The Transformer
The transformer receives on the primary winding an AC voltage and delivers on the secondary winding a different AC voltage (a lower one)
This AC output voltage must be according to the DC voltage we want to obtain at the end.
For example: If we want to obtain a final DC voltage of 12 volts, the secondary windings of the transformer must have an AC voltage no less of 9 volts.
The peak value on the secondary winding of the transformer will be Vp = 1.41 x 9 = 12.69 volts.
Even thought this value is very close to the one we wanted to get, it is not recommended because we need to take into account that the voltage drops at different stages (blocks) of the power supply.
In this case, we can choose a transformer with a 12 volts AC secondary winding. With this AC voltage, we can get a peak voltage of: Vp = 12 x 1.41 = 16.92 volts.
Note: Vpeak = Vrms x 1.41
Rectifier
The rectifier transforms the secondary winding AC voltage into a pulsating DC voltage. (look at the picture)
In our case, we use a ½ wave rectifier, then we eliminate the negative part of the wave.
The Filter
The filter, formed by one or more capacitors, flattens or smoothes the previous wave eliminating the alternating current (AC) component delivered by the rectifier.
These capacitors are charged to the maximum voltage value that the rectifier can deliver, and they are discharged when the pulsating signal disappears. Look at the picture above.
The Voltage regulator
The voltage regulator receives the signal from the filter and delivers a constant voltage (let’s say 12 DC volts) regardless of the variations on the load or the voltage supply.
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