Supply +12v 0v and -12v with a 24v power supply

Discussion in 'Power Electronics' started by killerisation, Aug 25, 2016.

  1. killerisation

    Thread Starter New Member

    Aug 25, 2016
    6
    0
    The manual states I need the following analog power supply:

    0.3A @ +12 to +15V (4.5W)
    0.25A @ -12 to -15V (3.8W)
    The positive supply – +12V to +15V – should be brought in on the A+15V line on pin 59.
    The negative supply – 12 to -15V – should be brought in on the A-15V line on pin 60.
    The analog common should be brought in on the AGND line on pin 58.
    I plan on using the 34V 3A version of this:
    http://www.ebay.com/itm/Universal-2...-Driver-110V-240V-for-LED-Strip-/351139238715

    Can someone confirm that this will work, and describe the circuit needed?
    Thanks
     
  2. killerisation

    Thread Starter New Member

    Aug 25, 2016
    6
    0
    Should say 24v not 34!
     
  3. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    To get ±12V from a 24V supply you need a rail-splitter circuit.
    Here are some ways to do that.
     
    killerisation likes this.
  4. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    If either the supply or load is floating; you can use a splitter as crutschow says. If the current is pretty much constant; you might get away with a simple voltage divider. If the load is more unpredictable, you can buffer the resistor divider with an op-amp - for the current you mentioned; you will need to buffer the op-amp with a complementary pair of power transistors in emitter follower. You have to include the transistors in the op-amp nfb loop to make them behave.
     
  5. killerisation

    Thread Starter New Member

    Aug 25, 2016
    6
    0
    I've decided to just get a +/-12v power supply instead.
     
  6. killerisation

    Thread Starter New Member

    Aug 25, 2016
    6
    0
    Though I was wondering, could I use a 12v and a 24v power supply, with a common +rail, and the 0v rail of the 12v supply connected to GND?
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    For 300mA - you can probably get away with a pair of wall-warts.

    They're usually double insulated with no internal earth connection to the low voltage side.

    If its only 2 pin, you're all set. 3 pin wall warts often have a plastic earth pin that's only there to open the safety shutters on the wall socket.

    Very few wall warts have a brass earth pin - its simple enough to check no continuity to the low voltage side.
     
    killerisation likes this.
  8. killerisation

    Thread Starter New Member

    Aug 25, 2016
    6
    0
    I actually already have a 12 & 24v supply, I just wondered if there are any issues with connecting them as described?
     
  9. SLK001

    Well-Known Member

    Nov 29, 2011
    811
    224
    Yes, that will work, provided they are both transformer based supplies and both are floating.
     
  10. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    No, because the current from the +24V supply would have to flow through the +12V supply backwards and a typical power supply cannot sink current unless they are expressly designed to do so.
     
  11. killerisation

    Thread Starter New Member

    Aug 25, 2016
    6
    0
    Darn!
    Thanks anyway.
     
Loading...