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UCC28064A: UCC28064A

Stuart Linzer
Intellectual 260 points
Part Number: UCC28064A
Other Parts Discussed in Thread: UCC25640EVM-020, UCC28064EVM-004, , UCC256404

Hi Tech Support, 

Designing power supply for Avionics application with 400Hz line frequency.  Using PMP30763 as a design guide.  

Also working with UCC25640EVM-020 and UCC28064EVM-004 evaluation boards.  At this time running tests at about 60W load and 115VAC input.  

I would like help with is the following.  When running the PFC evaluation board (UCC28064EVM-004) with a resistive load, Power Factor remains high (above 90%) with a 400Hz line frequency.   

Even at 800Hhz, power factor remains high.  

Next step, I connect the PFC evaluation board to the LLC evaluation board (UCC25640EVM-020).   Resistive load is connected to the LLC board and adjusted for the same power as before. 

Running at 60Hz Power Factor is high (0.942).  But as line frequency is increased the power factor drops.  At 400Hz power factor is very low at 0.49.  

What might be happing here causing low power factor when the LLC power supply is used?  Again when running at 60Hz with the LLC board, PFC power factor is high.   Also with just the PFC board, Power Factor remains high at 400Hz. 

Regards, 

Stuart

  • +1
    TI__Genius 9140 points

    Hi Linzer,

    thanks for your interest in UCC28064A and UCC256040 series controllers.

    when you compare PFC+resistor direct load and PFC+LLC+resistor load for the power factor, you may need to only use the input circuit from UCC28064AEVM, and remove the X cap on LLC EVM. So try to move C40/C41/C39 in the LLC evm to get out of the influence of LLC EVM input and check it again.

    Please also make sure UCC256404 on the LLCevm board needs ac zero crossing signal to get start up and realize the X cap discharge feature.

    and make sure you do the comparison at the load when LLC get out of burst mode.

    hope this helps you.

  • 0
    Intellectual 260 points

    Hi David, 

    Yes that resolved the issue.  PFC have high PFC with both resistive and LLC + resistive load.  Thank you. 

    Stuart