Anything wrong with this PWM generation model?

[Walter Roberson]

This question uses included images fairly effectively.

I would, though, suggest in future, to make the actual questions text rather than an image, and to make the commentary on the settings to be text rather than images. That would make the question more comprehensible for those who have images normally turned off (e.g., if they are using dialup), and would allow people whose native language is not English to copy and paste the sentences in to a translation tool.

[Nirmal Gunaseelan]

I agree with Walter. I really like the usage of images and with the questions in text, it'd perfect.

Answer 1

[Nirmal Gunaseelan]

I see that you changed the solver and zero-crossing settings and presume you have read through the various options and consequences of zero-crossing settings.

I have not tried changing the settings in your model, but I think that the time step settings you have hard coded makes the solver to probably miss the zero-crossing event? Could you try with a fixed-step solver under default settings to see what happens for a comparison?

Answer 2

[onemilimeter]

Thanks Nirmal.

The simulation results shown in my first post were prepared using MATLAB2009b.

I built the same model using MATLAB v7.0.1 (R14SP1) and did not encounter the same problem.

Kindly share if you know the reason that cause the abnormality in the model built in MATLAB2009b.

[Nirmal Gunaseelan]

I'd not be surprised by the version changes because solvers are constantly being changed.

Answer 3

[onemilimeter]

Hi Nirmal...

The following is the simulation results when fixed-step solver is used. The simulation model is implemented using MATLAB2009b. With fixed-step solver, the output of the "Repeating Sequence" block is Okay (i.e. not distorted).

[Nirmal Gunaseelan]

Thanks for trying out. So essentially, the variable-step solver is missing the zero-crossing point. I'm not sure of the reason until I play around with the settings, I'd implore you to check the link in my previous answer and try out the options.