Hi,
I am facing issues in the design of DC/DC converter using UCC28950. I am following slua560b application note. My design specs are as follows
Input 350-390V Dc
Output 28V DC @ 27 A
I am using RM14 Core (C95). I am able to run the converter at 354 DC input with full load. The transformer makes a sharp noise at the start up and last after few minutes (though not completely) and there is a rise in temperature. At low input voltage 280VDC there is no noise.
Second i am unable to run the converter in the CCM mode by shorting the DCM pin to ground. When DCM pin is shorted to Ground the transformer makes strange clicking noise and there is no output voltage. This happens at all input voltage range( from 50 to 380 VDC ) and with no load to full load condition. After few 20 to 30 seconds secondary side Mosfets are destroyed.
Another observation is that after running 45 minutes at full load (28.5V @ 28A) the controller enters into on/off mode and then synchronous FEts get destroyed.
I am not using shim inductor at this stage.
Regards
