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LM25575 inverting buck-boost mode

Prodigy 60 points

Replies: 5

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Hello,

I am designing a +/-12VDC supply based on LM25575 converters used in cascade. The topology consists to create a +12V from 24VDC (coming from PLC backplane). From the +12V we create the -12V by using the LM25575 converter in inverter mode.

The topology and peripherical components comes from the results of the WEBENCH designer tool. However, when I want to simulate the circuit, the -12V polarity doesn't work.

So, I would like to know if the problem comes from the topology or is it a limitation of the model ?

  • Hi Alexandre,

    We are looking into your request now and will get back to you shortly.

    Thanks,

    Anston

  • Hello,

    Would you please share your schematic and BOM simulated? If required, we could involve the engineers working in the Webench department as well.

    Regards,
    Akshay

  • In reply to Akshay Mehta:

    Hello,

    Please find hereunder the schmematic issued from Webench designer :

    The TI-TINA file is the following :

    0045.1385.Power_supply_testbench.TSC

    and the associated BOM is : 2112.2425.BOM_PS_management.txt

    Thanks for your reactivity and your support,

    Alexandre Penaud

  • In reply to Alexandre Penaud:

    Hello Alexandre,

    It looks like you are trying to use TINA to simulate the model. I am going to have to involve the modeling engineers to take a look at why the sim is not working. As such I don't see anything blatantly wrong with the design. Laying it out properly would be very important.

    Regards,
    Akshay

  • In reply to Akshay Mehta:

    Hi Alexandre,

    I believe the current TINA model for this was made for Buck topology only.

    Because of the way SPICE sims specially recognize a node 0 as a global GND, even in subcircuits, any internal IC references to 0 in a model make it so its GND referenced, so if in an inverting Buck Boost topology where the IC is referenced to another voltage, the simulation would not function properly.
    So its not a problem with the actual design, its a model issue.

    Best regards,
    Tommy

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