Silicon controlled switch (SCS), like the SCR, is a unilateral, four layer three junction P-N-P-N silicon device with four electrodes namely cathode C, cathode gate Gx, anode gate…
As mentioned earlier, low-current drop out is the normal way in which the SCR is turned off. Gate-controlled switch is designed for easy opening with a reverse-biased trigger.…
The diacs, because of their symmetrical bidirectional switching characteristics, are widely used as triggering devices in triac phase control circuits employed for lamp dimmer, heat control, universal motor…
Introduction to Diac-Operation and Construction A diac is an important member of the thyristor family and is usually employed for triggering triacs. A diac is a two-electrode bidirectional…
The ability of an SCR to control large currents to a load by means of small gate current makes the device very useful in switching and control applications.…
How to make a full wave rectifier using SCR ? For full-wave rectification two SCRs are connected across the centre taped secondary, as shown in figure-a. The gates…
How SCR functions as a Half Wave Rectifier ? SCRs are very useful in ac circuits where they may serve as rectifiers whose output current can be controlled…
How an SCR functions as a switch ? We have seen that SCR operates either in on-state or in off-state and no other state in between, that is…
90° Phase Control of SCR. In ac circuits, the SCR can be turned on by the gate at any angle a with respect to the applied voltage. This angle…
How to protect an SCR using protection circuits ? SCRs are sensitive to high voltage, over-current, and any form of transients. For satisfactory and reliable operation they are…
How to make series and parallel connections of an SCR ? In many power control applications the required voltage and current ratings exceed the voltage and current that…
Current ratings of an SCR The current carrying capability of an SCR is solely determined by the junction temperature. Except in case of surge currents, in no other…
SCR Voltage Ratings (i) Breakover Voltage. The minimum forward voltage, when the gate is open, at which SCR starts conducting heavily (that is turned-on) is called the breakover…
SCR-Ratings and Specifications The performance of an SCR is affected by the junction temperature, because of change in carrier densities in the four layers and the junction temperature…
Turning-off Methods of an SCR As already mentioned in previous blog post, once the SCR is fired, it remains on even when triggering pulse is removed. This ability…
How to turn ON an SCR ? As mentioned earlier, the SCR can be switched on either by increasing the forward voltage beyond forward break over voltage VFB0…
Turn-on and turn-off characteristics of an SCR are called the dynamic characteristics of the SCR. (a) Turn-On Characteristic. The turn-on time characteristic shows the variation of current and voltage…
As already mentioned, the SCR is a four-layer device with three terminals, namely, the anode, the cathode and the gate. When the anode is made positive with respect…
How an SCR works?-Principle of Operation SCR Working Principle The SCR is a four-layer, three-junction and a three-terminal device and is shown in fig.a. The end P-region is…
Introduction to SCR-Silicon Controlled Rectifier As the terminology indicates, the SCR is a controlled rectifier constructed of a silicon semiconductor material with a third terminal for control purposes.…
Comparison of Thyristor and Transistor As already mentioned, transistors and thyristors are both semiconductor devices. They are now widely employed in switching operations because of their numerous advantages…
Comparison between Thyristors and Thyratrons Before the discovery of thyristors, thyratrons were used for industrial control, but now they have been replaced by the thyristors because of the…
Thyristor Family-Types of Thyristors The P-N-P-N devices with zero, one or two gates constitute the basic thyristor. But today the thyristor family includes other similar multilayer devices also.…