How To Choose A Backlight

  The backlight is mainly composed of light source, light guide, optical module and structural parts.

1、Light source selection

Electroluminescent (EL) backlight is thin and light, providing uniform light. Its power consumption is very low, the required working voltage is 80-100Vac, to provide the working voltage of the inverter can be 5/12/24Vdc input conversion for the AC output. However, EL backlighting has a limited lifetime (average lifetime at 50% brightness is 3000 to 5000 hours, at higher brightness levels the lifetime will be much shorter), so an ideal inverter for EL backlighting allows the output voltage and frequency to increase as the EL bulb ages, thus extending the effective lifetime of displays with EL backlighting sources.

EL backside illumination is suitable for small reflective LCD applications such as watches, digital desktop clocks and monochrome PDAs that require very weak illumination for use in hazy or dimly lit conditions. However, the low efficiency, low brightness and short lifetime make them unsuitable for transmissive backside lighting applications such as large LCDs required for laptops and flat-panel desktop monitors.

Smaller cold cathode fluorescent lamps (CCFLs) provide the brightness and lifetime (and light control capability) required for large LCDs, but with the proliferation of more efficient and flexible LED designs, CCFLs are being used less and less. However, heat build-up is a concern.

LED backlight has a service life of over 5000 hours and uses DC voltage. LED backlight and CCFL backlight are basically the same in structure, where the main difference is that CCFL is a line light source, while LED is first made into an LED light bar (LED light-bar) when in use, and then put into the backlight.

2、Light guide plate selection

The role of the light guide plate is to guide the direction of light scattering, used to improve the brightness of the panel, and to ensure the uniformity of the panel brightness. The light guide has a great impact on the backlight panel, therefore, the design and production of the light guide in the side light backlight panel is one of the key technologies. The CCFL or LED light-bar is located on the side of the light-guide, and the light emitted from it is directed into the interior of the light-guide using reflection. When the light reaches the diffusion point, the reflected light spreads out at various angles and then breaks the reflection condition and is emitted from the front of the light guide. By using a variety of diffusion points of varying density and size, the light guide can be made to emit light evenly. The purpose of the reflector is to reflect the light from the bottom surface back into the light guide to improve the efficiency of the use of light.