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I want to design a gate driver board to drive 6 SiC MOSFETs/PWR IGBT where the VBus can go up to 1200V. I need to use an isolated DC-DC power supply that can make dual bipolar rails (+15V/-8V) from a 15V input, something like the below image.

enter image description here

My first question: Is it necessary to use this approach, meaning all gate drivers are powered with individual isolated power supplies?

I used the formula below found in this document to calculate IGBT drive power and it came out to be 1.5W.

enter image description here

My second question: Is this method of calculating drive power for IGBTs right?

Then I looked into some reference designs for bipolar DC-DC power supplies for gate drivers but I didn't find any that matched my needs because most of them either have a custom-made transformer or a chunky and expensive one.

Here are some reference designs I found:

Isolated Push-Pull Power Supply Circuit

Isolated Bias power and Gate Driver daughter board

This one below actually looks like a good choice but the design is a four layer board with a high component count:

Isolated IGBT Gate-Drive Push-Pull Power Supply with 4 Outputs

If I have to go with this approach (all gate drivers are powered with individual isolated power supplies) I need to have a low cost, small-footprint power supply to go with the small form factor gate driver board I am designing.

Younes Thabet
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  • (It isn't just one dual-rail supply for the grounded transistors + 1 for each phase's high side: the latter better have low capacitance vs. GND, too.) – greybeard Mar 08 '23 at 15:30
  • (1) Yes, (2) didn't check, (3) I shouldn't encourage questions seeking recommendations and, (4) maybe. And, as Greybeard suggests, very low isolation capacitance is a must hence, they can become expensive (see Recom and Murata 5 kV isolating power supplies with 50 or 65 kV per micro-second dv/dt). – Andy aka Mar 08 '23 at 15:36
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    Removed the part about the suggestion since it might go against the rules. – Younes Thabet Mar 08 '23 at 15:44
  • @greybeard do you mean lower gate-drivers are powered with a common power supply and for each of the high-side drivers a separate power supply? Can you please elaborate on the low capacitance vs. ground part! – Younes Thabet Mar 08 '23 at 15:55
  • (Just a lay person here, and kW electronics not a sub-field of *keen* interest: know some of the questions to ask, and enough to not trust "any" of my answers.) Correct on the number of supplies, but questions shouldn't be answered in comments, and this question not by me. – greybeard Mar 08 '23 at 17:00
  • As shown in your diagram, the three devices sharing the same negative or low power rail, do not need specific isolation methods for each transistor because of the common position of their sources (if n-channel MOSFETs were used). I'm not making a formal answer because you've asked too many questions and certainly to my mind, the final one about the pulse transformer is really open to speculation and is best removed. May I suggest to concentrate on the isolated power supplies and associated drivers. – Andy aka Mar 08 '23 at 17:11

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