Paralleling PSUs

Discussion in 'General Electronics Chat' started by MachineHum, Feb 16, 2015.

  1. MachineHum

    Thread Starter Member

    Nov 3, 2014
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    I'm designing a system that will allow paralleling of power supplies to increase the max current from the system... Essentially the board takes VDC in and will give +1/2VDC, -1/2VCD and a virtual ground...

    Right now i'm biasing VDC at 1/2VDC with a voltage divider, then feeding that into the non-inverting inputs of an opamp... the output of the opamp is fed into the base/base junction of two BJT transistors... the feedback is taken from the output of the two transistors in a totom-pole config... See picture (Left only)
    [​IMG]

    This works fine... the transistor will run hot because they're dissipating lots of power (1/2Vcc * Ice)

    If I was to put this system in parallel... I'm sure there would be problem, the outputs would have a slightly different potential and the PSUs would fight each other...

    I'm thinking that if the system can be hardware configurable, one as a master and one as a slave... the master taking Vref from it's own voltage divider and the slave a taking its voltage reference from the masters voltage divider... this may work... as both op-amps will have the same voltage reference and ideally they will keep the output at the correct voltage... does this make any sense?
     
  2. bance

    Member

    Aug 11, 2012
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    34
    You are trying to build a dual tracking power supply, you could try using a discrete voltage ref such as a TL431.

    HTH Steve.
     
  3. MachineHum

    Thread Starter Member

    Nov 3, 2014
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    Interesting ... so it's technically something that already exists? I'm assuming that "dual" part of the name means that the semiconductors are doubled up ... allowing for more current ... not duel output?

    As for the shunt regulator, I don't really want a certain voltage, I just want 1/2Vcc, so i'll most likely stick with the resistors
     
  4. bance

    Member

    Aug 11, 2012
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    I'm sorry I'm confused, are you saying that you have a transformer that produces twice the voltage you require but half the current?
    Perhaps you should post a complete schematic.
     
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
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    How much current are you wanting from the output?
     
  6. MachineHum

    Thread Starter Member

    Nov 3, 2014
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    I don't have a desired current... the idea is each system will have a different current requirement, to match the requirement you just add more power supplies... I think I failed to mention that there can be more then one slave
     
  7. MachineHum

    Thread Starter Member

    Nov 3, 2014
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    No it's not AC to DC, it's DC to DC

    24VDC in ... or 12VDC in, It doesn't matter. Then +-(1/2)Vin with a virtual ground... It's basically a single supply to split supply that can sink/source a few amps worth of current.
     
  8. MachineHum

    Thread Starter Member

    Nov 3, 2014
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  9. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Here is a pretty simple one. Just add 317s as the current goes up.
    Make R7 adjustable to set exact voltage.
     
  10. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Sorry, I just noticed you need to be able to both sink and source current so the above won't work, but the same principal might. Just close the loop on the other side of the resistors. Are you sourceing motors or something like that?
     
    Last edited: Feb 16, 2015
  11. MachineHum

    Thread Starter Member

    Nov 3, 2014
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    Thanks, that design is good to have in the back of my head anyways. It's going to be used for op-amp rails and drive current for B type amps.
     
  12. ronv

    AAC Fanatic!

    Nov 12, 2008
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    So it probably would work since there is nothing trying to raise the voltage like when you reverse a motor without stopping. You might want a bigger regulator, like an LM350 so you can get to 2 amps.
     
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