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PMP10195: Quick startup time approach for flyback SMPS

Xavier Pacheco
Prodigy 75 points

Part Number: PMP10195
Other Parts Discussed in Thread: UCC28711,

Hello,

PMP10195 reference design claims less than 70-ms startup time. It uses a MOSFET STP3N150 for the startup network, but this FET is expensive. Is there a reference design or approach to achieve quick startup with a less expensive part? I have the same input wide voltage than the app note. I'm planning to use UCC28711 which has a HV pin. Can the same startup be achieved through this pin with a resistor-diode network?

  • 0
    TI__Intellectual 2770 points

    Hello Xavier,

    please check PMP10195, made for 3ph input up to 1200V+;
    so this design uses 1.5kV discrete startup solution.

    The internal startup FET of UCC28711 is only able to handle 700V.

    Best regards, Bernd

  • 0 in reply to Bernd Geck
    Prodigy 75 points

    Bernd,

    The 1.5kV discrete startup solution is expensive because of transistor Q3. I would like to know if there is a less expensive approach within TI solutions without compromising the startup time and the 1.5kV. Thanks. 

  • 0 in reply to Xavier Pacheco
    TI__Intellectual 2770 points

    Hello Xavier,

    if you don't like the cost  for FET simply charge the bias capacitor across resistor;
    for "fast" startup you need to accept some losses there; standby power will increase as well.

    For startup i.e. 100ms it will be a mess, check Q = C x U = I x t;
    let's assume 22uF to 25V, so current is I = 22uF x 25V / 100ms = 5.5mA

    At 1000V input the losses across divider are 5W+ (!).

    Either you accept the auxiliary FET or you go for very long startup time.

    Best regards, Bernd