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I have just started learning about inverters. The following diagram has been intriguing me for the past few days:

enter image description here

Apparently, this inverter works if some PWM is applied to the MOSFET gates.

I would like to know if there is any way to make this inverter work without the PWM. If not, is there any other way to make an efficient inverter without the use of ICs or PWMs?

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    \$\begingroup\$ Maybe a dynamotor? No semiconductors involved at all. \$\endgroup\$
    – Kartman
    Commented Sep 14, 2021 at 6:36
  • \$\begingroup\$ @Kartman I think that might be a good idea. With a dynamotor I can get pure inducted sine waves. Thanks! \$\endgroup\$
    – Octonions
    Commented Sep 14, 2021 at 12:06
  • \$\begingroup\$ Without PWM you'll get a "Modified sine wave" inverter. Which means ... not quite a square wave, but a 3-step staircase, -V, 0V and +V. Cheap and does nasty things to some types of load. \$\endgroup\$
    – user16324
    Commented Sep 14, 2021 at 13:20
  • \$\begingroup\$ @user_1818839 is it possible to “smooth it” using capacitors? \$\endgroup\$
    – Octonions
    Commented Sep 14, 2021 at 14:35

2 Answers 2

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Can this H-bridge inverter work without the PWM?

Yes, but only if a modified square wave output is appropriate for your load. Also note the the output is floating wrt ground (no ground).

Can you generate 50, 60 or 400 Hz without a PWM drive with ICs?

Yes, easily. You can use a ferro-resonant transformer which is tuned to the required frequency. This can be driven by a square wave and produce a sine wave (10-15% distortion) output. The frequency can be pulled by several percent with only a modest increase in distortion.

enter image description here

There is an interesting set of Youtube videos on Ferro-resonant transformers that may pique your interest, though this is mostly about producing regulated AC.

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The answer to your question "will it work" depends on requirements. If you want to drive your load with square wave (including all the harmonic frequencies producing EMI noise) then yes. Beware that an H-bridge may fail catastrophically if you open the two transistors on one of the sides concurrently. There are chips to prevent that and to properly bias the gate of the high side FET. A good old example I remember is IRS2001 (and similar).

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