Full Wave Rectifier Circuit

Full-wave rectifier is an electric circuit that helps to convert both half cycles of an alternating current (AC) into direct current (DC). These circuits are made either using multiple diodes or using diodes and a transformer. The main components of full-wave rectifier circuit include:

Also Read: Full Wave Rectifier Efficiency and Their Applications

Full Wave Rectifier Circuit Diagram 

Diodes: These devices ensure that the current flows in one direction only and does not flow back.

Transformer: In some cases, a transformer is used to step down the voltage before it is rectified.

Load Resistance (R): This component is used to connect the rectifier circuit to the load.

How Does Full Wave Rectifier Work?

Here, we are going to show you detail information about working of full wave rectifier along with their all operations step by step:  

Also Read: Full Wave Rectifier Efficiency and Applications         

Input AC Signal: The full-wave rectifier starts with an alternating current (AC) input signal. This signal is usually in the form of a sinusoidal waveform.

Diode Bridge: In a full-wave rectifier, four diodes are arranged in a bridge configuration. The bridge rectifier allows current to flow through the load in one direction during both halves of the AC cycle.

Positive Half-Cycle: During the positive half-cycle of the AC input, two diodes become forward-biased, allowing current to flow through the load in a specific direction. The other two diodes are reverse-biased and block the current flow in the opposite direction.

Negative Half-Cycle: As the AC waveform enters the negative half-cycle, the roles of the diodes switch. The previously reverse-biased diodes become forward-biased, and vice versa. This allows current to flow through the load in the same direction as it did during the positive half-cycle.

Output: The result is a continuous flow of current in the same direction through the load during both halves of the AC cycle. The output across the load resistor is a pulsating direct current (DC) waveform.

Smoothing (Optional): To obtain a smoother DC output; capacitor is often connected in parallel with the load resistor. This capacitor helps reduce the ripple or variations in the output voltage.

DC Output: The final output across the load resistor is a relatively smooth DC voltage that has been rectified from the original AC input.

Types of Full Wave Rectifier

There are two commonly types of full wave rectifiers, like as the center-tapped full-wave rectifier and the bridge rectifier. They are effectively capable to convert AC signals into DC output voltages; both types have different circuit configurations and characteristics.

Centre-Tapped Full Wave Rectifier

Center tapped full-wave rectifier is a kind of rectifier circuit that is used in power supply applications to convert alternating current (AC) into direct current (DC). The center-tapped full-wave rectifier is an improvement over the simple full-wave rectifier that helping out to provide the higher efficiency and decrease the ripple in the output.

Here’s how a center-tapped full-wave rectifier works:

Transformer: The input to the rectifier is typically through a transformer. The primary winding of the transformer is connected to the AC supply, and the secondary winding has a center tap. The center tap serves as a reference point, dividing the secondary winding into two equal halves.

Diodes: Two diodes are connected in a bridge configuration, forming a bridge rectifier. The anodes of the diodes are connected to the ends of the secondary winding, and the cathodes are connected together.

Operation: During the positive half-cycle of the AC input voltage, the upper end of the secondary winding becomes positive with respect to the center tap. This forward-bias is one of the diodes that are allowing the current to flow through it. Simultaneously, the lower end of the secondary winding becomes negative, reverse-biasing the other diode, preventing current flow through it.

During the negative half-cycle of the AC input voltage, the polarities reverse. Now, the lower end of the secondary winding becomes positive, forward-biasing the second diode, while the upper end becomes negative, reverse-biasing the first diode.

Output: As a result, current flows through the load during both half-cycles of the AC input, creating a pulsating DC output. The center tap is often connected to the ground, and the DC output is taken from the common point of the diodes.

Bridge Rectifier

Bridge rectifier is also known as the full wave bridge rectifier; it is a type of rectifier circuit that is used to convert alternating current (AC) into direct current (DC). It is widely used in power supply applications due to its efficiency and simplicity. The bridge rectifier configuration uses four diodes connected in a bridge arrangement, and it doesn’t require a center-tapped transformer.

Here’s how a bridge rectifier works:

Diodes Configuration: Four diodes (labeled D1, D2, D3, and D4) are arranged in a bridge configuration. The AC input is applied across the diode bridge.

Operation: During the positive half-cycle of the AC input voltage, the voltage at terminal A (relative to terminal C) is higher than at terminal B. Diodes D1 and D2 become forward-biased, allowing current to flow through D1 and D2.

Simultaneously, diodes D3 and D4 become reverse-biased, preventing current flow through them.

During the negative half-cycle of the AC input voltage, the polarities reverse. Now, terminal B is at a higher voltage than terminal A. Diodes D3 and D4 become forward-biased, allowing current to flow through D3 and D4, while D1 and D2 become reverse-biased.

Output: As a result, current flows through the load during both half-cycles of the AC input, creating a pulsating DC output. The DC output is taken across the load connected between the points where D1 and D2 meet and where D3 and D4 meet.

Full Wave Rectifier Characteristics

There are several characteristics of full wave rectifier, including:

Also Read: Advantages and Disadvantages of Full Wave Rectifier

Rectification: Converts AC to DC using four diodes in a bridge configuration.

Input and Output Waveforms: AC input becomes a pulsating DC output.

Ripple Frequency: Output frequency is twice that of the input (2 times input frequency).

Ripple Factor: Approximately 0.48, indicating smoother output compared to half-wave rectifiers.

Peak Inverse Voltage (PIV): PIV is equal to the maximum AC voltage across the transformer secondary winding.

Transformer Utilization Factor (TUF): Higher TUF compared to half-wave rectifiers, indicating better transformer utilization.

Efficiency: Around 81.2%, higher than half-wave rectifiers.

Peak Current: Higher peak current compared to half-wave rectifiers.

Filtering: Capacitor filtering is often employed to smooth the pulsating DC output.

Load Resistance: Influences output voltage and current, higher resistance leads to higher DC voltage but lower DC current.

Difference between Half-Wave and Full-Wave Rectifier

Here is a comparison between Half-Wave and Full-Wave Rectifiers in tabular form:

Ripple Factor of Full Wave Rectifier

The ripple factor is a measure of the AC component or the “ripple” in the output of a rectifier circuit. It quantifies how much the DC output of the rectifier deviates from a pure DC voltage. For a full-wave rectifier, the ripple factor is given by the formula:

Ripple Factor = √V²_rms-V²_dc /V_dc

Where:

V_rms is the root mean square value of the AC component of the output voltage.

V_dc is the DC component of the output voltage.

For a full-wave rectifier, the RMS value of the AC component can be calculated as:

V_rms=V_m/2√2

Where:

V_m is the maximum voltage of the secondary winding.

The DC component V_dc is equal to the average value of the rectified voltage. For a full-wave rectifier, this can be calculated as:

V_dc=2V_m/ π

Substituting these values into the ripple factor formula, you can calculate the ripple factor for a full-wave rectifier. Keep in mind that a lower ripple factor indicates a smoother DC output.

It’s worth noting that if you assume ideal conditions and neglect the transformer and diode losses, the ripple factor for a full-wave rectifier is approximately 0.48.

Full-Wave Rectifier Formulas

Peak Inverse Voltage

The Peak Inverse Voltage (PIV) is the maximum voltage that appears across the diode in a rectifier circuit when it is in the reverse-bias condition. For a full-wave rectifier, the PIV occurs when the diode is reverse-biased during the portion of the AC cycle when the diode is not conducting.

In a full-wave rectifier, the PIV can be calculated using the formula:

PIV=2⋅V_m

Where:

• PIV is the Peak Inverse Voltage.
• V_m is the peak voltage of the input AC waveform.

RMS Value of Current

In a full-wave rectifier, the RMS (Root Mean Square) value of the output current can be calculated using the formula:

I_rms= I_m /√2

Where:

• I_rms is the root mean square value of the current.
• I_m is the maximum or peak value of the current.

DC Output Voltage

The DC (direct current) output voltage of a full-wave rectifier can be calculated using the formula:

V_DC=2 √2⋅V_max/π

Where:

• V_DC is the DC output voltage.
• V_max is the maximum or peak voltage of the input AC waveform.

Efficiency of Full-Wave Rectifier

The efficiency (η) of a full-wave rectifier can be calculated using the following formula:

η=PDC/PAC

Where:

• η is the efficiency.
• P_DC is the DC power delivered to the load.
• P_AC is the AC power drawn from the source.

The formula for P_DC is given by:

P_DC=I_DC⋅V_DC

Where:

• I_DC is the average DC current.
• V_DC is the DC voltage across the load.

The formula for PAC is given by:

P_AC=I_rms⋅V_rms

Where:

• I_rms is the RMS current.
• V_rms is the RMS voltage of the input AC waveform.

Form Factor

The form factor (F.F.) of a waveform is the ratio of its root mean square (RMS) value to its average (or mean) value. For a full-wave rectified waveform, the form factor can be calculated using the formula:

Form Factor (F.F.) = V_rms/V_avg

Where:

• V_rms is the RMS voltage of the waveform.
• V_avg is the average (or mean) voltage of the waveform.

Peak Factor

The peak factor (also known as the peak-to-average ratio) of a waveform is the ratio of its peak value to its RMS (Root Mean Square) value. For a full-wave rectified waveform, the peak factor can be calculated using the formula:

Peak Factor= V_m/V_rms

Where:

• V_m is the peak voltage of the waveform.
• V_rms is the RMS voltage of the waveform.

FAQs (Frequently Asked Questions)

What is the working principle of full wave rectifier?

Full-wave rectifier converts alternating current (AC) to direct current (DC) by using diodes to allow the flow of current in both positive and negative halves of the AC cycle, resulting in a more continuous and smoother DC output.

What are the key components of full-wave rectifier circuit?

The main components of full-wave rectifier circuit include diodes, a transformer (for center-tap rectifiers), and load resistor. In a bridge rectifier, four diodes are arranged in               bridge configuration.

Why full wave rectifier is used?

Full-wave rectifiers are used because they offer several advantages over half-wave rectifiers, such as higher efficiency, smoother output waveforms, and the ability to utilize both halves of the AC cycle. Their essential components are used in several electronic applications, like as power supplies, battery charging systems, signal processing circuits, and mobile phones.

What is the role of a smoothing capacitor in a full-wave rectifier circuit?

Smoothing capacitor is often added to the full-wave rectifier circuit to decrease the ripple in the DC output. It helps in smoothing out the variations in voltage, producing the more stable DC output for attached devices.

What are different types of full wave rectifier with diagram?

Full wave rectifier is classified into two different categories, including centre-tapped full wave rectifier and full-wave bridge rectifier. Above in this article, we already have been explained with their suitable circuit diagram; you can check them.

What is the operation of three phase full wave rectifier?

Three-phase full-wave rectifier operates by using two half-wave rectifier circuits, which produce a lower ripple output than a half-wave rectifier. It utilizes two diodes per phase and can be fed by a star or delta connected transformer supply.

Closure

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Also Read: Ripple Factor of Full Wave Rectifier with Formula

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