Bridge Rectifier: Construction, Types, Working, and Applications

Bridge Rectifier: Construction, Types, Working, and Applications

A bridge rectifier is a circuit that converts AC into DC. This article explains what it is, how it works, and how its four diodes allow full-wave rectification. It also covers different rectifier types, circuit diagrams, waveforms, uses, advantages, disadvantages, efficiency, and ripple. These show why bridge rectifiers are common in electronics.

What is a Bridge Rectifier and How Does It Work?

A bridge rectifier is a circuit that converts AC (alternating current) into DC (direct current). It uses four diodes arranged in a bridge. These diodes control the current flow so the output always moves in one direction. This process is called full-wave rectification. It uses the entire AC signal, unlike a half-wave rectifier.

Construction of Bridge Rectifier

The bridge rectifier circuit has four diodes (D1, D2, D3, and D4) connected in a closed loop. The AC input is connected to two opposite points of the bridge, and the load is connected to the other two points. This setup ensures that during each half of the AC cycle, two diodes conduct while the other two block, directing current through the load in one direction.

The four diodes can be placed on a PCB or built into a single bridge rectifier module for convenience. A filter capacitor is usually added across the output to smooth the pulsating DC and make it more stable.

Types of Bridge Rectifiers

Bridge rectifiers can be classified based on the power phase and the type of control used in the circuit:

Single-Phase and Three-Phase Bridge Rectifiers

A single-phase bridge rectifier uses a single-phase AC source and four diodes arranged in a bridge. Two diodes conduct in each half-cycle, producing a full-wave DC output. It is simple, low-cost, and commonly used in adapters, power supplies, and household electronics.

A three-phase bridge rectifier works with a three-phase AC supply and uses six diodes. Two diodes conduct at a time, providing a higher DC output with less ripple than a single-phase rectifier. This type is used in industrial applications, such as motor drives, welding equipment, and high-power DC systems that requires stable and smooth DC.

A fully controlled bridge rectifier replaces all four diodes with thyristors (SCRs). By adjusting the firing angle of each SCR through gate signals, the conduction period can be controlled precisely. This allows for regulation of the average DC output voltage and current, making it ideal for variable DC power supplies, industrial motor drives, and applications requiring voltage control and speed regulation.

Half-Controlled Bridge Rectifier

A half-controlled bridge rectifier uses two diodes and two SCRs in a bridge. One-part works like a normal diode rectifier, while the other allows controlled conduction through the SCRs. This setup gives partial control of the output voltage but keeps the circuit simpler and cheaper than a fully controlled bridge. It's commonly used in medium-power circuits, adjustable DC supplies, and industrial systems that need moderate voltage control.

Applications of Bridge Rectifiers

• Power Supply Units

The main use of bridge rectifiers is in DC power supplies. They change the AC from the mains into DC, which powers devices like TVs, radios, laptops, and chargers.

• Battery Charging

Bridge rectifiers are used in battery chargers to provide a steady DC voltage for charging automotive, emergency, and portable batteries.

• DC Motor Drives

Many DC motors run on rectified DC power. Bridge rectifiers supply this power for motors in fans, pumps, machines, and automation systems.

• Welding Equipment

Three-phase bridge rectifiers provide the stable, high DC current needed for industrial welding machines, ensuring consistent performance.

• Signal Demodulation

In communication circuits, bridge rectifiers help demodulate AM signals, converting them into DC signals for further processing.

• Industrial Control Systems

They are also used in industrial controls, inverters, and HVAC systems to supply stable DC for sensors and controllers.