Light sources

AN2042

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Light sources

Incandescent lights are basically electric space heaters that give off light as a by-product.

They are very inefficient, wasting most of the power they consume as heat.

An innovative light source is represented by LED technology, with very low power

consumption and virtually no heating effect, making LEDs ideal for several domestic and

commercial applications.

The long lifetime characteristic of LEDs means savings on maintenance costs. Unlike

traditional light sources, LEDs are not subject to sudden failure or burnout. Since LED based

light sources last at least 10 times longer than a normal light source (up to 10 years or

100.000 hours for the higher quality products), it is possible to reduce or eliminate the

maintenance ongoing costs.

This can be useful in many critical applications where the location makes replacement

difficult (radio tower, aircraft warning lights, bridge and tunnel lights…) or in applications

where a failure of the light source is not acceptable (emergency exit lights, back up lighting,

security lighting…).

LED lighting technology features many advantages compared to conventional lighting:

●

Higher energy efficiency, in terms of lumens per watt;

●

Direct light beam for increasing system performance;

●

Dynamic color control technology;

●

Full dimmable without color variation;

●

No mercury and no UV or heat in light beam;

●

Low voltage operation, suitable for safety purpose in SELV systems.

The most important limitation for using high brightness LEDs is the manufacturing cost,

which is still relatively high.

In Table 1 a comparison between traditional light sources and a typical commercial LED is

shown.

Table 1.

Performance of typical light sources compared with white Luxeon LEDs

Lighting source

Luminous efficiency

(lm/W)

Lifetime (hours)

Theoretical optical

power (min and max)

Incandescent bulbs

18 ÷ 25

1000 – 2000

15 – 1000 W

Halogen lamps

15 – 25

2000 – 5000

5 – 2000 W

Fluorescent lamps

60 – 110

14000 – 20000

4 – 60 W

Mercury lamps

15 – 60

12000 – 24000

50 – 1000 W

LEDs (white luxeon)

25

100000

0.7 – 5 W