Inverting buck-boost converter

Discussion in 'General Electronics Chat' started by anhnha, Feb 16, 2016.

  1. anhnha

    Thread Starter Well-Known Member

    Apr 19, 2012
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    This is an inverting buck-boost converter. As you can see in the picture, the output voltage is in the oppositive sign with the input.
    Assuming that we want non-inverting output voltage, why shouldn't we just swap the output reference to get the positive?
    I mean, for example, Vab = Va - Vb= -5V then Vba = Vb-Va= 5V. So why not choose Va as reference and have positive output voltage?

    Buck-Boost Negative Output Voltage.PNG
     
  2. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    Nothing on the schematic is marked Reference, Va, or Vb. Please try again.

    And note that the input and output share a common Ground connection. For a non-isolated converter, "swapping the output reference", if I understand what you mean by that, can cause problems for circuits with other external connections.

    ak
     
  3. anhnha

    Thread Starter Well-Known Member

    Apr 19, 2012
    783
    49
    Thank you. What will happen if the input and output don't share the common ground? Could you list some problems here?
     
  4. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    For that condition you need a very different circuit, one with a fully isolated transformer. With almost any isolated topology, the output reference can be either output polarity.

    ak
     
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