I am building a power selecting/splitter module and would like to ask if there are any glaring ommisions or reccomended additions to the system.

I have two inputs which will get connected at the same time or either one of them depending on the setup. If the 24v one is present it should have higher priority so I am using an MBR2045CTG Switch Mode Power Rectifier to select the higher voltage.

As outputs, firstly the unregulated output of the rectifier, and then I would need 12v and 24v. The values don't have to be exact on the decimal point. For that I plan on using two LM2587 Auto Buck Boost boards set to the respective values.

The LM2587: https://www.amazon.com/Converter-Electrical-converters-Regulator-DCCON-MS8/dp/B00LGJ48AC/ref=sr_1_3?ie=UTF8&qid=1482500052&sr=8-3&keywords=LM2587

Do you have any suggestions to improve the circuit? Maybe diodes for each output? Voltage suppressors for the buck boost? Caps?


enter image description here

  • 1
    \$\begingroup\$ That schematic you linked is worthless to answering this question. \$\endgroup\$
    – Andy aka
    Dec 23, 2016 at 14:10
  • \$\begingroup\$ You need the schematic of the buck boost right? \$\endgroup\$
    – drSnap
    Dec 23, 2016 at 15:02
  • \$\begingroup\$ You asked about the "power selecting/splitter module". \$\endgroup\$
    – Andy aka
    Dec 23, 2016 at 15:59
  • \$\begingroup\$ The MBR2045CTG is simply two diodes with a common cathode, so it's a bit of a stretch to call it a "power selecting/splitter module." \$\endgroup\$
    – Edward
    Dec 23, 2016 at 16:08
  • \$\begingroup\$ That is correct. I was describing the whole schematic as it's purpose is to select the higher voltage and to split it into unregulated and regulated outputs. It works, the question is if there are any improvements or safety features that could/should be added. \$\endgroup\$
    – drSnap
    Dec 23, 2016 at 16:38

1 Answer 1


Whenever you're thinking about fuses, it's useful to answer the question, "What are we protecting?"

With that in mind, I think I'd be inclined to separately fuse each of the two inputs and omit the one that's currently (if you'll pardon the pun!) shown. The reasoning is that it's reasonable to assume that each of those supplies could be capable of supplying considerable energy, so a short within your circuit could cause the wiring between your circuit and the supply to get very hot -- hot enough to start a fire.

With the original arrangement, the fuse would do nothing for that situation.

I'd also be inclined to move the fuse to just the Vunreg output just in case it might accidentally become the voltage input to the regulators. This would depend on what you're going to be connecting on that line. If it were, say, just a panel voltmeter, I probably wouldn't bother.

  • \$\begingroup\$ The Vunreg output is where the most power will be drawn from, up to 8A while the regulated outputs should supply up to 2A so it makes sense to move the fuse, yes. \$\endgroup\$
    – drSnap
    Dec 23, 2016 at 17:48

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