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WEBENCH® Tools/UC2843A-Q1: Auxiliary winding in Flyback transformer

Akshay Purohit
Prodigy 120 points
Part Number: UC2843A-Q1
Other Parts Discussed in Thread: UC2843

Tool/software: WEBENCH® Design Tools

Hello,

I am not able to understand the function of auxiliary winding of the flyback transformer connected to the Vcc pin of the switcher. Input DC voltage  is also connected to the Vcc pin via startup resistor network. What is the role of Raux ,Daux and Cvcc and how is the turns ratio of Auxiliary winding achieved? Please explain in detail

Input voltage range is 10 - 26 V DC from a battery

Thanks and Regards

Akshay

  • 0
    TI__Genius 13660 points

    Hi Akshay,

    The auxiliary winding is used to supply bias voltage to the UC2843 after start up.

    Raux is used to limit the current. The role of Daux and Cvcc are same with Dout and Cout of secondary side.

    You can refer the section 9.2.2.2 Transformer Turns Ratio and Maximum Duty Cycle  for the turns ratio of Auxiliary winding.

    Regards,

    Teng

  • 0 in reply to Teng Feng
    Prodigy 120 points

    Thanks Teng for the support