AN027

AN027 Applications for White LED Driver in Parallel vs. Series Introduction For the past few years there has been a huge revolution in color LCD displayers for hand-held devices, such as cellular phones, PDAs and DSCs. White Light Emitting Diode (LED) Module, a new technology for LCD displayers, plays an important role in the applications powered by a single-cell Li-ion battery. Due to the operating voltage limit (3.3V~4.2V) of single-cell Li-ion battery, it cannot drive white LEDs, which require a forward voltage at 3.6V. Therefore, we need a boost circuit, which is powered by a single-cell Li-ion battery, for white LEDs. Generally in mobile phone applications, white LEDs are usually used in two models－series and parallel. This application note points out several differences between these two models, and then gives corresponding solutions. The Model of White LEDs Driver Parallel Model－Charge Pump Converter For driving LEDs, fig.1 shows a parallel model solution by using AIC1845 ...