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I'm looking for a bit of initial direction or input on a circuit to accomplish two relatively simple tasks: (1) automatic switching between a li-ion battery pack and 120VAC and, (2) supply multiple output voltage taps. I made up a rough diagram of what I'm thinking, which isn't technically accurate but hopefully explains my general plan. I'm really hoping to minimize the number of PSUs due to space (and cost), and if I could eliminate a battery charger that'd be great too. But, I've been unable to identify a li-ion charge circuit that would support my 12S battery design.

The power amp is the primary draw, and it has a wide voltage tolerance (25-50VDC) but requires a higher voltage to maximize the output. So, my thought is to design everything to supply as close to the 50VDC as possible and step down from there in order to power the other devices directly. There's also a 120VAC device that contains an internal PSU with multiple DC voltage taps, which I'm trying to determine how to power when on battery. Obviously I could use some sort of inverter, but I'm not sure how that would fit in to everything.

Any input, advice, or initial direction would be much appreciated! Diagram

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  • \$\begingroup\$ Please ask a specific question \$\endgroup\$
    – Voltage Spike ♦
    Commented Feb 17, 2021 at 16:22

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Looks in manufacturers catalog for oring controllers and battery backup switches (every brand has its cute name like TI eFuse, Linear PowerPath and so on). These are way better than the huge diodes you would need (some part even interfaces with the battery charger to help it).

As for the output side I agree with your plan. A main 50V rail for the power amp and the other rails from which step down the other branches is a good solution.

The 120VAC mixer is an exception, it makes no sense to step down to 50V and then invert it to 120VAC (a can of worms in itself), so I'd power it directly from the oring controller output.

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  • \$\begingroup\$ Thanks for the help, I'll definitely look in to the ORing controllers. I figured there had to be a better option than diodes, especially considering the reverse leakage which can reportedly cause some issues with the BMS metering. The biggest issues I've found with ICs like the PowerPath is the input voltage, most I've found are designed for 12V or 5V applications. I'll look a little deeper since that at least provides me with some direction, thanks! \$\endgroup\$
    – Cornelius Qualley
    Commented Feb 17, 2021 at 16:37

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