A lighting circuit for an automotive luminous device and an automotive luminous device

Abstract

The invention provides an automotive luminous device (10) comprising a first light group (1) and a second light group (2). The device (10) further comprises a light driver (4) and an optical element (9) arranged to receive light emitted from the first and second light groups (1, 2) and project it outside the luminous device (10). The light driver (4) comprises a dynamic boosting circuit (14) comprising a boost unit (8) and a capacitor branch (11), wherein the boost unit (8) is connected between the power input (3) and the capacitor branch (11) and is configured to provide a voltage output when receiving an electric supply from the power input (3). The light driver (4) is configured to increase the voltage output of the boost unit (8) upon receiving a cranking event signal from the vehicle control unit.

Description

A LIGHTING CIRCUIT FOR AN AUTOMOTIVE LUMINOUS DEVICE AND AN AUTOMOTIVE LUMINOUS DEVICE

[0001] This invention belongs to the field of lighting devices installed in automotive vehicles, and more specifically to the electronic assemblies used in these automotive lighting devices.STATE OF THE ART

[0002] During engine cranking, battery voltage drops and some functions may switch off depending on the severity of the cranking pulse.

[0003] It is accepted by customers today that lighting functions may switch off during the cranking process if there are severe conditions.

[0004] However, despite not being critical, it is at least quite unsightly (and can moreover lead to safety issues) when a luminous element switches off.DESCRIPTION OF THE INVENTION

[0005] The present invention provides a solution for these problems by means of an automotive luminous device comprising:a first light group configured to emit light to contribute to a first lighting function, a second light group configured to emit light to contribute to a second lighting function, the first light group and the second light group comprising at least one solid-state light source;a light driver comprising a power input, a data input, a first power output and a second power output, wherein the power input is intended to receive a power signal, the data input is configured to receive data from a vehicle control unit, the first power output is connected to provide electric supply to the first light group and the second power output is connected to provide electric supply to the second light group,whereinthe light driver comprises a dynamic boosting circuit comprising a boost unit and a capacitor branch, wherein the boost unit is connected between the power input and the capacitor branch and is configured to provide a voltage output when receiving an electric supply from the power input;the light driver further comprises a first buck converter and a second buck converter, wherein the first buck converter is arranged between the dynamic boosting circuit and the first power output, and the second buck converter is arranged between the dynamic boosting circuit and the second power output; andthe light driver is configured to increase the voltage output of the boost unit upon receiving a cranking event signal from the vehicle control unit.

[0006] A boost unit or step-up converter is a DC-to-DC converter that increases voltage, while decreasing current, from its input (power supply, usually the power input coming from the vehicle battery) to its output (load).

[0007] A buck converter or step-down converter is a DC-to-DC converter which decreases voltage, while increasing current, from its input (usually the output of the boost unit) to its output (connected to the power output of the driver to feed the corresponding light group). Buck converters provide much greater power efficiency as DC-to-DC converters than linear regulators and are preferred in automotive luminous devices.

[0008] Each driver has an optimal operation point, which differs from the operation point of light sources and from the voltage level provided by the vehicle battery. The use of boost and buck converters is a common practice to adapt the current to the different elements. The present invention is aware of this practice, but introduces the fact of the driver being able to increase the output voltage of the boost unit when receiving a cranking event flag from the body control module (BCM) of the vehicle, by means of the data input. As a consequence, the capacitor is able to store much more energy and prevent the lighting functions from being switched off in the event of a cranking event in severe conditions.

[0009] Data input provides the driver with useful information and, amongst other, with a cranking event flag, which is used in the present invention to perform an increase in the boost voltage level to minimize the hazardous effect of the cranking event in severe conditions.

[0010] In some particular embodiments, the light driver is configured to reduce the increased output voltage of the dynamic boosting circuit to be equal to operating voltage of the first light group after processing the cranking event signal.

[0011] In some particular embodiments, the first lighting function corresponds to at least one of Daytime Running Light (DRL), passing beam light, signature light, direction indicator light, front or rear position light and driving beam light. In some particular embodiments, the second lighting function corresponds to at least one of Daytime Running Light (DRL), passing beam light, signature light, direction indicator light, front or rear position light and driving beam light.

[0012] Lighting or signalling functions which require a lower voltage will receive a higher benefit from this invention, since the standard voltage will be lower and the voltage increase in the dynamic boosting circuit will be higher.

[0013] In some particular embodiments, the light driver is configured to increase the voltage of the boost unit to at least 50 V, preferably to at least 59 V, preferably to 60 V.

[0014] Despite current automotive applications only require this boost stage to increase the voltage up to 30 V, a higher voltage is preferred, since a greater amount of energy may be stored in the capacitor, thus minimizing the effects of the cranking event in severe conditions.

[0015] In some particular embodiments, the capacitor has a capacitance higher than 50µF, particularly higher than 80µF, particularly equal or higher than 100µF.

[0016] In the particular case of capacitors of 100µF, which are usually employed in automotive circuits, the energy stored can be increased by 4 times, since the voltage is doubled with respect to the standard use. Not all this energy will be used, but still the present invention is useful to increase the duration of the corresponding lighting function being turned on.

[0017] In some particular embodiments, the dynamic boosting circuit, the first buck converter and the second buck converter are arranged in the same electronic substrate.

[0018] The electronic substrate is also called printed circuit board (PCB). In some particular embodiments, the electronic substrate is a rigid electronic substrate. Alternatively, the substrate can be made flexible. A rigid substrate should be understood in the sense of what the skilled person would construe. A skilled person knows the difference between a rigid substrate and a flexible substrate. Although every material is “flexible” in the sense that it has a stress-strain curve, a substrate which does not deform by its own weight when held by one of its ends is deemed to be rigid, while a substrate which suffer a substantial deformation when held by one of its ends is considered to be flexible. In any case, board manufacturers offer a “flexible” model and a “rigid” model, while any skilled person knows the difference between them.

[0019] In a second inventive aspect, the invention provides an automotive luminous device comprisinga lighting circuit according to the first inventive aspect;an optical element arranged to receive light emitted from the first light group and from the second light group and project it outside the luminous device.

[0020] In some particular embodiments, the optical element is a light guide or a reflector.

[0021] An optical element is an element that has some optical properties to receive a light beam and emit it in a certain direction and / or shape, as a person skilled in automotive lighting would construe without any additional burden. Reflectors, collimators, light guides, projection lenses, etc., or the combination thereof are some examples of these optical elements which are useful for transforming the light beams emitted by the light source into an acceptable light pattern for the functionality chosen for the lighting device.

[0022] In some particular embodiments, the solid-state light sources are light emitting diodes.

[0023] The term "solid state" refers to light emitted by solid-state electroluminescence, which uses semiconductors to convert electricity into light. Compared to incandescent lighting, solid state lighting creates visible light with reduced heat generation and less energy dissipation. The typically small mass of a solid-state electronic lighting device provides for greater resistance to shock and vibration compared to brittle glass tubes / bulbs and long, thin filament wires. They also eliminate filament evaporation, potentially increasing the lifespan of the illumination device. Some examples of these types of lighting comprise semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma or gas. These light sources are specifically advantageous, since they provide the required luminous properties for the automotive regulations with a high efficiency and reliability.

[0024] In some particular embodiments, the data input is connected to a bus communication interface, such as Local Interconnect Network or Controller Area Network (CAN) or Clock Extension Peripheral Interface.

[0025] CAN buses are commonly used in automotive luminous devices, and allow a bidirectional exchange of information between the Body Control Module (BCM) and the driver.

[0026] Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein.

[0027] In this text, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:

[0029] shows a luminous device according to the invention installed in an automotive vehicle.

[0030] shows an electronic scheme of some of the elements contained in this luminous device shown in.

[0031] shows some data associated with the improvement presented in the invention.

[0032] In this document, the following reference numbers have been used:1 First group of LEDs2 Second group of LEDs3 Power input4 Light driver5 Data input6 Power output for first light group7 Power output for second light group8 Boost unit9 Light guide10 Headlamp11 Capacitor branch12 Buck converter for first light group13 Buck converter for second light group14 Dynamic boosting circuit100 Automotive vehicleDETAILED DESCRIPTION OF THE INVENTION

[0033] The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

[0034] Accordingly, while embodiment can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit the scope of protection to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

[0035] shows a luminous device 10 according to the invention installed in an automotive vehicle 100.

[0036] This luminous device 10 is a headlamp, and is configured to provide the usual functions, i.a., Daytime Running Light (DRL), low beam, high beam, turn indicator light, front Position Light and Direction Indicator Light.

[0037] These functions are provided by light sources contained in the luminous device. The light emitted by these light sources is received by a light guide 9 and projected outside the headlamp 10.

[0038] shows an electronic scheme of some of the elements contained in this luminous device shown in.

[0039] As can be seen in this figure, there is a first group of LEDs 1 configured to emit light to contribute to obtain the DRL function. This first group contains a plurality of LEDs.

[0040] There is also a second group of LEDs 2, which are configured to emit light to contribute to obtain the Direction Lamp function. This second group also contains a plurality of LEDs.

[0041] A light driver 4 is arranged to provide a controlled power supply to these two groups of LEDs 1, 2. This light driver 4 comprises a power input 3, a data input 5 and at two power outputs 6, 7.

[0042] The power input 3 is intended to receive a power signal from the vehicle battery. This power signal usually has a voltage of 12 V and is used to provide the power supply needed by the LEDs to perform their respective functions.

[0043] The data input 5 is configured to receive data from aBody Control Module (BCM) of the vehicle 100 via a CAN bus, thus allowing a bidirectional exchange of information between these two entities, including instructions, signals and diagnosis information. For the present invention, it is interesting that the BCM may send the driver a flag concerning the cranking event when the user turns on the vehicle.

[0044] The power outputs 6, 7 are intended to provide the electric supply to the first and second groups of light sources.

[0045] To do so, there are some intermediate elements between the power input 3 and the power outputs 6, 7 to prepare this power supply.

[0046] Firstly, there is a dynamic boosting circuit 14. This circuit comprises a boost unit 8 and a capacitor branch 11. The boost unit 8 is arranged between the power input 3 and the capacitor branch 11. This boost unit 8 is configured to increase the voltage from the level provided by the vehicle battery (as said before, 12 V) to an amount that will be optimal to cope with the needs of the groups of LEDs. In an embodiment, this amount may be for example 30 V. This optimal boost voltage is aimed to optimize the driver’s global efficiency during normal mode.

[0047] A capacitor branch 11 is connected between the output of the boost unit 8 and ground. This capacitor has a capacitance value selected based on power requirements of the first group of LEDs 1 and the second group of LEDs 2 to provide optimal power to the boositing unit 8. In an embodiment, the capacitance value may be, for example, 100µF and can store energy and ensure continuous operation of the light groups.

[0048] Finally, two buck converters 12, 13 are arranged between the dynamic boosting circuit 14 and the power outputs 6, 7. A buck converter is a DC-to-DC converter which decreases voltage and increases current. The first buck converter 12 is arranged between the dynamic boosting circuit 14 and the first power output 6, and is intended to prepare the voltage to feed the first light group 1. The second buck converter 13 is arranged between the dynamic boosting circuit 14 and the second power output 7, and is intended to prepare the voltage to feed the second light group 2.Hence, the correct voltage may be supplied to each of the light groups 1, 2.

[0049] When the light driver 4 receives the cranking event flag from the BCM of the vehicle 100 via the data input 5 such as a CAN bus, it provides instructions to the boosting unit 8 to increase the voltage level from 30 V to 60 V. The boosting unit 8 along with the capacitor network 11 of the dynamic boosting circuit 14 provides the necessary increased voltage. Hence, the hazardous effect of the cranking event in severe conditions such as during bad weather conditions are minimized.

[0050] By this increase, the energy stored by the capacitor is 4 times more than in the standard case, since the voltage is doubled with respect to the normal use. Not all this energy will be used, but still the present invention is useful to increase the duration of the corresponding lighting function being turned on.

[0051] shows data associated with the improvement presented in the invention. In particular, it shows the power received by the first group of LEDs in two different responses to a standardised crank pulse: first response (represented by the dashed line) is the case where the invention is not applied, and the boost unit only increases the voltage to 30 V when the cranking event is to take place. The second response (represented by the continuous line) is the response associated to a system according to the present invention, where the driver commands the boost unit to increase the voltage to 60 V when the cranking event is to take place. In the first case, the first group has power to keep up during 6 ms before switching off, while in the second case, the first group has power to keep up during 15 ms before switching off. Further, the light driver 4 is configured to reduce the increased output voltage of the dynamic boosting circuit 14 to be equal to operating voltage of the first light group 1 after processing the cranking event signal. The voltage reduction is performed by the light driver 4 after time lapse of the engine cranking signal. The boosting of the voltage in the event of the engine crancking signal and the subsequent reduction of the voltage to be equal to the operating voltage of the first light group ensures that there is minimal time lapse of the disruption in functioning of the first light group in the case of, for example, a strong engine cranking pulse and in some cases for example, when there is a weak cranking pulse, the first light group could still function at the time of engine cranking. Therefore, by implementing this invention, we are able to maintain the power supply for a longer duration of time.

[0052] Additionally, in an embodiment, when the cranking pulse is weak and the vehicle is operating in normal operating condition, the present invention enables the power supply to be provided for both the first light group and the second light group, thereby maintaining the functional state of the LEDs at the time of the cranking pulse.

Claims

A lighting circuit for an automotive luminous device (10) comprising:a first light group (1) configured to emit light to contribute to a first lighting function, a second light group (2) configured to emit light to contribute to a second lighting function, the first light group (1) and the second light group (2) comprising at least one solid-state light source;a light driver (4) comprising a power input (3), a data input (5), a first power output (6) and a second power output (7), wherein the power input (3) is intended to receive a power signal, the data input (5) is configured to receive data from a vehicle control unit, the first power output (6) is connected to provide electric supply to the first light group (1) and the second power output (7) is connected to provide electric supply to the second light group (2),whereinthe light driver (4) comprises a dynamic boosting circuit (14) comprising a boost unit (8) and a capacitor branch (11), wherein the boost unit (8) is connected between the power input (3) and the capacitor branch (11) and is configured to provide a voltage output when receiving an electric supply from the power input (3);the light driver (4) further comprises a first buck converter (12) and a second buck converter (13), wherein the first buck converter (12) is arranged between the dynamic boosting circuit and the first power output (6), and the second buck converter (13) is arranged between the dynamic boosting circuit and the second power output (7); andthe light driver (4) is configured to increase the voltage output of the boost unit (8) upon receiving a cranking event signal from the vehicle control unit.Lighting circuit according to claim 1, wherein the light driver (4) is configured to reduce the increased output voltage of the dynamic boosting circuit (14) to be equal to operating voltage of the first light group (1) after processing the cranking event signal.Lighting circuit according to claim 1, wherein the first lighting function corresponds to at least one of Daytime Running Light (DRL), passing beam light, signature light, direction indicator light, front or rear position light and driving beam light.Lighting circuit according to any of the preceding claims, wherein the second lighting function corresponds to at least one of Daytime Running Light (DRL), passing beam light, signature light, direction indicator light, front or rear position light, and driving beam light.Lighting circuit according to any of the preceding claims, wherein the light driver is configured to increase the voltage of the boost unit to at least 50 V, preferably to at least 59 V, preferably to 60 V.Lighting circuit according to any of the preceding claims, wherein the capacitor has a capacitance higher than 50µF, particularly higher than 80µF, particularly equal or higher than 100µF.Lighting circuit according to any of the preceding claims, wherein the dynamic boosting circuit (14), the first buck converter (12) and the second buck converter (13) are arranged in the same electronic substrate.Automotive luminous device comprising a lighting circuit according to any of the preceding claims;an optical element (9) arranged to receive light emitted from the first light group (1) and from the second light group (2) and project it outside the luminous device (10).Automotive luminous device according to claim 8, wherein the optical element is a light guide or a reflector.Automotive luminous device (10) according to any of claims 8 or 9, wherein the solid-state light sources are light emitting diodes.Automotive luminous device (10) according to any of claims 8 to 10, wherein the data input is connected to a bus communication interface, such as Local Interconnect Network or Controller Area Network or Clock Extension Peripheral Interface.

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