Anyone worked with either of these drivers from Lightmalls?

I assumed that AOEC was an Alpha and Omega Semiconductor FET since it started with AO. Now I realize that I was probably wrong about that. Who knows what those markings indicate, but I think it’s a fair guess that replacing the FET is a good move. May as well replace both of course.

My test LED is on a little (20mm diameter x 25mm tall or so) copper rod. I sit an LED light bulb diffusing dome over top of that. It’s generally fairly easy to tell the modes apart, but things do still look very bright on either high or a short… so I know what you mean.

Sorry, re. “leave”, I meant leave my basement, where I have my so-called workshop set up :).

I’ll try to check if the QX92920/LEDA 1322 pin connections are as you suspected above.

EDIT: And I have some of those AO FETs in my Digi-key cart.

OK, but the pins I discussed in the post you quoted are NOT for the QX9920. They are for the modes chip, the unmarked SOT23-6 package chip.

Ok, sorry - understood.

I know that I keep going off-topic on this thread, but despite wanting to fully paramerize this driver, I’m really “feeling the need” to put one of these in a small/tiny host :(. I was messing around with the one with the R100 stacked on the R200, with an MT-G2, and got to 6.2V @ 2.99 amps on the emitter (according to the el-cheapo laser-guided thermometer I had, the emitter got to 197F, and the driver to about 98F, so things would get a bit toasty :laughing:!

Wherever you put it, the driver will need to be heatsinked.

No thermal protection, no LVP, no turbo stepdown… sounds like a pipebomb ;-). And I’m not saying I wouldn’t do it. :-p Just take the usual precautions. 1/2 twist will fully lock out a Roche F12, so that’s maybe an option for 2x18350 & an MT-G2.

I’m actually thinking smaller than 2x18350 :)…

EDIT: I did say “tiny” :)…

Now that I think about it I doubt that 2*18350 would fit in that host anyway.

FYI, I haven’t abandoned or given up on this yet. I’m still waiting for the new FET and diode. In the meantime, I’ve been trying to get one of the drivers (the one with R200 and R100 stacked) into a small light, but the pill was too short to accommodate this driver with the toroid (the toroid was just a tiny bit too tall), so I’m back to waiting for the parts.

I’ve been thinking that when the parts come in, I may pull the toroid off, so I’ll take pictures if I do that.

It may be possible to use an SMD torroid on air-wires instead of that big one. OTOH we don’t know the inductance so we’d be guessing and might fry stuff.

Let’s see how the new FETs and diode do first. I wasn’t necessarily interested in putting the driver in that particular light… it was more to kill some time.


The diodes and FETs from Digikey came in earlier this week (they ship FAST), but I hadn’t had time to try them until now, and I only had time to try a quick swap of the diode so far on the board that has the R100 stacked on top of the original R200.

It was kind of a pain, as I don’t really have any SMD tools, so I just used my soldering iron to pull the original SS34 off, which left solder still on the pads, so I then put some flux on the pads (my original intention for that was mainly to prevent the new diode from blowing off the board when I used my heat gun). I then put the diode on the pads, and used my heat gun, on “low” blower setting, but with the highest temperature, and was pleased that it actually reflowed the new diode without blowing all of the other components off of the board.

Anyway, I re-soldered the toroid and the emitter leads, and did a quick test and the driver still worked (it still has the blinky modes, etc.). I only did some short tests, maybe 30 - 60 secs on high, measuring at the emitter with a clamp, I was able to get 4+ amps at the emitter, and no puffs of smoke or burning odor.

Note that I haven’t switched the FETs (the A0EC/AOEC?) out yet.

Now, I have to really find a light to put this into, as the pill on the one I tried earlier was much too shallow (height-wise).


P.S. Emitter was an old XM-L something that I had reflowed on to a Noctigon, and the Noctigon was sitting on a 2” x 2” x (maybe) 1/4” piece of copper from an old CPU heatsink.

EDIT: This is the diode I used for the above:

EDIT 2: Here’s a pic I took of a test. The emitter wire is looped through the clamp meter, as wight (I think) suggested, so the current (8.89) is twice the actual emitter current (~4.45 amps). The current (4.5 amps) and voltage (4.7V) on the power supply display (in the background) should be about right:

LowLumen suggested looping the wire on your clamp meter to improve the results, not me.

Is your PSU set to 4.7v? That’s not telling you much since you’ll never hit that voltage with li-ions.

I could get to 4.7V (or more) with 2xLi-ion :)…

EDIT: Thanks for correcting the reference about looping the wire also…

Bump this thread. Apparently this is the driver used in the Uniquefire 1405. So is this the only 16.5mm buck driver we can find at the moment or is there any other choices?

I think everything else on the market in 17mm is pretty low current (as if we didn’t already consider 2A low).

I don’t expect these drivers come with high current draw ability, but can they be modded (resistor) and handle current at about 5A?

Definitely not 5A from either driver. The AX2002 won’t get close. I’m not sure what can be done with the SF driver, but I doubt that more than 3A is a good idea for the small inductor.

Well, it looks like one of the two I had (the one pictured in Anyone worked with either of these drivers from Lightmalls?) just went up in a blaze of glory :)….

I had put that one driver into a C3 awhile ago, and was messing with it today, and was trying to get a picture take of measured tailcap current:

That was tailcap current with 2x14500 Efest batteries in series, so I guess about 48 watts?

We took too long getting that picture, mucking around with the phone camera, and then it got dimmer. After that, it was only one mode, and bright, but not super bright.

So, I took the light apart to do a post mortem, and found that the area around the one of the legs of one of the AOEC/A0EC chips had burnt.

I tried to see if I could desolder that chip off to replace it, since I have the new FETs, but ended up pulling the LED22A, the stacked resistors, and both of the AOEC/A0EC chips off, and it looks like the trace that was under the AOEC/A0EC that burnt was delaminated (pulled off of the board).

I’m still a little disappointed and surprised (I guess that some others won’t be) that this happened, because I’ve had the driver in the C3 for awhile now and have been using it on-and-off, not for any length of time, but in short spurts, and it seemed to be ok.

Even with the voltage sag under load, that sounds terrible (assuming you were driving an XM-L or XM-L2). 48W turns into what? 24W at the LED? 50% efficiency? A linear driver would have done just as well.

I’d say the entire PCB was probably saturated with heat since there must have been large losses in most/all power components. That specific trace may have been sinking heat from the FET, so it delaminated a little early due to being a little hotter than the rest of the PCB. Once it didn’t have the PCB to sink heat into it burned up once it was run for long enough in a single stretch.

Potting may or may not have saved it, but assuming what I said in the first paragraph is correct about efficiency this is just not the driver for the job. I’m just pulling a number out of a hat here, but I certainly wouldn’t want to push a buck driver below 70% efficiency.

Thank you all for the information. Looks like we still cannot find good buck driver at this size yet. :frowning: