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CCS/TMS320F28035: Carrier-based PWM with external modulating sine wave

Balakrishna Balakrishna
Prodigy 10 points
Part Number: TMS320F28035
Other Parts Discussed in Thread: CONTROLSUITE,

Tool/software: Code Composer Studio

Hi All,

As shown in the below figure, I need to generate 6 PWM signal (Ta1 -Ta6) with an external modulating sine wave. I have TMS320F28035 control card and I have gone through examples projects available in controlSuite. But I am not able to find a solution to my requirements as the PWM duty cycle from the control card is fixed and not varying throughout the modulating signal cycle, due to duty cycle is dependent on TBPRD register.

However, in my requirement there are multiple duty cycles within the the modulating signal cycle as shown in below. Now my questions are

1)How can I generate the multiple duty cycles PWM within the the modulating signal cycle?

2)Initially I am planning to generate the modulating signal using internal look up table, can I able to generate sine wave in TMS320F28035 control card? because I have not seen any signal generation libraries or sample signal examples in the controlSuite.

3)If TMS320F28035 control card is not suitable for my requirements, then could you please suggest me the suitable device to full fill my requirement.

4)I have simulated the requirement in simulink, but I tried to load the program into the control card , however, PWM blocks are not having any inputs.

Therefore, I request you to provide me suitable solution and kindly let me know if you need any further information.

Regards!

Bala

  • 0
    TI__Mastermind 42195 points

    Bala,

    if you wish to update the PWM's frequency you can simply change TBPRD, we of course recommend using shadow loads however immediate loads are also available.

    To answer your questions directly as I can.

    1. You can update the PWM's period(and subsequently its frequency) at any time by adjusting TBPRD. Each PWM has it's own independent TBPRD value, this allows you to independently adjust PWM1's frequency from PWM2's frequency.
    2. The PWMs are a digital module and output 0v or 3.3v. They will not simply output a sine wave. It should be possible to generate a sine like waveform using a combination of PWMs and filters however we don't have an example of this in controlSuite.
    3. The F28035 controlCard should be a good debug test bed. It needs to be stated that the controlCard was not intended for, and should not be used in a commercially available application. This is an evaluation module only.
    4. The best place to get simulink support is from the mathworks' forums, Brian McKay is well versed in C2000+Mathworks software.

    Regards,
    Cody 

  • 0 in reply to Cody Watkins
    Mastermind 9005 points

    Basic info on MathWorks C2000 support is available here: https://e2e.ti.com/support/microcontrollers/c2000/f/171/t/484814

    There are posts in these forums with MathWorks + TI C2000 questions and answers - you can search to find them.

    Finally, you can contact MathWorks Technical Support if needed.

    Cheers,

    -Brian