Uses of Rectifier

A rectifier is an electrical device that converts AC to the DC current. A mobile can only be charged expeditiously if a constant, consecutive voltage supply is being provided to it. When the charger is connected to the mainline, the AC input supplied to it is 220 V, and this supply when passed through the charger, we achieve the output of 5V DC. This is possible by using a rectifier in the circuit of the charger.

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Here the voltage drop occurs by the transformer, and the conversion of AC to DC occurs by the device known as a rectifier.

Introduction

Rectifiers are used in not just a single device but have a variety of uses in various devices. This is used to modify the network systems. They are categorized based on the factors such as type, bridge configuration, and the components that are used in it. The rectifiers use the P-N junction type of diodes that help in converting the alternating current to direct current. To understand the Uses of Rectifier - Types and Their Uses and Functions, all the important information is provided via Vedantu that helps the students understand the concepts while also explaining how to apply them in real-life situations.

On this page, we&#;ll learn about the following:

• Application of rectifier

• Full-wave rectifier applications

• Rectifiers are used to convert

• Uses of the half-wave rectifier

• Uses of full-wave rectifier

• What is a rectifier?

• Types of rectifier

• Rectifier function

• Full-wave bridge rectifier

Rectifier Function

A rectifier uses a P-N junction diode to convert AC to pulsating DC. This P-N junction diode allows the flow of an electric current in a forward-biased condition and blocks the electric current in a reverse-biased condition. In simple words, a P-N junction diode allows a unidirectional flow of current. This unique attribute of the diode allows it to act like a Rectifier. The below fig shows an output waveform for the basic rectifier.

Types of Rectifier

Half-wave Rectifier: In such a rectifier, the input voltage is described by a sinusoidal wave for a positive half-cycle.

Full-Wave Rectifier

1. Full-wave centre-tapped rectifier

2. Full-wave bridge rectifier 

Half-Wave Rectifier

A type of electrical device that converts an AC voltage into DC voltage. Such a rectifier allows only one half-cycle of an AC voltage waveform by clipping the other half-cycle. These devices require only a single diode to construct. The advantage of the fact of using a diode is that it allows the unidirectional flow of current.

Fig.1 shows the functioning of the half-wave rectifiers, putting an AC waveform with positive and negative cycles as input power and after rectification, we obtain the DC output power with no negative cycle.

Rectifier efficiency is given by,

η =  Pdc / Pac

Where ηmax   = 40.6 % (low)

Rectifier efficiency η is defined as the ratio of DC power (Pdc) to the applied input AC  power (Pac) where ηmax has a very low value.

Uses of a Half-wave Rectifier

There are various uses of a half-wave rectifier, some of which are stated below.

Used in

• Low power simple battery charger circuit.

• Pulse Generator Circuits.

• Signal demodulation circuits.

• Firing circuits.

• Soldering Iron circuit. 

• Amplitude Modulation (AM) Radio circuits as a Detector.

Full-Wave Rectifier

A Full wave Rectifier is a circuit that changes an alternating current voltage into a pulsating dc voltage using both half cycles of the applied ac voltage supply.

It utilizes two diodes of which one conducts during one-half cycle while the other diode remains off and conducts during the other half cycle of the applied ac voltage. Hence in such a device, We obtain the positive and negative output cycle however one diode stops the current flow the other diode conducts and allows the current.

In this device, for both the input AC signals either positive or negative, the output DC is generated.

Full-Wave Bridge Rectifier

A Full wave bridge rectifier is a circuit organization that makes use of both half cycles of input AC and converts them to DC. There are 4 diodes (D1, D2, D3, D4) arranged as a bridge. Therefore, this arrangement is known as a Bridge Rectifier

The Positive Half-cycle

During the positive half-cycle, diodes D2 and D4  are forward-biased starts conducting diodes D1 and D3 are reverse-biased as an open circuit. Thus, current (i) flows through the load resistor RL.

The Negative Half-cycle

During the negative half-cycle, the diodes D3 and D4 are forward biased while D1 and D2 remain switched off. The current flow through the load is in the direction as before.

Applications of a Full-wave Bridge Rectifier

Full Wave Bridge Rectifiers are mostly used for the low cost of diodes because of being lightweight and highly efficient.

The important uses of the full-wave bridge rectifier are given below.

• Mobile phones, laptops, charger circuits.

• Uninterruptible Power Supply (UPS) circuits to convert AC to DC.

• Our home inverters convert AC to DC.

• LCD, LED TVs.

• Car Alternator to charge the batteries during the running of the car.

•  LED Driver Circuits

•  Audio Amplifier

•  Radios

The Need for Rectifiers

There are two types of voltages that are observed widely and are classified into either alternating voltage or direct voltage. These voltages can easily be interconverted based on the circuit that has been used. For example, the main supply for homes needs only a small amount of DC voltage while the main grid only provides alternating voltage. Due to this, it is needed to convert the AC into DC which can be easily done with the help of rectifiers being used in the circuit.

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It can also be perceived in another way where there is the interconversion of current taking place with the help of a rectifier. The alternating current is being converted to direct current which most of the appliances in a home will require. It is also seen that these rectifiers take in both the positive and negative components of the current and convert it to one with only positive components.

A basic diode has various applications it includes rectifiers in it as well. Rectification can be done through the basic diode. It may be current or voltage the AC values will be converted into DC. The basic property of the diode is that it can establish the path for the flow of current in one direction that is possible during forwarding bias. However, during reverse bias, the diode remains in non-conducting mode. It doesn&#;t participate for the establishment of the path for the flow of current. Hence this made the diode to utilize it for rectification. This article covers the basics of Rectifier, its working theory, functioning, circuit diagram, equations and furthermore its applicstions.

What is Rectifier?

Definition:  A normal diode with its junction formed due to p-type and n-type interaction is utilized for the purpose of conversion of alternating currents into direct currents. This process is referred to as rectification and the respective circuitry designed for rectification is defined as a rectifier.

As the property of diode suggests, whether a diode with the junction as p-n can operate in forwarding bias or block the flow during reverse bias.

The diode in forwarding bias is in conducting mode because the p-type is connected to the positive part of the supply and the n-type is connected to the negative part of the supply. There is the movement of electrons from the n-side towards the p-side and the holes movement can be evident from the p-side towards the n-side.

As these are the majority charge carriers from both sides. Their movement makes to generate the current that is referred to as forwarding current.

If the diodes p-type is connected to the negative part of the supply and n-type is connected to the positive part of the supply. This type of connection makes the diode to be in reverse bias.

Hence the majority of the charge carriers get attracted towards the respective terminals of the battery. Then the existence of minority carriers makes the presence and the reverse saturation current flows in the circuit.

But the reverse current in the diode is because of the influence of minority charge carriers. So that it can be neglected. Hence these conditions are utilized and make the diode as the part of the application.

These are the basic biasing techniques that make a part of the rectifier theory.

Functioning

Biasing basically done by using the supply in terms of DC but as per the consideration of rectifier, the terms must be realized by considering AC as the supply. As the representation of AC and DC is already known, AC in terms of sinusoidal wave and the DC representation is done with a straight line.
The upper part of the wave denotes the positive side of the supply and the lower part denotes the negative side of the supply. Positive half is the representation of the forward bias voltage of DC and the negative half representation will be of the reverse bias voltage of DC.

The waveform of AC is not constant it is a variant of time. As it reaches the positive peak value it tends to degrade the same will be followed for the negative value after reaching zero again it will come back to zero lines.

Now let us begin the working of rectifier by applying AC as the input. For the positive half of the cycle, the diode acts in forward bias mode. Hence the path is established for the movement of charge carriers.

Once the negative part of the cycle is applied to the diode it blocks the value of the current because the movement of minority charge carriers in it can be neglected. Simply one can define the working of the diode as conducting in forward bias and blocking in reverse bias to the flow of current.

Hence the flow of current is evident during the positive part of the cycle applied to the diode. The output obtained it must be converted from AC into DC. In this way the basic diode functions as a rectifier.

General Representation of Power Supply

But these rectifiers generally don&#;t produce any pure form of DC. It consists of an impure form of AC components in the obtained output. Hence these AC components are referred to as ripples. These ripples can be removed by using a filter connected across the rectified output in order to obtain the smoothening effect. It is said to be maximum efficient if its ripple factor value is at a minimum.

Rectifier Circuits

Basically, the rectifier circuits can be classified as

• Half Wave Rectifiers
• Full Wave Rectifiers

Rectifier Circuit of Half Wave

A half-wave rectifier is a basic circuitry with a single diode used in it. This connected to a series AC supply as well as a series load resistor. It follows the property of the diode by conducting to the positive cycle. This consideration makes this circuitry a simple one to analyze.

Rectifier Equations of Half Wave Rectifier

The average value of voltage,

Vavg= Vm/π

The average value of the current can be given as

Iavg=Im/π

The value of RMS voltage can be given as

Vrms=Vm/2

The value of RMS current can be given as

Irms=Im/2

The ripple factor value of half-wave rectifier is

Ripple Factor=1.21

The efficiency value of the rectifier is given as

maximum efficiency=40.6%

The form factor value is

form factor=1.57

The above are some of the rectifier equations that relate to the half-wave rectifier.

Rectifier Circuit of Full Wave

A full-wave rectifier can be classified as a center-tapped and bridge rectifier circuits. It is more efficient compared to that of half-wave. It can utilize both the cycles so that the loss in power is minimum.

Centre Tapped Full Wave Rectifier Circuit

It consists of a center-tapped transformer with two diodes connected with a resistive load. The positive point of it is that one diode responds during one part of the cycle and the other during another part of the cycle. In this way, there is no loss of the output power.

Centre Tapped Rectifier Circuit

The drawback for this kind of rectifier is that the usage of the center-tapped transformer makes it costly. Hence another circuit referred to as bridge rectifier has been designed.

Bridge Rectifier Circuit

A rectifier with four diodes connected in such a way that it follows bridge topology referred to a bridge rectifier. It has been drawn to overcome the drawback of the center-tapped rectifier.

Diodes D1 and D2 acts for one part of the cycle and D2 and D3 responds to the other part of the cycle so that it can utilize both the halves of the cycles and makes the circuit less costly by using a normal transformer.

Rectifier Equations for Full Wave

The average value of the voltage can be given as

Vavg=(2Vm)/π

The average value of the current can be given as

Iavg=(2Im)/π

The RMS value of the voltage is given as

Vrms=Vm/&#;2

The RMS value of the current is given as

Irms=Im/&#;2

The maximum efficiency of the full-wave rectifier can be given as

E=81.2%

The form factor value is

form factor=1.11

The above are some of the equations of the full-wave rectifier. Furthermore, Rectifier Equations are

1) Average Value

The instantaneous value for the signal considered its average for the arithmetic is referred to as the average value of the given rectifier.

Avg.value=(area present under the curve)/( complete value of the base )

2) RMS Value for the Rectifier

It can be referred to as the square root of the respective means.

RMS value of the given signal=&#;((area present under the respective curve squared)/( length of the base) )

The heat produced by the AC signal RMS value is the same as that of the flowing DC current of the equal value through similar resistance.

3) Peak Factor of the Rectifier

The ratio between the maximum peak value for the applied signal to the RMS value of the respective signal is referred to as the peak factor.

Peak factor=(max.peak value)/(RMS value )

4) Form Factor of the Rectifier

The ratio of the RMS value of the applied signal to its average value is referred to like the form factor.

Form factor=(RMS value of the input signal)/( average value of that signal )

5) Ripple Factor

It can be defined as the ratio of the AC component&#;s RMS value to the DC component present at the output.

γ=VAC/VDC

The final equation for the ripple factor is

γ=&#;((VRMS/VDDC )^2&#; 1)

6) Efficiency of the Rectifier

The ratio between the generated DC output power to the applied input power gives the efficiency of the respective rectifier.

E=PDC/PAC

Advantages

The basic advantage of the rectifier is that it can convert alternating current into direct current.

Applications

• Because of its property of rectification, it can be utilized as a part of the power supply circuitry.
• It can be utilized in power supply units with switching-mode technique.
• During the detection of the amplitude for the modulated radio signals rectifiers are used.
• In order to supply the voltage in a polarized manner for the purpose of wielding rectifiers are used.

Hence the overview for the basic rectifiers is given. It can be the useful part for the application of the power supply unit but it can&#;t be used in practical applications without applying it to a filter Now can you tell are the rectifiers useful in ADC conversions or any further way is there to convert it?

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