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TMS320F280039C: TMS320F280039C : TIDM DC-DC buck converter SFRA - doesn't create plot as expected

Geetha Priya Sivasankar
Prodigy 40 points
Part Number: TMS320F280039C
Other Parts Discussed in Thread: SFRA,

I'm trying to implement the TIDM Buck DC-DC Converter with TMS320F280039C control card with a few modifications as per our customized requirement. Vin, Vout, Iout - all seem to work properly with epwm frequency of 20KHz. When I try to run SFRA, with the settings shown below, the bode plot isn't displayed as expected. Though the Max. Frequency is set to 9.55KHz, the Magnitude plot shows a peak at 10KHz. And both the magnitude and phase plot are not limited to the set Max. Frequency of 9.55KHz and they extend beyond. Requesting help in resolving this and guidance on how the plot as shown in reference documentation could be produced.

  • 0
    TI__Genius 10506 points

    Hi Geetha,

    Did you make any changes to the SFRA-related settings when porting to F28003x family of devices?

    Regards,
    Peter

  • 0 in reply to Peter Luong1
    Prodigy 40 points

    Hi Peter,

    I didn't make any changes to SFRA settings at the time of posting this. Later, I made changes in the SFRA settings in buck_user_settings.h and the plot was correct, but the SFRA doesn't take values that are set in the GUI, instead when values are changed in buck_user_settings.h, it works. And this doesn't seem like porting issue, since the same issue is observed with the F280049 buck example as well. Could you please let me know how the SFRA could be run dynamically.

    Regards,
    Geetha Priya

  • 0 in reply to Geetha Priya Sivasankar
    TI__Genius 10506 points

    Hi Geetha,

    Can you let me know which values you have adjusted in your buck_user_settings.h file and resulting SFRA GUI properties? It seems your GUI is not updating from the information you set into the SFRA alone. Let me test the GUI on my side

    Regards,

    Peter

  • 0 in reply to Peter Luong1
    Prodigy 40 points

    Hi Peter,

    Below are the adjusted values in buck_user_settings.h , these are getting reflected on the SFRA GUI, but I would like to change it dynamically on the GUI, without changing the buck_user_settings.h , could you please help me with that.

    #define BUCK_SFRA_FREQ_START           ((float32_t)10)

       //
       // SFRA step Multiply = 10^(1/No of steps per decade(35))
       //
       #define BUCK_SFRA_FREQ_STEP_MULTIPLY   ((float32_t)1.0680004)
       #define BUCK_SFRA_FREQ_LENGTH          ((int16_t)75)
       #define BUCK_SFRA_AMPLITUDE            ((float32_t)0.005)
       #define BUCK_SFRA_SWEEP_SPEED          ((int16_t)1)


    Regards,
    Geetha Priya

  • 0 in reply to Geetha Priya Sivasankar
    TI__Genius 10506 points

    Hi Geetha,

    I replicated your setup in the SFRA GUI, from my testing, you should be able to dynamically set the maximum frequency. The margins on the GUI don't look to update automatically when you change this settings from the GUI, but if you hover over the plot component, you can see the correct frequency in the Frequency text box

    Regards,

    Peter