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TL431: TL431ACLPR unstable

Kevin Huang8
Genius 3955 points
Part Number: TL431

Tool/software:

Hi Team,

TL431ACLPR unstable, please help check schematics thanks!

1. When the power supply is working, the main line stops working. The main voltage does not drop, but the SW12V voltage drops. It is found that U54 (the feedback voltage regulator used in the TL431 circuit) does not work.

2. Analysis shows that the TL431 VREF voltage is in a stable state, and VKA is suddenly greatly loaded, causing the main VBF (feedback detection PIN) to return to zero, and TL431 stops working.

  • 0
    TI__Expert 8750 points

    Hi Kevin,

    I feel that having a more aggressive compensation network will make it less sensitive from the noise going from the reference to the cathode, could you increase C255 from 100pF to ~500pF?

    Thanks,
    Joshua