Design of High-Efficiency White-LED Driver

Low power white LED is the best choice for LCD's backlight in portable electronic products.Its driver can be regarded as a special power supply.Design of a high-efficiency PFM boost DC/DC converter is presented,which is capable of sourcing an output current up to 30 mA,with an input range from 0.8 V to 3 V and an output range from 1.9 V to 3.9 V.With external inductor and capacitor,it can start-up at 1.2 V without an external Schottky diode.Circuits of voltage reference and oscillator are analyzed in particular.Designed and simulated using 0.6 μm CMOS process,the device has achieved an efficiency greater than 80% when loading 20 mA and voltage precision better than ±2%,and the time to stabilize output voltage is 1.813 ms.