Thyristors - definition
Thyristors - definition
[Thyristors is a semiconductor power element with a four-layer PNPN type structure, mainly used as an electronic switch in alternating current (AC)](/mx/en/news/library-articles/page/62146/) and direct current (DC) circuits. It is characterised by its ability to conduct large currents when conduction is initiated by a control signal applied to the gate, while maintaining high resistance to blocking voltages in the off state. The mechanism of operation of the thyristor is based on the phenomenon of avalanche breakdown of the junction under appropriate polarisation conditions and on the positive feedback between the two internal transistors (NPN and PNP) that make up its structure.
When the pulse is applied to the gate electrode, the Thyristors switches from the blocking state to the conducting state and remains in this state even after the pulse disappears, until the anode current drops below a certain threshold value called the holding current. In AC applications, Thyristors switching is usually performed when the current passes naturally through zero, while in DC systems additional forcing of the switching process is required.
Thyristors are widely used in power control systems, controlled rectifiers, voltage regulation systems, frequency converters and overvoltage protection. Their ability to operate at high voltages and currents, as well as their low conduction losses, make them indispensable in power generation, electric actuators and industrial Automation systems. Developments in technology have also led to the development of specialised variations of Thyristors, such as Triacs, GTOs (Gate Turn-Off Thyristors) or IGCTs (Integrated Gate-Commutated Thyristors), enabling more advanced control of the conduction and turn-off states in demanding applications.
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