Full Wave Rectifier Circuit, Characteristics, Advantages & Disadvantages

In this chapter, we are going to learn about second type of rectifier that is full wave rectifier. Unlike half wave, full wave rectifier is mostly used.

We have already discussed rectifier and half wave rectifier in our previous tutorials. From them, we got to know that there is a vast difference between the characteristics and efficiency of different rectifiers. Now we will learn the types and characteristics of full wave rectifier.

Full Wave Rectifier

Full wave rectifier can be defined as “a type of rectifier that converts the alternating voltage into pulsating direct voltage but unlike half wave rectifier, it uses both cycles of the input voltage. For this AC to DC conversion, it uses 2 diodes.”

This rectifier acts a heart of circuitry which allows the sensors to attach to the RCX in either polarity.

Full wave rectifier image

In this rectifier, full wave rectification is achieved by using two crystal diodes which conduct current alternatively. During positive as well as the negative half cycle of input AC, the two circuits are employed to obtain the same direction of current flow in the load resistor.

Full Wave Rectifier Circuits

This rectifier is further classified into 2 types namely: Center Tap Full-wave Rectifier and Full wave Bridge Rectifier. Each of these has its own working operation and features. Now we are going to understand these circuits in detail.

Center Tap Full-wave Rectifier

This rectifier is widely used in the vacuum tubes and thermionic valves. It employs a tapped transformer with secondary winding AB tapped at the center point C, two diodes D1  and D2 are connected in the upper half and the lower half portion of the circuit.

For rectification, the Diode D1 utilizes the AC voltage appearing across the upper half of the secondary winding while D2 uses the lower half of secondary winding.

Learn More  Transistor as an amplifier: Common emitter amplifier circuit

Center Tapped Rectifier Working Operation

The circuit diagram of full wave rectifier circuit with waveform is shown in the below figure. The alternating voltage Vin appears across the terminals AB of the secondary winding of the transformer when AC supply is switched on.

Full wave rectifier circuit image

During positive half cycle at a given voltage, end A of the transformer become positive while end B become negative which makes the D1 diode forward biased and the D2 diode reverse biased. Due to this reason, the diode  D1 conducts current while D2 does not conduct current.

As shown in the above figure, the current starts flowing through diode D1, and output voltage Vout is measured across load resistor RL. This means current flows only in the upper portion of the secondary winding of the transformer. The path of the current is shown by bold arrows.

During Negative Half Cycle, the end B of the transformer becomes positive while the end A becomes negative. This makes the D1 diode reverse biased and the D2 diode forward biased. Due to this reason, now the diode  D1 does not conduct current while D2 conducts.

As shown in the figure above, the current starts flowing through diode D2, and through load resistor RL in the lower portion of the secondary by dotted arrows.

Note: During Negative as well as positive half-cycle of the input AC voltage, the current flows through the load resistor RL in the same direction.

Therefore across the load resistor RL,  DC output voltage Vout is obtained.

The waveform diagrams of the current flowing through the load, applied input voltage and output voltage developed across the load are shown in the above figure.

Full-wave Bridge Rectifier

bridge rectifier cicuit

Bridge Rectifier is another type of full wave rectifier, that uses 4 diodes instead of 2. It also does not require any center tapping. As the name suggests, it is a bridge rectifier, so we can conclude that it uses a bridge circuit.

These 4 individual rectifying diodes are connected in a closed-loop bridge configuration. Having no requirement of a special center-tapped transformer makes it smaller in size & cheaper at cost.

Bridge Rectifier Working Operation

As shown in the figure above, the bridge rectifier has 4 diodes; namely D1, D2, D3, D4.  Out of these 4 diodes of the bridge, only two diodes conduct at a time. Either “D1  and D3” conducts or “D2 and D4” conducts or vice-versa depending upon the positive or negative half cycle fed to the bridge circuit.

Learn More  Schottky Diode working, construction, characteristics and Applications

Now, let us understand this taking both cases:

Positive Half Cycle:

When the positive half cycle is fed to the bridge circuit, Diodes “D2 and D4” are positively biased. While Diode “D1  and D3” are negatively biased. This means only “D2 and D4” will conduct.

The direction of the current is shown in the above figure.

Negative Half Cycle:

When the negative half cycle is fed to the bridge circuit, Diodes “D1  and D3” are positively biased. While Diode “D2 and D4” are negatively biased. This means only “D1  and D3” will conduct.

The direction of the current is shown in the above figure.

Here most important point to note is, the direction of current flow is same in both cases. This means, the current is unidirectional and so the voltage-drop is also unidirectional.

You can also watch video on Full Wave Rectifier by Neso Academy

 

Full wave Rectifier Characteristics

For the analysis of Full wave rectifier following parameters value or properties are considered. Following of its characteristics are:

Ripple Factor

Ripple factor is defined as the ratio of the RMS value of the AC component to the DC component. Therefore,

Ripple factor = RMS value of AC component / value of DC component

This factor mainly decides the effectiveness of a rectifier i.e. smaller the value of this factor, lesser is the AC component in comparison to the DC component. Hence, more effective is the rectifier.

Ripple Factor Calculation Equation

The Ripple Factor of Full wave rectifier can be calculated as follows:

As we know,

Irms = √ Idc2 + Iac2

Where,

Irms = RMS value of total load current

Idc = value of dc component of the load current

Iac = RMS value of the AC component of load current

Therefore,

Iac = √ Irms2 – Idc2

As we know,

Ripple factor = Iac / Idc

                                    = √ Irms2 – Idc2 / Idc

                        = √ (Irms / Idc)2 -1

Learn More  Transistor as an Oscillator: Guide

For full wave rectifier, ripple factor is calculated as:

As we know,

Irms / Idc = ( Im / √ 2)  / (2 Im /π) = 1.11

Therefore,

Ripple factor = √ (1.11)2 -1 = 0.482

Efficiency Calculation

The efficiency of rectifier is defined as the ratio of DC power output to the input AC power. Therefore,

Efficiency = DC power output / AC power input

                                                                               = 0.812 RL /  (rf + RL)

If rf  is  neglected as compared to RL, the efficiency of the rectifier is maximum given as;

ηmax = 0.812 = 81.2%

Hence the efficiency of full wave rectifier is 81.2%. Or we can say that Full wave rectifier is 81.2% efficient.

Peak Inverse Voltage (PIV)

Peak inverse voltage is defined as the maximum value of the voltage coming out of the diode when it is reverse biased during the negative half cycle. For center tap full wave rectifier its value is 2Vand for the bridge rectifier, its value is Vm.

Transformer Utilization Factor (TUF):

It is defined as the ratio of power delivered to load and VA rating of the transformer. For center tap full wave rectifier its value is 0.573 and for the bridge rectifier, its value is 0.812.

Advantages and Disadvantages

Advantages:

Advantages of full wave rectifier are:

  • The output and efficiency of center tap full wave rectifier are high because AC supply delivers power during both the halves.
  • For the same secondary voltage bridge rectifier has double output.

Disadvantages:

Following of disadvantages of full wave rectifier are:

  • Full wave rectifier requires more diodes i.e two for center tap rectifier and four for bridge rectifier.
  • When a small voltage is required to be rectified the full wave rectifier circuit is not suitable.
  • In center tap full wave rectifier, center on the secondary winding for tapping is difficult.

Hope you all like this article. For any suggestions please comment below. We always appreciate your suggestions.

About Ajay Kumar

Hi readers, Ajay Kumar is graduated in Electronics and Communication Engineering is responsible for running this website. With the knowledge, he has gained, he tries to provide the readers as much of it as I can.

14 thoughts on “Full Wave Rectifier Circuit, Characteristics, Advantages & Disadvantages”

    • Thanks Prachi,
      We are glad that it is helpful to you. Like our page on fb and share with your friends. And if you have any doubt about the topic, ask in the comment section. 🙂

      Reply
    • Hi Brian,
      Thanks for commenting. It keeps us motivated. In the coming weeks, we are going to share some projects based on different festival presents and decoration. Make sure to read them and drop your valuable comments.

      Reply

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Previous

Half Wave Rectifier Efficiency Equation and Applications

Gallium Oxide: Semiconductor material with improved Heat conductivity

Next