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UCC3895: UCC3895 - Power transformer configuration

Part Number: UCC3895
Other Parts Discussed in Thread: UCC28951


we are in the development stages of 10kW DC -DC Converter . PWM IC Selected is UCC3895. as per the design, there are three Power transformer for power transfer. Each transformer is responsible for 1/3rd of total power. Transformer configured as follows....

Primaries are connected in series and secondaries are connected in it right configuration?

Thanks and regards


  • Hello,

    I did not see a schematic attached but have seen designs done this way with LLC up to 4 transformers in series on the primary with the outputs paralleled to share current and they work fine.  So it could be possible with PSFB.  The following link will get you to an LLC reference design using a similar technique.  Please note I am not suggesting you LLC for your high power application.  It is to just to prove that what you are trying to do should be possible.

    I do have one concern the PSFB when it comes out of free wheeling this is generally a difference between the resonant inductor Ls and the primary magnetizing inductor Lpm.  To prevent the FETs from being damaged there is generally clamping diodes between the input bulk capacitor and Ls and the transformer primary winding.  Didoes DB and DC in the following application note will handle this in a single transformer application.

    In regards to your design I would put clamping diodes between the transformer primary connections just in case there is a slight mismatch in current during loading of the three transformers.  If you need SR drivers I also suggest you use the UCC28951 PSFB controller that has on board drivers.

    Your design is unique and I think it should be possible.  However, this is unexplored territory and it may not work because of some unknown reason.