LD-40! (17mm Buck driver, 3-16.8v!)

Flashlight Modding and DIY Parts
36

Thanks syracuse.

Magnetics, Inc. makes a special line of thin toroid cores. I wonder if replacing the stock inductor with one of those would suffice for P60 compatibility. Magnetics’ documentation is pretty comprehensive; if one is really inclined to try this they may just find one that will support the requisite flux without saturating.

37

Have you started testing it yet? And if so, do you have any data (Iin, Vin vs. Iemitter,Vemitter, etc.)?

38

Sorry, I have not done anything yet - very busy with my children and my work…
I’m planning to make some P60 copper pills to use with this driver and the BLF17DD.

!!

compared with LD33.

39

Thanks for the links, but when I click on the pics, it’s taking me to a page with bunch of links, rather than displaying the original pics.

40

I guess that:

- 8205S is a dual-channel N-channel MOSFET (6A/20V, Rds(on) 28mA, STT8205S_11 datasheet(1/4 Pages) SECOS | N-Channel Enhancement Mode Power MOSFET)

- 3912 is some kind of (schottky?, zener?) diode

41

Thanks for the pics comfychair.

Parts info:

  • The popular QX9920 buck controller as we’ve seen on a lot of controllers. Marked LEDA 1328.
  • Two tiny 8205S N-Channel FETs (with a ridiculous pinout, is that normal for the SOT-26-6 footprint?). This is probably the same FET configuration we see in the “new DRY” driver, the lightmalls driver, and probably others. Note that these FETs are not in parallel, the capacity cannot be added together.
  • IC marked 00VM - probably the modes chip. Also that’s probably a batch code or whatever, not the name of the IC.
  • R100 sense resistor
  • Diode marked 39 12 - I assume that this is a 3A diode.
  • As usual there is a zener present to support the QX9920, it’s next to the IC marked 00VM.

As pointed out by the IOS listing, this driver has no low voltage protection. Running 3s into an XM-L will let you pull the cells down to a very low voltage with a low current draw from the cells. I suspect that some protection circuits may not trip. (I’m a pessimist.)

This driver seems very similar to the Lightmalls one I linked above which ohaya has put a bunch of work into (component pics on second page).

42

It’s a Schottky diode. Did we ever identify AOEC / A0EC on the Lightmalls boards you have?

43

I don’t remember if we did definitively, but FYI, l have been successfully replacing those with 5amp alternates mentioned in the LM thread since awhile ago.

44

Whoopdy! My order with the LD-44/LD-40s should be arriving from CNQ this week some time (shipped 9/20)! Looking forward to comparing these to the LM ones, and maybe killing a few :)…

45

Tested one of these, hooked up to an XM-L2 on Noctigon on a heatsink. Input was my bench PSU.

Stock, it is outputting ~2.3 amps at the emitter (at ~3V Vemitter). This was even when I crank the Vbat (from the PSU to the driver) > 10V.

46

Thanks ohaya. Looks like the LD folks split the difference between Hank and Ric’s spec… :wink:

I wonder how/if the performance changes with higher output voltage? (MT-G2 or 2*XM-L2)

47

I have an mtg2. If you let me know what would be needed, I can try.

48

I’m also most interested in seeing if/how this can be tweaked to get higher current …

49

Also how does this one compare to the LM one other than no blinkies?

50

If you’ve got everything setup and easy to get to I’d just hookup the MT-G2 for a quick test of output current. I’m sure it’s probably fairly close to the 2.3A you’ve already observed though, so it’s not a big deal. If you wanted to take tons of measurements (I rarely want to do that, it’s just a matter of needing the data sometimes) you could get current in, current out, volts in, and volts out. All measured under load. That’s our standard data for doing efficiency calculations. I’m not asking for that myself, because I don’t think it will be anything impressive. Probably 80% stock and <70% with a resistor mod. EDIT: in fact, I see little point in any of that testing. I’m pretty confident that we already know all of these answers. Don’t bother unless you get super bored! :slight_smile:

You increase current the same way it was done on your LM driver. Decrease resistance through the sense resistor. I assume I posted math over there in your thread somewhere, but it should be this:
Iout = 0.25/resistance

so for example the stock resistor gives us:
0.250 / 0.100 = 2.5 Amps (close enough)

I didn’t see any evidence that this driver was significantly different from the LM driver. Comfy’s pic is down right now, but the BOM looked very similar to the LM driver you photographed for us.

51

Efficiency aside, this driver seems to be more robust than the LM one.

The 8205s seems to be spec’ed for 4.8-6 amps , and so far I’ve tried stacking 1 R200 and also 2 R200, on top of the original R100, and got about 3.2 and 4.48 amps respectively.

52

I tend to be a pessimist. It’s rated at 4.8A @ 70°C under these conditions: “Surface mounted on 1in2 copper pad of FR4 board; t≦5 sec. 180°C/W when mounted on min. copper pad.”

I’d call that a “safe” 3A for our uses. I think that 5A will probably kill it inside a flashlight, but there’s only one way to find out for sure!

53

I have a host waiting for this I, but I’m think I’m already over my sitting time allotment for today :(….

54

Hi wight, is this always the case or is this calculation only applicable on LD-44?

I wonder why LD-44 has only 80% efficiency (I know it’s your “pessimistic” estimation lol)… is 80% efficiency considered good and normal for a buck driver? I thought buck driver should be quite efficient at about 88% especially it is a good quality driver apparently.

And thanks for the test and information ohaya. :slight_smile:

55

BTW, I think that with this (CNQ) driver, I hear whining, at least on medium mode, and possibly high (not sure).

That is one functional thing, aside from the no blinkies, that is different vs. the LM driver.