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Rectifiers, Voltage Regulation and Smoothing Circuits

Discussion in 'Videos and Podcasts' started by VU2JO, Oct 28, 2024 at 6:19 AM.

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  1. VU2JO

    VU2JO Ham Member QRZ Page

    Unlike direct current, alternating current reverses direction of flow periodically. Rectifier is a device which converts alternating current to direct current. It does this by cutting off one of the half cycles of an alternating current so that it becomes a pulsating direct current, flowing only in one direction. In the earlier era, vacuum tube diodes were used as rectifiers. Now there are semiconductor diodes which are commonly used in hobby electronics. Other types of rectifier devices are mercury arc valves, stacks of copper and selenium oxide plates and silicon controlled rectifiers. Rectified output needs smoothing out of ripples using high value capacitors and inductors. Voltage regulation is done by devices like zener diodes, to provide a stable output in the face of potentially fluctuating loads as in amateur radio transceivers. Transceivers need high current during transmit mode and only very low current during reception of radio signals.

     
  2. WB9YZU

    WB9YZU Ham Member QRZ Page

    Nice video!
    I would hope that most hams have a handle on these simple concepts as they are in the Amateur Radio Handbook :D
    One one of my screening tests for potential employees for a Tech position was to have them draw me the schematic of a basic linear power supply using a transformer, 4 diodes, and a capacitor.
    It was amazing to see how so many supposed ""Electronics School"" grads could not draw that circuit from memory.

    We call the "smoothing stages", Filters, because they filter out the remaining AC component.

    Zener Diodes are the semi conductor equivalent of a neon bulb or other discharge tube. They are parasitic devices, and do not regulate well on their own. They are however very useful as a reference voltage source for a linear pass supply.

    For the sake of discussion, one can not regulate a DC voltage near the supply voltage. How much headroom you give depends on how much current you expect to draw from the regulated supply.
    P=IE in is equal (minus heat losses) to P=IE out. So if you have 50V @ 1amp available, you can theoretically pull 12V @ 4.15 amps from the regulator output. This allows you to use a transformer that supplies less current than you require, and reduces the size of the transformer.
     
    VU2JO likes this.
  3. VU2JO

    VU2JO Ham Member QRZ Page

    Thanks a lot Ron for the valuable points. Hope to meet you on air someday. 73
     

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