An Engineer in Wonderland – LCDs get ‘greener’

I have been agonising over buying a new computer monitor for ages.

fujitsu-screen.jpgI have been agonising over buying a new computer monitor for ages.

There is a bewildering array available and the questions that need answering include:

  • 22″ 1280×1024 or 24″ 1680×1050?
  • Twisted nematic, in-plane switched, or some other technology?
  • A brand or a cheapie?
  • HD-ready just in case I ever watch DVDs?

So many questions, and so little decisiveness.

But I may have a way to cut the choice down – Alice’s Razor is to be energy consumption. 

LCD monitors are already significantly less wasteful of power than CRT types and 22″ types are supposed to waste disproportionately less than those 2″ bigger.

The list gets shortened to one if the LG Electronics W2252TE 22″ monitor reaches the shelves at a reasonable price.

It is claimed to use only half the operating power compared with others of the same size, and reviews seem to agree – getting its power somewhere between 18 and 22W compared with 40W plus for competitors.

This is quite an achievement as the only obvious specification limitation is a reduction in maximum brightness from 300 to 250cd/m2.

I have no idea how it is done, but there is some clever engineering somewhere.
As most power is eaten by the backlight, I am thinking that some better way to get light from CCFL tube to the screen has been employed.

Reports do not talk of washed out colours, which suggests its RGB filters have not been compromised.

If someone knows how it is done, do tell.

Standby power, according to this report is a creditable 300mW.

So the question is now: Get one of these, or stick with my old 17″ LCD?

Much easier.

Thinking about the last point – stand-by power – reminded me of an article in Electronics Weekly about a zero stand-by power monitor.

By coincidence, a range based on the Fujitsu Siemens technology covered has just hit the shelves.

There are quite a few ways to cut stand-by power to a few mW.

Some fine examples were submitted to Electronics Weekly’s own February 2007 ZigBee power supply competition – where the winner and runner up consumed 1mW and 2mW stand-by respectively.

At this point, purveyors of 7W-stand-by set-top boxes and their like should view this and hang their heads with shame.

Fujitsu’s undisclosed ‘switching element’ in the power supply is controlled by the PC connection and apparently cuts monitor consumption to zero when the PC is shut down.

I am thinking a photo-triac, or back to back mosfets controlled by an opto-isolator – there are many ways of doing it.

Two monitors have appeared: the 20″ P20W-5 ECO and 22″ P22W-5 ECO; with 24 and 26″ models following in September.

Unless the Fujitsu monitor also has low operating dissipation, it will not make my shortlist as within the walls of Chateau Alice everything gets turned off at the mains when it is not needed.

And prices start at €419 for the smallest one, which is a bit steep unless the display is not a simple twisted nematic type.

The good thing is, huge power savings are available for those motivated enough to look for them, and skilled enough to find them.


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  1. The W2252TE is stubbornly failing to hit the shelves, so I called LG’s representative.
    Despite being told someone would phone back, LG has offered no explanation why its energy-efficient 22in has been delayed.
    So don’t hold your breath.
    How disappointing.

  2. It’s possible that the TFT in the LG monitor is partly transflective. We use transflective TFTs (an after-market conversion in most cases) where our passenger transport information screens need to be legible in bright daylight conditions. I’ve never taken one apart, but I understand that some unidirectionally reflective film is used between the CCFL and the back of the TFT, so any light that makes its way through the glass from the front gets turned around and is used to supplement the backlight.
    It’s just a theory, maybe someone from LG will respond with an explanation from the horse’s mouth. Or maybe it’s a secret.

  3. By coincidence – NEC has also just announced a ‘green’ monitor.
    One version of the EA261WM scores gold on the Electronic Product Environmental Assessment Tool (
    “The 26” model’s EPEAT certification and carbon footprint meter offer greater transparency with respect to the use of environmentally-friendly materials, energy efficiency and CO2 emissions,” claims NEC.
    I have no way of judging how thorough EPEAT certification is,
    Somehow it lets NEC get away with a completely rubbish stand-by power consumption: 2W
    But I quite like the fact the monitor has a built-in carbon footprint meter.
    Operational consumption is high compared with the 22″ models:
    82W, or 70W in brightness-limited ‘EcoMode’.
    It is the black model that meets the gold standard, for some reason the white version only gets a silver assessment.

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