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Joule thief? Answered

http://joulethief.com/kit.php : It was from here that I built my first working joule thief. (I've found better ones now.) Anyways, last week, I got bored and tried to destroy an LED by feeding the circuit more and more power...I got to 18V (laptop charger adapter) and it still didn't bust. Why?

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frimm

Best Answer 8 years ago

 The joule thief does its work when the transistor turns off. With a higher than normal voltage, all you're doing is keep the transistor on much longer, which will do nothing but burn up power.

I suspect all you get is an uncomfortably warm coil.

For some reason the input voltage dose not greatly affect the output voltage but I have know idea why.

The coil must be limiting the current thru the led.  The transistors are also taking up some of the load.

Or maybe it's just a super-led!