We all know that LCD liquid crystal display itself can not emit light, its light source are provided by the led backlight. Currently on the market the backlight mainly has LED and CCFL these two kinds.
CCFL backlight: traditional TFT-LCD usually use cold cathode fluorescent lamps (CCFL) as the backlight source, before the introduction of LED, CCFL dominated the mainstream market, mature technology, color stability, the price is also relatively low. However, the large volume, high power consumption and heat generation, short service life, can not adapt to the new generation of market demand, has gradually withdrawn from the market.
LED backlight: after the gradual withdrawal of CCFL backlighting, LED with small size, ultra-low power consumption, high brightness, low heat and long life and other advantages, so it was developed as a new type of LCD backlighting, and has been widely used. Today we mainly to understand the LED backlight.
LCD liquid crystal display LED backlight classification and features
LED that is, light-emitting diode, is a solid-state semiconductor device, can be directly converted to light, it belongs to the PN junction device, with unidirectional conductivity. Applied to the LCD liquid crystal display on the LED backlight according to the distribution of light source location is divided into side light type and straight down type. (Bottom backlight)
Edge lit type: is the position of the linear light or point light source is set in the special treatment of the edge of the light guide plate made of led backlighting, according to the actual needs of the application can be designed into a bilateral or trilateral. Side light type can be made very thin, but the utilization rate of its light source is very low, and the thinner the utilization rate is lower.
Bottom backlight type: is a flat backlight by a certain structure, can be a continuous uniform surface light source, can also be a more point light source by the composition (such as dot-matrix LED or incandescent backlight plate, etc., the brightness of the ground backlight is good, good uniformity, but the thickness is larger, when the use of more than one LED lamp, the heat generation is obvious, generally used for the low-brightness of the design.
TFT LED Backlight Driver
LED is a temperature-sensitive nonlinear components, temperature increases, the forward voltage drop decreases, due to the nonlinearity of the LED volt-ampere characteristics, the forward voltage as long as there is a small change, the forward current change will be very large, so it must be supplied with a constant-current power supply or current-limiting measures, otherwise, constant-voltage power supply, with the increase in temperature of the LED, the forward voltage drop decreases, the current will be more and more large, until it burns out.