advanced leds ltd - The Future of Lighting

| How Do They Work? |

A light emitting diode (LED) is essentially a PN junction semiconductor diode which emits a monochromatic light when operated in a forward bias direction. A LED package comprises the light emitting semiconductor material, a lead frame to keep it in place, and an encapsulation epoxy resin. The encapsulation material is either clear or coloured, depending on the desired effect.

The basic operating process is therefore electronic rather than electro-chemical. LEDs themselves operate at low voltage, typically 3 - 6 volts DC.

Utilised in indicator applications, 5mm LEDs are in common use. Further development has led to the high flux LED, with improved output, efficiency and reliability (right).

LED Life

The expected life of LEDs depends on whether we need to consider mortality alone or allow for depreciation. Where a particular lighting level must be achieved, we must consider lumen depreciation as we would do with conventional light sources:

Mortality 2.5% @ 100,000 hours Depreciation 30% @ 50,000 hours

When calculating designed illuminance using LEDs, depreciation must be taken into account when selecting the maintenance factor to be used, and the expected life modified accordingly.

Please contact our technical department for further details.