The backlight technology of large-size LCD screen is divided into side down type (or edge type) and straight down type (or matrix type). Due to its low cost and simple architecture, the side down backlight accounts for more than 90% of the market share of large-size LCD backlight. At present, domestic first-line brands such as Hisense, Haier, Konka, Skyworth, TCL and Changhong are committed to the development of LED TV with side down backlight architecture. However, because the direct down architecture has the advantages of more power saving, simple heat dissipation, better image contrast and local dimming, the discussion on using direct down (or matrix) LED backlight architecture has also begun to rise in the industry.

According to displaybank's analysis, the global LED market will grow rapidly at an annual growth rate of 19%. The main growth impetus comes from the backlight market of large-size LCD screens, including LCD and LED TV sets. There is no doubt that if the LED backlight architecture is changed from the current mainstream edge type to straight down type (or matrix type), the demand for LED in the industry will surge.

The main growth driver of the global LED market comes from large-size LCD screens.

At present, sharp company in Japan has been pushing the straight down concept and developing the solution of LED + lens. However, because only high-end models adopt direct down technology, major domestic manufacturers have not responded positively, so the shipment volume of this technology product is not large.

Yang Zhiyong, TV Project Manager of Ruifeng optoelectronics Co., Ltd., analyzed this for three main reasons: first, the cost of direct type is still slightly higher than that of side type; The second is the volume problem. Compared with the side down type, the TV thickness of the straight down type increases more; The third is the process problem. The production and processing process of full LED & lens is more complex than that of side down.

Considering the possibility of shortage of light guide plate and the characteristic function of local dimming of direct type, Ruifeng is actively developing and reserving this technology (COB, full led and lens + LED mode). Yang Zhiyong revealed that at present, Ruifeng optoelectronics has jointly developed direct projects with Konka, Skyworth and TCL.

Looking forward to this year, the direct down backlight technology will remain weak. Zhao Donghui, vice president of power conversion Department of Fairchild Semiconductor in Korea, said that now the proportion of direct down (matrix) LED backlight in the overall output of LED TV is less than 5%, and the proportion of direct down LED backlight is not expected to increase, because the price adjustment of LED is relatively slow this year, and LCD TV manufacturers are focusing on reducing the cost of LED backlight module (BLU back light unit) TV to replace LCD TV with cold cathode fluorescent lamp (CCFL) backlight.

Wu Tao, power product business development engineer of ti China

Wu Tao, a power product business development engineer in ti China, predicted that more models of direct down backlight technology products will be developed in the market in 2012. Therefore, the large-scale adoption of direct LED backlight TV architecture will not occur until at least two years later.

In terms of side down backlight technology, with the full investment of domestic first-line brand manufacturers such as Hisense, Haier, Konka, Skyworth, TCL and Changhong, the development of LED TV with side down backlight architecture is getting better and better. Due to the improvement of LED brightness, the price of single lamp is greatly reduced, and the backlight bar has also rapidly transitioned from the previous multilateral to the current narrow unilateral, which is close to CCFL in terms of overall cost. At present, the number of LED TV projects approved and developed by major manufacturers is also significantly more than that of CCFL.

Kin Shum, CEO of Xinkai Electronic Technology Co., Ltd., believes that the main reason for the low cost of side down backlight is that dozens or even more LED lamps can be connected in one LED string, so as to reduce the cost of the system. Therefore, high voltage LED driver chip will become the mainstream driver chip of side projection backlight.

Kin Shum, CEO of Xinkai Electronic Technology

Kin Shum introduced that due to its leading high-voltage technology, Xinkai can provide a series of high-voltage LED driver chips, which can drive up to 60 LEDs in each string. "In terms of efficiency, our competitor's LED driver chip can only drive 10 to 15 LEDs in a single string, so using our LED driver chip will greatly reduce the system cost." He stressed that the high system cost is the bottleneck hindering the faster development of the LED market. Therefore, with the decline of the production cost of the LED itself, the unique LED driver chip of Xinkai will have no small cost competitiveness.

Number of LED backlight drive ICs

At present, there are no standard LED chip requirements for specific size TVs in the industry. In fact, different LED TV backlight schemes use different numbers of LEDs, which depends on their led characteristics such as forward current and luminous intensity. Wu Tao estimates that about 200 to 300 LED chips can meet the needs of 42 inch or 47 inch led TVs. Zhao Donghui believes that many TV manufacturers only need to use 70 ~ 140 LED chips in 42-49 inch LED backlight TVs.