tl431 infeedback loop

Posted by: sraman on 05/22/2011

I am designing a 100 volts/ 0.5 A power supply using TOP245YN. PIExpert is suggesting to use TL431 in the feedback loop which is having a max. cathode voltage rating of 36 volts only. Will this create a problem?
the piexpert file is attached for ready reference.
regds,
sraman

Files

110V55W.xls (60.5 KB)

Comments

Hi,

You are right in pointing out the problem with the use of TL431 for high voltage output designs.

We have a reference design that shows use of a zener to circumvent the problem.

http://www.powerint.com/sites/default/files/images/schematic.gif

I hope you will be able to use a similar arrangement for your design.

Regards

PI-Sarek

Hi,

The l8ink in the previous reply was incorrect.

Please use the link provided below:

http://www.powerint.com/sites/default/files/PDFFiles/der97.pdf

Regards

PI-Sarek

Dear Mr Sarek
Thnks for the reply. Actually my requirement is for 110 Volts, 500 mA output. As PIExpert does not support O/P voltages higher than 100 Volts, I hv designed this ckt using the software and increased the secondary no. of turns proportionally to the o/p voltage. However, the ckt stops working due to thermal shutdown of TOPSWITCH. Is the problem due to the overvoltage of the TL431 or saturation of the transformer? Can u help? Pls note that I hv designed SMPS upto 48 Volts and power rating of 240 Watts using TOPSWITCH and till date hv not encountered any problem before this one.
regds
sraman