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).
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.
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.
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
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 ?