help understanding circuit

Discussion in 'General Electronics Chat' started by mat350z1, Dec 4, 2014.

  1. mat350z1

    Thread Starter New Member

    Dec 4, 2014
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    Hello everyone.
    Im a noob and i want to learn
    I want to build my own efficient fly back driver
    I do have a decent understanding of electronic circuits. But i need help with this one. I want to design and build my own zero volt switching driver for a fly back i have. It has an exposed ferrite core that i can manage to wrap seven turns of 14 gauge wire around. My question is how do i calculate the the current draw of the primary side of the transformer at a frequency of around 30khz? at 12 volts. can i use standard inductor calculations or does the core of the transformer or the secondary side of the transformer have an impact on these calculations. What are the effects on the circuit when the transformer is running in its resonant frequency. Afterwords how do i figure out what the best FETs are to use. I have looked at a number of examples of the ZVS circuits, but i do not understand why certain components are placed, where they are in the circuit. I have an example attached.

    In the picture i don't understand to purpose of the inductor feeding the primary side of the transformer. Nor do i understand the purpose of the capacitor across the primary. Is it for frequency limitation? And what purpose do the two 400 volt diodes serve?

    Thanks. sorry for so many questions. i just want to learn all this.
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Huh?
    Noobs want to flash LEDs and charge batteries. Why do you want a flyback driver?
     
  3. mat350z1

    Thread Starter New Member

    Dec 4, 2014
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    okay well i would like to attempt to make my own plasma speaker. haha
     
  4. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Cool... but why don't you just buy a ready-to-assemble kit like this one?
     
  5. mat350z1

    Thread Starter New Member

    Dec 4, 2014
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    Simply because that takes the fun out of it, i want to build one of my own design.
     
    cmartinez likes this.
  6. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Then you're in the right place... though I myself won't be able to teach you much... this is borderline outside my area of expertise. But I'm willing to participate anyway I can...
     
  7. ScottWang

    Moderator

    Aug 23, 2012
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    I'm not sure how long the higher voltage as 35V or 40V will keeping in the input, if Vin=40V, how is the watts of current limiting resistor:
    Vin=40V-12V=28V
    I_470=28V/470Ω=59.6mA.
    W_470=28V*59.6mA=1.67W
    If using the least rating of power dissipation as 3 time, then the w=1.67W*3=5W.
    To me I might using 5 times to do the calculation.
     
  8. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    So... this thing is supposed to generate a spark (electric arch) depending on the audio signal being fed to it?
     
  9. mat350z1

    Thread Starter New Member

    Dec 4, 2014
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    Thanks cmartinez. I appreciate that. And not quite this is only suppose to drive the fly back transformer to generate the high voltage spark
    Scott. As far as i understand that 470 ohm resistor only goes to the gate of the mosfet which are turned on by a minuscule amount of power. so i dont think that the 2 watt resistor is underrated even at 40 volts, i could be wrong though.
     
  10. cmartinez

    AAC Fanatic!

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    I've already looked up some other circuits for what you want to accomplish... The one that has drawn my attention the most is this one, since it seems that it can be calibrated depending on your original signal strength.
     
  11. wayneh

    Expert

    Sep 9, 2010
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    I've seen plasma speaker demonstrations often at college engineering open houses. Science fair type stuff. There should be a lot of info out there but I haven't looked.

    Like you, I don't fully follow the circuit you posted.
     
  12. ScottWang

    Moderator

    Aug 23, 2012
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    I just according to the voltages to calculates the power dissipation, no matter the resistor where to located on, when you completed the circuit then you can using your finger to feel it or using thermometer.
     
  13. mat350z1

    Thread Starter New Member

    Dec 4, 2014
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    Thanks Scott you are right
    And thanks for the help cmartinez.
    so no one really knows whats going on in the circuit i posted.? okay i guess im going to do some more digging.
     
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