A More efficient joule thief
I need to make a joule thief type of thing that can up the power from a 0.55V source to a simple LED. I know that the joule thief is not the most efficient circuit which is why I am asking if you know of an efficient circuit I can use.
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Reduce losses, better core, bifilar windings, biggest wire you can get away with - all tricks that will increase efficiency, but low voltages do not make for highly efficient switcher topologies, so the Joule Thief is a darned good little circuit.
Mar 2, 2010. 10:50 AMphysics_dude (author)
says:
Well then what can be the most efficient ferrite coil specs (i.e. windings, wire gauge) ?
Mar 2, 2010. 11:25 AMphysics_dude (author)
says:
No, I'm just looking for something really efficient.
Make the core bigger, so you can get the same number of turns of heavier wire. You ARE ultimately constrained by the fact you can't get good turn on from the transistor with such low biasing voltages. There are very low start voltage switch mode regulators from the likes of Maxim that bootstrap themselves to increase efficiency at low input voltages.
This is an interesting paper on SMPSU efficiency.
www.maxim-ic.com/app-notes/index.mvp/id/4266
and this one is the datasheet for a chip that allows you to build a VERY efficient
0.7V starting PSU
datasheets.maxim-ic.com/en/ds/MAX1708.pdf
This is an interesting paper on SMPSU efficiency.
www.maxim-ic.com/app-notes/index.mvp/id/4266
and this one is the datasheet for a chip that allows you to build a VERY efficient
0.7V starting PSU
datasheets.maxim-ic.com/en/ds/MAX1708.pdf
A joule thief is the most efficient homebrew solution you'll find -- otherwise you need a commercial power supply option "boost converter".
Where did you read that they are not very efficient? buck converters are 95%+ efficient and boost are usually 70-95% efficient.
Where did you read that they are not very efficient? buck converters are 95%+ efficient and boost are usually 70-95% efficient.
FYI, efficiency depends on load. Efficiency worsens on low loads with some topologies.
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