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Topic: PWM and its logic level inverse (Read 521 times) previous topic - next topic

TheWyliestCoyote

Hello,

I am building basically some thing like a AC motor controller, the design uses a full H-bridge to generate alternating current. I have 2 problems I cant figure out. First is I need a PWM signal, easy part, but I also need its logic level inverse, can I do this all inside a atmega328 or equivalent or do I need an external inverter. I would like very much to minimize the parts count. Second is how much trouble is it to change the PWM frequencies on the program end of thing and when the chip is on and running.

Thanks

Coding Badly

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can I do this all inside a atmega328


Not well.  You would have to do software PWM.

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or equivalent or do I need an external inverter


Better choice.

Or, some ATtiny models have inverted output with "dead-time generator".


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Second is how much trouble is it to change the PWM frequencies on the program end of thing and when the chip is on and running.


Depends on the frequency.  Changing the "prescalar" is trivial but the frequency changes are rather dramatic.  It is possible to fine tune the frequency but there is potentially some lost resolution.  In other words, it all depends on the details.

Grumpy_Mike

You need a TC4428, it is two half H-bridges with inverted inputs so you just connect the two inputs to the same pin.
If you need more current than this will provide then use the outputs to drive another pair of FETs.

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