LED Lights Future Development Trends and Application Analysis

After the LED car headlights have undergone the development stage of technical verification and concept car demonstration in recent years, they have finally ushered in the market prospects that are expected to be used in production cars. There are three signs: Toyota's Lexus LS600h is the world's The first car to use a LED front light source, but it only uses LEDs on low beam, and the remote light source is still halogen. The Audi R8 features full LED headlamps, while the LED used in automotive lighting is provided by Lumileds and Osram. The Cadillac Platinum Escadael Platinum sports car is the first multi-purpose sports car with LED headlamps. Obstruct the LED light source to quickly develop the car

After the LED car headlights have undergone the development stage of technical verification and concept car demonstration in recent years, they have finally ushered in the market prospects that are expected to be used in production cars. There are three signs: Toyota's Lexus LS600h is the world's The first car to use a LED front light source, but it only uses LEDs on low beam, and the remote light source is still halogen. The Audi R8 features full LED headlamps, while the LED used in automotive lighting is provided by Lumileds and Osram. The Cadillac Platinum Escadael Platinum sports car is the first multi-purpose sports car with LED headlamps.

Obstructing LED Light Sources from Rapidly Exploiting Unfavorable Factors in the Automotive Market

Does the above milestone event mean that the LED headlamps will immediately become an innovative technology that dominates the automotive lighting industry? According to experts predict: Maybe not. Because even if the cost of LEDs can continue to decline at the rate foreseen by Moore's Law, it will take many years to achieve the same price as HID (High Intensity Discharge) deuterium lamp; and the LED family's cost will be reduced to that of halogens. If the lights are equal, you will need to go through a longer period of time.

According to Fischer, president of Hella, the size of automotive LEDs currently represents only a small percentage of the market share of light sources, so it is in favor of high-volume models (such as the GM/Chevrolet Malibu model). The matching supply is of great interest. However, LED needs to overcome a series of technical and cost problems to achieve the level of supply as large quantities as Malibu models, and at least a decade away.

Visteon pointed out that the LED's pace of entering the market is indeed slower than originally expected. We predicted in 2004 that LED lights would soon be injected into the city and HID would be eliminated. Obviously, the current situation is not the same, although it is always expected that LED technology can evolve faster than reality. It seems that the high cost is not the only factor that hinders the LED market. There are still challenges in terms of technical performance that need to be overcome.

For example, for a single light source, the LED's light intensity is still insufficient. A single point is not bright enough to achieve the following wishful calculations: Reducing the number of LED light sources that make up a combination of luminaires will help to reduce the footprint of automotive luminaires and allow for flexible placement, simplifying the wiring and installation of lighting systems and reducing production costs.

At present, the mainstream status of the LED supply chain is: the LED light source components supplied by Hella to the General Motors Cadillac Escalade are purchased from Osram, while the Koito LED uses the Nichia light source products. Toyota's LS600h model; Philips Lumileds supplies LED light sources to AL (automotive lighting) companies, which in turn configures the lighting system for the Audi R8.

According to Koito’s European and American operations managers, they do not plan to be jailed and self-define the types of light sources and their purchasers, regardless of who they produce (Phillips, Osram, or Toyota Gosei). Obviously, the first-tier suppliers of lighting system components try to maintain the flexibility of their own procurement of light source components, and want to observe: Which device manufacturer's product technology can be the fastest and most cost-effective.

The photoelectric conversion (light energy density) index of today's LED batch products reaches 80 lumens per watt (80 lm/W), while the HID lamp is 90 lm/W and the halogen lamp is 201 m/W. In addition, according to Hala, the latest LED prototype has reached 161lm/W. Hella also predicts that in the next 3-5 years, the LED light intensity from the same power chip will increase by 50%. This not only means that LED lamps will be brighter, but also reflects the reduction of energy consumption, thereby improving the vehicle's fuel economy.

It has been estimated that replacing halogen lamps with LEDs can increase the vehicle's mpg (miles per gallon of fuel) index by about 0.25. When it comes to implementing daylight driving regulations in Europe, it is also possible to increase the mpg boost value to 0.5. The Lexus model manager pointed out that the application of LED lamps will greatly contribute to improving the fuel economy of the vehicle.

However, LEDs with higher light intensity also emit more heat, and the compact arrangement of the lamps makes the area available for heat dissipation smaller. It is true that low-power LED devices in the semiconductor category generate much less heat than halogen or HID lamps, but much of the latter's heat is generated outside of the fixtures, while LEDs have low power consumption and low heat generation. It is necessary to conduct heat in tiny silicon wafers.

LED thermal management is a big problem

Even a small amount of heat must be concentrated on a chip-sized device to conduct and diverge, and a small increase in the thermal capacity of the device can also cause a sudden increase 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 light-emitting components in one luminaire so that the heat output of the individual components is smaller, and then disposing them in a larger space makes it easy to dissipate heat. This is the technique used by Kosaka’s headlights when it comes to matching the headlights of Toyota’s Lexus LS600h.

Each Cadillac Escalade Platinum headlight consists of seven LED tubes, of which five are used for the short-range beam and the other two are used as the remote source. They all have their own active heat sink - a cooling fan (similar to the small built-in fan in a desktop computer).

According to Hella, thermal management is a particularly troublesome design field for them. In terms of program selection, emphasis is placed on virtual simulation methods to evaluate the optimization. However, the selection of simulation tools (simulation software packages) must pass sufficient experimental data. . He pointed out that the challenge to the thermal management problem is not only the heat conduction, but the heat pool can be used to take out the heat generated by the LED components, and also to solve the ventilation problem, so that heat is emitted from the lighting fixture. 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 working mode for LED lamps, that is, when the lamp temperature rises to a predetermined warning value, it automatically switches to the security mode that reduces the lamp power supply by 20%. It is said that this degree 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 vehicle advantages

Since all the above-mentioned cost barriers and layered technical difficulties have been encountered, why did OEMs and their lighting system suppliers still insist that Castle Peak will not push its LED to enter the market without relenting?

This is due to the fact that this new light source allows unprecedented flexibility in the style design and layout of automotive lamps and is suitable for the individualization of models. Moreover, the LED's light output power density is comparable to that of HID lamps. It is hoped that all existing lighting technologies will be eliminated and the auto lighting market will be dominated.

According to Cadillac Escalade Platinum's model product manager, LED's luminescence spectrum is close to that of daylight, which makes the light emitted from it more effective than other light sources for reflecting objects (such as road traffic signs/lines), and thus can be farther away. The distance allows drivers to find out as soon as possible to improve traffic safety. He pointed out that the road signs almost all use passive glow reflections, because the light color of the LED is close to that of daylight, so the driver can easily find and see the traffic signs at night as well as during the day.

The color temperature of the LED lights is 5500-6000K, which is whiter than other light sources, because the light blue color temperature of the HID lamp is 4000K, and the halogen light is **3000K. Therefore, in the optical design of HID luminaires, the bluest portion of the spectrum needs to be shifted to the edge of the spot of the spot where they are used, because these regions are the places where the driver's eyes usually do not pay attention, thereby reducing the color to the human eye. Uncomfortable interference.

However, for oncoming driver drivers, Blu-ray will still cause the driver to dazzle and affect the safety of the vehicle when the vehicle crosses the marginal area. In the aspect of anti-glare interference, LED headlamps have the potential advantages: they can not only protect the driver's comfortable vision, but also not cause visual impairments to the driver of the adjacent/compartment driver. Due to the use of different light sources (LEDs/halogens) for the near/distance light of the headlights of the Toyota Lexus, the owner of the LS600h may be troubled by the apparent color difference of different light sources.

Another great advantage for AL (automotive lighting) LED headlights is that the EU has passed the DRL (Daylighting) Regulations, which will take effect in 2012, and it's Canadian-recommended (allows for daylight to use DFL as a DRL. ) Unlikely, EU regulations mandate the use of headlights during the day. As long as the vehicle is in motion, headlights must be turned on, making 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 fulfilled is that LED headlights can use spot arrays to combine the active features of headlights without any need for the current type of devices. Moving parts. Such an active lighting system (for example, an active security function that changes the direction of light irradiation depending on the steering angle) may require the use of a larger number of light pipes than used in the past to form a dot matrix. Valeo is developing a more reliable new adaptive headlamp system based on this idea.

Hella Fischer pointed out that this change in the lighting system is also consistent with and reflects the general trend that the mechanical functions of contemporary automobiles are being gradually replaced by the (electronic + electronically controlled + electric) all-electric system. The same set of LED arrays can be used as both headlamp headlights and also for turn signals. They only use their own optical mirror covers when they play different lighting functions.

As a general turn signal, it is only necessary to arrange LED arrays on both sides of the vehicle body, plus a simple switching function. To take advantage of the active security of the intelligent front lighting, so that the front light beam can always illuminate the road in front of the vehicle in synchronization with the turning trajectory of the vehicle, more light source lattices need to be arranged and a more complex light point electricity must be adopted. Control, in accordance with the steering input to control the light and shade combination of the variable spot array and its mirror, so as to synchronously change the direction of the front light beam.

In short, borrowing from Mr. Asif Anwar of Strategy Analytics, a market research and consulting firm, the LED headlamps are just starting to take off, but they will be an extremely fast-growing area for the automotive LED market. It is estimated that by 2012, the LED headlamp market will reach 80 million US dollars. LED will become the new darling of automotive lighting system with its excellent safety, reliability, energy-saving and aesthetic design features, which will bring new opportunities for the upgrade and revolution of automobile lights.