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  • TI Thinks Resolved

TMS320F28035: EPWM duty match while CBC occurs

Part Number: TMS320F28035

Hi C2000 expert,

I'm trying to use F28035 in HSFB topology with PCMC control algorithm.

Now I'd would like to know if this device support duty match or not?

For example, if epwm1A and epwm1b are connected to primary side mosfet, epwm2a, epwm2b are used to control sencondary side mosfet. If CBC occurs on EPWM1A, i would like EPWM1B have same duty cycle with EPWM1A, is it possible to relized?

Below is the waveform what I want, CBC occurs on EPWM1A, EPWM1B should keep the same pulswidth with EPWM1A, is it possible? Thanks...

Regards,

Jack

  • Jack,

    I am looking into this. In your system, will the CBC trip always occur before ePWM1B is high? If so approximatly how long before?

    Regards,
    Cody 

  • In reply to Cody Watkins:

    Code,

    Regarding to HSFB topology, the pulse width of ePWM1A and ePWM1B are clamped within 50% duty, otherwise it will cause MOSFET damaged. 

    If there is no CBC while ePWM1A output 50% duty cycle, then ePWM1a just output 50% duty clcle, and epwm1B should have the same pulse width.

    Regards,

    Jack

  • In reply to Jack Tan80:

    Sorry for the typo, you're cody.

    Cody,

    Regarding to HSFB topology, the pulse width of ePWM1A and ePWM1B are clamped within 50% duty, otherwise it will cause MOSFET damaged.

    If there is no CBC while ePWM1A output 50% duty cycle, then ePWM1a just output 50% duty clcle, and epwm1B should have the same pulse width.

    Regards,

    Jack

  • In reply to Jack Tan80:

    Cody/C2000 expert,

    Can you please help update about this?

    Regards,

    Jack

  • In reply to Jack Tan80:

    Edited 1/12/18/ 2:52 PM CST.

    __________________________________________________________________

    Jack,

    due to the asynchronous nature of the CBC trip this would be difficult to predict within the PWM module. There are two ways around this.

    • Setup up the Digital Compare Counter Capture Register (DCCAP) to indicate the falling edge of ePWMA. That value can then be used to update the CMPx values for ePWMB.
    • Setup an eCAP module to measure the pulse width of ePWMA then use that measurement to set the CMPx values for ePWMB.

    Note: When making symmetric waveforms it is often helpful for you to use up-down-count mode!

    Regards,
    Cody 

  • In reply to Cody Watkins:

    Jack,
    I am closing this thread due to inactivity feel free to reply here if the question is not answered.
    Cody

  • In reply to Cody Watkins:

    Cody,

    Sure, you can close this thread. We have added a external exponent to fixed this instead of inside the chip. Thanks anyway.

    Regards,

    Jack

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