Greetings. I have the same problem. I made the power supply circuit according to LNK624D program PI Expert. When I turn, then immediately burn IC LNK624. Began to look for the cause. I did a test pattern according to datasheet (no feedback). And that's what I saw. At a supply voltage of about 14 volts at the output pin "Drain" of chips visible square wave at approximately 265 Hz. When the supply voltage to 30 volts nothing changes. That is, the power transistor circuits LNK624 is open about 2 ms. That's a lot for a transformer. During this time, the transformer goes into saturation. And this situation with all the chips that I bought (about 20 pcs.). Then I picked up the old power supply chip TNY268. And for her to build the test circuit (without feedback). And that's what I saw. TNY268 chip opens the transistor with a frequency of 128 kHz for a short time, then a pause, then re-opens the switch at 128 kHz, etc. That is, start TNY268 done correctly.Now I have a question. Those LNK624, that I bought, they defective (fake) or a bug chip design company Powerint????P.S. Soryy my English. 

I sourced all the components but the transformer from Mouser so I believe that there's no defective or counterfeit devices. I also compared my design with others generated by PI expert software and I verified that there's no big diference amongst them. The board layout followed all recomendations by PI.

I hope a PI expert (a person, not the software) can shed some light on this problem.

 The fact that you received the items from the Mouser does not prove that the parts are not defective. Look oscillograms on pin Drain of IC. My waveforms look like ( see attachments) .

I believe that in my case is not working properly LNK624.

Have you tried these two kinds of transformer? If you tried and they are samething, then the problem is caused by the other circuit.

 PLS check the polarity of the snubber diode, the output diode and the output cap, and make sure they are good enough. If all these parts are correct, then verify the polarity of the transformer and make sure the output winding and the bias winding are really FLYBACK not forward winding.

Regards 

Well, it seems that the cause of the problem was a winding polarity reversal, specifically the primary winding. I had to replace the controller too. The circuit is running a little hot and I have to tweak the feedback resistors to adjust the output voltage but in general the output is very stable from 70 to 270 Vac. Thanks!

Cool. Could you make a waveform from pin Drain chips??  You can reduce the input voltage to 30 volts, the IC with the same voltage starts to work. I want to compare your waveform with mine.I would be very grateful to you. My power supply is still not working, and I can not understand why. 

LNK switch has been used by lots of customers and applications. PLS check your circuit and make sure the schematic and placement on your boards are good first.

Upload your schematic if your board can not work after you check your schematic and board carefully.

regards

I represent the scheme of a power supply. And also the scheme of a test board. And also the oscillogram in point DRAIN of a test board. This oscillogram correct??? And should work LNK624?? On idea, at breakage of a feedback (as in the scheme of a test board), LNK624 should do ре-start with a small interval. And it constantly gives out a meander in point DRAIN. Thus, time of opening of a switch is very large (approximately 2 msec.).

My suggestion is spending some time on your board and circuit first. Normally  PI part should be very good. As I said before, these parts are used by lots of differnt customers. PLS contact with local FAE at china. Hopefully they can help you and deliver you some sample.

regards

I will post the waveforms as soon as I finish the design!

After a long time working wit PI products, we decided to move to ST new range of products

PI products are so problematic for the below reasons:-

1- You will never get a fully working design generated from the software
2- Most of their designs, will generate transformer or inductor noise, and it will be difficult to overcome.
3- Complex and costly EMI filter
4- Will waste your time making it work
5- Difficult to pass EMC test

The last design that failed with us was for the LNK624

We had nasty transformer noise & very bad cross regulation & voltage drop

And we had no help at all, the transformer was made exactly as in the data in the software.

Thanks!