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flyback efficiency

Discussion in 'Electronic Design' started by dfarr --at-- comcast --dot-- net, Aug 4, 2007.

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  1. I'm wondering about the cost and power consumption of televisions and
    CRTs. I don't have enough knowledge of electronics to answer this
    question for myself.

    Does the process of moving the beam rapidly across the screen to begin
    a new scan line require a lot of power? Raster plotters draw in both
    directions to save time and total plotter head motion. Would there be
    any advantage to driving a CRT so half the scan lines were drawn right
    to left and half were drawn left to right, alternating directions on
    each scan line?

    I'm guessing one advantage of drawing all the lines in the same
    direction is synchronization, so what is the cost for doing it this
    way? Are there alternative ways to synch the lines on an analog
    display?
     
  2. Ken

    Ken Guest

    No.
     
  3. John Larkin

    John Larkin Guest

    Yes. The horizontal deflection system of a CRT uses far more power
    than the vertical, even for a 1:1 aspect ratio system. The horizontal
    deflection coil has to be low inductance, so needs lost od deflection
    current, and has to have very high voltages applied to it to slew the
    beam rapidly. All that takes a lot of power.

    But an LCD uses a fraction of the power of a CRT.

    Frame-sequential LED backlighting would be even better, if the LCDs
    could be made fast enough.

    John
     
  4. Ken

    Ken Guest

    But it's not "a lot of power".
     
  5. Ken

    Ken Guest

    "fraction" ???
    My 19" CRT monitor use 75W
    A normal 19" LCD monitor about 40-50W.
     
  6. John Larkin

    John Larkin Guest

    Tha ratio is typically 3:1 for small (15") screens, approaching 2:1
    for larger screens. 1/3 and 1/2 are both fractions. Look it up.

    John
     
  7. PeteS

    PeteS Guest

    The fraction is larger for smaller devices (common in HUDs and
    MultiFunction displays in aircraft).

    Cheers

    PeteS
     
  8. linnix

    linnix Guest

    You must have a very good CRT, if this is correct. I have two 17" CRT
    rated 1.5A and 2.5A (seems too high) @110V. I believe the actual
    usages are more like 150W to 200W.
     
  9. Ken

    Ken Guest

    Oh!
    Here the specification for my old CRT http://tekniken.se/misc/109b50.pdf
     
  10. Jasen Betts

    Jasen Betts Guest

    2/3 is a fraction.
     
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