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Need controller for 3 Ph PFC to be implemented on a per phase basis.

Robert Stowe
Prodigy 50 points
Other Parts Discussed in Thread: UCC28070A, UC2854A, UCC28180

I am looking for a suitable PFC controller for a design receiving three phase power. I desire to implement one boost converter for each phase, followed by a full bridge. Requirements:

-Each phase should process about 1kW.
-The input frequency is 380Hz to about 700Hz.
-The input voltage is TBD depending on whether the PFC stages will be delta connected or wye connected.
-The performance requirements are not super stringent, so a first order cut at active PFC should suffice.
-I want to synchronize the three phases and DC-DC to mitigate beat frequencies.

So far I have narrowed the choices to UC2854A/B, and UCC28070A. Questions:

The UC2854A indicates useability up to 400Hz line with a 5MHz GBW on the currrent amplifier. Can this device do OK at 700Hz? Again, the performance requirements are not super stringent, so a first order cut at active PFC should suffice.

The UCC28070A can provide interleaved functionality which will help with packaging / EMI filtering / dissipation, but does not specify current amplifier GBW or max line frequency. Can you provide the GBW for this device?

Are there any devices more suitable that I have missed?

Thanks!

  • 0
    TI__Mastermind 34465 points

    You can use the UCC28070A in a wye connected AC source as shown below:



    This method requires a separate controller for each phase with all controllers being synchronized by a master clock.

    The big advantage of this method is low capacitance requirement and enhanced harmonic performance.

    The UCC2854A has traditionally been used on the DC side of a 6 diode 3 phase rectifier.
    The advantage of this method is simplicity of control but it has the big disadvantage of poor harmonics
    But it is still possible to achieve power factors of greater than 0.9

    You may also wish to consider the UCC28180 controller.
    This has also been used in 400Hz aircraft applications both with MOSFETS and IGBT's
    It is a newer part than the UCC2854A and it is simpler to implement with a lower component count.

    The GBW of the UCC28070A is not available and this may be simply because the current amplifier is a synthesized type of amplifier that calculates the current downslope rather than  traditional analog amplifier.

    John Griffin

  • 0 in reply to John Griffin1
    Prodigy 50 points
    Hello John,

    Thanks for your reply and information.

    Is there any reason why the UCC28070A (or any other capable PFC IC for this application) could not be used in delta connected boost PFC's? This is a possibility since there would be a lower EMI filter part count and simpler layout since the neutral does not have to propagated.

    Your drawing shows a master clock with 120 degrees phase shifting for each phase. Would this phase shifting multiply the interleaving effect by a factor of 3 for the line input currents? So for a UCC28070A, which already has a two phase interleaving by itself, would the input line current from the three phase source have a switching ripple frequency of 6X the controller switching frequency?

    Is it possible to provide an external sync signal to the UCC28180? If so, how? Is there a simulation model for the UCC28180?

    Can the UC2854A, UCC28070A, UCC28180 provide usable performance at line frequencies of 700Hz?

    Is there a simulation model available for the UCC28070A, UCC28180, UC2854A?

    Thanks!
  • 0 in reply to Robert Stowe
    TI__Mastermind 34465 points
    Hi Robert,
    The UCC28070A can be used in a delta connected boost with a 6 diode bridge rectifier and it has been used in this configuration by many customers. The problem with this configuration, as you know, is that the line currents will be more like a square wave than a sine wave and you may find that you will not be able to meet any harmonic limits that are required. This would be a single controller for 3 phases and I understood your requirement for a controller for each phase. Unfortunately I do not have a setup to relate regarding a delta connected source with a controller for each phase.
    Your second point about the 6x nature of the ripple on the block schematic is correct. You would see effectively 6 times the switching frequency on the input and output caps.
    The UCC28180 cannot be synchronized with an external source. Some of the PWM controllers can be synchronized externally but these have an RC timing network and the sync signal can be tied to the voltage on the timing cap but unfortunately the UCC28180 does not have this feature.
    All of these parts have been operated at 700Hz.
    Models of these parts should be available. Please check the website location:
    www.ti.com/.../TINA-TI

    Regards,
    John