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Original question:

UCC28600: SMPS Transformer for multiple windings

UCC28600: 2nd and 3rd Step is not understanding

Vivek Sen
Prodigy 90 points
Part Number: UCC28600

Tool/software:

Dear Team,

I am using the spreadsheet of UCC28600, and I found there is only one output provision, but I am designing 200W SMPS with 3 phase AC input for multiple output about 7 outputs.

So, what I need to do with this spreadsheet to fulfill my requirement.

Can I get modified version of this spreadsheet for multiple outputs?

Hello,

 You can use the excel tool for a multi output design.

  1. Design it for output 1, for the total output power of the design. For example, if you have seven 10 W outputs.  You would set the output power for 70 W and the output voltage for output 1.  This will give you the correct primary magnetizing inductance and the correct electrical components for the primary power stage.
  2. Change Output 1 to the correct output power level. You can then use the calculations to give you the correct output components for the power stage.
  3. Change the output in the tool to Output 2 and set the output power and output voltage. The tool will then calculate the primary to secondary turns ratio for that output.  The tool will also help you select the output components for output 2.
  4. You can continue this for Outputs 3 through 7.

Please explain 2nd and 3rd step in deep with some of example I have 15V, 48V, 24V 18V ... outputs total output power 200W

  • 0
    TI__Guru* 86036 points

    Hello,

     

    Do to high volumes your inquiry will be answered in the order that it was received.

     

    Regards,

  • 0
    TI__Genius 12795 points

    Step 2 means that you treat your multi rail design as a single output design (pick the most power demanding one as I suggested in another thread). Run the calculator and get the corresponding power stage parameters (use them for the entire design). Then you can enter your second Vout option, but change the power level to that specific rail, run the calculation again. so on so forth to get the winding ratio for each rail. 

  • 0 in reply to Ning Tan
    Prodigy 90 points

    Dear Ning Tan,

    As you said "Then you can enter your second Vout option, but change the power level to that specific rail, run the calculation again" If I try this there will be change in Ipeak_Primary and L_Primary So our Ipeak_sec and Irms_sec  for that particular secondary winding will also get changed (not be accurate) and I need Irms_sec for each winding to calculate the wire size. 
    Now Advise me how I can fix this issue.

    So please explain If there is any method to calculate the secondary turns (N_sec), Ipeak_sec, Irms_sec for all 7 outputs in my design.

  • 0 in reply to Vivek Sen
    TI__Guru* 86036 points

    To calculate the peak and transformer RMS current for your design you can do the following using the excel design tool. 

    For example, if you have two outputs; Vout 1 = 12 V, 30 W; Vout 2 = 24 V, 10 W.

    1. First, enter your input voltage and output voltage for Vout 1 in the excel tool. Then enter the total output power for the two outputs.  In this case the total output power would be 40 W.  This will give you the correct primary to secondary turns ratio for Vout 1.  The tool will give you the correct primary magnetizing inductance for the transformer; as well as, the correct transformer primary peak and RMS currents for the system.
    2. Next, change the output power in the excel tool to the correct output power of Vout 1, which is of 30 W. The tool will give you the correct transformer secondary winding peak and RMS current for Vout 1.
    3. Next change the output in the excel tool to the output voltage of Vout 2, Vout = 24 V and the output power to 10 W. The excel tool will give you the primary to secondary turns ratio for Vout 2.  The tool will then calculate the peak and RMS current for the secondary winding out Vout 2.

    Regards,