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TMS320F28035: Phase shift FB PMC

ol
Intellectual 480 points

Part Number: TMS320F28035

Hello,
I tried the PSFB PMC software tool. I adapted it to my board and it works well except at low current.
I mean that under a certain amount of current voltage control can not regulate the output voltage. It is probably due to a problem of detection of the peak current because its shape is very "flat".
How to lower this current threshold? Can we recover the angle between the two PWMs and force it to a value in a low current area, a bit like in VMC? but how ?
Thank you for your help
Regards,

OL

  • 0
    TI__Genius 16085 points

    Hi,

    I don't quite get your question in terms of "How to lower this current threshold? Can we recover the angle between the two PWMs and force it to a value in a low current area, a bit like in VMC? but how ?"

    Could you please explain what happens in your case with very light load condition?

    Regards,

    Chen

  • 0 in reply to Chen Jiang ti
    Intellectual 480 points

    Hi,

    The trouble is at very light load. The current is then very small and voltage regulation is no more able to maintain the reference value. So, the output of the voltage increase up to over-voltage protection detection. I have to check but it seems that current is very small and peak become unreachable for peak control. So I would like to check peak detection and also angle between phase.

    If peak current  is not detected at very small current, how to maintain voltage regulation working properly ?

    Regards,

    Ol

  • 0 in reply to ol
    TI__Genius 16085 points

    Hi OL,

    If the peak current is not well detected or the peak current is coupled with some low frequency oscillation/noise, then it is extremely difficult to control for PCMC. 

    Regards,

    Chen 

  • 0 in reply to Chen Jiang ti
    Intellectual 480 points

    Hi Chen,

    I solved the problem, I placed filter on voltage feedback and now it works well.

    Thanks,

    OL