Boost Driver for White LED Flashlight

Selecting Boost Driver for White LED Flashlight Circuits

Since your source voltage is lower than your LED voltage drop, you will require a boost topology. Many boost drivers have in input voltage range that starts around 2 to 3 volts. However, it is possible to find components that have a lower input voltage range. One part to consider might be the NCP1400A offered by On Semiconductor. The input voltage range goes from 0.8 to 5 volts DC, and with an output of 5 volts. Another On Semi part includes the NCP1422, with an input range from 1.0 to 5 volts DC, and an output of 5 volts. The first parts has a 100mA output current rating, as where the second part has a 800mA output current rating. Both parts are intended for LED flash light applications, so you should find either one very useful in your design. Since it is extremely unlikely that you will be driving a 5mm LED at 800mA, I would consider the first driver mentioned.