Buck and Boost Drivers, Testing, Modding, and Discussion (Pic Heavy)

When I was testing the H1-A using a power supply it ran all the way down to 2.4v before it shut off, so I would say your fine.

Thanks for the reply, moderator007. I have an H1-A already modified for 4.5A output. Based on jensen567's 2.82A measured stock output, I consider this to be around the maximum effective current this driver can output at 2S XHP50A voltage (≈4.23A effective). Right now I'm just wondering if I should bypass the reverse polarity protection transistor, to help with TPS61088's cooling.

Cheers ^:)

Did the thing survived for long?

I am wondering…

… if sticking on the inductor case atop the boost IC would somewhat help with cooling, it is an easy thing to do just by desoldering its terminals, putting a dab of thermal paste/glue on top of the TPS61088, setting the thing on top and resoldering. Well, maybe a copper shim would be required.

Cheers :-)

The one thing you could do is stick a very small thermal adhesive dab on it, and then put a small copper shim on it.

Would help a lot.

Hi fellows! Just had a mishap while setting up one of my H1-As, shattered capacitor C11, the one attached to MCU's pin 8. Lost one of its leads. I've sort of managed to have a readout of its capacity with my multimeter, got from 25 to close to 33nF max. If someone is able to tell me what could be its capacitance value and post it here, that would be of help. I've tried to measure it over the glue on a spare driver but the measurement bounces up and down without end. Thanks.

Cheers ^:)

Mmm, just found something interesting in the newer Kaidomain H1-A drivers, there's no need to modify the output voltage divider for 3/4S emitters:

Looks like you can even drive XHP35s as it comes now, although in such a case I'd limit the current output to no more than 2A at most. That would already be ≈27.5W of power to the emitter, and driver's efficiency when boosting 3.x volts to nearly 14V is probably going to suck a bit, thus watch out for driver's temperature. With stock R025 output is 3A, swap it for an R050 for 1.5A max. R050 + R200 is 1.875A (75mV sense voltage).

Cheers :-)


After lowering the R11/R12 low voltage protection divider to 2.625V by stacking a 300KΩ resistor on top of R11, I noticed no usual low voltage warning in my modified SK98, at some point its output started to twitch and wouldn't change to the higher modes. I guess this is because the micro controller unit cannot work well with such a low battery voltage since it is fed via 2.8V LDO1. :-)

Measured cell voltage 2.72 - 2.73V once I arrived home, so it sort :-D of works LoL.

Cheers ^:)

turning on boost driver without load is no good idea imo


Well, at least that served to prove the H1-A can handle 4S emitters.

Cheers :-)

According to the datasheet from Ti TPS61088, it has a output overvoltage protection, that kicks in at 13.2V typ, 13.6V max.
The “no-load” readout of 14.66v is maybe just a generated high frequency noise??

I do not believe the multimeter is being mislead by high frequency noise, too high frequency.

I may try some load resistors to verify the maximum output voltage figure sometime later.

Cheers ^:)

Because if there is no overvoltage protection, it will try to manage current according to pre-set mode.
It proves nothing. You will probably get moon mode on with 4s, but nothing comparable with listed output current.

I would like to ask how far we from a BLF Boost driver? I know there is the GXB172 and Lexel is working on one but nothing ready to buy as far as i know.

And can someone recommend a Buck driver (2S clicky 22mm driver for Jaxman X1 flood host) for the 3V LUXEON MZ?
Or would it be better to remove the Extension tube and go with Lexels FET driver / Led4Powers driver?
I would prefer the Buck version because of the extra batterie capacity (@+12A even the Shockli 5500 are drained fast).

Richard a Mountain Electronics has already released his 17 mm boost driver and plans to release larger sizes with more power soon. We don’t know exactly when.

My SK98's cut-off voltage is definitively set too low at 2.625V, after a second test it completely blacked out in low mode. The onboard XC6221 voltage regulator's minimum drop is 80mV, this means the PIC12F683 is Vin sensitive. This is all guesswork and I just share this here in case someone can confirm these microcontrollers are expected to be so low input voltage picky.

The above black out was caused by a failing switch.

Cheers ^:)

Tue, 10/02/2018 - 01:21

My SK98 started misbehaving, random flickering and it ended up turning off. I took the time to dismantle the whole driver thing to check contacts, some caps I had replaced were refitted and replaced again, redid wrecked spring bypass, increased driving current a bit, etc. Started working again but soon failed once more, random flickering and strange behaviours like low battery warnings and other moon output periodic flickerings. Refitted the low voltage warning divider which was giving me strange readings on my modified R11, reverted it to stock (R11 = R12 = 100KΩ). Still no dice. I wonder what could went wrong, maybe capacitor C15 broke? C15 is in parallel with R12, at the low input voltage divider. Hope someone can help if not what a pity.

Cheers ^:)

Switches. Switches crapping out, and I had unnecessarily messed with the whole driver.

After replacing the tail switch once more, took the stuff for a walk. Started giving me early current tapering and low voltage warnings, previously noticed with multimeter in amperimeter mode tailcap readings for the sake of it. Today I checked the R11/R12 divider, the R11 value leaned to ≈40K for some reason, for a cut-off at 3.75V or slightly above (cells were reading ≈3.8V pulled out from the flashlight after low voltage warnings). This means the divider works inversely as I had thought. If someone could confirm this I'd be grateful, so much tail switch crapping out got me nuts. :facepalm:

Next is managing to make a MOSFET tail switch for this build.

Cheers ^:)

this will reduce output of max mode only or all modes proportionally?

mobydimk, swapping the sense resistor value changes all modes proportionally.

Cheers :-)

After a lot of driver messing I recognized an unseen tiny debris short-circuit between C15's body and terminals, the capacitor next and in parallel to R12. That was the cause for the random/instant low voltage warnings. :facepalm:

R11/R12 divider works as it was supposed, thus R11<R12 for lower than 3V cut-off.

My SK98 works. Thank God.

Cheers :-)