Thyristors are a very popular type of semiconductor devices. They share common characteristics with other solid-state devices made of silicone, such as diodes and transistors. So it may be difficult to differentiate between thyristors and transistors. Various forms of thyristors are available in the market. 

Types of Thyristor

 Silicon controlled rectifier (SCR)

A silicon-controlled rectifier (SCR) is the most significant component of the thyristor band. It is a four-layer solid-state current-controlling device and sometimes a phase-controlled thyristor also referred to as SCR. The SCR has widely used thyristor in the devices for the control of high power on and off. 

Triode for alternating current (TRIAC)

The second most frequently used thyristor after SCRs is TRIACS. They will have an influence on both sides of the alternating waveform by allowing more effective use of available power. They are typically used only for low-power applications because of their intrinsic non-symmetric nature. 

Diode for alternating current (DIAC)

DIACS are low-power devices that are primarily used in combination with TRIACS (assembled in a sequence with the TRIAC gate terminal). They are mostly found in light bulb dimmers.

Light-activated silicon-controlled rectifier (LASCR)

LASCR is also called as light-triggered thyristors (LTT). The LASCR assures full electrical isolation between the light source and the switching system of the power converter. Their use is mostly found in HVDC transmission equipment, reactive power compensators and high-power pulse generators.