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Original question:

UCC256404: Suggestion required

PMP8740: Increasing the output voltage

Basit Ali Khan
Intellectual 370 points

Part Number: PMP8740
Other Parts Discussed in Thread: PMP30092, , UCC28950

Tool/software:

Hi,

Need help in impementing the following requirements. For the reference boards I saw the PMP8740 that can provide the required outputs. Can I change the output voltage to 100VDC, is it programatically controlled. What other changes do I need to make in order to get the required output voltage? Secondly I don't need the LCD and buttons as this one will be a regular AC-DC supply without battery charging requirements... Also I believe the same PFC can be used to generate 24VDC as well following PMP30092 reference design then further voltage branches can be acheived by using buck regulators from it.

  • +1
    TI__Expert 6005 points

    Hi Basit,

    The PMP8740 is a variable output voltage battery charger; Vout can range 0 - 32V, with 62.5A maximum.

    In order to get 100V output, it needs to be redesigned in the secondary side section, therefore you need a new transformer, sync-FETs, clamping network, electrolytic capacitors, inrush current (hot swap) circuit rating, and loop compensation passive components fine-tuning.

    In your block diagram, you plan to replace the phase shifted full bridge DC/DC converter used in PMP8740, and even though it's feasible, LLC it's probably not the best topology to cover 1.8 kW. We have on TI.com an example of 1 kW LLC, driven by digital control C2000:

    https://www.ti.com/tool/PMP41081

    I am pretty sure it can be increased the output power up to 1.8 kW but with pretty much effort, so I would stick with phase shifted full bridge.

    Regarding the low voltage outputs, PMP30092 is a good candidate and can provide isolated 24V output, followed by Buck converters.

    Best regards,

    Roberto

  • 0 in reply to Roberto S.
    Intellectual 370 points

    Hi,

    Acutally at first I was about to use LLC but then found out that over 1KW PSFB is preferred therefore I will be using PSFB by taking reference of PMP8740. I was trying to get an idea about the changes related when increasing the output voltage to 100V. Also there is a MCU involved in its design, so how it is controlling the OV and OC.

    For PMP30092 I was thinking of using the same PFC circuit of PMP8740 and taking its 400VDC

  • 0 in reply to Basit Ali Khan
    TI__Expert 6005 points

    Hi Basit,

    I also believe selecting PSFB is a good choice for this power level.

    The changes needed to this DC/DC stage can be calculated by using the UCC28950 Excel calculation tool, available on product page of this part.

    Regarding the PFC stage, it delivers 2kW in Vin range 184V - 265V; down to 90VAC, it is limited to 1kW...1.1kW, so you may need to check whether the inductor can support the current and the MOSFETs and diodes as well.

    Regards,

    Roberto