My new boards came today...

thefish

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So as some of you may know I have been working on some LED drivers... well today my first prototype boards showed up, I loaded them and they work great (just in time for a Cree XR-E test).

Specs:
  • 1 Watt
  • Voltage Boost
  • CC 350ma
  • Efficiency: 75% @ 1.5Vin 90% @ 3Vin
  • Dia = 0.78 +/-.02
  • 0.9-4.5 Vin
  • Voltage Cutoff = 0.9V (1.5V input), 1.8-2.2V (3-4.5V input)
BoardsA.jpg


Driver.jpg


EDIT:

They fit nicely into many of the cheap chinese lights that take 3 AAA batteries, since these are prototypes they have many extra features that will probably be eliminated in the future in order to make them smaller (such as a pot for infinitely variable brightness between 20% and 90%) and a Dip switch for selecting 1.5V input or 3-4V input... I have actually pushed Vin to 5.2V in testing but I have found it makes things get hot and if even a bit of a surge happens it will fry the IC.

Here is the test setup, with a beam shot Left: Ultrafire 602A (L1P Clone) Right: Test light:

testsetup.jpg
 
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Loomy

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What sort of control mechanism will you support for changing brightness? I personally think that lithium ion cells are the way of the future (and present) in flashlights, so I'm really interested in hardware that supports a 3v safety cutoff and 3 brightness levels.
 

thefish

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I am not really sure at this moment what is the best method to adjust the brightness levels, a digital pot would be one option but that adds a bit more complexity and maybe would not fit in the area available...

Now the question is what size (Dia) do these things need to be shrunk to in order for people to want them? The reason I picked its current size was 1 becaused my PCB fab will only rout boards down to 0.5 Square inches (0.80 Dia round) and 2 because I wanted it to fit some cheap lights I had for testing. Right now they fit in many cheap chinese 3 AAA lights such as http://contents.fifthunit.com/html/products.5th/sku.79.html but I doubt these are the lights people normally want to regulate (although I have one I plan to mod with this board).

Some interesting behavior I have noticed is that it will run about full brightness for 1 hour then start to dim for 15 min off (1 AA Rayovac IC3 2000mAh battery). Then the interesting part... It alternates between off and full power. High 10-15 seconds, off 15-20 seconds, high 10-15 seconds, off 15-20 seconds, ect. (built in low batt warning :grin2: )...
 
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havand

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thefish said:
So I managed to put on in the fifthunit light

http://contents.fifthunit.com/html/products.5th/sku.79.html

and it turned out rather well if I do say so myself, now I have a $4 light with a $12 driver does that make it a $16 light? :grin2: Well anyway thats all for now, unless someone has some good ideas to throw at me...

What size should I shoot for in the Dia?

Nice work! It'll be nice to have a driver that can take higher and lower voltage batteries. Is it capable of taking 3.7V lithium rechargeables?
 

thefish

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havand said:
Nice work! It'll be nice to have a driver that can take higher and lower voltage batteries. Is it capable of taking 3.7V lithium rechargeables?

3.7V is no problem at all, even @ 4.2V (Liion fresh off the charger) will be no problem. The fifthunit light I have been using as a test has 3 AAA batteries in it putting out 3.57V and it does great.
 

IsaacHayes

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So it's a buck/boost driver?? If it does 350ma CC and takes 3.7-4.2v then it's doing buck too? or does it by pass CC and go DD?

Perhaps make them fit 1AA lights since they work for 1.5v.. That way we could replace the ultrafire boards that don't fire on 1.2v...
 

thefish

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IsaacHayes said:
So it's a buck/boost driver?? If it does 350ma CC and takes 3.7-4.2v then it's doing buck too? or does it by pass CC and go DD?

Perhaps make them fit 1AA lights since they work for 1.5v.. That way we could replace the ultrafire boards that don't fire on 1.2v...

By design it should be just a boost driver and go DD if you pass Vf of the LED, however that being said the actual measurements do not back me up: (for all tests I am using a clone Chinese LuxIII)

Vin = 0.9V VLED = 2.997
Vin = 1.2V VLED = 3.01
Vin = 4.05V VLED = 3.28

I will do some more checks and try to get to the bottom of it.
 
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thefish

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Something I have noticed playing around with Liion cells is that the current draw starts off around 0.6A then the LED starts to flicker a bit as it does this the current draw starts to go up (to around 0.8A) then the LED becomes brighter and the current draw jumps suddenly to 1.4A!
 

jsr

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Interesting. I'd be interested in at least a couple if they are made the same diameter as the Q3 board. I love my Q3s, but see the inefficient driver as the main negative on that light.

I was also going to ask if it goes DD if Vin > Vf, but your measurements don't seem to show that. Let us know what you find out.

Does the IC have a feedback pin that allows the IC to internal self adjust (either PWM or PFM) the Vo to keep the current constant? If so, perhaps the IC has the unknown ability to skip some cycles, or output a voltage spike so short in a cycle that it actually drops Vo below Vin and resulting in a behavior that looks like a buck? If it's CC, it must have a feedback and either an external PWM/PFM or internal one to control Vo.
 

IsaacHayes

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If these are a good price, I may be interested in one if it indeed will do 350ma CC from a single NiMH AA (how long?). And fit in an ultrafire... I'm thinking a small ultrafire, with a cree would be awesome. I might lean towards li-ion for power instead, but will need a different driver and have to buy batteries/charger... :(
 
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