Bridge Rectifier is an important electrical component that is used in power supply units. It is used as AC to DC converter. Stay on and head further to dig out everything about Bridge Rectifier Circuit, it’s types, how it works, characteristics, applications and advantages.
What is Bridge Rectifier
Bridge Rectifier is an integral part of all the electronic appliances which use DC to function. Many components use DC current as they require constant voltages and hence conversion of AC to DC is essential.
The Bridge Rectifier circuit is a component that helps to convert AC mains supply to DC. They can easily be designed by using one or more Diodes which are uncontrollable and unidirectional or other controllable solid-state switches.
Fig. 1 – Introduction to Bridge Rectifier
There are many types of Bridge Rectifiers. But the one you will require will be determined by the load requirements. While choosing Bridge Rectifier for power supply, there are several things which are taken into consideration.
Few necessary factors to be considered are- the rating of the component, breakdown voltage, specifications, range of temperature, forward rating of current, transient rating of current, mounting requirements, etc. Considering all of these and the load requirements, you can choose the appropriate Bridge Rectifier Circuit.
Fig. 2 – Bridge Rectifier Power Supply Board
Types of Bridge Rectifiers
The Bridge Rectifiers can be classified on the basis of factors like- circuit configuration, controlling capabilities, and the types of supply. Trace the pointers below and find out everything about the types of Bridge Rectifiers as few of them are enlisted below and are briefly described:
- Single- Phase and Three- Phase Bridge Rectifiers
- Uncontrolled Bridge Rectifiers
- Controlled Bridge Rectifiers
1. Single- Phase and Three- Phase Bridge Rectifier
The nature of supply which can be a Single- Phase or Three- Phase determines the rectifiers. There are four diodes in the Single- Phase rectifiers and this is used to convert AC to DC. But on the other hand, the Three- Phase rectifiers use six diodes for the same purpose and the components used in the construction of the bridge determine whether your Bridge Rectifier Circuit is controllable or uncontrollable. Few components of the circuits which can determine it are Diodes, Thyristors, etc.
Fig. 3 – Single Phase and Three Phase Bridge Rectifier Circuit
2. Uncontrolled Bridge Rectifiers
This is a Bridge Rectifier that is dominantly used to rectify the input. It uses the Diodes to rectify the input. The Diode is undeniably a unidirectional device and hence, it only allows current from one direction. The configuration of the diodes in this rectifier is such that, the power is not allowed to vary with the change in load requirements. Hence, due to this feature, the Uncontrollable Bridge Rectifiers are always used in the stable or constant power supplies.
3. Controlled Bridge Rectifiers
This is a type of Rectifier where the uncontrollable diodes are not used as the components of the device rather; controlled solid-state devices like those of MOSFET’s, SCR’s (Silicon Controlled Rectifier or simply Thyristors), IGBT’s etc. are put to use. Hence, the power output achieved with the help of this rectifier differs at various voltages. This feature of the Controllable Bridge Rectifiers has made them useful in many sectors.
Fig. 4 – Controlled and Uncontrolled Bridge Rectifier Circuit
It is possible to change the output load power appropriately. When various instants of the devices are triggered, there is a change in the output power. This is a major category of the Bridge Rectifier which has got all its features just due to alterations of the components.
How does Bridge Rectifier Work
A Single- Phase Rectifier has four Diodes D1, D2, D3, D4 and the connection is made across the load RL as shown in the Fig. 5. The four Diodes are connected in such a way that just two diodes conduct power during each half cycle. The load current is the same and the AC current which is the input is changed into DC with the help of this circuit.
The output received, is found to be pulsating and just to retain the purity of the DC current, there is a requirement of a capacitor. The working principle of almost all the rectifiers is the same but in the case of Controllable Bridge Rectifiers, the Thyristors are responsible for triggering; so that current is driven to the load.
Fig. 5 – Construction of Bridge Rectifier
AC signal is applied to the circuit. During positive half cycle, Diodes D1,D3 become forward biased while D2,D4 become reverse biased. It also shows that terminal A becomes positive and terminal B becomes negative. Similarly terminal B becomes positive and terminal A becomes negative during the negative half cycle. In this case, diodes D2,D4 get forward biased and diodes D1,D3 get reverse biased. The Load Current remains the same during both the positive and negative half cycles.
Fig. 6 – Input and Output Waveforms
Characteristics of Bridge Rectifier
The primary characteristics include:
- Ripple Factor
Ripple Factor is the measure of the smoothness of the output DC signal. The output DC signal with fewer ripples is known as a smooth DC signal while the output with large ripples is known as a top pulsating DC signal.
Efficiency of the rectifier is represented as the ratio between the output of the DC power to the applied AC as the input power.
Applications of Bridge Rectifiers
The applications include:
- They are used in the modulation of radio signals.
- Widely used to convert AC voltage into the low DC value.
- They are also used in electric Welding.
- Mainly used in Power supply units.
Advantages of Bridge Rectifiers
The advantages include:
- The efficiency of the Bridge Rectifier is surely a pro. It has an efficiency more than that of the half-wave rectifier and is equal to the full-wave rectifiers. The output signal of DC is found to be smoother comparatively, to that of the half-wave rectifier.
- There is no requirement of a step down transformer.
- The waveform output is continuous.
- A low filter is required to use it in a vehicle.
Disadvantages of Bridge Rectifiers
The disadvantage of the Bridge Rectifier can be the complex structure of it. Above all, another point that can be included in the disadvantage is the power loss caused when more number of diodes are used.
- If more diodes are used, then there can be a huge ascent in the cost of making.
- There can be error in the rectification, if the value of the Diode is not kept precise.
- Proper DC output cannot be found.