UCC28070A: What cause the inductore current doing like this

?? ?

Prodigy 100 points

Part Number: UCC28070A
Other Parts Discussed in Thread: UCC28070

Tool/software:

Hi team, I wanna ask what reason cause my inductor current acting wrong?

Below is my waveform,yellow is input voltage,green is input current,and red is inductor current.

When I raise the output power,the inductor waveform starting werid.

Is this because of Inductor Saturation?

over 1 year ago

0 ?? ? over 1 year ago

Prodigy 100 points

Or this is because of the wrong components design(Cpc Czc Rzc)?

+1 Ulrich Goerke over 1 year ago in reply to ?? ?

TI__Mastermind 40580 points

Hello,

This weird current waveform does not appear to be inductor saturation.

Definitely, there is unstable current-loop operation, but it is not clear if the instability is due to incorrect (Cpc Czc Rzc) values, or if it is due to interaction with the AC source impedance. The ringing voltage on the input voltage waveform suggests that there is significant output impedance at the source.

Please provide the UCC28070 Calculator Tool Excel file for this design.
Also, please provide the test conditions under which this waveform was obtained.

Regards,
Ulrich

0 ?? ? over 1 year ago in reply to Ulrich Goerke

Prodigy 100 points

Would the PKLMT affect inductor current?

0 Ulrich Goerke over 1 year ago in reply to ?? ?

TI__Mastermind 40580 points

Hello,

PKLMT will limit the peak current of the inductor on a cycle-by-cycle basis at the switching frequency.
The waveform shown has unstable oscillations at a frequency much lower than the switching frequency.

I don't think that PKLMT is involved here.

Regards,
Ulrich

0 ?? ? over 1 year ago in reply to Ulrich Goerke

Prodigy 100 points

So I just adjust the CAO pin( Cpc Czc and Rzc )value. Or adjust the VAO pin?

+1 Ulrich Goerke over 1 year ago in reply to ?? ?

TI__Mastermind 40580 points

Yes, it is possible that adjusting the CAO pin component values ( Cpc Czc and Rzc ) may solve the problem. I suggest to use the Excel tool to calculate the proper values: https://dr-download.ti.com/design-tools-simulation/calculation-tool/MD-HcFEXblwq6/01.00.00.0A/sluc114a.zip

But also investigate whether you may have an unstable interaction with the AC source.

Regards,
Ulrich

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UCC28070A: What cause the inductore current doing like this