example, light emitting diodes, LEDs. Additional wirings become necessary in known solutions, if parameters such as the junction temperature of the LEDs must be supported at the control device. Indeed this information is necessary to control the supply of the LEDs adequately. According to the invention, these second or third (or more) dedicated cabling become superfluous and can be eliminated, since the BIN, temperature or other information can be retrieved by the device for controlling the power supply according to the voltage electrical applied to the terminals of the electronic circuit, by means of the single wiring for supplying the LEDs included in this circuit. The reduction of wiring is particularly important in the design of motor vehicle lights, where a control device can be brought to power several light functions of the vehicle, involving as much information BIN, temperature and other to recover. Reduced wiring reduces the cost of production and also reduces design concerns related to the electromagnetic compatibility of a light module.

Other features and advantages of the present invention will be better understood from the exemplary description and the drawings, among which:

 FIG. 1 represents a schematic illustration of a light module according to a preferred embodiment of the invention;

 FIG. 2 represents a device for reading a light module according to a preferred embodiment of the invention;

 FIG. 3 represents the time evolution of several signals involved in the operation of a light module according to a preferred embodiment of the invention;

 FIG. 4 represents a schematic illustration of an electronic circuit of a light model according to a preferred embodiment of the invention;

FIG. 5 represents a schematic illustration of an electronic circuit of a light model according to a preferred embodiment of the invention; FIG. 6 represents a schematic illustration of an electronic circuit of a light model according to a preferred embodiment of the invention;

FIG. 7 represents a schematic illustration of an electronic circuit of a light model according to a preferred embodiment of the invention.

Unless specifically indicated otherwise, technical characteristics described in detail for a given embodiment may be combined with the technical characteristics described in the context of other embodiments described by way of example and not limitation. Similar reference numerals will be used to describe similar concepts through different embodiments of the invention. For example, references 120 and 220 denote an electronic circuit of a light module according to the invention, in two embodiments described. FIG. 1 gives an illustration of a preferred embodiment of a light module 100 according to the invention. The module 100 comprises a device for controlling the power supply 1 10 of light sources 132, for example of LED type electroluminescent diodes, grouped in series in a first branch 130 of an electronic circuit 120 mounted in charge of the control device by means of the terminals 122 and 124. The electronic circuit 120 is advantageously physically remote relative to the control device 1 10. The two components can be implemented on two printed circuits PCB ("printed circuit board") distinct. The control device 1 10 involves at least one converter circuit 1 14 whose operation will not be described in detail in the context of the present invention. Indeed, this operation and known in the art. The converter circuit 1 14 may be of the buck-voltage, boost-type or, for example, of the SEPIC type (Single Ended Primary Inductor Converter) type, for converting an input DC voltage V | _N supplied by an internal source of a motor vehicle at a different output voltage. The converter circuit 1 14 comprises, according to an advantageous embodiment, an "enable" terminal, EN, which serves to switch the circuit on or off. When it comes to a switching converter circuit, the terminal EN advantageously controls the open state of the switching switch. The control device 1 10 comprises a control device 1 12, made for example by a microcontroller element, which controls the converter circuit 1 14 by means of a control signal which is applied to the terminal EN of the latter. According to a preferred embodiment, the luminous intensity of the powered light sources can be controlled by applying a pulse width modulation (PWM) signal having a given duty cycle and peak current to the converter. chopping. The frequency of the pulse width modulation signal has an impact on the duty cycle. By adapting the frequency of the pulse width modulation signal, a predetermined average current intensity can thus be obtained at the converter. This implies, at the level of the light sources supplied, that a luminous flux of an intensity corresponding to the average intensity of the current flowing through them is emitted. The greater the average intensity of the current flowing through the light sources, the greater the intensity of the luminous flux emitted by the light sources.

A cycle of the PWM signal, which is preferably generated by the control device 1 12, thus comprises an active phase, during which the converter circuit 1 14 is on, followed by an inactive phase, during which the converter circuit 1 14 is not running. The invention uses the inactive phases of the signal to recover data relating to properties of the light sources 132. This is for example BIN information of the LEDs 132, their junction temperature, or other analog or digital information. .

For this purpose, the electronic circuit 120 comprises a second branch 140 connected in parallel with the first branch 130, which comprises the light sources. The second branch 140 comprises at least one state device 142 which induces a voltage drop across its terminals when an electric current flows through it. If the branch 140 comprises several such devices, the configuration of the electronic circuit 120 is such that one of the devices is supplied with electric power exclusively in dependence on the value of electrical voltage applied to the branch 140. The configuration of the electronic circuit is such that during the phases inactive of the converter circuit 1 14, a voltage drop indicative of at least one property of the light sources 132 becomes apparent at the terminals 122, 124 of the electronic circuit 120. In order to recover the information relating to this property, the control device comprises a reading device 1 1 6. When the converter circuit 1 14 is in idle phase, the reading device 1 1 6 is controlled by the control device 1 12 to read the information indicated by "data" in Figure 1. This information can then be used to configure the converter circuit. An exemplary embodiment of the reading device 1 16 is given by the diagram of FIG. 2.

A preferred and non-limiting embodiment of the invention will be described with reference to FIGS. 3 to 7. FIG. 3 shows the evolution of various signals that occur in the light module according to the invention, while FIGS. 7 show a concrete structural embodiment of the electronic circuit 220, which makes it possible to obtain the operation which has just been described, by means of the signals of FIG. 3. The elements of the control device 1 10 remain unchanged with respect to FIG. 1, and reference will be made to the components of Figure 1.

FIG. 3A shows the evolution of the supply of the light module 100. This is the signal V | _N applied to the input terminals of the power control device 1 10. In a first phase, the power is turned on from a source external to the light module. The reading device 1 1 6 is then activated by applying a non-zero control signal RD, as shown in FIG. 3B. At the same time, the converter circuit 1 14 is in stop mode, which is indicated by the signal EN equal to zero in FIG. 3C. During this phase, the "BIN" information is retrieved by the reading device, see FIG. 3D.

Following this initial phase, the control device 1 12 puts the converter circuit 1 14 in operation (EN on 1) to provide a charging voltage greater than the direct voltage V light source sources to the electronic circuit. It is an active phase of the converter circuit, during which no data is read by the reading device (RD on 0), and in which the LEDs emit light ("LEDs ON"). In order to complete the cycle of the PWM signal generated by the control device 1 12, the active phase is followed by an inactive phase of the converter circuit (EN on 0, FIG. 3C). During the inactive phase, the voltage applied to the terminals of the electronic circuit is lower than the direct voltage V threshold LEDs, so they do not emit light. The reading device 1 16 is again controlled to read a "data" information at the terminals of the electronic circuit (RD on 1), corresponding exemplary voltage drop of a thermistor. The command signal EN is then repeated periodically. FIG. 4 gives the electronic diagram of an embodiment of an electronic circuit 220 which makes it possible to obtain the operation described when it cooperates with the control device 1 10 according to the invention. The electronic circuit comprises only two terminals 222, 224 for the load mounting of the control device 1 10 of the light module. A first branch 230 of the circuit comprises a series connection of a plurality of light emitting light sources 232 having electroluminescent semiconductor elements, such as light-emitting diodes, LEDs.

A second branch 240 includes a first state device 242 whose electrical characteristics are representative of a property of the light sources. In this case, it is a resistor Rbin whose resistance value is representative of the BIN value of the LEDs 232.

The branch 240 also comprises a second state device 244 whose electrical characteristics are representative of a property of the light sources. It is a resistance to negative temperature coefficient, Rntc, also called "thermistor". The ohmic value of the thermistor is dependent on the temperature of the component. When the Rntc thermistor is installed close to the LEDs 232, its temperature is indicative of the junction temperature of the LEDs. This can therefore be obtained by measuring the voltage drop across the thermistor Rntc. The electronic circuit also involves Zener diodes, transistors and a capacitor, the utility of which will be described below.

FIG. 5 shows the diagram equivalent to the electronic circuit 220 of FIG. 4, during the initial phase indicated by "BIN" in FIG. 3D. Like the circuit converter 1 14 is not active, a very low voltage is applied to terminals 222, 224 of the electronic circuit. The LEDs are not conductive and the electric current can only pass through the device Rbin 242. As the electronic circuit was not previously supplied, the capacity does not carry electrical charges. As the reading device is activated during this phase, the voltage drop across Rbin is read by the control device 1 10, without using a dedicated connection harness for this purpose and with the single connection by the terminals 220 , 224 of the electronic circuit. FIG. 6 shows the diagram equivalent to the electronic circuit 220 of FIG. 4, during the "LEDs ON" phase indicated in FIG. 3D. The converter circuit 1 14 is not active, a voltage Vf at least equal to the threshold voltage Vthreshold is applied to the terminals 222, 224 of the electronic circuit. The LEDs are conductive and the electric current passes only through the first branch 230. The devices 242 and 244 are not powered, but an electric charge accumulates at the level of the capacity of the electronic circuit 220.

FIG. 7 shows the diagram equivalent to the electronic circuit 220 of FIG. 4, during the phase indicated by "NTC" in FIG. 3D. As the converter circuit 1 14 is not active, the LEDs are not conductive. However, the capacitor C charged during the previous active phase allows the remaining electric current to pass through the Rntc thermistor 244. Since the reading device is activated during this phase, the voltage drop across Rntc is read by the control device 1 10, without using a dedicated connection harness for this purpose and with the single connection through the terminals 222

0, 224 of the electronic circuit.

It will be appreciated that the principle of storing information relating to the components of the electronic circuit 120, 220 in a resistor integrated in the electronic circuit can be extended to other components than the light sources, or to information other than the BIN information. or temperature, using the principles of the invention which have just been described. Similarly, the storage of the information can be done in an element other than a resistor or a thermistor, the data can be an analog or digital data.

Claims

claims 1. Light module (100) for a motor vehicle, comprising a device for controlling the power supply (1 10) of light sources (132, 232), and an electronic circuit (120, 220) connected by at least two terminals (122). , 124; 222, 224) to the driving device, the circuit (120, 220) comprising a first branch (130, 230) comprising at least one of the light sources (132, 232),  characterized in that  the electronic circuit (120, 220) comprises a second branch (140, 240) connected in parallel with the first branch, the second branch comprising at least one state device (142, 242, 244) whose electrical characteristics are representative of at least least one property of the light sources (132, 232), and in that  the electronic circuit (120, 220) is configured to supply electrical power to either the first (130, 230) or the second (140, 240) branch, depending on the voltage applied to the terminals (122, 124; 224) of the circuit,  and in that the feed control device (1 10) further comprises:  a control device (1 12) configured to control a converter circuit (1 14) so as to selectively provide different voltage levels at the terminals (122, 124, 222, 224) of said electronic circuit, and  a reading device (1 1 6) configured to read a voltage value representative of the or at least one of the properties of the at least one light source (132, 232) at the terminals (122, 124; 222, 224) of said electronic circuit (120, 220). 2. Module according to the first claim, characterized in that the electronic circuit (220) comprises at least two state devices (242, 244) whose electrical characteristics are representative of two distinct properties of the light sources (232), the minus two state devices being connected in parallel, and in that the electronic circuit is configured for supplying electric current only one of the state devices (242, 244) for a given electrical voltage applied across the circuit (222, 224). Module according to one of claims 1 or 2, characterized in that the light sources (132, 232) are electroluminescent semiconductor elements, which are traversed by an electric current if and only if a voltage greater than a threshold value V threshold is applied to their terminals. Module according to claims 2 and 3, characterized in that the electronic circuit (220) is configured in such a way that one of the state devices (242) of the second branch (240) is supplied with electric current in such a way that exclusive that after a passage of the voltage applied across its terminals from a value equivalent to the mass to a non-zero value less than the threshold value Vseuil. Module according to one of Claims 1 to 4, characterized in that the electronic circuit (220) comprises a capacitor C which, when it is charged, makes it possible to supply one of the state devices (244) of the second branch (240), even when the voltage supplied by the power control device is substantially zero. Module according to one of Claims 1 to 5, characterized in that one of the state devices (142; 242, 244) comprises a resistance Rbin whose resistance value is representative of the BIN value of the light source or sources (132, 232 ) of the first branch. Module according to one of Claims 1 to 6, characterized in that one of the state devices (142; 242, 244) comprises an Rntc thermistor whose resistance value is variable and representative of the temperature of the light source or sources (132, 232) of the first branch. 8. Module according to one of claims 1 to 7, characterized in that the electronic circuit (120, 220) is arranged on a remote printed circuit relative to the power control device (1 10). Module according to one of Claims 1 to 8, characterized in that the control device (1 12) supplies a pulse width modulation signal PWM with a duty cycle of less than 100%, said signal being applied to the converter circuit (1 14), in order to apply different voltage levels to the terminals (122, 124, 222, 244) of the electronic circuit. Module according to one of claims 1 to 9, characterized in that the control device (1 12) comprises a microcontroller and / or a sequencer. Method for controlling the power supply of light sources (132, 232) of a motor vehicle by means of a light module (100), characterized in that the light module (100) is according to one of Claims 1 to 10, and in that the method comprises the following steps:  a) applying an electric voltage of a first intensity to the terminals (122, 124, 222, 224) of the electronic circuit (120, 220) by means of the converter circuit (1 14), and reading, using the reading device (1 1 6), a first property of the at least one light source (132, 232) of the first leg (130, 230) of the electronic circuit (120, 220); b) applying a voltage of a second magnitude to the terminals (122, 124, 222, 224) of the electronic circuit (120, 220) to turn on the one or more light sources (132, 232). Process according to claim 1 1, characterized in that it comprises the following additional step: c) applying a voltage of a third intensity across the electronic circuit using the converter circuit (1 14), and reading, with the aid of the reading device (1 1 6), a second property of the or light sources (132, 232) of the first leg (130, 230) of the electronic circuit (120, 220). 13. The method of claim 12, characterized in that steps b) and c) are repeated one after another repeatedly. 14. Method according to one of claims 12 and 13, characterized in that the voltage of first and third intensity are equal. 15. Method according to one of claims 12 and 13, characterized in that the first and third intensity voltage are lower than a predetermined voltage Vseuil, and in that the second intensity voltage is greater than or equal to Vseuil. Method according to one of claims 1 1 to 15, characterized in that the light sources (132, 232) are light emitting diodes and the first leg (130, 230) has a direct voltage equal to Vseuil, beyond the application from which all the light sources emit light. Method according to one of claims 1 1 to 16, characterized in that the read parameters are stored in a memory element and / or used to configure the power control device. 18. Method according to one of claims 1 1 to 17, characterized in that step b) corresponds to the active phase of the cycle of a pulse width modulation signal, PWM, generated by the control device (1). 12), said signal being applied to the converter circuit (1 14). 19. The method of claim 18, characterized in that the steps a) and c) correspond to inactive phases of the PWM signal cycle.