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Inverting or non-inverting buck-boost converter, does it matter in this case?

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David_

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Hello.

By now it was quite a while ago but I have been talking about building a high-current mcu controlled vaporizer before, here is a schematic(please note that this is now no longer valid at all, it wasn't ever finished but now it is completely scrapped), all the different coloured dashed lines isn't relevant to this question, I used it to ask about current paths so just ignore them. I only show this to give you an idea of what sort of circuit the question i regarding, but instead of a buck-converter running from 2 series Li-Ion cells the new design need to be able to use ether a single cell Li-Ion or 2 series cell Li-Ion(2,7V - 4,2V or 5,4V - 8,4V), so a buck-boost converter are required:
MOD_Return_issue.png

So while working towards implementing a 4-switch non-inverting buck-boost converter I thought "why couldn't I use a much simpler inverting buck-boost converter?".

And I am somewhat unsure about the results, but why wouldn't a inverting buck-boost converter work here?

Feedback needs to be taken from a resistive feedback divider and the current need to be measured, both those signals need to be read by the µC's 12-bit ADC, so some level-shifting circuits would probably be required.

Without even knowing how to accomplish those level-shifts yet I want to ask for opinions about the suitability for a non-inverting vs a inverting buck-boost in this case, is there any clear choice if one where trying to make it easier to design/implement?

Regards
 

It does matter. Inverting buck-boost involves large inductor and most likely higher switching losses. Please review this previous thread https://www.edaboard.com/showthread.php?t=375125

I still believe that supplying a resistive heater by a full featured DC/DC converter is a case of over-engineering. Design the heater coil to give sufficient power with lowest available battery voltage, use pwm for higher battery voltage.
 

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