Please let me know if this belongs in another sub-forum.In a previous
post I asked about designing a DC-DC battery charger. I haven't made progress there as life has gotten in the way. Lately, I've been thinking about the other end of the DIY UPS, powering the load. I'm currently using a separate inverter. But all the gear I'm running runs on DC internally. So, I'm thinking about taking the SLA battery bank (~9-15VDC), doing some DC-DC conversion, making some cables and just get rid of the inverter.
I've looked at the things I need to power:
* Four devices use wall warts that output 12VDC. I have appropriate connectors for all of them. Adding up the current on the wall warts says I'll need a max of 12A at 12V. But I measured the average in use power for these devices together they total about 2.5A
* My switch has an AC/DC PSU internally, it outputs 54VDC and is rated for 1.1A/60W. There's a single connector from the PSU to the mainboard of the switch, and it's a Molex Micro-Fit Jr (I asked the PSU maker for dimensions)
* My consumer NAS box has PC-like PSU inside, I need to open it up to check, but I think it's going to be an PC ATX connector. The easiest thing is to buy a DC-DC ATX PSU module. These typically take 12V or 24V in. I haven't checked this PSU specs, but this is probably 300W max, about 100-150W average.
I'm looking for advice on how to architect the conversion. It comes down to:
Power source is 9-15VDC.
I need to provide a peak 150W at 12V, but only about 30W continuously.
I need to provide 60W at 54V
I need to provide peak 300W, continuous 100-150W at something like 12V or 24V depending on what DC ATX PSU I find.
A simple approach is to find variable input DC converters that all use the battery as input and output the needed voltage (12V, 54V, etc). Doing some reading, I've come across the idea of using an intermediate voltage IBA. So I could step up the battery voltage to something like 60V, then step down for each output I need to provide. The advantage here I think is that each point-of-load step-down (I think I'm using that term correctly) only has to deal with a fixed input voltage and fixed output voltage, so they are simpler devices. Also, current between the initial step-up and the various step-downs in pretty low.
Is one approach better than the other? If I use the intermediate voltage, what guides the decision for that voltage? 48V seems like a common intermediate voltage, but it seems simpler to me to have a single step up that is higher than all the needed outputs so I'm only using step downs for each output. Not sure if this matters.
When I build this, I'm going to wire it up as separate modules in an enclosure. But eventually, I'd like to design a PCB that replaces this. Not sure if that matters when giving advice, but thought I would mention it.
Thanks for any help!