You may have a grounding problem and due to noise in the ground line to get
more than 35V on the cap. I had the same problem last week on a 100W 13V to
200V push-pull converter running at 250kHz. In my case the smps controller
blew up although it is rated for 40V and in my circuit it gets max. 18V. But
due to a bed grounding strategy the noise vas greater than 40V and in a
matter of 1-2 hours the controller got burned. Provide separate return paths
for ground currents to the lowest impedance point and as large traces as you
can afford. This worked for me.

Sascha


-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.289 / Virus Database: 265.4.2 - Release Date: 11/24/2004
 

_______________________________________________
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist