Connect with us

TL431 and PNP for SMPS feedback.

Discussion in 'General Electronics Discussion' started by eem2am, May 7, 2011.

Scroll to continue with content
  1. eem2am

    eem2am

    422
    0
    Aug 3, 2009
    Hello,

    I am doing an isolated, offline flyback SMPS.

    I must have low standby power, and also, very little current (less than 30uA) in the opto-diode during heavy load.

    so i must use this circuit
    http://i54.tinypic.com/295r18x.jpg


    .....but do you know of problems with this?....will the feedback loop gain be too high due to the PNP amplfier?




    The PWM controller IC on the primary side has a feedback pin which is connected to the opto collector...........just 90uA COMPLETELY stops switching.

    i cannot use this circuit, as the parallel resistor invokes current in the opto-diode http://i53.tinypic.com/300qt8l.jpg

    ...due to the volt drop across the opto diode
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-