DOWIN Opto－Electronic Co.,Ltd

  Incandescent lamps ( light bulbs ) create light by running electricity through a thin filament, thereby heating the filament to a
very high temperature so that it glows and produces visible light.A broad range of visible frequencies are naturally produced,
yielding a pleasing warm yellow or white color quality. The incandescing process, however, is highly inefficient, as over 98%
of its energy input is emitted as heat.A standard 100 watt 120 VAC light bulb produces about 1700 lumens,about 17 lumens
per watt . Incandescent  lamps  are  relatively  inexpensive to produce . The typical lifespan of a mains incandescent lamp is
about 1,000 hours.  They  work  well  with  dimmers. Most existing light fixtures are designed for the size and shape of these
traditional bulbs.
  Fluorescent lamps (light bulbs) work by passing electricity through mercury vapor, which  in  turn  produces  ultraviolet light.
The ultraviolet  light  is  then absorbed by a phosphor coating inside the lamp, causing it to glow,or fluoresce.While the heat
generated by fluorescent lamp is much less than  incandescent counterpart , energy is still lost in generating the ultraviolet
light and converting this light into visible light.If the lamp breaks exposure to mercury can occur. Linear fluorescent lamp are
typically five to six times the cost of incandescent lamps,but have life span around 10,000 and 20,000 hours.Lifetime varies
from 1,200 hours to 20,000 hours for compact fluorescent lamps.
  The efficacy of fluorescent tubes with modern electronic ballast commonly averages 50  to 67  lm/W overall. Most compact
fluorescents 13 watts or more with integral electronic ballasts achieve about 60 lumens/watt.They should be recycled rather
than disposed to prevent mercury release. Some flicker at 100 or 120Hz,and the quality of the light tends to be a harsh white
because of the lack of a broad band of frequencies. Most are not compatible with dimmers.
  SSL/LEDs LEDs come in multiple colors, which are produced without the need for filters. A white SSL can be comprised of
a single high-power LED , multiple  white  LEDs , or from LEDs of different colors mixed to produce  white light . Advantages
include:
  High efficiency - LEDs are now available that reliably offer over 100 lumens from a one-watt device  or much higher outputs
at higher drive currents
  Small size - provides design flexibility, arranged in rows, rings, clusters, or individual points
  High durability - no filament or tube to break
  Life span - in properly engineered lamps, LEDs can last 50,000 - 60,000 hours
  Full dimmability – unlike fluorescent lamps , LEDs can be dimmed using pulse-width modulation (PWM - turning the light
on and off very quickly at varying intervals). This also allows full color mixing in lamps with LEDs of different colors.[1]
  Mercury-free - unlike fluorescent and most HID technologies, LEDs contain no hazardous mercury or halogen gases
  However,some current models are not compatible with standard dimmers. It is not currently practical to produce high level
of room lighting . As a result , current LED screw-in light bulbs offer either low levels of light at a moderate cost,or moderate
levels of light at a high cost.In contrast to other lighting technologies, LED light tends to be directional . This is disadvantage
for most general lighting applications, but can be an advantage for spot or flood lighting.
  Because individual LEDs are low-voltage DC devices,implementing SSL to operate from mains AC requires well designed
circuitry and a thermal case to dissipate the heat.