So what started as a single modest project has turned into a bit of a project family for me. Regular work has slowed down so there’s plenty of time now.
I’m looking at somewhat standardizing a control package, which means microcontroller, current sense amplifier, error-amp and temperature sensor set up in a fairly repeatable/reusable configuration. To start, I like the three-setting “low/high/stupid” where “stupid” is basically the max that the LED or driver will sustain, temperature-limited by a sensor placed near the LED. Software of course is flexible, so additional modes are possible. The microcontroller is intentionally fairly minimalist so there aren’t extra lines for fancy stuff, but sufficient to integrate one channel of 10-bit current setting, battery monitoring, temperature monitoring, one regulator en/disable and an off-time-capacitor read for mode switching, plus EEPROM for persistent memory settings. Everything I care about is possible.
I’ll also see about building a FET tailswitch for efficiency, but that’s not immediately necessary.
For current drivers, I’m looking at 1S voltages for input and would start with 17mm size. Attempts will be made at:
2.5-3A buck (existing project)
6A buck
4-5A boost (6V)
8A boost (6V)
My cousin and his mechanic friends have requested a decent penlight so I’ll also be working on something there. I’ve got some samples of a buck/boost that’ll pretty fully utilize 2xAAA voltage range.
Found a decent dual-phase driver for the 6A buck which will take up a bit more board space for inductors, but the resulting drop in conduction losses and reduced input and output capacitance requirements should more than make up for it.
The 8A boost will be fun, if it’s even possible. I’m looking at using a non-exotic controller and external FETs for increased flexibility, better heat handling and easier sourcing of parts. Eats up more board space so it may not fit in a 17mm but I won’t find out until I try.