How it works?
TV manufacturers can use an LED backlight instead of the standard Cold Cathode Fluorescent Lamps
(LCD-CCFL) used in most LCD televisions. It is important to distinguish this method of backlighting,
a conventional LCD panel, from a true LED display, or an OLED display. Televisions described as
'LED TVs' are vastly different from the self-illuminating OLED, OEL or AMOLED display
technologies. In terms of the use of the term 'LED TV' in the UK, the ASA(Advertising Standards
Authority) has made it clear in prior correspondence that it does not object to the use of the term, but
does require it to be clarified in any advertising. There are several methods of backlighting an LCD
panel using LEDs including the use of either White or RGB (Red, Green and Blue) LED arrays
positioned behind the panel; and Edge-LED lighting, which uses white LEDs arranged around the
inside frame of the TV along with a special light diffusion panel designed to spread the light evenly
behind the LCD panel.
An LED backlight offers several general benefits over regular CCFL backlight TVs, typically including
lower power consumption and higher brightness. Compared to regular CCFL backlighting, there may
also be benefits to color gamut. However advancements in CCFL technology mean wide color gamuts
and low power consumption are also possible. The principal barrier to wide use of LED backlighting
on LCD televisions is cost.
The variations of LED backlighting do offer different benefits. The first commercial LED backlit LCD
TV was the Sony Qualia 005 (introduced in 2004). This featured RGB LED arrays to offer a color
gamut around twice that of a conventional CCFL LCD television (the combined light output from red,
green and blue LEDs produces a more pure white light than is possible with a single white light). RGB
LED technology continues to be used on selected Sony BRAVIA LCD models, with the addition of
'local dimming' which enables excellent on-screen contrast through selectively turning off the LEDs
behind dark parts of a picture frame.
Edge LED lighting was also first introduced by Sony (September 2008) on the 40 inch BRAVIA KLV-
40ZX1M (refered to as the ZX1 in Europe). The principal benefit of Edge-LED lighting for LCD
televisions is the ability to build thinner housings (the BRAVIA KLV-40ZX1M is as thin as 9.9mm).
Samsung have also introduced a range of Edge-LED lit LCD televisions with extremely thin housings.
Because LEDs are able to be switched on and off more quickly than CCFL displays and can offer a
higher light output, it is theoretically possible to offer very high contrast ratios. They can produce deep
blacks (LEDs off) and a high brightness (LEDs on), however care should be taken with measurements
made from pure black and pure white outputs, as technologies like Edge-LED lighting do not allow
these outputs to be reproduced simultaneously on-screen.