The way of white LED driver

All specially designed to drive white LED constant current IC offer evening most is based on the inductance or charge pump solution 9 both solutions have their advantages and disadvantages.

solution is also known as switch capacitor charge pump solution, using separate capacitor from input to output the power supply, the whole process does not need to use any inductance male so is popular solution. Charge pump power volume is small, the design is simple, choosing components usually only according to choose the appropriate capacitor component specifications.

the charge pump solution of main drawback is that it can only provide a limited range of output voltage, the vast majority of the conversion ratio of charge pump can at most reach twice the input voltage, which means that the output voltage can't be twice higher than the input voltage. Therefore, if you want to use white LED the charge pump driven more than one, will have to adopt the way of parallel drive. Using only the output voltage regulated charge pump drive multiple white LED, must use the ballast resistance to prevent the uneven current distribution, but the resistance will shorten the battery life.

inductive drive circuit small size in high efficiency, suitable for all too many portable electronic products provide a longer battery when asked. In the application efficiency of the inductive transducer can be adjusted, so that the volume between the efficiency and achieve the best balance. Most inductive solutions are using the boost converter, as shown in figure booster type solution can drive at most 6 or 7 series of white LED. This approach has the advantage of, because many white LED display built-in adopts serial mode, even if not put inside the white LED display screen, in most cases or strung them together. Backlight drive and white LED is usually in a variety of circuit boards, must therefore be a circuit board from the power supply to connect to another piece of circuit board. Drive 5 parallel white LED, need to use the 6 pin connector and drive in series with the five white LED only need two pins.

figure inductive step-up converter solution