Analysis of the dimming principle of LCD TV LED area backlight

Now CRT (negative ray tube) TVs are gradually being replaced by LCD TVs, and at the same time, the number of household purchases is steadily increasing, and the average American household now has 2.4 LCD TVs, much higher than the average of 1 CRT TV per household in 1990. Although the power consumption of each LCD TV is decreasing year by year, the increase in its penetration rate has increased the total power consumption of each household TV year by year, and among household appliances, LCD TV has become the main power consuming appliance after the refrigerator.

Therefore, a series of LCD TV energy-saving standards have emerged, the most stringent of which is the EPA Energy Star 5.0 standard, which will take effect on May 1, 2012, especially for large-screen LCD TVs over 50 inches, which impose a mandatory energy consumption ceiling of 108 watts for usage mode. For the first time, the Energy Star Energy Saving Standard also regulates the absolute energy consumption of TVs, which is different from the previous relative standards corresponding to screen size.

Over the past 10 years, we have witnessed the development of signal processing paths for LCD TVs: multiple functional modules are gradually integrated into a single chip, which rapidly reduces costs and energy consumption. Similar developments and innovations have occurred in the power path of LCD TVs in recent years, the most important of which is the unit function of the largest energy consumption in LCD TVs, that is, LCD backlights that exceed more than 60% of the total energy consumption of LCD TVs.

Just as the backlight of notebook computers has basically completed the conversion from CCFL (cold cathode fluorescent light) to LED backlight in the past two years, the conversion of LCD TV backlight will be completed in recent years. Its main energy-saving effect comes from the photoelectric conversion efficiency of LED higher than CCFL, and with the rapid development of LED luminescent material technology, its energy-saving effect will become more and more obvious. Make move.

The most straightforward LED backlight method of LCD TV is to follow the LED backlight scheme of notebook computers, arrange multiple LEDs in a row, and place them on the upper and lower sides of the LCD display. In this way, the LCD TV can continue to retain the advantages of low cost and slim size of the notebook computer LED backlight, and to a considerable extent, retain and simply extend its existing production line and process, especially for small and medium-screen LCD TVs, which is an effective solution. In order to further reduce costs, even the LED backlight solution with only one side of the lower side has been used in small-screen LCD TVs.

After this side-down (Edgelit) LED backlit TV entered the market, it was widely favored by the market because of its slim popular style, further improving the market position of LED backlit LCD TVs and catering to the needs of more price-sensitive customer groups. At the same time, from a technical point of view, scientists and technicians use the rapid photoelectric conversion speed of LED to invent regional dimming technology, combined with the side down or direct LED backlight structure, the whole screen image is divided into 1 or 2 dimensional areas, and according to the content of the displayed image in each area dynamically adjust the regional LED backlight brightness, greatly improving the image contrast and color saturation, while further reducing the energy consumption of LCD TV. The image quality of LCD TVs has been improved to a level that is far superior to that of CCFL TVs and PDP (plasma) TVs, catering to the needs of customers who are sensitive to image quality.

iWatt is a technology leader in the field of LED area backlighting, with its years of successful experience in the field of digital power and its position as a leader in the LED lighting and smart power market, to promote its digital power control technology to LED backlight applications for LCD TVs. iWatt's original patented adaptive intelligence technology can automatically detect and compensate for LED voltage drop (VF) mismatches, making it possible for multiple channel LEDs to share the same power supply, and combined with the power of its digital power supply, solves the well-known integrated heat loss problem of high voltage switches and rectifier resistors. In 2010, the world's first 64-channel fully integrated LED driver chip was launched, replacing all the functions traditionally required to use four 16-channel chips, 32 dual-package high-voltage switching transistors, and 64 current sense resistors, reducing the total number of key device pins from the original 576 pins to only 88 pins , and its powerful SPI programmability makes the chip equally suitable for side-down and straight-down area dimming. While providing high-quality and low-cost LED backlight, it further reduces the energy consumption of LCD TVs, providing customers with the lowest cost and smallest LED backlight solutions.

If the 170 million LED-backlit LCD TVs sold worldwide in 2012 were dimmed side-down or direct-zone, 30 megawatts of electricity would be saved, enough to supply the total electricity consumption of all households in New York City for 10 months.