LNK6768K - built ckt per PI, but converter won't start
I am at a loss to understand why the converter won't start when presented with ~200V DC input voltage. It seems to shut down immediately, and draws no current and doesn't try to start at all. I have uploaded the as designed by PIExpert and as implemented schematics.. need help!
Comments
resistor from bias winding to bypass pin - PI not so expert issued 0k as the value; should be 4.3k. PI expert makes mistakes!
Hello kwing54,
Thanks you for interested in using Power Integrations products.
As you mentioned, you are using the PI expert to do the design. From the schematic you share, it seems that you followed the Piexpert and no change was made. the only difference is you are using a DC input while you designed with AC input. the schematic looks good to me. how about the transformer consutruction, can you share that information with us as well?
when you mentioned the power supply doesn't startup, can you see any rise at the output. if possible, can you measure the BYPASS pin voltage to see how much you will get. if you can measure the drain to source pin voltage, that will be even better. It can tell us if the IC is trying to swicth or not. if you can share this information with us, we can continue and move on.
Best Regards
kwing54,
Thank you very much for reaching out. We were able to re-create the bug that you pointed out and are currently investigating this anomaly. As you correctly pointed out, the bias winding resistor should be in the vicinity of 4.3kohms and not 0kohms as mentioned in PIExpert.
Thank you once again for your observation.
added PCB layout