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TIDA-00779: Output voltage fluctuation

Nidheesh BR
Expert 1295 points
Part Number: TIDA-00779

While turning on the PFC output DC voltage was 389 V.

Then increased load up to 3.6KW in steps of 240W and voltage was stable at 389 volts.

Then I kept it running as it is for a long time. As the time proceeds the output DC voltage seems to be slowly rising.

so I run it for a very long duration of time.

in 2-3 hours voltage raised up to 401 volts. then in the next 4 hours, it raised up to 403V only and seems to be stable at 403 volts.

Is it a desirable condition?

What can be the possible reason for this?

Thanks.

  • 0
    TI__Intellectual 950 points

    Hi Nidheesh,

    Where did you do this test? our EVM or your board by yourself?

    What is the test environment? Input voltage?  ambient temperature? Any forced cooling? Did you monitor the temperature of components?

    BR

    Jason

  • 0 in reply to Yuan Tao
    Expert 1295 points

    Hi Jason,

    I conducted the test on a board by myself with reference to your reference design.

    Input ac voltage:231V rms (disabled boost follower circuit)

    Input Ac current:16.5A rms

    ambient temperature: 28-degree celsius

    I used series-parallel connected incandescent lamps as load bank. and never faced a problem with cold resistance issue. And load seems to be constant throughout this 8 hours testing.

    I used heavy forced air cooling for MOSFETs, Diodes and Bridge rectifier because the heat sink is suggested for these three components in the design. So even after 8 hrs run heat sink was light warm only.

    PFC inductor was a little bit heated may be beyond 50-degree Celsius. Remaining all components seem to be just warm only.

    when I tested the same with the 2.6KW load this voltage rise was just 3-4Volts. But with 3.6KW load, it was around 14-15 V rise.

    But there was no voltage change while changing the load, the voltage change noticed only for a long period of run.

    Thanks.

  • 0 in reply to Nidheesh BR
    TI__Intellectual 950 points
    Hi Buddy,

    I think this question has been finished, thanks.


    BR
    Jason
  • 0 in reply to Yuan Tao
    Expert 1295 points

    Hi Jason,

    Ya, it's almost solved. As you suggested I tried forced cooling of feedback paths. So it seems to be more stable. So in my next design, I will try to isolate the feedback and control parts from high heating power path.

    Thanks buddy for your wonderful support.

    Regards

    Nidheesh.