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UCC25600: Need help with Full bridge LLC converter design with UCC25600

Sidd Bhattacharya
Prodigy 145 points
Part Number: UCC25600
Other Parts Discussed in Thread: UCD3138

Hello,

I am designing a 3.3 kW full bridge DC-DC converter for automotive applications (input voltage 540V and output 28V)  and I need feedback on design.  We are using a UCC25600 for resonant controller and need some feedback regarding our design. Who is the right person to talk to about this? I would like  send my design and PCB by email for your feedback if that's possible. Your kind support is solicited. 

Best.

Sidd

  • 0
    TI__Mastermind 31580 points

    Hi Sidd,

    The UCC25600 is supported by our team in the US who are currently on Thanksgiving holidays, they will be back in the office on Monday and will reply then.

    Regards

    Peter

  • 0 in reply to Peter Meaney
    TI__Guru* 77535 points

    Hello Sidd,

    The UCC25600 was optimized for half bridge LLC design.  I am not sure what external circuitry would be required to get it to run in an LLC full bridge.

    However, I know that the UCD3138 was used in a resonant full bridge converter.  The following link will get you to a reference design using this converter.

    http://www.ti.com/tool/TIDA-00381?keyMatch=LLC%20FULL%20BRIDGE&tisearch=Search-EN-everything

    If you are interested in using the UCD3138 with your LCC full bridge design please re post to the e2e so someone from the UCD3138 team can help you with your design.

    Regards,

  • 0 in reply to Mike O'
    Prodigy 145 points

    Hello, 

    Thank you for your reply. I am kind of determined to make use UCC25600 ( also due to internal reasons :) . If this fails I will look into  UCD3138.

    Actually I managed to use the controller to work in a FB configuration. 

    Please refer to the attachment where I uploaded the schematics. I would like you to please take a look and comment if I missed something. Going back to your original answer, what kind of potential problem do you see in this design. 

    Additionally,  I discovered a problem :  that even though I put a frequency range if 70- 140 KHz , the controller does not hit the upper limit. I have measured maximum of 110kHz from the controller. How can I fix this? You kind support is solicited. Thank you. 

    TI _ upload.pdf

  • 0 in reply to Sidd Bhattacharya
    TI__Guru* 77535 points

    Hello,

    I reviewed the schematic and it looks like you are driving to half bridge drivers to form a full bridge. Once of the half bridges has the GD1 and GD2 swamped.  One side of the H Bridge will achieve ZVS.  I am not sure about the side with the swapped inputs.  Most likely this will be hard switched.  This is where the UCD3138 would be a better option.  Both sides of the H Bridge would have ZVS.  However, if you are happy with the performance it is O.K. to use the UCC25600 instead; as long as, it meets your requirements.

    The UCC25600 should be able operate from 40 kHz to 350 kHz based on the modulated RT current through an opto isolator.  I would try an open loop circuit with a variable resistor on the CT pin.  You should be able to vary the frequency from 40 kHz to 350 kHz.

    Regards,