1.2V Drive 7 High efficiency white LED flashlight

High efficiency white LEDs have advanced to the point where they can replace glow bulbs and other light sources not only as indicators, but also for illumination. While many of the claims made about the LEDs’ efficiency, light quality, lifetime and economy are mostly exaggeration, the truth is that for very low light levels they are now competitive. They have equal or slightly higher efficiency than a flashlight bulb, a longer lifetime, and are very much tougher. On the other hand, they are still far more expensive than a bulb, for a given light output.

The circuit is a self-oscillating boost converter, and I certainly cannot claim having invented it. It is ages old! I only did the detail design of this one, and optimized it in the course of one afternoon. It runs with a beautifully clean waveform, with all components except the LEDs staying completely cold to the touch. At this low power level, even that doesn’t guarantee a good efficiency, but I measured it at about 72%, which is quite good for a circuit operating from such a low voltage!

Source :http://ludens.cl/Electron/ledlamp/ledlamp.html
Thank you.

1.2v LED Flasher - Joule thief
This is a 1.2-volt single transistor flyback (Joule Thief) circuit that features a third coil. With it, flash duration and brightness is much enhanced, even with just a 10uF capacitor, as can ...
Mains Powered White LED Lamp
Did it ever occur to you that an array of white LEDs can be used as a small lamp for the living room? If not, read on. LED lamps are available ready-made, look exactly the same as standard hal ...
2C cell LED Flashlight
Next we have the circuit from an actual LED flashlight. This circuit is so small that it fits inside the "bulb base" behind the reflector in a 2C cell flashlight. All of the parts are surface mo ...
4011 Dual Led flasher
This simple circuit uses NAND Gates to alternately flash two led's. The two 47uF capacitors determine the flash frequency. It is a good idea to use a decoupling capacitor across the power supp ...
Fading LED by LM358
This circuit uses op-amps to obtain a triangle wave. The triangle wave causes the Led to slowly get brighter and then slowly get dimmer until it isn't producing any light. It then gets slowly ...