TOP 268 +/- voltagae feedback
Posted by: Ian Wilson
on
Hi
I am trying to develop a PSU which porvides +/- 22v output and uses feedback from both outputs. I am using a TL431, referrred to the -22v rail with a potential network on it's reference pin:
11k between -22v and Vref
170k between Vref and GND
365k between Vref and +22v
The opto coupler is where I think my problem lies, I am pulling to +22v with 21k and pulling up to GND with 11k.
The PSU regulates beautifully at 230v a.c. but does not start-up at 100v a.c.
Any suggestions from the forum?
Ian
It might be start up delay problem. Try doubling the value of the C-pin capacitor and see if that helps start-up at 100VAC.