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I have used isolated supplies while making optocouplers based drive circuitry for driving 6 IGBT switches in 3-phase VSI in my undergrad projects. I remember my professor kind of explained why exactly it was required but I kind of forgot the complete reason. I also remember at first using 6 isolated supplies for 6 switches and then reducing them to 4 as I learned from some application note which was probably from TI. Can anyone tell me what happens if I don't use isolated supply? Thanks in advance!

PS : I know there are other ways such as bootstrap drivers, but I'd really like to know what would happen if I supplied all optocouplers by deriving supply from a same transformer.

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  • \$\begingroup\$ draw a sketch of the various SOURCE/Emitter pins of your IGBTs. Now add the waveforms of those emitters. Are they compatible? \$\endgroup\$ Nov 19 '19 at 7:08
  • \$\begingroup\$ @analogsystemsrf Sorry but I didn't understand what you were trying to say, what requirement of triggering won't be satisfied if we do so.. I understand it might be something trivial but I am unable to figure it out, it'd be great if you can elaborate or refer me to some source. \$\endgroup\$
    – Deep
    Nov 19 '19 at 8:26

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