UCC28950: ucc28950 output ossiclation

What is your load condition? Can you share more waveforms at COMP pin?

This problem occurs when there is no load on the output connector this situation improves when a load is connected to the output even at 100mA

We need more details on the issue. What's the difference between these two images?

Please share the full schematic, more waveforms on the feedback loop, such as COMP and EA pin, at different loadings, etc.

Hello, first of all, thank you for your quick reply

The photos above are a photo of the circuit output non-load state, and the two photos show the same thing.

The schematic you shared previously doesn't have the controller. It only shows the power stage.

The IC responds to the COMP signal and the Vout clearly matches the COMP freq. You need to figure out why there is a 20Hz freq when no load. Likely it is due to your feedback loop design, which is not clear from the schematic either. 

Please refer to the example schematic in the datasheet and example designs on ti.com.

You might want to size your output capacitor large enough too. Please go through the calculator tool to design your power stage.

https://www.ti.com/tool/download/SLUC222

Hello,

i forgot to add the control circuit part, I'm sorry, could you please re-examine it. If there is an error that you see, please indicate it.

4237.quess_82V.pdf

Please share the ABCD waveforms during a single COMP rise event.

Also, the Vout waveform at 1A load is not clear to me. Do you see 2.8V ripple at ~170Hz?

Is your total Cout = 33uF *3 + 15uF = 114uF?

Hello,

Ripple occurs at 170 Hz and 2.8V when the output load is 0.01A, not 1A

in the case of no load, a ripple of 16 Hz occurs, the frequency increases as the load value increases, and the ripple disappears

total Cout value 114uF is correct

I will send you the desired waveforms tomorrow and I would like to apply the recommendations you can give at this stage

Best regards

ok, will wait for the waveforms.

Hello,

In case of "NO LOAD", ABCD signals are given with different measurement ranges in the photographs below. Two of the measurements belong to A and B signals, the other two belong to C and D signals. The signals are not periodic in the "NO load" state.

I know that my output capacitor is lower than it should be, but I need to design the circuit small. Will the input inductance of the transformer or leakage inductance be effective in this situation?

I will be waiting for your valuable thoughts

Best regards

Can you overlay the ABCD waveforms in one screenshot? Also, please show the COMP signal at the same image when you zoon out to mS range.