large driver question

[tjones96761]

If I wanted to run 3 of these Bridgelux BXRA-27-E7000 emitters on 3 different heat sinks, can I run them in parallel off a single Excelsys LVX300-036SW (or similar) constant voltage driver? Am I going to overload anything or burn stuff up? can I push it to 4 emitters?

 

[tjones96761]

All the smart guys on here and no one can tell me if I can run 3 lights in parallel from a single constant voltage driver?

 

[RoGuE_StreaK]

Googled and couldn't find either of those products to get the specs, especially the Excelsys.
Common answer would be you want a constant current driver, not constant voltage. Closest Bridgelux number I could find required 350mA

 

[DIWdiver]

Like individual dice, these arrays are designed to run at constant current, not constant voltage. Running them on constant voltage will not yield predictable results.

I suspect the power supply part number you listed is incorrect. Googling the part number resulted in only one hit - this thread. Adding 'Excelsys' to the search got me to their web site, but they do not recognize the part number.

Smart people tend to be busy people. If you want them to take their time to answer your questions, you should at least do a little homework first and post accurate information. You can also make the work a lot easier by posting some more detailed information - ratings of the power supply, like voltage/current ratings, so they don't have to do multiple searches just to know what you are talking about.

Just posting a couple of part numbers doesn't pique anyone's interest. Maybe add some application information to get people interested?

Edit: Took me too long to post. RoGue StreaK beat me to it.

 

[RoGuE_StreaK]

Edit: Took me too long to post. RoGue StreaK beat me to it.

Sucker :nana:

Smart people tend to be busy people.

So what does that say about me?

And/or I'm just procrastinating as I lack motivation to get onto developing an eLearning module about capitalisation of assets...

 

[tjones96761]

I was also in a hurry, those are terrible examples now that I have a minute to look at them. It was more of a general question. I know the rule of thumb is CC for a single light, CV for lights in series. Because I'm running lights in parallel, I don't know which is more correct.
emitter - http://www_._digikey.com/scripts/dk...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
CC driver - http://www_._mouser.com/ProductDeta...=sGAEpiMZZMt5PRBMPTWcaRTgZe1UVjflcVzTTkwbT8M=
CV driver - http://www_._mouser.com/ProductDeta...=sGAEpiMZZMt5PRBMPTWcabPz/SJMUP4LBCL5Vim46ns=
What I'm trying to do is reduce overall size and footprint (hopefully total cost) by running multiple lights off the same driver.

 

[langham]

A few things, first you should remove the above links before they are removed for you. Second yes that CC driver will drive 3 I wouldn't use it for 4. Third I would use the CREE equivalent model the CXA series. Fourth, if you want smart people to reply you shouldn't call them out on not having any time because they are very pre-disposed. What kind of thermal management are you planning on using? I would have a seperate heat-sink for the array and the driver as both will be very hot at 300W. I would also pay very close attention to the Tj as it has signicant effects on overall output and efficiency. I would personnally directly copper mount these on a large copper heat-sink like 5mm thick or have a large surface. Notice how large the variation of Vf requirement is for different temperatures/currents? It also effects the color more than in a small led. This will make it difficult to tell, based on your application these perameters could change. The guy you should be asking has already responded DIWdriver is the expert on all things driver related. Don't expect to get 10Klm out of one of these either as they will probably have a Tj of close to 100C unless you are using some form of active cooling. You should actually calculate the amount of waist heat that will be produced and use enough copper/aluminum to disipate that heat being a little conservitive to account for the junctions. The way you can tell if it can handle the load is by the Watage rating being greater than 3 times the watage of the LED at the required voltage.

 

[ianfield]

All the smart guys on here and no one can tell me if I can run 3 lights in parallel from a single constant voltage driver?

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Running LEDs in parallel is a bad idea & running LEDs from constant voltage is a bad idea. If you only have enough voltage headroom for one LED - you have to put them side by side (NOT parallel) each with its own current limited supply. If you have enough voltage headromm for multiple LEDs in series you can run them from a single current limiting supply.

 

[tjones96761]

A few things, first you should remove the above links before they are removed for you. Second yes that CC driver will drive 3 I wouldn't use it for 4. Third I would use the CREE equivalent model the CXA series. Fourth, if you want smart people to reply you shouldn't call them out on not having any time because they are very pre-disposed. What kind of thermal management are you planning on using? I would have a seperate heat-sink for the array and the driver as both will be very hot at 300W. I would also pay very close attention to the Tj as it has signicant effects on overall output and efficiency. I would personnally directly copper mount these on a large copper heat-sink like 5mm thick or have a large surface. Notice how large the variation of Vf requirement is for different temperatures/currents? It also effects the color more than in a small led. This will make it difficult to tell, based on your application these perameters could change. The guy you should be asking has already responded DIWdriver is the expert on all things driver related. Don't expect to get 10Klm out of one of these either as they will probably have a Tj of close to 100C unless you are using some form of active cooling. You should actually calculate the amount of waist heat that will be produced and use enough copper/aluminum to disipate that heat being a little conservitive to account for the junctions. The way you can tell if it can handle the load is by the Watage rating being greater than 3 times the watage of the LED at the required voltage.

Not calling anyone out, just couldn't understand howthere were 100+ views with no response. Incorrect PN is a valid explanation. Iam also busy, hence the typo.
Why do you recommend the cree over the bridgelux? Personalpreference, product quality issue…
Absolutely, separate heat sink for each.
Active cooling with 28-30C fresh water. I was planning onaluminum cast. With water cooling, I was thinking thinner would be better(?)
Same as everyone else in LED, I'm trying to get the mostout of the least. I don't know how to extrapolate what the Tj will be withwater cooling. Only thing I know to do is get a few different things and dosome testing. Most likely I will have to hire someone to do the testing,because I don't have all the necessary tools or the time.
To summarize, sizing the driver is simply the sum of thewattage for each (or sum of amperage at required voltage of each), correct ?

 

[DIWdiver]

Yes, you want a CC driver or three, depending on whether you have enough voltage to run them in series. Current must match the desired current in the emitter. Voltage must be greater than the max voltage the emitter might require to get that current. Matching power specs can get you in the ballpark, but it's only a guide, not the final answer. Links don't work so I can't check out what you found.

As far as running them in parallel, it depends on the application. Right now I'm supposed to be working on a light that uses 30 LEDs, in 10 strings of 3, one group is 4 strings in parallel, the other group is 6 strings in parallel. My customer has put hundreds of these in the field over the last few years, and they are working so well, the mod I'm making is to push the currents higher. But they are 30 leds from the same batch, mounted on the same large heatsink, which is capable of dissipating the max power with only natural convection. Here's the potential problem - if one emitter gets hotter than the others, it's voltage drops. Since they are in parallel, it's voltage can't be different, so instead it draws more current. It heats up even more as the others cool off. If it's bad enough, you get thermal runaway, and the cycle continues until the hot emitter fails. If it fails open circuit, the current is all dumped into the other two, which also fail in rapid succession. This is much more likely in your application, where you will likely get three from the same lot, but not necessarily, and you have three different heatsinks, which require active cooling, with the nearly inescapable possibility of one getting poor cooling while the others don't.

Running water cooling in cast alu heatsinks should work quite well, as long as there's water flow. Close is good, but you don't want to get so close that you have temperature bands across the emitter where the cooling tubes are! I don't have a good answer for how close is too close, but if I were doing it, I would shoot for the distance from the tubes to the emitter being about half the distance between tubes, and not less than half the diameter of the tubes.

 

[tjones96761]

I put in underscores on each side of the dot after www in the above links after Langham said they needed to be taken down. So they're dead links for site restrictions, just remove the underscores and it will connect.

something else to consider, I'm not looking for 100,000 hours of life out of these things. I actually intend to have enough testing done to determine how far the chips can be over driven and maintain about 1000hr life. I estimate that to be more than a years worth of operation. For the application the manufacturer designed lifespan is way overkill. I believe (or I'm hoping) that more can be done with less. At the rate technology is changing, I don't think it's beneficial to operate longer than a year in this application.

I hadn't considered if 1 were to fail. Isn't this another reason to run CV and just accept the fluctuation in output and color?

This will all be going on boats that go out maybe twice a week and only during the summer. If I can use 1 set of emitters for 1 year for $400 +/- , it is still a substantial advantage to the maintenance issues and associated cost per lumen of the best available option today, which is HPS. This is an expensive hobby already. being able to offer a product that is roughly half the maintenance cost would be a home run. It's not about the power savings at all, it's all about ease of use.

I'm starting to think the direction I'm trying to go is so far off the intended purpose of LED lighting, that I'm not going to find much relevant information.

 

[DIWdiver]

I put in underscores on each side of the dot after www in the above links after Langham said they needed to be taken down. So they're dead links for site restrictions, just remove the underscores and it will connect.

Part of the address has been replaced by '...' so I can't cut/paste. I didn't see the links before you broke them, but you can post links, just not hotlinks. The difference is a hotlink brings up the content of the link without me clicking on it. The rules are a little more complex than that, but I'm guessing you had hotlinks and that's what Langham was warning you about.

I hadn't considered if 1 were to fail. Isn't this another reason to run CV and just accept the fluctuation in output and color?

No, it's a reason to use individual CC drivers.

 

[RoGuE_StreaK]

Part of the address has been replaced by '...' so I can't cut/paste.

Right-click and copy - the full edited link is there, just that the forum concatenates long links in the text view