convertAC/DCwithout diod

Discussion in 'General Electronics Chat' started by fanoudi, Apr 7, 2012.

  1. fanoudi

    Thread Starter New Member

    Apr 7, 2012
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    hi, I convert AC/DC with out Diod work it , for example convert AC/DC with SCR,transistor or ... plese help me
     
  2. PaulEE

    Member

    Dec 23, 2011
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    A BJT has a diode in it...
     
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    #12 likes this.
  4. Adjuster

    Well-Known Member

    Dec 26, 2010
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    What are you actually asking for? There are other things than diodes which can rectify under certain circumstances, such as synchronously switched MOSFETS, leaving aside that these many also provide rectification due to parasitic diode action if not correctly driven.

    Historically, rectification was sometimes accomplished mechanically by vibrating or rotating switches, the commutators of brushed Dc generators effectively worked in this way.

    Early battery charging equipment sometimes used electrolytic rectifiers, inefficient and hazardous devices which may not have been referred to as diodes.

    Note however othat the thermionic valve (or vacuum tube) rectifier is in fact the earliest rectifying diode of all, after which semiconductor diodes were named by analogy. Gas filled rectifier tubes may not be called diodes so often, and certainly the polyphase mercury kind are (or were) more complex beasts.
     
  5. jimkeith

    Active Member

    Oct 26, 2011
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    How about a high voltage spark-gap rectifier? --used in old geiger counters.
     
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Google doesn't get me anywhere. Got a link?

    Ken
     
  7. debe

    Well-Known Member

    Sep 21, 2010
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    I dont know how it was done, but I wrecked a large 240V ac to 48V dc battery charger that used SCRs as the rectifiers. It put out 48V dc @ about 200Amps. It came out of an old telephone exchange.
     
  8. jimkeith

    Active Member

    Oct 26, 2011
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    Hi Ken, This I recall from reading Popular Electronics in the '50s --well before the days of google, so it is possible that this technology has fallen through the crack.

    How it works--a breaker point inductive discharge generates a specific polarity at the coil output--connecting this point to a capacitor through a spark gap causes a high voltage charge to be stored in the capacitor. I can see that this could be tempermental if the plasma decay is not sufficiently fast when the voltage across the gap is reversed--similar issue to recovery time in microwave duplexer discharge tubes

    Another rectifier technique not mentioned is the use of electrolytic capacitors--yes they do rectify, but have substantial recovered charge--they were used in the early days of radio, but obviously not widely as there is little doubt that their lifetime was severely limited
     
  9. jimkeith

    Active Member

    Oct 26, 2011
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    Hi Daryl, Did this use high (hundreds of hZ) or low frequency magnetics?