This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PMP40328: Unstable Vout (7.64~9.13V) at Vin>200V

Part Number: PMP40328

Hello,

Recently we have been working on module PMP40328. At low input voltage range (90V~150V), the output voltage is stable at 9.04V. However, at input voltage>200V, the output voltage is unstable (which kept changing from 7.64~9.13V). Why the input voltage range affects the stability of Vout?  Or is there any problem we should check on our PMP40328?

Thank you for answering the question.

Sincerely,

Chiao

  • Hi, Chiao,

    Thanks for your working on PMP40328 module.

    Theoretically, there is no affect on the stability of output if the input voltage change from 85Vac-265Vac. Could you please check which system fault protection occurs and what is the delay to action in datasheet Page 30? Either, could you plesae send me one Vds, VDD waveform when intput voltage is above 200V?

    Thanks.

  • Dear David,

    Sorry for the delay in providing the waveforms.

    The photo below is:

    1.Vds at Vin=200V (Peak voltage=374V, Min voltage=-36V)

    2. VDD at Vin=200V (Stable at 15V)

    Thank you for your help.

    Sincerely,

    Chiao

  • Hi, Chiao,

    Thanks for your feedback.It seems to be the feedback loop problem.

    Could you please check if there is the same problem with output no load and full load?

    Thanks.

  • Dear David,
    The problem is more severe when the PMP40328 at full-load. (Drop to 5.65V).
    The test results mentioned before is tested with output no load (7.64~9.13V).

    Also, D4 and Q6 of the secondary side regulation circuit were damaged sometimes, and the output at this situationis also unstable. Therefore, we have changed the D4 Zener to 1W level, and the problem of regulation circuit D4 and Q6 is temporarily fixed. However, I'm not sure whether this will affect the feedback loop or not.

    Thank you so much for your reply.

    Sincerely,
    Chiao
  • Hi, Chiao,

    It seems that the issue is coming from SR.

    Please remove the D8,D4,Q6,R13 and connect output to C16 capacitor. Or, add one secondary winding for SR power supply.

    I need to update the website schematic later.

    Thanks.

  • Dear David,

    I have removed the D8, D4, Q6 and R13 and connected output to C16 capacitor. The output is stable at 220V at no-load now, but the output still drop to 5.56V with load.

    I will check the SR and the components, too.

    Thank you so much!

    Sincerely,
    Chiao
  • Hi, Chiao,
    It should be the feedback loop issue and high line compensation, plsae adjust the parameters according to the following suggestion.
    Please increasing the C22 to 680pF; R16 decreasing to 1.5kohm; R26 increasing to 10kohm.
    Thanks.