To know about LED lighting


LED - a new lighting dimension

LED (electroluminescent diode) is small in size, but represents conclusive technological advantages which have changed the lighting world and has become a real alternative to conventional light sources for many lighting applications.


LED - operating principles


The principle of electroluminescent diodes is based on the technology of semiconductor components directly transforming the electric current into light. Different from an incandescent lamp, the light is not provided by a lamp filament, but by a solid-state crystal in the form of a flat chip. The crystal consists 2 areas of opposed polarity, an “n” area with an excess of electrons and a “p” area with a deficiency of electrons. A recombination process equalizes electron excess and electron deficiency at the pn junction.

The energy released during this process is emitted in the form of radiation (visible light). This light is monochrome, which means it consists of only one wavelength and is therefore of only one color. Depending on the materials used for the semiconductor crystal, a LED can be red, orange, yellow, green or blue. The color white is obtained either by mixing colors (three LEDs: red, green and blue), or by a luminescence conversion. In this case a blue light, emitted by a diode, excites luminescence dyes, which thus emit a yellow light. The superposition of these luminous emissions provides a white light. The leadframe on which the semiconductor crystals are mounted provides electrical contacting and discharges the heat produced. The plastic lens protects the chip from environmental influences and, at the same time, serves as an optical lens defining the aperture angle of the light beam.


LED - characteristics and advantages

LED efficiency has definitely increased over the last few years. Today, white LEDs are produced with an efficiency of 20 lm per Watt (lm/W) and red LEDs reach 50 lm/W. Their luminous efficiency is therefore comparable to that of halogen lamps.
This economic aspect of LED is also very positively influenced by their long service life which can reach 80,000 hours. The LED service life is defined by the failure rate and the luminous flux reduction compared to the initial values. When LEDs are operated under temperature and intensity conditions indicated by the manufacturer, there is virtually no possibility of a total failure. The continuous luminous flux reduction (degradation), depending on the temperature load on the light-producing layer, is the crucial point influencing the service life. According to the definition provided by the semiconductor industry, the average service life of a LED is reached when the luminous flux reaches half of the initial value. The light manufacturer can influence in a crucial way the service life of a diode thanks to a luminaire design encouraging heat evacuation. The user can also influence the service life by carefully respecting the luminaire’s operating instructions.
LEDs may be used at low voltage (SELV) and reduced intensities. Thanks to the color diversity, their reduced size, and therefore the resultant flexibility of the modules, LEDs open many new perspectives in numerous different fields of application. Other important advantages: the almost unlimited switchability with an immediate 100% light output, the high shock-resistance, a light without IR or UV, and a silent operation with low heat development.


Further information to the following topics


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What you should know about LED lighting


LED - a new lighting dimension

LED (electroluminescent diode) is small in size, but represents conclusive technological advantages which have changed the lighting world and has become a real alternative to conventional light sources for many lighting applications.


LED - operating principles


The principle of electroluminescent diodes is based on the technology of semiconductor components directly transforming the electric current into light. Different from an incandescent lamp, the light is not provided by a lamp filament, but by a solid-state crystal in the form of a flat chip. The crystal consists 2 areas of opposed polarity, an “n” area with an excess of electrons and a “p” area with a deficiency of electrons. A recombination process equalizes electron excess and electron deficiency at the pn junction.

The energy released during this process is emitted in the form of radiation (visible light). This light is monochrome, which means it consists of only one wavelength and is therefore of only one color. Depending on the materials used for the semiconductor crystal, a LED can be red, orange, yellow, green or blue. The color white is obtained either by mixing colors (three LEDs: red, green and blue), or by a luminescence conversion. In this case a blue light, emitted by a diode, excites luminescence dyes, which thus emit a yellow light. The superposition of these luminous emissions provides a white light. The leadframe on which the semiconductor crystals are mounted provides electrical contacting and discharges the heat produced. The plastic lens protects the chip from environmental influences and, at the same time, serves as an optical lens defining the aperture angle of the light beam.


LED - characteristics and advantages

LED efficiency has definitely increased over the last few years. Today, white LEDs are produced with an efficiency of 20 lm per Watt (lm/W) and red LEDs reach 50 lm/W. Their luminous efficiency is therefore comparable to that of halogen lamps.
This economic aspect of LED is also very positively influenced by their long service life which can reach 80,000 hours. The LED service life is defined by the failure rate and the luminous flux reduction compared to the initial values. When LEDs are operated under temperature and intensity conditions indicated by the manufacturer, there is virtually no possibility of a total failure. The continuous luminous flux reduction (degradation), depending on the temperature load on the light-producing layer, is the crucial point influencing the service life. According to the definition provided by the semiconductor industry, the average service life of a LED is reached when the luminous flux reaches half of the initial value. The light manufacturer can influence in a crucial way the service life of a diode thanks to a luminaire design encouraging heat evacuation. The user can also influence the service life by carefully respecting the luminaire’s operating instructions.
LEDs may be used at low voltage (SELV) and reduced intensities. Thanks to the color diversity, their reduced size, and therefore the resultant flexibility of the modules, LEDs open many new perspectives in numerous different fields of application. Other important advantages: the almost unlimited switchability with an immediate 100% light output, the high shock-resistance, a light without IR or UV, and a silent operation with low heat development.


Further information to the following topics
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