Electronics > Projects, Designs, and Technical Stuff

LED driver circuit efficiency

(1/7) > >>

Federal Farmer:
Good day…

I scored a bunch of high power LED’s for free and have been looking at different drivers to power them with.
I picked up a kit at a local electronics chain store and reverse engineered it.
(If anyone is interested: http://www.gertweb.com/projects/images/LED%20Driver.pdf)



I built my own based on this design and took some measurements and found it's best efficiency was 75 to 78% @ 7.5 to 8v input.



Any suggestions on improving the above circuit or perhaps a better/different circuit altogether?
I was hoping to be at 80 to 90% efficient, or is this wishful thinking.
I have about 40 of these LED's so the cheaper the driver the better.

For an efficiency plot and other information visit my FB page.
http://www.facebook.com/media/set/?set=a.445878665445702.103623.100000707171935&type=3

EDIT 8/18/2012
Updated my personal web page to include this and other projects.
http://www.gertweb.com/arduino.html

HackedFridgeMagnet:
Hi Federal Farmer

There are people who don't use facebook, I am one of them.

But I am interested in Led Drivers, if you want to post your details somewhere else, maybe even in this thread.

IanB:
It's going to be hard to get above 80% efficiency for most power converters without a lot of effort. That's about the sweet spot where most designs end up.

Rufus:

--- Quote from: IanB on July 21, 2012, 07:16:01 am ---It's going to be hard to get above 80% efficiency for most power converters without a lot of effort. That's about the sweet spot where most designs end up.

--- End quote ---

Efficiencies in the mid 90s are not difficult for LED buck switchers. Harder if you are restricted to building on proto board.

If the OP is using exactly the circuit posted it will be loosing 10% or more just in the input bridge rectifier.

Federal Farmer:

--- Quote from: HackedFridgeMagnet on July 21, 2012, 07:05:36 am ---Hi Federal Farmer

There are people who don't use facebook, I am one of them.

But I am interested in Led Drivers, if you want to post your details somewhere else, maybe even in this thread.

--- End quote ---
Off Subject…
Facebook or something like it will become the government of the future.
Check out http://fora.tv/2008/08/08/Daniel_Suarez_Daemon_Bot-Mediated_Reality


Measuring the performance characteristics of the constant current LED driver.
 
At a “good” brightness level I measured 7.85 volts on the input and 6.12 volts on the output.
Also measuring the current at this level I recorded 92mA. This gives an efficiency of 77.96%
 (100 * 6.12) / 7.85 = 77.96%
 
At an “excellent” brightness level I measured 8.71 volts on the input and 6.57 volts on the output.
Also measuring the current at this level I recorded 284mA. This gives an efficiency of 75.43%
 (100 * 6.57) / 8.71 = 75.43%
 
The graph below is a plot of measured values showing input and output voltages verses current.
At the highest measured input voltage of 11 volts the circuit is 66% efficient.
Like all things in the physical world there are diminishing returns for applied effort.
There are religious aspects to science it is just a matter of observation and awareness. (I digress)

If anyone needs or wants help with graphing in Excel let me know.




This is actually my first proto build.
I used mostly the trimmed leads for the traces.
In hindsight I should have just bent them over and soldered them in place. (live and learn)

Q: Is it normal to mount the comparator in a socket?
I am thinking the original was designed this way because it has a shorter lifespan and this makes it easily replaceable.
Or is it just to avoid putting heat on a sensitive component? (thoughts or comments on this are welcome)





Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version