Why is a smartphone like a hummingbird? Neither can go more than a few hours without refueling, or bad things happen. (If you answered that smartphone owners are often forced to flutter around looking for a power outlet, I’ll accept that, too.)
Do you know where the power goes? As the graphic shows, around half your battery is spent on the display alone. And of that, the vast majority is used simply to power the backlight that all LCDs need. (The situation for AMOLED displays is similar, but for different reasons. That’s a subject for a future blog.)
Clearly, improving the power efficiency of the display is a powerful way to improve battery life. Turning the brightness down isn’t a helpful strategy. Indeed, we expect displays to be brighter and richer all the time, but not at the expense of already limited battery life. (Bigger batteries would also work, but the market has spoken on that one. Slim is in!)
How is this to be accomplished? Find out after the jump.
[Updated February 13, 3013 because metal oxide backplane technology has improved since the original post was published. See question 7.]
There has been a huge amount of interest and discussion around new LCDbackplane technologies, particularly about metal oxide. Following on from my first post on the subject last week, I thought it might be useful to answers some of the questions I’ve been hearing most often.
1. Amorphous Silicon (a-Si) has been the dominant transistor backplane technology for displays the last 20 years. Why are new technologies necessary?
Changes are being driven primarily by the demand for higher resolution and faster refresh rates. The most important transistor parameter is electron mobility. Electron mobility of a-Si is very low (around 1cm2/Vs) and is at the edge of the physical ability to support high refresh rates such as 240Hz for high definition television. (Just in case you need a reminder, as this graphic shows, each transistor is basically an on/off switch that controls each red/green/blue subpixel and 240Hz refers to 240 switches per second.)
The display industry is in the middle of one of the most significant technical transitions of the last 20 years and it is also mostly invisible to the average consumer. It has all to do with the advances taking place in transistors – the electronic switches that control the display’s picture, providing clarity and crisp imagery.
Every pixel on your LCD screen is turned on or off by a transistor. The complete array of pixel transistors is known as a backplane, as you can see in the graphic. Clearly, the performance of the backplane directly affects the quality of the display for your TV, smartphones and tablet PCs. How fast the switch can be turned on and off refers to the refresh rate and the total number of pixels on the screen equals picture resolution.
Today, there are three backplane technologies, which we call amorphoussilicon (a-si), low temperature poly-silicon (LTPS) and metal oxide (MO). If you are buying a TV, should you care what transistor technology is in it?