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PMP10200: Why is the output power constrained to 10 W at low input voltages?

Jon Hall
Prodigy 10 points
Part Number: PMP10200
Other Parts Discussed in Thread: UCC28700,

I'm trying to figure out why the output power is specified as 20W when input is higher than 60V, but only 10W otherwise. Based on my quick math, it seems like the converter should be able to comfortably operate in DCM, given the transformer and capacitors used. My best guess is a stability issue?

Thanks!

  • +1
    TI__Mastermind 40100 points

    Hi Jon, usually the peak currents are higher at the lower input voltages so you're limited on the total output power before hitting current limit. However, I've reached out to the designer of this reference design to also comment. Thanks!

  • 0
    TI__Prodigy 430 points

    Hi Jon,

    A valley switching quasi resonant controller like the UCC28700 cannot support every ultra wide input range because of limitation of the minimum on-time, the switching frequency and the primary peak current. The PMP10200 was designed and tested only for this certain specification:

    Pout_max = 10W for Vin<60V.

    I_out_min = 0.35A for Vin>60V.

    Please note that in general a higher output power could be achieved by increasing the peak current, but this reduces the switching frequency and the controller may no longer works in FM mode for full load. Please also note, that a minimum load of 0.35A is required, otherwise the minimum on-time (for high line) will be violated.

    Thank you.