Looking for a specific DC CC driver for LEDs

[karimwassef]

I can usually find these things, but this time, I'm stumped.

I'm looking for a DC-DC driver with constant current at 120W:

DC in = 36VDC
DC out = 32-34VDC
Constant Current
I max = 3500mA (or higher)
P max = 120W (or higher)
Dimmable 0-10V (preferred but any electronic dimming is ok)

I can go with any multiple of 12VDC for the input too (12V or 24V or 36V or 48V). I prefer the 36VDCin since that should be the most efficient with 36Vin, 34Vout (max duty cycle).

I think these should be ~$10 based on the description and the components I could do it for. The AC input versions run $30-$50 depending on the vendor, so just having the DC CC driver section should be less.

Anyone know where to get these things? Does anyone make them? I need 20 - assuming they're not fictional.

[chimmike]

like this?

http://www.meanwellusa.com/product/led/LED.html#module

[karimwassef]

which one is 3500mA and 34V?

[chimmike]

don't see one there, but it sure looks like you want something similar to those that I posted to put out 3x the mA they do.

i'll dig some more.

[theatrus]

For a DC/DC solution a driver can be pretty easily built on the Allegro A6211 up to 3A, which is the highest current integrated switch controller I've seen (external switch is always possible with more design effort).

http://www.allegromicro.com/en/Produ...ing/A6211.aspx

What LEDs are you planning - multichip?

[karimwassef]

the closest I got was 2100mA

[chimmike]

here's something close-ish

http://store3.sure-electronics.com/ps-sp12153

http://www.ledsupply.com/led-drivers...-dc-led-driver

best I could find

[karimwassef]

Originally Posted by theatrus

For a DC/DC solution a driver can be pretty easily built on the Allegro A6211 up to 3A, which is the highest current integrated switch controller I've seen (external switch is always possible with more design effort).

http://www.allegromicro.com/en/Produ...ing/A6211.aspx

What LEDs are you planning - multichip?

Thanks. Still 500mA short

I also need 20, so that's a lot of soldering.

[karimwassef]

Originally Posted by chimmike

here's something close-ish

http://store3.sure-electronics.com/ps-sp12153

http://www.ledsupply.com/led-drivers...-dc-led-driver

best I could find

Thanks. I found the LuxDrive, but didn't know if it could boost from 32Vin to 34Vo.

The Sure Buck looks close... so close. It doesn't say that it can run 34Vo.

[theatrus]

Do you really need to run all the way to 3.5A? Derating curves usually make that less appealing.

Don't worry, my build has 32 drivers

[karimwassef]

Yes. I have forced liquid cooling to maintain the LED temperature at ~40C even at a full load of 34V 3.5A. I will only be running 100W really at 34V = 2950mA. But if the driver is only rated to 3000mA, I would need to derate its application to 2700mA...

There's 10-12 on each fixture for 1000W-1200W.

[theatrus]

The 3A limit is over the speced temp range. With good thermal control 4A operation could be possible.

[karimwassef]

Thanks theatrus. Maybe I can buy their demo boards. I need 20, so I don't see making 20 circuits.

Yes. Each feeds a multichip LED.

In case this helps... I have a constant voltage AC/DC supply that generates 36V at 75A (2700W).

I have 20 multichip LEDs that need 34V at 3A each (100W) = 2000W total.

I'm missing the constant current DC-DC drivers in between. I would like each to be individually controllable.

[oreo57]

Originally Posted by theatrus

For a DC/DC solution a driver can be pretty easily built on the Allegro A6211 up to 3A, which is the highest current integrated switch controller I've seen (external switch is always possible with more design effort).

http://www.allegromicro.com/en/Produ...ing/A6211.aspx

What LEDs are you planning - multichip?

This might work, but it is up to you to translate the geek speek..

http://cds.linear.com/docs/en/datasheet/3955fb.pdf

[karimwassef]

Oh. My budget for the DC-DC portion is about $200 (for all 20). If there's a better way to do it, I'm all ears.

I already have the power supply (unexpected recovery from another DIY) and the LEDs are on the way.

I was going to use these HLG-120H-36B (http://pge.powergatellc.com/product_...oducts_id/1253) until I got the 2700W power supply from the other project.

[theatrus]

Originally Posted by oreo57

This might work, but it is up to you to translate the geek speek..



http://cds.linear.com/docs/en/datasheet/3955fb.pdf

Note that it's a boost topology, so Vin would have to below the target. Linear makes awesome parts at a nice premium.

For more plug and play, Meanwell HLG series supplies would be more plug and play but not cheap for the number of required channels. They come in various powers, here is the 150W:

http://www.mouser.com/ds/2/260/HLG-150H-SPEC-806071.pdf

[karimwassef]

Originally Posted by oreo57

This might work, but it is up to you to translate the geek speek..

http://cds.linear.com/docs/en/datasheet/3955fb.pdf

I can design a circuit around a chip, but this is where I draw the DIY line.

I need a whole driver, not the IC.

[oreo57]

Originally Posted by theatrus

Note that it's a boost topology, so Vin would have to below the target. Linear makes awesome parts at a nice premium.

For more plug and play, Meanwell HLG series supplies would be more plug and play but not cheap for the number of required channels. They come in various powers, here is the 150W:

http://www.mouser.com/ds/2/260/HLG-150H-SPEC-806071.pdf

But can it output 3.5A constant current..?

Besides:

Drives LEDs in Boost, SEPIC, CUK, Buck Mode,
Buck-Boost Mode, or Flyback Configuration

you didn't read it very well..
And they're $5 each...
http://www.linear.com/purchase/LT3955

[karimwassef]

Originally Posted by theatrus

Note that it's a boost topology, so Vin would have to below the target. Linear makes awesome parts at a nice premium.

For more plug and play, Meanwell HLG series supplies would be more plug and play but not cheap for the number of required channels. They come in various powers, here is the 150W:

http://www.mouser.com/ds/2/260/HLG-150H-SPEC-806071.pdf

Yes - see above. This is what I was going to do if I needed to start from AC input. I already have 36V DC.

The 120W version I was going to use is ~$50. For 20 channels, that's $1000.

Since I already have the AC-DC part, I just need the DC-DC CC driver.

[karimwassef]

Originally Posted by oreo57

But can it output 3.5A constant current..?

Besides:


you didn't read it very well..
And they're $5 each...
http://www.linear.com/purchase/LT3955

The MeanWells can put out a lot of current. These 150W put out 4.2A at 36V. The 120W version puts out 3.5A at 36V.

But they're $50 a pieces.

So the AC input power supply/drivers are $50.
The ICs are $5-$6.

I need the DC-DC driver only at $10-$11

[theatrus]

Originally Posted by oreo57

But can it output 3.5A constant current..?

Besides:


you didn't read it very well..
And they're $5 each...
http://www.linear.com/purchase/LT3955

I can - it can be used in this mode, but I'd take a look at the reference designs. It's going to require an external PWM low side switch and over current protection circuitry. Your raw BOM cost is much higher.

Raw cost of the A6211 is <$1: http://www.digikey.com/product-detai...7-1-ND/3597453. A shunt is still required, but you can drop a number of external parts.

[oreo57]

http://www.linear.com/product/LT3791
different variation on the theme...


The IC "is" the driver..
Look, to be honest, I'm only throwing out what "looks" to be quite possible for you. Others better at this "stuff" needs to follow up..

The LT®3791 is a synchronous 4-switch buck-boost LED driver controller. The controller can regulate LED current up to 52V of LED string with input voltages above, below, or equal to the output voltage.

[theatrus]

Originally Posted by oreo57

http://www.linear.com/product/LT3791
different variation on the theme...


The IC "is" the driver..
Look, to be honest, I'm only throwing out what "looks" to be quite possible for you. Others better at this "stuff" needs to follow up..

No integrated switches, so current is up to the 4 FETs chosen. This is the controller / external switch design I alluded to. More complex to design with of course.

[oreo57]

And the Allegro can do 3.5A??
Don't care how cheap it is if it can't do the job..or if I have to drop $3 worth of copper onto it (just in general terms. not my $'s)
You stated above "possible".. How possible to run at 3.5A


this stuff is all above my pay grade.. but if saving $4 is what is at stake here, and by running a chip off spec.. well have at it.

To help the op poster out, say you use the LT chip, what is an est cost per assembled driver?

And My first question was could one regulate 3.5A wasn't answered either..
I'm doing my own lern-in.

I'm not asking for a semester of basic electronics here..

BTW I am well aware that things usually are not "simple" but no need to make it purposely obtuse..

from a naive standpoint, I can't see a driver built around that chip (3955, like you said the other one has external MOSFETS) costing much more than the requested $10.. Well let's go to $15.
and a drive built around the Allegro? w/ heatsink.. $5

Lets stick w/ the 3955.. Looks easier (and cheaper) to design around.

[theatrus]

Originally Posted by oreo57

And the Allegro can do 3.5A??
Don't care how cheap it is if it can't do the job..or if I have to drop $3 worth of copper onto it (just in general terms. not my $'s)
You stated above "possible".. How possible to run at 3.5A


this stuff is all above my pay grade.. but if saving $4 is what is at stake here, and by running a chip off spec.. well have at it.

To help the op poster out, say you use the LT chip, what is an est cost per assembled driver?

And My first question was could one regulate 3.5A wasn't answered either..
I'm doing my own lern-in.

I'm not asking for a semester of basic electronics here..

BTW I am well aware that things usually are not "simple" but no need to make it purposely obtuse..

It's possible, assuming several things:

- Low thermal resistance on the board. This is hard to predict without seeing the design.
- Frequency chosen (lower will reduce switching losses, but also require a larger inductor)
- Ambient temperature remains low enough.
- switching ratio. The requested regulation ratio is ideal here for maximum efficiency.

FWIW I would not casually recommend pushing the driver in the design unless you are familiar with the basics of designing buck regulators. It *can* be done and enough information is available in the data sheet to calculate it out from the looks of it.

Another consideration for the OP: what is the true maximum current your LED can take? The output of a buck converter has non trivial levels of ripple current which may exceed your stated current limit. This is something that can be controlled via an output capacitor with trade offs.

As for cost, all in including (small qty) PCB my LM3414 8-up design runs about $5 a channel, with up to 1A drive per channel.