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galleon
08/15/2016, 09:13 PM
Anybody have plans for building a driver that can deliver 3 amps for the CREE XM-L2s and run off of a (existing) Meanwell 48 volt/200 watt PSU?

Edit: I understand basic electronics and how buck converters work.

theatrus
08/16/2016, 12:50 AM
This is a good thread:

http://www.reefcentral.com/forums/showthread.php?t=2553733

You'd have to uprate some components to work on a 48V supply, but its quite possible.

The BOM is mostly in the thread - I can post the schematic as well:

https://oshpark.com/shared_projects/DgLzLrl6

theatrus
08/16/2016, 12:51 AM
I don't actively use this design, but I do have a spare board which is only fitted for 25V supplies.

BOM: http://i.imgur.com/iZcz8Br.png

The diode is incorrect for the PCB, you want a https://www.digikey.com/product-detail/en/vishay-semiconductor-diodes-division/V8P10-M3-86A/V8P10-M3-86AGICT-ND/2048231

Schematic: http://i.imgur.com/Se0pmgj.png

If you don't mind running at 48V with 50V capacitors just make sure you get the LM3409HV and the BOM as shown will work.

galleon
08/16/2016, 07:56 AM
Thanks!

Any thoughts on this build? The TI IC chip is dirt cheap... http://andrewpearson.org/?p=643#fn-643-10

The PSU I'm using is also adjustable, though I'm not sure how that would impact the available power. Which means this option from the thread you posted may be viable: http://store3.sure-electronics.com/ps-sp12153

galleon
08/16/2016, 08:12 AM
I don't actively use this design, but I do have a spare board which is only fitted for 25V supplies.

BOM: http://i.imgur.com/iZcz8Br.png

The diode is incorrect for the PCB, you want a https://www.digikey.com/product-detail/en/vishay-semiconductor-diodes-division/V8P10-M3-86A/V8P10-M3-86AGICT-ND/2048231

Schematic: http://i.imgur.com/Se0pmgj.png

If you don't mind running at 48V with 50V capacitors just make sure you get the LM3409HV and the BOM as shown will work.

This is a great great thread. Thank you. Digesting...

galleon
08/16/2016, 10:51 AM
I'm really liking the idea of doing this, I've never done my own PCB before, just breadboarding/prototyping. I don't see any of the resistors in your BOM?

mcgyvr
08/16/2016, 11:15 AM
Go on TI or linear or others sites and use their LED driver tool to pick one that fits your needs and more than likely the datasheet will have all the information you need on pcb layout/external components,etc..

Many of the IC manufacturers have design tools (web bench,etc..) that will spit out a complete schematic/BOM,etc... all ready to go.. Its almost easy now to do whatever you want..

galleon
08/16/2016, 11:50 AM
Go on TI or linear or others sites and use their LED driver tool to pick one that fits your needs and more than likely the datasheet will have all the information you need on pcb layout/external components,etc..

Many of the IC manufacturers have design tools (web bench,etc..) that will spit out a complete schematic/BOM,etc... all ready to go.. Its almost easy now to do whatever you want..

Awesome! Just registered at TI and started using Webench...

theatrus
08/16/2016, 12:05 PM
I'm really liking the idea of doing this, I've never done my own PCB before, just breadboarding/prototyping. I don't see any of the resistors in your BOM?

I'll dig up the order list. Missed the feedback resistors, only had the main sense resistor.

As for the TPS5430, its not designed to be a constant current driver (don't confuse the control mode - its referencing everything based on a voltage feedback pin). You can adapt a normal bucker converter into a constant current design, but you can also save yourself some design pain and use a CC designed chip to begin with :)

galleon
08/16/2016, 12:35 PM
I'll dig up the order list. Missed the feedback resistors, only had the main sense resistor.

As for the TPS5430, its not designed to be a constant current driver (don't confuse the control mode - its referencing everything based on a voltage feedback pin). You can adapt a normal bucker converter into a constant current design, but you can also save yourself some design pain and use a CC designed chip to begin with :)

Thank you!

Also. I just enrolled in the Ed-X MIT 6002 course thanks to this LED stuff. :lolspin:

This is what Webench gave me for an output voltage of 40-48V with a 3 amp LED of similar Vf as the XML2 (they didn't have it listed as an option).

https://c1.staticflickr.com/9/8171/28407239504_69a3e9e4ed_b.jpg
https://c1.staticflickr.com/9/8585/28407149464_f44f900a42_b.jpg

I'm guessing there is a way to add dimming to such a design since the IC itself is capable?

I'm also curious what you guys use to export these schematics to PCB designs and get prototype boards printed...

oreo57
08/16/2016, 12:45 PM
8.3.6 PWM Dimming Using the EN Pin
The enable pin (EN) is a TTL compatible input for PWM dimming of the LED. A logic low (below 0.5V) at EN will
disable the internal driver and shut off the current flow to the LED array. While the EN pin is in a logic low state
the support circuitry (driver, bandgap, VCC regulator) remains active to minimize the time needed to turn the LED
array back on when the EN pin sees a logic high (above 1.74 V).
Figure 25 shows the LED current (iLED(t)) during PWM dimming where duty cycle (DDIM) is the percentage of the
dimming period (TDIM) that the PFET is switching. For the remainder of TDIM, the PFET is disabled. The resulting
dimmed average LED current (IDIM-LED) is:
(15)
The LED current rise and fall times (which are limited by the slew rate of the inductor as well as the delay from
activation of the EN pin to the response of the external PFET) limit the achievable TDIM and DDIM. In general,
dimming frequency should be at least one order of magnitude lower than the steady state switching frequency to
prevent aliasing. However, for good linear response across the entire dimming range, the dimming frequency
may need to be even lower.

galleon
08/16/2016, 12:48 PM
Gotcha!!

theatrus
08/16/2016, 01:08 PM
Also, if you can provide a 0-1.2V output voltage, consider also using the IAdj pin. You can control the max output current in a pretty linear range which is in many way superior to PWM dimming (except at the very low currents, where you could combine them).

BOM looks good, feel free to adjust some parts (i.e. avoid 0402 parts).

My general process is:

- Re-capture the schematic and PCB layout. Eagle is popular since its well community documented, but pretty eclectic. I'm not sure Fritzing is up to the task, and KiCad suffers the Eagle problem. Others have used DIPTrace, CircuitMaker, etc.
(You'll likely need to build symbols and footprints for some of the parts)

- Do a 1:1 printout of your board copper layer to paper, buy the parts, and lay it out on the paper to make sure you bought the right parts that fit the board :)

- Get someone to sanity check things

- Do a manufacturing run of the output. OSHPark is great when you only want a handful (3-6) of boards. DirtyPCBs, PCBWay, etc are all good options for larger runs that end up being cheaper.

- I would strongly suggest using a reflow assembly method, especially since some of the parts (LM3904) has a center pad which can't be soldered by hand using an iron. For this, get some solder paste (Kester EM256, leaded is best for prototypes as its super reliable), and a cheap stencil from OSHStencil. You'll also need a defunct toaster oven, a skillet, or a hot air source (heatguns can work but can get pretty melty). You don't really need to modify the toaster oven or skillet (I like the skillet, cheaper and easier to see) with controllers, just watch the board carefully - once the solder is in the liquid phase everywhere, cut the heat :).

- Success!

You probably want to read some tutorials. SparkFun has an old one on SMT assembly.

O2Surplus
08/16/2016, 02:22 PM
Looking for an LM3409 based DIY Led driver PcB? There's a few in this old thread-http://reefcentral.com/forums/showthread.php?t=1759758&highlight=diy+led+driver

oreo57
08/16/2016, 04:30 PM
Try post 1853.............;)
http://reefcentral.com/forums/showthread.php?p=19169573&highlight=lm3409+eagle#post19169573

sorry, I'm just an enabler.. couldn't resist..

theatrus
08/16/2016, 04:47 PM
How things have changed in LED land in five years :)

Now its most people running series strings at 700mA-1A and using the super attractively priced LDDs ;)

I remember some of these threads from days back.

oreo57
08/16/2016, 04:56 PM
Well, higher amp and voltage PWM drivers will be needed as COB's like the Luminous Devices and Vero's start (well already have) beating 3W premium diodes out on pricing and output..
got to get them to not add phosphors so one can get "colored"..though not a large market for that.. ;)
Then again. who knows whats next or resurrected.. ;)
http://www.ledsmagazine.com/ugc/2014/10/01/lighting-solutions-development-offers-illumis-lights-driverless-led-modules-with-zhaga-form-factor.html

http://www.ledsmagazine.com/content/dam/leds/onlinearticles/2014/10/ledsillumislsdprod100114.jpg