What is Thyristor

In today’s tutorial, we will have a look at What is Thyristor. The thyristor is a semiconductor component that has 4 layers of N and P materials

Posted at: 17 - Nov - 2019

Category: Tutorials

Author: williamjones

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Hello friends, I hope you all are doing great. In today’s tutorial, we will have a look at What is Thyristor. The thyristor is a semiconductor component that has 4 layers of N and P materials with the sequence P, N, P, N. First thyristor was invented in 1950 by William Shockley who was a physicist and belonged to the United States of America. But first time it was practically used in 1956 due to its huge amount of current and voltage handling capability. Due to this feature, it was commonly used in different power control circuitry, fan dimmers, and speed control of different motors. There are 2 types of design in which this module available and both used according to circuit requirements first one has two leads and the second one has three leads in its structure. This electronic component is mostly used in switching circuitry, oscillators, level detection circuits, etc. This module is not similar to the transistor as a transistor can operate among on and off conditions but thyristor operates only single state either on or off. In today's post, we will have a look at its working, structure, pinout, applications and some related parameter. So let's get started with What is Thyristor.

What is Thyristor

A thyristor is also known as SCR (silicon controlled rectifiers) used in different switching circuits like a transistor and in power controlling circuitry.
The physical structure of this semiconductor is different than the other semiconductors materials like transistor that has three layers but in thyristor 4 layers of different elements are constructed.

In a normal transistor, there are 3 P, N, P or N, P, N layer exists but in while in thyristor four-layer like P, N, P, N exists.
Its 'P' end is known as anode and 'N' end is known as the cathode. As in normal transistor base control terminal in this device, the control terminal is known as a gate that is adjacent to the cathode.
This module can be created with the different semiconductor materials but normal it is manufactured with the silicon.
As the silicone has the ability to handle larger amperes current and voltage easily as well it has ability to bear high temperature so it mostly preferred for thyristor construction.
with these features, its price and construction are simple so it prefered for thyristor and some other electronic devices.

Working of Thyristor

The working of this module is different than other semiconductors device, to the understanding of working of this device we draw the equivalent circuit.
In the given figure you can see that two transistors are linked with one another the first transistor is NPN that is behaving like the anode and the second transistor is PNP that is behaving like the cathode.
If we provide input supply to at the terminals of thyristor there will be no current passes as the both of transistor ane unbiased state.
If we connect input supply at the gate then current will passes through the base that will operate the TR2 transistor.
When TR2 starts its operation than the base of the first transistor get force from this transistor and start its operation it causes to put TR2 in working state either we separated the input supply.

Features of Thyristor

These are some features of thyristor that are described here with detailed.

	Specifications	Parameters
dI/dt	Extreme increment of on-state current	It is an extreme value of current for on condition if it surpasses then our device will be damaged.
I_GM	Maximum Gate Current	It is the extreme value at the gate that it can bear.
I_GT	Triggering current of the gate	It is the triggering value of current at the gate that also starts to current flow through anode and cathode terminals of component.
I²t	Overcurrent protection	The I²t parameter tells about the value of fuse used for this module.
I_T(AV)	On condition average current	This parameter of thyristor explains about the average value of current passing through the module.

Types of Thyristor

There are numerous types of thyristor according to their use and structure.

RCT:

One important feature of thyristor is that it stops current to flow in reverse direction so if we add and diode then current starts to flow in the opposite direction. This type of arrangement is known as RCT or reverse conducting thyristor.
During reverse operation both thyristor and diode not operate at the same time but they take some time for the operation that provides protection from overheating.
This type of thyristor used in inverter circuits and frequency regulators.

GATT:

This types of thyristor are used in such applications where fast switching needs. For this process in certain cases, negative polarity voltage also provided to the gate.
To control the voltage at cathode and anode terminals negative voltage at the gate control the minorities carriers.
The physical construction of thyristor is like to normal thyristor but the difference is that the area of cathode that enhances the controlling capability of the gate.

GTO:

It is also known switch for a gate of thyristor. This types of thyristor are not normally used in circuits because they not operate at reverse voltage.

Asymmetric Thyristor:

In such circuits where there is no use reverse voltage and no need of rectifier circuit this type of thyristor is used. These are normally used in switching circuits.

Applications of Thyristor

The thyristor is normally used in different electronic circuits and devices, its some practical uses are explained here with the detailed.
It used in different electrical devices for the controlling of alternating current at the input such as motor, light etc.
It used in different circuits as a switch.
In a different circuit, it used to control the overvoltage.
It used in different controllers as a trigger.
It also used in camera for flashing of a photograph.

It is the detailed tutorial on thyristor in this post I have mentioned each and everything related to the thyristor. If you still have any question about it ask in comments. Thanks for reading.