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Original question:

UCC27714EVM-551: About cause of destruction of evaluation board

UCC27714EVM-551: Powering VBIAS/VBIAS2

Shota Mago
Expert 8110 points
Part Number: UCC27714EVM-551

Hi team,

In accordance to below thread, there is description that "If you share the Vbias supplies both bias supplies turning on and off at the same time is OK.".

http://e2e.ti.com/support/power-management/f/196/p/834394/3096649#3096649?jktype=e2e

Is it possible to power VBIAS and VBIAS2 by same supply eventhough VBIAS and VBIAS2 are isolated?

Best regards,

Shota Mago

  • 0
    TI__Mastermind 23015 points

    Hello Shota,

    It is possible to share the VBIAS and VBIAS2 with the same supply which will mean the two grounds will be referenced to each other.

    In this case, to have a safe setup, you need to have an isolated supply for the high voltage 390V input so that the primary ground can be referenced to the controller ground in the test setup.

    Confirm if this addresses your question, or you can post additional questions on this thread.

    Regards,

  • 0 in reply to Richard Herring
    TI__Expert 8110 points

    Hi Richard

    Thanks for your answer.

    Let me clarify my understanding.

    When powering VBIAS and VBIAS2 from same supply, the supply should be referenced to primary GND.

    On the other hand, the high voltage input should be referenced to secondary GND(PWRGND).

    Is this understanding correct?

    But in this case, I'm not sure how much voltage will be at VBIAS2-PWRGND...

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Mastermind 23015 points

    Hello Shota,

    On the board the high voltage input is referenced to the primary ground which is called PWRGND on the schematic. VBIAS2 is the primary bias supply which is also referenced to the primary ground, or PWRGND. VBIAS is the secondary bias which is referenced to the secondary ground which is called GND on the schematic.

    If you share the VBIAS and VBIAS2 the bias grounds need to be connected to provide the bias voltage relative to ground. This will result in the PWRGND connected to GND. If your bench setup has a floating, or isolated input power supply, this connection can be made and still have a safe bench setup. Many bench tests are performed with this setup which allows scope probes to be connected to primary signals and also secondary signals.

    You need to confirm that you have an isolated input power supply source, if so this configuration can work.

    Confirm if this addresses your questions, or you can post additional questions on this thread.

    Regards,

  • 0 in reply to Richard Herring
    TI__Expert 8110 points

    Hi Richard,

    Thank you so much for your detail explanation.

    This answer solved my question.

    Best regards,

    Shota Mago