Continued from [LCD TVs Teardown] Power Consumption Compared [Part 1]
Nikkei Electronics Teardown Squad started to break down the Bravia "KDL-32J5," Sony's 32-inch energy-saving LCD TV, and removed its back chassis. But we could find only two substrates inside.
"No more substrates?" said an engineer from a Japanese TV manufacturer.
In general, LCD TVs have at least four substrates, which are a power supply board, inverter circuit board, signal processing board and timing controller board.
Why does the Bravia TV have only two substrates? After carefully examining them, we found one reason: the integration of the power supply board and the inverter circuit board.
This is probably one of the improvements made to reduce the power consumption of the TV. General LCD TVs, whose power supply board and inverter circuit board are separated, convert AC power from a household electric outlet to DC power via the power supply board and supply it to the inverter circuit board. The inverter circuit board converts the DC power from the power supply board to high-frequency AC power to light cold cathode fluorescent lamps (CCFL).
The Bravia TV, however, "uses AC power from a household electric outlet to light the CCFLs without converting it to DC power," said an engineer from a backlight manufacturer.
Probably, Sony enhanced the power use efficiency by eliminating the two conversion processes before lighting the CCFLs.
Where is timing controller?
Why can't we find more than two substrates? When further examining the substrates, we realized that we cannot find a timing controller board. Where in the world is it?
Actually, it existed on a side of the LCD panel module, integrated with the interface board connected to the source driver IC.
"This is an unfamiliar method," said an engineer from a TV manufacturer.
Why did Sony employ such a method? With this question unanswered, we continued to tear down the TV. After disassembling the panel module and removing optical sheets, four U-shaped (or eight) CCFLs appeared.
"In general, 32-inch LCD TVs use 10 CCFLs," said an engineer from a backlight manufacturer.
Probably, the number of the lamps was decreased to cut the power consumption. Smaller number of lamps means smaller power consumption. But it reduces the luminance and causes uneven brightness because of a larger interval between lamps. How did Sony address these problems?
An engineer from a backlight manufacturer started to examine the optical sheets.
"These sheets must be fairly expensive," he said.
Sony prevented the reduction in brightness by combining high-performance optical sheets, he said.
"To reduce the power consumption, Sony seems to have accepted some cost increase caused by using expensive optical sheets," he continued. "And it apparently made efforts to simplify other parts that do not influence the power consumption. The timing controller board and the interface board were integrated probably to reduce the number of components and enhance the production efficiency."
On closer inspection, there were some empty screw holes in the portion where there normally is a timing controller board. Probably, Sony used the same sheet metal used in its existing models to reduce the cost while integrating the timing controller board with the interface board. We finally understood why we could find only two substrates.