Silicon Controlled Rectifier | Industrial Electronics | SNS Institutions

#snsinstitutions #snsdesignthinkers #designthinking Silicon Controlled Rectifier (SCR) Introduction A Silicon Controlled Rectifier (SCR) is a four-layer, three-junction semiconductor device belonging to the thyristor family. It is widely used in industrial electronics for controlling high power and high voltage applications. Unlike an ordinary diode, which conducts whenever it is forward biased, an SCR conducts only when it receives a triggering signal at its gate terminal while it is forward biased. Once turned ON, it continues to conduct even if the gate signal is removed, provided the current through the SCR remains above a minimum value called the holding current. SCRs are known for their high efficiency, fast switching capability, low power loss, and ability to handle large currents and voltages. They are commonly used in controlled rectifiers, motor speed controllers, battery chargers, light dimmers, heating systems, and industrial power control circuits. Definition A Silicon Controlled Rectifier (SCR) is a unidirectional, four-layer (PNPN), three-terminal semiconductor switching device that conducts current only after receiving a gate triggering pulse and continues conducting until the anode current falls below the holding current. Construction An SCR consists of four alternate semiconductor layers: P₁ – N₁ – P₂ – N₂ This creates three PN junctions: Junction J₁ Junction J₂ Junction J₃ It has three terminals: Anode (A): Connected to the outer P-layer Cathode (K): Connected to the outer N-layer Gate (G): Connected to the inner P-layer