LED lamp

LED headlights are headlights, which LEDs / LEDs ( light - emitting diodes, English light emitting diode) are used as light sources.

• 7.1 parking lights and daytime running lights
• 7.2 Legal requirements

• 8.1 advantages
• 8.2 disadvantages

Principle of operation

LEDs are devices made ​​of semiconductors. In the LED chip, the energy of electric current at a relatively low heat generation is converted into light energy. In this case, a very narrow-band light is emitted. (monochromatic LED, classic colors are red, yellow, green, orange). For realizing a white LED can be either the light of different color LEDs, or superimposed part of the light from blue LED by a fluorescent phosphor to be transformed into yellow light mixed with the remaining blue component resulting white light. Since the individual LEDs have a low light output compared to incandescent or xenon gas discharge lamps, multiple LEDs are usually bundled extensively interconnected in so-called LED modules. This can be either provided with its own bundling look or an overall look for the entire module can be used each LED.

Construction

The LEDs with optics ( shaped from the transparent capping lenses, superior lenses, sometimes slender parabolic mirror ) combined individually in order to concentrate the light. The individual radiation characteristics averaged out. Their mistakes ( orientation and angle ) to the total directivity, but is yet far less than that with incandescent or gas discharge lamps ( high pressure short arc lamps) achievable Larger LED headlights need a heat sink to cool the temperature-sensitive LEDs sufficient. The LEDs are, in turn, connected in groups in series, and these parallel to an array and from a constant-current source (in the simplest case, a resistor, for larger lamps, an electronic circuit or a switching regulator, for mains powered spotlights a ballast capacitor, a rectifier and a smoothing capacitor ) supplied.

The electronics not only enables a brightness control, but - in a mixed configuration - even continuous change in light color through additive color mixing of LEDs of the primary colors red, green and blue.

Use

LED headlights are increasingly replacing other lights, because they last longer and are compared to incandescent about two to three times more efficiently and correspondingly less heat emit radiation. Areas of application are light shows, stage and nightclubs, as well as surgical lights. Light microscopy uses long small LED spotlight.

Small LED spotlights are increasingly replacing halogen dichroic reflector lamps for mains operation and for operation on a 12 -volt AC transformer, as it is also used for low-voltage halogen systems.

Ring-shaped lamps in many self -focusing white or single color LEDs are also used for object recognition in automation technology.

LED infrared illuminator work with radiating near-infrared LEDs and are used in the object monitoring using surveillance cameras.

Units of red, green and blue LED groups are able to generate almost any color. They are used among other things as effect light for stage lighting or in museums. So that no color change mechanism, or more color filters are necessary and the power supply is less expensive.

Life

LEDs, depending on the data sheet a lifespan of up to 100,000 hours, which they can easily exceed if they are not wired wrong or unprotected. The life is very temperature dependent. LEDs in lamps to be operated at higher temperatures, so that its lifetime is reduced to 15000-45000 hours. This is due to the fact that you want per LED obtain a high light yield and therefore operates with a load whose current.

The AC power is working with rectifiers and constant-current buck converters to keep losses at the optimum operating condition. In this down-converters Electrolytic capacitors are used with significantly lower lifetime functional reasons.

LED headlights on motor vehicles

In automotive lighting, three basic types of the LED insert can be distinguished:

• Lights, where only additional functions using LED technology are designed as parking light / position light ( daytime running lights ), turn signals, brake light, rear fog light, reversing light, number plate light or lights.
• Headlights that realize the low beam LED technology.
• Full-LED headlights, in which all functions previously mentioned as well as the high beam LED technology are realized.

Furthermore, there are also indicators on motor vehicles to distinguish Stand-/Positionslicht ( daytime running lights ) and main lighting functions ( Abblend-/Fernlicht ). The functions are usually implemented as a reflection system, a projection system or as so often with turn signals or parking lights as light bands.

History of LEDs in the car outdoor lighting

First, LEDs are used in the field of indoor lighting or as a control lamp, there were not yet sufficient for use as an all-round lighting color temperature and light output.

In 1992, LEDs stopped their way into the exterior vehicle lighting and were first used in the so-called third brake light.

Since the 2000s, LEDs are also increasingly in rear lights than normal tail light, and later as a brake light, parking light and turn signal before, mostly with reflection optics.

2000, the first combination rear lights came on the market in which the normal tail light, turn signal and brake light function is provided by LEDs ( Cadillac DeVille ).

2003 presented the company Hella at the IAA in Frankfurt am Main the first full-LED headlights that meets the lighting requirements of the legislature.

In 2004, the series used in the front. For the first time integrated the company Hella LED daytime running lights in the standard headlights of the Audi A8 W12. Furthermore, they are installed as a separately arranged module in the front area since 2004. Here, the Audi S6 and Porsche are to call 911 Turbo.

Followed in 2005 by a further milestone in the development towards full-LED headlights. Hella introduces the world's first LED headlamp which achieves the same performance as a low beam xenon previous models. The so -stocked Golf -V prototype already shows that the technical possibilities for future full-LED headlights are available. Furthermore, the LED technology was also used in the compact class with the tail lamp of VW Golf Plus. Here (partly SMD bi-color ) LEDs for lights, brake light and indicator are used. Also in the same year, the first full-LED rear light from Hella is made for the Cadillac DTS in series.

The end of 2006, Audi presented in collaboration with Automotive Lighting Reutlingen the new R8 sports car, the optional one full-LED headlamp is the first production vehicle in which all functions (indicators, position lights, daytime running lights, low beam and high beam) work with LED. At the same time Lexus LS 600H ago, in which the low beam is performed as standard in LED technology. The LS 600H was available from summer 2007. For the R8, the new LED technology was from the summer of 2008.

In 2007, the company Hella before their first full-LED headlamp for the Cadillac Escalade Platinum, which was introduced in the spring of 2009 on the U.S. market.

In 2009, Audi introduced the A8 before another vehicle with optional full-LED headlamps.

2010 Audi presented with the A7 his third vehicle with all-LED headlights. Almost simultaneously presented the new CLS Mercedes (Mercedes- Benz C 218 ) with full-LED headlamps and the Intelligent Light System as an option. So far only the xenon headlights features reserved for LED headlights are available.

Since 2011, a full-LED headlights including AFL function is optionally available for the Audi A6. In the new 6 Series Coupe / 7 Series LCI / X5 / 6 LCI BMW adaptive LED headlights are available as an alternative to the xenon headlamps. 2012 Rolls- Royce (BMW) the first manufacturer to equip a complete series comes standard with (full) LED headlamps.

Current state of development

A few years ago, most experts predicted a market introduction of LED lights not foresee before 2010. The first LED headlamp, however, came in 2007 to the European market. This was possible because the car manufacturers Audi and Lexus have worked with the EU by a dispensation - in contrast to the U.S., where LED technology is already allowed for low and high beam, lags in Europe, legislation is technically possible afterwards. It is only recently the LED functionality was introduced in the ECE Regulation R112 and adopted for AFS functions in the GRE. The LEDs Development has managed in recent years to increase the light output so that now even beam with LED can be realized. In addition, the light output now reaches that of xenon headlamps.

Positioning in the market

Because of the high price of LED headlights are now almost only offered in luxury cars. Full LED headlights are, for example, so far for the Audi R8, A8 D4, Audi S3, Mercedes -Benz CLS, Cadillac Escalade ( Platinum), BMW 6 Series Coupe and an LED low beam in the Toyota Prius III, Lexus RX 450h Lexus LS600h and offered. Despite the new opportunities in the field of LED technology - for example in the design - the Xenon technology remains state of the art This is mainly because that a conventional xenon headlamps consumes 40 watts on average. The time required for the high-power LEDs cooling and the thermal power loss associated can not keep up with this power requirement at the time. However, it is already working from manufacturers such as Osram on a solution which does not require active cooling more. Osram LED is used for the first time since March, 2011 by BMW as auxiliary lights with passive heatsink on a motorcycle in the BMW R 1200 GS ( K25 ), at the same time also in the BMW K 1600 GT. Since the 2013 model year, BMW also leads in the BMW R 1200 GS ( K50 ) for the first time a main headlamps with integrated daytime driving lights in LED technology in the option list. This fixture is actively cooled by a fan.

LED lights on railway vehicles

The locomotive 101 047 was fitted in December 2009 with LED signal lights and signal lights heating. At this experimental vehicle to be tested whether the conversion for all locomotives of this series is economical. The UIC headlights with LED technology is already known from other series, will be available in the 101 series with the latest warm white LEDs, which represent the current state of LED technology. Another new feature is an LED implementation for the Spotlight, the world's first place in the rail vehicle technology application. Thus, the warning lights remain visible even when the snow and ice, this locomotive was equipped with a temperature-controlled heating signal lights. The different lighting regulations in the EU make it necessary for transnational multi-system vehicles, as large a number to represent color and brightness in a limited space. On a board, many different colored LEDs can be accommodated and also dim. That is applied for example in the Siemens ES64F4.

Further equipped with LED headlights locomotives are the ÖBB 1144 and the new Mariazellerbahn " The Stairway to Heaven ".

LED headlights on bicycles

LEDs were on bicycle headlight first used in addition to the light bulb for the parking light. Since 2007, LED headlights are available for the bike lights. Made possible by the availability of white LEDs with 3 W of power. With them, the light output is higher than that good halogen headlights. The main manufacturer of LED bike lights for road traffic are Busch & Müller, CATEYE, Philips and SIGMA. Most high-quality LED headlamps use a free-form reflector to shape the light distribution.

There are also bicycle headlight with rotationally symmetrical optics; they are unfit for the road transport and are used mainly on mountain bike.

Parking lights and daytime running lights

Many LED headlights headlights - LED assumes the function of a status light. Returns the dynamo no energy, the LED for a few minutes fed by a double-layer capacitor which is charged during the journey; the parking light has a significantly reduced brightness. Some LED headlights have an additional LED daytime running lights for one that has a different brightness than the night driving lights.

Legal requirements

The legal requirements in Germany regulate the traffic regulations and the TA 23 So must be at least 10 lux since 2006, the light power in the core area of ​​illumination. The light distribution is defined in the TA 23. It aims to ensure a good illumination of the road, is blinded without oncoming traffic.

The electrical performance of approved lighting equipment must be at least 3 W, 2.4 W accounts for the front light.

Pros and Cons of LED headlamps

Benefits

• Long operating life (up to 50,000 hours, not a total failure )
• High energy efficiency
• High mechanical robustness
• Various possible light colors
• Advanced design possibilities.
• Instant one-click switching on and off
• No loss of life caused by frequent switching on and off, so for example for flashing stage lights interesting
• Among other things in motor vehicles, the reduced glare relative to other fixtures plays a role, since the light from a more distributed source. Thus, a selective high luminance is avoided, at the Xenon lights on motor vehicles often results in, for example glare for oncoming traffic. The light color of white LEDs is very similar to daylight, which causes a more nuanced illumination of the road when used in headlights.
• LED headlamps emit a very low UV and IR radiation.
• LEDs can be very effective work in partial load operation, thereby reaching in some cases even a higher efficiency than at full load. In contrast, the efficiency of incandescent lamps is reduced at low voltage very rapidly to very low values ​​. Gas discharge lamps can be dimmed only in a subregion.
• With colored LEDs can monochromatic light can be generated directly. In particular, blue light can be produced only very inefficient because blue color filters absorb a lot of light with incandescent lamps and color filters. Blue LEDs, however, produce light with relatively high efficiency ( Cree XR-E 7090 blue: about 34 lumens per watt ).
• LED headlights do not require protective glass in indoor applications.

Disadvantages

• LED headlights have higher initial cost compared to other lights. One reason for this is that they are constructed of technically challenging ( for example, they need an electronic constant current source). In addition, the high-power LEDs that are required in large numbers due to the low individual performances, still relatively expensive.
• The inevitable power losses in the form of heat is a problem with LEDs because the temperature inside the crystal of semiconductors such as, for example, LEDs such as 200 ° C must not exceed. Therefore, a heat sink and some active cooling is necessary especially in sunlit lights and high ambient temperature, which draws additional costs after itself.
• The efficiency and the lifetime of the LEDs drops with rising temperature semiconductor. Although temperatures of about 120-150 ° C are acceptable, the semiconductor temperature should therefore be kept as low as possible.
• Headlight lenses to fog on vehicles and outdoor use from within. For incandescent lamps, the moisture on the inside of the glass evaporates due to the high temperatures; with LEDs which is due to the lower temperature of the light source is not the case here different solutions are required.
• The luminous flux of LED headlamps is currently (February 2011 ) to approximately 11,000 lumens ( 140 watts ) is limited, increased power (up to 15 kilowatts) previously reserved for incandescent, sulfur and gas discharge lamps.
• LED headlamps have the same luminous flux in a larger device than incandescent or gas discharge lamps in order to accommodate the necessary electronics required and passive cooling can.

• LED tail lights, which are often pulsed with only about 50 Hertz, irritate people who because of relatively " faster signal processing in the field of vision ," meaning " sehphysiologisch conditionally, moving pulsed light sources as several adjoining single lights perceive - so-called bead - effect ( Perlschnureffekt ); This effect applies to road transport [ for these people ] very disturbing. This perception happens involuntarily ", they can " neither used to it nor work off it. For those affected, it is a minority, " which is estimated at only about 5 % of the German road users. However, can be solved by increasing the pulse rate with a low cost of this problem.
• In case of failure of an LED, the entire headlight has to be replaced depending on the construction method, since the replacement of individual LEDs by the legislature is not provided or can be made only with difficulty with workshop tools.