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UCC28070A: 3.3KW to 6.6KW

Venkatesh B
Intellectual 732 points
Part Number: UCC28070A
Other Parts Discussed in Thread: UCC28070

Tool/software:

Hi TI Team,

I am using UCC28070A Interleaved PFC IC for 3.3KW AC to DC front end section and working fine

I would like to change same schematic to 6.6KW ~7KW,what changes require to implement this.I may use Excel calculation sheet.apart from that anything i need to consider kindly advice

will this IC support 6.6KW PFC operation? layout changes if any.do give suggestion please

Thank you

venkatesh  B

  • 0
    TI__Mastermind 34280 points

    Hello Venkatesh, 

    The UCC29070A controller can theoretically support any power level, because all control and sensing signals are scaled to the controller input ranges.
    The only limitations to actual power are practical considerations of how to handle high currents and voltages.  7kW is not a problem for the UCC28070A. 
     
    If you simply wish to double the output power from 3.3kW to 6.6kW, I suggest 2 options:
    1.  Recalculate all parameters using the Excel calculation sheet, or
    2.  Duplicate the existing 3.3kW design and connect two PFCs up with 4-phase interleaving as shown in Figure 6-1 (page 20) in the UCC28070A datasheet.

    Option 1 requires all new design of all components, while Option 2 only requires designing an external synchronization clock.

    If you wish to extend Pout to 7kW, then Option 1 is still the same, but Option 2 is modified such that you should evaluate component temperature rises if you increase the maximum loading on your 3.3kW design by +6.1%.  If the thermal performance is satisfactory, then only a few circuit tweaks may be necessary. 


    In both cases, when output power is doubled, then conversion losses are doubled, so thermal cooling capability must be doubled to keep temperature rises the same. 

    If the PCB layout for the 3.3kW design is successful, then a similar arrangement should work for 6~7kW.  Gross changes in layout are most likely driven by overall packaging changes for the larger PFC and post-regulator.  

    Regards,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Intellectual 732 points

    Hi ulrich,

    Thank you for your response.

    Which will be high efficiency, Interleaving PFC IC or single PFC IC with 6.6KW design

    currently PFC efficiency is about 97%.if loss doubles effieciency drops,overall system efficiency droops

    I want higher efficiency

    Thank you

    venkatesh B

  • +1 in reply to Venkatesh B
    TI__Mastermind 34280 points

    Hello Venkatesh, 

    The loss doubles because the total output power doubled.  The ratio of loss to output power stays the same, so system efficiency stays the same. 

    I mentioned the additional loss because it will need additional cooling and revised packaging.  You asked: "apart from that anything i need to consider kindly advice", and that is something that I believe should be considered. 

    To gain a little more efficiency you will need to consider some form of bridgeless or semi-bridgeless PFC.
    Here is a reference design https://www.ti.com/tool/PMP40261 for an 800W bridgeless PFC converter using the UCC28070.
    It achieves ~98% efficiency with 230Vac input, and I assume for 6.6kW you will not be using a low-voltage input.  Please correct me if I am wrong. 
    Although it is for 800W, the design can be scaled to higher power levels. 

    Regards,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Intellectual 732 points

    ok thank you ulrich,i will go through it

    Thank you

    venkatesh B

  • 0 in reply to Venkatesh B
    Intellectual 732 points

    Hi ulrich,

    Yes i am not using low voltage line,190V AC to 265V AC operating range

    One more question , Bridgeless PFC & Interleaved PFC are same right? except Input diode bridge rectifier

    180 deg phase shift happens or not in case of using UCC28070 for Bridgeless operation

    Thank you

    venkatesh

  • 0 in reply to Venkatesh B
    TI__Mastermind 34280 points

    Hello Venkatesh, 

    Bridgeless PFC is not the same as Interleaved PFC. 
    The UCC28070 controller is used to implement bridgeless PFC because the 2 PWM output (GDA and GDB) can be used to drive the boost stages for the opposite halves of the AC line.  In this bridgeless implementation, there is no interleaving. 

    In bridgeless PFC, GDA and GDB are still always phase-shifted by 180 degrees, but it does not matter.  GDA and GDB drive both MOSFETs all the time, but only one inductor carries line current during a half-cycle of the line. The other inductor carries current during the other half of the line cycle.

    Regards,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Intellectual 732 points

    Dear ulrich,

    can i use same excel sheet calculator for Bridgeless PFC implementation using UCC28070,will Input current ripple cancel at D=0.5? at this same operation

    Kindly let me know design steps for Bridgeless Interleaved PFC

    Thank you

    venkatesh B

  • 0 in reply to Venkatesh B
    TI__Mastermind 34280 points

    Hello Venkatesh, 

    Unfortunately, the existing UCC28070 Excel calculator tool cannot be used for bridgeless implementation of the UCC28070.  It was not designed to support that topology. 

    As I mentioned above, when using the UCC28070 in a bridgeless PFC, there is no interleaving, so consequently there is no ripple current cancelation at the input or output.  Also, pure bridgeless PFC has some issues with common-mode EMI, so you are more likely to implement a semi-bridgeless topology which mitigates the EMI problem. 

    Please refer to this App-Note on the topic: https://www.ti.com/lit/pdf/slua517  which discusses the differences in calculation. 

    Many other papers on this topic can be found at this link: https://www.ti.com/sitesearch/en-us/docs/universalsearch.tsp?langPref=en-US&nr=677&searchTerm=bridgeless%20pfc#q=bridgeless%20pfc  
    They typically involve controllers other than the UCC28070, but they may contain additional information about the principles of the various forms of bridgeless PFC.  

    Regards,
    Ulrich