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Original question:

TMS320F28388D: EPWM sync in tms320

TMS320F28379D: Configuring epwm's with different counter modes

Vijaymahantesh Surkod
Intellectual 301 points
Part Number: TMS320F28379D


I am configuring PWM's for a phase shift converter and an active snubber. I am able to generate a proper phase shift between leading and lagging leg with the up-down counter mode. For this I have used epwm 4 and epwm 5 (running at 50kHz). Now in order to generate pwm for an active snubber, I want to use epwm 6A (at a frequency of 100kHz). The question I have is, can I use down count mode of same TBPRD value (as I had used in epwm 4 and epwm 5 but in up-down mode) so that I get a 100kHz and use a synchronisation select for synchronising the counters. Is this feasible to use up-down mode for epwm 4 & 5 and down mode for epwm 6 while maintaining the synchronisation.

Thank you

Vijaymahantesh V Surkod 

  • 0
    TI__Mastermind 23870 points

    Hi Vijaymahantesh,

    You should be able to use different count modes to produce similar EPWM signals, but may have to alter the TBPRD depending on this and how you are syncing your EPWMs to match frequencies.

    Would you be able to send a diagram of the PWM signals you are trying to produce so I can better understand the target configuration?

    Best Regards,

    Allison

  • 0 in reply to Allison Nguyen
    Intellectual 301 points

    Hello Allison,

    The PWMs I require are shown below, where EPWM4 and EPWM5 are for a PSFB converter input H-Bridge (regular Phase shift operation with each PWM at 50% duty and a phase shift between 4A and 5A while 4B and 5B are complimentary to 4A and 5A respectively) (50kHz operation). However, the PWM for the active snubber switch that I want is shown in EPWM6A, which is at 100kHz. 

    So I was thinking If I can use the below strategy to generate EPWM 6A i.e Up-Down counter for EPWM4 and EPWM5 and for EPWM6 I thought of using a down counter of the same TBPRD value but the counter itself if phase shifted by 25% so that the rising edge of the counter coincides with the rising edge of EPWM4A.

    What do you think about this?, is this possible to do in TMS320F28379D?

    Thank you

    Vijaymahantesh V Surkod

  • 0 in reply to Vijaymahantesh Surkod
    TI__Mastermind 23870 points

    Hi Vijaymahantesh, 

    This is achievable with the EPWM module.

    One way you could implement this is how you drew it out by sourcing a sync signal from EPWM4 CTR=0. This sync signal looks like it is also used in EPWM5 to phase shift, so you can just select the EPWM5 sync-out signal (sourced from EPWM5 sync-in) to become the EPWM6 sync source (meaning EPWM6 is syncing on EPWM4 CTR=0).

    I sketched out a basic down-count example (though up-count would also work) with some arbitrary values for better visualization- and if you have deadband on EPWM4A then you would have to adjust your TBPHS and CMPA accordingly. Hope this helps! Let me know if you have any follow up questions.

    Best Regards,

    Allison