LED car headlights have finally entered the market prospects for production cars after years of technical verification and concept car display. There are three landmark events: Toyota's Lexus LS600h is the world's first A listed car with LED headlights, but it only uses LEDs on the low beam, and the remote source is still a halogen. The Audi R8 features a full LED headlamp, while the LEDs used in automotive lighting are supplied by Lumileds and Osram. The Cadillac Escalade Platinum Platinum Multi-Player is the first multi-purpose sports car with LED headlamps.
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Obstructing the LED light source to quickly develop the disadvantages of the automotive market
Does the above-mentioned milestone event mean that LED headlamps will immediately become an innovative technology in the field of mastering automotive light sources? According to experts predict: maybe not. Because even if the cost of LEDs can continue to decline at the foreseeable rate of Moore's Law, it will take years to reach the same price as the HID (high-intensity discharge) xenon lamp; and the cost of the LED family should be reduced to halogen. If the lights are comparable, it will take a longer period of time.
According to Hella's president Fischer, the size of automotive LEDs currently accounts for only a small percentage of the light source market, so it is aimed at high-volume models (such as the GM/Chevrolet Malibu models). The matching supply is extremely interesting. However, LEDs have to overcome a series of technical and cost challenges in order to achieve the same high-volume supply level as the Malibu models, at least for a decade.
Visteon pointed out that the pace of LED entry into the market is indeed slower than originally expected. In 2004, we predicted that LED lights would soon be blown into the market and HID would be eliminated. Obviously, the current situation is not the case, although it has been expected that LED technology can evolve faster than reality. It seems that high cost is not the only factor that hinders the LED market, and there are still challenges in technical performance that need to be overcome.
For example, in the case of a single light source, the illumination intensity of the LED is still insufficient. If the single point is not bright enough, it is difficult to achieve the following wishful thinking: reducing the number of LED light sources constituting the combined luminaire will help to reduce the space occupied by the automobile luminaire and be easy to flexibly arrange, and simplify the wiring and installation of the lighting system and reduce the production cost.
The current mainstream of the LED supply chain is: Hella's LED light source components for the GM Cadillac Escalade model are purchased from Osram, while Koito's LEDs use Nichia's light source products for Toyota. The LS600h model; Philips Lumileds supplies LED light source to AL (Automotive Lighting), which in turn configures the Audi R8 with a light system.
According to Koito's manager of the European and American operations department, they will not be able to customize the type of light source and its purchasers, regardless of who they are from (Philips, Osram, or Toyota Gosei). Obviously, the first-tier suppliers of lighting system components are trying to maintain the flexibility of their own procurement of light source components. I want to observe: which device manufacturer's product technology can be the fastest and most cost-effective.
Today's LED batches offer a photoelectric conversion (light energy density) of 80 lumens per watt (80 lm/W), while HID lamps are 90 lm/W and halogen lamps are 201 m/W. According to Hella, the latest LED R&D prototype has reached 161 lm/W. Hella also predicts that LED light intensity from the same power chip will increase by 50% in the next 3-5 years. This not only means that LED luminaires will be brighter, but also reflects the reduction in energy consumption, thereby improving the fuel economy of the vehicle.
It is estimated that replacing halogen lamps with LEDs can increase the vehicle's mpg (miles per gallon of fuel) index by about 0.25. When the regulations for daylighting in the day are implemented in Europe, the mpg boost value can be increased to 0.5. Lexus's model manager pointed out that the application of LED lamps will greatly contribute to the improvement of fuel economy of the whole vehicle.
However, LEDs with higher light density also emit more heat, and the compact arrangement of the lamps makes the area available for heat dissipation smaller. It is true that low-energy LED devices in the semiconductor category generate much less heat than halogen lamps or HID lamps, but most of the latter's heat is generated outside the fixture, while LEDs have low power consumption but low heat. It is to conduct heat by squeezing it inside tiny silicon wafers.
LED thermal management is a big problem
Even if the small amount of heat is concentrated on the chip-sized device to conduct and diverge, the small heat capacity of the device will cause a sudden rise in the LED temperature. The operating temperature of the LED must be kept below 150 °C. One solution to this heat dissipation problem is to use a larger number of LED lighting elements in one luminaire, so that the heat generation of the single parts is smaller, and then they are arranged in a larger space to make it easier to dissipate heat. This is the technique used by the small Xenon headlights for the Toyota Lexus LS600h.
Each headlamp of the Cadillac Escalade Platinum consists of seven LED tubes, five for short-range beams and two for remote sources. They all come with their own active heat sink - a cooling fan (similar to the built-in small fan in a desktop computer).
According to Hella, thermal management is a design field that makes them particularly painstaking. In the choice of the program, the virtual simulation method is used to evaluate the optimization. In the selection of the simulation tool (simulation software package), it must be verified by sufficient experimental data. . He pointed out that the challenge of thermal management issues not only comes from heat conduction, but also the heat generated by the LED components can be taken out by means of a "hot pool" device, and the ventilation problem is solved to allow heat to be dissipated from the lamp device. If natural ventilation alone is obviously not enough, Hella decided to add a built-in fan to the luminaire.
Valeo's thermal management strategy is a must. It sets a safe mode of operation for LED luminaires, that is, when the temperature of the luminaire rises to a predetermined warning value, it automatically switches to the security mode that reduces the power supply of the luminaire by 20%. It is said that this level of power supply reduction has little effect on the brightness of the light, but it can significantly suppress the level of heat.
LED light source car advantage
In the face of the above-mentioned various cost barriers and layers of technical difficulties, why do OEMs and their lighting system suppliers still have to insist that Aoyama does not relax and push LEDs into the market?
The reason is: this new light source can make the style design and styling of the car luminaire have unprecedented flexibility and be suitable for the individualization of the car. Moreover, the light output power density of the LED can match the HID luminaire, so it is very It is hoped that all other existing lighting technologies will be eliminated and the market for the lamp will be dominated.
According to the model product manager of Cadillac Escalade Platinum, the LED's luminescence is close to daylight, which makes it more effective to reflect light from objects (such as road traffic signs/lines) than other sources. The distance allows drivers to find out early and improve driving safety. He pointed out that almost all road signs use passive glow reflection, because the color of the LED is close to daylight, so the driver can easily find and see the traffic signs at night as well as during the day.
The color temperature of LED lights is 5500-6000K, which is whiter than other light sources, because the light blue color temperature of HID lamps is 4000K, and the halogen light is yellow 3000K. Therefore, when performing the optical design of the HID luminaire, it is necessary to move the bluest part of the spectrum to the edge of the spot spot, because these areas are places where the driver's eyes usually do not pay attention, thereby reducing the color to the human eye. Discomfort.
However, for the oncoming car driver, the blue light will cause the other party to dazzle and affect the car safety when the vehicle crosses the marginal area. In terms of anti-glare interference, LED headlights have the potential advantage of not only protecting the comfort of the driver of the car, but also the visual impairment of the driver/car driver. Because the proximity/remote light of the headlights of the Toyota Lexus uses different light sources (LED/halogen), the owners of the LS600h may be plagued by the poor coloration of different light sources.
Another major advantage for AL (automotive lighting) LED headlamps is that the European Union has adopted the DRL (daytime running light) regulations that will enter into force in 2012, which is in line with Canada's recommended regulations (allowing daylights to be used as DRLs) Unlike the EU regulations, it is mandatory to use headlights during the day. As long as the vehicle is in the middle of driving, the headlights must be turned on, which makes the advantages of low energy consumption and long life of the LED light source more obvious.
According to Valeo's CEO, another potential that has not yet been realized is that LED headlights can use the array of light spots to combine the active functions of the headlights without any need (currently necessary for such devices) Moving parts. Such active lighting systems (eg, active security functions that vary the direction of illumination as a function of steering angle) may require the use of more light tubes than previously used to form a lattice. Valeo is following this idea to develop a more reliable new adaptive headlamp system.
Hella Fischer pointed out that this change in the lighting system is also in line with and reflects the general trend that the mechanical functions of contemporary cars are gradually being replaced by (electronic + electronically controlled + electric) all-electric systems. The same set of LED arrays can be used as both a light source for the headlights and a turn signal, but with separate optical mirrors for different lighting functions.
As a general turn signal, it is only necessary to arrange LED arrays on both sides of the body, plus a simple switching function. To take advantage of the active security of smart front lighting, so that the front light beam can always illuminate the road ahead with the vehicle's steering trajectory, it is necessary to arrange more light source lattices and take more complicated light spot Control, according to the steering input to control the light and dark combination of the variable point array and its mirror, thereby synchronously changing the direction of the front beam.
In short, borrowing from Mr. AsifAnwar of StrategyAnalytics, a market research and consulting firm, LED headlamps, although just beginning, will be an area where the automotive LED market is growing rapidly. It is estimated that by 2012, the LED headlamp market will reach 80 million US dollars. LED will be the new darling of automotive lighting system with its excellent safety, reliability, energy saving and aesthetic design, bringing new opportunities for the upgrade and revolution of automotive lights.
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