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UC3843: 6.25V main feedback voltage over 5% tolerance

Patrick Chen
Mastermind 8875 points
Part Number: UC3843
Other Parts Discussed in Thread: TL431

Hello,

Vin 220ac. 9 output power rail. 

6.25V/2A(main feedback)、+15V/0.3A、-15V/0.3A、24V/1A、10V/0.3A、thress 25V/0.5A and 25V/1A.

           While connect to load 0.6A, 6.25V will be over 5% spec. limitation. How to solve this issue? Thank you.

BR

Patrick 

  • 0
    TI__Guru* 86286 points

    Hello Patrick,

    I reviewed your schematic and you are regulating the output with the 5V output of TL431 feedback DU4.

    The 6V output is not being tightly regulated and will have a duty cycle based on the 5V output.

    You have a couple of options that you could try.

    1. If you want the 6V output to be tightly regulated you could adjust the TL431 to sense the 6V output.
    2. You could adjust the turn ratio of the secondary winding of the 6V output to meet your regulation requirements if it is the only output out of tolerance.
    3. Use a series pass regulator and or shunt to better regulate the 6V output.

    Regards,

    Mike