Operation of SCR
Figure shows the schematic diagram of SCR. It consists of four layers(i.e., p, n, p and n) three terminals A(Anode), K(Cathode) and G(Gate) and three junction J1 , J2 , and J3.
The anode and cathode terminals are connected to the main power circuit wherever, the gate terminal is connected to the control circuit. Whenever the P layer near the anode is made more positive compared to N layer near the cathode, Junctions J1 and J3 get forward biased. Whereas, the middle junction J2 gets reverse biased. Junction J2 is known as a junction capacitance as it acts as a capacitor in this mode. Due to the depletion layer formed at this junction, no current flows through the device, but due to the drift of mobile charge carriers, a small amount of leakage current flows through the circuit.
As the leakage current is negligible small, the device does not conducts. This state is know as forward blocking state or OFF state of the device, as it blocks the forward biased voltage.
Whenever the N layer near the cathode is more positive compared to P layer near the anode, junctions J1 and J3 are in reverse biased and middle junction J2 get forward biased. As the junctions J1 and J3 are in reverse biased condition, they do not allow any amount of current to flow through the device. This state is know as reverse blocking state or OFF state.
By increasing the voltage across the anode and cathode, the width of the depletion layer at the junction J2 may be reduced. At some particular voltage, J2 disappears this is due to the breakdown of the junctions by large voltage gradient also called as avalanche breakdown. As junctions J1 and J3 are already in the forward biased condition, there exists a free carrier movement from anode to cathode. As a result, the device starts conducting and hence it is said to be in the conducting state or ON state.
Silicon Controlled Rectifier
The SCR or thyristor is one type of semiconductor device and using in high-power switching applications is exceptionally planned. The working of this device should be possible in a switching mode only and acts as a switch. When the SCR is triggered by its gate terminal into the transmission, then it will supply the current constantly. While planning a SCR or Thyristor circuit, exceptional focus ought to be expected for enacting the circuit. This article examines various techniques for SCR setting off or SCR turn ON strategies or setting off of Thyristors. There are different setting off strategies are accessible in light of different substances which incorporate temperature, voltage, and so on.
Table of Content
- Silicon Controlled Rectifier
- Key Terminologies
- Construction
- Operation
- Modes of Operation
- Types
- Advantages of SCR