04 Mar 2015

LCD Display Backlight Options

LCD Displays

LCDs require a light source, either ambient light or direct light, in order to show the information on the display. Using an internal light source like a backlight with your LCD increases the readability of your display. It also illuminates the information on the display in low-light conditions. Popular backlight options for monochrome displays include LEDs, fiber optics, ELs, and CCFLs.

LED Backlight

LED backlighting is the most commonly used backlight for small, LCD panels. Light-emitting diodes, or LEDs, are practical components for a light source because of their small size. LED backlighting is popular due to its overall low cost, long life, variety of colors and high brightness.

LED backlights are housed in a light box that has a diffuser to evenly distribute the LED light. The light box is then mounted behind the LCD’s viewing area. The LED backlight comes in two configurations: array and edge lit. The array configuration has the LEDs mounted in a uniform, grid layout within the light box. This configuration gives off a very bright, even light. The disadvantage of an array configuration is that it requires a thick light box design to accommodate the number of LEDs required. The high number of LEDs in this configuration also means it consumes more power.

The other configuration for LED backlights is edge lit. An edge lit configuration is the most commonly used construction for LED backlights. This configuration mounts the LEDs along one edge of the light box. The layout results in a thin design. Edge lit also uses less LEDs overall and therefore consumes less power than an array configuration.

Fiber Optic Backlight

Another type of backlight options is the use of fiber optic technology. Fiber optic backlights use sheets of fiber optic woven cloth and are bundled by a ferrule (metal cap) to an LED or halogen light source. Advantages for the fiber optic technology includes low voltage, low power, and a very uniform brightness. This type of backlighting is ideal for custom display shapes or sizes however it is priced at a higher cost compared to other technologies available.

EL Backlight

A third type of backlight option available uses an electroluminescent (EL) panel. The EL backlight is constructed of a series of different material layers that work together to create the light. The EL panel generates light when an electric current (AC power) is applied to its conductive surfaces. The advantage with EL backlighting is its low power consumption, no heat emission, and overall thin composition. EL backlighting is limiting in that it requires an invertor to generate the VAC needed to emit the light.

CCFL Backlight

The last common backlight option available are cold cathode fluorescent lamps (CCFLs). CCFL backlights are a cost effective option typically found in graphic displays. The CCFL backlight for LCDs is usually configured with the lamp on the edge of a diffuser to distribute the light. An inverter is required to supply the voltage required by the fluorescent lamp. CCFLs offer a bright white light with low power consumption. This backlight option is not ideal for cold-temperature applications (less than 15°C) as the light output decreases with decreased ambient temperature.

There are many different backlight options available for your LCD. The most common types are LED, fiber optic, EL, and CCFL backlights. Cost and application of your product will have the highest influences on which backlight technology is best for your LCD.