Hi
Thanks guys for the input.
I am using the converter at 50Khz. The reason i am using this high value of capacitor is that, this stage is supposed to be input to inverter(dc-link capacitor, to reduce ripple of inverter output). I am at present testing it in open loop so no damaged due to defective control.Also regarding that opto inverting characteristic (if i use IXDI504PI inverting output,that problem could be solved).
Secondly the diode which i used is PFr856 which has Trr of 200ns, would that be sufficient at 50Khz? Also current rating of diode is 3 A, at 370 W output and 400V , the load/diode current would be nearly 1A so its not going above diode rating.
SO again it comes back to question a) why is switch and diode getting damaged together b) how to protect the gate driver ic.