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LED backlight to replace CCFL in large-screen LCD TVs

Posted: 14 Mar 2007 ?? ?Print Version ?Bookmark and Share

Keywords:LCD TV? LED backlight? CCFL? panel? desktop?

Since home appliances such as air conditioners and refrigerators have become necessities for many families, energy conservation on these white appliances has been neglected over the years. However, with the entry of large-screen TVs and home audio systems in homes in China in recent years, the power consumption issue could no longer be ignored.

"The core of black appliances is audio and video, so energy conservation will start from video and audio system design," said Mao Yu-Hai, chief scientist at Power Analog Microelectronics (PAM). "For example, in LCD monitors or LCD TVs, we can make use of much more power-saving LED backlight to replace CCFL (cold cathode fluorescent lamp) backlight in video part, and in audio part, we can use Class D amplifier to replace Class AB amplifier."

Reduced consumption
In LCD panels and LCD TVs, most of the power is consumed by the backlight source. These days, almost all desktop LCD monitor and LCD TV utilize CCFL lamps that consume a lot of electric power since they have to be driven by high voltage inverter.

"When using LED backlight, the power consumption can be reduced by 50 percent. In Samsung's 40inch LCD TV, it consumed 170W. After it changed to LED backlight, it only consumed 100W," Mao said.

Besides the power saving advantage, LED backlight is capable of realizing color saturation beyond NTSC ratio of 100 percent and can replace color filter.

At the 12th International IC-China Conference and Exhibition, PAM demonstrated its new LED driver chip, PAM2701, for driving LCD panel or LED backlight in cellphones or PMPs. Mao said that PAM is developing LED driver IC for many serial LEDs for larger panels' backlight usage. The ultimate target is to replace CCFL backlight with LED backlight in large-screen LCD modules (7inch to 46inch).

Mao added that according to iSuppli, about 7 percent of desktop computer LCD monitors use LED backlight and vendors from Taiwan expect that number to increase up to 25 percent.

The biggest challenge, however, with the use of LED backlight is cost. Mao explained that as temperature increases when the LED is lit, LED chrominance will also gradually change. Because of this, the cost in large-screen LCD TV applications will greatly increase for LED backlight than that of CCFL.

According to Mao, since most consumers are not aware of the energy conservation for black appliances, local manufacturers would not actively produce power-saving black appliance with cost in mind. He added that because the benefits of energy conservation belongs to end users, manufacturers will not actively adopt power saving design solutions when energy precautions will increase the cost for them. The key, Mao said, is for the government to take actions to define related regulations to be forced into application.

- Freddy Ma
EE Times-China




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