Basics of Power Supply Circuit

 If you want to build an electronics system that is operated from AC main line power supply then you need to have a power supply circuit. The power supply circuit mainly consist of transformer, a rectifier, a smoothing capacitive filter and voltage regulator. 

A rectifier can be a simple half wave rectifier as shown below.

Or a full wave rectifier as shown below.

Or a bridge rectifier as shown below.

Among these three rectifier, the bridge rectifier has higher DC output voltage and it is more advantageous to use bridge rectifier.

The output of a rectifier is pulsating DC voltage or rippled voltage which can be smoothen using capacitor(s). In power supply circuit these capacitors are called filter capacitor. The output voltage from the filter capacitor is larger than the unfiltered voltage. Below is shown filter capacitor placed after the rectifier.

To improve the power supply, that is to remove the ripples even futher two stage capacitive filter are often used as shown below.

A zener diode is placed after the capacitive filter to output a constant voltage and current and also improve the ripple variation. This is called regulator which is shown below.


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