Electronics > Projects, Designs, and Technical Stuff

power supply woes

(1/4) > >>

KTP:
I just added up the power supply requirements of the RGB led boards I am making and calculated worst case with each led element on full at 50mA, 1/6 duty cycle I will be drawing 3.6 amps at 5V (if I use 5V as the drive voltage for the allegro driver chip).  Ok, the kicker here is I need 80 boards...er, worst case then for each element of each RGB led fully on would be 288 amps at 5V!  :o

Since I want to power these off of at most 4 strings of cables, that would be almost 60 amps per cable...very beefy.

Sooo....I am thinking about incorporating a 24V to 5V dc-dc converter chip on each board, figuring that at 80% efficiency, I reduce the current to a more manageable 1 amp per board and 20 amps per each of the four strands.

The problem is I am having difficulty finding a dc-dc converter chip that can handle 3.6 amps and only requires a few external components.  Plenty that handle 3 amps, and some really expensive ones that handle 5 or 10 amps.  I also would like it to be adjustable such that maybe I supply the led driver with a bit less than 5V to limit waste.  I am looking at the LM2576 but it is only 3A.  http://www.onsemi.com/pub_link/Collateral/LM2576-D.PDF

Suggestions?

Chasm:
Can you split the power supply on the board even more?
RGB, three converters. - but that is also getting expensive, fast.


Did you seee the TPS5450?

Psi:
what kind of price range are you looking for?

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MC34167TVGOS-ND

Internal FET but you're still going to need diode and of course inductor.

KTP:

--- Quote from: Psi on January 17, 2011, 02:12:15 am ---what kind of price range are you looking for?

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MC34167TVGOS-ND

Internal FET but you're still going to need diode and of course inductor.

--- End quote ---

Thanks.  I missed that one because I filtered the 17,000 converters at digikey with "in stock" and "smt" and the smt version of that part is non stock.  I'd like to keep the total cost of the converter under $5 including catch diode and inductor, so that one fits the bill I think.  The whole board is getting really expensive (144 RGB leds, xmega micro, 6 allegro serial shift register drivers, RS485 communications).  My wife wants 80 of these boards....sheez.

Psi:
Another option is to buy prebuilt dc/dc modules, you can get quite cheap ones considering they include the ic, inductor, diode and all other passives.

This one is 4.5v-13.8v input and 5V at 10A output (almost enough to run 3 of your boards with one module)
Effieiency is good too over 90% when load is 5A and above. Worst case 75% at 1A load
and it only costs  $9.50  or $7.6 in qty above 50

http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=507-1384-ND



That exact model is probably not an ideal choice as you want 24V input but it looks to be cheaper and easer to run 2 or 3 boards off something like this than build a psu on each board yourself.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks WYSIWYG Editor
Powered by SMFPacks Advanced Attachments Uploader Mod