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UCC25600: LLC converter, 120Hz output ripple,

kwnag woon Lee
Prodigy 170 points
Part Number: UCC25600
Other Parts Discussed in Thread: UCC256403, UCC28951, UCC256303, UCC27511A

I am developing a 2kw ac-dc converter.

I configured the LLC converter using ucc25600 and the 120Hz ac rippe appears in the DC output.

How can I reduce 120Hz output voltage ripple of LLC converter?

Best regards.

  • 0
    TI__Expert 8210 points

    Kwnag

    To reduce the 120Hz voltage ripple on the output the bandwidth of the feedback loop needs to be increased.  This app note http://www.ti.com/lit/an/slua582a/slua582a.pdf explains how to optimize the feedback loop with UCC25600.

    Alternatively we have newer controllers that can have better performance than UCC25600

    • UCC256403: this is our latest LLC controller, which has hybrid hysteretic control (HHC) which enables much greater transient response.  The following app note has more details on what HHC is http://www.ti.com/lit/an/slua834/slua834.pdf
    • UCC28951: at 2kW our half bridge resonant LLC controllers (UCC25600, UCC256403) performance may be limited.  We recommend that you consider our phase shift full bridge (PSFB) controller UCC28951 instead since it can support higher power levels better.  This controller also achieves zero voltage switching so it has the same efficiency and EMI benefits as resonant LLC

    Best Regards,

    Eric

  • 0 in reply to Eric Faraci
    Prodigy 170 points

    Thanks for your advice.

    I am trying to change the design from LLC Controller to UCC256303.

    Since it's a 2kw design, it seems to lack the mosfet driver ability, so I want to add an external driver.

    If I connect the HS pin to ground, I think there is a problem with adaptive dead time.

    Is there a way to connect an external driver?

    Can adaptive dead time be applied by connecting the HS pin to the switching node and using a single output driver like

    ucc27511a?

    There is a lot of development going on, so it's hard to change the topology.

    Best Regards,

  • 0 in reply to kwnag woon Lee
    TI__Expert 8210 points

    Kwnag

    First off we recommend that you use our latest LLC controller UCC256403.  This device is pin to pin compatible with UCC256303 and has several features that improves performance.  Details of these improvements are in the following app note http://www.ti.com/lit/an/slua966/slua966.pdf

    In order for both UCC256303 and UCC256403 to work correctly the HS pin must be connected to the switch node.  If you need an external gate driver to increase gate drive strength, we recommend that you use the internal gate driver for level shift and use a low side driver that meets your current requirement, just as you proposed.  A table of all low side gate drivers that you can use to select the right one for your design is available here http://www.ti.com/power-management/gate-drivers/low-side-drivers/products.html#p480=1;1

    Best Regards,

    Eric