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LM5023: LM5023

Girish K76
Prodigy 90 points
Part Number: LM5023

Hi,

   We are trying to design an SMPS for our 120W application, for which we selected TI based LM5023 QR current mode controller.

    We found in all your application notes, it is limited to 65W power output .

    Is there any power output limitation for this controller or is it safe to choose for our 120W power output level?

    If so,please provide some typical application manual for the same ,also provide high frequency transformer winding details .

Thanks and Regards,

Girish K

Design Engineer,

Power Electronics and Drives division,

CDAC,India

    

    

  • 0
    TI__Guru* 77865 points

    Hello,

    The data sheet discusses the typical application as being 65W.  Could you tell me which application note that say's this device is limited to 65W applications?

    The LM5023 is a quasi resonant flyback controller that drives an external FET.  You should be able to use in flyback applications up to 250W.  Do to higher RMS currents after that  designers generally designs will move to a forward converter for more efficient design.  So your 120 W application should be O.K.

    The gate driver is only capable of delivering 700 mA peak.  That will affect how fast your FET turns on and off.  When selecting FETs of for your design you may need external FET drivers.  A good estimate is to select so the gate of the FET can reach full charge in 50 ns.  Depending on your frequency this could be 100ns.

    I=dQ/dt, Qmax = I*dt=700mA*50ns=35nC.  If your application is driving FETs were the gate charge is greater than 50 ns, I would recommend using an external gate drive.

    Regards,

  • 0 in reply to Mike O'
    Prodigy 90 points

    Hai,

     Thank You for your immediate response on the issue.I found in the LM5023 datasheet like "Universal Input AC-to-DC Notebook Adapters from 10 W to 65 W", where my doubt came from.Now i am clear about the application level.Thanks for giving an overview of gate driving recommendations.

    Is there any good application design note so that the transformer winding details and all can be fetched ?

    Regards,

    Girish K

  • 0 in reply to Girish K76
    Prodigy 90 points

    Hai,

      I need one more clarification in the gate driving voltage level of FET. Please find attached the red highlighted portion  from the datsheet.

      As mentioned here, VOH level is 1.1V max, where i came to understand that we cant give more voltage level than this to the external FET.

     

    But the recommended FET datsheet mentioned that Vth is 4V (shown below) which is a bit confusing. Kindly give some clarification on this.

    Regards,

    Girish K

  • 0 in reply to Mike O'
    Prodigy 90 points

    Hello,

     Can you recommend any ready-made transformer for this application, since we are not expertise in this area?

     We haven't found any transformer design for the LM5023 based smps design.

    Regards,

    Girish K

  • 0 in reply to Girish K76
    TI__Guru* 77865 points

    Hello Girish,

    If you go to the following link and scan halfway down the page you will find Webench designer.  You can enter your design parameter and it will generate a schematic and transformer specification.  You can send this to GCI, Wurth or Renco and they will review the design and design a magnetic for you.

    I am sorry but in regards to power supply design most of the magnetics are custom and there are not standard off the shelf transformers.

    Regards,