Difference Between SCR, DIAC, TRIAC |Definition, Construction

Hello guys, welcome back to my blog. In this article, I will discuss the difference between SCR, DIAC, TRIAC, construction, definition, applications of SCR, DIAC, and TRIAC, etc.

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Difference Between SCR, DIAC, TRIAC

SCR ( Silicon controlled rectifier)

This is a uni-directional device which is made up of silicon. SCR can be also called us thyristor or thyroid transistor. SCR is having three terminal and 4 layers, a semiconductor device that consists of alternating layers of P & N-type materials.

Construction Of SCR

SCR is having three terminals and four layers as I mentioned above. The four layers are made up of P and N layers, Which are arranged alternately to form 3 junctions. The outer P and N layers will be doped heavily but middle P and N layers are doped lightly. The gate terminal is connected in the middle of the P-layer and the anode is connected from the outer P-layer and cathode is from the N-layer terminal.

Advantages Of SCR

It is small in size.
It doesn’t have moving parts and it is having higher efficiency.
It delivers noiseless operation.
High switching speed.
This can be operating at high voltage and high current.

Applications Of SCR

It can be used in power-switching circuits.
Used in 0 voltage switching circuits.
It is used in inverters.
It can be used in timing circuits, welding machine control, computer logic circuits, many more.
Used in battery charging regulator.
It is used in a controlled rectifier.

DIAC ( Diode for alternating current )

DIAC can be also called transistor without a base. DIAC is one of the types of the diode, switch conducts only after its break over voltage has reached. DIAC will be having two electrodes and this is the member of thyristor family, which will be used in triggering thyristors. In DIAC gate electrode is absent. It is a bi-directional device.

Construction Of DIAC

DIAC Is having two terminals and four layers. The construction of DIAC is similar to the transistor, but there is a slight difference. The base terminal is absent in DIAC and the three regions are having the same level of doping. It will give symmetrical switching characteristics to both polarities of voltages. It will be having 2 P-type material and 3 N-type materials and the gate terminal is absent in DIAC. DIAC can be triggered in both the polarity of voltages. The construction of DIAC is similar when two diodes are connected in anti-parallel.

Advantages Of DIAC

It can be switched on or off just by reducing the voltage level below its breakdown voltage.
Using DIAC as a triggering circuit is cheap.

Applications Of DIAC

It can be used in the TRIAC triggering circuit by connecting the gate terminal to the DIAC.
Used in lamp dimmer circuit.
This can be used in the heater control circuit.
Used in speed control of the universal motor.

TRIAC ( Triode for alternating current)

TRIAC is a 3 terminal AC switch. Unlike SCR, TRIAC can trigger in both directions. This device can be used in AC systems as a switch. TRIAC Is 3 terminal, 4 layers, and a bi-directional semiconductor device that controls AC power. The maximum rating of TRIAC is 16KW.

Construction Of TRIAC

In TRIAC, 2 SCRs will be connected in inverse with parallel combination, and gate terminal as common. The gate terminal will be connected to both N and P regions, due to this the gate signal will be applied that is irrespective of the polarity of the signal. In TRIAC we will not be having anode and cathode because it works in both polarities, which means TRIAC is bilateral. It contains three terminals, main terminal 1, main terminal 2, gate terminal G.

Advantages Of TRIAC

It can operate with the positive and negative polarity of great pulses.
TRIAC needs a single fuse to protect.
It needs only a single heat sink of larger size but SCR requires two heat sink.
A safe breakdown in both directions is possible.

Disadvantages Of TRIAC

These are not much reliable.
These are having low ratings compared to SCR.
You need to be careful while triggering this circuit because it can operate in either direction.

Applications Of TRIAC

This can be used in the control circuit
Used in controlling fans.
It can be used in AC phase control.
Used in high power lamp switching.
It is used in AC power control.

Difference Between SCR, DIAC, TRIAC

SCR (Silicon controlled rectifier)

SCR stands for silicon controlled rectifier.
It is having three terminals.
It is a unidirectional device that is only conducted in forwarding bias.
It is a controlled device since it is having a gate terminal.
The power handling capacity of this is high.
The firing angle of SCR is 0 to 180°.
Used in inverters, choppers, rectifiers, 3 phase systems.

DIAC (Diode for alternating current)

DIAC stands for Diode for alternating current.
It is having two terminals.
This is a bi-directional device.
It is an uncontrolled device.
The power handling capacity of DIAC is low.
There will be no firing angle for DIAC.
Used to trigger TRIAC.

TRIAC ( Triode for alternating current)

Stands for Triode for alternating current.
It is having three terminals
It is a bi-directional device
This is a controlled device
The power handling capacity of TRIAC high.
The firing angle of TRIAC is 0 to 180° and 180° to 360°.
Used in fan control, light dimmer, and many more.

I hope this article may help you all a lot. Thank you for reading. If you have any doubts related to this article “difference between SCR, DIAC, TRIAC”, then comment below.

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