pfc on uc3854 soft start problem

[valter_ppk]

Hi everyone!
I have got problem with my pfc which I design using UC3854N IC. Problem concerns soft start pin, because voltage on this pin doesn't rise. Application note gives information that voltage on capacitor connected to this pin should rise to 8V when supply voltage is higher than 16V and when voltage on ENA pin (pin 10) is higher than 2.5V. I checked voltage on these both pins and they are OK (ENA is about 10V and supply is 18V), but voltage on SS is close to 0V. What is strange, voltage on SS pin reach 8V when I connect it for a while with RSET pin (pin 12.), wheras in application note write that maximum voltage on pin 12. is 3.75V. I don't know why voltage on pin 12. is so high.
I attach scheme, which corresponds conditions in which I tested pfc: ZAS1 is the input voltage for PFC and ZAS2 is supply voltage of UC3854N.

If anybody has any idea, please let me know.

 

[erenkcms]

hi,
i am using UCC3817 IC from TI. But i have got a problem. i give circuit from UCC3817 datasheet (typical circuit).
BUt this circuit does not working...
when i look at DRVOUT pin , i see square signal at 50 Hz but here the expected signal is 100kHz.
Also i can't simulation of this circuit but its library is not found.
can you simulate your circuit (uc3854,ucc3817...)? if you can simulate, do you say me which program?
Now do you find your problem?
thank you for your attention