Although there are some shining examples of LED applications in automotive headlamps, the adoption rate is still not as fast as one would expect, especially for the surge in solid-state lighting (SSL) products for general lighting. . Automotive applications present a unique design challenge at a relatively high cost. However, LEDs are expected to add unique features to the headlights. Moreover, we will propose a design option that will create a headlight system with rugged functionality.
You can compare general lighting with car lighting. We all remember the traditional tungsten light bulb. At the end of 2013, 40W and 60W incandescent bulbs commonly used in most American homes were banned from being manufactured in the US or imported from abroad; however, they are still available for purchase. It should also be noted that the 75W and 100W bulbs were gradually phased out in 2012.
The reason for the elimination of these lamps is that the US Environmental Protection Agency (EPA) requires an increase in the efficacy of electro-optical output. The main reason for this requirement is to help reduce electricity consumption (and therefore power generation) because, in fact, US residential lighting accounts for about 14% of US electricity consumption (Source: Energy Information Administration). Solid-state LED lights require only about 1/8 of the power to produce the same lumens of light output, so LED lights have successfully entered our world today.
The evolution of illuminators from incandescent lamps to solid-state electronic lamps is similar to the shift in vehicle lighting currently occurring in the automotive industry. Although red LED lights have been used in taillights for more than 10 years, only recently, changes in the interior and forward lighting systems have led to a significant increase in the adoption rate of LED lights. For example, more than 70% of automotive interior lights and more than 45% of instrument display backlighting use LED lights. In contrast, current 55% of daytime running lights (DRL) and about 5% of headlights use LED lights. Although the headlights (low beam, high beam, fog light) represent the biggest business opportunities, but also the market with the lowest penetration rate, many people have discovered this contradiction, I am one of them. One of the main reasons for this apparent contradiction is cost, and automakers are unable to provide LED headlights at the price consumers are willing to pay.
Car headlights
Before discussing the background reasons for the low adoption rate of headlights, it is useful to know why many drivers and even original equipment manufacturers prefer LED lighting solutions. Reasons for LED lighting solutions being favored include but are not limited to the following:
Performance and Design Flexibility - The LED's small form factor provides design flexibility and the LEDs offer a wide range of dimming capabilities. Remember that the human eye is very sensitive to small deviations in light output.
Energy savings and lower CO2 emissions – LEDs not only have higher efficiency, they reduce the energy required to power them, but they also have a significantly extended life cycle.
Cost – This feature seems counterintuitive, but in non-headlight applications, continued cost reduction, durability and superior quality have made LED a new standard for ultimate consumer value.
Regulatory – Many government regulations dictate requirements for daytime running lights and headlights, as well as other lighting applications, which have led to an increase in demand for LED lighting.
Audi is widely regarded as the leader in LED applications, and I think anyone will not be surprised by this because Audi uses LEDs in almost any external automotive lighting application. Anyone who sees Audi's famous "eyebrow" daytime running lights in the rearview mirror will be very eye-catching. In addition, Audi is the first car manufacturer to use LED headlights, used in the 2004 Audi R8. Moreover, the company is well known for its matrix headlights that are capable of directing a beam of light (an example of beam control is shown in Figure 1).
Figure 1: This figure shows how a matrix LED headlight scatters light.
So why aren't LED headlights as popular as LEDs used in other forms of automotive lighting? The answer is of course the cost. Other products that can replace LED headlights include incandescent, halogen or high-density discharge (HID) xenon lamps. The price of comparable LED lamps may be 100% higher than halogen headlamps (first introduced in Europe in 1962, but not used in the United States in 1978), than HID xenon lamps (to achieve comparable performance with HID xenon headlamps, a need The LED solution is much more expensive than the lower performance halogen lamp). Incidentally, the first HID Xenon headlights appeared in the BMW 7 Series in 1991.
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