LCD TV Backlight LED light Bar Analysis and Maintenance

 

Light source structure

The backlight source of LED LCD screen consists of multiple groups of LED backlights. The backlight source is divided into two types of installation: side-entry and straight-down, and the structure is slightly different.

Directly under the type is made of LED into a dense array of dots, placed behind, directly irradiate the screen. The straight-down backlight needs to be placed at the back of the screen, and each LED bead has a lens on it, which increases the thickness quite a bit.

 

Side-entry LED backlighting refers to the LED backlight placed on the side of the screen, the light emitted through the light guide plate to illuminate the entire screen, which can make the whole machine more light book. Side entry LED strip is installed on the top or bottom of the light guide, left or right side.

  

Light bar structure

The performance and parameters of each LED strip in the same screen are the same. SMDLED is surface mount light-emitting diodes, referred to as the paste LED beads, SMD beads common models are 0603, 0805, 3020, 3014, 3528, 5630, 7030 and so on, SMD series beads are generally named after the size, such as product size 7.0mm * 3.0mm, so called "7030" lamp beads.

Each SMD LED beads using pressure welding process assembled on a metal strip, generally a metal strip of SMD LED beads have a group or more than one group composition, each group is made up of multiple single LED beads in series, a strip of very few both string and parallel structure, in addition to the universal modification of the light bar.

It is worth noting that there is a difference between the lamp beads on the backlight strip of LCD color TV and the lamp beads on the lighting fixtures nowadays, not only the difference of model, body prompt, size, but also the difference of color temperature, brightness, voltage, etc. The key is the current, the current of the lamp beads on the lighting fixtures generally does not exceed 20mA, while the current of the backlight strip lamp beads is several times larger than it.

 

How to determine whether the lamp beads are damaged or lamp beads drive the constant current circuit damage

Measure the voltage between the constant current source backlight board output socket LED + and LED -, mainly after the second power on there is no instantaneous voltage to determine, if there is and then slowly decline, most of the LED strip problems, direct replacement can be; if not, the general constant current driver circuit failure.