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Original question:

TIDA-01604: Blanking Interval in EPWM

TIDA-01605, Blanking interval during zero-crossing in Totem-Pole PFC

Pranav Ananthakumar
Prodigy 170 points
Other Parts Discussed in Thread: TIDA-01604

Hello all,

I am using EPWM1A and EPWM1B to switch the totem-pole leg. Since they are being used in complementary mode with active high complementary deadband, how do I provide a blanking interval at zero-crossing as suggested by TI in various documents? Attaching the document here also. I am detecting zero-crossing based on my ADC values using the Post Processing Block.slyt718.pdf

  • 0
    TI__Expert 4200 points

    Hi,

    TIDA-01604 user guide also include how it suppress zero crossing distortion. Please check page 12 of  the document (https://www.ti.com/lit/pdf/tidue54)

    This reference design detects zero crossing based on PLL not directly from ADC measurement and can be different from what you are looking for.

    Best,

    John

  • 0 in reply to John_K
    Prodigy 170 points

    Hi,

    I am aware and I understand how the switching scheme has to be implemented. I wanted to understand which registers I should specifically set in the ePWM module to provide a blanking window. Since I am using active high complementary deadtime and set my action qualifiers in complementary mode, even if I use the AQSFRC register to blank my PWM I get a complementary PWM. Can you suggest any specific registers which can help me blank the PWM while such configurations have been set?

  • 0 in reply to Pranav Ananthakumar
    TI__Expert 4200 points

    Hi,

    By setting DBRED and DBFED to PWM period, ePWM output become low for both high side and low side. Check pfcControlCode in pfc1ph3ilttpl.h.

    SET_PWM_DBRED(HIGH_FREQ_PWM1_BASE,PFC_PWM_PERIOD);
    SET_PWM_DBFED(HIGH_FREQ_PWM1_BASE,PFC_PWM_PERIOD);

    SET_PWM_DBRED(HIGH_FREQ_PWM2_BASE,PFC_PWM_PERIOD);
    SET_PWM_DBFED(HIGH_FREQ_PWM2_BASE,PFC_PWM_PERIOD);

    SET_PWM_DBRED(HIGH_FREQ_PWM3_BASE,PFC_PWM_PERIOD);
    SET_PWM_DBFED(HIGH_FREQ_PWM3_BASE,PFC_PWM_PERIOD);

    If you want to enable ePWM output, set DBRED and DBFED to the nominal deadtime.

    Best,

    John