outputside diode of LNK 419 33watt design is become open after sevsel hours

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Dear Sir ,


we are working on lnk 419 ic .

we have get output of 48 V 700mA.

when start the led driver , driver is working proprely .

but  after severl hours of operation secondery side diode is become short . and driver is stop working .  i  am using MUR460.

 and we are getting sound of like " beep beep"

this problem we find in only in  severl drivers. 

 can you please tell what can be the problem ?


as per my thiking it can be the transformer problem?


please guide on this problem . 


thanking in advance . 


Smit Patel

circuit diagram.doc212.5 KB

Check voltage, current, and temperature on the diode and see whether its ratings are exceeded.