Half wave Rectifier

Working of Half Wave Rectifier
In this section, let us understand how a half-wave rectifier transforms AC into DC.

A high AC voltage is applied to the primary side of the step-down transformer. The obtained secondary low voltage is applied to the diode.
The diode is forward biased during the positive half cycle of the AC voltage and reverse biased during the negative half cycle.
The final output voltage waveform is as shown in the figure below:
Half Wave Rectification

For better understanding, let us simplify the half-wave circuit by replacing the secondary transformer coils with a voltage source as shown below:

Half Wave Rectifier Circuit with Voltage Source

For the positive half cycle of the AC source voltage, the circuit effectively becomes as shown below in the diagram:

Halfwave circuit during the positive half cycle of the AC source voltage

When the diode is forward biased, it acts as a closed switch. But, during the negative half cycle of the AC source voltage, the equivalent circuit becomes as shown in the figure below

Halfwave circuit during the negative half cycle of the AC source voltage

When a diode is reverse biased, it acts as an open switch. Since no current can flow to the load, the output voltage is equal to zero.

Half Wave Rectifier Waveform
The halfwave rectifier waveform before and after rectification is shown below in the figure.

Halfwave Rectifier Waveform

Half Wave Rectifier Capacitor Filter
The output waveform of a halfwave rectifier is a pulsating DC waveform. Filters in halfwave rectifiers are used to transform the pulsating waveform into constant DC waveforms. A capacitor or an inductor can be used as a filter.

The circuit diagram below shows how a capacitive filter is used with halfwave rectifier to smoothen out a pulsating DC waveform into a constant DC waveform.

Halfwave Rectifier Rectification

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Ripple Factor of Half Wave Rectifier
Ripple factor determines how well a halfwave rectifier can convert AC voltage to DC voltage.

Ripple factor can be quantified using the following formula:

The ripple factor of a halfwave rectifier is 1.21.

Efficiency of Halfwave Rectifier
The efficiency of a halfwave rectifier is the ratio of output DC power to the input AC power.

The efficiency formula for halfwave rectifier is given as follows;

RMS value of Half Wave Rectifier
The RMS value of the load current for a half-wave rectifier is given by the formula:

Form factor of a Halfwave Rectifier
The form factor is the ratio between RMS value and average value and is given by the formula:

Applications of Half Wave Rectifier
Here are a few common applications of half wave rectifiers:

They are used for signal demodulation purpose
They are used for rectification applications
They are used for signal peak applications
Disadvantages of Half Wave Rectifier
Power loss
Low output voltage
The output contains a lot of ripples