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UCC3806 reference design and simulation model

Genius 3245 points

Replies: 8

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Hello,

The UCC3806 looks like a good fit for my average current mode, flyback design.  However, I can't find any reference designs, eval boards, or simulation files.  Does any of this exist?  Also, I just want to verify that this device is a good choice for DCM flyback?

I have a 70Vdc source, and will have to output 3.3V, 5V, +/- 15V, and -60V, with a total output of less than 25W.

Thanks for your help   

  • Hello,

    The UCC3806 is a dual output controller though it can be used in a flyback where only one of the outputs are used to drive the switch it might be better to choose a single output controller. Look at page 46 of the attached under General Purpose Single- ended Controllers and choose a suitable device.

    Regards,

     

    John

    John Bottrill

    Power management guide 2011.pdf
  • In reply to John Bottrill:

    Thanks John,

    I;m thinking I can use the dual output controller if the output are in phase – to reduce the block voltage of the switch.  Can the UCC3806 be used as an average current mode device?

    Thanks again

  • In reply to Jamaal_Charles:

    Jamaal,

    Look at the block diagram on page 8. The T Flip Flop forces the outputs to be 180 degrees out of phase.

    The control loop is peak current mode control. For average current mode control you would need external components.

    Regards,

    John

    John Bottrill

  • In reply to John Bottrill:

    Thanks again John,

    The UCC2813D-2 looks like it may work.  Just to verify, is this a good choice for flyback ( single switch)?  One requirement I am confined by is to have a controller chip that has a 5V ref before other voltages are generated.

    -J

  • In reply to Jamaal_Charles:

    Hi Jamaal,

    There are 3 reference designs for flybacks that you can find on the UCC2813-2 product page.  You can find these by scrolling down to the Tools & Software section.  Here you will find the heading Reference Designs.

     

    Ryan

  • In reply to John Bottrill:

    Hi John,

    you know what the function of the NPN transistor connected to the CT, Vref and CS + pin.
    I Check some application notes and can not find an explanation of its function.
    Regards Carlos

  • In reply to Carlos Fangauf:

    Hi Carlos,  without seeing the specific schematic that you are referring to I would say that the added components are for slope compensation.  There is an application note, SLUA110, also known as U-111, that is from the old Unitrode days that has a lot of info for the "new" current mode power supplies that is on our TI website but I'll (attempt) to attach it here so you don't need to search it out.

    slua110.pdf

    Lisa Dinwoodie

  • In reply to Lisa Dinwoodie:

    Thanks Lisa for information, is exactly the explanation I need.
    Cordially Carlos

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