Why Center Tapped Transformers Don't Need a Bridge (4 Diode) Rectifier

Discussion in 'Shock Brother's DIY Amps' started by robrob, Oct 19, 2014.

  1. robrob

    robrob Poster Extraordinaire Ad Free Member

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    This bothered me for a long time until I did enough research to understand the current flow through 2 and 4 diode rectifiers.

    Why does a power transformer with a center tap allow rectification with just two diodes versus four needed with no center tap?

    Because the center tap provides the path for returning current. If you use a transformer without a center tap then a 4 diode bridge rectifier is needed to provide a current return path from the amp circuit back to the transformer.

    Bridge Rectifier Current Flow During Top Half of AC Wave
    [​IMG]
    All four diodes act as one-way valves that allow current to only flow one direction. The two diodes on the left side are the 'bridge' back to the transformer. They provide a return path for the current from the amp (circuit load) to the transformer.

    Bridge Rectifier Current Flow During Bottom Half of AC Wave
    [​IMG]


    With a Center Tap Two Diodes are Enough
    [​IMG]
    Conventional rectifier showing current flow during the top half of the AC wave. The power transformer's center tap provides the current return path from the amp circuit.


    [​IMG]
    A tube rectifier works the same way as this two diode rectifier, that's why tube rectifiers are always paired with power transformers with center taps--the center taps are required to provide a current return path from the amp circuit back to the transformer.

    Conventional Rectifier and No Center Tap
    [​IMG]
    With no center tap there's no return path to the transformer so this will not work.
     
    Last edited: Oct 20, 2014
  2. andyfromdenver

    andyfromdenver Friend of Leo's

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    Cool!
     
  3. Telenut62

    Telenut62 Poster Extraordinaire

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  4. printer2

    printer2 Poster Extraordinaire

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    All you had to do was ask.
     
  5. robrob

    robrob Poster Extraordinaire Ad Free Member

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  6. robrob

    robrob Poster Extraordinaire Ad Free Member

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    This is a pretty cool little youtube animation:

     
  7. Amazed

    Amazed Tele-Meister

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    Thanks Rob.
     
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