LTspice: singular matrix

Discussion in 'General Electronics Chat' started by tom66, Nov 20, 2010.

  1. tom66

    Thread Starter Senior Member

    May 9, 2009
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    I am designing a buck regulator LED power supply in LTspice. I'm trying to add an optocoupler on/off switch to it (which will be an option.) When the opto is ON, the output should be OFF (which is controlled by turning off the standby supply reducing consumption to a few microamps), and vice-versa. However, LTspice is giving me odd errors:

    Does anyone know what's wrong?
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    Put a ground on V1.
     
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  3. retched

    AAC Fanatic!

    Dec 5, 2009
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    That should do it.

    Post your asc file, as well as any non-standard models.

    It will make following along that much easier.
     
  4. tom66

    Thread Starter Senior Member

    May 9, 2009
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    Okay, but doesn't that make it non-isolated? (I presume this is only a simulation bug/limitation?)

    See attached.
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
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    Spice requires a ground reference.

    It checks to see if there is a ground in the schematic, but doesn't check to see if it is in the proper places.
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    I am not sure if you can tell spice to use to different grounds. In reality it will work with two isolated grounds but here it needs to have ground every where to work.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Tom66,
    I can't load that .asc file; my LTSpice doesn't like it one bit.
    Did you upload a shortcut to the .ASC file instead of the actual .asc file?
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    I couldn't get it to load either.

    Ahh... You uploaded the plot setting file:

    Code ( (Unknown Language)):
    1.  
    2. Title: * C:\Documents and Settings\Thomas\My Documents\LED driver-5.asc
    3. Date: Sat Nov 20 15:01:43 2010
    4. Plotname: Transient Analysis
    5. Flags: real forward
    6. No. Variables: 98
    7. No. Points:            0
    8. Offset:   0.0000000000000000e+000
    9. Command: Linear Technology Corporation LTspice IV
    10. Backannotation: u3 1 2 200 300 101
    11. Backannotation: u2 1 2 200 300 101
    12. Backannotation: u1 1 2 3 4 5 6 7 8
    13. Backannotation: u4 1 2 3 4 5 6 7 8
    14. Backannotation: u5 1 2 3 4 5
    15. Variables:
    16.     0   time    time
    17.     1   V(n001) voltage
    18.     2   V(n005) voltage
    19.     3   V(n003) voltage
    20.  
    21. etc....etc...
    22.  
     
  9. tom66

    Thread Starter Senior Member

    May 9, 2009
    2,613
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    Ah, silly me. Try this file.
     
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