400 watts of LED power supply, question

[Millipede]

can i run 4 of these on a single 100w power supply?
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[Av8tor1]

you want to run 400w of load on a 100w power supply?

personally, I wouldn't run one of them on a 100w power supply... Its just not a good idea to run a power supply under 100% load for long term reliability.
4x its rating is just asking for a melt down.

but that's just my opinion fwiw

 

[Millipede]

so does the power get divided between them? I want to use four (dimmer) to spread the light out more instead of have one running at full power. I want to stay at 100w. Should i get 4 25 watt lights or what

 

[Av8tor1]

depends if you connect them in series or parallel.

to do what you're wanting to do, you would need to connect them in series,

you will be running each at 25% power that way and putting dimmers will give odd results, each dimmer will effect all four

 

[Av8tor1]

(assuming your "dimmers" are basic rheostat or potentiometer and not pulse width modulation controllers)

either way, you will need to connect in parallel to have individual control, and parallel will likely end up smoking the power supply unless you closely monitor power levels

you would be better off getting 4-25w and connect in parallel, then your dimmer's will have the control you want.

still don't know if i would run a power supply at 100% load though, but in theory it should be able to handle it i guess.

She'll get hot if you run each at max... be prepared for that.

 

[naoki]

either way, you will need to connect in parallel to have individual control, and parallel will likely end up smoking the power supply unless you closely monitor power levels.

Av8tor1, what do you mean here? I can't see how parallel connection will cause the problem with the CC driver. As long as the forward voltage (Vf) is within the constant current range of the driver, it works. This kind of cheap COB usually have the forward voltage of 36-38V. So-called "100W" LED indicates the maximum capacity. Under-driving the LED is the way to go for the efficiency, most of the time we drive the LED at much lower power.

Also, you do want to match the driver with LEDs so that the LED load is close to the maximum capacity of the CC driver. The AC/DC conversion efficiency suffers if you don't load the driver. Some of the modern CC drivers can have 94% efficiency, but this is when you are driving at the maximum capacity.

Millipede, there are two way to go. Method 1. A driver is around 3A CC driver with around 36V max. Then you want to connect the 4x 100W COB LEDs in parallel. Each COB will get the current of about 750mA (there could be some variation due to slight difference in the forward voltage). If one parallel circuit dies for some reason, each will be getting 1000mA now. So this could end up overdriving the LEDs, but in this case, even 3 of them dies, the remaing 1 COB will get 3A, which is within its capacity (so it's safe).

Method 2: To avoid the problem of overdriving, people prefer to use serial connection. Then you want to get a low current driver (with high max voltage). For example, Meanwell LPC-100-700 is an example (700mA, 72-143V). You have to check the Vf of the COB at 700 mA is within 36V, though.

I started out with this type of Chinese COB LEDs, but it is a false economy. It is very inefficient compared with modern COB LEDs (Cree CXB, Bridgelux Vero etc). For a given amount of light (you can run CXB or Vero at a lower wattage than the cheap COB), Cree/Vero becomes cheaper than the cheap 100W COB in 1 year or so (after considering the cost of electricity). Check my post #15 for the comparison in this thread:
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At that time, I didn't have a PAR meter, so it is using fc, but I did make comparison with a PAR meter more recently.

 

[Av8tor1]

Based on his question and comments I assume he does not have a CC power supply, but a less expensive CV

in either case, overloading the wattage rating of a power supply will cause problems be it CC or CV

I may very well be wrong though, I would ask the mfg for their recommendations

 

[naoki]

Based on his question and comments I assume he does not have a CC power supply, but a less expensive CV

in either case, overloading the wattage rating of a power supply will cause problems be it CC or CV

I may very well be wrong though, I would ask the mfg for their recommendations

Oh, I didn't think that people would use CV supply, which can be done, but not a good idea.

I think you are misunderstanding the "power rating" of LEDs. This is usually the maximum power. So when people says 3W LEDs, they can handle up to 3W. There is nothing wrong with driving it with 1W or 0.1W driver. Most fixtures use the LEDs at 50% or so of the maximum power. The cheap fixtures will try to use the diodes near the maximum capacity (to reduce the cost) and sacrifice the efficiency. This is the reason why there is such a huge differences in the price and efficiency of LED fixtures.

With this kind of cheap COB LEDs, some people have run them at 350mA (about 10W) to gain a decent efficacy. Using 4 of "100W" COB LEDs with a 100W driver is doing the same thing (running each at 25W). That is the way this should be done. It is not overloading the power supply. It is "under-driving" the LEDs. For example, you can call Cree CXA3070 a "116W" COB LED because it is the maximum power manufacturer recommends. But I use it with a 50W driver (1.4A), and most people use drivers less than that to gain very good efficiency (most commercial grow lights can't achieve the efficiency of luxurious DIY builds).

Cree XLamp CXA LED Arrays: Highest Efficacy Lighting-Class LED Arrays

 

[pmatil]

+1 for naoki.

 

[Av8tor1]

Oh, I didn't think that people would use CV supply, which can be done, but not a good idea.

I think you are misunderstanding the "power rating" of LEDs. This is usually the maximum power. So when people says 3W LEDs, they can handle up to 3W. There is nothing wrong with driving it with 1W or 0.1W driver. Most fixtures use the LEDs at 50% or so of the maximum power. The cheap fixtures will try to use the diodes near the maximum capacity (to reduce the cost) and sacrifice the efficiency. This is the reason why there is such a huge differences in the price and efficiency of LED fixtures.

With this kind of cheap COB LEDs, some people have run them at 350mA (about 10W) to gain a decent efficacy. Using 4 of "100W" COB LEDs with a 100W driver is doing the same thing (running each at 25W). That is the way this should be done. It is not overloading the power supply. It is "under-driving" the LEDs. For example, you can call Cree CXA3070 a "116W" COB LED because it is the maximum power manufacturer recommends. But I use it with a 50W driver (1.4A), and most people use drivers less than that to gain very good efficiency (most commercial grow lights can't achieve the efficiency of luxurious DIY builds).

Cree XLamp CXA LED Arrays: Highest Efficacy Lighting-Class LED Arrays

And I think you're misunderstanding my comments, I am warning about the damage that can result to a power supply by running one overloaded or at full load for extended periods.

From "understanding LED drivers" by LEDSUPPLY.com

When calculating the appropriate power supply wattage for your project, it’s important to allow a 20% ‘cushion’ to your wattage calculation. Adding this 20% cushion will prevent the power supply from being over-worked. Overworking the power supply can cause the LEDs to flicker or cause premature failure of the power supply.

You have posted some really good information, but none of my comments were ever about damage or efficiency of the LED themselves.
Just addressing the OP question about 400w load on a 100w power supply, and while I agree about constant current, many of the economy LED kits over here are constant voltage.