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UCC28950: 1.5kW DC-DC converter using UCC28950 - 400V Input, 150V Output, 10A Output Current

Sambuddha Khan
Prodigy 90 points
Part Number: UCC28950
Other Parts Discussed in Thread: UCC28951, TINA-TI

Hello,

I am working on a design of 2kW DC-DC converter where the input is 380-400V DC and the required output is 150V. For this I would like to use UCC28950 Full Bridge Synchronous Rectifier. I would like to know if UCC28950 is a good choice for this kind of application. I used the SLUC222C, the Excel Design Tool for UCC28950 and came up with a solution. could you please let me know if I am doing it right. Please suggest if there is any mistake. I am not able to simulate the model in PSpice as the models for the mosfets mentioned below is not available Therefore, I have to design based on the excel design tool only. Therefore, I would like to get your expert opinion on this matter.

For Mosfets QE and QF, I have chosen the values from an Infineon Part - IPP110N20N3

For Mosfets QA, QB, QC and QD, the part selected is - IPW60R070CFD7

Regards,

SambuddhaUCC28950 Excel Design Tool_SLUC222C_140V_2kW.xlsxUCC28950 Excel Design Tool_SLUC222C_140V.xlsUCC28950 Excel Design Tool_SLUC222C_140V.xlsxInfineon-IPW60R070CFD7-DS-v02_00-EN.pdfUCC28950 Excel Design Tool_SLUC222C_140V.xls

  • 0
    TI__Mastermind 25570 points
    Hello Sambudda

    The UCC28950 is a good choice although the newer UCC28951 may work better if you need to operate at lower input voltages - during hold-up when the system is being turned off for example. The UCC28951 can be retrofitted into a UCC28950 application with no external circuit changes so you don't need to make a choice just yet.

    SLUC222C has been recently replaced with SLUC222D and there are some important differences.
    First - the transformer turns ratio calculation displays 2 decimal points - this is not significant where the turns ratio is high but is significant in your case where it is about 1.8.
    Second - the voltage stresses on the SRs are double those reported in the RevC document so the SR MOSFETs will probably be overstressed.
    I can't really comment on your choice of primary side MOSFETs other than to suggest that you contact Infineon to discuss this application.
    I would suggest you download SLUC222D off the UCC28950 webpage and rerun your calculations.

    For 150V out would be worthwhile looking into using SiC diode rectifiers instead of SRs - The gains using SRs will be small and the added complexity may not be justifiable - but that is a judgement you have to make.

    Regards
    Colin
  • 0 in reply to Colin Gillmor
    Prodigy 90 points

    Hello Colin,

    Thank you very much for your valuable insight.

    We have re-run the calculations in SLUC222D (the latest version) and used the same values in the simulation model. Hopefully we have chosen correct Mosfets to switch the DC Bus voltage in the Primary (QA, QB, QC and QD) and the SR Mosfets (QE and QF). As per the Excel design tool, the design looks fine. But when we try to simulate the same using the pspice model from “slum169a.zip”  changing the mosfets with the correct ones, changing  the transformer turns ratio and changing all the necessary passive components’ values as suggested by the excel design tool, we still stuck at the output which is 12 – 13 V. It does not even change with change in the load resistance or load current. Please note that we are running here the steady state simulation model. I am attaching all the necessary pspice models, mosfet library files, excel design tool, MOSFET datasheets. Please look into the .rar file for design and other details and help us to design the product that we are looking for. Please let me know what we are doing wrong.

    We have also communicated with Infineon on the their Mosfet IPW20R070CFD7 and they said it’s fine to use that Mosfet as they also use it for similar applications. I am attaching the similar application that they have published in their website. This application also talks about a 2 kW DC/DC converter design with 56V output using UCC28950 with Infineon IPW20R070CFD7 mosfets.

    We have also changed the existing SR mosfets to SiC Mosfet from RoHM namely SCT3022AL as per your suggestion. 

    If you need anything else, please let me know.1.5 - 2kW 150V DC-DC UCC28950.rar

  • 0 in reply to Sambuddha Khan
    TI__Mastermind 25570 points

    Hello Sambudda

    I'll try to look at this tomorrow but in the meanwhile please note that the transformer turns ratio in TINA-TI is different to what you might expect. Please review it - you could always simply put V meters on primary and secondary to see what is happening.

    Regards

    Colin

  • 0 in reply to Colin Gillmor
    Prodigy 90 points
    Hi Colin:

    We have checked with TINA-TI and implemented the same circuit there too. The output of the circuit is the same, clipped to 50V before the Lout and cout and 12V on Cout. I have made all the necessary changes including changing the Turns ratio, feedback resistors values, current sense resistors values, passive component values in the compensation network. Even then I got no luck. Please check my earlier post where I attached the PSPICE model. Please help me to resolve the issue.

    Regards,
    Sambuddha
  • 0 in reply to Sambuddha Khan
    TI__Mastermind 25570 points
    Hello Sambuddha

    Can you send me your TINA-TI schematic please. You can email it to me at colingillmor@ti.com

    The reason I ask is that I'm having some difficulty getting a PSpice simulator up and running - I have other open tasks for that simulator so I'll continue to work on it but in the meanwhile I should be able to answer your question more quickly if I can work with the TINA-TI files.

    Regards
    Colin
  • 0 in reply to Colin Gillmor
    TI__Mastermind 25570 points
    Hello Sambuddha

    I didn't receive your TINA-TI files - please feel free to send them to me if this issue is still open. In the meanwhile I'm closing this thread - we can always reopen it or open a new one.

    Regards

    Colin
  • 0 in reply to Colin Gillmor
    Prodigy 90 points

    Hi Colin,

    I have sent you all the designs including TINA files in your email. I was wondering why I did not receive any kind of acknowledgement from your end. Please look into your inbox, you might have missed it. If you are not able to find it, I will send them again.

    Regards,

    Sambuddha

  • 0 in reply to Sambuddha Khan
    TI__Mastermind 25570 points

    Hello Sambuddha

    I'm afraid I missed the files - thanks for re-sending. I may be able to get to them today, if not then tomorrow.

    Regards
    Colin

  • 0 in reply to Colin Gillmor
    Prodigy 90 points
    Hi Colin,

    Any update on the design? could you resolve the issue? Thanks.

    Regards,
    Sambuddha
  • 0 in reply to Sambuddha Khan
    TI__Mastermind 25570 points
    Since this topic has gone to email I'm closing this thread.
    Colin