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

Akshay Purohit

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

over 4 years ago

0 Teng Feng over 4 years ago

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 Akshay Purohit over 4 years ago in reply to Teng Feng

Prodigy 120 points

Thanks Teng for the support

Power management

Power management forum

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