That’s really impressive, it means 50W output would be relatively easy right down to 3V, which in turns means 4000+ OTF lumens whatever the battery level on a single 18650 with the right led configuration.
That’s better than any production light I know of 
if it ends up being produced I’ll definitely have to get one.
I am so excited about Schoki’s Boost driver I can hardly contain myself.
I have actually been collecting parts and am now starting to look for hosts for this driver. These will be the first real lights I have built in almost a year, there was just nothing to significantly upgrade from what I had before.
Now I have plans to rebuild most of my collection around these drivers. The XHP35 is better then the XP-L or L2 in every way, more lumens, more throw, no tint shift. Then you have the xhp50.2 and xhp70.2 for some big flooder fun.
I have almost talked Schoki into letting me beta test some of these drivers…
I’d be happy to beta test as well if more testers are wanted. No problem paying for any prototype hardware.
This will indeed be awesome!
I have some question about further development of the Schoki’s driver….
1. We’ve seen GXB20 being optimized for 6V out. Lone oceans said that the driver would do 12V, but for optimal efficiency some components would have to be tweaked. Are there tweaks left to make the driver more efficient at certain output voltages?
2. How about low-profile inductors? Could they work sensibly with this driver?
3. Is there any component on the driver that supports temperature readout or are we back to the world of turbo timers?
1. If you have the driver configured to 6V, and you use the right parts from the beginning (with the output caps being able to handle >=20V), then you need to change two small resistors and the inductor to convert it from 6V to 12V.
The other way around, change the two small resistors and the inductor again.
To be honest, both inductor values work with both voltages, but the higher value inductor has a higher resistance, so it runs hotter. So just change the inductor for better efficiency.
2. Didn’t search specifically for low profile alternatives, but the XAL7030 is a lower profile version of the current inductor I’m using (XAL7070). 6V operation only then! Didn’t calculate ripple, but 1.5uH should do it (a bit lower than XAL707 with 1.8uH)
3. The MCU has a temperature readout. It is on the other side of the board, so we will have to set the maximum temperature lower. If that fails, the boost IC shuts off at 150°C.
That’s better than I expected, thank you. 
Question…Lexel improved heat path from inductor and controller. Maybe it would be useful to review thermal path of the MCU as well?
No worries, the thermal connection of the MCU is pretty good. I made some new revisions of my board to make the heat path better. The board you can see in the thread was made to get a working board as fast as possible.
And remember, if the inductor and boost IC heat up, pretty much the whole board heats up, since those two parts cover a lot of surface area. And a 17mm diameter PCB is pretty small. So when those two parts heat up, every other part gets hot as well. And half of the MCU is directly under the inductor (and it’s a 4 layer board).
Yeah one internal layer connects the BUCK controller to the whole board size
So far no BLF firmware supports external NTC to get more accurate temperature reading
Great job guys. I will buy several of these.
Just a suggestion: If you do not need all pins of the MCU (and you find the space), could you please prepare external pads for those? Maybe with traces to GND that can be cut when needed.
Yes, no firmware today supports NTCs but this may change quickly once they become more common, as on led4power’s boards.
There is literally no space to add such pads you suggest, but the pads of the MCU are wide enough you can solder very thin leads to them
The parts next to the MCU seem wider than the other, but in fact they are normal spaced and the others extremly close together
Pin 5 and 6 usually in 8 pin package are available as solder pads next to the ground ring
You can solder small leads on the pads, you just need patience, and a fine solder iron tip. I mean really fine. Best you hold the leads down with some scotch tape while you solder them on. And watch out to put no force on the leads, or they could lift the whole pad.
Yeah, that is why I hoped you find some space on the larger boards. It would make my life easier.
I doubt we will see widspread use of NTC’s until we move to a more modern MCU with more pins. Like the 1616 or 1617. When we move to those, then lots of doors open.
Also, we are out of space on the tiny25 for anything else anyways, so it sure won’t be added to that.
a NTC could be added to one of the programming pads for sure if vias gets added or drilled
adding a ground pad for it as well should be no problem next to the inductor
So let’s say we build a XHP35 triple in a S2+ shorty using these drivers. 6A at 12V gives us… 3x 2A per XHP35 so that would be 3x 2200 lumens for around 6600 lumens. Not too shabby 
For about half a second before your LEDs reach 200 degrees and start melting.
With 12V LEDs, maximum current is around 3A, not 6A. For 6V LEDs, then the maximum output is roughly 6V.
What I’m really looking forward to is efficiency on the medium modes combined with a good UI. A quad 9050 219C can do around 800 led lumen at 6W, if the driver is efficient enough I think something like 600 lumen OTF for 2 hours should be easily doable with a single 18650. That combined with bistro and the option of doing 30W bursts on any battery level, all in a very compact light, would be amazing.
Do we have any estimate for how efficient it will be at around 10W ?