The Texas Buck driver series, Q8 / Skyray King 2S/4S buck driver RELEASED!

It very well could not hit 10k lumens, no guaranty there till someone tries it.

I am guessing that you were using an FET driver when pushing the XHP35? Taking an educated guess I am guessing you controlled the current by setting a max duty cycle on the FET?

As we all know an FET is much less efficient then a buck driver when it comes to LED output and heat.

A buck driver is constant current which allows for exactly the current you want to be sent to the LED and thus the LED can function much more efficiently.

I know that Acebeam makes 2600 lumens from an XHP35 HI in the K70 with lower binned emitters then we have now days and I am sure they are not 100% maxed out as well.

It is theoretical for sure but if Acebeam can do it I see no reason we can’t as well, particularly with LED’s at least 2 bins higher then what they had access to.

If not then it will still be a LOT brighter then the XP-L’s the Q8 will come with stock :wink:

It could also be used for XHP50’s or 70’s as well naturally. 4x XHP50’s would easily reach 10k lumens and a fair amount more based on others testing.

Not an FET, I modified led4power’s LD-2 driver. A regulated 2.89A. Bottom line though is that the XHP-35 is sensitive to the amperage, in many cases I’ve heard of em blowing even lower than I’m running my last one. So it would appear that the 2.9A range is about peak.

Acebeam doesn’t necessarily tell 100% accurate numbers.

XHP-50’s is a likely bet, 70’s are monsters and can take massive current while also producing massive heat. These 2 also have the donut hole issue. Trade-offs, everywhere we look…

Following

Interesting, strange that they could only manage a ~16% increase over the factory ratings. Cree led’s generally get closer to 40-50% more then rated when on DTP stars and driven well.

Although we do have XHP35 HI’s in bins 2 higher then I am sure you used, so that would be around 2500 lumens all else staying the same unless you were using the HD version of the 35 in your build.

I have an XHP35 here that I could torture test with the now calibrated sphere you sent me to see what it can really do but I didn’t want to risk killing it as I don’t want to have to pay for shipping on another order from cutter. $30 shipping on a $7 part is just hard to stomach. But then I have not seen any tests on the XHP35 yet and I would really like to see what it can do……

I tested a few XM-L2’s when calibrating the sphere and it was reading dead on the factory spec sheet.

If I haven’t said so, thanks again for the sphere, it has been great! I used it to calibrate my PVC sphere as well for the larger lights and after a few minor changes I have it reading the same as the sphere.

I have 7 XHP-35’s, all HI variants and all top bins. :wink:
Richard has some good ones on Cutter mcpcbs. another :wink:

Remember that the XHP-35 is 4 XP-E2 dies in series, that’ll help wrap the mind around the limitations.

I'm following this too, but I don't understand the real detailed design issues involving buck drivers. Many have tried here on BLF to design a good buck driver, and the only one I know that came out successful, and was completed, was Richard's, so it's a good foundation to start from. As far as efficiency, all buck and boost drivers, have power (watts) loss's as I understand, where a FET is more efficient every time, in terms of minimizing wasted power (watts). In regulation of course, buck and boost drivers have big advantages.

Richard doesn't say anywhere in his MTN MAX page, but I assume he's using PWM's across all modes, accept hi, so you don't get mode level regulation.

I saw a few places that it uses the G2 dies or at least dies the size of G2’s?

The spec sheet shows it is much closer to a 4x XP-G2 then E2 as well. Particularly when you take into account that the G2 has a dome and the XHP35 does not it is virtually the same on the spec sheet.

What bins are you using? I was under the impression that the E4 was only released a few months ago?

http://www.cutter.com.au/proddetail.php?prod=cut3023

E4 1D are my latest 4.

Frying the emitter at under 3A per die is more consistent with XP-E2 performance, XP-G2’s can take over 5A apiece.

Yeah, I am learning as I go with the buck driver design, it is actually quite simple and ingenues once you wrap your head around it. The design of the actual buck driver is not a big issue as long as I can reverse engineer the MTN MAX driver to see how it is laid out to make sure I am getting the schematic right.

The only real hang up at this point that I see is the parasitic drain issue. Although like I said above I think this could be solved by powering the MCU directly from the batteries and thus not using the buck converter 5V regulator.

This allows us turn the buck converter off when the light is off by a small FET, thus eliminating any drain in the system besides the MCU. It would have a free pin to control the FET since it would only need a single output to control the buck converter. The FET would simply shut off anytime the MCU went into sleep mode.

This is the basis I am working on at the moment.

Someone like DEL would be the best to get an opinion from, I know enough to understand the basics but not how everything interacts.

The MCU does output a PWM but it is only used to tell the buck converter how much current you want. The buck converter does all the actual work.

I did a bunch of reading yesterday but can’t find some of the links that were good. Here is one that explains things:

A bit long but good.

Basically a buck converter is a normal FET circuit with an inductor placed between the FET and LED. The inductor stores energy when the FET is on and slows the voltage rise, then when the FET turns off the reverse happens. It releases it’s stored energy and causes the voltage to drop slowly (in comparison to instantly stopping).

What the buck converter does is watch all of this happen at up to 2mhz+. It then times the FET to turn on so that voltage/current increases to 5% over your target level. It then turns the FET off and lets the inductor release the stored energy until voltage/current (remember they are directly connected with LED’s) is 5% less then target.

It then repeats this process endlessly giving you a regulated and constant current with a 10% ripple (aka, 5% over and 5% under target). Better buck converters can obviously be much better then this but the one we use has a 10% ripple.

That is the basics to how it works, just an FET with an inductor, technically you could make a buck driver by simply adding an inductor to a normal FET driver. but the circuitry to actually monitor things and ensure constant current is a bit more complicated, which is where the buck converter comes in.

The ripple is not a big deal in most cases but if you add a large enough capacitor to the output from the inductor you can further clean up the signal. The old Skyray king drivers had this setup.

Far as I can tell the limiting factor when it comes to current is the inductor, small ones just can’t handle high amps and the larger the inductor the better. Since we have a lot of room in the Q8 this should not be a problem. The one I linked above is rated for 18A and would easily fit in the Q8 assuming we have at least 6-8mm of height clearance, which we should.

Honestly the biggest issue I see for a buck driver in a flashlight is size, trying to fit it on a 17mm board and make it supply high currents would be silly hard and you would need to overdrive the inductor causing a lot of heat.

I think I am going to move ahead with basically using the MTN MAX driver with an FET to turn the buck converter off when sleeping and see what the schematic looks like.

Anyone that has something to say, please do say it!

I pretty much need to finish these driver projects this week as my free time will be cut drastically after that.

Interesting, no idea what to make of it, seems odd that acebeam would be lying by that much, CPF seems to think they are making more then 2600, I saw claims of 2800 lumens.

Either way, the exact number doesn’t really matter. it can be done for sure with an XHP50, maybe the MCPCB could be designed to allow for XM pads as well as XP? I know it was brought up but it was not selected for some reason.

Another key to a properly working buck driver is a high quality, fast switching FET.

It needs to switch as fast as possible to minimize heat build up. I know the SIR400’s work well for high currents and don’t generally have any issues but has anyone looked at how they handle high frequency?

We were just discussing the die size in another thread. It seems like the lateral size of the XHP35 is more consistent with it being 4 XPG2 sized dies.

How are the XHP35 emitters frying? Is it at the bond wires? From pictures it looks like all the current flows through one bond wire instead of two like on the XPG2.

Regarding the output differences between measurements and Acebeam’s claims: could some of that be OTF lumens vs LED lumens? I would guess there could be up to 20% loss in the flashlight.

Is there somewhere that has better measurements than that graphic? It doesn’t use any unit of measurement, and it is showing “optical source size” instead of actual size anyways.

I suppose that acebeam could be using emitter lumens, although I thought they are FL-1 ratings? Or are they one of those manufactured that just slap a number on the lights? I thought the little I heard about them said they were reasonably honest about the ratings.

The bond wires is a good point though, that could very well be the case, they do seem to be going at right about half the current of normal XP-G2’s

It would be easy for someone with a HI version to just measure it, but I don’t have one. The “optical source size” seems to be consistent with the lateral size, though, because it says the XPL HD is ~1.5x the size of the XPL HI, which is consistent with our observations that dedoming reduces apparent area by ~1.5^2=2.25. Also it agrees with our observations that the XPL HI and XPG2 with dome are about the same size.

I just measured an XHP35 HI best I could without damaging it.

Comes out to between 2.65-2.75mm or there abouts, hard to get an accurate reading without messing up the silicone and risking it burning later.

Ehm a lot is way over my head here…
I assume the focus is on the xhp35 because they could be reflowed on the Q8 ledboard as hoped for now?

With the 4 18650 cells a 2S2P configuration makes more sense to me then 4 series.
A boost from 3-8.4 to 12V should be given in this case but longer runtimes and a mod I would dare start :wink:

Yes, the XHP35 is mostly due to it being a direct replacement, if the MCPCB was changed to the other design that was purposed that had pads for both XP and XM LED’s then the XHP50 would be the one to watch.

Far as 2s2p vs 4S. 4S makes more sense in this case IMHO.

Firstly the XHP35 must have 12v so it has to be 4s.
Secondly all the XHP series can be run in 4s mode or run in series to work in 4S mode.
Lastly higher voltage and lower current = less heat in the driver/components and thus less resistance. This allows you to be more efficient and push more power.

Why do you think that all the major manufactures go with the cells in series whenever possible? It is easier and better from an electrical point of view.

There is nothing that 2s2p offers that 4s doesn’t do better if using a buck driver in a light with 4 LED’s. No matter what the setup you can make it work better (aka, more efficient) with 4s. Now sure the changes are not much but there is simply nothing that 2s2p offers that is better.

Technically the best possible driver setup for the Q8 would be a buck driver running 4s and driving all 4 XP-L’s in series. This way each LED would get exactly the same current and it would take less total current flowing through the system.

Instead of ~16+ amps it would only need ~4 amps to reach the same wattage/lumens (4 amps x 16 volts is the same as 16 amps x 4 volts).

Because there would not be as many losses in the driver/wires/springs/everwhere you would actually be able to push a noticeable amount more current as well netting more power. The gains could be as much as half an amp per LED depending on how much resistance is in the system.

This is why all the big manufactured run the batteries in series, it simply works better.

[quote=Texas_Ace]

Can sign all posted.

Guys, do not exaggerate XHP35 possibilities. They are limited by thermal conductivity and thermal pad area. If both are same, led can not be able to provide more than XP-L. Just few percent more efficincy cause less losses cause lower current rates.

selfbuilt's review has measured lumens, and I trust his measured estimated lumens more than the manufacturers. His # is 2,275 lumens, here: http://www.candlepowerforums.com/vb/showthread.php?421264. This makes more sense, plus that big 88 mm reflector - big reflectors do seem to squeeze out more lumens, like the old TN31. Maybe between the size, SMO, and good AR lens... dunno.