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Original question:

PMP8740

PMP8740

anjana salgaonkar
Expert 1460 points
Other Parts Discussed in Thread: PMP8740

Hello Roberto, 

IN PMP8740

what switching frequency is used in DC-DC section (for ZVS FB) ? Is primary switching frequency and secondary switching frequency is different?

what is duty cycle considered for DC-DC converter? 

Anjana

  • 0
    TI__Expert 5875 points

     isHello Anjana,

    The switching frequency of the DC/DC section is 100 KHz at primary side (Q8, Q9, Q15, Q16) and 200 KHz at secondary side (after output inductor L3), therefore the ripple current on output capacitors has to be calculated @ 200 KHz.

    The maximum duty cycle of the converter, which is calculated @ 32Vout and 350Vin, is 86.86%, while @ 32Vout and 420Vin is 72.38%.

    Of course, the lower Vout is, the lower is the duty cycle.

    Regards,

    Roberto