The 2540's are almost double the rating, but that being said the die (both the same size) will have to cope with equally as much heat dissipation, so better cooling required.
I still think the 2520's are best bang for buck and my setup above only drives them to 63% of their rating. Use a pair of the 2520's on a 60W driver and I'm sure they would out perform a 2540 (at a similar price point).
I was confused by power supplies also, but then simplified it in my mind. This is not 100%, but you shouldn't blow sh1t up if followed.
Step 1 - Choose a constant current driver
Step 2 - Make sure the operating voltage range covers your LED forward voltage (Vf)
Step 3 - Add LED's in parallel summing up their current usage.
Step 4 - Try keep their working power 60 - 80% of their max rating
The reason for operating at lower than max rating is simple - efficiency and heat.
Stolen from another website....
For your example CXB3590 CB 36V @ 700ma VS CXB3590 CB 36V @ 1.4A
if 700ma 22.9 watts @ 58.71% efficiency 22.9 x 58.71% = 13.45 par watts / 9.94 heat watts
if 1.4A 48.85 watts @ 51.67% efficiency 48.85 x 51.67% = 25.24 par watts / 23.61 heat watts
So if you run twice as many COB's at lower current you get more PAR watts compared to running less COB's at higher current.
4 @ 700ma = 91.6 watts / 53.8 par / 39.76 heat
2 @ 1.4A = 97.7 watts / 50.48 par / 47.22 heat
- I have two 2520's (Vforward is 35V / Max power is 48W). I have two of these so max power is 96W
- I want to drive this to 60% of the rated 96W = 57W
- Typically drivers have a +- 5% tolerance so I choose a 50W driver for worst case (50W + 5% = 53W). Pretty close to the 57W I was aiming for.
- Check the driver's voltage range (35V - chosen one is 20-39V) so this will work.
- In this case I could have upped to a 60W driver and driven it to 71% of chip rating (I chose not to as 50W driver $12NZD and 60W driver $20NZD)
- I have one 2540 (Vforward is 36.2V / Max power is 84W)
- I want to drive this to 80% of the rated 84W = 67W
- Typically drivers have a +- 5% tolerance so I choose a 60W driver for worst case (60W + 5% = 63W). Pretty close to the 67W I was aiming for.
- Check the driver's voltage range (36.2V - chosen one is 20-38V) so this will work.
All this being said though the 50W driver I bought (being a generic) has a tolerance of +20% so the safety factors above play in well.
I will be testing the 2520's on the 60W driver when it arrives so will have an update in a week or two.
- I have three 500mm rigid strips of 5630smd that are rated at 12Vforward and 13W typical. I have tested these to 25W max (but then they get real hot real quick)
- I have a 50W driver with working voltage of 20-39V.
- I assume worst cast tolerance to 53W and divide by 3 (53 / 3 = 17.6W per strip)
- This is over it's typical, but under the tested max so should be ok.
- I connect them in series so add their Vforward together (12V + 12V + 12V = 36V). This is within the driver operating voltage so should work.
I have however played with the cheap 12V power supplies where you can change the output voltage from 11V - 14V and these are far cheaper than dedicated drivers to power rigid strips. They unfortunately are not constant current drivers though.
Edited by KAOS, 13 June 2018 - 03:16 AM.