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FrozenGate by Avery

Driving an NUBM05 array.

R

rmfd

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Hi LPF, I'm hoping you can help point me in the right direction on a little project of mine. I'm hoping to drive an array of 8 NUBM05 in series as currently wired in the link below. Unfortunately, I'm having a hell of a time tracking down a driver that will provided the power needed. Am I missing sometime or does such a driver not exist?

Thanks in advance!

New Nichia 450-460nm Blue laser Diode module 8*3.5W /28.5W NUBM05 | eBay
 





You can make your own linear driver's and power them as laid out in 2 strings of 4.
Correction, this looks to be all 8 in series.
s-l1600.jpg


You can also get that block for less and likely less still in another month, but it's not very useful in this format and needs a big heat sink.

NICHIA NUBM05 455nm 28W High Power LD Bank/Blue Laser Diode Array/New but w/ PCB | eBay

----EDIT----

Do NOT trust the ebay DC to DC converters, they can spike.
 
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Cooling isn't much of an issue in this case... The bigger issue is getting a driver that can run at 36ish volts.
 
Yes, this driver might work if you have an input battery with voltage higher that output voltage needed for current you want to pass through 8 LDs.

But I would maybe modify this PCB a little to have 2 series of 4LDs - and are you sure that the original PCB is not made like that?

I also plan to do this with a block of NUBM08 in the future and I am more of opinion to use step-up drivers than step-down drivers. I am not expert of electronics but after trials to drive serially connected 07s I liked those step-up drivers more because they slowly rise voltage from input value until they reach the preset output current while step-down or buck drivers go to maximal preset current very fast.

For another test I took the KE array from A135 PJ (some are cheap on ebay). The 24 LDs there were connected as 4 series of 6.
I soldered these 4 chains (each of 6 LDs in series) in parallel to the output of cheap BST400W driver (from aliexpress) and used 5 cell LiPo as input. Preset current 6A to have 1.5A through each of 24 LDs. After switching on this value was reached in 5-6 sec. All spots were slowly gaining on luminosity at constant rate, so I think that distribution of current through all 4 series should be pretty uniform. I would even conclude that all blue LDs manufactured now have pretty uniform resistance.
Also, 3 cells LiPo voltage was not enough to reach total ouput current higher than 3.7A, what means less than 1A for each series of 6 LDs.

I do not know if this info could help but I would try the same set on 8 LDs in series just because not 6A are needed here but "only" 4.5A I suppose.
The power = Voltage drop in a series of 6 blue LDs multiplied by 6A should be close to same for 8 blue LDs and 4.5A.
 
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I think you will find that the LEDs are much more forgiving than LDs, and the resistance of the LD depends greatly on the heat it produces. So, no two LDs will be the same depending on heat at any instance in time.
 
Hi Paul,

You are right, I did not say it correct.

What I want to say is that the summary resistance of any long enough (6+) series of LDs shoulds be quite similar because the low/high resistance LDs most probably are randomly distributed between each of chains.
That might be the reason why the 24 LDS in that PJ were connected to driver in series of 6. Of course it could be that the PJ board had a separate driver for each chain, but when I soldered them all in parrallel, the brighnesses of all 24 spots were very close (not at start of voltage increase, but when the current preset was reached).

So maybe 2 chains of four MUBM05 each could be driven in parallel by this way without need for a driver capable of 36+V, too.
 
Driving LDs in parallel are always more involved than driving them in series. In series all you need from the driver is enough current for an individual diode and the sum of the Vf of each diode in the string. If strung in parallel, one needs to be aware that any diode in the string may heat up and go into thermal runaway. The easiest way to solve this is to put a small value (1ohm) resistor in series with each diode. If they start to draw too much current, the resistor will drop the voltage and lower the current into the diode. These resistors will have to be high power (watts) as you won't get away with using a 1/2 watt resistor. So, it is still far more simple to use them in series.
 
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