Boost LED driver

[Cloud]

Hello,
I am looking for a boost led driver, for a LED with U=3.15-3.4V, I=0.2-0.3A. And I want to power it from a AA battery (preferably rechargeable). What would you recommend?

[Paul Price]

C B lo

[bktemp]

MCP1643 is the LED driver version with constant current output.

[SeanB]

You get 3 pin boost converters specially made for this. All you need is the small SO device, an inductor, an input decoupling capacitor and connect the diode across the output. works well for a torch off a single AA cell.

I bought a few $2 torches with the whole circuit and a 5mm LED inside, just to take the LED module out, fix the poor assembly ( they wire the led incorrectly on about 1 in 2) and use them as incandescent lamp replacements. Same light, brighter colour temperature but about 1/4 the current draw. On an emergency lamp it now lasts 4 hours instead of 30 minutes.

[Cloud]

I ordered MCP 1623 and 1643s  and will report when I get them 

[T3sl4co1l]

?

If you don't need fancy control, a single transistor will do the job.

Tim

[Whales]

I've just spent the last few weeks getting a 34063 to boost 12V to ~32V peak and run as a constant-current source.  I blew so many ICs until I had the over voltage protection circuit going, and even now it has faults.  I did learn much more than if I bought some better parts however 
T3sl4co1l: is that a joule thief?

[Cloud]

I was thinking about joule thief, but i don't think there will be enough space, since I want to make a compact and reliable flash light

[T3sl4co1l]

Well, that one has a capacity a bit larger than your spec, so if that's too big, you're going to have a problem no matter how you cut it.  You will always need the same basic circuit, whether driven by a single transistor or a fancy IC.

Tim

[DmitryL]

Hello,
I am looking for a boost led driver, for a LED with U=3.15-3.4V, I=0.2-0.3A. And I want to power it from a AA battery (preferably rechargeable). What would you recommend?

LTC3490, I used them, nice ones.
On the other hand, you may try doing a parametric search on a sites like Farnell, Digikey etc., you may find a bunch of drivers that suit you.

[bktemp]

You will always need the same basic circuit, whether driven by a single transistor or a fancy IC.

The main advantage of a special IC over the simple joule thief circuit is the synchronous rectification: If you drive a single white LED you are losing either 0.5V on a rectifier diode (~15% loss), or the LED gets pulsed by a high current (>100mA to get 20mA avarage. Both reduces the efficiency substantially. Another advantage of the ic: The output current is regulated. The brightness will stay constant when the battery discharges until the ic can not deliver enough current when the voltage goes below around 0.7V.
I have build similar 1 transistor led drivers many years ago and they are still used occasionally, but today I prefer the MCP1643 or similar ics, because you can achieve better performance.

[paulie]

The array needs over 20V at a few amps.  The transformer is tucked under the heatsink.   Paralleled a couple of 9Vs to it.

I suspect it will take more than a "couple" 9v to supply "a few amps".

[dave_j_fan]

Inspired by Tim's single transistor flashlight, I decided to build my own little portable LED flashlight.    A friend gave me a 2000 lumen Bridgelux LED array that has been sitting around for about a year.    I mounted it to a old computer heatsink along with a single N-channel FET.   The array needs over 20V at a few amps.  The transformer is tucked under the heatsink.   Paralleled a couple of 9Vs to it.   Held together with hot glue.  Yea, its not my finest work.   It's fairly bright even with the 9 volt batteries.  May get one of those USB battery packs to run it. 

Put the camera on a tripod, and took a picture with the normal lights, with the lights off, then with me holding the flashlight.   



 

very nice .. from text i suspect joeqsmith=daveJones himself

[T3sl4co1l]

Hmm, you'd be able to run that a little while from a couple or more LiIon cells, but 9Vs aren't gonna cut it for power or energy capacity.  You're probably not getting much more light out of the poor boy than mine! On the upside, a flashlight using one of those at ratings is probably a little *too* aggressive, anyway. 

Tim