Hello TI team,
I just use UCC256403 for LLC design and calculation result attached. It's working well at all load conditions. The only issue I found is that at soft startup, the resonant current is very large.
Below is the first waveform after power up with no load.
Here CH2 is Vcap of voltage of resonant cap.
CH3 is the resonant current.
CH4 is SW point.
When start up with no load, it can output the desired voltage, after startup finished, I can add load to system. But if I add a small load even 0.1A at load to start up, the system can not start and enter hiccup mode.
Can you help to explain why and how can I solve the startup issue?
Does so large current at startup reasonable?
