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TIDM-02010: Impact of Removing EPWM_setPeriodLoadMode on PFC Current Loop Behavior

Ankit Saxena
Prodigy 210 points
Part Number: TIDM-02010

Tool/software:

Hi Experts,

We are using a reference design for our PFC proof-of-concept (POC). However, after removing the EPWM_setPeriodLoadMode function call to enable access from the shadow register, we observed unexpected oscillations in the current waveform. Since we have not modified the actual PWM period, we are trying to understand how this change is affecting the system.

Below is a code snippet from hal.c, specifically the HAL_setupPWMsPFC function, where we made this modification.

Could you provide a detailed explanation of how EPWM_setPeriodLoadMode works and how its removal could lead to oscillations in the current waveform?

Thanks!

  • 0
    Prodigy 210 points

    Additional Note: In PFC application, the PWM period remains constant throughout the operation cycle. Therefore, we set the PWM period only once during initialization and retrieve it using the EPWM_getTimeBasePeriod function, which operates independently of the period load mode.

    We would appreciate your help in bridging our understanding gap regarding how the period load mode affects system behavior in this scenario.

  • 0 in reply to Ankit Saxena
    TI__Mastermind 43196 points

    Hi Ankit,

    I don't see how TBCTL.PRDLD would have any effect if you keep TBPRD static. Do you have PWM and current waveforms you can share to show if any issue can be seen?

    Best,

    Kevin