Lighting module and headlamp of a vehicle including such a lighting module

Abstract

The invention relates to a light module (220) comprising a matrix (111) of pixelated light sources, a driver (112) receiving a power voltage (Vp) and providing a driving voltage to each pixelated light source of the matrix (111), a monitoring circuit (113) connected to the driver (112) for monitoring the driver (112) and storing status information into at least one register, said register comprising at least one alarm bit indicating that the driving voltage is out of a correct range. The light module (200) further comprises an analog control circuit (221) connected to the register for receiving the at least one alarm bit and for providing an analog signal (Vreg) having a voltage value representative of the at least one alarm bit on an analog output. The invention also relates to a headlamp module (200) comprising a DC-DC converter (140) and a light module (220) according to the invention.

Description

Lighting module and headlamp of a vehicle including such a lighting module

[0001] The invention relates to a lighting module and to a headlamp of a vehicle including such a lighting module. More particularly, the invention relates to a lighting module for an automotive vehicle capable of projecting a pixelated light beam.

[0002] Light emitting diodes (hereinafter LEDs) are commonly used in the headlamps of vehicle because of their low consumption. In addition, they are used in matrix enabling to have a controlled light beam allowing to have dynamic bending lights but also to prevent the dazzling of a front vehicle. Today it is known to have high-definition (HD) matrix of LEDs that are controlled by sending an image of light.

[0003] As an example, a HD lighting module sold by the company OSRAM under the reference KEW GBBMD1U comprises a matrix of 320x80 LEDs and a HD lighting module sold by the company Nichia under reference NMAWA 16KAT comprises a matrix of 256x64 LEDs. These lighting modules further comprise drivers for independently controlling each LED of the matrix, a diagnostic circuit for monitoring the drivers and a communication circuit for exchanging digital data with another circuit.

[0004] Currently, a headlamp including a HD lighting module further comprises a controlling circuit, power supply circuits and sometimes a fan for cooling the headlamp. The controlling circuit is connected to the HD lighting module for sending a lighting image but also for monitoring the HD lighting module for adjusting power supply circuits when needed.

[0005] Each headlamp of the vehicle comprises a controlling circuit which is relatively expensive. The controlling circuit may also cause some breakdown because of the heat released by the lighting module. So, the moving of the controlling circuit into a zonal controller outside the lighting module. In some cases, the zonal controller can also be a Body Control Module (BCM) of the vehicle that enables automotive manufacturers to have a single controlling circuit for several headlamps, which reduce the cost and prevent overheating of the control circuit. However, because the zonal controller is outside the lighting module, the detection of thermal issues on the pixelated LED substrate and their thermal de-rating control takes more time. Additionally, the zonal controller needs to correspond with a voltage regulator to control the pixelated LED substrate. This adds more complexity in the circuit. In some cases, the zonal controller can have a specific protocol that is different form the voltage regulator and hence the zonal controller may not recognize the voltage regulator leading to synchronization issues. Moreover, power supply circuits are analog components having analog control that needs an analog connection with the controlling circuit. Such an analog connection needs a dedicated wire between the zonal controller and the headlamp which is not desirable and increases the cost.

[0006] The invention provides a light module having an analog output for directly controlling a power supply circuit. The digital data related to voltage monitoring modulate an analog signal capable to controlling the power supply circuit. The invention provides also a headlamp module using this light module controlling directly its power supply circuit.

[0007] More particularly, the invention relates to a light comprising:- a matrix of pixelated electroluminescent light sources, wherein a plurality of light elements are mounted on a common substrate, the lighting module being configured to project a pixelated beam,- a driver connected to the matrix, said driver having an input for receiving a power voltage and for providing a driving voltage to each pixelated electroluminescent light source of the matrix,- a monitoring circuit, said monitoring circuit being connected to the driver for providing an image to be displayed by the matrix and for monitoring the driver and storing status information into at least one register, said register comprising at least one alarm bit indicating that the driving voltage is out of a preferred range,- a communication interface connected to the monitoring circuit and to a communication bus, the communication interface allowing to receive an image to display and to read the register from the communication bus,characterized in that the light module further comprises an analog control circuit connected to the register for receiving the at least one alarm bit and for providing an analog signal having a voltage value representative of the at least one alarm bit on an analog output.

[0008] According to a specific embodiment, the at least one alarm bit can comprise a first alarm bit and a second alarm bit, the first alarm bit indicating whether or not the driving voltage is lower than a first voltage threshold, and the second alarm bit indicating whether or not the driving voltage is higher than a second voltage threshold. The first and second threshold can define a functioning range of the driving voltage, and the second threshold can be higher than the first threshold.

[0009] In the particular embodiment, the analog signal can be set to a first voltage value when the first and second alarm bits are both inactive, the analog signal can be set to a second voltage value when the first alarm bit is active, and the analog signal can be set to a third voltage value when the second alarm bit is active.

[0010] For having more precision in the driving control, the at least one bit can comprise several bits corresponding to a positive or negative integer value representative of a difference voltage between the driving voltage and a maximum voltage value or a minimum voltage value. The analog control circuit can comprise a digital to analog converter providing analog signal corresponding to the conversion voltage of the positive or negative integer value in addition to an offset voltage value.

[0011] The invention also relates to a headlamp module comprising a DC-DC converter and a light module according to the invention, wherein the DC-DC converter being connected to a battery voltage to provide the power voltage to the driver ,wherein said DC-DC converter comprises variable input for receiving the analog signal from the analog control circuit , the DC-DC converter being further configured to control the power voltage based on the received analog signal.

[0012] Using an analog control circuit for control of the DC-DC converter ensures faster response times and lower latency when compared to using digital controllers that are controlled by microcontrollers. Analog control systems process signals continuously without sampling delays, whereas digital systems must sample, convert, process, and then output signals, introducing latency. In headlamp applications, faster response times can improve safety and performance.

[0013] The invention will be detailed with reference to the annexed drawings in which:

[0014] shows a headlamp module of a vehicle according to prior art,

[0015] shows a headlamp module of a vehicle according to the invention,

[0016] details an analog control circuit according to the invention.

[0017] For simplifying the specification, a same reference is used in several drawing for designating a same element or a similar element. In addition, the element already described in one figure will not necessarily be described in a subsequent figure.

[0018] Theshows a headlamp module 100 of a vehicle according to prior art. Such a headlamp module 100 can constitute a complete headlamp with optical means or only a part of the headlamp, providing one high-definition light beam amongst several light beam of a complete headlamp of the vehicle. The headlamp module 100 comprises a light module 110, a microcontroller 120, a first power converter 130, and a second power converter 140.

[0019] The light module 110 could be, as an example, a HD lighting module sold by the company OSRAM under the reference KEW GBBMD1U. Such a light module 110 comprises a matrix 111 of pixelated electroluminescent light sources, which can be LED in the case of the OSRAM circuit, a driver 112, a monitoring circuit 113, and a communication interface 114.

[0020] An electroluminescent source is a solid-state light source (acronym for “solid-state lighting”) comprising electroluminescent elements that use electroluminescence to emit light. Electroluminescence is an optical and electrical phenomenon in which a material emits light in response to an electric current flowing through it, or to a strong electric field. This is to be distinguished from light emission due to temperature (incandescence) or the action of chemicals (chemiluminescence). The monolithic electroluminescent light source comprises hundreds or thousands of electroluminescent elements sharing the same layer of electroluminescent material and / or substrate. The electroluminescent elements can be arranged in a matrix arrangement with several columns and several rows, also known as a “monolithic matrix”. The monolithic matrix is therefore a grid of electroluminescent elements or a grid of pixels. Each of the matrix's electroluminescent elements is electrically independent of the others, and emits or not light independently of the other matrix elements. Each element of the matrix is controlled individually. Alternatively, the electroluminescent elements can be grouped together electrically, for example by powering them in parallel or in series, to reduce the number of elements to be controlled. To control the light source, the latter can be coupled with an electronic device that is able to power and control the elements of a monolithic matrix of electroluminescent elements.

[0021] This new family of monolithic electroluminescent light sources offers a large number of pixels, on the order of thousands of pixels, in a single envelope for greater compactness. It also simplifies the optical design of the light module, compared with that of a DMD (digital micromirror device). A DMD requires not only projection optics, but also collimation optics to collimate the light rays coming from a light source, most often a light-emitting diode (LED). In a light module with a monolithic source, only the projection optics are required for direct imaging of this source.

[0022] The matrix 111 can comprise pixelated electroluminescent light sources mounted on a single substrate enabling to display an image of light constituting a pixelated light beam with optical means (not shown) placed in front of said matrix 111. The driver 112 is connected to the matrix 111 and comprises a plurality of drivers for driving individually each pixelated electroluminescent light source of the matrix 111 according to a light image to display. The driver 112 further comprises an input connected to the second power converter 140 for receiving a power voltage Vp used for powering the pixelated electroluminescent light sources of the matrix 111 by providing individually a driving voltage. The monitoring circuit 113 comprises a controlling part storing the image to display for controlling the driver 112 and a monitoring part for monitoring the driver and storing in a status register information related to the functioning state of the light module 110. Some bits of the status register can correspond to specific command and some other bit of the status register corresponds to reporting bits that may indicates a misfunctioning. The communication interface 114 is connected to the monitoring circuit 113 for exchanging information through an input / output port. The communication interface 114 enables to receive the light image for storing it in the controlling part of the monitoring circuit 113 and enables to read and to write the bits of the status register of the monitoring circuit 113.

[0023] The microcontroller 120 is a processing unit comprising memory for storing programs and data. The microcontroller 120 comprises a first input / output bus connected to the communication interface 114 of the light module 110, a second input / output bus connected to a CAN bus, and an analog output.

[0024] The first power converter 130 is a DC-DC voltage converter which receives a voltage Vbat from the battery of the vehicle and provides a supplying voltage Vcc for supplying the logic circuit of the headlamp module 100. As an example, the supplying voltage Vcc is 5 volts, and the supplying voltage is provided to the light module 110 and to the microcontroller 120.

[0025] The second power converter 140 is a DC-DC voltage converter which receives a voltage Vbat from the battery of the vehicle and provides the power voltage Vp to the driver 112. As an example, the power voltage Vp is comprised between 3.5 and 4.5 volts. The second power converter 140 further comprises a regulation input connected to the analog output of the microcontroller for receiving a regulation voltage Vreg for increasing or decreasing the power voltage Vp. As an example, the second power converter 140 can be a buck converter having a feedback loop of a well-known type.

[0026] The microcontroller 120 is in charge of the whole management of the headlamp module 100. The microcontroller 120 receives commands from the CAN bus and transform the commands into other commands for the light module 110. As an example, the received can be: switch-off, switch-on, direction of the light on N degrees right or left, display an information on the road, or other commands for highlighting or preventing to highlight specific zone in the front lighting area. The microcontroller 120 transforms the commands into an image of light that is transmitted to the light module 110. Specific commands can be written by the microcontroller 120 into the status register of the light module 110. Once a light image has been transferred and specific commands written in the status register, the microcontroller 120 periodically read the status register and in particular alarm bits of the register that can report a misfunctioning.

[0027] In particular, the status register can comprise two bits dedicated to the management of the power voltage Vp. Typically, the load of the second power converter 140 is a variable load which depends on the number of pixelated electroluminescent light sources that are driven and of the wear of the pixelated electroluminescent light sources. In addition, the monitoring of the voltage can be made on the driving voltage for each pixelated electroluminescent light sources of the matrix 111 to be sure to have a sufficient power of light and for preventing excessive wear of the pixelated electroluminescent light sources. So, one of the bits can indicate when the driving voltage or the power voltage Vp is lower than a first voltage threshold and another bit can indicate when the driving voltage or the power voltage Vp is higher than a second voltage threshold. The microcontroller 120 reading these two bits can adjust the regulation voltage Vreg for increasing or decreasing the power voltage Vp of the second power converter 140.

[0028] Considering that a complete headlamp of a vehicle can comprises several headlamp modules, and considering that each headlamp module comprises a microcontroller that do not work at its optimum capability except when a light image has to be computed, economy can be made by removing the microcontroller from the headlamp module using a single microcontroller for several headlamp module. Removing the microcontroller from the headlamp module requires to have an analog connection between the microcontroller and each headlamp module for regulating the power voltage Vp which needs additional wires. The addition of additional wires causes an increase of cost of wire which reduce the economy on the reduction of the number of microcontrollers. So, the invention proposes to modify the light module in such a way the light module can directly control the power voltage Vp.

[0029] Theshows a headlamp module 200 of a vehicle according to the invention wherein the microcontroller 120 is moved in a zonal controller 210 for controlling several headlamp modules 200.

[0030] The zonal controller 210 is not fully detailed because it is not the subject of the invention. Nevertheless, the zonal controller comprises the microcontroller 120 which communicate with the headlamp modules 200 through a communication bus, as an example a CAN bus, for only sending light images and specific commands to several headlamp modules 200. In some embodiments, the zonal controller 210 can also be a Body Control Module (BCM) of the automotive vehicle.

[0031] The headlamp module 200 comprises a light module 220, a first power converter 130, and a second power converter 140. The first and second power converters 130 and 140 are identical to prior art. The light module 220 comprises a matrix 111, a driver 112, a monitoring circuit 113, and a communication interface 114 which can be identical to those of the light module 110 of prior art.

[0032] According to the invention, the light module 220 further comprises an analog control circuit 221 connected to the register of the monitoring circuit 113 for providing to the second power converter 140 an analog signal having a voltage value Vreg representative of two bits dedicated to the management of the power voltage Vp. The second power converter 140 is a DC-DC converter being connected to a battery voltage to provide the power voltage (Vp) to the driver (112). The second power converter 140 comprises variable input for receiving the analog signal (Vreg) from the analog control circuit (221). The DC-DC converter (140) being further configured to control the power voltage (Vp) based on the received analog signal (Vreg).

[0033] Thedetails an example of the analog control circuit 221 according to the invention. The analog control circuit 221 comprises first, second, and third shaping circuit 310, 320 and 330, an analog subtracting circuit 340, and an analog adding circuit 350.

[0034] The first shaping circuit 310 provides a first voltage value V0 corresponding to a neutral value for controlling the second power converter 140. The neutral value corresponds to a voltage value for which the second power converter 140 do not change the power voltage Vp. The first shaping circuit 310 can comprises a voltage dividing bridge 311 connected between the supplying voltage Vcc and providing the first voltage value V0 to a follower amplifier 312 which provides said first voltage value V0 to the analog subtracting circuit 340. As an example, the voltage dividing bridge 311 can be a resistive bridge having two identical resistors R1 for providing the voltage value V0 equals to Vcc / 2.

[0035] The second shaping circuit 320 provides a second voltage V1 relative to a first bit value of the one of the bits indicating when the power voltage Vp is lower than a first voltage threshold. The second shaping circuit 320 can comprises a voltage dividing bridge 321 connected to the status register of the monitoring circuit 113 and providing the second voltage V1 to a follower amplifier 322 which provides said second voltage value V1 to the analog subtracting circuit 340. As an example, the voltage dividing bridge 321 can be a resistive bridge having two resistors R2 and R3 serially connected, and having an input receiving the voltage VB1 corresponding to Vcc or zero volt depending on the first bit value and providing the second voltage V1 equals to R3 / (R2+R3)*VB1.

[0036] The third shaping circuit 330 provides a third voltage V2 relative to a second bit value of the another of the bits indicating when the power voltage Vp is higher than a second voltage threshold. The third shaping circuit 330 can comprises a voltage dividing bridge 331 connected to the status register of the monitoring circuit 113 and providing the third voltage value V2 to an inverted follower amplifier 332 which provides the inverted second voltage -V2 to the analog adding circuit 350. As an example, the voltage dividing bridge 331 can be a resistive bridge having two resistors R2 and R3 serially connected, and having an input receiving the voltage VB2 corresponding to Vcc or zero volt depending on the second bit value and providing the third voltage V2 equals to (R3 / R2+R3)*VB2.

[0037] The analog subtracting circuit 340 can comprises an operational amplifier 341 and four identical resistors R mounted in a subtracting circuit having an inverted input receiving the first voltage V0 a non-inverted input receiving the second voltage V1 and an output providing a voltage equals to V1-V0.

[0038] The analog adding circuit 350 can comprises an operational amplifier 351 and three identical resistors R mounted in an inverted adding circuit having a first input connected to the output of the subtracting circuit 340 and a second input receiving the inverted third voltage -V2 and an output providing a voltage equals to V0-V1+V2 corresponding to the voltage value Vreg of the analog signal.

[0039] When the first and second bit are inactive, the second and third voltage V1 and V2 are close to zero volt, and the voltage value Vreg is equal to V0=Vcc / 2. When the first bit is active, VB1 is close to Vcc, the second voltage is equal to k*Vcc, with k=R3 / (R2+R3), and the voltage value Vreg is equal to V0-V1= Vcc*(1-k). When the second bit is active, VB2 is close to Vcc, the third voltage is equal to k*Vcc, with k=R3 / (R2+R3), and the voltage value Vreg is equal to V0+V2= Vcc*(1+k).

[0040] As it can be understood by a person skilled in the art, the invention is not limited to the described example. In particular, the use of two bits for indicating that the driving voltage is too low or too high can cause to have an analog signal having a neutral voltage value between two voltage values, one indicating to the second power converter 140 to increase the power voltage Vp value, while the other indicating to decrease the power voltage Vp value. The fact that the increasing or the decreasing is associated to a higher or lower voltage value is arbitrary set and can be inverted.

[0041] In case we have a second power converter having a drift that can be in a single direction, a single alarm bit is necessary for monitoring the power voltage value.

[0042] In another variant, the monitoring can be made by measuring a gap between the power voltage value and the high and low threshold value of a correct range of power voltage value. The two alarm bits can be replaced by one signed or two unsigned digital values coded on a plurality of bits. The digital value can correspond to a positive or negative integer value representative of a difference voltage between the power voltage and a maximum voltage value or a minimum voltage value. In that case, the shaping circuits can be replaced by digital to analog converters. The analog signal can then correspond to the voltage conversion of the digital value added to and offset corresponding to a neutral value. With such analog signal comprising more than three values, the second power converter 140 can react quickly depending on the voltage values. The DC-DC converter 140 having analog control circuit 221 ensures faster response times and lower latency when compared to using digital controllers.

[0043] Many other modifications can be made by a person skilled in the art without departing from the scope of the annexed set of claims.

Claims

A light module (220) comprising:- a matrix (111) of pixelated electroluminescent light sources, wherein a plurality of light elements are mounted on a common substrate, the lighting module being configured to project a pixelated beam,- a driver (112) connected to the matrix(111), said driver having an input for receiving a power voltage (Vp) and for providing a driving voltage to each pixelated electroluminescent light source of the matrix (111),- a monitoring circuit (113), said monitoring circuit being connected to the driver (112) for providing an image to be displayed by the matrix (111) and for monitoring the driver (112) and storing status information into at least one register, said register comprising at least one alarm bit indicating that the driving voltage is out of a preferred range,- a communication interface (114) connected to the monitoring circuit (113) and to a communication bus, the communication interface (114) allowing to receive an image to display and to read the register from the communication bus,characterized in that the light module (200) further comprises an analog control circuit (221) connected to the register for receiving the at least one alarm bit and for providing an analog signal (Vreg) having a voltage value representative of the at least one alarm bit on an analog output.The light module (220) of claim 1, wherein the at least one alarm bit comprises a first alarm bit and a second alarm bit, the first alarm bit indicating whether or not the driving voltage is lower than a first voltage threshold, and the second alarm bit indicating whether or not the driving voltage is higher than a second voltage threshold.The light module (220) of claim 2, wherein the second threshold is higher than the first threshold.The light module (220) of claim 2 or 3, wherein the analog signal is set to a first voltage value (V0) when the first and second alarm bits are both inactive, wherein the analog signal is set to a second voltage value (V0-k*Vcc) when the first alarm bit is active, and wherein the analog signal is set to a third voltage value (V0+k*Vcc) when the second alarm bit is active.The light module (220) of claim 4 wherein the first voltage value is between the second and third voltage values.The light module (220) of claim 1, wherein the at least one bit comprises several bits corresponding to a positive or negative integer value representative of a difference voltage between the driving voltage and a maximum voltage value or a minimum voltage value, and wherein the analog control circuit comprises a digital to analog converter providing analog signal corresponding to the conversion voltage of the positive or negative integer value in addition to an offset voltage value.A headlamp module (200) comprising a DC-DC converter (140) and a light module (220) according to one of the claims 1 to 6, the DC-DC converter (140) being connected to a battery voltage to provide the power voltage (Vp) to the driver (112),wherein said DC-DC converter comprises variable input for receiving the analog signal (Vreg) from the analog control circuit (221), the DC-DC converter (140) being further configured to control the power voltage (Vp) based on the received analog signal (Vreg).

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