White LED driver circuit Character LCD Modules

At present, the white LED is mainly used for a color display of mobile phones and TFT PDA, the uniformity of a TFT-LCD backlight requires three to four or more white LED, smart phones may require six or more white LEDs. Due to the increase in demand for white LED. A strong impetus to the growth of the market of white LED driver. Linear Power Division product marketing manager Tony Armstrong estimated that: "mobile phone shipments in 2003 will be more than 400 million, of which at least 60% to 70% is a color screen cell phones, in addition there will be 1000 color PDA market will hundreds of millions of white LED driver, the white LED forward voltage drop of 3.5 V, when a single lithium battery similar, therefore, need a boost converter to solve the white LED forward voltage problem.
Boost two solutions: First, the charge pump (switch capacitor), its small footprint, but the efficiency is low, National Semiconductor has introduced the white LED driver using this switched-capacitor, the company believes that if boost converter, when the drive is in the off state leakage current will; inductive switching boost, the advantage of high efficiency, but the area occupied.OLED Display Module
At present, most of the white LED driver manufacturers are inductive switching boost, such as Catalyst CAT32 White LED Driver, it works on a fixed frequency of 1.2MHz, it can enhance the low-voltage battery voltage and automatically adjusts the drive current, can support up to four series with white LED. The company is developing CAT32 more advanced white LED driver, it can control the current MPU, and integrated passive components, thus saving costs. Linear has introduced a white LED driver integrated on-chip Schottky diode, drive circuit requires only two external capacitors, a resistor and an inductor. The general white LED driver integrated MOSFET.
White LED driving circuit by a white LED drive and a peripheral circuit (including transistors, diodes, inductors, capacitors, and resistors, etc.). Drive white LED requires a constant current source, the current is typically 15mA ~ 20mA. The luminance of the LED depends on its forward current, so a plurality of white LED used in tandem, can ensure that the same current flowing through each of the white LED. Forward set for four series white LED 14V voltage, the voltage boost regulator to enhance the single-cell lithium battery (2.7V to 4.2V) it said operating voltage.COG LCD Display