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PMP5711: Minimum Load requirement of PMP5711

Aneesh TS
Expert 1735 points

Part Number: PMP5711

Dear TI experts,

Is there any minimum load at output side Requirement for PMP5711?.

Regards

Aneesh

  • 0
    TI__Intellectual 2770 points

    Hello Aneesh, the design is fine for zero load, best regards, Bernd

  • 0 in reply to Bernd Geck
    Expert 1735 points
    Dear Bernd,

    Could you please explain how this minimum load requirement is taken care in PMP5711?

    Regards
    Aneesh
  • 0 in reply to Aneesh TS
    TI__Intellectual 2770 points

    Hello Aneesh,

    the error amplifier is on secondary side, see U2A, so output voltage is controlled directly at output capacitors,
    using the remote sense lines directly at the point of load.
    At forward topology output energy is controlled by the V x sec product, so reduction of duty cycle results in less energy at the output.
    At light load or zero load the controller starts to skip pulses, but auxiliary is kept alive by internal J-FET.
    You could study data sheet page 19/22 on this.

    And it works, you could study my test report page 2, figure 1/2, start up and shutdown are shown at full load 35A and zero load 0A.

    Best regards, Bernd

  • 0 in reply to Bernd Geck
    Expert 1735 points
    Dear Bernd,

    PMP5711 is very fantastic design in all aspects, mainly in terms of efficiency as well as compactness.

    Thank you for sharing the details. I have one more query,

    I have the requirement of two 5V/15A output isolated each other . I am planning to use same PMP5711 design with one more extra secondary winding with one 5V/15A connected to the feedback loop and other winding is in open loop. Second 5V/15A output is planning to regulate with a extra buck regulator at output side.

    So My doubt is, if first output goes to no load UCC2897A will operate in Pulse skipping mode and regulate the first output. But what will be the output voltage of second output if it is loaded? Will i able to meet my requirement?.

    Regards
    Aneesh
  • 0 in reply to Aneesh TS
    TI__Intellectual 2770 points

    Hello Aneesh,

    this won't work properly for single ended FORWARD topology by just adding a secondary winding at xfmr;
    it's not like a flyback, so just think about a dual winding for output filter inductor...

    Simply go for LM5034 and operate the two REGULATED 15A power stages 180 degs out of phase...

    Best regards, Bernd