View Full Version : SMPS LED Switching power supplies in parallel....

03-17-2016, 12:53 AM
Ok, so I apologize if this has already been discussed. I looked but I couldn't find anything like it.

I am currently building/trying to build, 2 power supplies. One is a 60amp and one is a 90amp. I am going to use the SMPS power supplies found on eBay for around $30. They are regulated so they should work fine on my AB biased amps. And they are surprisingly stable under heavy load, even close to their amperage limit. The supplies I am using are 12v 30A supplies. They are individually regulated. Ive been doing quite a bit of research on running these in parallel to increase the amperage. Each being 30a, so one supply will have two of these units producing 60a, and obviously the other will have 3 units producing 90a. I also have learned that in order for these to play along nicely with each other they must be set to as close to the same voltage as possible. They have a small pot that allows for voltage output adjustment, and it seems to be pretty good. I was able to set 2 of the units to within .01V of each other just playing around. 15.20v seems to be the usual limit on these FYI.

My questions are as follows;

1. I have heard that in order to run these in parallel, they must first run through a Isolating Diode, like the one found on RV charging systems. Apparently these will prevent the units from trying to fighting with each other, who gets to produce the current, and making sure they are sharing the load and one not shouldering all the burden. Are the absolutely necessary? And where can they be found for something not resembling the price tag of a pre-built PS. lol They are crazy expensive everywhere Ive looked.

1b. On the 60a supply I am assuming that I only need one of these isolators..? But on the 90a supply, since it has 3 units, is there an isolating diode with three inputs? Or do i use one I.D. and wire the third unit up directly to the hot buss?

2. Do i need any kind of filter caps in this build or can I simply run the + voltage to a power buss and then to the output stud? I have also seen that these SMPS supplies can have noisy DC power. I had read that building a simple filter using 4700uF caps (x6) would eliminate any noise. True or unnecessary?

3. Since these are switching supplies and are pretty dang stable under load, do I need to run them into a 47000uF/56000uF cap like you do with linear PS's?

I'm fairly new to this PS building thing as you can probably tell. I GREATLY appreciate any help or comments. Thanks for a warm welcome to the Site as well guys. I included a picture to make sure its clear the kind of SMPS I'm talking about.