Converting 2.4V to 3.6V in torches

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varunme

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How 2.4V is converted to 3.6V in LED torches to lignt a 3.6V led ?
 

by using a small boost converter circuit
 
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    varunme

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you can even convert 1v -- even 0.5v -- to light 3.6v LED (which led is this btw ?)
google for 'joule thief' circuits
 
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    varunme

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I have seen torches with simple boost circuits, inductor and bjt's fedback with a capacitor to make oscillator. The current is set by leakage inductance and inductor on-time for discontinuous current. With the boost voltage clamped by the LED's own VI characteristics. Actually one 1.5V cell is enough for bipolar based designs.
 
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    varunme

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The 3909 IC flashed an led from a single 1.5V battery. It charged a capacitor, then switched its polarity to add to the supplyV, thus is could power a 1.8V led.

The 3909 is obsolete because the same function apparently can be duplicated by more advanced circuits and IC's (although I don't know what number to look for).
 
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    varunme

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