Introduction to Thyristor

Introduction to Thyristor

• In various modem electronic applications such as variable speed drives, temperature control, light and illumination control, motor current control etc., some special type of control devices are used. Such devices are called power switching and control devices. A thyristor is a base of such control devices. A thyristor is a semiconductor device whose switching action depends on internal regenerative feedback. Unlike BJTs and FETs, a thyristor can be operated only as a switch. A thyristor can be two terminal, three terminal or four terminal, unidirectional or bidirectional device.

• The main applications of these devices are the control of large load current for motors, heaters, lighting systems and other similar devices.

• There is big family of thyristors. Some of the commonly used members of the thyristor family are,

1. Silicon Controlled Rectifier (SCR)

2. Gate turn-off thyristor (GTO)

3. Diac

4. Triac

5. Insulated Gate Bipolar Transistor (IGBT)

6. Power MOSFET

• Thyristors mainly lack in switching speeds compared to the power transistors. But their power handling capabilities are very high. The drive requirements of thyristors are also simple compared to power transistors. Silicon Controlled Rectifier (SCR) is most commonly used thyristor.