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Original question:

TMS320F280049: CMPSS + EPWM Peak Current Mode Control (PCMC) Configuration for Phase-Shift Full-Bridge Converter

TMS320F28379D: How to utilize HrPWM for PSFB with peak current mode control

Mingyu Xue
Prodigy 40 points
Part Number: TMS320F28379D


Hi Team,

I cannot use HrPWM for the peak current mode control of PSFB. The switching frequency is 100kHz so that the PWM resolution is only 10ns，leading to limit-cycle oscillation. 

The reason why HrPWM cannot be enabled is that the 200MHz clock signal is used to synchronize the output of comparator of CMPSS module.

Hope to hear from you soon. Thanks.

Br.,

Mingyu Xue

  • 0
    TI__Mastermind 28230 points

    Hi Mingyu Xue,

    Could you provide more details on your desired PWM configuration? What PWM output are you trying to achieve that you believe is not possible using HRPWM?

    Thank you,

    Luke

  • 0
    Prodigy 40 points

    Hi Luke,

    Thanks for your reply.

    I use T1 event to control epwm AQ module. The T1 event stems from CMPSS→CTRIPH→X-bar→EPWM DC module→DCAEVT1. The DB module is used. To prevent an asserted comparator trip state in one PWM cycle from extending into the following cycle, I clear the COMPxLATCH 10 clk prior to the end of the PWM cycle with PWMSYNCPER signal. Then COMPCTL[CTRIPHSEL] should be set to 3.

    Thanks again.

    Br.

    Mingyu

  • 0 in reply to Mingyu Xue
    TI__Mastermind 28230 points

    Hi Mingyu,

    HR resolution is supported for CMPA events but not T1 events. Is this why you say HRPWM cannot be used? Or is it because there is no HR support for CMPC or CMPD? I am not familiar with "limit-cycle oscillation". 

    Thank you,

    Luke

  • 0
    Prodigy 40 points

    Hi Luke,

    "HR resolution is supported for CMPA events but not T1 events. Is this why you say HRPWM cannot be used?"-- Yes, that's what I  mean. The limit cycle resonance can be simply interpreted as there isn't PWM that fine enough to regulate the output, so that the output jumps between the adjacent levels. 

    In order to utilize HrPWM for PCMC, I've assessed two candidate solutions. 1. Use the trigger signal produced by the comparator to generate PWM through the logic module. But once LUT is employed in logic module, the synchronize clock will hinder HRPWM; 2. Use the trigger signal produced by the comparator to generate PWM through the AQ module, while dead band is realized with external RC circuit. However, if it is also indispensable for a PWM clock, then HrPWM may still be invalid.

    Br,

    Mingyu

  • 0 in reply to Mingyu Xue
    TI__Mastermind 28230 points

    Hi Mingyu,

    The CLB and action qualifier modules are synchronized to TBCLK, however the trip-zone module is asynchronous. Have you looked into whether the trip zone module can be used to meet your requirements?

    Thank you,

    Luke

  • 0
    Prodigy 40 points

    Hi Luke,

    Sorry for late reply.

    The trip zone works at the switching frequency. However, what I need is the trip zone has to work at twice such frequency.

    Can you suggest a dedicated DSP for PSFB using the peak-current-mode control? Thus not only the PWM logic bust also the PWM resolution are satisfied.

    Thanks.

    Mingyu

  • 0 in reply to Mingyu Xue
    TI__Mastermind 28230 points

    Hi Mingyu,

    Unfortunately there is no C2000 device that offers the HR functionality you are describing, since the EPWM module is mostly identical across devices. HR resolution can only be applied to predefined duty cycles and periods, not after a T1 event.

    Thank you,

    Luke