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UCC28950-Q1: Current transformer polarity

Joseph Francis S
Prodigy 130 points
Part Number: UCC28950-Q1
Other Parts Discussed in Thread: UCC28950

Tool/software:

Hi Team,

Can I reverse the polarity of current transformer in secondary side alone. Will it affect the functionality.

If not could you please let me know why.

  • 0
    TI__Guru* 80466 points

    Hello,

    In general they recommend that you put the current transformer (CT) in front of the H Bridge in the primary.  If you put it in series with the transformer there can be issues durring large signal transients where the DC information is lost and will cause instablities.

    In regards to putting the CT in the secondary alone, I am not sure what you are thinking.  If it is in serisies with the transformer you possibily will have the same issue as stated above.

    I do think that you can control the design on the secondary with two CT networks.  Each CT inputs would be in series with the SR FETs.  You would need two CT configuations with one current sense resistor.

    Regards,

  • 0 in reply to Mike O'
    Prodigy 130 points

    Hello Mike,

    I am not using the CT in seondary side of phase shifted ZVT.

    I am planning to use the CT in front of H-Bridge in primary side of phase shifted ZVT only. The clarification I need is in recommended application circuit in UCC28950-Q1 CT, current was entering in dot polarity in primary side and secondary dot polarity was connected to RC and then to CS pin.

    In my circuit, current entering in dot polarity of primary of CT and  the CT secondary side dot polarity was connected to ground and other end was connected to CS pin. Whether it cause any issue or not.

  • 0 in reply to Joseph Francis S
    TI__Guru* 80466 points

    Hello,

    If you change the input polarity of the CT on the primary you have to change the CT polatory connections on the secondary side as well.

    The following link will bring you to an application note that goes through the design process of a phase shifted full bridge converter using the UCC28950.  There is a section on how to setup the CT.  You can use this for guidance in setting up your current sense transformer.

    https://www.ti.com/lit/pdf/slua560

    Thank you for interest in Texas Instruments (TI) products.  If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

    Regards,