A DC/DC converter that drives white LEDs from a variety of power sources is described.
LEDs are usually driven with a constant DC current source in order to maintain constant luminosity. However, most DC/DC converters are designed to deliver a constant voltage by comparing a feedback voltage to an internal reference via an internal error amplifier. The easiest way to turn a simple DC/DC converter into a constant current source is to use a sense resistor to turn the output current into a voltage and use it as the feedback. The problem with this method is its reduced efficiency—700mA ...