Smoothing with full wave rectification

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Discussion Overview

The discussion revolves around the feasibility of producing a smooth voltage output through full wave rectification, particularly in the context of powering an x-ray tube. Participants explore methods to convert AC to DC and smooth the resulting voltage, addressing the differences in capacitor requirements between half-wave and full-wave rectification.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant questions the ability to achieve a smooth voltage with full wave rectification and compares it to half-wave rectification, which typically uses a capacitor.
  • Another participant asserts that full wave rectification can indeed produce a smooth voltage and suggests that the ripple frequency is higher, indicating a need for different capacitor values for optimal performance.
  • A different viewpoint suggests that a smaller capacitor can suffice for full wave rectification, emphasizing the engineering principle of achieving functionality with minimal resources.
  • A participant shares a diagram intended to demonstrate a circuit that achieves smooth voltage across a resistor, although they note it hasn't been thoroughly tested in simulation software.
  • A participant clarifies their goal of converting AC to DC for an x-ray tube, seeking to ensure the peak voltage aligns with the average voltage for effective operation.
  • Another participant provides a formula for calculating the required capacitance for smoothing the output voltage, indicating that larger capacitance reduces ripple voltage and enhances smoothness.
  • The suggestion of using a voltage regulator is made to maintain a constant DC voltage and further reduce ripple effects.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of capacitor size for effective smoothing in full wave rectification, indicating that multiple competing perspectives remain without a clear consensus.

Contextual Notes

The discussion includes assumptions about circuit design and the effectiveness of different components, but these assumptions are not universally agreed upon. The specific conditions under which the proposed solutions would work effectively are not fully explored.

Who May Find This Useful

Individuals interested in power supply design, particularly in applications involving x-ray tubes or similar technologies, may find the insights and discussions relevant.

IntuitioN
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Hi all!

Is it possible to produce a smooth(or almost smooth) voltage through full wave rectification? I know for half-wave, you can use a capacitor, but this doesn't seem to work for full wave.

Cheers
 
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Sure it does. You may need to provide more information about what you are doing. IIRC, since a full wave rectifier has twice the ripple frequency of a half wave rectifier you will need to use a different valued cap for optimal performance.
 
You don't need to use a different cap, but you can get by with a smaller one. That is what engineering is all about though, getting by with as little as possible and still having things work correctly.
 
I think the diagram that I have attached achieves that, I did not test it properly in pspice though. The DC source represents your full wave rectification and the voltage across R1 should be smoothe enough
 

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hi guys thanks for ur replies!

What i am trying to do is to produce a smooth voltage to power an xray tube. I am trying to convert the AC currect into a DC current then smooth the voltage out so that the peak voltage is effectively the average voltage.

Exequor: What is L1? I'm not very good at this so can you please explain a bit how your circuit works?

Cheers
 
Last edited:
Go to my website www.abiscus.com and go to the rectified power supply link. On that page you'll find a PDF file explaining the theory behind rectification.

For a fullwave rectifier, the equation for the capacitor C is:

C = Vp / ( 2 * R * f * Vr )

where Vr is the voltage ripple, f is the frequency, R is the load resistance, and Vp is the peak voltage of the input.

As you can see, the larger the capacitance, the smaller the ripple voltage and the closer you will come to a smooth DC value.

You may also want to think about using a voltage regulator. This helps keep the DC voltage constant and further dampens the ripple.
 

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