October 02, 2020

LED Backlit Flat Panel Displays

LED stands for Light Emitting Diode, LCD stands for Liquid Crystal Display.  The two are used together in a form that utilises the LED's to generate the backlight for the LCD, replacing the traditional approach that uses CCFL (Cold Cathode Flourescent Lamps) as the image light source.


The LED backlights consume less power and generate less heat compared with traditional CCFL backlit displays.  The light o/p from the LED's is able to be more tightly controlled so that the screen bcightness can be adjusted up or down depending on the application.  PWM (Pulse Wiith Modulation) is used to turn the LED's on and off quicker than can be observed by the human eye, effectively reduring the light o/p and therefore power consumption.  These displays are said to consume up to 40% less power than a CCFL backlit display.  Also because the LED's are distributed across the panel the light spread is even - no hotspots (areas of light and dark).

The picture quality is better as the color gamut is wider than a boadcast television signnal, and the blur effects that plagued early LCD technology are improved further again.

The weight of these units is also substantially less.  They operate from low voltages (5-12V), so do not require an inverter or transformer to generate the AC voltages needed for CCFL backlights.  This will also result in lower cost, once the manufacturing community are producing these units in large quantities.

The life of the panel is also extended.  LED's have a life expectancy in the order of 50,000 to 100,000 hours - that is somewhere between 6 and 12 years of continuous use, with no noticable picture quality degradation over that period.  CCFL backlit displays can lose up to 50% of their light output over their life.  Picture quality stability is particularly important in applications where consistent color temperature is a requirement - like Graphic creation.

The units do not need need to warm up, so will operate at best from switch on.

In a portable application such as a laptop they have the additional advantage of being thinner, whilst also having Immunity to vibration.

The obvious "Green" advantages will be a big factor in encouraging the transition to this type of display.  Reduced power consumption and longer life are the main ones.  But conventional CCFL backlights contain some mercury and therefore create a disposal issue.  LEDS do not. have this problem.

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