Thermal shutdown??
Hello.
We have been using LNK501 IC for several years, but recently we have come across with somewhat very strange phenomenon.
It seems to go into thermal shutdown.
this phenomenon does not happen often in normal operation, but in chamber heatted up around 4~50c, it occurs, if it is a product with Power issue.
So I have tried to replace the IC with perfectly operating IC, the issue goes away.
I did some test, which was to measure temperature of the ic, on IC' source pin with thermocouple, and the result was at the point when it shuts down, temperature is 40C, no more than 50.
I also went and saw VDS, it never went over 690V rather stayed under 4~500V while switching.
When it shuts down, it went flat lined with 400V level.
This is my second time facing this issue, so I wish you can give me some wise advice on solving this issue.
Comments
Power issue is shut down. it actually shuts down.
replacing IC makes everything ok, even in chamber.
I do not use Opto, so it is not CTR issue.
The device cannot be thermallt shutdown at 40 C,
Could you let me know what is the power issue?
Honestly,I do not think it is caused by LNK501, since it has been used for several yrs. Inside the chamber,performance of other part could be different too. I wonder if the design was modified recently or a new part was used. If optocoupler was used to improve the regulation, PLS check the CTR range of the opto. CTR reduced significantly at hot.