# Difference between Half Wave and Full Wave Rectifier

A rectifier is an electronic circuit that converts the alternating current (AC) into direct current (DC). The process of conversion of alternating current into direct current is known as rectification. The rectifier consists of semiconductor diodes to perform the rectification.

Depending upon the type of conversion of AC into DC, i.e., half cycle of AC into DC or full cycle of AC into DC, the rectifiers are classified into two categories viz. −

• Half Wave Rectifier
• Full Wave Rectifier

In this article, we will discuss about the differences between half-wave rectifier and full-wave rectifier. Also, we will briefly discuss about the half-wave rectifier and full wave rectifier so that the understanding of differences between them becomes easier.

## What is a Half Wave Rectifier?

A half wave rectifier is the rectifier circuit which converts only half cycle of the alternating current into direct current. The circuit of a typical half-wave rectifier consists of a semiconductor diode, the circuit of half-wave rectifier and the output waveform are shown in Figure-1.

The alternating current is stepped-up or stepped-down to the desired voltage using a transformer and then the transformed AC is fed to the diode. The rectification process of the half wave rectifier can be understood as follows −

During positive half cycle of AC, the diode being forward biased acts as a short circuit and allows the electric current to pass through it. While, during the negative half cycle of AC, the diode gets reverse biased and acts as an open circuit and hence do not conduct. In this way, the electric supply (voltage) at the load terminals will appear only for the positive half cycle of AC. And, during the negative half cycle, there is no voltage across the load terminals. Thus, the alternating current is converted into direct current, which flows only in one direction, but only half cycle of AC.

## What is a Full Wave Rectifier?

A full wave rectifier is the one which converts the complete cycle of alternating current into direct current. The full-wave rectifier circuit consists of a center-tapped type step-down transformer and two semiconductor diodes. The anode terminals of the diodes are connected to the secondary winding terminals of the transformer and the cathode terminals of the diodes are connected to a common point. The load resistor is connected between the common terminal and the center-tapping point of the transformer.

During the positive half cycle of AC, the diode D1 is forward biased and diode D2 is reverse biased. Hence, for the positive half cycle, the diode D1 conducts and current flows through the diode D1 and the load resistor RL. Now, during the negative half cycle of AC, the diode D1 is reverse biased and diode D2 is forward biased, thus only diode D2 conducts for the negative half cycle of AC and the current will flow through the diode D2 and the load resistor RL. The circuit of the full wave rectifier and the output voltage waveform are shown in Figure-2. In this way, a full wave rectifier converts the complete cycle of AC into DC.

Based on circuit configuration, the full-wave rectifier is further classified into two types viz. center-tapped FWR and bridge type FWR.

## Difference between Half Wave Rectifier and Full Wave Rectifier

The major differences between half-wave rectifier and full-wave rectifier are given in the following table −

ParameterHalf Wave Rectifier (HWR)Full Wave Rectifier (FWR)
DefinitionAn electronic circuit which converts half cycle of alternating current into direct current is known as half-wave rectifier.An electronic circuit that converts the complete cycle of alternating current into direct current is known as full-wave rectifier.
TypesNo further classification.The full-wave rectifier is of two types: center-tapped FWR and bridge FWR.
Number of diodes requiredHalf wave rectifier requires only one diode.The number of diodes required in a full-wave rectifier are as −
• Center-tapped FWR requires two diodes.
• Bridge FWR requires 4 diodes.
Rectified cycles of ACIn half wave rectifier, only half cycle of AC (either positive or negative) being rectified.Full wave rectifier rectifies the both positive and negative cycles of AC.
Electric current through loadThe electric current through the load is not continuous.A continuous electric current flows through the load.
Peak inverse voltage (PIV)The peak inverse voltage for the half wave rectifier is equal to the maximum value of the input voltage, i.e., Vm.For the full wave rectifier, the peak inverse voltage is equal to the double of the maximum value of input voltage, i.e., 2Vm.
Output frequencyFor half wave rectifier, the frequency of ripple output is equal to the input supply frequency, i.e., "f".The output frequency for the full-wave rectifier is double of the supply frequency, i.e., "2f".
Maximum efficiency of rectification (for sinusoidal AC)For half wave rectifier, the maximum efficiency of rectification is 40.6%.The maximum efficiency of rectification for a full-wave rectifier is equal to 81.2%.
Ripple factor (for sinusoidal AC)The ripple factor for half-wave rectifier is 1.21.The ripple factor for full-wave rectifier is 0.482.
Form factor (for sinusoidal AC)The form factor of half-wave rectifier is 1.57.The form factor of a full-wave rectifier is 1.11
Peak factor (for sinusoidal AC)For half-wave rectifier, the peak factor is equal to 2.The peak factor of a full-wave rectifier is 1.414.
Transformer utilization factorThe transformer utilization factor of a half-wave rectifier is 0.2865.The transformer utilization factor of a full-wave rectifier is 0.692 (centre-tapped rectifier) and 0.8106 (bridge rectifier).
Average output currentThe average output DC of a half-wave rectifier is,
$$l_{av}\:=\:\frac{l_{m}}{\pi}$$
The average output DC of a full-wave rectifier is,
$$l_{av}\:=\:\frac{2l_{m}}{\pi}$$
Voltage regulationThe half-wave rectifier has good voltage regulation.The voltage regulation of a full-wave rectifier is better than that of half-wave rectifier.
Saturation of transformer coreIn case of half-wave rectifier circuit, the DC saturation of the transformer core is a common problem.A full-wave rectifier does not have DC saturation of the transformer core.
CostHalf wave rectifier is less costly as it requires only one diode.Full wave rectifier is costlier than half-wave rectifier as it requires more number of diodes.

## Conclusion

In this article, we have explained about the half wave and full wave rectifiers and the key differences between them. Both half-wave and full-wave rectifiers are crucial components in various electronic circuits as they convert AC into DC. However, the most significant difference between the two is that a half-wave rectifier converts only half cycle of AC into DC, whereas a full-wave rectifier converts the complete cycle of AC into DC.

Updated on: 31-Oct-2023

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