Phone color LCD screen backlight general use two LED lights -8 stars, and their drive single or parallel constant current power supply most of the way. Since 2000, mobile phone color LCD screen used LED driver has a DC / DC switching regulators, charge pump, the constant-current source and low dropout regulator (LDO).


DC / DC switching regulator is to be stored electric power sensors, and the inductor AC motor capacitor switching frequency easy to launch and easy for a new radio frequency interference, in the mobile phones used less.


Charge pump is a switching regulator, but it is used for electric energy storage capacitor, and therefore it would not launch switching frequency, cell phone products accounting for the largest share.


IF constant current LED luminous requirements, constant current source for this market is a special design, production, constant-current charge pump price is the source of 50 per cent, thus in recent years the popularity of mobile phones has a certain share.


LDO is a very good performance low dropout regulator, the output voltage stability, when the same load, it flowed load current is constant, and based on this principle LDO is a good LED driver.


LDO regulator in the work - steady flow model, the use of absorption resistor to AC motor capacitor obtain approximate matching white LED brightness, as long as the basis of an LED forward voltage can be adjusted automatically change the bias voltage can be improved when mass production LED matching of the requirements of increased tolerance. The rated output current LDO larger, and for LCD backlight drivers use it only when the output capacity of 1/5-1/3, redundancy more difficult chip fever, heat dissipation without paying too much attention to the problem. Thus the 300 mA-500mA LDO do universal phone LCD backlight drive is a low-cost design choice.


On the phone with current LED driver IC market prices, a DC / DC switching regulator is the price of 0.12 US dollars -0.15 dollars, a charge pump is the price of 0.18 US dollars -0.25 dollars, the price of a constant current source -0.12 dollar is 0.09 US dollars, while the price of LDO only a few cents. Lowering the unit cost of mobile phone backlight drivers, LDO really quite attractive, in recent years many popular cell phones have been used.


From the charge pump, constant current source, low dropout regulator AC motor capacitor performance / price comparison, charge pump, constant current source, LDO for use backlight little difference between the actual results. Charge pump, constant current sources, the efficient use of LDO there is a gap between theory, but in VLI lithium battery voltage of 3.0 V to 4.2V, the actual efficiency in the use similar. In addition, the LDO use their lower power consumption, the use of a lower cost.