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Original question:

UCC28070: ucc28070 current sample question

UCC28070: 3500W large dynamic PFC-MOS tube current waveform

Gabriel Wang1
Genius 4715 points
Part Number: UCC28070

Dear Expert

In batch production test, due to the small capacity of the input voltage regulator, the input voltage drop with 3500W at full load is about 20VAC, and the MOS tube of PFC will be damaged by large dynamic from no load to full load.At the client side, there is a risk of damage to the MOS tube if the input regulator the client is using has a low capacity.Is there a good way to solve this problem?

Input voltage 220VAC, output from no load to full load to do large dynamic (input voltage 220VAC from no load to full load, the voltage drop is about 7VAC) MOS tube 500ms per grid current waveform 29A.

1.MOSFET 500ms per grid current waveform,maxium 29A :

2.MOSFET unfolds 5ms per grid current waveform, maxium29.8A

3.MOSFET unfolds 5us per grid current waveform,maxium29A

Input voltage 220VAC, output from no load to full load increase dynamic (input voltage 220VAC from no load to full load, the voltage drop is about 20VAC)

MOS tube unfolds 5us per grid current waveform maxium 62.5A

  • 0
    TI__Genius 9140 points

    Hi Gabriel,

    thanks for your interest in UCC28070.

    If it happens that the ac source drops a lot cause the mosfet with very high current, since the CT has a real time sapling of mosfet current, is it possible to decrease the PKLMT threshold to limit the current and protect the mosfet?

    another suggestion here is:

    is it possible to incease the VINAC resistor divider to input a "fault" signal for the controller. For example, if input voltage is 220VAC, there level 7 for kvff is normal used, then you can try to use level 8 to limit the duty.(refer to page 21 of datasheet). or try to always let KVFF to be level 8, then you may need to find tune the Rsynth to improve the current distortion caused by mismatch of Vinac sampling.

    hope this helps you.