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

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texas shooter
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Nice work, thanks for sharing. Sitting under a hot LED encased in a host with no air flow. I think drivers bleeding out that much heat might need potting. A few good materials out there should nip frying in the bud.

loneoceans
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DavidEF wrote:
Rufusbduck wrote:
Any possibility of a parts kit with flashed mcu?
+1 _please!_

 

I bought a bunch of ATtiny84A MCUs :). Let me know if anyone is interested in a board with populated and programmed MCU (only MCU, you need to solder on the rest yourself)  :). The rest of the details and BOM can be found here: www.loneoceans.com/labs/sales/gxb20v1

www.loneoceans.com/labs/

- Next-gen Switching Drivers: Lume X1 and Lume1
- High Power Boost Drivers: GXB100 GAN 100W, GXB172 17mm 50W
- Older: GXF22, GFS16, GXB17 & GXB20

M4D M4X
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i am! Big Smile

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i do not work in "reviews, deals and codes" for the time being
maybe M4D M4X will return one day, but until then:

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Rufusbduck
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Yes please!

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

lovetheguitar
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Very interested too! Smile

TBone
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Sounds good. I am in for one.

mrheosuper
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if you could make 17mm version, i’m IN

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loneoceans
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So... I made a whole bunch of improvements to the GXB20 V1.. 

I just received the news PCBs for it... introducing the new GXB20 V2cool 

Still writing the (improved) firmware with a lot more additional and optional functionality, this time with 3 extra mode selection jumpers or E-switch control. And a complete layout redesign, on-board programming connection which will hopefully be a lot easier to use, and improved power electronics. 

More to come soon! Smile

www.loneoceans.com/labs/

- Next-gen Switching Drivers: Lume X1 and Lume1
- High Power Boost Drivers: GXB100 GAN 100W, GXB172 17mm 50W
- Older: GXF22, GFS16, GXB17 & GXB20

DavidEF
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V2 looks nice!

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texas shooter
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WOW very professionally built. Great looking with plenty of retaining ring clearance.

Mike C
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Different components used? Besides layout, any hardware changes that I can take when I eventually get around to building the previous versions I have?

loneoceans
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Mike C wrote:
Different components used? Besides layout, any hardware changes that I can take when I eventually get around to building the previous versions I have?

 

Hello, yes there were some slight changes in the feedback and digital potentiometer allowing for more variations in brightness. I also conducted some experiments in the power section but I don't think there are any hardware changes needed to be made so far (some changes I made resulted in same or slightly less efficient results so the original is good enough Smile )

www.loneoceans.com/labs/

- Next-gen Switching Drivers: Lume X1 and Lume1
- High Power Boost Drivers: GXB100 GAN 100W, GXB172 17mm 50W
- Older: GXF22, GFS16, GXB17 & GXB20

loneoceans
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Another quick update and thanks again to everyone who's been following this project! 

GXB20 Version 2

In short, the changes I've made for the V2 version turned out to be an improvement over the original by a small amount, and after a little more testing I think I'm happy with the result for now, and the GXB20 driver has achieved all the goals I had set out at the beginning of the project!

By no means is this a complete nor 'commercial' driver, which will certainly require a little more optimization and better firmware, but I think I'm quite happy with how it is as-is, for a hobby project. Currently I'm working on finishing a more complete write-up on this driver, and will be publishing everything open-source for all to use and to fabricate boards (e.g. from OSHpark).

Some notes on the additional improvements of the GXB20 V2:

  • Better placement and layout (I hope!)
  • Much more levels of constant current brightness (256, adjustable using 1 resistor)
  • Improved lowest level of CC brightness (just around 1mA - true 'firefly' mode)
    • Modes for my own firmware: 1  = firefly <1mA, 2 = low ~180mA, 3 = mid ~600mA, 4 = ~1.8A (~1000 lumens), 5 = 3A (turbo)
  • Measured efficiency of 92% at 3A (~6.5V) output
  • Two new solder-bridge mode jumpers + extra GPIO for easy mode selections
    • (needs more firmware work to take advantage of all of these)
  • New 0.4mm pitch micro programming header for ATtiny84A
  • Works better at lower voltages when approaching 2.5V
  • + maintains all the features of the original GXB20 V1

 

I did some experiments in the power section but it turns out that they didn't make too much of a difference (e.g. in the previous post you can see I used a bigger inductor but didn't see much benefit).  The final improvement I'd probably want to do with this driver is to fabricate using half-thickness (0.8mm) PCB and 2oz copper, and of course continual work on the firmware to improve things further like adding more modes and improving EEPROM performance using a random hopping scheme.

Finally, above is another view of the GXB20 V2 driver.

www.loneoceans.com/labs/

- Next-gen Switching Drivers: Lume X1 and Lume1
- High Power Boost Drivers: GXB100 GAN 100W, GXB172 17mm 50W
- Older: GXF22, GFS16, GXB17 & GXB20

CRX
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Looking good Thumbs Up

tuelleric
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Good news! This is a pretty cool result for a hobby project!

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That looks so neat. Thumbs Up
The side picture gives another perspective to the difference in height size of the components.

 

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Rufusbduck
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Were you able to hit the 95% efficiency goal? Remarkable work here.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

texas shooter
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I see that the top says GXB20 V2.0 3V/6A. Is this a typo 3V/6A? What final voltage, amperage, efficiency did you get? And finally thanks for helping us out on getting a good single cell driver for these newer XHP LED’s.

DavidEF
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Nice work! It’s a beautiful driver!

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loneoceans
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texas shooter wrote:
I see that the top says GXB20 V2.0 3V/6A. Is this a typo 3V/6A? What final voltage, amperage, efficiency did you get? And finally thanks for helping us out on getting a good single cell driver for these newer XHP LED's.

Ah >< I was hoping nobody would notice the typo embarassed, but yep it was a mistake in the silkscreen - it's supposed to be 6V 3A. But I think I can claim that the nominal input power is ~3+V at 6A, so that's still ok :).

The efficiency numbers are roughly the same as the chart that I posted earlier. Again efficiency varies depending on the input supply and the load, but realistically the converter should have a total efficiency ranging from ~85 to 95%. This is the total converter efficiency, with some additional loss in the current sense resistor. Maximum I've tested for the GXB20 topology is the same as the previous with a measured 3.8V in at 6.32A, and an LED current of 3.26A at ~88% efficiency.  

However for the GXB20v2, I've measured a total converter efficiency of 92% with an input of 21.39W at 6.01A and output of 19.76W at 3.0A. I'm also pleased to say that the lowest possible brightness I got with the GXB20v2 is really low at an LED voltage of 4.52V and around 1mA, so it's a true moonlight, or more like fire-fly mode :). I have yet to fabricate a PCB with thicker copper (2oz) which will improve things a little more.

Regardless, as I've found, at such high power levels, just basic DC resistance plays a huge role in efficiency especially with low single-cell voltages. In practical aspects, I found it very challenging to avoid significant voltage drop at over 6A (at least with the cheap flashlight host I'm using), which I suppose places a practical limitation in how much more power I can push through. Any more and the voltage the driver sees becomes a little low, and overall efficiency also drops. 

www.loneoceans.com/labs/

- Next-gen Switching Drivers: Lume X1 and Lume1
- High Power Boost Drivers: GXB100 GAN 100W, GXB172 17mm 50W
- Older: GXF22, GFS16, GXB17 & GXB20

JasonWW
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I know this is a bit off topic, but how would this boost driver with a 4500mah 26650 compare to a linear driver of the same 3 amps, but using a pair of 2200mah 26350 batteries?

Would voltage sag be about the same under the same load?

Is efficiency a lot less?

I know there’s a big difference in 18mm batteries because name brand 18650 are much higher mah than small brand 18350. But with 26mm there doesn’t seem to be the big difference.

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Xoden
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Nice!
I wonder if it’s possible to get a smaller design with lower power. Like 17mm 9V/1A for 219C triple.

Rufusbduck
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Low power buck drivers are already available.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

loneoceans
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Xoden wrote:
Nice! I wonder if it's possible to get a smaller design with lower power. Like 17mm 9V/1A for 219C triple.

Yes it's possible and with a lot lower power, can definitely be made smaller too. However it's unlikely I'll have the time to work on it but I'm sure there are lots of other who will be Smile

www.loneoceans.com/labs/

- Next-gen Switching Drivers: Lume X1 and Lume1
- High Power Boost Drivers: GXB100 GAN 100W, GXB172 17mm 50W
- Older: GXF22, GFS16, GXB17 & GXB20

Xoden
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I don’t recall any in the 17mm size beside the KD BD8P. Which is both out of stock and unprogrammable.
Also, a small boost driver would allow to build a high-CRI EDC light using XHP LEDs.

loneoceans
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Xoden wrote:
I don't recall any in the 17mm size beside the KD BD8P. Which is both out of stock and unprogrammable. Also, a small boost driver would allow to build a high-CRI EDC light using XHP LEDs.

I do have a 17mm version planned for the future, but not quite now yet! 

www.loneoceans.com/labs/

- Next-gen Switching Drivers: Lume X1 and Lume1
- High Power Boost Drivers: GXB100 GAN 100W, GXB172 17mm 50W
- Older: GXF22, GFS16, GXB17 & GXB20

DB Custom
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Thank you for bringing this little experiment of yours to BLF.
I am also one that is very interested in trying one, whether building it myself with your flashed MCU or a complete driver.

Might would have to build a whole new flashlight from scratch just to honor your work on this ! Smile

cncyana
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Great work!

The idea of a boost driver for the XHP LEDs has been floating around this forum for how long now?

Someone finally has a grasp of how to get it done! 2017 is looking like a good year, in more ways than one.

Would love to put this driver into a nice host, maybe Texas Lumen’s upcoming c8-sized host?

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JasonWW
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How sweet would it be if cree decided to offer the xhp70.2 with a 3 volt option? All 4 dies would be parallel.

Just dreaming out loud. Lol

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DB Custom
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I can envision this is a smallish light with a beautifully tinted MT-G2, sure would love to see it…

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