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LM5018ISOEVAL: About max duty cycle

Tsukui Yusuke
Guru 21930 points
Part Number: LM5018ISOEVAL

Hi,

Customer is considering the LM5018ISOEVAL circuit configuration.
Customer requirement specification is ;

Vin=8.2V
Vout1=8V / Iout1=200mA(max)
Vout2=xx /  Iout2=xx

1．Please tell me the minimum value of the voltage difference between the VIN and SW pins.
　  Customers want to know the MAX duty of this EVM.
　  ※UVLO initial setting is scheduled to be changed.

2.  Please tell me how to calculate the drop voltage 0.5V of Vout2.



Best Regards,
Yusuke

  • 0
    TI__Guru 74462 points
    Hi Yuseke-san,

    The duty cycle of a Fly-Buck converter should not exceed ~65% (this allows 35% of the switching period for secondary-side conduction). 8.2V to 8V on the primary side is not feasible for a Fly-Buck.

    The difference between Vout1 and Vout2 in the above schematic is the D1 diode voltage drop (assuming a 1 : 1 transformer turns ratio).

    Regards,
    Tim