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TIDM-DC-DC-BUCK: upper switch missing pulses

Shengnan Li
Expert 1010 points
Part Number: TIDM-DC-DC-BUCK

Hi,

I adapt TIDM-dc-dc-buck to control a boost converter. This problem happens at close loop voltage mode. Basically, it can regulate from 48V input to 65V output. but I notice some bumps in the output voltage. Zoomed in, I noticed that upper PWM signal is missing in some duration, it can be from 1 switching period to 4 switching period, while the lower PWM signal is correct. I am wondering why, it should appear as a pair. 

Deadtime is not set for boost mode, because the gatedriver can provide deadtime.

In the waveform below, purple is upper switch PwM, yellow is lower switch PWM. Blue is output voltage.  

 

  • 0
    TI__Expert 4200 points

    Hi,

    Can you share how you configure ePWM modules especially the dead band configuration?

  • 0 in reply to John_K
    Expert 1010 points

    Thanks for the reply. deadband module is not configured at all for this ePWM module.

  • 0 in reply to Shengnan Li
    TI__Expert 4200 points

    I guess using the deadband module is the convenient way to generate complementary switching. How do you implement complementary switching on your system? This can help figure out the root cause.

    Best,

    John

  • 0 in reply to John_K
    Expert 1010 points

    Hi, John,

    Thanks for looking into this, I set up the action for outputB and outputA individually as following:

    //This is to set turn on of outputB, outputA is complimentary 

    EPWM_setActionQualifierAction(BOOST_DRV_EPWM_BASE,EPWM_AQ_OUTPUT_B,EPWM_AQ_OUTPUT_HIGH,EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);
     EPWM_setActionQualifierAction(BOOST_DRV_EPWM_BASE,EPWM_AQ_OUTPUT_A,EPWM_AQ_OUTPUT_LOW,EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);

    //this is to set turn off of output B, outputA is complimentary
    EPWM_setActionQualifierAction(BOOST_DRV_EPWM_BASE,EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_HIGH,EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);
    EPWM_setActionQualifierAction(BOOST_DRV_EPWM_BASE,EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_LOW,EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);

  • 0 in reply to Shengnan Li
    TI__Expert 4200 points

    I'm closing this as the issue was covered in the other thread.

    Best,

    John