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

You definitely don’t want to take a big step like going half or double. I have only messed with sense resistors in linear and boost drivers, but not Buck. In just about all those instances slightly lowering the resistance saw a noticable increase in output.

This one driver had a 0.04 ohm sense total and put out 4.6A. Changing the value to 0.03 bumped up the current to 7A. So small resistor change equals big output change. It’s probably one of the reasons this driver uses two resistors in place of one bigger one. You can’t always get the exact value resistor that you need, so the manufacturer can use two different values combined to get just the right value.

Using one .360 and one .180 gets you .12 total. That’s a pretty big jump from .18
Maybe get a few .300 and .250 to go along with the .180 you have.

A .360 and .300 will get you .16
Two .300 will get you .15 (same as .360 and .250)
A .300 and .250 will get you .14
Two .250 will get you .13
A .360 and .180 will get you .12
A .300 and .180 will get you .11
A .250 and .180 will get you .10

Yeah, that should work. Buy some R300 and R250 in the correct package size and you can get whatever value you need.

hmm, okay seems like doing that will not damage the driver either. will order some R300-R250s today. thanks.

Have you already seen new Convoy’s boost driver? Looks like well designed driver.
https://www.aliexpress.com/item/4000046041955.html

  • 22mm diameter
  • 2.3A max. current
  • MP3431 boost IC
  • big-ass 1.5mH inductor
  • large MLCC bank on the ouptut

MP3431 is very powerful boost controller:

  • up to 16V output
  • up to 40W to the load
  • up to 13A input current (programmable)
  • in theory should provide 5A output current for 6V XHP50.2

Link to IC:
https://www.monolithicpower.com/en/mp3431.html

Looks like promise to even higher perfrmance than H2-A or H1-C. I’ve ordered some quantity and it will land on my test bench soon.

Considering the driver comes stock with R360s, swapping them with R300s nets you a 20% current increase. Using R250s means 44% increase. Its an inversely proportional thing. With R220s the increase is 63.63%, and +80% with R200s. You may want to also swap the smaller schottky diodes in such a case, and even add some extra output capacitance. Ask the experts LoL.

Suffice to say, at your own risk. O:)

So if he wants to go from 1.5A to 2.5A he needs about 65% increase. When you say “with R220s” you mean two in parallel which equals 0.11?
A .300 and a .180 would also work.

Hmm, just replacing one of the .360 with a .180 is pretty close at .12. That might work. Hopefully it won’t burn up. Lol

well, it does seem like it’s inversely proportional to that resistor. i found this pdf about the driver ic which is used. and it indicates same thing i guess same should apply for my driver too ? does this apply for all buck drivers ?

link to pdf


apart from those schottky diodes, anything else i need to change ? along with resistor ofc. hope it doesn’t burn, headlight costs 98$ lol

On my motorcycle, I just swapped in an aftermarket led bulb that gives me a stock cutoff pattern, but noticably brighter. Easy peasy. :stuck_out_tongue:

Wow that MP3431 datasheet shows 97% efficiency @1A which is around the current I need. Just need a driver with more evenly-spaced or configurable modes, and a ~3V cutoff voltage.

EDIT: Appears to be PWM not constant current :person_facepalming:

I thought that driver was 12v out only, not 6v.

Have you seen Loneoceans boost driver? He does not sell them, he just designed it and shows others how to assemble the parts.

What would prevent me of using ‘12V’ constant-current mode driver with 6V LED? :question:

NarsilM - Neolithic Advanced Research Superior Intelligent Light Module

Yea, right....

From the source code: "the sword wielded by Isildur that cut the One Ring from Sauron's hand"

Let me see, I started working as a programmer in 1979, also bought the very first IBM PC for my own home use about in '82 or so. Also in 1981, started doing my first consulting gig at $17/hour - hit the big time!

I should add that over these 40 years or so, I've done a ton of firmware projects, most or all where the firmware had no name, least that I can recall, because basically, hardware such as fault tolerant server, graphics controller, terminal, typesetting system, treadmill, or any other device I've written firmware for gets only one functional version of firmware and is an inherent part of the product. So for example I might have built in a feature in the treadmill firmware to pause/resume, but that's a feature of the mill and listed as so.

In this BLF/flashlight kind of environment though, a name or way of identifying it is more important since there are many choices. We could have gone by the author but that has it's problems and is not conducive to the open source, open nature of the forum here. Also could have used some acronym that stands for something clever, but no one will really remember or care anyway, so Narsil or NarsilM is about as good as anything. I followed TK's lead here for using names like this, and Anduril, of course, is the natural successor to Narsil. In fact as I recall, TK asked me privately if it was ok to use that name, and assured her it's no problem at all.

Just a little history here....

Yes JasonWW, Loneocean’s driver is a tease but I don’t have that kind of time. I’ll just stick with the H1-A mod until MTN has their BST series back in stock.

I accidentally broke my old one marked 2R2 and now I’m getting a 3% efficiency drop (92% to 89%) @1.25A with the new one marked 1R5. Well that kinda sucks.

As predicted.

It does not bode well, I wonder what would happen on high when sense resistor modified at 4+A.

Can you try replacing the inductor, to see if it restores the efficiency Nightsword?

Stuff like this sort of takes away my appetite for, honestly.

I still have the old driver with 2R2 inductor, but I absolutely won’t do anything that might damage the newly modified driver, because changing the resistor is a PITA. Let me know if there’s a sure way to replace the inductor. While at it, may as well go bigger than the 2R2.

Unsolder the current, solder the new/replacement one. This is easy. If you have some parts lying around, that is. I do, but guess I may be too far away. O:)

The solder joint near the resistors is risky for me. I’m going to skip this mod, use this H1-A as is for now, and then get a MTN BST driver when they’re in stock.

Doh!!!

Going from 92% to 89% efficiency would be a third more heat off the driver btw

i’m having strange issue with a buck driver, currently it’s having 3x 0.24 ohm current sense resistors which means output should be 2.5Amps right ? but it outputs more than 2.5A when i try to run 3x osrsm white flat + 1x Xml leds in series.

i’m powering the driver via motorcycle charging system ( driver is designed for it since it’s from motorcycle auxiliary light) , input and output current hovers around 1.3/1.5 amps when motorcycle is idle @ 13.2-13.8v, but as soon as i increase RPM, voltage goes upto 14.2v , and led driver outputs more than 2.5Amps and goes upto 3.2Amps to leds. i get that when input voltage is not sufficient the driver won’t output enough current to the leds, but when the input voltage is enough , it shouldn’t deliver more current than it’s supposed to, right ?

now here comes the strange part, when i remove 1 xml led from above arrangement and run only 3 white flat leds in series, everything behaves normally, output current never goes above 2.51Amps.


any idea why running 4 leds in series instead of 3 , increases driver output current ? btw driver is designed to be used in 9-36v range.
thanks .