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UCC28951: Testing Procedure to bring up 2.5kW 48V PSFB Board

Nishant S
Prodigy 51 points
Part Number: UCC28951
Other Parts Discussed in Thread: UCC28950EVM-442, UCC28950, TINA-TI

Hello,

I am working on design of 2.5kW 48V PSFB DC-DC converter using UCC28951 Controller IC. (input voltage: 370 to 410 Vdc)

We tested using on-board UCC28951 IC by following the recommended test procedure given for UCC28950EVM-442 EVM with an electronic load set for 10% loading in CR mode (9.216 ohms).

We provided 400V DC at the Vin terminal and then provided the 12V auxiliary supply to the IC.

But two of the diagonal primary side MOSFETs were blown-off. Also, the input DC power supply ran into OCP protection at 2.75 Amps. 

So, could you please suggest the proper testing plan to bring up a PSFB DC-DC converter using UCC28951 IC.

Regards, 

Nishant

  • 0
    Prodigy 51 points

    Further we have tested the same board, using same loading, but now the auxiliary supply of 12V is given first and then we gradually increased input voltage from 0 to 100 volts. As we reached just above 100V of input voltage, one of the SR MOSFET blown off. The heat sink of the blown MOSFET was heated-up.

  • 0 in reply to Nishant S
    TI__Guru* 85696 points

    Hello,

    Your inquiry is under review and I will get back to you shortly.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru* 85696 points

    Hello,

    If your FETs are getting damaged more than likely in your design the FETs are being exposes to excessive voltage or over current.

    I would check the ratings of those components to make sure they are rated correctly.

    Next double check your schematic and design to make sure it is setup correctly. The following link will bring you to an application note that goes through the step by step design process of a UCC28951 in a phase shifted full bridge (PSFB).  You may find this information useful in checking your schematic for functionality.  https://www.ti.com/lit/pdf/slua560

    If your design was damaged at 10% load.  You might want to try troubleshooting the design with high voltage/high power DC source that has current and power limiting.  You would then limit the current and power to 15% load to protect the PSFB.

    Regards,

  • 0 in reply to Mike O'
    Prodigy 51 points

    Hello,

    These are the datasheets of the Primary side and Synchronous side FETs being used:

    - Primary Side MOSFETs (IPP65R060CFD7)

    - Secondary Side MOSFETs (IPP120N20NFD)

    The UCC28950/51 datasheet and particularly the excel tool were referenced to verify the calculations and selection of components.

    Also before testing the design practically, the simulation was also done in TINA-TI.

    The test was also done with 440V of OVP protection set on source at the input side.

    I have sent you a connection request where I can share the component details.

    Thanks & Regards,

     

  • 0 in reply to Nishant S
    TI__Guru* 85696 points

    Hello,

    We handle all the technical support on the e2e.  You should be able to use the following application note to check your schematic if you cannot share it on the e2e.  https://www.ti.com/lit/pdf/slua560

    Since you simulated the design in Tina you have a confidence in the design.  If the schematic checks out the other information given in troubleshooting should help you evaluate your design and prevent it from being damaged.

    I would recommend checking the CS, error amplifier output, input voltage of the transformer, switch nodes with an oscilloscope at 5% load and make sure they behave as expected.  You might want to load this with 5% and slowly bring the load up to evluate.

    Regards,