Author Topic: Boost Converter for LED  (Read 1855 times)

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Boost Converter for LED
« on: August 19, 2014, 12:29:18 PM »
Individual LED are cheap, but fixturing is always a problem.  At a wharehouse store I found  18W flush mount lamps for $14 after power company instant rebate.  The LED took about 41V and the camp is 12V.  I'm fond of these 150W boost converters on ebay that are less than $5 shipped.  They boost up to 35V, limited mostly by the 35V cap.  I could have removed the cap, I've been soldering for 40 years but these cheap thru hole boards with no lead solder make that risky.  I would prefer just to bend the cap and break it off.

Anyway, I didn't do any of that.  The toroid has enough space under it, if not it can be soldered and lifted.  I added  a separate seven more turns of wire with a high speed diode and filter cap.  This was added in series with the output of the 150W boost converter.  I added a 1K pot in series with the 10K pot on the board.  This allows me to vary the brightness from 1/4W to 10W.  That is almost too bright for the bathroom.  Since I am no where near over current on the LED, voltage control is only on the boost converter.  It does not sense the total voltage on the LED.  I could have done that or sensed the returning current for constant  current control.  This is a quick cheap solution for some of those odd voltage LED.
 I have some 91V MR16 spots that I will be trying that next.

Winding direction does matter a little.  One way works better.  Might as well do two winding and have full wave. I look for 1/3 of voltage to come from 12V, 1/3 from boost, and 1/3 from extra winding

When I get some time I will try rewiring the factory converter that came with the lamp.  I should be able to use the output winding as the boost inductor.