Ultra-low-Power Technology Round-Up

Government mandates and industry trends are more or less in step with each other when it comes to making more-energy-efficient TVs. This move toward low-power displays is being realized through a variety of technologies, including refinements in the backlighting and edge-lighting of LCDs.

by Steve Sechrist

SOME MAY CONSIDER 2009 the beginning of the energy-conservation era in consumer electronics. That certainly holds for the nation's most populous state, California, and the adoption of its new energy regulations in mid-November 2009 by the California Energy Commission (CEC). The group moved to adopt, at the state level, new energy specifications for TVs and other consumer-electronic devices and gave the new standard teeth by restricting sales of non-compliant products in one of the largest markets in the U.S. Here's how the official proceeding (Docket#09AAER-1C) stated it:

"In California, TVs (along with DVRs, DVD players, and cable/satellite boxes) now consume about 10% of a home's electricity. Increasing sales of flat-screen TVs, larger screen sizes, the growing number of TVs per household, and increased daily use of TVs all contribute to greater electricity consumption.

"The proposed standards have no effect on existing TVs. … they would only apply to TVs sold in California after January 1, 2011. The first standard (Tier 1) would take effect January 1, 2011 and reduce energy consumption by an average of 33%. The second measure (Tier 2) would take effect in 2013 and, in conjunction with Tier 1, reduce energy consumption by an average of 49%."

"Foul," cried electronics organizations, including Californians for Smart Energy (CSE) in-state, as well as bigger guns like the Consumer Electronics Association, producer of the popular CES show in Las Vegas. These groups did not mince words: "Shock and dismay" were used by the CSE, which claimed the results would be catastrophic, significantly contributing to unemployment in the state, etc.

But are consumer-electronics makers really so far off from the California compliance numbers – and, more importantly, is the trend toward creating ultra-low-power displays simply on track for the 2011 adoption date anyway?

Off the bat, the CEC's position is this: "The technology to make TVs more energy efficient is available now and currently used in a variety of models. As of late-September 2009, more than 1000 TVs already meet the 2011 standards." Chiming in from the editorial side of the industry, CNET Reviews' senior editor David Katzmaier calls the new Californis standards "fairly lenient." He said, "The TVs most in danger of not meeting the California mandates or getting an Energy Star label are the very large PDP TVs, particularly those that are more than 54 in."

In any event, the main culprit behind energy-hogging TVs is not so much the technology they are based on as the ballooning sizes of TVs in general. "TVs consume more power because they are bigger," Katzmaier said. "The California Energy Commission estimates that per square inch, LCDs consume a bit more than CRTs, but most people are also upgrading in size, which means significantly more electricity use." That usage number is growing now to match that of a refrigerator in some cases.

To help get a handle on display size and power consumption of the entire system, we turn to a CNET interactive HDTV Power Consumption chart (Fig. 1) that can be sorted by TV attributes, including power consumed in watts and a host of other factors.

As the CEC suggests, smaller sets (32 in.) deliver the best power numbers, but with some surprises. For instance, nestled among the low-power LCD-TV sets in the 32-in. size, which range between 59.75 and 70.16 W, is a Sharp 46-in. LCD TV (model 46LE700UN) drawing 63.91 W of power (or a slim 0.071 W/sq. in.).

That set beat out a host of 32-in. sizes from the likes of Sony (KDL-32M4000), Panasonic (LCD TC-L32X1 and -LX85), Samsung (LN32A 450), and LG (32LG40) and delivered the best per-square-inch consumption of any LCD TV on the list. Here's how CNET describes the Sharp 46-in. set in its review, "Among HDTVs of its size, the Sharp out-misers the former champ, Samsung's UN46B6000, by 26%, using barely more power after calibration (about 64 W) than a standard light bulb."

 

Fig. 1: An HDTV power-consumption chart compares watts per square inch and other factors for a variety of manufacturers' products in display sizes ranging from 23 to 46 in. Source: CNET.com.

Model
HDTV type
Screen size
Default setting(watts)
Default setting (watts persquare inch)
Default setting (cost per year)
Calibrated setting (watts) (down arrow)
Calibrated setting (watts per squareinch)
Calibrated setting (cost per year)
Sharp LC- 32D44U
LCD
32
126.25
0.289
$27.91
59.75
0.137
$13.58
Vizio VO32L
LCD
32
104.90
0.240
$22.60
61.14
0.140
$13.17
Toshiba 32CV510U
LCD
32
131.34
0.300
$28.92
61.20
0.140
$13.81
LG 32LG30
LCD
32
117.88
0.269
$26.17
61.70
0.141
$14.06
Sharp LC- 46LE700UN
LCD
46
101.58
0.112
$21.94
63.91
0.071
$13.83
Panasonic TC-32LX85
LCD
32
97.79
0.223
$21.99
64.96
0.148
$14.92
LG 32LG40
LCD
32
116.19
0.266
$25.03
67.86
0.155
$14.62
Samsung LN32A450
LCD
32
130.65
0.299
$28.99
68.27
0.156
$15.56
Vizio VO32LF
LCD
32
121.58
0.278
$26.19
69.00
0.158
$14.86
Panasonic TC-L32X1
LCD
32
92.10
0.210
$20.34
70.16
0.160
$15.61
Vizio VOJ370F
LCD
37
145.84
0.249
$31.42
76.64
0.131
$16.51
Sony KDL- 32M4000
LCD
32
112.94
0.258
$25.09
78.09
0.178
$17.58

 

Sharp describes its LED-based LCD TV as a "full-array LED-backlight system," meaning the light-emitting diodes are not arranged in edge-lit formation similar to those of rival Samsung. But the Sharp sets are considerably thicker than the Samsung sets.

The Insight Media Green Display Report (GDR) characterizes edge-lit LED technology in LCDs this way: "In the edge-lit backlight design, separately controlled LEDs illuminate the panel from the top and bottom edges to create 16 zones that can be independently addressed, yielding a 2-D dimming approach. This edge-lit 2-D local-area-dimming LED backlight can reduce power consumption on a 55-in. TV by 35–64% [compared to a cold-cathode fluorescent lamp (CCFL) backlight unit (BLU)], depending upon the type of content. AU Optronics Corp. (AUO) also recently announced a 32-zone edge-lit local-dimming LCD TV."

LG Electronics showed just such a system, with eight zones on the top row and eight zones on the bottom row, using these 16 blocks to achieve the power reduction mentioned above. One other approach, reported by Insight Media publisher and analyst Chris Chinnock, is similar to the 2-D local-dimming strategy that dims color LEDs (R-G-B) individually. This method boosts contrast and expands color – "But do not look to this approach for dramatic power savings," Chinook says.

At the Insight Media Green Display Expo in Washington, D.C., in October of 2009, conference organizer Chinnock reported on a presentation by Bruce Berkoff, chairman of the LCD TV Association: "Berkoff described some of the trends in LCD technology that are helping to reinforce the trend toward lower power consumption. He cited LED backlights as a key driver, as well as local-area dimming and the use of RGBW color-filter architectures.

"Berkoff expanded this discussion of local dimming to describe a concept edge-lit 1-D system that illuminates the panel from top and bottom to create 16 zones that can be independently addressed (really a 2-D dimming approach). This can reduce power consumption of a 55-in. TV by 35–64% (compared with a CCFL BLU), depending upon the type of content. Interestingly, AUO announced a 32-zone edge-lit local-dimming LCD TV at Flat Panel Display International during the same week. Another variation on the 2-D local-dimming approach is to dim the red, green, and blue LEDs individually. Compared with using a white LED, the RGB LEDs improve contrast, expand the color gamut, but do not provide as much power savings."

Light-Guide Technologies

There are, however, new light-guide technologies that allow for direct LED backlighting and thin design. Insight Media covered this approach recently in its Large-Display Report (July 9, page 26.) in which analyst Ken Werner noted a "distinguished paper" (No. 48.1) delivered at the 2009 SID Symposium, where James Gourlay of Design LED Products (Livingston, UK; product shown in Fig. 2) and Ian Miller of ITI Techmedia (Glasgow, Scotland) described such a structure in detail.

According to Werner, "The thin device structure, which incorporates side-emitting LEDs distributed in a two-dimensional array across the BLU, is embedded in a multi-layered printed and integrated light guide. Containing 0.6-mm-high LEDs, the substrate/light-guide structure is 1.5 mm thick. A prototype 40-in. design produced a BLU thickness of 15 mm, and the authors believe less than 10 mm is possible. The light-guide structure incorporates micro-structure surface extraction, which provides a controlled beam angle for the extracted light."

Readers may find it interesting to do an Internet search on "Sharp LED light Guide" to see the patent activity around this subject. Clearly, there is something big brewing in this area.

Samsung Popularizes "LED TV"

Are power savings alone enough to get consumers excited about LED backlit units – or paying more for them? In fact, LED-backlit TVs are some of the best selling (and highest priced) LCD TVs available today. Last year, Samsung made a lot of hay (OK, dollars too) over its new "LED TVs" that also captured some of the lowest power-draw numbers in the industry using edge-lit technology.

Spurred on by a bold marketing campaign in the spring of 2009, the company launched a line of new, pricy LED TVs with an ultra-thin low-power-consumption message that hit a chord with consumers despite a worldwide pull-back in spending.

While LED illumination for TVs is not new, Samsung made a strategic decision to launch a "new class" of TV it labeled simply "LED TVs," creating confusion at the retail level and drawing the ire of some analysts. But the gutsy recession-bucking plan that included higher-priced LCD TVs paid off in spades as Samsung dominated the high-end premium market with an 83% share of sets costing $3K or more each, up from just 4% a year earlier, according to Pt. Washington, NY, based NPD Group. Samsung sold 500,000 "LED TVs" in the first 100 days after the mid-March launch and reported a fivefold increase in earnings for Q2 over Q1. Some industry analysts attributed up to 80% of that growth to the LCD-TV performance.

Samsung showed that the green message could pay off in the market and that consumers would be willing to pay a premium for the LED-based LCD TVs. But interestingly, it was not the power savings as much as the ultra-cool thinness factor (and perhaps the idea of the "new" LED technology) that made the Samsung panels so popular.

Alternative Technologies

The Green Display Report also identifies other display technologies that could lead to reduced power consumption. These include time-multiplexed optical shutter (TMOS), a technology from UniPixel that the company claims significantly reduces complexity in manufacturing. Here is the technology description given in the company's report: "UniPixel's TMOS display technology promises to deliver displays with very low power consumption by combining a linear array of RGB LEDs at the edge of a two-dimensional array of electrically addressed pixels that couple light to the viewer utilizing frustrated internal reflection (FIR). When a polymer film, initially not in contact with the underlying polymer substrate, is deflected downward electrostatically and comes in contact with the illuminated polymer substrate, light is coupled outward from that pixel toward the viewer." On the production side, the company claims it needs just six layers and far fewer manufacturing steps when compared to LCD technology, and the front plane can move to a very efficient roll-to-roll process.

A second, temporal-based technology involves field-sequential-color (FSC) LCDs that, according to the Green Display Report, "operate by flashing the red, green, and blue LEDs in a rapid time sequence to create a full-color display. In an FSC LCD, each individual pixel is illuminated with red, green, and blue (RGB) light in sequence to produce a full-color image rather than relying on three individual, spatially separate RGB subpixels. FSC LCDs must be operated at more than three times the frame rate of non-FSC displays because each of the R, G, and B frames must be loaded and flashed in sequence."

This approach would allow display-panel designers to eliminate the light-absorbing color-filter arrays that add cost, thickness, and power consumption to LCDs. Along with other advantages, the FSC-LCD pixels can have larger aperture ratios leading to higher light transmission and lower power consumption.

Other (next-generation) technologies include a Pentile-type approach to pixel arrangement, using a unique RGBW-colored pixel configuration that more closely supports the way the human eye discerns colors.

Conclusion

So, as the state of California drives toward reducing the energy consumed by our most popular displays, LCD-TV makers will respond in kind. But the truth is the industry is marching in that direction – government mandate or not. Samsung proved earlier this year that low-power (sexy, thin) displays could sell for a premium and enrich the company coffers by taking bold moves in that direction. Sharp responded with its brand of direct-backlit displays using light-guide technology that blew away the low-power numbers of even the most efficient sets previously on the market. And as we continue the move toward next-generation displays, the industry will continue to re-invent itself with units that use fewer components and provide greater efficiency. •

 

Fig_2

Fig. 2: The new Sharp LED-based LCD TVs will sport "direct backlighting," perhaps with the use of a new light guide similar to this one from Design LED Products to improve light uniformity and reduce on-screen hot spots.

 


Steve Sechrist is an editor and analyst with Insight Media. He can be reached at steve@insightmedia.info.