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UCC28950: feedback loop design of PMP8606 and SLUA560C

SAMRAT PUJARI
Intellectual 730 points
Part Number: UCC28950
Other Parts Discussed in Thread: LMV431, PMP8606,

Hello

In SLUA560C its not isolated feedback, in pmp8606 its isolated, apart from that how the feedback designs are different? Is the loop gain affecting by the isolation (optocoupler)? Is LMV431 precision regulator design acting as compensator too? how? if yes then what the R33 and C38 are used for? I think thats where the real compensation is? please clarify?  any references for this complete feedback design?

I want to implement feedback of pmp8086 in slua560c.

thanks,

samrat

 

  • 0
    TI__Mastermind 27145 points
    Hi Samrat,

    Thanks for your interest in UCC28950. The optocoupler does affect the shape of the gain and phase curves. The impact of the optocoupler itself is the gain will have a current transfer ratio (CTR) term which comes from the opto. Your converter bandwidth will also be limited by the bandwidth of the opto.

    LMV431 is the error amplifier on the secondary side which has an internal reference of 1.24V. R27 and R31 form the feedback divider to the error amplifier. C31, R26, C25, R11 and C33 are compensation components. R24 and R25 help set the fast lane current in the optocoupler. R33 and C38 are compensation components for the internal error amplifier on UCC28950.

    This reference might be helpful to you:training.ti.com/power-tips-compensating-isolated-power-supplies

    Best Regards,
    Ben Lough