Highly Efficient 0-100% LED Dimmer

This webpage describes a highly efficient LED dimmer, or a dimmable LED flashlight, or a switching current source, or whatever you want to call it. Cheap, single-IC, uses commonly available parts, easy to build. Designed to get the longest light out of a (rechargable) battery, ideal in emergency situations: some 24+ hours for a single white LED at
Highly Efficient 0-100% LED Dimmer - schematic

full brightness from a cheap 9V, 200mAh battery. Works well from 4 up to at least 30 Volts; may even vary over time, while the brightness level is maintained essentially constant. Can drive as many LEDs as would normally be possible with the given supply voltage. Efficiency up to 94%(*), or even higher when a cunningly split supply voltage system is used. While I`ve been doing electronics for some 15-20 years, this happens to be my first web-documented project. That`s because it`s not quite trivial, it wasn`t yet documented anywhere in this form, and it`s potentially useful for more people than only me. Oh, and this project uses ideas from a variety of online sources, so "giving back" is also a motivation. For this project, some prior experience with electronics is required. I will not answer your questions, sorry. Instead, the explanation below is very detailed indeed. I should probably issue a WARNING for that. On the other hand, if your day job is to design lighting systems for cellphones or the like, this page won`t tell you much you didn`t already know. This project and webpage including all images are copyright © 2006 J. A. Bezemer, and are licensed under the terms of the GNU GPL ‰¥2. This basically means that you`re very free to use and modify and re-publish it, as long as you also publish your source material (e. g. files from your schematics drawing program), and preferably include a back-reference to this...

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