Anyone worked with either of these drivers from Lightmalls?

You measure the input current so the led current is higher but anyway 10W on two XMLs are only 1.5A or so…which is way to low. But this could get better with a resistor mod.
The really bad news is that it doesn’t deliver full power on a slightly higher battery voltage than the forward voltage, areasonable mtg2 driver should drive until around 6.5V. I am also interested on a coil free picture.
Glad you have ordered the other one too, this will work way better.

Have you followed one of threads with the hx1175b drivers, it seems to be a really badass one.

I’ve seen that other thread, but haven’t really followed because I think those are larger (diameter) drivers? I’m more interested in smaller drivers.

Hi,

Ok, I measured with a single XM-L (on Noctigon). The current at the power supply (Vbat/Vin) topped out at about 1 amp, about 4.5V. If I increased the Vbat/Vin to higher voltage than that (I went to about 5.2V), the current at the power supply would start dropping. I didn’t go much higher than that voltage since it was only a single emitter.

I think that the bottom line seems to be that this driver is about a 1 amp driver, rather than a 3 amp driver as “advertised” :(… Disappointing after waiting for so long for shipping from LM…

I agree, the driver is likely not capable of the advertised 3A. It sounds like you have unfulfilled needs though, so IMO we’d better make sure! The next step is a resistor mod until you reach the desired current or it fries. “random resistors” is a game those guys sometimes play, it’s possible that the sense resistors the driver came with were a mistake.

4.5V for single emitter is really useless, I guess it is a buck driver so it should be able to drive a XML with 8V…
Increasing voltage->decreasing current that is normal for a regulated driver.
Just the emitter current stays constant, but I guess in this case it is 1.5A or so.

I didn’t mention this earlier because I wasn’t paying much attention to it, but I had a clamp meter on the emitter lead when I was testing, and it was in the same range current-wise. What I mean to say is when I was increasing the voltage at the power supply (and watching the current drop at the power supply), the emitter current was kind of going the same way (i.e., it wasn’t increasing).

Can you tell which resistors might those be? I’m assuming that that was why you all were asking to pull the toroid, but I’m not sure when I’ll have time to do that, so I don’t mind doing some random resistor shorting in the meantime to see if I can get the current bump :)!!

I always discourage people from shorting resistors. When I say resistor mod, I mean changing resistor values or stacking resistors, not shorting resistors. I understand that other people may have a different perspective and that that’s confusing. Shorting sense resistors on either buck or boost setups normally fries stuff. Only certain specific drivers have extra limits which prevent that.

The sense resistor(s) is under the toroid. I see one right next to the 1165c silkscreen. You’ll definitely need to pull the toroid order to do the mod. Pulling the toroid shouldn’t take you more time than shorting resistors would have? In order to work on the driver more efficiently I’d recommend removing the toroid, attaching LED+ to one leg of the toroid, and attaching the other leg using a short wire of appropriate thickness to BAT+ (or wherever it was connected to start with). This will let you do work without moving the toroid on and off of the driver.

There are other things under the toroid we want to see as well :slight_smile:

As you increased Vin the emitter current was

  1. Staying constant?
  2. Dropping?

I’ll let you know tomorrow…

It looks like the emitter current gets to about 1.25-1.3V, then stays pretty much constant as I increase Vin.

Good work. That describes proper behavior for this thing. Next step is to reduce the sense resistance.

Can you explain what you said? Are you saying that because you believe that this is a buck driver at this point, and the behavior I’m seeing matches that of a buck driver?

I’ll take a look at pulling the toroid off this weekend.

Thanks,
Jim

It’s definitely a buck driver. Your earlier description left the possibility of a malfunctioning buck driver. We now know that it’s a properly functioning buck driver. :slight_smile:

A “properly functioning, but incorrectly-spec’ed buck driver” (the 3 amp part) :)…

Here’s a link to the resistor mod thread for the other driver. What’s unknown is the resulting emitter current.

Hi,

This’ll be a bit of cross-posting, but I just noticed that the driver in the Cofly KX-T21 is apparently this smaller driver:

Jim

I’m curious about something?

On the other thread about the Cofly light which appears to use the same driver, nofearek9 reported 1.4 amps at the tailcap with 2xLi-ion. So I guess that’d be like 1.4 x 8V = 11.2 watts, right?

On the emitter side, let’s say the Vf was about 4V, so if the power-out was ~11.2 watts, then emitter current should be about 2.8 amps?

But, from the testing I did initially with the bench power supply, even though I didn’t go more than say 5.5V, current at the emitter didn’t increase to that level (seemed to go down instead)?

Shouldn’t I have seen, say, 3 amps at the emitter?

I’ll need to test with the single XM-L again, but this time, bump the Vin to the driver to maybe 8V (yes, I’m willing to lose that emitter)…

EDIT: I just tested again, both with a single XM-L U2 (I think) and a new XM-L2, and am seeing the same behavior I saw before. With Vin up to 8V, the current both at Iin and Iemitter were dropping to about 0.7 - 0.8 amps. I also measured Vemitter (just in case) and was about 3V with the XM-L2 (I didn’t make a note of it for the XM-L, but I think that Vemitter was about the same, i.e., about 3V).

So I’m still puzzled!

I understand this is a buck driver, but where the heck is that power/watts disappearing to? Is the driver soaking up all the extra power/current?

I SHOULD be seeing about 2+ amps Iemitter, correct :(?

EDIT:

Although this is not the right chip, just to get an idea, I found this:

http://andrewpearson.org/?p=643

So, assuming that this driver is using a similar chip, I am guessing that the answer to my question about where the excess power is going is to the sense resistors in the R1/R2 voltage divider (fig. 11 in the above page), and probably the reason I’m seeing lower than 3 amps is that the sense resistors’ values are controlling that.

So that’s why you all are looking for the board without the toroid, to try to figure out which resistors could be/need to be changed to try to bump the driver output current?

Your description of whether emitter current (Iout) stays constant keeps changing! I asked for clarification earlier and you clarified by giving an example where it did not change. :frowning:

Iout should stay the same once Vin is above a certain voltage. Your most recent description of Iout dropping shows a problem of some sort.

Let’s really make sure we are on the same page now. Are you saying that Iout stays constant with 2*XM-L but changes with only 1*XM-L?

In the most recent scenario you described [With Vin up to 8V, the current both at Iin and Iemitter were dropping to about 0.7 - 0.8 amps. I also measured Vemitter (just in case) and was about 3V with the XM-L2] all your losses are in the driver.

After your good find in nofearek9’s COFLY KX-T21 review we are left with 2 or 3 possibilities (that I can think of):

  1. You got a bad batch of HX-1163c drivers, nofearek9 got a good one in the COFLY light.
  2. The version you got is on the same PCB but uses different components to support higher Vf than the one in the COFLY light. And it’s just a crappy driver after those modifications.
  3. The version you got is on the same PCB but uses different components to support higher Vf than the one in the COFLY light. And the particular items you got are defective.

Without component values from a working board it’s going to be difficult if #2 or #3 are the case. I could not find specifications for this driver on Lightmalls, they don’t even list that it’s a buck driver, the input range, or anything.

I think your interpretation of where the extra power is going is probably wrong. If the sense resistor(s) was burning off 3.5W you’d know it ;-). One or more things should be getting fairly hot though. Once you move the inductor out of the way we can check.

Basically this board is nothing but a (broken, non-functioning) mystery right now. Werner and I asked to see clear pictures of the board without the inductor because of that. We don’t know the parts in use, their configuration, or anything. I doubt that there is a magic button under there, so there’s only so much good to be had by guessing what we want to see under there… if taking the inductor off and showing pictures on the forum generates results you’ll learn from that! A list of all legible component markings would also be useful - sometimes those chips are very hard to read even in good pictures.

Oops. As a follow up, I took a slightly closer look at the blog post you linked to. Figure 11 is… not relevant. It shows a constant voltage configuration, not a constant current configuration. I’m no guru, but I strongly doubt that the modifications Andrew Pearson suggested to Fig11 work correctly. I would hesitate to use his blog post about a probably failed project as a learning resource. (no offense to AP, I encourage everyone to try and make high current drivers!)

Note that there’s no followup post with a success story. I’d say it’s a safe bet that this project was abandoned because it did not actually function.