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Original question:

UCC2897A: Active clamp flyback converter

UCC2897A: ACF Flyback without isolation

MUHAMED AJMAL C N
Prodigy 30 points
Part Number: UCC2897A
Other Parts Discussed in Thread: TL431, UCC2891, , TPS28225

Tool/software:

Hello,

I am designing a fixed-frequency active clamp flyback converter that do not require the secondary ground to be isolated from the primary. As a result, compensating the loop with an optocoupler and TL431, as typically suggested in references, is not an optimal solution for my application. Are there any reference materials available for closing the loop when using this IC or any member of the UCC2891/2/3/4/7 family without an optocoupler?

Additionally, since isolation is not required, could you recommend a general-purpose current-mode controller with complementary outputs and programmable dead time as an alternative to the UCC289x family for implementing a fixed-frequency ACF?

Thanks,

Ajmal

  • 0
    TI__Guru 74115 points

    Hi,

    If not use opto-coupler, you can use an external error op-amp to drive FB pin of UCC2897A and that external error op-amp to help provide feedback control. FB pin voltage is too low to connect to TL431 so an external opamp is needed.

    We do not have a general purpose PWM controller with complementary outputs. One possible solution is to use GP-PWM with TPS28225. TPS28225 helps to convert single PWM signal into complementary two outputs like used in buck converters.

  • 0 in reply to Hong Huang
    Prodigy 30 points

    Thanks, using an additional driver with a GP PWM controller sounds good. However, TPS28225 uses a limited-duration adaptive dead time control which might not be enough for my application. Is there a similar single PWM to dual output driver that has features to set the dead time manually like in the UCC289x series?

    Thanks,

    Ajmal

  • 0 in reply to MUHAMED AJMAL C N
    TI__Guru 74115 points

    Hi,

    No, I do not know. 

    I suggest you create a new thread with subject including TPS28225 word then in the thread asking if there are devices same as TPS28225 but deadtime can be setup manually. The thread will reach a proper team to help check if any similar devices can be referred.