Half wave rectifier question

Discussion in 'General Electronics Chat' started by coinmaster, Mar 16, 2016.

  1. coinmaster

    Thread Starter Member

    Dec 24, 2015
    350
    6
    So I have a transformer winding that is 15vac and I'm trying to get 20vdc out of it using a half wave rectifier but it is acting weird.
    Screenshot_37.png
    V1 signifies the transformer winding.
    I'm getting 0v at the junction between D1 and C1 and I'm getting -20v at the junction between V1 and D1. If I reverse the diode then I get +20v at the junction between V1 and D1. Why am I getting DC at the input and not at the output?
     
  2. mcasale

    Member

    Jul 18, 2011
    210
    12
    First thing is to add a load resistor across C1, because you are charging C1 to the peak value of V1 (15*1.414 = 21.2v). The simulator likes at least a small load.

    If you are measuring at the + side of V1, you should see V1 - only AC - no DC. Are you using an oscilloscope or a multimeter?
     
  3. coinmaster

    Thread Starter Member

    Dec 24, 2015
    350
    6
    Well the simulator works fine. It's real life that is acting weird. V1 is just representing my transformer.
    Multimeter.
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,050
    3,244
    Sounds like something in your circuit is wired incorrectly.
    What type of transformer is it?
    The real circuit should basically act the same as the simulator shows.
     
  5. coinmaster

    Thread Starter Member

    Dec 24, 2015
    350
    6
    It's a toroidal transformer I pulled from a tube amp.
    I'm using a 15v output wire and connecting the diode and capacitor to it as shown in the simulator, actually the wire is 30vAC because it is connected in series but the winding itself is being rectified.
    It's reading 21v AC and -20v DC on the winding and 0v at the diode-capacitor junction.
    [​IMG]
    EDIT: Actually I just noticed the 15v wire is connected in series to the other toroidal so it is 30vAC by default, not 15v.
     
    Last edited: Mar 16, 2016
  6. crutschow

    Expert

    Mar 14, 2008
    13,050
    3,244
    I don't understand what you mean by "the winding itself is being rectified"? :confused:
    If that a separate rectifier from the external rectifier, then that would explain your results.
     
  7. coinmaster

    Thread Starter Member

    Dec 24, 2015
    350
    6
    As in the transformer coil itself is being rectified to DC. But I just solved it, there was some outputs on the transformer that needed to be connected to ground. Thanks for the help :)
     
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