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Design of LED backlight source type ultra-thin structure

Posted On:2017-09-09 15:14:04

1, structural design
The LED backlight source designed in this paper is a side light type ultra-thin structure. The entire structure includes: LED light bars, drive plates, film materials, light guide plates, heat dissipation blocks, upper frames, and back plates. The back light source uses a white LED. The entire structure design uses the center point of the Active Area as the design center of all components. The other dimensions are designed on the premise of the size of the LCD screen used in LCD TVs.
The structure is designed taking into account the requirements of circuit design and optical design. The structure design begins with the layout diagram of U IV OUT, expresses the assembly relationship between the whole mechanism and each component, and then proceeds with the structure design of the part diagram. The upper frame adopts a segmented design and is segmented in the length direction to avoid long lengths. The outlet end of the lamp bar is set at the four corners of the back plate to reduce the length of the winding line.
2, optical design
The role of the backlight module is to turn the light emitted by the point light source into a surface light source through diffuse reflection. In order to obtain a qualified surface light source, we must first select a suitable LED. This design uses a white light dual-chip LED. Through the preset white field photometric index, combined with the study and analysis of the influence factors such as liquid crystal screen and optical film, the calculation of the required light flux for the entire back light source is completed. According to the calculated luminous flux, the number of LEDs required is calculated based on the optical characteristics of the LEDs.
In order to increase the brightness of the back light source, the membrane structure is matched with: one layer of diffusion plate + one layer of BEF + one layer of DBEF. Among them, the role of the diffusion sheet is to atomize the light by the refraction and reflection of the diffused material, so that the emitted light is more uniform: the role of BEF is to gather the light. Make it vertical into the liquid crystal module to increase the brightness: DBEF uses 50 % of the light that was originally absorbed by the traditional absorption polarizer to increase brightness. The diameter of the guide plate dot is 0.54 ~ 1.55 mm. And ...
3, circuit design
The design of LED backlight circuit mainly includes lamp bar design and drive control circuit design.
4, light bar design
The light source uses a double-chip white LED, and the light bars are distributed around the back light source. In order to achieve better current homogeneity, the lamp bars are mixed with strings and two and more strings are implemented. In order to achieve better heat dissipation effect, LED light bars are made of aluminum substrate processing. The entire system input voltage is 24V, which is provided by an external power converter.
5, drive control
The circuit design drive chip is a three-way peak current mode PWM controller that provides high-precision LED current through closed-loop control output current. The chip contains three peak current mode controllers that provide feedback to the IC to ensure higher efficiency and higher precision. The gate drive on the chip is optimized to drive the logic level FET of 0.25A source current or O. 5A sink current. Each output current can be dimmed separately by linear or PWM dimming methods.

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