RECTIFIER

In the last article we studied about a P N junction diode,how it works ,whats it nature in forward and reverse bias condition and one application that is as a switch. Today we learn about an another application that is a diode can act as a "RECTIFIER".

         In this section we observe how a diode act as a rectifier.
RECTIFIER  :   It  is a device which is used to convert AC(continuous variable with time) into a DC(constant with time).

NEED TO CONVERT AC TO DC:

1. We cannot store an AC signal as it is continuously varying with time.But we can store a DC signal like in batteries etc.
2. Our all electronic goods require DC because a continuous change in signal will affect the device.
3. Our renewable energy sources like hydro electric ,wind turbine generate AC so there is a need to convert to DC.

There are 3 types of rectifiers using diode.

• half wave rectifier
• full wave rectifier
• bridge rectifier

1. Half wave rectifier:

In this half wave rectifier only half of the input AC signal into DC signal.

OPERATION:

                      Here when the input AC is in positive state, diode becomes ON and allows for rectification but for negative input of AC diode will be in OFF state so open circuit(no output will be resulted). 

Efficiency is around 40.6%.

Transformer is to allow only AC and reject DC.

output resistance is used to measure the output DC signal.

2. Full wave rectifier:

In the full wave rectifier both positive and negative cycles of input AC is converted in DC.

OPERATION:

                      Here for the positive input cycle, diode D1 becomes ON so the output DC is resulted and for the negative input cycle diode D2 becomes ON so same process continues and DC signal is resulted.

*Hence in the full wave rectifier, input AC signal is completely converted into DC signal.

*Efficiency is around 81.2%(double of half wave rectifier).

3. Bridge rectifier:

                        similar to the full wave rectifier bridge rectifier also converts AC into DC,it is one of the design process using 4 diodes.

OPERATION:

If we name the diodes as D1,D2,D3,D4 respectively in clockwise direction from right top then for positive AC signal D1 & D3 will be in ON condition remaining will be in OFF state where as for negative AC signal D2 & D4 will be ON and remaining will be in OFF state.

*This is how AC signal is completely converted into DC signal.

*Efficiency is also the same.