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TIDM-1000: Inductor voltage drop feedforward

Part Number: TIDM-1000
Other Parts Discussed in Thread: TIDM-02013

Hi,

I don't quite understand this part of the inductor voltage drop feedforward,the screenshot of the program is as follows

I looked at other thread but didn't get an answer that solved my doubts.


Can you help explain how adding this feedforward item(L*di/dt) will help with control?

What aspects of performance can be improved by this function?

Are there any relevant documents that can be provided for study?

Looking forward Your explanation.

regard,

  • Feed forward terms are used to predict what will happen and react before the thing occurs. In this case it appears to be predicting a voltage drop at the inductor due to the step size of the inductor current reference. Using this information it is and trying to compensate proactively rather than reactively.

    https://en.wikipedia.org/wiki/Feed_forward_(control)

    The above wiki describes it simply with a house. The idea is that when a door opens you know the room's temperature will drop. In this case you can use feedforward control by turning on a heater when a door opens rather than waiting for the thermostat to provide feedback that the room's temperature has dropped.

    In this analogy, similar to the voltage-drop compensation above, can lead to greater stability of the controlled parameter by reacting before the feedback path's delay.

    Regards,
    Cody 

  • Have you verified this function? Could you show me the waveforms?


    Are there any side effects or should I pay attention to adding this function?

    Because I also found this function in the totem pole pfc of TIDM-02013, but the voltage drop feedforward term was not added to the calculation of duty.

  • I did not personally verify this function, I'll see what I can find, but I don't expect to have any waveforms.

    Side effects that I would look for would be over/under compensation due to the FF term. In this case it looks like the FF term is just trying to preemptivlely move the PFC's duty down to the reference. I believe this is just to help track the reference more closely, with less phase delay.

    Correct TIDM-02013 did not utilize the FF term. The power factor was acceptable, so this was not evaluated.

    Regards,
    Cody