Driver Info: HX-1175b & HX-1175B1 (Pic Heavy)

I will post some more details soon, but all it needs preliminarily is a little output capacitance. 22uF ceramic is enough to keep it from blowing LEDs with the factory sense resistors.

I also tried swapping FETs, diodes, and adding more inductance, none of which seemed to help at all. I was surprised that adding more inductance didn't work.

I will see how far I can push it with extra capacitance. Unfortunately I don't have an oscilloscope so I can only tell whether or not the voltage is staying within the limits of an XM-L2 but I suppose for our purposes we don't need a perfectly clean output.

Good work RMM. It seems that an inexpensive scope might pay dividends if you are burning up a lot of LEDs in your testing? Just FYI, the PC based one comfychair is using is $75 shipped from the US.

I do have a scope, although I only get one channel. It seems that my QX5241 driver zapps LEDs at 6A, based on one potentially flawed test. I’ll get some more caps in hand and take a look at that on the scope ASAP… starting at 4A of course ;-).

Just a another quick update:

With two 25v 22uF ceramics on the output I can run 50 and 68 ohm sense resistors together with no issues, which delivers over 8A to the emitter with 18 AWG wires. My TK61 is pushing over 2000 lumens OTF now!

Sometimes the simple solutions are the best ones.

I know you are always pressed for time. Would it be possible for you to grab the 4 values required for an efficiency calculation? Vin/Vout Iin/Iout

Either way, thanks for the update!

I spend much time at the law office these days! If I remember correctly, it was pulling about 5A on the input for over 8A on the output... sorry but I don't remember the exact numbers but I am going to be building some more this week. I'm guessing that efficiency is around the 85% mark when it is run full bore.

I think I am going to order an oscilloscope. There have been a few things that I have been able to pin down by trial and error and lots of online searching, but it could definitely be a time saver (and time is what I am usually short on.)

In a few more weeks I will be done with my law office/internship assignments and back to regular school, which interestingly enough gives me more time experiment, list, etc. I thought I would have more time this summer but I have had significantly less because I decided to take on the second job along with the first.

RMM wrote:

With two 25v 22uF ceramics on the output I can run 50 and 68 ohm sense resistors together with no issues, which delivers over 8A to the emitter with 18 AWG wires. My TK61 is pushing over 2000 lumens OTF now!

Sweet! Congrats and thanks for the info.

EDIT: Please let me know if you start selling modded versions of these drivers. I will put a link in the OP.

They don’t have the same pinout, that much we can be certain of. I’m moving this conversation back into your thread though, this info is more useful there!

Based on the photos in RaceR86’s post #67 in this thread I’d say we’re almost certainly dealing with QX9920. If that's the case, I'm starting to see why they've got all those resistors around the PWM line. They appear to be abusing the EN (enable) pin rather than using the TOFF (PWM) pin. I wonder why?

QX5241
1. CSN
2. DIM (PWM)
3. VIN
4. Vcc (regulated output for MCU/etc)
5. DRV (gate)
6. VSS (GND)

Mystery chip
1. DRV (gate)
2. VIN oops, GND!
3. (PWM)
4. VDD (from zener W8 by way of S4 RP protection diode)
5. ?
6. CSN


QX9920 (marked with LEDA & date code probably)
1. DRV
2. VSS (GND)
3. EN (Chip Enable)
4. VDD (needs regulated VIN)
5. TOFF (PWM)
6. CS (CSN)

Darn. Thank you for all that good info wight.

I actually have the QX5241 chips because I ordered them when you first started your QX5241 thread. Seems like too much trouble to hard wire it. I'll try to find some of those QX9920's and hope for the best.

I've been meaning to catch up on your QX99205241 thread and also on Ohaya's LM's Driver thread that you have been helping with.

No problem.

I definitely wasn’t suggesting an attempt to hookup the QX5241 in place of the QX9920 - I just listed the pinouts to illustrate my point. I’m not saying it can’t be done, but we’ve got enough hurdles as it is!

We should be in shape for you to use up a couple of those faith-purchased QX5241’s soon. Maybe not in 17mm yet, but at least in 20mm. Do you also have SO8/Power-SO8/LFPAK56/whatever N-channel FETs? If so we may as well get you hooked up with some PCBs so you can start blowing stuff up.

I think these may be the cheapest QX9920 on AliExpress in QTY=10 or less at ~$5/shipped for 10:
http://www.aliexpress.com/item/10PCS-QX9920-9920/1068294410.html

+1

Not sure. I only have a few different type of N-channels. I'll check and get back to you.

Ordered set of those QX9920's. I'll report back how they work out.

I just tried Richards cap solution, but I didn’t change my resistor set-up that I was using with the Luminus SST-50. Which proved to be too much for the Cree. 8.23A at the emitter on the Luminus SST-50, completely de-domed and naked as a JayBird. I have a R068 and R140 along with an R200 and R140. This should be R029419 which is a wee bit less than stocks R034.

Working on creating a base for the reflector to sit into so it stays centered when I tighten the bezel. Wish I had more Sugru…

I have spent more time working with this driver over the past few weeks than I care to admit (along with killing over 25 LEDs!!!!)

These are a few of my current observations:

1. The stock driver with the stock MCU and sense resistors (stock everything) on the highest level produces a voltage peak of around 4.22v, valley of around 3.26v, for a whopping 0.96v of ripple! Most XM-L2s seem to die at around 4.15V+ so the stock driver is too much for good input cells and thick wires.

2. The stock inductor seems to saturate at 100%. You can vary the PWM levels and sense resistors and the output will be fairly smooth and controlled until around 6A output, after which point things get out of control in a hurry. A larger inductor (more saturation capacity and uH) smooths things out a LOT at higher current levels, but makes the lower output levels have more ripple.

3. Adding some additional INPUT capacitance helps smooth things out at the higher drive levels. I suspect that the driver attempts to overcompensate for the input ripple.

4. Extra output capacitance helps a little bit, but not enough to keep from blowing XM-L2s unless you add a combination of ceramics and a LARGE (1000uF) electrolytic on top of that. This is just masking the underlying issues (toroid too small; too much ripple)

5. Fast 19.1K PWM works great coming from the attiny13a. I seem to get the best and smoothest results using this then setting the peak PWM level to around 200 instead of 255 (full on.) The buck IC seems to like this better than going 100%...you get around 95% of the 255 output but the output ripple is much lower. The buck IC seems to react much differently to full on PWM vs almost full on PWM. If you need more, just reduce input resistance.

6. You can piggyback or switch out the flyback diode if you want to reduce heat a little bit.

7. The 70N02 works as a replacement for the stock FET and it also seems to reduce heat generated by the driver (probably a much lower on resistance and/or faster switching time.)

A few takeaway lessons:
i. The stock driver will probably blow domed XM-L2s and will certainly blow dedomed XM-L2s (they seem to take a bit less overvoltage to blow). You can possibly get away with running it with an XM-L2 stock with 24AWG or smaller leads. The driver blows LEDs due to excessive voltage spikes not due to excessive current.

ii. If you want a good reliable buck driver without changing a lot of things, just add more resistance to the limiting bank. If you get it down to around 5A on the output it works great without any other driver changes.

iii. The quickest and easiest way to get the driver smoothed out at higher drive levels (6A+) is to add a larger inductor, add some input capacitance, and limit PWM to around 200 with fast PWM. The larger inductor and extra capacitors do add size to the driver so this won't work for some setups.

iv. If you want to reduce heat at the higher drive levels (7A+), swap out the FET and piggyback another large diode onto the flyback. The next biggest heat producer are the big limiting resistors but there is no way to get around that loss with this driver.

v. On the scope, adding modest amounts of output capacitance don't seem to help a lot. For higher drive currents, focus your efforts first on the inductor then on the input capacitance. If you need a bit more after that then you can add some ceramics to the output (but I doubt you will need it.)

^ Wow, 25 LED's lost in the cause for improving performance. Talk about sacrifice. Thank you for all that and the resulting info. The ones I currently have will just have to be for lower current xml2 or higher current MT-G2 as I don't have the electronics knowledge or components you discuss.

Do you know at this point if you plan on selling these drivers?

I will probably offer some for sale in a month or so. It has been much more complicated than I thought it would be. The MT-G2 and SST-90 can handle much more abuse than the smaller LEDs, that's for sure!

I was hoping to share some insight so nobody else would have to waste so much time and so many LEDs trying to get it to work.

I am trying a few different inductors now to find the optimum one. Once I find the one I like the best, I'll post the specs here.

Good work. How high can you take the drive current with the larger inductor? Also, do you know the value of the stock inductor or any of the ones you tried?

I don't know the value of the stock inductor, but it seems to saturate somewhere around 6A...at around 6A-7A depending on the driver the output ripple increases by around 5-10 times regardless of anything else I do to the driver...which tells me that the inductor core is getting saturated. The actual inductance the stock inductor seems to be enough but the core can't handle the current. I had a few inductors laying around that were all 15A+ but only in the 10uH range and they weren't enough. The one that is working well is off of a 600W boost converter so I don't know its exact value, but I have several 20uH+ inductors on the way so I can get the best value/size ratio tuned in. Stay tuned.

The new oscilloscope actually ended up costing me more LEDs because I would have otherwise given up long before I did! The scope gave me hope of being able to resolve the issue. After a while, looking at the scope image I could usually tell on the second-to highest level whether the LED was going to blow on the highest level before I ever clicked it up but I usually clicked it up out of sheer hope and desperation anyways!

I’m building a light and plan to use this driver (7A) stock with an MT-G2.
Do you forsee any problems?

I haven't tried it with an MT-G2 but others here have been pretty successful with it. Are you planning on 3S input? I could give it a spin tonight...although I will shed a much larger tear over an MT-G2 loss than I will over an XM-L/XM-L2.

Very detailed testing and at some sacrifice, appreciate the hard work and time spent.

I’ve also blown about 8 emitters with this driver, have a de-domed XP-L running stably at 7.2A now. I used even larger sense resistors and used a pair of R070. Vishay-Dale from Mouser if I remember correctly.

May or may not be looking to use my second driver. Am still pretty blown out from all the xperimenting on this one. :slight_smile: