[[ GXB20 Driver – Homemade Constant Current Programmable XHP50 Single-Cell Boost Driver! ]]

Thank you for the tests!

There are many flashlights with soft button.Typical size of driver is from 18.5mm to 21mm.One of popular hosts is skilhunt H03
Its a bit hard to disassemble because it is sealed with thread. Or H02 it have very convenient construction for modification.

Those efficiency number is impressive
Thank you for your test and a great tools you have there :slight_smile:

Some updates for the week!

To summarize, I finally finished a 'beta' version of the firmware, put it inside the host, and now have a single 18650 XHP50 flashlight producing 1700+ lumens of 4000K CRI90 light!

Firmware Work

I spent about an hour or so yesterday and tidied up the basic functionality of the firmware (currently v0.6). It has all the basic functionality - 4 modes at 60mA, 540mA, 1800mA and 3000mA. Using the G2-bin LED I'm using, this corresponds to around 35 lumens, 310 lumens, 1000 lumens and 1750 lumens from the emitter. Keep in mind that if the most efficient bin was used (J4), a whopping 2500 lumens is possible!

The brightness levels chosen was somewhat arbitrary with no specific reason. Mode change goes from level 1 -> 2 -> 3 -> Brightest, with memory mode tested and working. Low battery cut-off was also tested and working. Thermal cut-off was difficult to test, but I did at least verify that it was reading the right temperatures. Clearly more robust testing is required later, but for my own 'demo' torch, this should do.

Obviously a lot more testing is required before I would consider a firmware stable, hence it's now labeled as v0.6 instead of 1.0

Assembly

With the beta firmware done, I loaded it up to the LED driver, then removed the programming header and prepared it for mounting.

As recommended, I also did a spring bypass with teflon coated stranded wire. Above shows the logic/driver side.

And here's a photo of the 'power' side with all the power electronic components.

As some of you may remember, I was doing testing with a G2-bin XHP50 LED with 90CRI and 5700K temperature. I wanted something a little warmer so I opted for a 90CRI G2-bin 4000K XHP50 instead. This time I had some proper heatsinks (from the recommendation of many members here), so I reflowed the 4000K LED onto it - this will go into my flashlight.

This was then fitted into the housing and thermal paste applied between the LED-sinkpad and the housing.

The wires were trimmed and soldered down.

And finally it was assembled into the host! It looks just like the original... but actually contains a light monster!

Above you can see it sitting beside the older XHP50 (5700k) mounted on heatsink, which I used for testing.

The project is done!

Comparison Shots

So how does it compare? Let's take a look at some beam shots. In order to compare, I set my camera to have a fixed manual exposure of 1/60s, ISO 400, W/B 4500K, f3.2. I compared the new XHP50 flashlight with the following:

1) 3000K 800 lumen Greenlite LED bulb (8.4W measured)
2) 5000K 1700 lumen CREE LED bulb (2016 version) (15W)
3) SK68-3W - cheap AA LED flashlight - 1.28V at 2.00A via Eneloop HR-3UTG (2.56W measured)
4) SK98 stock with LatticeBright 6500k+? (6.74W measured)
5) SK98 replaced with Cree XML2 80CRI 3000K (6.67W measured)
6) SK98 with GXB20 with Cree XHP50 90CRI 4000K (22W measured)

All 18650 batteries used in the SK98 Ultrafire host were the venerable LGDBHE21865 high discharge cells.

The above photo shows the unedited images with (1) on the top left and (6) at the bottom right. The result speaks for itself I think! It's extremely bright! Also, I specifically under-exposed as much as I could to (a) retain luminosity data and not blow highlights and (b) since I expect myself to make more, brighter lights in the future!

And finally, with the lenses zoomed all the way in to give an idea of the 'throw':

From left to right:

  1. LED AA flashlight (no idea what's inside)
  2. Lattice-bright XML-copy LED in SK98
  3. Cree XML2 in SK98
  4. Cree XHP50.1 in SK98

I think it's pretty clear that the Lattice Bright LED does have a smaller die and different phosphor coating than the XML2, and again from the XHP50 which has 4-dies. Hopefully the XHP50.2 will improve the cross pattern. Regardless, I think it's a pretty interesting pattern (which only really becomes annoying at max zoom), so I don't really mind it at all given how much light it provides!

So overall I think this project is a success! Thanks again for reading and following my little project!

Next step is to refine the firmware, do additional testing and see how it does in the real world, and then perhaps start on the GXB17...

[Edit] - Did a little bit of real world testing of the firmware and it appears that thermal management is working as intended :)

I am very impressed and if you should decide to brings these to market I’d certainly be interested in at least 4-5 of these drivers.
Just start a thread or continuance here maybe and post a notice and I’ll be there, thanks for sharing your project it’s fantastic.
Edit: Maybe an interest list would give you an idea of what might be possible and needed for your parts etc.

Wow, very nice!

Very impressive and very well spaced modes. Congratulations!!

I love it when a plan comes together

Well done, loneoceans! It’s great to see some real-world test results. Now only to… (1) find a way to make a 17mm version, and (2) find a manufacturer to produce them on your behalf, to your exact specs :slight_smile:

Why not create an Oshpark project?

:slight_smile: :+1:

Very nice!
How about an additional moonlight mode? How low can this driver go (without flickering)?

Awesome job!!

I want one! Maybe more than one depending on price. :sunglasses:

Sounds like this is what I need for the Nichia 144A’s I bought from Clemence/TA being able to use a single cell. Nice job loneoceans

From wo to go you have amazed. What an effort. :beer:

Simon, are you reading? :crown:

In all greatness, nice to see someone driver design knowledgeable with the same spirit as me (efficient boost & buck drivers).

SK98, nice choice; pretty popular. I see you've managed to fit that into its short shelf.

May sound a tad weird but, would it be more or less easy-feasible to turn it into a boost/buck engine for 2S input? I mean, compatible with 2S li-ion input for bigger torches, even if it means the driver has to grow a bit.

Cheers ^:)

Buck drivers already exist (mtn electronics has one). The Boosting at high current is what makes this new driver interesting.

Can you change the boost voltage up to 12V
For driving xhp35 led

A buck driver cannot regulate an emitter over the full battery input voltage range if it falls below what the emitter needs plus overhead, The_Driver. Also, a boost + buck engine could be made with a wide output voltage range and, with a few board/programming changes, allow for the desired input voltage cutoff (2.75V, 5.6V, custom values for different chemistries, etc) for over-discharge protection. Sort of a high efficiency universal driver.

Cheers ^:)

Recently I saw a 20mm 3A boost driver for 6V leds on kaidomain

http://kaidomain.com/p/S026606.H1-A-20mm-3A-1-cell-5-Mode-Boost-Driver-Circuit-Board-for-Cree-XHP50-6V-MT-G2-MK-R2

Looks promising to me!

Interesting find!

I’d still love to see the GXB20/17 come alive, especially when it comes with the possibility to use an electronic switch.