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I want to make a 5-level inverter using an H-bridge. I have made an H-bridge using MOSFETs and it works. My problem comes when adding the output of these two H-bridges to get 5 voltage levels. I am adding the outputs like we join two batteries in series but for some reason it is not working with my circuit. Can anyone help me with this?

Circuit in Proteus

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  • \$\begingroup\$ In effect you are connecting two parallel batteries but in antiphase and nothing good is going to happen from that. \$\endgroup\$
    – Andy aka
    Commented Jan 9, 2022 at 13:43
  • \$\begingroup\$ Do you have a reference where two H bridges can be connected to give a 5-level inverter? \$\endgroup\$
    – a concerned citizen
    Commented Jan 9, 2022 at 15:56
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    \$\begingroup\$ Do more reading Neutral Point Clamped (NPC), Cascaded H-Bridge (CHB), Flying Capacitor Converters (FCC), and Modular Multilevel Converters (MMC) \$\endgroup\$
    – D.A.S.
    Commented Jan 9, 2022 at 16:34
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    \$\begingroup\$ Have you mastered the 2 level converter yet? yumpu.com/en/document/read/18800114/… Do not skip ahead until you do. \$\endgroup\$
    – D.A.S.
    Commented Jan 9, 2022 at 16:43

2 Answers 2

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You cannot simply connect common-supply H-bridges in series. There is a common-mode return path through the supplies which shorts them out.

Isolated supplies (and gate drives, by extension) are mandatory.

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In case someone comes in future and sees it. You need to give negative voltage to gate of P-MOSFET instead of ground to turn it ON. Doing that will make it work.

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