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I am designing a 3-phase three-level NPC converter (same type as: https://trinhquocnam.files.wordpress.com/2015/12/t-npc.png?w=767&h=434).

The box this converter will be placed into is fed with 48V (for the control signals). I would like to take this 48V, step it down to 12V (with a DC-DC converter, probably), and power all 12 of the gate drivers that are necessary for this 3-phase setup.

Currently, our design uses 12 dedicated DC-DC converters, but they are pricey ($35/piece) and this solution doesn't seem "clean" to me.

Is there a way to take this 48V, step it down (preferably only once), and send it to all of the gate drivers? I was thinking using pulse transformers may work, but I would like to see the opinions here.

Thanks a lot!

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Upon NPC configuration you may save 3 DC-DC.

If your layout is TNPC i.e. your neutral switches ( horizontal branches) are made by two anti-series IGBT with their emitters joined then each couple can share one single DC-DC (and probably gate drivet too).

Other possible topologies unfortunately cannot.

Being connected to negative bus-bar you may also be tempted to use one single DC-DC for your low side switches. This should be really avoided though, the emitters stray inductance would otherwise l kill your di/dt

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  • \$\begingroup\$ So the way I'm looking at it now, depending on how I set up the neutral-point MOSFETs (using MOSFETs instead of IGBTs), if the sources are common, then one power supply can be used for both of them, so we can reduce the amount of DC-DC converters by 2 (since only one is needed for all 3 of the phases). Also, you said to avoid it, but since I'm using MOSFETs, could only one DC-DC converter be used on the low side switches (since all the sources are common)? \$\endgroup\$ – Lerbi Aug 18 '17 at 18:04

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