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UCC256304: Startup Fault condition

Part Number: UCC256304

Hi,

I use controller UCC256304 for power supply 24V/350W

design input range 240V-390VDC

i can turn it startup at full load, output working stable. but then about 25 second after first startup otuput power go down  --> restartup output working about 1 second --> restartup output working about 1 second --> then no output power.

I measure current of resonance winding when it fail output is overshort current switching. but in first startup i measure current is belower and stable.

how I can fix it?, and how many reason make it fail output power?

thanks!