Have been designing without specification of a rectifier circuit. Can someone explain from transformer, bridge rectifier and capacitor stage how to get a specified voltage at the output? The paper design first and what to expect at the output stage when measured with multimeter.

 

You put a voltage regulator on the filtered output of the bridge rectifier.

 

I'm not talking of the regulator

 

How to get a specified voltage at the output given a transformer of a specific voltage

 

Usually the voltage across the smoothing capacitor is the voltage from the transformer less 1.4V (bridge rectifier) , multipied by 1.414, this is an approx value.

 

Hello Exjay,
The answer to your question is "it depends".
If you have a transformer with a 12v.AC rms voltage, if your capacitor stage is perfectly sized amd you are drawing current, the DC voltage would be 12v as well. However, as Dodgydave says you will actually see more like this voltage times 1.414 (root 2) as this is the peek ac voltage. When no current is being drawn, the capacitor draws peek current at peek voltage, and hence gets very close to peek voltage.

 

What is the nature of the circuit you are using?
In some cases a capacitor is not required.
Max.

 

A transformer without a load produces a voltage higher than its loaded rating. A 12V transformer might produce 14V. Then its peak is 14V x 1.414= 19.8V and the bridge rectifier reduces the filtered DC output to 18.4V.

When the bridge rectifier is loaded heavily then its voltage drop is 2V.

 

These might be of use -

http://mcitransformer.com/about-mci/power-supply-design-notes/

https://www.st.com/content/ccc/reso...df/jcr:content/translations/en.CD00003794.pdf

Regards, Dana.

 

and this:

http://www.hammondmfg.com/pdf/5c007.pdf