LED drivers and Accessories you want, but don’t exist

Of course. You’re speaking about an 18W driver vs a 50W driver.

Extremely amazing when you think about it. A 17mm 50W boost driver is unprecedented in the industry.

Hello guys,

Please excuse me for joining this conversation, as I am a newbie in regard of the flashlight electronics topic, but I have a (general) problem, for which I think, a solution would be highly desired, as success in that regard could be perceived as a big improvement for many of us. (Also excuse me for introducing a problem, which does not match the concept of your latest conversation.)

I have read about the linear drivers across some pages and forum topics, which are used pretty much all across the baseline of Convoy products (S2+, C8), and many more similar flashlights.

Because mostly there is a significant difference between emitter Vf values (for given current), and battery voltages, they just convert the difference to heat, which leads to undesired efficiency loss, and worse heat attributes for given current levels.

I was lucky enough to make a few emitter swaps in my favourite headlamp model (Skilhunt H03), and I discovered, that heat is pretty much controlled with even the two highest output settings. I have read, that it has a driver, which converts the battery input voltage down to the Vf of the used LED (certainly, it has a buck driver), so it could stay fairly efficient, regardless the fact, that I used an emitter with considerably lower Vf across its current characteristics (change was from Cree XM-L2 to Nichia E21A).

But, that is not the case with any of the known linear drivers - so using lower Vf emitters with those drivers could mean even more heat compared to the older XM-L2 or XPL emitters, if they are used at the same current. (These emitters would be most new Cree whites, almost all Nichias, many of the monochromes /extremely low for mostly orange, red, and near infrared/ for signaling purposes) - Also, I would not like to direct drive these low Vf emitters.

Generally, I would like to ask for a solution, which could be used in a few smaller popular flashlight hosts, which can only support d = 17 mm driver plates (e.g. Convoy S2, Jaxman E2L), and probably they have limited space to fill vertically (e.g. it would be around <5mm for both of Convoy S2 and Jaxman E2L, if I remember it right).

So, for now, my question would be, that could you design a single li-ion battery buck driver for a d = 17 mm driver plate, or it has too many difficulties? (‘Moderate-to-high’ max. current, e.g. 2-3A for S2+, 4-6A for C8)

If at least one of you would like to, and would be able to put some effort into it, I am willing to donate for its development based on the needed parts list, and other factors/milestones. (I cannot offer more than a few $10, but I hope, others could join the funding of this project as well, if it can start.)

With a little exaggeration, my dream would come true, if I could use nearly any emitters efficiently and with controlled current levels with the above mentioned flashlight hosts (and it could be widely available across the flashlight users/lovers, then).

17mm buck drivers exist in plenty of flavors already.

The problem? Since buck drivers have much higher resistance than FET and linear drivers, in a 1x18650 setup, they go out of regulation quite quickly except if you have a very low forward voltage emitter(E21A quad).

For example, imagine you have a 3.2V forward voltage emitter at 3A. A linear driver will keep constant brightness until the cell goes down to 3.3V. It is less efficient than a buck or a boost, but will keep brightness constant at all times.

Usually, unless you have a very expensive buck, there will be a room of 0.5V to stay in regulation. That means you would fall out of regulation at 3,7V, much sooner than the linear regulator. It is much more efficient though at 3.8-4.2V however.

The easy way to get perfectly regulated brightness, but then, you would need a 2S setup, meaning you would have a light twice as long.

TLDR: Unless you have very low forward voltage LEDs, the best drivers for 1x18650 lights are boost, linear, and the Holy grail, the buck boost.

adam7027. What you are wanting is a buck or boost driver like we have been talking about. These are fairly easy for low currents but get exponentially harder as power goes up.

Also, while the linear drivers are less efficient at low modes then a buck/boost driver, it is usually not enough that you would notice it besides a bit less battery life. It is not enough to make the light noticeably hotter to the hand anyways from just an emitter swap.

As the improved efficiency of the emitter makes up for the worse efficiency of the driver, so the final output is basically the same. You just don’t gain efficiency that you could from the lower Vf LED.

In my testing of linear / PWM drivers, even at 50% duty they were still close to 90% efficient, which is about what you can expect for a buck/boost driver. Only in modes lower then that will there be a noticeable different in efficiency.

Although the linear driver gets more efficient as the voltage drops. So in the long run the final outcome is not nearly as bad as it sounds on paper except for some special use cases (very long term use at very low modes for example, where you battery life is measured in days).

Edit: Bluesword beat me to it.

Pretty sure the LED4Power offerings are pretty close to what he wants already.

Thank you all for your helpful answers.



Good to know about the higher resistance, I didn't consider that. Still, if you know premium single cell buck or buck-boost drivers for d = 17mm, I would happily take a look at them. There is a chance, that in some less frequent cases, I would like to use emitters comparable to E21A quad, regarding the Vf (e.g some monochrome reds are of much lower Vf starting around less than 2.5V).

I also noticed the small room for regulated output with the stock Skilhunt H03. It 'lost' its highest setting around 3.8V, while with the E21A quad, it could go down to 3.3V with a plain old Pana NCR18650B for the same effect. Something approximately as good as that driver could be good for me.

Otherwise, if I'd use a linear driver, maybe then it would be better to use some mid-current, capacity optimized cells to make the difference a bit less, and their discharge slope also gets less steeper at the second half of the discharge.




For what current level would you consider a buck (or buck-boost) driver to be fairly easily made?

I found somewhere a driver, which could fit most of my use cases /no blinkies, more modes relatively close to each other in the midrange - I planned to use it with 4-5 pcs of 7135 regulator/, but I found a review, which had discouraging results for me. Based on the fact, that it was made with a Cree XP-G2 emitter, I only expect worse result with e.g. Nichia 219C or 319A - that was the main reason for me to ask for help.

Are there 'good' and 'bad' (i.e. with significant difference) linear drivers, according to your tests?




Thank you, I already looked at that specific driver, just hoped for other solutions as well.

But the fact, that it 'renders' all modes without PWM, could be good.

Buck/boost drivers are reasonably simple to make with up to ~2-3A max on either the input or output, whichever is higher. Once you go much above that it gets exponentially harder to keep everything in check.

The 7135 drivers are fine for what they are, basic and cheap but they do the job.

Just listed Emitters, pads, heat sinks but need driver for

WTS Once in a life time 95CRI 3000K massive emitters

Someone please let me know that we can at least build single mode drivers!! Please

I pointed you at the MIC2298 in that thread, maybe someone here can take a look, see if it’s feasible.

Here’s Arduino firmware that can turn it to avrdude-compatible ATTiny1616 programmer:

How about a buck driver that fits an L6, with narsil, and 12v 2.5a output. I’d love to build one with an xhp35hi. I would be happy to use 4 x 26350 in it. Slightly more reflector over the l2 version and ramping fw. I would hope for a bit better throw over the l2 for that reason.

I was thinking zener modding a fet setup, to get the input side sorted, but i have no idea how i’d regulate it to keep the led at 2.5a. Buck seems like a better plan, but i don’t see them done on that platform.

You are thinking of a boost driver to do that and yes, I have also thought of the same thing.

Boost on 2 26650s would be even better, but i’d be fine with either setup

From MtnE front page:

:slight_smile:
I wonder when there will be Narsil though.

guppy should be fine for clicky lights, at least we have more progress

I would also be interested in purchasing 17mm boost drivers. Maybe a few larger ones if 17 is not possible.

You will need to see Lexel about that. I just recently heard he got some help to get NarsilM working on his high powered boost drivers. No word on when they will be available, though. I hope soon.

Iirc, Richard doesn’t use NarsilM. He may adapt RampingIOS (the D4 UI) to work later on, though.

To show I’m working on it:

So, do we need to take up a collection for you guys? I’d be happy to throw in a couple bucks to push the boost driver forward. I figure there are others who would do the same.