Help upgrading CFL circuit? Want to drive cfl's up to 25w

Discussion in 'General Electronics Chat' started by Clark44, Aug 26, 2014.

  1. Clark44

    Thread Starter New Member

    Aug 11, 2014
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    0
    Hello

    I have this circuit which i built, it can drive cfl's up to 15w, do u think it can be modified so that it can drive cfl's up to 25w?
    I have used D313 fot his project as the D882 didn't gave me the results i needed.
    Right now i am using a 12v battery, do u think the transformer i made for this circuit can be used for the famous Jeanna's light (Joule's Thief). If yes then how it would connect on the circuit? I will be making two or three more transformers like this.


    Regards!
     
  2. wayneh

    Expert

    Sep 9, 2010
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    The only way to get more power from the existing circuit would be drive more current thru the coil. I think you'd need a bigger transistor to accomplish that, but the transformer wiring may be the limiting factor. Hard to tell without more details about the wire gauge, length, core material and so on. Does it get warm with the existing wiring?
     
  3. ian field

    Distinguished Member

    Oct 27, 2012
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    The blocking oscillator/inverter is much easier to design by trial and error than attempting the maths involved!

    Maybe cut the primary down to 20t, but use thicker wire to fill the same space.

    Increasing the secondary is less likely to be beneficial as the tube has a gas discharge potential - a small increase in voltage gives a steeper rise in current.

    A very small advantage can be gained by selecting a low VCEsat transistor.
     
  4. Clark44

    Thread Starter New Member

    Aug 11, 2014
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    Primary and feedback is winded using 28 awg and secondary using 32 awg.
    Core material is ferrite.
    Don't know the length.
    Feedback turns are exactly 18, primary is 27 and secondary is 250.

    Just to let you know i did this experiment and added more turns on the secondary about 100 more making total 350. It ran at first without giving any more power or brightness in the cfl then transformer started giving strange noises and sparks, turned it off and since then its not running anymore. When i connect the power all that is happening is the transistor is getting extremely hot within 5 seconds.
     
  5. ian field

    Distinguished Member

    Oct 27, 2012
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    When the gas in the tube strikes its a bit like a bidirectional zener, increasing the secondary turns will increase the voltage it tries to produce but the crest current rises to a greater proportion and basically shunts it out.

    Thicker wire on the secondary winding might do more good, especially if increasing the amount of drive stresses the transformer so it gets hot.
     
  6. Clark44

    Thread Starter New Member

    Aug 11, 2014
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    Well the thing is getting hot is transistor not transformer. As i said earlier i tried increasing the turns to secondary, but transformer stared giving sparks and noises and since then its more like dead and at the same time transistor is extremely hot.
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
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    Normally, an overheating transistor indicates saturation - but the whole basis of the blocking oscillator is saturation.

    If you give the transistor too much base bias, the collapsing field as the inductor saturates won't bring the transistor out of saturation.

    When you reach the power limits of the parts you're using - its time to scale them up.
     
  8. wayneh

    Expert

    Sep 9, 2010
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    If you saw sparks, it's almost certain that you melted some insulation off the windings and this led to a short of some number of windings. Visual inspection may reveal this, as might checking DC resistance of both sides. It would have been useful to have the DC resistances when the coils were known good.

    The shorting may have destroyed the transistor, or it is merely overloaded and getting hot.
     
  9. Clark44

    Thread Starter New Member

    Aug 11, 2014
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    Can anyone tell me what should be the primary and secondary gauge margins? I mean if i were to use 30 gauge wire for the primary what gauge of wire i should use for the secondary?
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    30 gauge seems a bit thin for the primary - probably about right for the secondary.
     
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