Unidirectional thyristor (SCR) and bidirectional thyristor (TriaC) are two common electronic components commonly used in AC power control and power regulation applications. Although they are both controllable silicon devices, they have significant differences in structure, working principle, and characteristics.

Unidirectional thyristor is a type of thyristor device that operates unidirectionally, also known as single-phase thyristor. It is composed of four layers of semiconductor material, with a control electrode (called the gate electrode) used to control the conduction and turn off of the device. Single phase thyristors can only conduct at forward voltage, and if the voltage is reverse, the device will be in an off state. SCR is mainly used in the control and rectification circuits of DC power supplies.

Compared to unidirectional thyristors, bidirectional thyristors (TRIACs) are a type of thyristor device that operates bidirectionally. It consists of two interconnected SCR devices connected in reverse parallel, so it can operate at both forward and reverse voltages. TRIAC is commonly used in AC applications to control the brightness of electric lights, motor speed, and more.

(单向可控硅)




(Bidirectional thyristor)