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Analog Circuit Design Volume Three by John Hamburger, Bob Dobkin

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Chapter 298

DC/DC converter drives white LEDs from a variety of power sources

Keith Szolusha

Abstract

A DC/DC converter that drives white LEDs from a variety of power sources is described.

Keywords

LED light

boost converter

LT1618

Introduction

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 ...

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