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PMP10236: Confirmation

May
Genius 9880 points
Part Number: PMP10236


Hi Team,

Good day, one of our customer want to use PMP10236 as reference and want to know the reason why bulk capacitors for high bus voltage  uses resistor such as 4.7Mega ohm in the design. 

Thank you and looking forward for your kind response.

Regards,

Maynard

  • 0
    TI__Intellectual 2770 points

    Hello Maynard,

    those resistors are symmetrizing the capacitive divider;
    a good starting point for the resistors bias current is 10x leakage current of capacitor.

    If you don't use them during start up or transient the two waveforms at the output are not exactly balanced,
    resulting in bigger ripple at 1/2 Fsw. After some ms the reflected voltage to the primary ensures "normal" operation,
    balances itself.

    Depending on quality of your capacitors 2x 2MegaOhm to 2x 4MegaOhm is a typical value here;
    regarding the capacitor leakage current please watch out for aging, too.

    Hope this helps & best regards, Bernd