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UCC256404: UCC256404

Stuart Linzer
Intellectual 260 points
Part Number: UCC256404


Hi Tech Help, 

UCC256404 data sheet section 8.2.2.8 LLC Transformer shows the following:

Primary terminal voltage:450 Vac

Secondary terminal voltage: 36 Vac

Please define "terminal voltage" and where these values come from or how they are calculate.  

Regards, 

Stuart

  • 0
    TI__Genius 16155 points

    Hi Stuart,

    Thanks for reaching out. I have reached out to systems engineer regarding your question. I will let you know once I hear back from him. He will give response by Tuesday.

    Regards

    Manikanta P

  • 0 in reply to Manikanta Pallantla
    TI__Genius 16155 points

    Hi Stuart,

    Here is the response from our systems engineer:

    "For the UCC25640x application example, I assumed that the resonant capacitor has an initial voltage of 0V before the LLC begins switching and when the high side first turns on, there would be almost 400V across the primary pins of the transformer. 450V peak was with some margin on top of this number. Keep in mind this was considering the use case where the leakage inductance is used as Lr.

     

    For the secondary terminal voltage, I used 2x the output voltage since the EVM was using a center-tapped rectifier and added some margin on top to account for ringing."

     

    So, the primary and secondary voltages that were mentioned in the datasheet are peak values not the RMS values.

    Please let me know if you have any further questions. Thank you.

    Regards

    Manikanta P