Power saving in LED-Backlight, LCD Televisions

[eem2am]

Hello,

I have heard that the latest method of saving power in LED-Back-lit, LCD Televisions is to dim the LEDs behind certain parts of the screen image that are dark.

Do you know if this is true?

-The thing is, Television pictures are moving constantly, and from frame to frame, different parts of the screen are constantly varying in light level depending on the particular movie scenes playing.

So how on earth are they going to manage to dynamically and differentially dim the particular LEDs over each square inch of the screen throughout the course of a typical movie?

This would require hundreds of switch-mode Dimmable LED Drivers.
-It is completely impratical.(?)
-There would be losses associated with each of the hundreds of Dimming LED Drivers that would make the efficiency relatively poor.

So is this idea of dynamically and differentially dimming various LED banks in a TV Backlight just a rumour?

 

[betwixt]

No it's absolutely true and has been used for several years to achieve "dynamic contrast" where the backlight is lowered to reduce light breakthrough on dark scenes.
It only requires ONE led or CFL driver though. In an LCD dislplay the pixels are turned on to allow the backlight through to the viewer so switching pixels is all thats needed to select any particular part of the screen, this is what is done in normal scanning. The whole backlight is dimmed or lightened at once and the level is set by the average picture content.

Brian.