Help with begginer circuit

Discussion in 'Embedded Systems and Microcontrollers' started by John Brkic, Nov 20, 2014.

  1. John Brkic

    Thread Starter New Member

    Nov 20, 2014
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    0
    Hi,

    I have created a dc-dc booster using the AS1326 which has been designed specifically for this purpose. The problem is that I want to put 4 of these circuits into one PCB and I need the output to be unified. For example:I will have 4 dual inputs (+, -). The input for one single IC (AS1326) will vary from 0.7 to 5V and the outpt will be a fixed 3.3V. The problem is that I dont know how to connect the 4 outputs and add their voltaged together into one output. Is conecting the ICs together an option? Should I use a component that will unify all the 4 outputs and add them together to fom an output of 13.2V? Thanks in advance and apologies if my question is a too begginer one. Pleasee see icon and datasheet attached.

    Regards
    John
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    Hi John, welcome to the forums.

    Are the input voltages all separate and independent and (most importainly) isolated from each other?

    If so then stacking them up should work to add the voltages together.

    If not, you're making one big short.
     
  3. BobTPH

    Active Member

    Jun 5, 2013
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    114
    Are you sure that is what you want to do? The current will be limited to that of the smallest source.

    Bob
     
  4. John Brkic

    Thread Starter New Member

    Nov 20, 2014
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    Hi guys,

    First of all thanks for your replies.
    @ErnieM I forgot to mention the input setup. I have 4 TEGs and each TEG will be connected to each IC (AS1326). So yes the input voltages are independent and isolated from each other. The circuit I did (on Eagle) is exactly the same a shown on figure 19, at page 11 of the datasheet.

    @BobTPH I would certenly wouldnt want to limit the current to that of the smallest source since it is very important to get as much power as possible from the output. I just need to have 4 dual inputs and one output on one board.
     
  5. BobTPH

    Active Member

    Jun 5, 2013
    782
    114
    Combining dissimilar power sources to get the most out of them is not an easy task.

    One way would be to boost each one to the same voltage, then parallel them, with some small resistors in series so that each contributes what it can.

    Bob
     
  6. John Brkic

    Thread Starter New Member

    Nov 20, 2014
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    Hi @BobTPH ,

    The ouput voltage will be fixed at 3.3V for all 4 outputs. The current will vary. Wouldnt the resistors drop the voltage? And by saying parallel them with resistors in series you mean somrthing like this?(see pic).
     
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  7. BobTPH

    Active Member

    Jun 5, 2013
    782
    114
    No, connect one end of each resistor to each source, and the other end of all the resistors together to make the output.

    The purpose of the resistors is to make up for small differences in the voltage of the sources. They should be small, designed to drop maybe 100mV at the expected current.

    Oh, and the output voltage will be 3.3V since they are paralleled.

    Bob
     
  8. iimagine

    Active Member

    Dec 20, 2010
    129
    9
    You would likely receive more help if you post this in 'The Project Forum'
     
  9. John Brkic

    Thread Starter New Member

    Nov 20, 2014
    5
    0
    Thanks iimagine will do.
     
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