Looking good! The 20mm version would be perfect to put into a Convoy L2 with short battery tube.
Laying out the board on 4 layers would certainly not only allow better performance but also allow better routing. However specifically avoided a 4 layer stack to keep the PCB costs as low as possible. Adding blind or buried vias significantly increases cost so I usually try to avoid them as much as possible. I'll explore a little with the 17mm version when I have time though it looks to me that there should be no problems making a 2-layer 17mm version.
I didn't bother fabricating a stencil for this since I was expecting to only make a very small number of boards, so I soldered them all by hand with a combination of reflow and solder paste applied by hand using a toothpick (typically I don't get any bridges if the right amount of paste is used, or I fix it using solderwick), and solder the rest by hand under magnification with a tiny tip soldering iron. Like you mentioned soldermask expansion needs to be adjusted. I think I used 1 or 2mil expansion, depending on the fab I go with.
“Improved lowest level of CC brightness (just around 1mA - true ‘firefly’ mode)
Modes for my own firmware: 1 = firefly <1mA, 2 = low ~180mA, 3 = mid ~600mA, 4 = ~1.8A (~1000 lumens), 5 = 3A (turbo)
Measured efficiency of 92% at 3A (~6.5V) output”
Can this driver correctly work with triple LEDs, 8-9V ?
17mm 9V/1A for 219C triple will be very interesting driver.
(and <=5mm height, for E2L host)
Yes it will work just fine with some small adjustments (e.g. to make sure it doesn't try to drive 9V at 3A, adjust components to make it more efficient st the desired drive currents etc).
3A - huge overload for N219C (with serial connection), ~1-1.3A current in (turbo) mode will be nice.
Wanted 17mm (and 5mm height) driver .
fine modes may be, for example :
1 = firefly 1mA,
2 = low ~30-40mA,
3 = mid ~100-130mA,
4 = high ~400mA,
5 = turbo ~1-1.3A
3A is a huge overload for the 219C???
I have run them up to 12A and they still worked fine. Check my sig for a test of them, they didn’t even reach peak lumens until ~6A. Although around 4-5A is ideal IMO.
thanks, but I tell about triple of 219C with serial connection, for every-day usage (not about 1-time tests).
And, for serial connection, 3x219C & 1A will require 8-9W, for 3A it will be ~27Watts of power, and ~36-38W for 4A.
30-35W in small case - overheat in few seconds.
Ok, so you are saying that 3A is too much for the host, not for the 219C LED’s themselves. That makes more sense.
Besides heat from the LEDs, running at 3A at 9V output is also impractical from a single 18650 cell drive in most flashlights as well. The 27W output will require at least 30W input or more, which for most 18650 cells will require about >=10A input current which will be just about too much for the driver to handle safely. Contact and switch resistance will also lead to significant losses. However, 9V at 2A or so is completely OK (at least for the GXB20) :)
loneoceans, when you plan to produce 17mm drivers ?
I didn’t see this in the OP. Curious what are the limits of this driver when it comes to power. I assume that the true limits lie in the input current?
I assume this could boost power to an 12v XHP35 as well with some component changes, what kind of output current would be possible?
Also, did you ever say what components you are using for this driver? I never saw a parts list, curious what boost IC you are using along with the rest of the parts.
If this could be shrunk to 17mm an xhp35 S2+ could be a really interesting EDC light (or xhp50.2 for that matter).
A TPS61088 is used as the boost converter, here is the website, even with a schematic: loneoceans labs | GXB20 v1 LED Driver PCB
I currently try to get it shrunk to 17mm (with a few modifications to the circuit).
Very soon! Layout for GXB17 is basically done. Just need to order a few PCBs and to fine tune everything (render above is not final yet, was taken during initial design). The hardest part is designing within the 6/6mil constraints of OSHpark and using 2 layers with no air-wires, though I've fabricated 5/5mil with them and they seem.. just fine. I suspect even 4/4mill will still be OK!
There are several aspects to the limits, but not hitting on the more nuanced ones would be the maximum input current of 10A. In addition, making the driver efficient at different output / input voltages requires fine-tuning the component choices such as the switch frequency, inductor and error compensation network - i.e. one cannot just run the driver for a different output configuration while expecting similarly high-efficiency output. However, if one is willing to sacrifice a bit of performance, then changing it should be fairly straightforward.
I'm still in the process of writing up a page for it but my 'sales' page has a decent overview of the BOM and Schematics. http://loneoceans.com/labs/sales/gxb20v1/ Note the V2 version is fairly different with some enhancements.
Finally there are obviously other limits to the other components such as minimum voltage input required for proper operation, thermals (getting pretty warm already at ~18W output) as well as boost inductor. Trade-offs I suppose between cost, size, efficiency, performance and features :)
Thanks for the link, I didn’t see that before.
So it is setup for a 7A input, thats pretty darn good. What is the limiting factor? I see the inductor is rated at 11A but didn’t take the time to look up everything else.
With a 7A input limit, that would be around 1.75-2A to an xhp35, which is pretty darn good. If it could drive it a bit harder to 2.25 - 2.5A it would be perfect.
I think one limiting factor is power dissipation. Even if the converter maybe has ~90% efficiency at 25W of power, it still gets pretty hot.
Yeah, heat buildup should be the limiting factor, the question is which component? If you stuck the driver with thermal cubes you can usually get some more out of it if you know where the heat is coming from.
It’s either the coil or the converter itself. It’s difficult to say because the converter works a little different and has like a “built-in diode”. The diode is replaced with a mosfet controlled by a deadtime
control logic.
It’s really annoying that I spent all the time fiddling around with the 17mm board (probably finished by tomorrow), but loneoceans did it already :person_facepalming: .
I hope my version isn’t completely wasted time 
Very interesting, that is a nice IC. I was curious why I didn’t see a diode listed in the parts list.
Or triple xhp35.
Though my dream would be this driver on a 20mm DTP PCB. With a series od 3 XP-L2s on the same board.