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UCC28180EVM-573: UCC28180EVM-573

Sousan Manteghi
Prodigy 10 points
Part Number: UCC28180EVM-573
Other Parts Discussed in Thread: UCC28180, UCC28070EVM, UC3854, UCC2818, UCC28070, UCC28065

one of TI's tech support that their UCC28180 had been successfully used at the AC line frequency of 400Hz. We obtained their evaluation board, the UCC28180EVM, and gave it a good try. My results were not good. At 400HZ, high line, the power factor fell below 0.9. In addition, at frequencies above 400Hz, (where MIL STD 704F goes to 800Hz for "Variable AC") the parts looks hopeless.

Second: We tried a UCC28070EVM evaluation board which gave us mixed results. Power Factor was good all the way to 800Hz at 115V in. However, the harmonic distortion was out of spec the for the entire frequency range, all at 115V. This part has promise but I'll want some help experts in overcoming the THD problem. By the way I have some data for the proper TI expert. Another good aspect of this part is that the current is not leading the voltage. There seems to be zero degrees between voltage and current in contrast with the UCC28180 where the Power Factor is always leading.

Third: I have also been looking at several other TI parts such as: UC3854, UC3855, UCC2818, and UCC29065. I want to discuss the possibilities of which of these part(s), or any others, would possibly be usable here.

  • 0
    TI__Mastermind 26710 points

    Hello Sousan,

    Thank you for your interest in TI PFC controllers.

    I'm sorry that you obtained poor results when testing the EVMs at 400Hz+, however I believe you would see better results if the EVMs had been specifically designed for 400Hz+ input line frequency.  As such, they are designed for 50/60Hz operation and their component values and responses are tailored for that input.

    Consider that the input current is expected to follow the input voltage and the Avionic frequency is at least 7X that of the normal power line (420Hz vs. 60Hz), I suggest that you would see better performance from each device if their inductances were scaled by the inverse of that factor.  The UCC28180 EVM inductance is 327uH.  I believe the UCC28070 EVM performed better because its inductances are 150uH.  (The UCC28070 EVM uses lower inductance because it is taking advantage of interleaved ripple cancellation.)  I suggest that 327uH/7 = ~47uH with the UCC28180 EVM should have much better THD performance at the higher frequencies.  But, in addition, the ICOMP and VCOMP compensation components also need to be scaled to the appropriate values for this higher frequency range.
    A similar adaptation would apply to the UCC28070 EVM components.   

    The issue of leading PF I think comes from the input filtering capacitance.  The UCC28180 EVM has twice the X-cap on its input that the UCC28070 EVM does.  At 400Hz+, this capacitance current will constitute a significant fraction of the total input current.  Input filtering also needs to be scaled to the 400Hz frequency range to avoid significant leading current contribution.

    Finally, I think the older parts UC3854, UC3855, and UCC2818, should all be serviceable in such an application with the same considerations about the boost inductance, compensation values and input filtering.  The UCC28065 (not UCC29065) uses a transition mode constant on-time control method where I expect the on-times to be relatively short compared to those of 60Hz applications.  As such, turn-off delay due to highly non-linear Coss of super-junction MOSFETs may contribute a large amount of distortion to the current, since the FETs don't turn off when the controller tells them to turn off.  It can regulate output voltage and power, but the input current waveshape will be distorted, perhaps beyond what your application can tolerate.  (Turn-off delay will affect the CCM parts too, but I think it has a greater impact on iTHD with a TM controller, than with a CCM controller.) 

    I hope this helps clarify the limitations of the stock EVMs and suggests some opportunities for modification to test for better results at 400Hz.
    Note, if you do modify one or more of these EVMs for the high frequency, be aware that they will no longer provide good performance at 50/60Hz.

    Regards,

    Ulrich