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UCC28070: Vblk drop

Rock Shao
Expert 2995 points
Part Number: UCC28070


Hi, 

My customer use UCC28070. At present, in 90Vac and from no-load to full load (1050W), the PFC Vblk drops to about 400V→328V.

Is it adjusting the feedback compensation of CAOA and CAOB or VAO pin? Thanks.

  • 0
    TI__Mastermind 24375 points

    Hi Rock,

    Thank you for the query.

    It is hard to tell what is going on without schematic and the design calculator. Is this effect happening only at 90Vac or also  at high line 230Vac? Then it could be hitting current limit causing the voltage to drop. It could be possible you have chosen wrong value of Rimo. You can try fixing the compensation values on VAO. Also check for the gate pulses GDA/GDB. Please share the design calculator also.

    Regards,

    Harish