Analysis EL backlight driver works TFT Display Module

With the popularity of civilian high-tech products, the former only in the driver's seat cabin aircraft using electroluminescent technology is now widely used in civilian handheld devices, mobile phones, pagers, cordless phones, personal digital assistants, remote control, etc. products, since the EL backlight mode with a small size, light weight, low temperature, low power consumption, no flash, light uniformity and other characteristics, has been gradually replacing the traditional way of LED backlighting.

EL backlight system is composed of EL lamps, and an EL driver. EL lamps typically have a thickness less than 0.2mm, the insulating substrate is sprayed and an electroluminescent material sandwiched between two layers of electrode composition. EL electroluminescent lamp provider can by using different luminescent materials, such as zinc sulfide, calcium or strontium sulfide, and then doped with other ingredients such as magnesium, samarium, europium or add fluorescent dye, etc., to adjust the brightness of the light and color. Changing the excitation frequency can cause the same color of the light changes, when the frequency increases to a bluish color change in direction, and when the frequency is decreased to a greenish color change in direction, EL light film is the original color of the excitation voltage is 200V / 400Hz when the EL lamps luminous color. QVGA lcd
EL lamps with strong flexibility, without the premise of electrode breakage, can be arbitrarily cut or bent without affecting the luminescent properties; moreover, EL lamp film is a "flat" transmitter relative to the LED light source, without light guide plate diffuser can achieve full-surface uniform light; addition, LED is a "hot spot" light, localized "hot spots" are often sophisticated electronic systems will bring unexpected interference, EL lamps is a cold light source. Relative to the LED backlight system, EL backlight system is another advantage of reducing power consumption. EL lamps require only a high voltage, load current required is very small, about the range of 0.03 to 1mA/cm2, in general, the EL lamp is less than 10 cm2 area, the operating current of several mA or so . However, only one LED on the drive 5 to 10mA of current. Low power consumption for battery-powered equipment, has considerable significance. Judging from the electrical characteristics, EL light sheet has a resistive and capacitive characteristics, the equivalent circuit shown in Figure 1, the capacitance is typically 2 to 6nF/in2 (EL lamp the better the quality the smaller the capacitance characteristics). Resistor is typically 50 to 15000KOhm/in2. EL driver circuit with a maximum drive size and brightness will vary depending on driving EL lamps which are quite different. EL lamp brightness piece is the combined effect of several electrical parameters. Generally, the driving voltage peak increases, increased brightness; driving voltage frequency increases, the brightness increase (up to a few thousand hertz when the frequency, the brightness will decrease gradually increases); on the other hand, the frequency of the drive voltage increases , EL light emission efficiency will be reduced sheet; course, EL light film of material, quality and structural efficiency of the light emitting brightness and also has a great impact, for example, EL lamps of different colors with different efficiencies, the green maximum efficiency. Furthermore, EL lamp brightness chip mapping unit is a reflection of active light sources fL (foot lamberts) or nits (cd/m2, cd / sq m), 1fL = 0.2919nits, instead of measuring the intensity of light reflected from an object Lux (lux ). serial 16x2 lcd