LED Ahead

Car headlamps will be transformed by light-emitting diode technology in the next three years, according to two major automotive suppliers.

At this week’s Frankfurt Motor Show Valeo and Hella revealed that they are developing white LED lights for a variety of front lighting applications. Hella demonstrated what it claims is the first prototype LED headlight to meet all current requirements for main and dipped beam patterns.

LEDs are semiconductors which turn electricity directly into light. Advantages include lower power consumption, compact size, and long life. Red LEDs are commonly used for high-level brake lights, and recently they have been adopted for the main rear lights on vehicles such as the new Range Rover.

One car maker is expected to introduce a model with white LED running lights this year.

According to Valeo, which is working with partners Valeo Sylvania in the US and Ichikoh of Japan, LED front lights will last longer than the vehicle itself, freeing the car maker from designing in-built provision to replace them. Their compact size will make for more flexibility in styling, and Valeo believes they will first be used in top-end models.

Hella technical marketing director Wolfgang Hendrischk said the prospect of using LEDs for headlamps and fog lamps had become possible because the light output of white LEDs has increased dramatically in the last few years. This trend is expected to continue.

Currently LEDs are more expensive than incandescent lamps, but the cost per unit of light output is expected to reduce.

Hendrischk said LED headlamps were expected to be market-ready in time for 2006 model year cars, which manufacturers are designing now. Remaining obstacles include the need to change regulations to allow the use of LEDs, but this is in hand and expected to be achieved by 2006.

Technical issues include keeping the headlights cool. If the chip exceeds around 125 degrees Centigrade it stops working. High power LEDs would need heat sinks or forced air cooling because of the heat they produce themselves and because they would be close to the engine bay.

Hendrischk also said that producing sufficient light is not a problem, nor is achieving wide illumination up to 20-30m from the car. ‘But it is difficult to shine light into the far distance,’ he said. The illuminated area of an LED is quite large compared with the filament of a bulb, needing a very large lens to project it.

With its Japanese partner Stanley, Hella has been working on combining multiple diodes into the space of one normal LED. Shades are used to create the correct beam pattern with sharp cut-off lines.

None of these problems apply to running lights, which are a legal requirement in several European countries. Constant use of dipped headlights increases fuel consumption by 0.2 litres/100km at a time when manufacturers are under pressure to reduce it.

On the web