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UCC24610 used in synchronous LLC

Other Parts Discussed in Thread: UCC24610, UCC25600EVM, PMP8920

Hello-

We are developing the power front-end which includes 2 converters.  The 1st being the PFC section and the 2nd is the isolation converter which may be the LLC resonant Half-Bridge.  The output is 15V @10A and we are concerned about efficiency.  I have the following questions regarding the LLC converter:

1)      We are aware that the LLC secondary rectifiers are typical for this converter however, synchronous rectifiers can also be used.  Specifically, control IC’s exist for the drive and timing of LLC synchronous rectifiers and TI does indeed make this control IC.  Can the UCC24610 Controller be used in the LLC converter? 

2)      There is an App Note referenced in Powerelectronics referencing this concept however TI’s EVM’s do not use their UCC24610 controller.  Why not?

3)      Does TI have an LLC EVAL module utilizing the UCC24610?

4)      Can the UCC25600EVM (300W evaluation module) be modified to include the synchronous controller?

Thanks and Best Regards,

-Tim Starr on behalf of KB@ZM

  • Tim, see responses below.

    Hope this helps

    Thanks,

    Billy

    1)      We are aware that the LLC secondary rectifiers are typical for this converter however, synchronous rectifiers can also be used.  Specifically, control IC’s exist for the drive and timing of LLC synchronous rectifiers and TI does indeed make this control IC.  Can the UCC24610 Controller be used in the LLC converter?

    - Yes, note that if the LLC is running in CCM you may need to send a SYNC pulse to the UCC24610 from the primary side as described on page 22 of the datasheet.

    2)      There is an App Note referenced in Powerelectronics referencing this concept however TI’s EVM’s do not use their UCC24610 controller.  Why not?

    - I don't know but I would guess that the UCC25600EVM is to show the performance of that IC, not the UCC24610. Putting an SR controller on the board may suggest to some people that an SR is required to get good efficiency with the UCC2500.

    3)      Does TI have an LLC EVAL module utilizing the UCC24610?

    - The following reference designs use the UCC24610 in an LLC architecture.

    A 90-W High-Efficiency, LCC Series-Resonant Converter - www.ti.com/.../sluu467.pdf

     400VDCin, 12V@460W, LLC with Synchronous Rectifiers  -  PMP8920

    High-Eff 2Stage Univ Input Pwr Supply Using Trans Mode PFC/LLC Resonant Conv Reference Design - PMP8920

     

    4)      Can the UCC25600EVM (300W evaluation module) be modified to include the synchronous controller?

    - I expect so. Points to note are that the UCC24610 cannot tolerate more than 50V on the Vd pin (some extra circuitry can be used to extend this range).

    The Vcc has a maximum range of 5.5V, so in this applicaition it will require and linear regulator to supply the Vcc rail.

    As noted above a sync cap may be required in CCM

    Thanks and Best Regards,