Feb 142019
 

What is Half Wave Rectifier?

Half wave rectifier rectification process

The current and voltage, that the energy supplier companies deliver to our homes, offices, shops, etc., is alternating current (AC). But the electronic devices that we have on these places use direct current (DC) . Then, the alternating current (AC) should be converted to direct current (DC).

To make the rectification process, we use a rectifier circuit made of semiconductor diodes. An electric transformer is used to reduce the line voltage from 110/220 volts AC or other, to a lower voltage such as 24, 12, 9  or 15 volts AC.

The rectifier circuit is placed at the output of the transformer. The voltage at the transformer secondary winding is alternating, and it has positive and negative half cycles.

Forward Biased Diode

During each “positive” half cycle of the AC sine wave, the diode is forward biased, allowing current to flow through it. See the graph. If the diode is considered ideal, it behaves like a short circuit. Then all the transformer voltage  secondary winding goes directly to the load resistor.

Forward Biased Diode - The Half Wave Rectifier

Reverse Biased Diode

During each “negative” half cycle of the AC sinusoidal input waveform, the diode is reverse biased, the current supplied by the transformer secondary winding will attempt to flow in the opposite direction to the diode arrow (the diode is reverse biased). If the diode is considered ideal, it will behave as an open circuit and no current flows through the diode.

Diode Reverse Bias - The Half Wave Rectifier

The output waveform of a half wave rectifier is shown in the diagram below.

Half-wave Rectifier Output

Half wave rectifier output

As you can see only the positive part of the original wave is obtained in the output of the half wave rectifier.

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