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UCD3138: Output no load issued used single phase CCM PFC output 800W

prarinya Maneechompoo
Intellectual 540 points
Part Number: UCD3138

Dear ALL

Pls help to suggestion customer have problem of UCD3138  he used in PFC circuit   .

How to improved  this issued   ? 

detail of this issued is below  .

We use UCD3138 for single phase CCM PFC . output of PFC about 800W .

We found that when PSU was in 0A output load condition.

The bulk voltage was rising up like the figure below until it had tripped OVP and

happen only in quite hi-line input voltage (245 to 264 Vac) and

just found only one sample in several samples, not every samples found this problem.

Have you ever faced this problem before or do you have any suggestion about this?

 

Test condition of the below waveform: AC voltage turn on  with 230 Vac then switch to 264 Vac immediately then turn off AC voltage.

 

 

Thank you so much & Bestregard

Prarinya

  • 0
    TI__Genius 17090 points

    This is generally caused by offset on the current sense from the external amplifier and the EADC on the UCD.

    With negative offset, a current reading of 0 will actually mean a current is still flowing.  So the firmware will request zero current, but the hardware will deliver some current.  

    You can solve it by putting in maybe 10 millivolts or more of positive offset in the current amplifier so that even if there is negative offset in the system, it will be overridden by the build in positive offset.

    Another thing you can do is to put in effectively burst mode - if the output voltage gets too high, just turn the DPWM off until the output voltage drops back down.

    If its a light load issue, you will have plenty of time to do this if you sample at the 10 KHz interrupt rate.