Bridge Rectifier – Definition, Characteristics, & Types

Bridge Rectifier 

Generally, the rectifier circuit converts alternating current into direct current. The basic function of each of these rectifiers is to convert current, yet they all perform this task inefficiently. 

One often-found component of electronic power sources is a bridge rectifier circuit. Many electronic circuits require a rectified DC power source to power the numerous electronic fundamental components from the available AC mains supply. This rectifier is used in many electronic AC power devices, including welding applications, motor controllers, residential appliances, and modulation processes. So let’s start with what is a bridge rectifier.

What is a bridge rectifier?

Here you can understand what is bridge rectifier! A bridge rectifier is a full wave rectifier that effectively transforms alternating current into direct current using four or more diodes in a bridge circuit design (DC). Any other regulated solid-state switch or four or more diodes can be used to build them.

A suitable bridge rectifier is chosen based on the need for the load current. When choosing a rectifier power supply for an acceptable electronic circuit’s application, factors such as component ratings and specifications, temperature, transient current rating, breakdown voltage, forward current rating, mounting requirements, and others are considered.

Many electronic circuits employ its circuit (as shown in the bridge rectifier diagram) to deliver power to many electronic fundamental components.

Bridge Rectifier Construction

Below is a diagram illustrating its construction. The four diodes can be used in this circuit, along with a load resistor. These diodes can be connected in a closed-loop arrangement to convert AC (alternating current) to DC (direct current). This design’s key advantage is that it does not require a special center-tapped transformer. Therefore, both the size and the price will be decreased.

The output DC signal can be obtained across the RL once the input signal is applied across two terminals. In this case, a load resistor is attached between two terminals. Two diodes can be placed in such a way that two diodes will conduct electricity during each half cycle. Electric current will flow via diode pairs like D1 and D3 for the duration of the positive half cycle. D2 and D4 diodes behave similarly, conducting current during a negative half cycle.

Bridge rectifier diagram 

Key points about the construction of the Bridge rectifier

A resistor (RL) and four diodes (D1, D2, D3, and D4) make up the bridge rectifier or bridge full-wave rectifier circuit.

1. A closed-loop connection between these four diodes effectively transforms alternating electricity into direct current.
2. The output DC signal is obtained across the Resistor RL, connected between the M and L terminals, and applied to Terminals A and B with the input AC signal.
3. The four diodes are arranged so that only two of them—D1 and D3—conduct electricity during a positive cycle, while D2 and D4 do so during a negative cycle.
4. The changes keep happening as long as the current keeps moving.

Working on the bridge rectifier

Its principal benefit is that it generates roughly twice as much output voltage as a full-wave rectifier using a center-tapped transformer. However, this circuit is similar to a low-cost rectifier because it does not require a center-tapped transformer.

The circuit diagram for it includes several components, including a transformer, a diode bridge, filtering, and regulators. A regulated DC power supply is what all these building blocks are commonly referred to as, and it powers numerous electronic equipment.

The input signal flows alternately, or in a positive and negative cycle, across the bridge rectifier.

1. Terminal A turns positive, and terminal B turns negative during the positive half cycle.
2. During both the positive and negative half cycles, the same amount of current flows across the resistor RL.
3. The output DC signal’s polarity might be either positive or negative.
4. To achieve an entirely negative voltage, we can reverse the direction of the diodes.

Bridge Rectifier’s Characteristics

The following are the various characteristics :

1. Ripple Effect

The ripple Factor can be described as the output DC signal’s smoothness.

1. A smooth DC signal is an output DC signal with fewer ripples, whereas a pulsing DC signal is an output DC signal with more ripples.
2. The ratio of ripple voltage to pure DC voltage is known as the ripple factor.

A bridge rectifier is thought to have a ripple factor of 0.48.

Γ = √ (Vr_ms²/VDC)⁻¹

2. Bridge Rectifier Efficiency

How well it converts AC to DC is a straightforward way to determine its efficiency. The ratio of DC output power to AC input power can be interpreted as its efficiency.

Its efficiency should be considered to be 81.2 percent.

3. Peak Inverse Voltage

The highest voltage that a diode can withstand when reverse-biased is known as peak inverse voltage.

Peak Inverse Voltage (PIV) or Maximum Reverse Bias Voltage (MRV) is the maximum voltage that a diode can withstand. 

Peak Inverse Voltage is the highest voltage that a non-conducting diode can withstand (PIV). 

The diodes D1 and D3 are in the conducting state during the positive half cycle, while D2 and D4 are in the non-conducting state. The diodes D1 and D3 are in the non-conducting state during the positive half cycle, while the diodes D2 and D4 are in the conducting state. 

For a bridge rectifier, the Peak Inverse Voltage (PIV) is given by,

VSmax = PIV 

Ripple Factor: 

The use of a factor known as the ripple factor allows for the measurement of the output DC signal’s smoothness. When there are relatively few ripples in the output DC signal, it is said to be smooth, however, when there are many ripples, it is said to be high-pulsating. 

The ratio of the ripple voltage to the pure DC voltage is known as the ripple factor in mathematics.

 The ripple factor for a bridge rectifier is given by, 

 The bridge rectifier’s ripple factor is 0.48, the same as that of a center-tapped full-wave rectifier. 

Rectifier efficiency 

The efficiency of the rectifier determines how effectively it transforms AC (alternating current) into DC (direct current) (DC). 

 A most reliable rectifier will have a high-efficiency rating, while a subpar rectifier will have a low-efficiency rating.

The DC output power to AC input power ratio is referred to as rectifier efficiency. 

A bridge rectifier’s maximum rectifier efficiency is 81.2%, the same as a center-tapped full wave rectifier. 

Different Types Of Bridge Rectifiers 

Bridge rectifiers are separated into many kinds based on supply characteristics, controllability, bridge circuit configuration, and other factors. Single-phase and three-phase rectifiers are the two main types of bridge rectifiers. These categories are further separated into fully regulated, somewhat controlled, and uncontrolled rectifiers. A handful of these rectifier types are described below.

1. Single Phase and Three Phase Rectifiers

These rectifiers are determined by the type of supply, such as a single-phase or three-phase supply. The picture indicates that a three-phase rectifier employs six diodes, whereas a single-phase bridge rectifier utilizes four diodes to convert AC into DC. These rectifiers can again be controlled or uncontrolled, depending on the circuit’s diodes, thyristors, and other components.

2. Uncontrolled Bridge Rectifiers

As seen in the image, this bridge rectifier uses diodes to rectify the input. Because the diode is a unidirectional device, the current can only flow in one way through it. The rectifier’s diode configuration prevents the power from changing in response to the demands of the load. In continuous or fixed power supplies, this type of rectifier is employed.

3. Controlled Bridge Rectifier

SCRs, MOSFETs, IGBTs, and other controlled solid-state components are used in place of uncontrolled diodes in this sort of rectifier, AC/DC converter, or rectifier to regulate the output power at various voltages. It is possible to adjust the output power at the load in a sensible manner by triggering these devices at different intervals.

Advantages of bridge rectifiers

1. The output ripples of the DC signal are very small

The DC output signal of a bridge rectifier is more reliable than a half-wave rectifier. In other words, a bridge rectifier produces fewer ripples than a half-wave rectifier. On the other hand, the ripple factor of the bridge rectifier is the same as that of the center-tapped full bridge rectifier.

2. Improved rectifier efficiency

The bridge rectifier has a much higher efficiency than the half-wave rectifier. However, the center tapped the full bridge rectifier, and the bridge rectifier has the same rectifier efficiency.

3. Less power loss

Only one-half cycle of the incoming AC signal is allowed in a half-wave rectifier, blocking the other half cycle. Consequently, more than 50% of the input power is lost.

On the other hand, the bridge rectifier allows electricity to flow during both the positive and negative half of the input AC signal. As a result, the AC power input and DC power output are practically equal.

Disadvantages of Bridge Rectifier 

• The Bridge rectifier circuit appears to be pretty complicated

A center-tapped full rectifier uses two diodes, whereas a half-wave rectifier only uses one. However, it uses four diodes to operate the circuit. Compared to the half-wave rectifier and center-tapped full-wave rectifier, the bridge rectifier circuit appears more complicated.

• There is more power loss when compared to the center-tapped full-wave rectifier

Voltage loss in electrical circuits increases as the number of diodes used increases. It loses power at roughly the same rate as full wave center-tapped rectifiers. It has a slightly higher voltage drop than a center-tapped full-wave rectifier. This has happened as a result of two extra diodes.

This is all about its theory’s types, circuits, and operating principles. We believe that this full information on the subject will be useful in helping pupils develop their electronics or electrical projects and look at various electronic gadgets and appliances.

Frequently Asked Questions (FAQ) 

1. How can you use a Bridge Rectifier to convert AC power to DC?

It can be a half-wave rectifier, which rectifies only one-half of the alternating current signal, or a full-wave rectifier, which rectifies both cycles of the alternating current signal. The full-wave rectifier can be either a center-tapped rectifier with two diodes or a bridge rectifier with four diodes.

2. What is the importance of the PIV voltage of a Diode in A Rectifier Circuit? 

A diode can sustain a maximum voltage known as PIV (Peak Inverse Voltage) when biased oppositely. When a voltage is put across a diode higher than the peak inverse voltage, an avalanche breakdown occurs, irreversibly damaging the diode. The PIV of the diode should, therefore, always be higher than its maximum reverse voltage.

3. What is the PIV of a full-wave center-tapped rectifier, and why?

The PIV of a center-tapped full-wave rectifier is 2Vmax or twice the maximum voltage. Because with a center tap rectifier, the total voltage across the winding’s two end terminals is 2Vmax, the voltage across the two half-windings becomes 2Vmax.