Uses of Rectifier

A rectifier is an electrical device that converts AC to the DC current. A mobile device can only be charged efficiently if a steady, continuous voltage supply is provided to it. When the charger is connected to the grid, the AC input supplied is 220 V, and this supply, when passed through the charger, results in an output of 5V DC. This is achieved through the use of a rectifier within the charger’s circuit.

kelingyizhi Product Page

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

Introduction

Rectifiers are utilized in a multitude of devices and serve various functions across different applications. They are essential in adjusting network systems and can be classified based on several factors, such as type, bridge configuration, and the components utilized. Rectifiers employ P-N junction type diodes which facilitate the conversion of alternating current to direct current. To better grasp the Uses of Rectifier - Types and Their Uses and Functions, students can refer to resources provided by Vedantu, which clarifies the concepts and real-life applications.

In this article, we will explore:

• Application of rectifier

• Full-wave rectifier applications

• How rectifiers convert

• Uses of the half-wave rectifier

• Uses of the full-wave rectifier

• What is a rectifier?

• Types of rectifier

• Rectifier function

• Full-wave bridge rectifier

Rectifier Function

A rectifier transforms AC into pulsating DC using a P-N junction diode. This diode facilitates current flow in a forward-biased condition and restricts current in a reverse-biased condition. Essentially, a P-N junction diode allows current to flow in one direction only, a characteristic that enables it to function as a rectifier. An example of this process is illustrated in the output waveform for a basic rectifier.

Types of Rectifier

Half-wave Rectifier: This rectifier operates on the principle that the input voltage follows a sinusoidal wave during the positive half-cycle only.

Full-Wave Rectifier

1. Full-wave centre-tapped rectifier

2. Full-wave bridge rectifier

Half-Wave Rectifier

This electrical device converts AC voltage into DC voltage and permits only one half-cycle of an AC waveform while blocking the other half-cycle. A single diode suffices for its construction. The diode’s property enables a unidirectional current flow.

For instance, Fig.1 demonstrates the operation of a half-wave rectifier, where the input AC waveform with both positive and negative cycles yields a DC output devoid of the negative cycle after rectification.

Rectifier efficiency is calculated using the equation:

η = Pdc / Pac

Where ηmax = 40.6 % (low)

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

Uses of a Half-wave Rectifier

The half-wave rectifier has several practical applications, including:

Used in

• Low-power battery charger circuits.

• Pulse generator circuits.

• Signal demodulation circuits.

• Firing circuits.

• Soldering iron circuits.

• Amplitude modulation (AM) radio circuits as a detector.

Full-Wave Rectifier

A full-wave rectifier is designed to convert alternating current voltage into pulsating DC voltage using both half cycles of the applied AC voltage supply.

This circuit utilizes two diodes, with one conducting in one-half cycle while the other remains off, and vice versa during the other half cycle of the AC voltage. As such, both positive and negative output cycles are produced, with one diode halting current flow while the other permits it.

For both input AC signals, either positive or negative, a DC output is generated.

Full-Wave Bridge Rectifier

A full-wave bridge rectifier employs both half cycles of the input AC and converts them into DC. Four diodes (D1, D2, D3, D4) are arranged in a bridge formation, giving this setup its name.

The Positive Half-cycle

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

The Negative Half-cycle

During the negative half-cycle, diodes D3 and D4 become forward biased, with D1 and D2 remaining off. Current then continues to flow through the load in the same direction as before.

Applications of a Full-wave Bridge Rectifier

Full-wave bridge rectifiers are preferred for their cost-effectiveness due to the use of lightweight and highly efficient diodes.

Important applications of the full-wave bridge rectifier include:

• Mobile phones, laptops, and charger circuits.

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

• Home inverters which convert AC to DC.

• LCD and LED TVs.

• Car alternators for charging batteries while driving.

• LED driver circuits.

• Audio amplifiers.

• Radios.

The Need for Rectifiers

The two voltage types predominantly observed are classified as either alternating or direct voltage. These voltages can be interconverted depending on the circuit design employed. For example, household power requires a small amount of DC voltage, while the mains supply typically provides AC voltage. Thus, the conversion of AC to DC is essential, and rectifiers serve this purpose effectively within circuits.

For further details on the work of rectifier, please contact us for professional insight.

Additionally, rectifiers facilitate the interconversion of current types, converting alternating current to the necessary direct current needed by most home appliances. It is also observed that these rectifiers process both positive and negative components of the current, yielding an output composed exclusively of positive components.

A basic diode has numerous applications, including its role in rectifiers. Rectification can be conducted with simple diodes, converting AC values into DC either in terms of voltage or current. The fundamental property of diodes allows them to establish a unidirectional current flow during forward bias, while they remain non-conductive during reverse bias, leading to their utilization in rectification processes. This article encompasses the basics surrounding rectifiers, covering their operational theory, functioning, circuit diagrams, equations, and various applications.

What is Rectifier?

Definition: A standard diode, structured from p-type and n-type materials, is employed to convert alternating currents to direct currents. This phenomenon is termed rectification, with the circuitry designated for this process referred to as a rectifier.

The operational principle of a diode, whether a P-N junction, revolves around its ability to conduct in a forward bias or inhibit current flow in reverse bias.

In forward bias, the diode conducts since the p-type is linked to the positive end of the installation and the n-type connects to the negative end. This configuration enables electrons to migrate from the n-side to the p-side, while holes traverse from the p-side to the n-side.

As these carriers move, they facilitate current generation, referred to as forward current.

Conversely, if the p-type is connected to the negative supply and the n-type to the positive, the diode is reverse biased.

In this scenario, majority charge carriers are pulled towards the respective battery terminals, allowing only a negligible minority current to flow.

Due to the minimal reverse current caused primarily by minority charge carriers, the diode effectively blocks most reverse current. These principles underpin the functioning of diodes within rectifier applications.

These basic biasing concepts form the theoretical foundation of rectification.

Functioning

Biasing primarily employs DC supply, but for rectifiers, AC must be factored in. AC signals can represent sinusoidal waves while DC is typically depicted as a straight line.
The peak of the wave signifies the positive portion while its trough represents the negative side, with the positive indicating forward bias and the negative depicting reverse bias.

The AC waveform is not stable; it varies over time. As it peaks positively, it subsequently drops, mirroring the behavior as it approaches negative values before returning to zero.

Let's explore rectifier operation by applying AC input. During the positive cycle, the diode is in forward bias mode, enabling charge carriers to flow.

Once subjected to the negative part, the diode obstructs current flow as negligible minority carriers remain. Simply put, a diode conducts during a positive cycle and blocks during negative cycles, demonstrating rectifier functionality.

Consequently, current flows during the positive segment of the cycle, achieving conversion from AC to DC. This is how a basic diode serves as a rectifier.

General Representation of Power Supply

However, rectifiers typically do not produce pure forms of DC output, which contain residual AC components known as ripples. These ripples can be eliminated with filters connected across the rectified output, ensuring a smoothing effect. The efficiency is deemed optimal when the ripple factor is minimized.

Rectifier Circuits

Rectifier circuits can generally be classified as:

• Half Wave Rectifiers
• Full Wave Rectifiers

Rectifier Circuit of Half Wave

A half-wave rectifier comprises a basic circuit featuring a single diode connected to a series AC supply and load resistor. Here, the diode only conducts during the positive cycle, making analysis straightforward.

Rectifier Equations of Half Wave Rectifier

The average voltage value can be calculated as:

Vavg= Vm/π

The average current value can also be expressed as:

Iavg=Im/π

The RMS voltage can be calculated as:

Vrms=Vm/2

The RMS current can be given as:

Irms=Im/2

The ripple factor for the half-wave rectifier is:

Ripple Factor=1.21

The rectifier's efficiency is expressed as:

maximum efficiency=40.6%

The form factor can be expressed as:

form factor=1.57

These equations summarize the operational principles of the half-wave rectifier.

Rectifier Circuit of Full Wave

Full-wave rectifiers are categorized into center-tapped and bridge circuits, providing greater efficiency by utilizing both cycles and minimizing power loss.

Centre Tapped Full Wave Rectifier Circuit

This design incorporates a center-tapped transformer along with two diodes connected to a resistive load. One diode engages during one phase of the cycle while the other does so for the opposite phase, preventing power output loss.

Centre Tapped Rectifier Circuit

A limitation of this type of rectifier is the cost associated with the center-tapped transformer, leading to the design of the bridge rectifier.

Bridge Rectifier Circuit

This rectifier consists of four diodes configured in a bridge topology, providing a solution to the limitations of center-tapped rectifiers. Diodes D1 and D2 conduct during one cycle while D3 and D4 engage during the other part of the cycle, leveraging both AC halves and utilizing a standard transformer to reduce costs.

Rectifier Equations for Full Wave

The average voltage value can be expressed as:

Vavg=(2Vm)/π

The average current value can be calculated as:

Iavg=(2Im)/π

The RMS voltage value can be expressed as:

Vrms=Vm/'2

The RMS current can be calculated as:

Irms=Im/'2

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

E=81.2%

The form factor value is:

form factor=1.11

The aforementioned details summarize the equations for full-wave rectifiers. Moreover, rectifier equations are also outlined below:

1) Average Value

The instantaneous value of the signal averaged over the respective area is termed the average value of the rectifier.

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

2) RMS Value for the Rectifier

Referred to as the square root of the mean values.

RMS value of the signal='((area present under the respective curve squared)/(length of the base))

The thermal output produced by an AC signal's RMS value matches that of DC current flowing through a similar resistance.

3) Peak Factor of the Rectifier

The ratio between the maximum peak value of the applied signal and its RMS value 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 input signal to its average value denotes the form factor.

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

5) Ripple Factor

Defined as the ratio of the AC component's RMS value to the DC component in the output stream.

γ=VAC/VDC

The final equation for the ripple factor reads:

γ='((VRMS/VDDC)^2' 1)

6) Efficiency of the Rectifier

The efficiency of the rectifier is derived from the ratio of DC output power to applied input power.

E=PDC/PAC

Advantages

The principal advantage of rectifiers lies in their capability to convert alternating current into direct current.

Applications

• Rectifiers serve as integral components of power supply circuits due to their rectification properties.
• Utilized within power supply units employing switching-mode techniques.
• Excelling in the detection of amplitude in modulated radio signals.
• Providing a polarized voltage supply for welding purposes.

This overview highlights fundamental features of basic rectifiers, demonstrating their importance in power supply systems. However, practical applications necessitate filters to optimize utility. Further inquiries may address the application of rectifiers in ADC conversions or alternative conversion methods.

To learn more details, please visit flatpack2 48/.