Name: Energy Band Gap
Uploaded: 2019-07-19
Duration: 5 min 21 s
Description: We know that certain materials conduct electricity whereas some don’t. Has it got anything to do with their energy bandgap? Let’s find out in this video.

Question

What is rectifier? Name different kinds of rectifier. Describe the

pn

Junction diode as a half-wave rectifier.

Accepted Answer

A rectifier is an electronic device that converts an alternating current into a direct current by using one or more P-N junction diodes. A diode behaves as a one-way valve that allows current to flow in a single direction. This process is known as rectification.

A rectifier can take the shape of several physical forms such as solid-state diodes, vacuum tube diodes, mercury-arc valves, silicon-controlled rectifiers, and various other silicon-based semiconductors switches.

Different Types of Rectifier

Rectifiers are mainly classified into two types as:

Uncontrolled Rectifier

Controlled Rectifier

Uncontrolled Rectifiers

The type of rectifier whose voltage cannot be controlled is known as an uncontrolled rectifier. Uncontrolled rectifiers are further divided as follows:

Half Wave Rectifier

Full Wave Rectifier

The type of rectifier that converts only the half cycle of the alternating current into the direct current is known as a half-wave rectifier. Likewise, a full-wave rectifier converts both positive and negative half cycles of the AC. An example of this is a bridge rectifier. A bridge rectifier uses 4 diodes that are connected in the form of a Wheatstone bridge.

Controlled Rectifiers

A type of rectifier whose voltage can be varied is known as the controlled rectifier. We use SCRs, MOSFETs and IGBTs to make an uncontrolled rectifier a controlled one. These rectifiers are preferred over their uncontrolled counterparts. There are two types of controlled rectifiers, and they are Half Wave Controlled Rectifier and Full Wave Controlled Rectifier. Half-wave controlled rectifier has the same design as the half-wave uncontrolled rectifier except we replace the diode with an SCR.

Basically, a rectifier is a device which converts an alternating current into a direct current. A half-wave rectifier consists of a transformer, a diode and a load resistor. The primary coil of the transformer is connected to the ac mains, and the secondary coil to a load resistor $R_{L}$ through the diode D as shown below in figure: -

The waveforms of input and the corresponding output voltages are as shown below:-

During the positive half-cycle of the input voltage sine wave, the p-n junction diode is forward-biased and hence it conducts through $R_{L}$ . The current flowing in the circuit produces a voltage across the load which has the same shape as the positive half-cycle of the input voltage $V_{i}$ . During the next half-cycle of the sine wave, the p-n junction diode is reverse-biased. Hence, during this time, no current flows in the circuit and no voltage develops across $R_{L}$ . Since only the positive half-cycle of the input appears across the load, the input ac voltage is converted into a pulsating dc voltage. This process is repeated. This process is called Half-Wave Rectification.

What is rectifier? Name different kinds of rectifier. Describe the $pn$ Junction diode as a half-wave rectifier.

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