You need to convert ~12v to 5v and you need a lot of current.
You also want high efficiency, and you'd like to be able to power them down completely to avoid the ~1ma-per-led quiescent current..
While perusing buck converters, I came across this, and was immediately curious... It's about $10 a pop.
http://www.prodctodc.com/dc-1014v-to-255v-15a-buck-converter-peak-20a-high-current-power-supply-p-121.html
also on Ali-express
http://www.aliexpress.com/item/5-PCS-LOT-DC-Buck-Converter-15A-10-14V-to-2-5-5V-Peak-20A-High/558859436.html
Rated at 20Amps, ideal for a large car/deep cycle lead-acid battery.
Seems like rather a fancy module on there, no? Well.. it sure is!
Eyeballing the part number it's actually a really high quality DC-DC converter module; the Artesyn "SIL40c-12sADJ-VS", now obsolete.
http://www.artesyn.com/power/assets/lf_sil40c_1208906885_techref.pdf
The module is actually rated at 40A continuous output with 92% efficiency, low ripple, and all the bells and whistles you could want. Datasheet mentions 18.5A input (@12v) = 222W in and 40A @5V = 200W out, which is 90%, so only about 20W dissipation at full power. Very nice. Spec-wise this is far superior to all the other cheapo DC-DC buck converters from china, and a very good price at that.
The modules also support 'current sharing' as well as remote on/off, it's also _very_ well regulated to handle very rapid surges in current (i.e. all your LEDs going from off to on!), and so on.
Caveat: It's possible the modules they're using are rejects but we'll see. They may just available b/c the module's been discontinued.
The three chips on the underside of the host board are a slight mystery; the two on the left look like reverse-polarity protection diodes on the input [update: no, they're P-FETs, only 2mv drop!] (which I plan to bypass, not wasting my precious juice on them), the other in the middle... not sure yet [update: LM393 comparitor] The module datasheet implies it's basically ready-to-rock as it comes, with only external smoothing caps.
Note that the module sheet suggests 2000uf output caps for 5v and these have only about 1200-ish, but should be ok.
I'll give more feedback when mine arrive... Excited!
UPDATE 1: DOH! The no-load current is like 290ma @12v!!!! WTF!? Gets toasty just doing nothing. Not so impressed any more. Also at 1.8A output I measured 1A/12.5V in = only 72% efficient.
UPDATE 2: Ok so the specs do mention the high quiescent current if you look closely, and if you can live with that the modules work very well; the load regulation is excellent. It turns out the module does happily output well over 20A (tested at 30A - active cooling a good idea, the small heatsink gets literally hot enough to boil water; thermal cutoff is at about 120C(!) ) - however - the board the module is mounted on has a P-FET for reverse voltage protection on the input and that blows up (quite spectacularly; lets the magic smoke out) above about 15A input current. If you don't care about the protection you can bypass the fet with some (very) thick wire from the input terminals to the module and it works well at very high currents.
Overall it's a pretty good module as long as you're ok with max 13.8v input and wasting a fair bit of power as heat...
