Hi
Working on 800W resonant mode converter with UCC25600 LLC controller.
Build up as the typical application diagram and by use of the design tool.
It work perfect in steady state (same output current, same load) and Eff. shows up to 95 % close to max load.
But with transient loads something strange happens.The Upper fet is blowing even at very light loads. So changing
from load to no load which means that the converter goes into burst mode damage the fet. (FCPF22N60)
Can this be caused by the high drain current when gate turns on again after the burst break?
I did'nt quite hit the Lr calculated in the spreadsheet 31uH but ended up with a
Leakage induction Lr at about 22UH.
Here is the input parameters used in the spreadsheet.
Vin Min: 375V
Vin Max: 410V
Fsw norm.: 134khz
Fsw Max.: 350khz
Fsw Min : 65khz
Max. Power Limit: 800W
Max. Output Power: 775W
Full load eff: .92
Vo: 155V
M: 9
Qr:0.5
Tss:25msec
Td: 200nsec
Br
Finn