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WEBENCH® Tools/UCC28631: AC-DC converter using JA4429-AL transformer

Part Number: UCC28631
Other Parts Discussed in Thread: UCC28700

Tool/software: WEBENCH® Design Tools

Hello all,

I am currently developing a 24V@1A DC power supply using UCC28631DR. For the initial design i used Webench, but couldn't find am off-the-shelf transformer. So I had to replace with the Coilcraft's JA4429-AL, That was the closest one I could find with the parameters given at Webench. I have adapted the voltage reference resistor that feed VSENSE to fit the turns ratio of the used transformer.

My question is if JA4429-AL would be a suitable replacment to work with UCC28631DR and, if there's any other modification that has to be made on the system aside from the VSENSE resistors.

The Webench design can be found at webench.ti.com/.../SDP.cgi

EDIT: I have attached the schematics of the converterUCC28631_converter.pdf

Thank you for the support.

  • Hello,

    Generally these design require custom transformers.  You could always ask Wurth or GCI to make the transformer for you.

    As long as the turns ratio, primary magnetizing inductances and RMS current ratings are similar within 5% it should work.

    I reviewed the TI reference design library and found a 85V to 265V AC to 24V 1A output using the UCC28700  PMP10648.  The following link will get you to the reference design.  http://www.ti.com/tool/PMP10468

    This is a DCM fly back controller similar to the UCC28631.  This design uses a Wurth transformer 750811647.  I believe you can order this from directly. 




  • For now we won't produce many units and the project is still a proof-of-concept, so ordering a custom transformer would be above our budget. I have contacted Wurth to see if we can get some samples for 750811647. The problem with that approach is that we use Mouser for must our purchases and they don't carry that particular transformer, that would create extra processes ordering components for the project. We are based in Canada, so a transformer supplier that sells low quantities in the country could be suitable.

    Right now, the best case scenario would be use the provided schematics, as maintaining those supply lines would be easier. My main concern with JA4429-AL is the turns ratio, that being Pri:Sec:Aux as 1:0.24:0.24. Would a Sec:Aux turn ratio of 1:1 be a problem to be used with UCC28631?


  • Hello,

    I think the Np/Ns =4.16 would be a problem is you are doing an 85V RMS to 265V RMS design.  At 70V the maximum output that could be achieve is 70/4.17 = 16.78V.  However, if you are just evaluating the concept the input would work as long as Vin  > 24V*4.17 = 100V.

    How close is the primary magnetizing inductance compared to what the WEBENCH tool calculated?  This will affect the maximum switching frequency and you should be able to ratio to see how far you off.  Please note if you exceed the maximum frequency that is recommend with the new transformer it will not work as well.