Uses of Rectifier

What is a Rectifier?

A rectifier is an electrical device that converts AC to the DC current. A mobile phone 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 phone charger.


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


On this page, we’ll learn about the following:

  • Application of rectifier

  • Full-wave rectifier applications

  • Rectifiers are used to convert

  • Uses of half wave rectifier

  • Uses of full wave rectifier

  • What is a rectifier?

  • Types of rectifier

  • Rectifier function

  • Full-wave bridge rectifier

Rectifier

A rectifier is an electrical device consisting of one or more diodes that allow the unidirectional flow of current. It basically converts AC (that periodically reverses the direction of current) into DC. Rectifiers can be forged in several shapes as per requirement like semiconductor diodes, SCRs (silicon controlled rectifiers), vacuum tube diodes, mercury-arc valves, etc.

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. A below fig shows an output waveform for the basic rectifier.

Types of Rectifier

Half-wave Rectifier

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

Full-wave Rectifier

  1. Full-wave center-tapped rectifier

  2. Full-wave bridge rectifier   

Half-wave Rectifier

A type of electrical device that converts an AC voltage into the 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.


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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

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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

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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


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


The Negative Half-cycle


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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 


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FAQ (Frequently Asked Questions)

1. What are rectifiers and their types?

A rectifier is an electrical device consisting of one or more diodes that allow the unidirectional flow of current. It basically converts AC into DC.

The rectifiers are categorized into three types namely uncontrolled, half controlled, and full controlled rectifiers.


2. Why half-wave rectifiers are not used in dc power supply?

The half-wave rectifier is used most commonly in low-power applications because the output amplitude is less than the input amplitude and there is no output during the negative half-cycle.