Rectifier

Rectifier is an electronic component that converts alternating current (AC) into direct current (DC), ensuring a unidirectional flow of electric charge. As we know, electricity reaches our homes from power grids in the form of AC, but most commonly used electric appliances, such as mobile phones, computers, televisions, fridges, etc operate on direct current (DC). Therefore, the rectifier becomes a very useful component in electronics.

This article provides a detailed understanding of the electrical component known as a rectifier, including its types such as full-wave and half-wave rectifiers, controlled and uncontrolled rectifiers, etc. In addition to that, we will learn about various specific rectifiers such as the Mercury Arc Rectifier, Selenium Rectifier, and Precision Rectifiers.

What are Rectifiers?

Rectifiers are electronic devices or circuits that convert alternating current (AC) into direct current (DC). Alternating current periodically changes direction, whereas direct current flows consistently in one direction. Rectifiers are crucial in many electronic applications where a steady DC voltage is required.

Most rectifiers use P-N junction diodes to convert AC to DC, but some use different kinds of materials as well, such as semiconductor materials like silicon carbide or specialized semiconductor devices like thyristors and metal-oxide-semiconductor field-effect transistors (MOSFETs).

How does Rectifier Work?

A rectifier is an electrical device which is used to convert AC current into DC current. Rectifier does this process by allowing current (I) to flow through any device and the process taking place here is called rectification.

Rectifier works by using diodes which are like one-way valves for electricity. A rectifier can take one or more diodes to convert the positive or negative half cycle of the AC inputs DC outputs. Rectifiers generates an DC voltage by rectifying any one cycle of the AC supply and the reverse operation of this above process is called Inverter and the process called inversion in electricity.

Rectifiers Circuits

It plays a vital role in DC power supplies for converting AC signal into DC signal. P-N junction diode have lot of applications and Rectifier circuits are one of them. In simple words the electronic circuit which performs rectification is called rectifier circuit. By using this circuit we can able to convert electrical signals.

Types of Rectifiers

There are various types of rectifiers used in electronics for different use cases. Some of these rectifiers are:

• Half-Wave Rectifier
  • The simplest type of rectifier.
  • Uses a single diode to allow current to flow in only one direction during one half-cycle of the AC waveform.
  • Efficiency is relatively low.
• Full-Wave Rectifier
  • Utilizes two diodes to rectify both halves of the AC waveform.
  • Improved efficiency compared to half-wave rectifiers.
    • Center-Tap Full-Wave Rectifier: Uses a center-tapped transformer.
    • Bridge Rectifier: Uses four diodes in a bridge configuration, eliminating the need for a center-tapped transformer.
• Bridge Rectifier
  • A type of full-wave rectifier that uses four diodes in a bridge configuration.
  • More efficient than center-tap full-wave rectifiers.
  • Commonly used in power supplies and electronic devices.
• Bridgeless Rectifier
  • A variation of the bridge rectifier that minimizes voltage drops associated with diodes.
  • Uses additional switches to control the flow of current.
  • Offers improved efficiency compared to traditional bridge rectifiers.
• Voltage Doubler Rectifier
  • A circuit that doubles the output voltage of a rectifier.
  • Uses capacitors to store and deliver additional charge during the rectification process.
• Cockcroft-Walton Multiplier
  • A voltage multiplier circuit that generates a high DC voltage from a low AC voltage.
  • Often used in particle accelerators and high-voltage power supplies.
• Chopper Rectifier
  • Uses a switch (chopper) to control the output voltage.
  • Can provide variable DC output voltage by adjusting the duty cycle of the chopper.
• Schottky Rectifier
  • Uses a Schottky diode, which has a lower forward voltage drop compared to standard diodes.
  • Faster switching speed and lower power loss.
• Synchronous Rectifier
  • Utilizes active components such as MOSFETs instead of diodes.
  • Offers lower conduction losses and improved efficiency.
• Zener Diode Rectifier
  • Uses Zener diodes for voltage regulation.
  • Provides a constant output voltage despite fluctuations in input voltage.

Other than these types, rectifiers can be classified as Controlled rectifier and Uncontrolled rectifier.

• Controlled Rectifier: In this type of rectifier, voltage always varies and MOSFET, SCRs or IGBTs are used to convert uncontrolled rectifier to controlled rectifier. It consists of two other types of rectifiers which is
  • Half Wave Controlled Rectifier
  • Full Wave Controlled Rectifier
• Uncontrolled Rectifier: In this type of rectifier, voltage cannot be controlled or it cannot vary with respect to time. There are two types of uncontrolled rectifier that is
  • Half Wave Uncontrolled Rectifier
  • Full Wave Uncontrolled Rectifier
    • Uncontrolled rectifier uses diodes and they generate a fixed output voltage depending only on AC inputs.
    • It works with switches and here in this type of rectifier diodes play a important role.
• This rectifier cannot be controlled because it is connected in forward biased.

Half Wave Rectifier

It is easy to construct. Similar to rectifier Half way rectifier is used to convert AC (Alternating Current) signal into DC (Direct Current) signal by passing through negative or positive half cycle. The only drawback is it is less efficient by comparing to full-wave rectifier. In simple words Half wave rectifier produces purely positive by avoiding negative half-cycle on the other hand full wave rectifier produces purely negative half cycle by changing the direction. The efficiency of half wave rectifier is 40.5% which is considered as lower than full wave rectifier.

Half Wave Rectifier Circuit

Circuit for Half Wave Rectifier is given below:

Full Wave Rectifier

It requires multiple diodes to function and to construct. It is a process of converting AC signal into DC signal (AC voltage into DC voltage). As we know that electrical circuits which convert AC into Direct current are called rectifiers. Full wave rectifier rectifies both negative and positive half cycle of input which is alternating signal. The efficiency of full-wave rectifier is twice than that of half-wave rectifier. So these rectifiers are maximum used in all electronic devices because it can withstand high voltages or current with intense power.

Full Wave Rectifier Circuit

Circuit for Full Wave Rectifier is given below:

Bridge Rectifiers

It is an type of full-wave rectifier which uses four diodes to form a close-loop bridge. It conduct in pairs through each positive and negative half cycle which leads to no power wastage. It is also called rectified output voltage. Rectifiers are mainly used in power supply, providing DC voltage for electronic devices to function. It doesn’t require any center tap over the secondary winding of the transformer .

Here Let us see the working of bridge rectifier the input is fed through transformer to the cross section of diagonal bridge . Here the transformer is always busy due to power supply to the both cycle all the time of input AC.

Bridge Rectifiers Circuit

Circuit for Bridge rectifier is given below:

Some Specific Types of Rectifiers

Other than all these discussed types of rectifiers, there are some special types of rectifiers. Some of these are:

• Mercury Arc Rectifier
• Selenium Rectifier
• Precision Rectifiers

Let’s discuss these types in detail as follows.

Mercury Arc Rectifier

It is used to convert AC power into DC power and it is used in the earlier stages which is before the invention of solid state devices called thyristors. It is used to handle powers of hundred of kilowatts. It consists of evacuated glass vessel with a pool of mercury at the bottom acting as a cathode and at the top is an anode. Here the operation will occur due to mercury vapor discharge in a sealed tube to create an electrical barrier that allows current to flow in only one direction. It is widely used in industry and military applications.

Selenium Rectifier

It is a type of rectifier which is invented in 1933 that uses selenium which is an chemical element acts as an semiconductor for electrical conductivity. it is used for power supplies for power equipment and in high-current battery charger applications until they were superseded by silicon diode rectifiers. They were made up of stacks of aluminium or steel plates coated with about 1 μm of bismuth or nickel. it is about same size as a copper oxide rectifier.

Precision Rectifiers

It is an type of rectifier obtained with Op-amp in order to have a circuit functions like an ideal diode and rectifier. It is highly used for high-precision signal processing. It conducts perfectly when it is forward-biased , without any forward voltage drop and it blocks when reverse bias occurs.

Advantages of Rectifiers

Main advantages of rectifiers are:

• Converts AC to DC power for electronic devices.
• Essential for battery charging in devices and electric vehicles.
• Used in industrial processes like electroplating and welding.
• Enables efficient HVDC power transmission over long distances.
• Provides controlled and stable DC power for precision applications.
• Integral in renewable energy systems for converting variable AC to DC.
• Facilitates signal processing by converting AC signals to rectified signals.
• Contributes to energy efficiency in power conversion processes.
• Cost-effective and reliable for a wide range of applications.

Disadvantages of Rectifiers

Key disadvantages of rectifiers are:

• Generates harmonics and electrical noise during the conversion process.
• May require additional filtering components to reduce output ripple.
• Limited in handling high power levels compared to some alternative technologies.
• Efficiency can decrease at partial loads or when operating away from design conditions.
• High initial costs for certain types of rectifiers and associated equipment.
• Some rectifiers may have a relatively lower power factor, leading to poor power quality.
• Maintenance may be required, especially in heavy industrial applications.
• Possibility of heat generation, requiring cooling mechanisms in high-power rectifiers.
• Incompatible with AC-powered devices, necessitating additional conversion for certain applications.
• Environmental concerns, as certain types of rectifiers may contain hazardous materials.

Applications of Rectifiers

Some of the key application of rectifiers are:

• It is used for powering appliances as we know all electrical appliances use a DC power supply to function. By using rectifier in power supply and systems it helps in conversion of AC to DC.
• It is used to soldering and modulation as it is used in mosquito repellent to power the lead for the fumes.
• Voltage multiplier – As said earlier that rectifiers are used for power conversion such as AC power to DC power and so on same as they are used to convert AC to DC voltage for electronic appliances such as microwave ovens and so on.
• Used in Transformers to obtain desired voltage by using rectifier in combination with a step-down or step-up transformer.
• For Radio appliances rectifiers acts as an detectors because the output consists of an audio signals. For examples Modulation, Demodulation and power supplies.

Read More,

• Alternating Current
• Difference between AC and DC Generator
• Difference between AC and DC Motor

Sample Questions on Rectifier

Question 1: What happens to the width if the depletion layer of a P-N junction when it is forward biased and reverse biased?

Answer:

• Width of the depletion layer decreases in forward bias.
• Width of the depletion layer increases in reverse bias.

Question 2: What is the most common use of photo diode?

Answer:

It is used as a photodetector to detect optical signals.

Question 3: What type of impurity is added to obtain n-type semiconductor?

Answer:

Pentavalent atoms like phosphorus(P) and arsenic (As).

Rectifier: FAQs

1. What is Half Wave Rectifier?

A half-wave rectifier only converts half of an AC signal into a pulsing DC signal. It’s like a one-way valve for electricity, only letting through positive or negative half-cycles.

2. What is Full Wave Rectifier?

A full-wave rectifier converts both positive and negative halves of an AC signal into a pulsating DC signal, making it more efficient than a half-wave rectifier.

3. How many types of Rectifier there are?

There are two main types of rectifiers: Uncontrolled and Controlled.

4. What is the key difference between Rectifier and Inverter?

• Rectifier: AC to DC, simpler circuit, powers electronic devices.
• Inverter: DC to AC, more complex, supplies AC from batteries.

5. What is a Rectifier used for?

Rectifiers convert AC power to DC power, making them essential for powering electronics.

6. What is PN Junction Diode?

A PN junction diode is a one-way valve for electricity, allowing current to flow in one direction only (forward) and blocking it in the opposite (reverse). It’s the basic building block of many electronic devices.

7. How does PN Junction Convert AC to DC?

PN junction acts like a one-way valve, allowing current to flow in only one direction, effectively chopping off the negative half of the AC signal, resulting in pulsating DC.