Test/Review of Led4power 5A linear driver LD-1 (prototype)

It was just the capacitor.

That can be discussed. The best way to find it is to look at the first curve with current, find the minimum voltage where the driver can sustain the 5A, the look at the "Driver" curve for the voltage drop across the driver at that voltage. I will say somewhere between 0.15 and 0.20 volt is minimum loss. This includes the (short and thick) wires I mounted on the driver:

It would be interesting for sure. We discussed how stacking/adding 7135's adds voltage drop because each 7135 adds to it, but think it was written off as being insignificant. I think comfy did a great job finding a low resistance FET we are using in the custom Atmel Tiny13A BLF boards, but that's of course is a DD design, using PWM's for lower modes. The popular boards right now for single cell use for us are:

  • Nanjg/Qlite (same design), w/optional stacking or an off board 7135 "farm" slave board
  • the BLF17DD, and other derivations
  • this LD-1 driver (will BE popular!)
  • the BLF15DD (similar to the BLF17DD but different small footprint FET)

Would be nice to know who they compare.

You can measure parasitic resistance of LD-1this way:

Use xm-l2 and set power supply voltage such that driver supplies 2A on high(or 3A,doesn't matter,it's only important that driver can't supply 5Amps to led,so you have kind of direct drive).Now measure voltage drop between mosfet drain(place where you solder - led wire) and gnd close to sense resistor. Parasitic resistace is Rpar=Vdrop/I.

You can also do that with other drivers.

I think it was written off because it’s not true… You are thinking of battery voltage sag, that happens more as you put them under a heavier load. [and batteries sagging under load clearly applies to all drivers] AFAIK Voltage drop is the same no matter how many 7135’s you put in parallel. That said, I hope we find voltage drop to be lower with the LD-1 than 7135 based boards.

Thanks, I guess that’s a straightforward application of Ohms Law but I would not have thought of it by myself. That seems much more useful than coming up with an arbitrary “this is the voltage drop” figure. I guess it’s not that simple when it comes to switching drivers such as buck designs? Can we assume Rpar=Vdrop/I to be true basically anytime Iin = Iout?

wight - yes, you are right about the 7135's! My freshly charged KK cells in the HD2010 can't get to 5A, the older ones are hitting ~4.25A, and newer ones maybe ~4.5A or so. I'm thinking/speculating the LD-1 might be higher resitance than a maxed out Nanjg/Qlite. I see O-L just posted a HD2010 for sale with a 16x7135 Qlite driver, so it's at least 5.8A configured - wonder if he had any cell that could achieve the max. The max I measured on the LD-1 was 5.35A with turbo enabled, using a fresh charged LG HE2 and 20 AWG LED wires.

Sorry if this was already mentioned somewhere, but can this driver run 3 x XML in parallel @4 or 5A each? Or would it be something like 5A/3 = 1.6A each?

It would be 1.6-1.7A each - the driver won't know there are 3 LED's out there in parallel, just that it restricts output to 5A, unless you have turbo enabled of course. He's got turbo working like DD.

I’m not sure if this is what you were asking, but it definitely can’t do that in the stock configuration. The stock configuration certainly won’t do 12A or 15A (what you asked about). It would be the 5A/3 = xx each.

Oh well. Thanks from the quick replies.

Why do you ask?

Just a few ideas I had mulling around. I use a modded SRK for a bike light with a 24 x 18650 parallel remote pack. While it does a fantastic job as a bike light that runs continuously without voltage sag, the idea of having the greater efficiency of CC in the lower modes would justify the mod. Ive also thought about hacking apart the SRK, then mounting a large CPU heat sink on the back of the emitter mounting plate so it could run at higher sustained amps. The driver would then be remote mounted on its own sink. I also thought about asking if 2 slaves could operate off one master driver, but at that point it would be hard to justify. Ive already considered vF matching the emitters if necessary. (I have at least 75 L2’s on noctigons so its not a concern) lol

I thought you might say something like that. Why not simply wire them in series and use a buck driver?

For safety and versatility. Its soldered 4.2V and I use it to power many other devices. I have no ambition to build a large capacity serial pack, deal with balance charging and then hang it under my seat. Especially considering the high G-shock it is constantly subjected to.

I’m curious what other devices you run off of this monster pack?

Turbo is theoretically cca 10Amps but it's designed only for single xm-l2 or xp-g2.Don't drive triples with turbo!

If you want to get 15Amps,you'll need external mosfet and sense resistor,it's possible.

You need two 10mohm sense resistors+one mosfet(I recommend you nxp psmnXXX series with maybe little lower resistance than stock).Those can should be mounted on separate pcb and heatsinked.Connect them in series with led and power supply(thick wires).On driver you need to remove sense resistor,and bring sense voltage from new (2x10mohm) sense resistors;connect gate pin on driver to gate of external mosfet,and connect driver to + battery voltage(all thin wires).I'll post schematic later.

This was already a great driver. Now you have really made this into a must have if you can achieve 15 amps for 3 XMLs or 3 XPLs.

Thank you for giving this some serious thought. Im not sure if I could fab my own. Being able to supply 3 emitters @5A each + CC would be extremely useful for many of us. Once you finalize the design of your single version, could you please consider building a triple version? I think you’d sell many of them. This is starting to get very exciting! :bigsmile:

Just a heads up. I sent a BLF17DD driver to HKJ this morning. After he has tome to test it yall will have all the graphs in the world to look at :-)

Ahh, cool! Thanx LedSmoke!!

I am already drooling at the thought of using this for a tripple/quad xpl