Bridge Rectifier

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What is Bridge Rectifier? 

The bridge rectifier is said to be widely used circuits among many electronic circuits. Bridge rectifiers are widely used for supplying power to various electronic basic components. 

The purpose of the bridge rectifier is to convert the AC power into the DC power. It is the most resourceful rectifier circuit from others. The power conversion in this device is very efficient. We call it a bridge rectifier as it makes a bridge-like circuit by including 4-diodes.

To improve the output of the bridge rectifier, a filter is also used inside the circuit. Let’s learn about the bridge rectifier in brief, especially about bridge rectifier working, it’s efficiency, and so forth.

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Bridge Rectifier Circuit

The bridge rectifier includes four diodes, such as D1, D2, D3, D4. It also includes a load resistor RL. For making its performance more efficient, these four diodes are linked in a closed-loop configuration. 

Then, it manages to convert the AC (alternating current) into DC (direct current). The non-existence of the exclusive centered-tapped transformers make the configuration of this device more relevant. It helps to reduce the cost and size of the device.

The diagram given below shows the circuit diagram of the bridge rectifier:

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Point-A and Point-B are the terminals where the input signal is applied. Point-C and Point-D are the output terminals that produce DC signals across the load resistor RL. The arrangement of four diodes is made in a unique fashion. That is why only two diodes conduct electricity throughout every half cycle.

The diodes that pair to conduct electricity through the positive half cycle are D1 and D3. Similarly, the diode pairs D2 and D4 conduct electricity during the negative half cycle.


Bridge Wave Rectifier

The following figure shows the current flow during the positive half-cycle:

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The following figure shows the current flow during the negative half cycle:

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Now, We will discuss how a Bridge Rectifier works:

If you supply the power (AC) across the bridge rectifier, the terminal–A turns into positive, and the terminal–B turns into negative during the positive half cycle. At this point, the diodes D1 and D3 get changed into forward biased, whereas D2 and D4 turn into reverse biased.

The terminal-A becomes positive, and the terminal–B becomes negative during the negative half-cycle. At this point, the diodes D1 and D3 change into reverse-biased, whereas D2 and D4 turn into forward-biased.

The above figures show that the flow of current across the load resistor RL remains the same during the positive half-cycles, and the negative half-cycles. The polarity of the output DC signal may vary completely. The output may be negative or positive completely. 


Bridge Rectifier Waveform

We acquire a complete negative DC voltage when the diodes’ direction is reversed. That is why electric current can pass through a bridge rectifier during both negative and positive half-cycles of the AC input signal.

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Ripple Factor of Bridge Rectifier

The ripple factor is a feature associated with the bridge rectifier that measures the smoothness of the output DC signal. We can say the output DC signal is a smooth output when it comes to less number of ripples. The high pulsating DC signal is measured as the high ripples.

The expression for the ripple factor is explained as the ratio of ripple voltage to the pure DC voltage.

Mathematically,

ℽ = \[\sqrt{\frac{V_{rms}^{2}}{V_{DC}}-1}\]

Vrms = Root Mean Square Voltage

VDC = Average Voltage of DC Supply


Efficiency of Bridge Rectifier

The measurement of the efficiency of the bridge rectifier shows the optimum performance of the rectifier. The definition for the rectifier efficiency is the ratio of the DC output power to the AC input power.

ɳ = (DC Output Power /AC Output Power)

Note: A bridge rectifier has a maximum efficiency of 81.2%.


Advantages of Bridge Rectifier

Here are some advantages of bridge rectifier:

  1. A bridge rectifier has a higher efficiency than a half-wave rectifier. But in some cases, the efficiency of the center-tapped full-wave rectifier and the bridge rectifier is the same.

  2. A smooth output is obtained from a bridge rectifier than the half-wave rectifier. 

  3. The bridge rectifier allows both positive and negative half cycles of the input AC signal for processing. This feature is not found in the half-wave rectifier, and processes only half of the AC signal, blocking the other.


Peak Inverse Voltage of a Bridge Rectifier

A peak inverse voltage is a maximum voltage that a diode can endure in the reverse bias condition. The diodes D1 and D3 are in the conducting state in the positive half, and the diodes D2 and D4 are in the non-conducting state.

However, in the negative half, the diodes D2 and D4 are in the conducting state, and the diodes D1 and D3 are in the conducting state.

FAQ (Frequently Asked Questions)

1. Describe the purpose of the Zener diode.

We use Zener diodes for regulating the voltage. 

For example, it is used in surge suppressors, and switching applications and clipper circuits as reference elements. This diode is functional by dropping the excess voltage during the conduction. It uses a series resistor to do so.

2. How is a half-wave rectifier used in circuits?

The half-wave rectifier is known for allowing the only half-cycle of an AC voltage waveform to pass by, blocking the other half. It is used to create a flow of current through the circuit by the demodulation of the amplitude modulated signal.

3. Mention some points on the disadvantages of bridge rectifiers

Here are some points regarding the disadvantages of bridge rectifier:

  • The bridge rectifier has a complex circuit arrangement as compared to the half-wave rectifier, and center-tapped full-wave rectifier.

  • It uses four diodes to convert the AC current to DC, whereas the center-tapped full-wave rectifiers use only two diodes.

  • There is more power loss when diodes are used multiple times.

  • A higher voltage drop is sensed in the bridge rectifiers.

4. Calculate the efficiency of a bridge rectifier, connected to an AC source supplying 100 watts, with a total DC output of 24 Watts.

We know that the formula for the efficiency of a bridge rectifier is:

ɳ = (DC Output Power /AC Output Power)

η = 50/100 = 0.5 = 50%