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This is one of my very first schematics, so there'll probably be a lot of silly mistakes and it would be really helpful if someone could check it for errors and advise me on what I have to improve.

I'm trying to implement a DC/DC module that converts the input voltage of a 6-cell LiPo battery (about 22-24 V) to 12 V and 5 V power buses. I have a load of 200 W for the 12 V bus and 100 W for the 5 V bus.

I found these two Murata DC/DC converters. I also tried to implement reverse polarity protection, but I'm not sure of the ratings.

And I'm not quite sure if I wired everything correctly at all.

Should I add input or output LC filters or something else? If you check and give me some tips I'll be happy.

Datasheet for 5V converter: https://www2.mouser.com/datasheet/2/281/uws-33607.pdf

For 12V: https://www2.mouser.com/datasheet/2/281/MDC_UWQ-12-17-Q48T-C.A01-1186248.pdf

enter image description here

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    \$\begingroup\$ The 5V flyback converter you want to use has lower output power than required. Do you really need isolated outputs? Regular buck converters will be cheaper and less complex. \$\endgroup\$
    – Lars Hankeln
    Commented Dec 26, 2021 at 7:18
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    \$\begingroup\$ You could make that schematic so much more accessible to viewers on small devices by basic simple redraws. \$\endgroup\$
    – Andy aka
    Commented Dec 26, 2021 at 10:01
  • \$\begingroup\$ For example: i.sstatic.net/p2pDM.png \$\endgroup\$
    – Andy aka
    Commented Dec 26, 2021 at 10:08
  • \$\begingroup\$ Alan - Hi, As commented, you deleted the schematic from the question, but with no explanation about why. Therefore, initially, I have reversed (rolled-back) that edit. If you want to delete the question, there is more info here. Please add a comment to explain what's going on and we'll take it from there. \$\endgroup\$
    – SamGibson ♦
    Commented Jan 8, 2022 at 5:08

2 Answers 2

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I don't see much wrong with it, a little confusing why you would need the fuses. Another way (more complex way) to implement current protection would be to detect the current with an analog circuit and cut enable line if the current get's too high. With the battery you also may want to consider a regular DC/DC converter because the design is probably already isolated (with the battery). (isolated supplies are useful for generating positive and negative rails, but it appears that this is not happening)

If you are worried about the device turning into an unintentional radiator you may want to add common mode chokes to the output, input or both (if you need to reduce the peak to peak noise on the rails chokes are also useful):

enter image description here Source: Isolated DC-DC common mode choke without shunt?

Also, it would probably be a good idea to place the 0.1uf cap close to the DC DC converter and the electrolytic further away (because of parasitic inductance in the copper traces will reduce the 0.1uf caps filtering).

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  • \$\begingroup\$ especially C3 should be added unless @Alan connects Vin directly to GND or uses non-isolated converters instead. \$\endgroup\$
    – tobalt
    Commented Jan 8, 2022 at 7:01
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What do the specs say for the voltage on CTRL? Why the fuses? The fuse is to protect the wire, not the load so what value are the fuses adding?

As for input and output filters, it depends. What are the standards you need to comply with? You probably don't need to worry too much about input filtering as the battery won't care and the wiring is probably short.

For the output, is the load worried about noise? Is the wiring long that it might radiate significantly? Have you found that the converters radiate too much and you need to quiet them down?

Do you really need isolation on a battery powered system? You're paying a premium for that isolation that you probably don't need.

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