As the LCD is essentially a selective filter, and ambient lighting create the display brightness is often not enough, therefore, must be placed on the back of the LCD light. Placed on the back of the light source means there are several different occasions, the back lighting applications, is different.
Early LCD on the back lighting is mainly used for laptop or notebook computers, as these devices are used in displays available battery power consumption accounted for 90% of the total, so people are most concerned about is efficiency.
Recently, LCD's main application has shifted to desktop computers, LCD's focus is also transferred from the original low-power high-brightness, brightness and image quality has become a top priority. Of course, efficiency is still one of the elements can not be ignored, because the user costs for the self-heating and power is still more concerned.
A method of back lighting
Electroluminescent (EL) back light body thin volume of light, providing a uniform light. Its power consumption is low, the required operating voltage of 80 ~ 100Vac, to provide operating voltage inverter can be input into 5/12/24Vdc transformation for the exchange of the output.
EL back light source because of the limited life (in 50% of the lighting conditions, the average life of 3,000 to 5,000 hours, at a higher brightness level will be much shorter life), so the ideal EL back light inverter allows the output voltage and frequency with the aging of EL lamps is increased, thereby prolonging the use of EL lighting on the back of the display has an active life.
EL back light for like watches, digital desktop clock and monochrome PDA, etc. need to be extremely weak illumination in order to dim light or dark conditions, the use of small reflective LCD applications is more applicable. However, low efficiency, low brightness, as well as short-lived so that it does not apply, such as laptop computers and flat-panel desktop monitors required by such a large LCD on the back of the transmission-type illumination purposes.
LED back light EL than the life of long (more than 5000 hours), and the use of DC voltage, typically applied to a small monochrome display, such as Feng Wo phones, remote controls, microwave ovens, stereo audio equipment. However, its brightness is not enough to provide for large-scale transmission-type display back light.
Small-scale cold-cathode fluorescent lamps (CCFL) to provide for the necessary large-scale LCD brightness and life (as well as lighting control capability), which is that it is still the most commonly used method of backlighting causes. However, heat accumulation is a matter of concern.
Back of the light source component has changed from the past, the relatively modest power levels driven one or two CCFL increased to 30W or 60W of power for up to 12 (or 16) root tube. As a relatively small space, there are used so much power, therefore, accumulation of heat source component makes the display on the back of all the components are in the majority of the early lcd module applications do not occur on the level of force. Moreover, the electrical efficiency and lighting control capacities are also close to the limits.
2 to change the requirements of inverter
In a surface light source with CCFL backlight, 18-inch standard flat panel display (FPD) has shown that the logic circuits and DC / AC inverter may respectively require 10W and 55W of power. 65W total power in this, only very little of it is converted to light, most were converted into heat.
Multi-tube back light source of the heat also have serious scattered, making its optical efficiency is very low. As the FPD component made of very thin, so more than 50W of heat had a very small space dissipation away.
In order to achieve the best thermal management, the display case must be appropriate ventilation measures. Moreover, all components including: housing, CCFL, display and inverter must display case for the actual operating temperature (up to 150 ¡ã F) to design and requirements. FPD with the ideal of today's multi-lamp inverter can provide about 90% efficiency and a direct connection with the display, low power, 0 ~ 100% flicker-free brightness control, up to 60W of output power, integrated input and output connectors.