What is the purpose of these components here?

Discussion in 'General Electronics Chat' started by studenteng, Dec 14, 2010.

  1. studenteng

    Thread Starter New Member

    Dec 14, 2010
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    What is the purpose of the capacitor and the inductor in this basic PWM circuit? Why does the capacitor need be there for the Va to equal Vin when the switch pole is in the up position? Same with the inductor, what does it do in this circuit specifically and why does it have to be there?

    Wouldn't the Va be equal to Vin without the capacitor there?

    [​IMG]
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    I have to say welcome..

    cause what I have to say next is pretty darn stupid.

    Oh well!!.here goes

    Forget asking why the inductor is there and or the capacitor, first ask your self...

    Why did you join this forum?
     
  3. studenteng

    Thread Starter New Member

    Dec 14, 2010
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    No, it's alright, no question is stupid, I'll answer you. It's an engineering forum and it was a good place to ask the question about that circuit.
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Ok then .....good answer.. u have passed.

    Welcome ....

    Why do you ask why it is there?

    Why don't u ask what does that capacitor/inductor combination does?
     
  5. studenteng

    Thread Starter New Member

    Dec 14, 2010
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    Yes, this is a better way to word my question.

    Another question, in the extremes, to add is why do the capacitor and inductor need to be there when the switch's duty cycle can be used to create an average voltage to go to the load.
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    some loads are active. Meaning they have components in them which react to changing voltage. The switch will give you a square wave output. The capacitor and inductor will 'shape' the square wave into pulsing, or rippled DC. They prevent the voltage from going all the way to ground when the switch opens, by sending discharge current thru the load when the switch is open.
     
  7. studenteng

    Thread Starter New Member

    Dec 14, 2010
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    What would happen to the load and it's voltage waveform if the circuit only composed of the load, switch and the input voltage?

    What does that mean?

    What does that mean and why is the voltage not supposed to go all the way to the ground?
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    I don't teach basic electronics. But I will suggest that you learn it.

    Hit the books man!
     
  9. studenteng

    Thread Starter New Member

    Dec 14, 2010
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    Thank you for the previous response, it was useful to get some kind of understanding. I am trying to understand it and research it.
     
  10. dig1

    Member

    Jul 31, 2008
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    i am supposed to be a fresh EE undergrad...so i will try to help dude just to be corrected if wrong and better YET TO ACTUALLY LEARN..so KERMIT, if you see this...ask questions so that we all can learn.... if it's too elementary ask also a directed question maybe where i can go research it specifically....thanks by the way for all ur contribution...
    ur capacitor will help by acting as a consitent voltage source @ the instant of switch flicking from down position to up position... voltage in a capacitor does not change instantly
    the inductor will help by acting as a current source to the load while @ that infinitesimal instance when the switch is moved from down position to up position...the combination, stabilization.... thus will not see spikes at those times there is a switch...if the load was sensitive or contains sensitive components those spikes could damage....
    anybody wanna chime more?(again would love to be corrected also if wrong lol)
     
  11. studenteng

    Thread Starter New Member

    Dec 14, 2010
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    Thank you, that makes perfect sense.
     
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