• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 82 subscribers
  • Views 193 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

F28377D-SEP: PWM

Reshma M
Prodigy 40 points

Part Number: F28377D-SEP
Other Parts Discussed in Thread: TMS320F28388D

Hi,

I'm working on TMS320F28388D MCU for my application. I have gone through the TRM and the datasheet for the same. 

I am working on three-phase active front end PFC and I want to generate pwm duty with phase difference present between the legs.
U, V, W legs of my 3-phase have same switching frequency and they only differ by the phase. 
To get the phase resolution of the pwm, the formula that I have understood from TRM (pg 2988) is 360/total prd. Is that the min phase difference that i can give between the legs without HRPWM?

With HRPWM, will the formula change to 360/(total prd*256), since there are 256 bits?

Please advice.

Regards,
Reshma.

  • +1
    TI__Expert 7690 points

    Hello,

    The minimum phase-shift step is 1 TBCLK count, so the phase resolution depends on the ePWM count mode and the effective PWM period in TBCLK counts, not just on a fixed “360 / PRD” expression. For example, in up-count mode, one full PWM cycle is approximately TBPRD TBCLK counts, so the phase resolution is about 360 / TBPRD degrees. In up-down count mode, one full PWM cycle is approximately 2 * TBPRD TBCLK counts, so the phase resolution is about 360 / (2 * TBPRD) degrees.

    As for HRPWM, the MEP comes after sync-in pulse in block diagram. Meaning, it actually won't help minimum phase-shift and 1 TBCLK count goes for HRPWM too.

    Best Regards,

    Masoud

  • 0 in reply to Reshma M
    Prodigy 40 points

     I have made a table for worst case scenario when I use a 20KHz PWM for both edge and center aligned pwm. Can you please verify if my understanding is correct?